Minor log fixes (#1983)

* Fix a bug in the case where syncer chain is fully known to syncee

* Extract chain negotiation to a separated method

* Bump version and update the changelog

* Add zoom-in progress validation and some debug logs

* Improved error explanation

* go fmt

* Validate zoom-in progress through a total count

CONTRIBUTING.md

@@ -12,8 +12,7 @@ If you want to make a big change it's better to discuss it first by opening an i
 
 ## Pull Request process
 
-Any pull request should be opened against the development branch of the target version. The development branch format is
-as follows: `vx.y.z-dev`, for example: `v0.8.5-dev`.
+Any pull request should be opened against the development branch `dev`.
 
 All pull requests should pass the checks written in `build_and_test.sh`, so it's recommended to run this script before
 submitting your PR.

README.md

@@ -1,16 +1,13 @@
 
 Kaspad
 ====
-Warning: This is pre-alpha software. There's no guarantee anything works.
-====
 
 [![ISC License](http://img.shields.io/badge/license-ISC-blue.svg)](https://choosealicense.com/licenses/isc/)
 [![GoDoc](https://img.shields.io/badge/godoc-reference-blue.svg)](http://godoc.org/github.com/kaspanet/kaspad)
 
 Kaspad is the reference full node Kaspa implementation written in Go (golang).
 
-This project is currently under active development and is in a pre-Alpha state.
-Some things still don't work and APIs are far from finalized. The code is provided for reference only.
+This project is currently under active development and is in Beta state.
 
 ## What is kaspa
 

app/app.go

@@ -87,6 +87,7 @@ func (app *kaspadApp) main(startedChan chan<- struct{}) error {
 	if app.cfg.Profile != "" {
 		profiling.Start(app.cfg.Profile, log)
 	}
+	profiling.TrackHeap(app.cfg.AppDir, log)
 
 	// Return now if an interrupt signal was triggered.
 	if signal.InterruptRequested(interrupt) {

app/appmessage/domainconverters.go

@@ -436,10 +436,10 @@ func RPCBlockToDomainBlock(block *RPCBlock) (*externalapi.DomainBlock, error) {
 
 // BlockWithTrustedDataToDomainBlockWithTrustedData converts *MsgBlockWithTrustedData to *externalapi.BlockWithTrustedData
 func BlockWithTrustedDataToDomainBlockWithTrustedData(block *MsgBlockWithTrustedData) *externalapi.BlockWithTrustedData {
-	daaWindow := make([]*externalapi.TrustedDataDataDAABlock, len(block.DAAWindow))
+	daaWindow := make([]*externalapi.TrustedDataDataDAAHeader, len(block.DAAWindow))
 	for i, daaBlock := range block.DAAWindow {
-		daaWindow[i] = &externalapi.TrustedDataDataDAABlock{
-			Block:        MsgBlockToDomainBlock(daaBlock.Block),
+		daaWindow[i] = &externalapi.TrustedDataDataDAAHeader{
+			Header:       BlockHeaderToDomainBlockHeader(&daaBlock.Block.Header),
 			GHOSTDAGData: ghostdagDataToDomainGHOSTDAGData(daaBlock.GHOSTDAGData),
 		}
 	}
@@ -454,12 +454,27 @@ func BlockWithTrustedDataToDomainBlockWithTrustedData(block *MsgBlockWithTrusted
 
 	return &externalapi.BlockWithTrustedData{
 		Block:        MsgBlockToDomainBlock(block.Block),
-		DAAScore:     block.DAAScore,
 		DAAWindow:    daaWindow,
 		GHOSTDAGData: ghostdagData,
 	}
 }
 
+// TrustedDataDataDAABlockV4ToTrustedDataDataDAAHeader converts *TrustedDataDAAHeader to *externalapi.TrustedDataDataDAAHeader
+func TrustedDataDataDAABlockV4ToTrustedDataDataDAAHeader(daaBlock *TrustedDataDAAHeader) *externalapi.TrustedDataDataDAAHeader {
+	return &externalapi.TrustedDataDataDAAHeader{
+		Header:       BlockHeaderToDomainBlockHeader(daaBlock.Header),
+		GHOSTDAGData: ghostdagDataToDomainGHOSTDAGData(daaBlock.GHOSTDAGData),
+	}
+}
+
+// GHOSTDAGHashPairToDomainGHOSTDAGHashPair converts *BlockGHOSTDAGDataHashPair to *externalapi.BlockGHOSTDAGDataHashPair
+func GHOSTDAGHashPairToDomainGHOSTDAGHashPair(datum *BlockGHOSTDAGDataHashPair) *externalapi.BlockGHOSTDAGDataHashPair {
+	return &externalapi.BlockGHOSTDAGDataHashPair{
+		Hash:         datum.Hash,
+		GHOSTDAGData: ghostdagDataToDomainGHOSTDAGData(datum.GHOSTDAGData),
+	}
+}
+
 func ghostdagDataToDomainGHOSTDAGData(data *BlockGHOSTDAGData) *externalapi.BlockGHOSTDAGData {
 	bluesAnticoneSizes := make(map[externalapi.DomainHash]externalapi.KType, len(data.BluesAnticoneSizes))
 	for _, pair := range data.BluesAnticoneSizes {
@@ -500,7 +515,9 @@ func DomainBlockWithTrustedDataToBlockWithTrustedData(block *externalapi.BlockWi
 	daaWindow := make([]*TrustedDataDataDAABlock, len(block.DAAWindow))
 	for i, daaBlock := range block.DAAWindow {
 		daaWindow[i] = &TrustedDataDataDAABlock{
-			Block:        DomainBlockToMsgBlock(daaBlock.Block),
+			Block: &MsgBlock{
+				Header: *DomainBlockHeaderToBlockHeader(daaBlock.Header),
+			},
 			GHOSTDAGData: domainGHOSTDAGDataGHOSTDAGData(daaBlock.GHOSTDAGData),
 		}
 	}
@@ -515,7 +532,41 @@ func DomainBlockWithTrustedDataToBlockWithTrustedData(block *externalapi.BlockWi
 
 	return &MsgBlockWithTrustedData{
 		Block:        DomainBlockToMsgBlock(block.Block),
-		DAAScore:     block.DAAScore,
+		DAAScore:     block.Block.Header.DAAScore(),
+		DAAWindow:    daaWindow,
+		GHOSTDAGData: ghostdagData,
+	}
+}
+
+// DomainBlockWithTrustedDataToBlockWithTrustedDataV4 converts a set of *externalapi.DomainBlock, daa window indices and ghostdag data indices
+// to *MsgBlockWithTrustedDataV4
+func DomainBlockWithTrustedDataToBlockWithTrustedDataV4(block *externalapi.DomainBlock, daaWindowIndices, ghostdagDataIndices []uint64) *MsgBlockWithTrustedDataV4 {
+	return &MsgBlockWithTrustedDataV4{
+		Block:               DomainBlockToMsgBlock(block),
+		DAAWindowIndices:    daaWindowIndices,
+		GHOSTDAGDataIndices: ghostdagDataIndices,
+	}
+}
+
+// DomainTrustedDataToTrustedData converts *externalapi.BlockWithTrustedData to *MsgBlockWithTrustedData
+func DomainTrustedDataToTrustedData(domainDAAWindow []*externalapi.TrustedDataDataDAAHeader, domainGHOSTDAGData []*externalapi.BlockGHOSTDAGDataHashPair) *MsgTrustedData {
+	daaWindow := make([]*TrustedDataDAAHeader, len(domainDAAWindow))
+	for i, daaBlock := range domainDAAWindow {
+		daaWindow[i] = &TrustedDataDAAHeader{
+			Header:       DomainBlockHeaderToBlockHeader(daaBlock.Header),
+			GHOSTDAGData: domainGHOSTDAGDataGHOSTDAGData(daaBlock.GHOSTDAGData),
+		}
+	}
+
+	ghostdagData := make([]*BlockGHOSTDAGDataHashPair, len(domainGHOSTDAGData))
+	for i, datum := range domainGHOSTDAGData {
+		ghostdagData[i] = &BlockGHOSTDAGDataHashPair{
+			Hash:         datum.Hash,
+			GHOSTDAGData: domainGHOSTDAGDataGHOSTDAGData(datum.GHOSTDAGData),
+		}
+	}
+
+	return &MsgTrustedData{
 		DAAWindow:    daaWindow,
 		GHOSTDAGData: ghostdagData,
 	}

app/appmessage/error.go

@@ -38,6 +38,10 @@ type RPCError struct {
 	Message string
 }
 
+func (err RPCError) Error() string {
+	return err.Message
+}
+
 // RPCErrorf formats according to a format specifier and returns the string
 // as an RPCError.
 func RPCErrorf(format string, args ...interface{}) *RPCError {

app/appmessage/message.go

@@ -66,6 +66,13 @@ const (
 	CmdPruningPoints
 	CmdRequestPruningPointProof
 	CmdPruningPointProof
+	CmdReady
+	CmdTrustedData
+	CmdBlockWithTrustedDataV4
+	CmdRequestNextPruningPointAndItsAnticoneBlocks
+	CmdRequestIBDChainBlockLocator
+	CmdIBDChainBlockLocator
+	CmdRequestAnticone
 
 	// rpc
 	CmdGetCurrentNetworkRequestMessage
@@ -124,6 +131,8 @@ const (
 	CmdStopNotifyingUTXOsChangedResponseMessage
 	CmdGetUTXOsByAddressesRequestMessage
 	CmdGetUTXOsByAddressesResponseMessage
+	CmdGetBalanceByAddressRequestMessage
+	CmdGetBalanceByAddressResponseMessage
 	CmdGetVirtualSelectedParentBlueScoreRequestMessage
 	CmdGetVirtualSelectedParentBlueScoreResponseMessage
 	CmdNotifyVirtualSelectedParentBlueScoreChangedRequestMessage
@@ -145,6 +154,8 @@ const (
 	CmdNotifyVirtualDaaScoreChangedRequestMessage
 	CmdNotifyVirtualDaaScoreChangedResponseMessage
 	CmdVirtualDaaScoreChangedNotificationMessage
+	CmdGetBalancesByAddressesRequestMessage
+	CmdGetBalancesByAddressesResponseMessage
 )
 
 // ProtocolMessageCommandToString maps all MessageCommands to their string representation
@@ -185,6 +196,13 @@ var ProtocolMessageCommandToString = map[MessageCommand]string{
 	CmdPruningPoints:                       "PruningPoints",
 	CmdRequestPruningPointProof:            "RequestPruningPointProof",
 	CmdPruningPointProof:                   "PruningPointProof",
+	CmdReady:                               "Ready",
+	CmdTrustedData:                         "TrustedData",
+	CmdBlockWithTrustedDataV4:              "BlockWithTrustedDataV4",
+	CmdRequestNextPruningPointAndItsAnticoneBlocks: "RequestNextPruningPointAndItsAnticoneBlocks",
+	CmdRequestIBDChainBlockLocator:                 "RequestIBDChainBlockLocator",
+	CmdIBDChainBlockLocator:                        "IBDChainBlockLocator",
+	CmdRequestAnticone:                             "RequestAnticone",
 }
 
 // RPCMessageCommandToString maps all MessageCommands to their string representation
@@ -243,6 +261,8 @@ var RPCMessageCommandToString = map[MessageCommand]string{
 	CmdStopNotifyingUTXOsChangedResponseMessage:                   "StopNotifyingUTXOsChangedResponse",
 	CmdGetUTXOsByAddressesRequestMessage:                          "GetUTXOsByAddressesRequest",
 	CmdGetUTXOsByAddressesResponseMessage:                         "GetUTXOsByAddressesResponse",
+	CmdGetBalanceByAddressRequestMessage:                          "GetBalanceByAddressRequest",
+	CmdGetBalanceByAddressResponseMessage:                         "GetBalancesByAddressResponse",
 	CmdGetVirtualSelectedParentBlueScoreRequestMessage:            "GetVirtualSelectedParentBlueScoreRequest",
 	CmdGetVirtualSelectedParentBlueScoreResponseMessage:           "GetVirtualSelectedParentBlueScoreResponse",
 	CmdNotifyVirtualSelectedParentBlueScoreChangedRequestMessage:  "NotifyVirtualSelectedParentBlueScoreChangedRequest",
@@ -264,6 +284,8 @@ var RPCMessageCommandToString = map[MessageCommand]string{
 	CmdNotifyVirtualDaaScoreChangedRequestMessage:                 "NotifyVirtualDaaScoreChangedRequest",
 	CmdNotifyVirtualDaaScoreChangedResponseMessage:                "NotifyVirtualDaaScoreChangedResponse",
 	CmdVirtualDaaScoreChangedNotificationMessage:                  "VirtualDaaScoreChangedNotification",
+	CmdGetBalancesByAddressesRequestMessage:                       "GetBalancesByAddressesRequest",
+	CmdGetBalancesByAddressesResponseMessage:                      "GetBalancesByAddressesResponse",
 }
 
 // Message is an interface that describes a kaspa message. A type that

app/appmessage/p2p_msgblock_test.go

@@ -18,7 +18,7 @@ import (
 
 // TestBlock tests the MsgBlock API.
 func TestBlock(t *testing.T) {
-	pver := ProtocolVersion
+	pver := uint32(4)
 
 	// Block 1 header.
 	parents := blockOne.Header.Parents

app/appmessage/p2p_msgblockwithtrusteddatav4.go

@@ -0,0 +1,20 @@
+package appmessage
+
+// MsgBlockWithTrustedDataV4 represents a kaspa BlockWithTrustedDataV4 message
+type MsgBlockWithTrustedDataV4 struct {
+	baseMessage
+
+	Block               *MsgBlock
+	DAAWindowIndices    []uint64
+	GHOSTDAGDataIndices []uint64
+}
+
+// Command returns the protocol command string for the message
+func (msg *MsgBlockWithTrustedDataV4) Command() MessageCommand {
+	return CmdBlockWithTrustedDataV4
+}
+
+// NewMsgBlockWithTrustedDataV4 returns a new MsgBlockWithTrustedDataV4.
+func NewMsgBlockWithTrustedDataV4() *MsgBlockWithTrustedDataV4 {
+	return &MsgBlockWithTrustedDataV4{}
+}

app/appmessage/p2p_msgibdchainblocklocator.go

@@ -0,0 +1,27 @@
+package appmessage
+
+import (
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+)
+
+// MsgIBDChainBlockLocator implements the Message interface and represents a kaspa
+// locator message. It is used to find the blockLocator of a peer that is
+// syncing with you.
+type MsgIBDChainBlockLocator struct {
+	baseMessage
+	BlockLocatorHashes []*externalapi.DomainHash
+}
+
+// Command returns the protocol command string for the message. This is part
+// of the Message interface implementation.
+func (msg *MsgIBDChainBlockLocator) Command() MessageCommand {
+	return CmdIBDChainBlockLocator
+}
+
+// NewMsgIBDChainBlockLocator returns a new kaspa locator message that conforms to
+// the Message interface. See MsgBlockLocator for details.
+func NewMsgIBDChainBlockLocator(locatorHashes []*externalapi.DomainHash) *MsgIBDChainBlockLocator {
+	return &MsgIBDChainBlockLocator{
+		BlockLocatorHashes: locatorHashes,
+	}
+}

app/appmessage/p2p_msgrequestanticone.go

@@ -0,0 +1,33 @@
+// Copyright (c) 2013-2016 The btcsuite developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+package appmessage
+
+import (
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+)
+
+// MsgRequestAnticone implements the Message interface and represents a kaspa
+// RequestHeaders message. It is used to request the set past(ContextHash) \cap anticone(BlockHash)
+type MsgRequestAnticone struct {
+	baseMessage
+	BlockHash   *externalapi.DomainHash
+	ContextHash *externalapi.DomainHash
+}
+
+// Command returns the protocol command string for the message. This is part
+// of the Message interface implementation.
+func (msg *MsgRequestAnticone) Command() MessageCommand {
+	return CmdRequestAnticone
+}
+
+// NewMsgRequestAnticone returns a new kaspa RequestPastDiff message that conforms to the
+// Message interface using the passed parameters and defaults for the remaining
+// fields.
+func NewMsgRequestAnticone(blockHash, contextHash *externalapi.DomainHash) *MsgRequestAnticone {
+	return &MsgRequestAnticone{
+		BlockHash:   blockHash,
+		ContextHash: contextHash,
+	}
+}

app/appmessage/p2p_msgrequestibdchainblocklocator.go

@@ -0,0 +1,31 @@
+package appmessage
+
+import (
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+)
+
+// MsgRequestIBDChainBlockLocator implements the Message interface and represents a kaspa
+// IBDRequestChainBlockLocator message. It is used to request a block locator between low
+// and high hash.
+// The locator is returned via a locator message (MsgIBDChainBlockLocator).
+type MsgRequestIBDChainBlockLocator struct {
+	baseMessage
+	HighHash *externalapi.DomainHash
+	LowHash  *externalapi.DomainHash
+}
+
+// Command returns the protocol command string for the message. This is part
+// of the Message interface implementation.
+func (msg *MsgRequestIBDChainBlockLocator) Command() MessageCommand {
+	return CmdRequestIBDChainBlockLocator
+}
+
+// NewMsgIBDRequestChainBlockLocator returns a new IBDRequestChainBlockLocator message that conforms to the
+// Message interface using the passed parameters and defaults for the remaining
+// fields.
+func NewMsgIBDRequestChainBlockLocator(highHash, lowHash *externalapi.DomainHash) *MsgRequestIBDChainBlockLocator {
+	return &MsgRequestIBDChainBlockLocator{
+		HighHash: highHash,
+		LowHash:  lowHash,
+	}
+}

app/appmessage/p2p_msgrequestnextpruningpointanditsanticoneblocks.go

@@ -0,0 +1,22 @@
+package appmessage
+
+// MsgRequestNextPruningPointAndItsAnticoneBlocks implements the Message interface and represents a kaspa
+// RequestNextPruningPointAndItsAnticoneBlocks message. It is used to notify the IBD syncer peer to send
+// more blocks from the pruning anticone.
+//
+// This message has no payload.
+type MsgRequestNextPruningPointAndItsAnticoneBlocks struct {
+	baseMessage
+}
+
+// Command returns the protocol command string for the message. This is part
+// of the Message interface implementation.
+func (msg *MsgRequestNextPruningPointAndItsAnticoneBlocks) Command() MessageCommand {
+	return CmdRequestNextPruningPointAndItsAnticoneBlocks
+}
+
+// NewMsgRequestNextPruningPointAndItsAnticoneBlocks returns a new kaspa RequestNextPruningPointAndItsAnticoneBlocks message that conforms to the
+// Message interface.
+func NewMsgRequestNextPruningPointAndItsAnticoneBlocks() *MsgRequestNextPruningPointAndItsAnticoneBlocks {
+	return &MsgRequestNextPruningPointAndItsAnticoneBlocks{}
+}

app/appmessage/p2p_msgtrusteddata.go

@@ -0,0 +1,25 @@
+package appmessage
+
+// MsgTrustedData represents a kaspa TrustedData message
+type MsgTrustedData struct {
+	baseMessage
+
+	DAAWindow    []*TrustedDataDAAHeader
+	GHOSTDAGData []*BlockGHOSTDAGDataHashPair
+}
+
+// Command returns the protocol command string for the message
+func (msg *MsgTrustedData) Command() MessageCommand {
+	return CmdTrustedData
+}
+
+// NewMsgTrustedData returns a new MsgTrustedData.
+func NewMsgTrustedData() *MsgTrustedData {
+	return &MsgTrustedData{}
+}
+
+// TrustedDataDAAHeader is an appmessage representation of externalapi.TrustedDataDataDAAHeader
+type TrustedDataDAAHeader struct {
+	Header       *MsgBlockHeader
+	GHOSTDAGData *BlockGHOSTDAGData
+}

app/appmessage/p2p_msgtx_test.go

@@ -22,7 +22,7 @@ import (
 
 // TestTx tests the MsgTx API.
 func TestTx(t *testing.T) {
-	pver := ProtocolVersion
+	pver := uint32(4)
 
 	txIDStr := "000000000003ba27aa200b1cecaad478d2b00432346c3f1f3986da1afd33e506"
 	txID, err := transactionid.FromString(txIDStr)

app/appmessage/p2p_msgversion.go

@@ -82,12 +82,12 @@ func (msg *MsgVersion) Command() MessageCommand {
 // Message interface using the passed parameters and defaults for the remaining
 // fields.
 func NewMsgVersion(addr *NetAddress, id *id.ID, network string,
-	subnetworkID *externalapi.DomainSubnetworkID) *MsgVersion {
+	subnetworkID *externalapi.DomainSubnetworkID, protocolVersion uint32) *MsgVersion {
 
 	// Limit the timestamp to one millisecond precision since the protocol
 	// doesn't support better.
 	return &MsgVersion{
-		ProtocolVersion: ProtocolVersion,
+		ProtocolVersion: protocolVersion,
 		Network:         network,
 		Services:        0,
 		Timestamp:       mstime.Now(),

app/appmessage/p2p_msgversion_test.go

@@ -15,7 +15,7 @@ import (
 
 // TestVersion tests the MsgVersion API.
 func TestVersion(t *testing.T) {
-	pver := ProtocolVersion
+	pver := uint32(4)
 
 	// Create version message data.
 	tcpAddrMe := &net.TCPAddr{IP: net.ParseIP("127.0.0.1"), Port: 16111}
@@ -26,7 +26,7 @@ func TestVersion(t *testing.T) {
 	}
 
 	// Ensure we get the correct data back out.
-	msg := NewMsgVersion(me, generatedID, "mainnet", nil)
+	msg := NewMsgVersion(me, generatedID, "mainnet", nil, 4)
 	if msg.ProtocolVersion != pver {
 		t.Errorf("NewMsgVersion: wrong protocol version - got %v, want %v",
 			msg.ProtocolVersion, pver)

app/appmessage/p2p_netaddress.go

@@ -5,8 +5,9 @@
 package appmessage
 
 import (
-	"github.com/kaspanet/kaspad/util/mstime"
 	"net"
+
+	"github.com/kaspanet/kaspad/util/mstime"
 )
 
 // NetAddress defines information about a peer on the network including the time
@@ -57,3 +58,7 @@ func NewNetAddressTimestamp(
 func NewNetAddress(addr *net.TCPAddr) *NetAddress {
 	return NewNetAddressIPPort(addr.IP, uint16(addr.Port))
 }
+
+func (na NetAddress) String() string {
+	return na.TCPAddress().String()
+}

app/appmessage/p2p_ready.go

@@ -0,0 +1,22 @@
+package appmessage
+
+// MsgReady implements the Message interface and represents a kaspa
+// Ready message. It is used to notify that the peer is ready to receive
+// messages.
+//
+// This message has no payload.
+type MsgReady struct {
+	baseMessage
+}
+
+// Command returns the protocol command string for the message. This is part
+// of the Message interface implementation.
+func (msg *MsgReady) Command() MessageCommand {
+	return CmdReady
+}
+
+// NewMsgReady returns a new kaspa Ready message that conforms to the
+// Message interface.
+func NewMsgReady() *MsgReady {
+	return &MsgReady{}
+}

app/appmessage/protocol.go

@@ -11,9 +11,6 @@ import (
 )
 
 const (
-	// ProtocolVersion is the latest protocol version this package supports.
-	ProtocolVersion uint32 = 3
-
 	// DefaultServices describes the default services that are supported by
 	// the server.
 	DefaultServices = SFNodeNetwork | SFNodeBloom | SFNodeCF

app/appmessage/rpc_get_balance_by_address.go

@@ -0,0 +1,41 @@
+package appmessage
+
+// GetBalanceByAddressRequestMessage is an appmessage corresponding to
+// its respective RPC message
+type GetBalanceByAddressRequestMessage struct {
+	baseMessage
+	Address string
+}
+
+// Command returns the protocol command string for the message
+func (msg *GetBalanceByAddressRequestMessage) Command() MessageCommand {
+	return CmdGetBalanceByAddressRequestMessage
+}
+
+// NewGetBalanceByAddressRequest returns a instance of the message
+func NewGetBalanceByAddressRequest(address string) *GetBalanceByAddressRequestMessage {
+	return &GetBalanceByAddressRequestMessage{
+		Address: address,
+	}
+}
+
+// GetBalanceByAddressResponseMessage is an appmessage corresponding to
+// its respective RPC message
+type GetBalanceByAddressResponseMessage struct {
+	baseMessage
+	Balance uint64
+
+	Error *RPCError
+}
+
+// Command returns the protocol command string for the message
+func (msg *GetBalanceByAddressResponseMessage) Command() MessageCommand {
+	return CmdGetBalanceByAddressResponseMessage
+}
+
+// NewGetBalanceByAddressResponse returns an instance of the message
+func NewGetBalanceByAddressResponse(Balance uint64) *GetBalanceByAddressResponseMessage {
+	return &GetBalanceByAddressResponseMessage{
+		Balance: Balance,
+	}
+}

app/appmessage/rpc_get_balances_by_addresses.go

@@ -0,0 +1,47 @@
+package appmessage
+
+// GetBalancesByAddressesRequestMessage is an appmessage corresponding to
+// its respective RPC message
+type GetBalancesByAddressesRequestMessage struct {
+	baseMessage
+	Addresses []string
+}
+
+// Command returns the protocol command string for the message
+func (msg *GetBalancesByAddressesRequestMessage) Command() MessageCommand {
+	return CmdGetBalancesByAddressesRequestMessage
+}
+
+// NewGetBalancesByAddressesRequest returns a instance of the message
+func NewGetBalancesByAddressesRequest(addresses []string) *GetBalancesByAddressesRequestMessage {
+	return &GetBalancesByAddressesRequestMessage{
+		Addresses: addresses,
+	}
+}
+
+// BalancesByAddressesEntry represents the balance of some address
+type BalancesByAddressesEntry struct {
+	Address string
+	Balance uint64
+}
+
+// GetBalancesByAddressesResponseMessage is an appmessage corresponding to
+// its respective RPC message
+type GetBalancesByAddressesResponseMessage struct {
+	baseMessage
+	Entries []*BalancesByAddressesEntry
+
+	Error *RPCError
+}
+
+// Command returns the protocol command string for the message
+func (msg *GetBalancesByAddressesResponseMessage) Command() MessageCommand {
+	return CmdGetBalancesByAddressesResponseMessage
+}
+
+// NewGetBalancesByAddressesResponse returns an instance of the message
+func NewGetBalancesByAddressesResponse(entries []*BalancesByAddressesEntry) *GetBalancesByAddressesResponseMessage {
+	return &GetBalancesByAddressesResponseMessage{
+		Entries: entries,
+	}
+}

app/appmessage/rpc_submit_block.go

@@ -4,7 +4,8 @@ package appmessage
 // its respective RPC message
 type SubmitBlockRequestMessage struct {
 	baseMessage
-	Block *RPCBlock
+	Block             *RPCBlock
+	AllowNonDAABlocks bool
 }
 
 // Command returns the protocol command string for the message
@@ -13,9 +14,10 @@ func (msg *SubmitBlockRequestMessage) Command() MessageCommand {
 }
 
 // NewSubmitBlockRequestMessage returns a instance of the message
-func NewSubmitBlockRequestMessage(block *RPCBlock) *SubmitBlockRequestMessage {
+func NewSubmitBlockRequestMessage(block *RPCBlock, allowNonDAABlocks bool) *SubmitBlockRequestMessage {
 	return &SubmitBlockRequestMessage{
-		Block: block,
+		Block:             block,
+		AllowNonDAABlocks: allowNonDAABlocks,
 	}
 }
 
@@ -90,11 +92,14 @@ type RPCBlockLevelParents struct {
 
 // RPCBlockVerboseData holds verbose data about a block
 type RPCBlockVerboseData struct {
-	Hash               string
-	Difficulty         float64
-	SelectedParentHash string
-	TransactionIDs     []string
-	IsHeaderOnly       bool
-	BlueScore          uint64
-	ChildrenHashes     []string
+	Hash                string
+	Difficulty          float64
+	SelectedParentHash  string
+	TransactionIDs      []string
+	IsHeaderOnly        bool
+	BlueScore           uint64
+	ChildrenHashes      []string
+	MergeSetBluesHashes []string
+	MergeSetRedsHashes  []string
+	IsChainBlock        bool
 }

app/component_manager.go

@@ -102,7 +102,7 @@ func NewComponentManager(cfg *config.Config, db infrastructuredatabase.Database,
 
 	var utxoIndex *utxoindex.UTXOIndex
 	if cfg.UTXOIndex {
-		utxoIndex, err = utxoindex.New(domain.Consensus(), db)
+		utxoIndex, err = utxoindex.New(domain, db)
 		if err != nil {
 			return nil, err
 		}
@@ -152,6 +152,7 @@ func setupRPC(
 		utxoIndex,
 		shutDownChan,
 	)
+	protocolManager.SetOnVirtualChange(rpcManager.NotifyVirtualChange)
 	protocolManager.SetOnBlockAddedToDAGHandler(rpcManager.NotifyBlockAddedToDAG)
 	protocolManager.SetOnPruningPointUTXOSetOverrideHandler(rpcManager.NotifyPruningPointUTXOSetOverride)
 

app/protocol/common/common.go

@@ -1,6 +1,8 @@
 package common
 
 import (
+	peerpkg "github.com/kaspanet/kaspad/app/protocol/peer"
+	routerpkg "github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
 	"time"
 
 	"github.com/pkg/errors"
@@ -12,3 +14,14 @@ const DefaultTimeout = 120 * time.Second
 
 // ErrPeerWithSameIDExists signifies that a peer with the same ID already exist.
 var ErrPeerWithSameIDExists = errors.New("ready peer with the same ID already exists")
+
+type flowExecuteFunc func(peer *peerpkg.Peer)
+
+// Flow is a a data structure that is used in order to associate a p2p flow to some route in a router.
+type Flow struct {
+	Name        string
+	ExecuteFunc flowExecuteFunc
+}
+
+// FlowInitializeFunc is a function that is used in order to initialize a flow
+type FlowInitializeFunc func(route *routerpkg.Route, peer *peerpkg.Peer) error

app/protocol/flowcontext/blocks.go

@@ -11,14 +11,13 @@ import (
 	"github.com/pkg/errors"
 
 	"github.com/kaspanet/kaspad/app/appmessage"
-	"github.com/kaspanet/kaspad/app/protocol/flows/blockrelay"
 )
 
 // OnNewBlock updates the mempool after a new block arrival, and
 // relays newly unorphaned transactions and possibly rebroadcast
 // manually added transactions when not in IBD.
 func (f *FlowContext) OnNewBlock(block *externalapi.DomainBlock,
-	blockInsertionResult *externalapi.BlockInsertionResult) error {
+	virtualChangeSet *externalapi.VirtualChangeSet) error {
 
 	hash := consensushashing.BlockHash(block)
 	log.Debugf("OnNewBlock start for block %s", hash)
@@ -32,10 +31,10 @@ func (f *FlowContext) OnNewBlock(block *externalapi.DomainBlock,
 	log.Debugf("OnNewBlock: block %s unorphaned %d blocks", hash, len(unorphaningResults))
 
 	newBlocks := []*externalapi.DomainBlock{block}
-	newBlockInsertionResults := []*externalapi.BlockInsertionResult{blockInsertionResult}
+	newVirtualChangeSets := []*externalapi.VirtualChangeSet{virtualChangeSet}
 	for _, unorphaningResult := range unorphaningResults {
 		newBlocks = append(newBlocks, unorphaningResult.block)
-		newBlockInsertionResults = append(newBlockInsertionResults, unorphaningResult.blockInsertionResult)
+		newVirtualChangeSets = append(newVirtualChangeSets, unorphaningResult.virtualChangeSet)
 	}
 
 	allAcceptedTransactions := make([]*externalapi.DomainTransaction, 0)
@@ -49,8 +48,8 @@ func (f *FlowContext) OnNewBlock(block *externalapi.DomainBlock,
 
 		if f.onBlockAddedToDAGHandler != nil {
 			log.Debugf("OnNewBlock: calling f.onBlockAddedToDAGHandler for block %s", hash)
-			blockInsertionResult = newBlockInsertionResults[i]
-			err := f.onBlockAddedToDAGHandler(newBlock, blockInsertionResult)
+			virtualChangeSet = newVirtualChangeSets[i]
+			err := f.onBlockAddedToDAGHandler(newBlock, virtualChangeSet)
 			if err != nil {
 				return err
 			}
@@ -60,6 +59,15 @@ func (f *FlowContext) OnNewBlock(block *externalapi.DomainBlock,
 	return f.broadcastTransactionsAfterBlockAdded(newBlocks, allAcceptedTransactions)
 }
 
+// OnVirtualChange calls the handler function whenever the virtual block changes.
+func (f *FlowContext) OnVirtualChange(virtualChangeSet *externalapi.VirtualChangeSet) error {
+	if f.onVirtualChangeHandler != nil && virtualChangeSet != nil {
+		return f.onVirtualChangeHandler(virtualChangeSet)
+	}
+
+	return nil
+}
+
 // OnPruningPointUTXOSetOverride calls the handler function whenever the UTXO set
 // resets due to pruning point change via IBD.
 func (f *FlowContext) OnPruningPointUTXOSetOverride() error {
@@ -100,7 +108,7 @@ func (f *FlowContext) broadcastTransactionsAfterBlockAdded(
 
 // SharedRequestedBlocks returns a *blockrelay.SharedRequestedBlocks for sharing
 // data about requested blocks between different peers.
-func (f *FlowContext) SharedRequestedBlocks() *blockrelay.SharedRequestedBlocks {
+func (f *FlowContext) SharedRequestedBlocks() *SharedRequestedBlocks {
 	return f.sharedRequestedBlocks
 }
 
@@ -110,14 +118,14 @@ func (f *FlowContext) AddBlock(block *externalapi.DomainBlock) error {
 		return protocolerrors.Errorf(false, "cannot add header only block")
 	}
 
-	blockInsertionResult, err := f.Domain().Consensus().ValidateAndInsertBlock(block, true)
+	virtualChangeSet, err := f.Domain().Consensus().ValidateAndInsertBlock(block, true)
 	if err != nil {
 		if errors.As(err, &ruleerrors.RuleError{}) {
 			log.Warnf("Validation failed for block %s: %s", consensushashing.BlockHash(block), err)
 		}
 		return err
 	}
-	err = f.OnNewBlock(block, blockInsertionResult)
+	err = f.OnNewBlock(block, virtualChangeSet)
 	if err != nil {
 		return err
 	}
@@ -142,7 +150,7 @@ func (f *FlowContext) TrySetIBDRunning(ibdPeer *peerpkg.Peer) bool {
 		return false
 	}
 	f.ibdPeer = ibdPeer
-	log.Infof("IBD started")
+	log.Infof("IBD started with peer %s", ibdPeer)
 
 	return true
 }

app/protocol/flowcontext/errors.go

@@ -2,6 +2,7 @@ package flowcontext
 
 import (
 	"errors"
+	"strings"
 	"sync/atomic"
 
 	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
@@ -9,6 +10,11 @@ import (
 	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
 )
 
+var (
+	// ErrPingTimeout signifies that a ping operation timed out.
+	ErrPingTimeout = protocolerrors.New(false, "timeout expired on ping")
+)
+
 // HandleError handles an error from a flow,
 // It sends the error to errChan if isStopping == 0 and increments isStopping
 //
@@ -21,8 +27,15 @@ func (*FlowContext) HandleError(err error, flowName string, isStopping *uint32,
 		if protocolErr := (protocolerrors.ProtocolError{}); !errors.As(err, &protocolErr) {
 			panic(err)
 		}
-
-		log.Errorf("error from %s: %s", flowName, err)
+		if errors.Is(err, ErrPingTimeout) {
+			// Avoid printing the call stack on ping timeouts, since users get panicked and this case is not interesting
+			log.Errorf("error from %s: %s", flowName, err)
+		} else {
+			// Explain to the user that this is not a panic, but only a protocol error with a specific peer
+			logFrame := strings.Repeat("=", 52)
+			log.Errorf("Non-critical peer protocol error from %s, printing the full stack for debug purposes: \n%s\n%+v \n%s",
+				flowName, logFrame, err, logFrame)
+		}
 	}
 
 	if atomic.AddUint32(isStopping, 1) == 1 {

app/protocol/flowcontext/flow_context.go

@@ -10,8 +10,6 @@ import (
 
 	"github.com/kaspanet/kaspad/domain"
 
-	"github.com/kaspanet/kaspad/app/protocol/flows/blockrelay"
-	"github.com/kaspanet/kaspad/app/protocol/flows/transactionrelay"
 	peerpkg "github.com/kaspanet/kaspad/app/protocol/peer"
 	"github.com/kaspanet/kaspad/infrastructure/config"
 	"github.com/kaspanet/kaspad/infrastructure/network/addressmanager"
@@ -22,7 +20,10 @@ import (
 
 // OnBlockAddedToDAGHandler is a handler function that's triggered
 // when a block is added to the DAG
-type OnBlockAddedToDAGHandler func(block *externalapi.DomainBlock, blockInsertionResult *externalapi.BlockInsertionResult) error
+type OnBlockAddedToDAGHandler func(block *externalapi.DomainBlock, virtualChangeSet *externalapi.VirtualChangeSet) error
+
+// OnVirtualChangeHandler is a handler function that's triggered when the virtual changes
+type OnVirtualChangeHandler func(virtualChangeSet *externalapi.VirtualChangeSet) error
 
 // OnPruningPointUTXOSetOverrideHandler is a handle function that's triggered whenever the UTXO set
 // resets due to pruning point change via IBD.
@@ -43,14 +44,15 @@ type FlowContext struct {
 
 	timeStarted int64
 
+	onVirtualChangeHandler               OnVirtualChangeHandler
 	onBlockAddedToDAGHandler             OnBlockAddedToDAGHandler
 	onPruningPointUTXOSetOverrideHandler OnPruningPointUTXOSetOverrideHandler
 	onTransactionAddedToMempoolHandler   OnTransactionAddedToMempoolHandler
 
 	lastRebroadcastTime         time.Time
-	sharedRequestedTransactions *transactionrelay.SharedRequestedTransactions
+	sharedRequestedTransactions *SharedRequestedTransactions
 
-	sharedRequestedBlocks *blockrelay.SharedRequestedBlocks
+	sharedRequestedBlocks *SharedRequestedBlocks
 
 	ibdPeer      *peerpkg.Peer
 	ibdPeerMutex sync.RWMutex
@@ -78,8 +80,8 @@ func New(cfg *config.Config, domain domain.Domain, addressManager *addressmanage
 		domain:                           domain,
 		addressManager:                   addressManager,
 		connectionManager:                connectionManager,
-		sharedRequestedTransactions:      transactionrelay.NewSharedRequestedTransactions(),
-		sharedRequestedBlocks:            blockrelay.NewSharedRequestedBlocks(),
+		sharedRequestedTransactions:      NewSharedRequestedTransactions(),
+		sharedRequestedBlocks:            NewSharedRequestedBlocks(),
 		peers:                            make(map[id.ID]*peerpkg.Peer),
 		orphans:                          make(map[externalapi.DomainHash]*externalapi.DomainBlock),
 		timeStarted:                      mstime.Now().UnixMilliseconds(),
@@ -100,6 +102,11 @@ func (f *FlowContext) ShutdownChan() <-chan struct{} {
 	return f.shutdownChan
 }
 
+// SetOnVirtualChangeHandler sets the onVirtualChangeHandler handler
+func (f *FlowContext) SetOnVirtualChangeHandler(onVirtualChangeHandler OnVirtualChangeHandler) {
+	f.onVirtualChangeHandler = onVirtualChangeHandler
+}
+
 // SetOnBlockAddedToDAGHandler sets the onBlockAddedToDAG handler
 func (f *FlowContext) SetOnBlockAddedToDAGHandler(onBlockAddedToDAGHandler OnBlockAddedToDAGHandler) {
 	f.onBlockAddedToDAGHandler = onBlockAddedToDAGHandler

app/protocol/flowcontext/orphans.go

@@ -17,8 +17,8 @@ const maxOrphans = 600
 
 // UnorphaningResult is the result of unorphaning a block
 type UnorphaningResult struct {
-	block                *externalapi.DomainBlock
-	blockInsertionResult *externalapi.BlockInsertionResult
+	block            *externalapi.DomainBlock
+	virtualChangeSet *externalapi.VirtualChangeSet
 }
 
 // AddOrphan adds the block to the orphan set
@@ -90,14 +90,14 @@ func (f *FlowContext) UnorphanBlocks(rootBlock *externalapi.DomainBlock) ([]*Uno
 			}
 		}
 		if canBeUnorphaned {
-			blockInsertionResult, unorphaningSucceeded, err := f.unorphanBlock(orphanHash)
+			virtualChangeSet, unorphaningSucceeded, err := f.unorphanBlock(orphanHash)
 			if err != nil {
 				return nil, err
 			}
 			if unorphaningSucceeded {
 				unorphaningResults = append(unorphaningResults, &UnorphaningResult{
-					block:                orphanBlock,
-					blockInsertionResult: blockInsertionResult,
+					block:            orphanBlock,
+					virtualChangeSet: virtualChangeSet,
 				})
 				processQueue = f.addChildOrphansToProcessQueue(&orphanHash, processQueue)
 			}
@@ -143,14 +143,14 @@ func (f *FlowContext) findChildOrphansOfBlock(blockHash *externalapi.DomainHash)
 	return childOrphans
 }
 
-func (f *FlowContext) unorphanBlock(orphanHash externalapi.DomainHash) (*externalapi.BlockInsertionResult, bool, error) {
+func (f *FlowContext) unorphanBlock(orphanHash externalapi.DomainHash) (*externalapi.VirtualChangeSet, bool, error) {
 	orphanBlock, ok := f.orphans[orphanHash]
 	if !ok {
 		return nil, false, errors.Errorf("attempted to unorphan a non-orphan block %s", orphanHash)
 	}
 	delete(f.orphans, orphanHash)
 
-	blockInsertionResult, err := f.domain.Consensus().ValidateAndInsertBlock(orphanBlock, true)
+	virtualChangeSet, err := f.domain.Consensus().ValidateAndInsertBlock(orphanBlock, true)
 	if err != nil {
 		if errors.As(err, &ruleerrors.RuleError{}) {
 			log.Warnf("Validation failed for orphan block %s: %s", orphanHash, err)
@@ -160,7 +160,7 @@ func (f *FlowContext) unorphanBlock(orphanHash externalapi.DomainHash) (*externa
 	}
 
 	log.Infof("Unorphaned block %s", orphanHash)
-	return blockInsertionResult, true, nil
+	return virtualChangeSet, true, nil
 }
 
 // GetOrphanRoots returns the roots of the missing ancestors DAG of the given orphan

app/protocol/flowcontext/shared_requested_blocks.go

@@ -1,4 +1,4 @@
-package blockrelay
+package flowcontext
 
 import (
 	"sync"
@@ -13,13 +13,15 @@ type SharedRequestedBlocks struct {
 	sync.Mutex
 }
 
-func (s *SharedRequestedBlocks) remove(hash *externalapi.DomainHash) {
+// Remove removes a block from the set.
+func (s *SharedRequestedBlocks) Remove(hash *externalapi.DomainHash) {
 	s.Lock()
 	defer s.Unlock()
 	delete(s.blocks, *hash)
 }
 
-func (s *SharedRequestedBlocks) removeSet(blockHashes map[externalapi.DomainHash]struct{}) {
+// RemoveSet removes a set of blocks from the set.
+func (s *SharedRequestedBlocks) RemoveSet(blockHashes map[externalapi.DomainHash]struct{}) {
 	s.Lock()
 	defer s.Unlock()
 	for hash := range blockHashes {
@@ -27,7 +29,8 @@ func (s *SharedRequestedBlocks) removeSet(blockHashes map[externalapi.DomainHash
 	}
 }
 
-func (s *SharedRequestedBlocks) addIfNotExists(hash *externalapi.DomainHash) (exists bool) {
+// AddIfNotExists adds a block to the set if it doesn't exist yet.
+func (s *SharedRequestedBlocks) AddIfNotExists(hash *externalapi.DomainHash) (exists bool) {
 	s.Lock()
 	defer s.Unlock()
 	_, ok := s.blocks[*hash]

app/protocol/flowcontext/shared_requested_transactions.go

@@ -1,4 +1,4 @@
-package transactionrelay
+package flowcontext
 
 import (
 	"sync"
@@ -13,13 +13,15 @@ type SharedRequestedTransactions struct {
 	sync.Mutex
 }
 
-func (s *SharedRequestedTransactions) remove(txID *externalapi.DomainTransactionID) {
+// Remove removes a transaction from the set.
+func (s *SharedRequestedTransactions) Remove(txID *externalapi.DomainTransactionID) {
 	s.Lock()
 	defer s.Unlock()
 	delete(s.transactions, *txID)
 }
 
-func (s *SharedRequestedTransactions) removeMany(txIDs []*externalapi.DomainTransactionID) {
+// RemoveMany removes a set of transactions from the set.
+func (s *SharedRequestedTransactions) RemoveMany(txIDs []*externalapi.DomainTransactionID) {
 	s.Lock()
 	defer s.Unlock()
 	for _, txID := range txIDs {
@@ -27,7 +29,8 @@ func (s *SharedRequestedTransactions) removeMany(txIDs []*externalapi.DomainTran
 	}
 }
 
-func (s *SharedRequestedTransactions) addIfNotExists(txID *externalapi.DomainTransactionID) (exists bool) {
+// AddIfNotExists adds a transaction to the set if it doesn't exist yet.
+func (s *SharedRequestedTransactions) AddIfNotExists(txID *externalapi.DomainTransactionID) (exists bool) {
 	s.Lock()
 	defer s.Unlock()
 	_, ok := s.transactions[*txID]

app/protocol/flowcontext/should_mine.go

@@ -25,6 +25,10 @@ func (f *FlowContext) ShouldMine() (bool, error) {
 		return false, err
 	}
 
+	if virtualSelectedParent.Equal(f.Config().NetParams().GenesisHash) {
+		return false, nil
+	}
+
 	virtualSelectedParentHeader, err := f.domain.Consensus().GetBlockHeader(virtualSelectedParent)
 	if err != nil {
 		return false, err

app/protocol/flowcontext/transactions.go

@@ -4,7 +4,6 @@ import (
 	"time"
 
 	"github.com/kaspanet/kaspad/app/appmessage"
-	"github.com/kaspanet/kaspad/app/protocol/flows/transactionrelay"
 	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
 	"github.com/kaspanet/kaspad/domain/consensus/utils/consensushashing"
 )
@@ -30,7 +29,7 @@ func (f *FlowContext) shouldRebroadcastTransactions() bool {
 
 // SharedRequestedTransactions returns a *transactionrelay.SharedRequestedTransactions for sharing
 // data about requested transactions between different peers.
-func (f *FlowContext) SharedRequestedTransactions() *transactionrelay.SharedRequestedTransactions {
+func (f *FlowContext) SharedRequestedTransactions() *SharedRequestedTransactions {
 	return f.sharedRequestedTransactions
 }
 

app/protocol/flows/blockrelay/handle_pruning_point_and_its_anticone_requests.go

@@ -1,95 +0,0 @@
-package blockrelay
-
-import (
-	"github.com/kaspanet/kaspad/app/appmessage"
-	peerpkg "github.com/kaspanet/kaspad/app/protocol/peer"
-	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
-	"github.com/kaspanet/kaspad/domain"
-	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
-	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
-	"runtime"
-	"sync/atomic"
-)
-
-// PruningPointAndItsAnticoneRequestsContext is the interface for the context needed for the HandlePruningPointAndItsAnticoneRequests flow.
-type PruningPointAndItsAnticoneRequestsContext interface {
-	Domain() domain.Domain
-}
-
-var isBusy uint32
-
-// HandlePruningPointAndItsAnticoneRequests listens to appmessage.MsgRequestPruningPointAndItsAnticone messages and sends
-// the pruning point and its anticone to the requesting peer.
-func HandlePruningPointAndItsAnticoneRequests(context PruningPointAndItsAnticoneRequestsContext, incomingRoute *router.Route,
-	outgoingRoute *router.Route, peer *peerpkg.Peer) error {
-
-	for {
-		err := func() error {
-			_, err := incomingRoute.Dequeue()
-			if err != nil {
-				return err
-			}
-
-			if !atomic.CompareAndSwapUint32(&isBusy, 0, 1) {
-				return protocolerrors.Errorf(false, "node is busy with other pruning point anticone requests")
-			}
-			defer atomic.StoreUint32(&isBusy, 0)
-
-			log.Debugf("Got request for pruning point and its anticone from %s", peer)
-
-			pruningPointHeaders, err := context.Domain().Consensus().PruningPointHeaders()
-			if err != nil {
-				return err
-			}
-
-			msgPruningPointHeaders := make([]*appmessage.MsgBlockHeader, len(pruningPointHeaders))
-			for i, header := range pruningPointHeaders {
-				msgPruningPointHeaders[i] = appmessage.DomainBlockHeaderToBlockHeader(header)
-			}
-
-			err = outgoingRoute.Enqueue(appmessage.NewMsgPruningPoints(msgPruningPointHeaders))
-			if err != nil {
-				return err
-			}
-
-			pointAndItsAnticone, err := context.Domain().Consensus().PruningPointAndItsAnticone()
-			if err != nil {
-				return err
-			}
-
-			for _, blockHash := range pointAndItsAnticone {
-				err := sendBlockWithTrustedData(context, outgoingRoute, blockHash)
-				if err != nil {
-					return err
-				}
-			}
-
-			err = outgoingRoute.Enqueue(appmessage.NewMsgDoneBlocksWithTrustedData())
-			if err != nil {
-				return err
-			}
-
-			log.Debugf("Sent pruning point and its anticone to %s", peer)
-			return nil
-		}()
-		if err != nil {
-			return err
-		}
-	}
-}
-
-func sendBlockWithTrustedData(context PruningPointAndItsAnticoneRequestsContext, outgoingRoute *router.Route, blockHash *externalapi.DomainHash) error {
-	blockWithTrustedData, err := context.Domain().Consensus().BlockWithTrustedData(blockHash)
-	if err != nil {
-		return err
-	}
-
-	err = outgoingRoute.Enqueue(appmessage.DomainBlockWithTrustedDataToBlockWithTrustedData(blockWithTrustedData))
-	if err != nil {
-		return err
-	}
-
-	runtime.GC()
-
-	return nil
-}

app/protocol/flows/handshake/handshake.go

@@ -28,7 +28,7 @@ type HandleHandshakeContext interface {
 	HandleError(err error, flowName string, isStopping *uint32, errChan chan<- error)
 }
 
-// HandleHandshake sets up the handshake protocol - It sends a version message and waits for an incoming
+// HandleHandshake sets up the new_handshake protocol - It sends a version message and waits for an incoming
 // version message, as well as a verack for the sent version
 func HandleHandshake(context HandleHandshakeContext, netConnection *netadapter.NetConnection,
 	receiveVersionRoute *routerpkg.Route, sendVersionRoute *routerpkg.Route, outgoingRoute *routerpkg.Route,
@@ -98,7 +98,7 @@ func HandleHandshake(context HandleHandshakeContext, netConnection *netadapter.N
 }
 
 // Handshake is different from other flows, since in it should forward router.ErrRouteClosed to errChan
-// Therefore we implement a separate handleError for handshake
+// Therefore we implement a separate handleError for new_handshake
 func handleError(err error, flowName string, isStopping *uint32, errChan chan error) {
 	if errors.Is(err, routerpkg.ErrRouteClosed) {
 		if atomic.AddUint32(isStopping, 1) == 1 {

app/protocol/flows/handshake/receiveversion.go

@@ -7,6 +7,7 @@ import (
 	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
 	"github.com/kaspanet/kaspad/infrastructure/logger"
 	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+	"github.com/pkg/errors"
 )
 
 var (
@@ -17,7 +18,9 @@ var (
 
 	// minAcceptableProtocolVersion is the lowest protocol version that a
 	// connected peer may support.
-	minAcceptableProtocolVersion = appmessage.ProtocolVersion
+	minAcceptableProtocolVersion = uint32(4)
+
+	maxAcceptableProtocolVersion = uint32(5)
 )
 
 type receiveVersionFlow struct {
@@ -97,7 +100,12 @@ func (flow *receiveVersionFlow) start() (*appmessage.NetAddress, error) {
 		return nil, protocolerrors.New(false, "incompatible subnetworks")
 	}
 
-	flow.peer.UpdateFieldsFromMsgVersion(msgVersion)
+	if flow.Config().ProtocolVersion > maxAcceptableProtocolVersion {
+		return nil, errors.Errorf("%d is a non existing protocol version", flow.Config().ProtocolVersion)
+	}
+
+	maxProtocolVersion := flow.Config().ProtocolVersion
+	flow.peer.UpdateFieldsFromMsgVersion(msgVersion, maxProtocolVersion)
 	err = flow.outgoingRoute.Enqueue(appmessage.NewMsgVerAck())
 	if err != nil {
 		return nil, err

app/protocol/flows/handshake/sendversion.go

@@ -7,6 +7,7 @@ import (
 	"github.com/kaspanet/kaspad/infrastructure/logger"
 	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
 	"github.com/kaspanet/kaspad/version"
+	"github.com/pkg/errors"
 )
 
 var (
@@ -56,15 +57,18 @@ func (flow *sendVersionFlow) start() error {
 	// Version message.
 	localAddress := flow.AddressManager().BestLocalAddress(flow.peer.Connection().NetAddress())
 	subnetworkID := flow.Config().SubnetworkID
+	if flow.Config().ProtocolVersion < minAcceptableProtocolVersion {
+		return errors.Errorf("configured protocol version %d is obsolete", flow.Config().ProtocolVersion)
+	}
 	msg := appmessage.NewMsgVersion(localAddress, flow.NetAdapter().ID(),
-		flow.Config().ActiveNetParams.Name, subnetworkID)
+		flow.Config().ActiveNetParams.Name, subnetworkID, flow.Config().ProtocolVersion)
 	msg.AddUserAgent(userAgentName, userAgentVersion, flow.Config().UserAgentComments...)
 
 	// Advertise the services flag
 	msg.Services = defaultServices
 
 	// Advertise our max supported protocol version.
-	msg.ProtocolVersion = appmessage.ProtocolVersion
+	msg.ProtocolVersion = flow.Config().ProtocolVersion
 
 	// Advertise if inv messages for transactions are desired.
 	msg.DisableRelayTx = flow.Config().BlocksOnly

app/protocol/flows/ready/log.go

@@ -0,0 +1,9 @@
+package ready
+
+import (
+	"github.com/kaspanet/kaspad/infrastructure/logger"
+	"github.com/kaspanet/kaspad/util/panics"
+)
+
+var log = logger.RegisterSubSystem("PROT")
+var spawn = panics.GoroutineWrapperFunc(log)

app/protocol/flows/ready/ready.go

@@ -0,0 +1,56 @@
+package ready
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/app/protocol/common"
+	"sync/atomic"
+
+	peerpkg "github.com/kaspanet/kaspad/app/protocol/peer"
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	routerpkg "github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+	"github.com/pkg/errors"
+)
+
+// HandleReady notify the other peer that peer is ready for messages, and wait for the other peer
+// to send a ready message before start running the flows.
+func HandleReady(incomingRoute *routerpkg.Route, outgoingRoute *routerpkg.Route,
+	peer *peerpkg.Peer,
+) error {
+
+	log.Debugf("Sending ready message to %s", peer)
+
+	isStopping := uint32(0)
+	err := outgoingRoute.Enqueue(appmessage.NewMsgReady())
+	if err != nil {
+		return handleError(err, "HandleReady", &isStopping)
+	}
+
+	_, err = incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
+	if err != nil {
+		return handleError(err, "HandleReady", &isStopping)
+	}
+
+	log.Debugf("Got ready message from %s", peer)
+
+	return nil
+}
+
+// Ready is different from other flows, since in it should forward router.ErrRouteClosed to errChan
+// Therefore we implement a separate handleError for 'ready'
+func handleError(err error, flowName string, isStopping *uint32) error {
+	if errors.Is(err, routerpkg.ErrRouteClosed) {
+		if atomic.AddUint32(isStopping, 1) == 1 {
+			return err
+		}
+		return nil
+	}
+
+	if protocolErr := (protocolerrors.ProtocolError{}); errors.As(err, &protocolErr) {
+		log.Errorf("Ready protocol error from %s: %s", flowName, err)
+		if atomic.AddUint32(isStopping, 1) == 1 {
+			return err
+		}
+		return nil
+	}
+	panic(err)
+}

app/protocol/flows/v4/blockrelay/batch_size_test.go

@@ -0,0 +1,16 @@
+package blockrelay
+
+import (
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+	"testing"
+)
+
+func TestIBDBatchSizeLessThanRouteCapacity(t *testing.T) {
+	// The `ibdBatchSize` constant must be equal at both syncer and syncee. Therefore, we do not want
+	// to set it to `router.DefaultMaxMessages` to avoid confusion and human errors.
+	// However, nonetheless we must enforce that it does not exceed `router.DefaultMaxMessages`
+	if ibdBatchSize > router.DefaultMaxMessages {
+		t.Fatalf("IBD batch size (%d) must be smaller than or equal to router.DefaultMaxMessages (%d)",
+			ibdBatchSize, router.DefaultMaxMessages)
+	}
+}

app/protocol/flows/v4/blockrelay/block_locator.go

@@ -13,15 +13,21 @@ func (flow *handleRelayInvsFlow) sendGetBlockLocator(highHash *externalapi.Domai
 }
 
 func (flow *handleRelayInvsFlow) receiveBlockLocator() (blockLocatorHashes []*externalapi.DomainHash, err error) {
-	message, err := flow.dequeueIncomingMessageAndSkipInvs(common.DefaultTimeout)
-	if err != nil {
-		return nil, err
+	for {
+		message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
+		if err != nil {
+			return nil, err
+		}
+
+		switch message := message.(type) {
+		case *appmessage.MsgInvRelayBlock:
+			flow.invsQueue = append(flow.invsQueue, message)
+		case *appmessage.MsgBlockLocator:
+			return message.BlockLocatorHashes, nil
+		default:
+			return nil,
+				protocolerrors.Errorf(true, "received unexpected message type. "+
+					"expected: %s, got: %s", appmessage.CmdBlockLocator, message.Command())
+		}
 	}
-	msgBlockLocator, ok := message.(*appmessage.MsgBlockLocator)
-	if !ok {
-		return nil,
-			protocolerrors.Errorf(true, "received unexpected message type. "+
-				"expected: %s, got: %s", appmessage.CmdBlockLocator, message.Command())
-	}
-	return msgBlockLocator.BlockLocatorHashes, nil
 }

app/protocol/flows/v4/blockrelay/handle_ibd_block_requests.go

@@ -33,7 +33,7 @@ func HandleIBDBlockRequests(context HandleIBDBlockRequestsContext, incomingRoute
 				return err
 			}
 			if !blockInfo.Exists || blockInfo.BlockStatus == externalapi.StatusHeaderOnly {
-				return protocolerrors.Errorf(true, "block %s not found", hash)
+				return protocolerrors.Errorf(true, "block %s not found (v4)", hash)
 			}
 			block, err := context.Domain().Consensus().GetBlock(hash)
 			if err != nil {

app/protocol/flows/v4/blockrelay/handle_pruning_point_and_its_anticone_requests.go

@@ -0,0 +1,145 @@
+package blockrelay
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	peerpkg "github.com/kaspanet/kaspad/app/protocol/peer"
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/domain"
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+	"github.com/kaspanet/kaspad/infrastructure/config"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+	"sync/atomic"
+)
+
+// PruningPointAndItsAnticoneRequestsContext is the interface for the context needed for the HandlePruningPointAndItsAnticoneRequests flow.
+type PruningPointAndItsAnticoneRequestsContext interface {
+	Domain() domain.Domain
+	Config() *config.Config
+}
+
+var isBusy uint32
+
+// HandlePruningPointAndItsAnticoneRequests listens to appmessage.MsgRequestPruningPointAndItsAnticone messages and sends
+// the pruning point and its anticone to the requesting peer.
+func HandlePruningPointAndItsAnticoneRequests(context PruningPointAndItsAnticoneRequestsContext, incomingRoute *router.Route,
+	outgoingRoute *router.Route, peer *peerpkg.Peer) error {
+
+	for {
+		err := func() error {
+			_, err := incomingRoute.Dequeue()
+			if err != nil {
+				return err
+			}
+
+			if !atomic.CompareAndSwapUint32(&isBusy, 0, 1) {
+				return protocolerrors.Errorf(false, "node is busy with other pruning point anticone requests")
+			}
+			defer atomic.StoreUint32(&isBusy, 0)
+
+			log.Debugf("Got request for pruning point and its anticone from %s", peer)
+
+			pruningPointHeaders, err := context.Domain().Consensus().PruningPointHeaders()
+			if err != nil {
+				return err
+			}
+
+			msgPruningPointHeaders := make([]*appmessage.MsgBlockHeader, len(pruningPointHeaders))
+			for i, header := range pruningPointHeaders {
+				msgPruningPointHeaders[i] = appmessage.DomainBlockHeaderToBlockHeader(header)
+			}
+
+			err = outgoingRoute.Enqueue(appmessage.NewMsgPruningPoints(msgPruningPointHeaders))
+			if err != nil {
+				return err
+			}
+
+			pointAndItsAnticone, err := context.Domain().Consensus().PruningPointAndItsAnticone()
+			if err != nil {
+				return err
+			}
+
+			windowSize := context.Config().NetParams().DifficultyAdjustmentWindowSize
+			daaWindowBlocks := make([]*externalapi.TrustedDataDataDAAHeader, 0, windowSize)
+			daaWindowHashesToIndex := make(map[externalapi.DomainHash]int, windowSize)
+			trustedDataDAABlockIndexes := make(map[externalapi.DomainHash][]uint64)
+
+			ghostdagData := make([]*externalapi.BlockGHOSTDAGDataHashPair, 0)
+			ghostdagDataHashToIndex := make(map[externalapi.DomainHash]int)
+			trustedDataGHOSTDAGDataIndexes := make(map[externalapi.DomainHash][]uint64)
+			for _, blockHash := range pointAndItsAnticone {
+				blockDAAWindowHashes, err := context.Domain().Consensus().BlockDAAWindowHashes(blockHash)
+				if err != nil {
+					return err
+				}
+
+				trustedDataDAABlockIndexes[*blockHash] = make([]uint64, 0, windowSize)
+				for i, daaBlockHash := range blockDAAWindowHashes {
+					index, exists := daaWindowHashesToIndex[*daaBlockHash]
+					if !exists {
+						trustedDataDataDAAHeader, err := context.Domain().Consensus().TrustedDataDataDAAHeader(blockHash, daaBlockHash, uint64(i))
+						if err != nil {
+							return err
+						}
+						daaWindowBlocks = append(daaWindowBlocks, trustedDataDataDAAHeader)
+						index = len(daaWindowBlocks) - 1
+						daaWindowHashesToIndex[*daaBlockHash] = index
+					}
+
+					trustedDataDAABlockIndexes[*blockHash] = append(trustedDataDAABlockIndexes[*blockHash], uint64(index))
+				}
+
+				ghostdagDataBlockHashes, err := context.Domain().Consensus().TrustedBlockAssociatedGHOSTDAGDataBlockHashes(blockHash)
+				if err != nil {
+					return err
+				}
+
+				trustedDataGHOSTDAGDataIndexes[*blockHash] = make([]uint64, 0, context.Config().NetParams().K)
+				for _, ghostdagDataBlockHash := range ghostdagDataBlockHashes {
+					index, exists := ghostdagDataHashToIndex[*ghostdagDataBlockHash]
+					if !exists {
+						data, err := context.Domain().Consensus().TrustedGHOSTDAGData(ghostdagDataBlockHash)
+						if err != nil {
+							return err
+						}
+						ghostdagData = append(ghostdagData, &externalapi.BlockGHOSTDAGDataHashPair{
+							Hash:         ghostdagDataBlockHash,
+							GHOSTDAGData: data,
+						})
+						index = len(ghostdagData) - 1
+						ghostdagDataHashToIndex[*ghostdagDataBlockHash] = index
+					}
+
+					trustedDataGHOSTDAGDataIndexes[*blockHash] = append(trustedDataGHOSTDAGDataIndexes[*blockHash], uint64(index))
+				}
+			}
+
+			err = outgoingRoute.Enqueue(appmessage.DomainTrustedDataToTrustedData(daaWindowBlocks, ghostdagData))
+			if err != nil {
+				return err
+			}
+
+			for _, blockHash := range pointAndItsAnticone {
+				block, err := context.Domain().Consensus().GetBlock(blockHash)
+				if err != nil {
+					return err
+				}
+
+				err = outgoingRoute.Enqueue(appmessage.DomainBlockWithTrustedDataToBlockWithTrustedDataV4(block, trustedDataDAABlockIndexes[*blockHash], trustedDataGHOSTDAGDataIndexes[*blockHash]))
+				if err != nil {
+					return err
+				}
+			}
+
+			err = outgoingRoute.Enqueue(appmessage.NewMsgDoneBlocksWithTrustedData())
+			if err != nil {
+				return err
+			}
+
+			log.Debugf("Sent pruning point and its anticone to %s", peer)
+			return nil
+		}()
+		if err != nil {
+			return err
+		}
+	}
+}

app/protocol/flows/v4/blockrelay/handle_relay_invs.go

@@ -3,12 +3,14 @@ package blockrelay
 import (
 	"github.com/kaspanet/kaspad/app/appmessage"
 	"github.com/kaspanet/kaspad/app/protocol/common"
+	"github.com/kaspanet/kaspad/app/protocol/flowcontext"
 	peerpkg "github.com/kaspanet/kaspad/app/protocol/peer"
 	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
 	"github.com/kaspanet/kaspad/domain"
 	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
 	"github.com/kaspanet/kaspad/domain/consensus/ruleerrors"
 	"github.com/kaspanet/kaspad/domain/consensus/utils/consensushashing"
+	"github.com/kaspanet/kaspad/domain/consensus/utils/hashset"
 	"github.com/kaspanet/kaspad/infrastructure/config"
 	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
 	"github.com/pkg/errors"
@@ -23,16 +25,15 @@ var orphanResolutionRange uint32 = 5
 type RelayInvsContext interface {
 	Domain() domain.Domain
 	Config() *config.Config
-	OnNewBlock(block *externalapi.DomainBlock, blockInsertionResult *externalapi.BlockInsertionResult) error
+	OnNewBlock(block *externalapi.DomainBlock, virtualChangeSet *externalapi.VirtualChangeSet) error
+	OnVirtualChange(virtualChangeSet *externalapi.VirtualChangeSet) error
 	OnPruningPointUTXOSetOverride() error
-	SharedRequestedBlocks() *SharedRequestedBlocks
+	SharedRequestedBlocks() *flowcontext.SharedRequestedBlocks
 	Broadcast(message appmessage.Message) error
 	AddOrphan(orphanBlock *externalapi.DomainBlock)
 	GetOrphanRoots(orphanHash *externalapi.DomainHash) ([]*externalapi.DomainHash, bool, error)
 	IsOrphan(blockHash *externalapi.DomainHash) bool
 	IsIBDRunning() bool
-	TrySetIBDRunning(ibdPeer *peerpkg.Peer) bool
-	UnsetIBDRunning()
 	IsRecoverableError(err error) bool
 }
 
@@ -55,7 +56,10 @@ func HandleRelayInvs(context RelayInvsContext, incomingRoute *router.Route, outg
 		peer:             peer,
 		invsQueue:        make([]*appmessage.MsgInvRelayBlock, 0),
 	}
-	return flow.start()
+	err := flow.start()
+	// Currently, HandleRelayInvs flow is the only place where IBD is triggered, so the channel can be closed now
+	close(peer.IBDRequestChannel())
+	return err
 }
 
 func (flow *handleRelayInvsFlow) start() error {
@@ -81,7 +85,18 @@ func (flow *handleRelayInvsFlow) start() error {
 			continue
 		}
 
+		isGenesisVirtualSelectedParent, err := flow.isGenesisVirtualSelectedParent()
+		if err != nil {
+			return err
+		}
+
 		if flow.IsOrphan(inv.Hash) {
+			if flow.Config().NetParams().DisallowDirectBlocksOnTopOfGenesis && !flow.Config().AllowSubmitBlockWhenNotSynced && isGenesisVirtualSelectedParent {
+				log.Infof("Cannot process orphan %s for a node with only the genesis block. The node needs to IBD "+
+					"to the recent pruning point before normal operation can resume.", inv.Hash)
+				continue
+			}
+
 			log.Debugf("Block %s is a known orphan. Requesting its missing ancestors", inv.Hash)
 			err := flow.AddOrphanRootsToQueue(inv.Hash)
 			if err != nil {
@@ -111,8 +126,17 @@ func (flow *handleRelayInvsFlow) start() error {
 			return err
 		}
 
+		if flow.Config().NetParams().DisallowDirectBlocksOnTopOfGenesis && !flow.Config().AllowSubmitBlockWhenNotSynced && !flow.Config().Devnet && flow.isChildOfGenesis(block) {
+			log.Infof("Cannot process %s because it's a direct child of genesis.", consensushashing.BlockHash(block))
+			continue
+		}
+
 		log.Debugf("Processing block %s", inv.Hash)
-		missingParents, blockInsertionResult, err := flow.processBlock(block)
+		oldVirtualInfo, err := flow.Domain().Consensus().GetVirtualInfo()
+		if err != nil {
+			return err
+		}
+		missingParents, virtualChangeSet, err := flow.processBlock(block)
 		if err != nil {
 			if errors.Is(err, ruleerrors.ErrPrunedBlock) {
 				log.Infof("Ignoring pruned block %s", inv.Hash)
@@ -134,13 +158,35 @@ func (flow *handleRelayInvsFlow) start() error {
 			continue
 		}
 
-		log.Debugf("Relaying block %s", inv.Hash)
-		err = flow.relayBlock(block)
+		oldVirtualParents := hashset.New()
+		for _, parent := range oldVirtualInfo.ParentHashes {
+			oldVirtualParents.Add(parent)
+		}
+
+		newVirtualInfo, err := flow.Domain().Consensus().GetVirtualInfo()
 		if err != nil {
 			return err
 		}
+
+		for _, parent := range newVirtualInfo.ParentHashes {
+			if oldVirtualParents.Contains(parent) {
+				continue
+			}
+
+			block, err := flow.Domain().Consensus().GetBlock(parent)
+			if err != nil {
+				return err
+			}
+			blockHash := consensushashing.BlockHash(block)
+			log.Debugf("Relaying block %s", blockHash)
+			err = flow.relayBlock(block)
+			if err != nil {
+				return err
+			}
+		}
+
 		log.Infof("Accepted block %s via relay", inv.Hash)
-		err = flow.OnNewBlock(block, blockInsertionResult)
+		err = flow.OnNewBlock(block, virtualChangeSet)
 		if err != nil {
 			return err
 		}
@@ -177,14 +223,14 @@ func (flow *handleRelayInvsFlow) readInv() (*appmessage.MsgInvRelayBlock, error)
 }
 
 func (flow *handleRelayInvsFlow) requestBlock(requestHash *externalapi.DomainHash) (*externalapi.DomainBlock, bool, error) {
-	exists := flow.SharedRequestedBlocks().addIfNotExists(requestHash)
+	exists := flow.SharedRequestedBlocks().AddIfNotExists(requestHash)
 	if exists {
 		return nil, true, nil
 	}
 
 	// In case the function returns earlier than expected, we want to make sure flow.SharedRequestedBlocks() is
 	// clean from any pending blocks.
-	defer flow.SharedRequestedBlocks().remove(requestHash)
+	defer flow.SharedRequestedBlocks().Remove(requestHash)
 
 	getRelayBlocksMsg := appmessage.NewMsgRequestRelayBlocks([]*externalapi.DomainHash{requestHash})
 	err := flow.outgoingRoute.Enqueue(getRelayBlocksMsg)
@@ -227,9 +273,9 @@ func (flow *handleRelayInvsFlow) readMsgBlock() (msgBlock *appmessage.MsgBlock,
 	}
 }
 
-func (flow *handleRelayInvsFlow) processBlock(block *externalapi.DomainBlock) ([]*externalapi.DomainHash, *externalapi.BlockInsertionResult, error) {
+func (flow *handleRelayInvsFlow) processBlock(block *externalapi.DomainBlock) ([]*externalapi.DomainHash, *externalapi.VirtualChangeSet, error) {
 	blockHash := consensushashing.BlockHash(block)
-	blockInsertionResult, err := flow.Domain().Consensus().ValidateAndInsertBlock(block, true)
+	virtualChangeSet, err := flow.Domain().Consensus().ValidateAndInsertBlock(block, true)
 	if err != nil {
 		if !errors.As(err, &ruleerrors.RuleError{}) {
 			return nil, nil, errors.Wrapf(err, "failed to process block %s", blockHash)
@@ -239,10 +285,13 @@ func (flow *handleRelayInvsFlow) processBlock(block *externalapi.DomainBlock) ([
 		if errors.As(err, missingParentsError) {
 			return missingParentsError.MissingParentHashes, nil, nil
 		}
-		log.Warnf("Rejected block %s from %s: %s", blockHash, flow.peer, err)
+		// A duplicate block should not appear to the user as a warning and is already reported in the calling function
+		if !errors.Is(err, ruleerrors.ErrDuplicateBlock) {
+			log.Warnf("Rejected block %s from %s: %s", blockHash, flow.peer, err)
+		}
 		return nil, nil, protocolerrors.Wrapf(true, err, "got invalid block %s from relay", blockHash)
 	}
-	return nil, blockInsertionResult, nil
+	return nil, virtualChangeSet, nil
 }
 
 func (flow *handleRelayInvsFlow) relayBlock(block *externalapi.DomainBlock) error {
@@ -265,6 +314,19 @@ func (flow *handleRelayInvsFlow) processOrphan(block *externalapi.DomainBlock) e
 		return err
 	}
 	if isBlockInOrphanResolutionRange {
+		if flow.Config().NetParams().DisallowDirectBlocksOnTopOfGenesis && !flow.Config().AllowSubmitBlockWhenNotSynced {
+			isGenesisVirtualSelectedParent, err := flow.isGenesisVirtualSelectedParent()
+			if err != nil {
+				return err
+			}
+
+			if isGenesisVirtualSelectedParent {
+				log.Infof("Cannot process orphan %s for a node with only the genesis block. The node needs to IBD "+
+					"to the recent pruning point before normal operation can resume.", blockHash)
+				return nil
+			}
+		}
+
 		log.Debugf("Block %s is within orphan resolution range. "+
 			"Adding it to the orphan set", blockHash)
 		flow.AddOrphan(block)
@@ -275,7 +337,28 @@ func (flow *handleRelayInvsFlow) processOrphan(block *externalapi.DomainBlock) e
 	// Start IBD unless we already are in IBD
 	log.Debugf("Block %s is out of orphan resolution range. "+
 		"Attempting to start IBD against it.", blockHash)
-	return flow.runIBDIfNotRunning(block)
+
+	// Send the block to IBD flow via the IBDRequestChannel.
+	// Note that this is a non-blocking send, since if IBD is already running, there is no need to trigger it
+	select {
+	case flow.peer.IBDRequestChannel() <- block:
+	default:
+	}
+	return nil
+}
+
+func (flow *handleRelayInvsFlow) isGenesisVirtualSelectedParent() (bool, error) {
+	virtualSelectedParent, err := flow.Domain().Consensus().GetVirtualSelectedParent()
+	if err != nil {
+		return false, err
+	}
+
+	return virtualSelectedParent.Equal(flow.Config().NetParams().GenesisHash), nil
+}
+
+func (flow *handleRelayInvsFlow) isChildOfGenesis(block *externalapi.DomainBlock) bool {
+	parents := block.Header.DirectParents()
+	return len(parents) == 1 && parents[0].Equal(flow.Config().NetParams().GenesisHash)
 }
 
 // isBlockInOrphanResolutionRange finds out whether the given blockHash should be
@@ -316,6 +399,10 @@ func (flow *handleRelayInvsFlow) AddOrphanRootsToQueue(orphan *externalapi.Domai
 			"probably happened because it was randomly evicted immediately after it was added.", orphan)
 	}
 
+	if len(orphanRoots) == 0 {
+		// In some rare cases we get here when there are no orphan roots already
+		return nil
+	}
 	log.Infof("Block %s has %d missing ancestors. Adding them to the invs queue...", orphan, len(orphanRoots))
 
 	invMessages := make([]*appmessage.MsgInvRelayBlock, len(orphanRoots))

app/protocol/flows/v4/blockrelay/handle_request_headers.go

@@ -10,7 +10,9 @@ import (
 	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
 )
 
-const ibdBatchSize = router.DefaultMaxMessages
+// This constant must be equal at both syncer and syncee. Therefore, never (!!) change this constant unless a new p2p
+// version is introduced. See `TestIBDBatchSizeLessThanRouteCapacity` as well.
+const ibdBatchSize = 100
 
 // RequestHeadersContext is the interface for the context needed for the HandleRequestHeaders flow.
 type RequestHeadersContext interface {

app/protocol/flows/v4/blockrelay/ibd.go

@@ -1,22 +1,99 @@
 package blockrelay
 
 import (
-	"time"
-
-	"github.com/kaspanet/kaspad/infrastructure/logger"
-
-	"github.com/kaspanet/kaspad/domain/consensus/model"
-
 	"github.com/kaspanet/kaspad/app/appmessage"
 	"github.com/kaspanet/kaspad/app/protocol/common"
+	peerpkg "github.com/kaspanet/kaspad/app/protocol/peer"
 	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/domain"
+	"github.com/kaspanet/kaspad/domain/consensus/model"
 	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
 	"github.com/kaspanet/kaspad/domain/consensus/ruleerrors"
 	"github.com/kaspanet/kaspad/domain/consensus/utils/consensushashing"
+	"github.com/kaspanet/kaspad/infrastructure/config"
+	"github.com/kaspanet/kaspad/infrastructure/logger"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+	"github.com/kaspanet/kaspad/util/difficulty"
 	"github.com/pkg/errors"
+	"math/big"
+	"time"
 )
 
-func (flow *handleRelayInvsFlow) runIBDIfNotRunning(block *externalapi.DomainBlock) error {
+// IBDContext is the interface for the context needed for the HandleIBD flow.
+type IBDContext interface {
+	Domain() domain.Domain
+	Config() *config.Config
+	OnNewBlock(block *externalapi.DomainBlock, virtualChangeSet *externalapi.VirtualChangeSet) error
+	OnVirtualChange(virtualChangeSet *externalapi.VirtualChangeSet) error
+	OnPruningPointUTXOSetOverride() error
+	IsIBDRunning() bool
+	TrySetIBDRunning(ibdPeer *peerpkg.Peer) bool
+	UnsetIBDRunning()
+	IsRecoverableError(err error) bool
+}
+
+type handleIBDFlow struct {
+	IBDContext
+	incomingRoute, outgoingRoute *router.Route
+	peer                         *peerpkg.Peer
+}
+
+// HandleIBD handles IBD
+func HandleIBD(context IBDContext, incomingRoute *router.Route, outgoingRoute *router.Route,
+	peer *peerpkg.Peer) error {
+
+	flow := &handleIBDFlow{
+		IBDContext:    context,
+		incomingRoute: incomingRoute,
+		outgoingRoute: outgoingRoute,
+		peer:          peer,
+	}
+	return flow.start()
+}
+
+func (flow *handleIBDFlow) start() error {
+	for {
+		// Wait for IBD requests triggered by other flows
+		block, ok := <-flow.peer.IBDRequestChannel()
+		if !ok {
+			return nil
+		}
+		err := flow.runIBDIfNotRunning(block)
+		if err != nil {
+			return err
+		}
+	}
+}
+
+func (flow *handleIBDFlow) runIBDIfNotRunning(block *externalapi.DomainBlock) error {
+	highHash := consensushashing.BlockHash(block)
+
+	// Temp code to avoid IBD from lagging nodes publishing their side-chain. This patch
+	// is applied only to p2p v4 since the implemented IBD negotiation has quadratic complexity in this worst-case.
+	// See IBD logic of p2p v5 for further details.
+	virtualSelectedParent, err := flow.Domain().Consensus().GetVirtualSelectedParent()
+	if err == nil {
+		virtualSelectedParentHeader, err := flow.Domain().Consensus().GetBlockHeader(virtualSelectedParent)
+		if err == nil {
+			// We first check that DAA score of the relay block is at distance of more than DAA window size.
+			// This indicates a side-chain which is not in the future of any block in the current virtual DAA window.
+			if virtualSelectedParentHeader.DAAScore() > block.Header.DAAScore()+2641 {
+				// We then find the 'unit' of current virtual difficulty. We check if the relay block is at least
+				// at distance of 180 such units. This signals another condition for a pow-weak side-chain.
+				virtualDifficulty := difficulty.CalcWork(virtualSelectedParentHeader.Bits())
+				var virtualSub, difficultyMul big.Int
+				if difficultyMul.Mul(virtualDifficulty, big.NewInt(180)).
+					Cmp(virtualSub.Sub(virtualSelectedParentHeader.BlueWork(), block.Header.BlueWork())) < 0 {
+					log.Criticalf("Avoiding IBD triggered by relay %s with %d DAA score diff and lower blue work (%d, %d)",
+						highHash,
+						virtualSelectedParentHeader.DAAScore()-block.Header.DAAScore(),
+						virtualSelectedParentHeader.BlueWork(), block.Header.BlueWork())
+					return nil
+				}
+			}
+		}
+	}
+
 	wasIBDNotRunning := flow.TrySetIBDRunning(flow.peer)
 	if !wasIBDNotRunning {
 		log.Debugf("IBD is already running")
@@ -29,15 +106,14 @@ func (flow *handleRelayInvsFlow) runIBDIfNotRunning(block *externalapi.DomainBlo
 		flow.logIBDFinished(isFinishedSuccessfully)
 	}()
 
-	highHash := consensushashing.BlockHash(block)
-	log.Debugf("IBD started with peer %s and highHash %s", flow.peer, highHash)
-	log.Debugf("Syncing blocks up to %s", highHash)
-	log.Debugf("Trying to find highest shared chain block with peer %s with high hash %s", flow.peer, highHash)
+	log.Infof("IBD started with peer %s and highHash %s", flow.peer, highHash)
+	log.Infof("Syncing blocks up to %s", highHash)
+	log.Infof("Trying to find highest shared chain block with peer %s with high hash %s", flow.peer, highHash)
 	highestSharedBlockHash, highestSharedBlockFound, err := flow.findHighestSharedBlockHash(highHash)
 	if err != nil {
 		return err
 	}
-	log.Debugf("Found highest shared chain block %s with peer %s", highestSharedBlockHash, flow.peer)
+	log.Infof("Found highest shared chain block %s with peer %s", highestSharedBlockHash, flow.peer)
 
 	shouldDownloadHeadersProof, shouldSync, err := flow.shouldSyncAndShouldDownloadHeadersProof(block, highestSharedBlockFound)
 	if err != nil {
@@ -50,12 +126,25 @@ func (flow *handleRelayInvsFlow) runIBDIfNotRunning(block *externalapi.DomainBlo
 
 	if shouldDownloadHeadersProof {
 		log.Infof("Starting IBD with headers proof")
-		err := flow.ibdWithHeadersProof(highHash)
+		err := flow.ibdWithHeadersProof(highHash, block.Header.DAAScore())
 		if err != nil {
 			return err
 		}
 	} else {
-		err = flow.syncPruningPointFutureHeaders(flow.Domain().Consensus(), highestSharedBlockHash, highHash)
+		if flow.Config().NetParams().DisallowDirectBlocksOnTopOfGenesis && !flow.Config().AllowSubmitBlockWhenNotSynced {
+			isGenesisVirtualSelectedParent, err := flow.isGenesisVirtualSelectedParent()
+			if err != nil {
+				return err
+			}
+
+			if isGenesisVirtualSelectedParent {
+				log.Infof("Cannot IBD to %s because it won't change the pruning point. The node needs to IBD "+
+					"to the recent pruning point before normal operation can resume.", highHash)
+				return nil
+			}
+		}
+
+		err = flow.syncPruningPointFutureHeaders(flow.Domain().Consensus(), highestSharedBlockHash, highHash, block.Header.DAAScore())
 		if err != nil {
 			return err
 		}
@@ -71,7 +160,16 @@ func (flow *handleRelayInvsFlow) runIBDIfNotRunning(block *externalapi.DomainBlo
 	return nil
 }
 
-func (flow *handleRelayInvsFlow) logIBDFinished(isFinishedSuccessfully bool) {
+func (flow *handleIBDFlow) isGenesisVirtualSelectedParent() (bool, error) {
+	virtualSelectedParent, err := flow.Domain().Consensus().GetVirtualSelectedParent()
+	if err != nil {
+		return false, err
+	}
+
+	return virtualSelectedParent.Equal(flow.Config().NetParams().GenesisHash), nil
+}
+
+func (flow *handleIBDFlow) logIBDFinished(isFinishedSuccessfully bool) {
 	successString := "successfully"
 	if !isFinishedSuccessfully {
 		successString = "(interrupted)"
@@ -82,7 +180,7 @@ func (flow *handleRelayInvsFlow) logIBDFinished(isFinishedSuccessfully bool) {
 // findHighestSharedBlock attempts to find the highest shared block between the peer
 // and this node. This method may fail because the peer and us have conflicting pruning
 // points. In that case we return (nil, false, nil) so that we may stop IBD gracefully.
-func (flow *handleRelayInvsFlow) findHighestSharedBlockHash(
+func (flow *handleIBDFlow) findHighestSharedBlockHash(
 	targetHash *externalapi.DomainHash) (*externalapi.DomainHash, bool, error) {
 
 	log.Debugf("Sending a blockLocator to %s between pruning point and headers selected tip", flow.peer)
@@ -125,7 +223,7 @@ func (flow *handleRelayInvsFlow) findHighestSharedBlockHash(
 	}
 }
 
-func (flow *handleRelayInvsFlow) nextBlockLocator(lowHash, highHash *externalapi.DomainHash) (externalapi.BlockLocator, error) {
+func (flow *handleIBDFlow) nextBlockLocator(lowHash, highHash *externalapi.DomainHash) (externalapi.BlockLocator, error) {
 	log.Debugf("Sending a blockLocator to %s between %s and %s", flow.peer, lowHash, highHash)
 	blockLocator, err := flow.Domain().Consensus().CreateHeadersSelectedChainBlockLocator(lowHash, highHash)
 	if err != nil {
@@ -143,7 +241,7 @@ func (flow *handleRelayInvsFlow) nextBlockLocator(lowHash, highHash *externalapi
 	return blockLocator, nil
 }
 
-func (flow *handleRelayInvsFlow) findHighestHashIndex(
+func (flow *handleIBDFlow) findHighestHashIndex(
 	highestHash *externalapi.DomainHash, blockLocator externalapi.BlockLocator) (int, error) {
 
 	highestHashIndex := 0
@@ -168,7 +266,7 @@ func (flow *handleRelayInvsFlow) findHighestHashIndex(
 // fetchHighestHash attempts to fetch the highest hash the peer knows amongst the given
 // blockLocator. This method may fail because the peer and us have conflicting pruning
 // points. In that case we return (nil, false, nil) so that we may stop IBD gracefully.
-func (flow *handleRelayInvsFlow) fetchHighestHash(
+func (flow *handleIBDFlow) fetchHighestHash(
 	targetHash *externalapi.DomainHash, blockLocator externalapi.BlockLocator) (*externalapi.DomainHash, bool, error) {
 
 	ibdBlockLocatorMessage := appmessage.NewMsgIBDBlockLocator(targetHash, blockLocator)
@@ -176,7 +274,7 @@ func (flow *handleRelayInvsFlow) fetchHighestHash(
 	if err != nil {
 		return nil, false, err
 	}
-	message, err := flow.dequeueIncomingMessageAndSkipInvs(common.DefaultTimeout)
+	message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
 	if err != nil {
 		return nil, false, err
 	}
@@ -196,8 +294,8 @@ func (flow *handleRelayInvsFlow) fetchHighestHash(
 	}
 }
 
-func (flow *handleRelayInvsFlow) syncPruningPointFutureHeaders(consensus externalapi.Consensus, highestSharedBlockHash *externalapi.DomainHash,
-	highHash *externalapi.DomainHash) error {
+func (flow *handleIBDFlow) syncPruningPointFutureHeaders(consensus externalapi.Consensus, highestSharedBlockHash *externalapi.DomainHash,
+	highHash *externalapi.DomainHash, highBlockDAAScore uint64) error {
 
 	log.Infof("Downloading headers from %s", flow.peer)
 
@@ -206,6 +304,12 @@ func (flow *handleRelayInvsFlow) syncPruningPointFutureHeaders(consensus externa
 		return err
 	}
 
+	highestSharedBlockHeader, err := consensus.GetBlockHeader(highestSharedBlockHash)
+	if err != nil {
+		return err
+	}
+	progressReporter := newIBDProgressReporter(highestSharedBlockHeader.DAAScore(), highBlockDAAScore, "block headers")
+
 	// Keep a short queue of BlockHeadersMessages so that there's
 	// never a moment when the node is not validating and inserting
 	// headers
@@ -254,21 +358,24 @@ func (flow *handleRelayInvsFlow) syncPruningPointFutureHeaders(consensus externa
 					return err
 				}
 			}
+
+			lastReceivedHeader := ibdBlocksMessage.BlockHeaders[len(ibdBlocksMessage.BlockHeaders)-1]
+			progressReporter.reportProgress(len(ibdBlocksMessage.BlockHeaders), lastReceivedHeader.DAAScore)
 		case err := <-errChan:
 			return err
 		}
 	}
 }
 
-func (flow *handleRelayInvsFlow) sendRequestHeaders(highestSharedBlockHash *externalapi.DomainHash,
+func (flow *handleIBDFlow) sendRequestHeaders(highestSharedBlockHash *externalapi.DomainHash,
 	peerSelectedTipHash *externalapi.DomainHash) error {
 
 	msgGetBlockInvs := appmessage.NewMsgRequstHeaders(highestSharedBlockHash, peerSelectedTipHash)
 	return flow.outgoingRoute.Enqueue(msgGetBlockInvs)
 }
 
-func (flow *handleRelayInvsFlow) receiveHeaders() (msgIBDBlock *appmessage.BlockHeadersMessage, doneHeaders bool, err error) {
-	message, err := flow.dequeueIncomingMessageAndSkipInvs(common.DefaultTimeout)
+func (flow *handleIBDFlow) receiveHeaders() (msgIBDBlock *appmessage.BlockHeadersMessage, doneHeaders bool, err error) {
+	message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
 	if err != nil {
 		return nil, false, err
 	}
@@ -287,7 +394,7 @@ func (flow *handleRelayInvsFlow) receiveHeaders() (msgIBDBlock *appmessage.Block
 	}
 }
 
-func (flow *handleRelayInvsFlow) processHeader(consensus externalapi.Consensus, msgBlockHeader *appmessage.MsgBlockHeader) error {
+func (flow *handleIBDFlow) processHeader(consensus externalapi.Consensus, msgBlockHeader *appmessage.MsgBlockHeader) error {
 	header := appmessage.BlockHeaderToDomainBlockHeader(msgBlockHeader)
 	block := &externalapi.DomainBlock{
 		Header:       header,
@@ -320,7 +427,7 @@ func (flow *handleRelayInvsFlow) processHeader(consensus externalapi.Consensus,
 	return nil
 }
 
-func (flow *handleRelayInvsFlow) validatePruningPointFutureHeaderTimestamps() error {
+func (flow *handleIBDFlow) validatePruningPointFutureHeaderTimestamps() error {
 	headerSelectedTipHash, err := flow.Domain().StagingConsensus().GetHeadersSelectedTip()
 	if err != nil {
 		return err
@@ -354,7 +461,7 @@ func (flow *handleRelayInvsFlow) validatePruningPointFutureHeaderTimestamps() er
 	return nil
 }
 
-func (flow *handleRelayInvsFlow) receiveAndInsertPruningPointUTXOSet(
+func (flow *handleIBDFlow) receiveAndInsertPruningPointUTXOSet(
 	consensus externalapi.Consensus, pruningPointHash *externalapi.DomainHash) (bool, error) {
 
 	onEnd := logger.LogAndMeasureExecutionTime(log, "receiveAndInsertPruningPointUTXOSet")
@@ -363,7 +470,7 @@ func (flow *handleRelayInvsFlow) receiveAndInsertPruningPointUTXOSet(
 	receivedChunkCount := 0
 	receivedUTXOCount := 0
 	for {
-		message, err := flow.dequeueIncomingMessageAndSkipInvs(common.DefaultTimeout)
+		message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
 		if err != nil {
 			return false, err
 		}
@@ -409,7 +516,7 @@ func (flow *handleRelayInvsFlow) receiveAndInsertPruningPointUTXOSet(
 	}
 }
 
-func (flow *handleRelayInvsFlow) syncMissingBlockBodies(highHash *externalapi.DomainHash) error {
+func (flow *handleIBDFlow) syncMissingBlockBodies(highHash *externalapi.DomainHash) error {
 	hashes, err := flow.Domain().Consensus().GetMissingBlockBodyHashes(highHash)
 	if err != nil {
 		return err
@@ -422,6 +529,17 @@ func (flow *handleRelayInvsFlow) syncMissingBlockBodies(highHash *externalapi.Do
 		return nil
 	}
 
+	lowBlockHeader, err := flow.Domain().Consensus().GetBlockHeader(hashes[0])
+	if err != nil {
+		return err
+	}
+	highBlockHeader, err := flow.Domain().Consensus().GetBlockHeader(hashes[len(hashes)-1])
+	if err != nil {
+		return err
+	}
+	progressReporter := newIBDProgressReporter(lowBlockHeader.DAAScore(), highBlockHeader.DAAScore(), "blocks")
+	highestProcessedDAAScore := lowBlockHeader.DAAScore()
+
 	for offset := 0; offset < len(hashes); offset += ibdBatchSize {
 		var hashesToRequest []*externalapi.DomainHash
 		if offset+ibdBatchSize < len(hashes) {
@@ -436,7 +554,7 @@ func (flow *handleRelayInvsFlow) syncMissingBlockBodies(highHash *externalapi.Do
 		}
 
 		for _, expectedHash := range hashesToRequest {
-			message, err := flow.dequeueIncomingMessageAndSkipInvs(common.DefaultTimeout)
+			message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
 			if err != nil {
 				return err
 			}
@@ -458,7 +576,7 @@ func (flow *handleRelayInvsFlow) syncMissingBlockBodies(highHash *externalapi.Do
 				return err
 			}
 
-			blockInsertionResult, err := flow.Domain().Consensus().ValidateAndInsertBlock(block, false)
+			virtualChangeSet, err := flow.Domain().Consensus().ValidateAndInsertBlock(block, false)
 			if err != nil {
 				if errors.Is(err, ruleerrors.ErrDuplicateBlock) {
 					log.Debugf("Skipping IBD Block %s as it has already been added to the DAG", blockHash)
@@ -466,27 +584,62 @@ func (flow *handleRelayInvsFlow) syncMissingBlockBodies(highHash *externalapi.Do
 				}
 				return protocolerrors.ConvertToBanningProtocolErrorIfRuleError(err, "invalid block %s", blockHash)
 			}
-			err = flow.OnNewBlock(block, blockInsertionResult)
+			err = flow.OnNewBlock(block, virtualChangeSet)
 			if err != nil {
 				return err
 			}
+
+			highestProcessedDAAScore = block.Header.DAAScore()
 		}
+
+		progressReporter.reportProgress(len(hashesToRequest), highestProcessedDAAScore)
 	}
 
-	return flow.Domain().Consensus().ResolveVirtual()
+	return flow.resolveVirtual(highestProcessedDAAScore)
 }
 
-// dequeueIncomingMessageAndSkipInvs is a convenience method to be used during
-// IBD. Inv messages are expected to arrive at any given moment, but should be
-// ignored while we're in IBD
-func (flow *handleRelayInvsFlow) dequeueIncomingMessageAndSkipInvs(timeout time.Duration) (appmessage.Message, error) {
-	for {
-		message, err := flow.incomingRoute.DequeueWithTimeout(timeout)
+func (flow *handleIBDFlow) banIfBlockIsHeaderOnly(block *externalapi.DomainBlock) error {
+	if len(block.Transactions) == 0 {
+		return protocolerrors.Errorf(true, "sent header of %s block where expected block with body",
+			consensushashing.BlockHash(block))
+	}
+
+	return nil
+}
+
+func (flow *handleIBDFlow) resolveVirtual(estimatedVirtualDAAScoreTarget uint64) error {
+	virtualDAAScoreStart, err := flow.Domain().Consensus().GetVirtualDAAScore()
+	if err != nil {
+		return err
+	}
+
+	for i := 0; ; i++ {
+		if i%10 == 0 {
+			virtualDAAScore, err := flow.Domain().Consensus().GetVirtualDAAScore()
+			if err != nil {
+				return err
+			}
+			var percents int
+			if estimatedVirtualDAAScoreTarget-virtualDAAScoreStart <= 0 {
+				percents = 100
+			} else {
+				percents = int(float64(virtualDAAScore-virtualDAAScoreStart) / float64(estimatedVirtualDAAScoreTarget-virtualDAAScoreStart) * 100)
+			}
+			log.Infof("Resolving virtual. Estimated progress: %d%%", percents)
+		}
+		virtualChangeSet, isCompletelyResolved, err := flow.Domain().Consensus().ResolveVirtual()
 		if err != nil {
-			return nil, err
+			return err
 		}
-		if _, ok := message.(*appmessage.MsgInvRelayBlock); !ok {
-			return message, nil
+
+		err = flow.OnVirtualChange(virtualChangeSet)
+		if err != nil {
+			return err
+		}
+
+		if isCompletelyResolved {
+			log.Infof("Resolved virtual")
+			return nil
 		}
 	}
 }

app/protocol/flows/v4/blockrelay/ibd_progress_reporter.go

@@ -0,0 +1,45 @@
+package blockrelay
+
+type ibdProgressReporter struct {
+	lowDAAScore                 uint64
+	highDAAScore                uint64
+	objectName                  string
+	totalDAAScoreDifference     uint64
+	lastReportedProgressPercent int
+	processed                   int
+}
+
+func newIBDProgressReporter(lowDAAScore uint64, highDAAScore uint64, objectName string) *ibdProgressReporter {
+	if highDAAScore <= lowDAAScore {
+		// Avoid a zero or negative diff
+		highDAAScore = lowDAAScore + 1
+	}
+	return &ibdProgressReporter{
+		lowDAAScore:                 lowDAAScore,
+		highDAAScore:                highDAAScore,
+		objectName:                  objectName,
+		totalDAAScoreDifference:     highDAAScore - lowDAAScore,
+		lastReportedProgressPercent: 0,
+		processed:                   0,
+	}
+}
+
+func (ipr *ibdProgressReporter) reportProgress(processedDelta int, highestProcessedDAAScore uint64) {
+	ipr.processed += processedDelta
+
+	// Avoid exploding numbers in the percentage report, since the original `highDAAScore` might have been only a hint
+	if highestProcessedDAAScore > ipr.highDAAScore {
+		ipr.highDAAScore = highestProcessedDAAScore + 1 // + 1 for keeping it at 99%
+		ipr.totalDAAScoreDifference = ipr.highDAAScore - ipr.lowDAAScore
+	}
+	relativeDAAScore := uint64(0)
+	if highestProcessedDAAScore > ipr.lowDAAScore {
+		// Avoid a negative diff
+		relativeDAAScore = highestProcessedDAAScore - ipr.lowDAAScore
+	}
+	progressPercent := int((float64(relativeDAAScore) / float64(ipr.totalDAAScoreDifference)) * 100)
+	if progressPercent > ipr.lastReportedProgressPercent {
+		log.Infof("IBD: Processed %d %s (%d%%)", ipr.processed, ipr.objectName, progressPercent)
+		ipr.lastReportedProgressPercent = progressPercent
+	}
+}

app/protocol/flows/v4/blockrelay/ibd_with_headers_proof.go

@@ -9,20 +9,22 @@ import (
 	"github.com/kaspanet/kaspad/domain/consensus/ruleerrors"
 	"github.com/kaspanet/kaspad/domain/consensus/utils/consensushashing"
 	"github.com/pkg/errors"
+	"time"
 )
 
-func (flow *handleRelayInvsFlow) ibdWithHeadersProof(highHash *externalapi.DomainHash) error {
+func (flow *handleIBDFlow) ibdWithHeadersProof(highHash *externalapi.DomainHash, highBlockDAAScore uint64) error {
 	err := flow.Domain().InitStagingConsensus()
 	if err != nil {
 		return err
 	}
 
-	err = flow.downloadHeadersAndPruningUTXOSet(highHash)
+	err = flow.downloadHeadersAndPruningUTXOSet(highHash, highBlockDAAScore)
 	if err != nil {
 		if !flow.IsRecoverableError(err) {
 			return err
 		}
 
+		log.Infof("IBD with pruning proof from %s was unsuccessful. Deleting the staging consensus.", flow.peer)
 		deleteStagingConsensusErr := flow.Domain().DeleteStagingConsensus()
 		if deleteStagingConsensusErr != nil {
 			return deleteStagingConsensusErr
@@ -31,15 +33,22 @@ func (flow *handleRelayInvsFlow) ibdWithHeadersProof(highHash *externalapi.Domai
 		return err
 	}
 
+	log.Infof("Header download stage of IBD with pruning proof completed successfully from %s. "+
+		"Committing the staging consensus and deleting the previous obsolete one if such exists.", flow.peer)
 	err = flow.Domain().CommitStagingConsensus()
 	if err != nil {
 		return err
 	}
 
+	err = flow.OnPruningPointUTXOSetOverride()
+	if err != nil {
+		return err
+	}
+
 	return nil
 }
 
-func (flow *handleRelayInvsFlow) shouldSyncAndShouldDownloadHeadersProof(highBlock *externalapi.DomainBlock,
+func (flow *handleIBDFlow) shouldSyncAndShouldDownloadHeadersProof(highBlock *externalapi.DomainBlock,
 	highestSharedBlockFound bool) (shouldDownload, shouldSync bool, err error) {
 
 	if !highestSharedBlockFound {
@@ -58,7 +67,7 @@ func (flow *handleRelayInvsFlow) shouldSyncAndShouldDownloadHeadersProof(highBlo
 	return false, true, nil
 }
 
-func (flow *handleRelayInvsFlow) checkIfHighHashHasMoreBlueWorkThanSelectedTipAndPruningDepthMoreBlueScore(highBlock *externalapi.DomainBlock) (bool, error) {
+func (flow *handleIBDFlow) checkIfHighHashHasMoreBlueWorkThanSelectedTipAndPruningDepthMoreBlueScore(highBlock *externalapi.DomainBlock) (bool, error) {
 	headersSelectedTip, err := flow.Domain().Consensus().GetHeadersSelectedTip()
 	if err != nil {
 		return false, err
@@ -76,13 +85,13 @@ func (flow *handleRelayInvsFlow) checkIfHighHashHasMoreBlueWorkThanSelectedTipAn
 	return highBlock.Header.BlueWork().Cmp(headersSelectedTipInfo.BlueWork) > 0, nil
 }
 
-func (flow *handleRelayInvsFlow) syncAndValidatePruningPointProof() (*externalapi.DomainHash, error) {
+func (flow *handleIBDFlow) syncAndValidatePruningPointProof() (*externalapi.DomainHash, error) {
 	log.Infof("Downloading the pruning point proof from %s", flow.peer)
 	err := flow.outgoingRoute.Enqueue(appmessage.NewMsgRequestPruningPointProof())
 	if err != nil {
 		return nil, err
 	}
-	message, err := flow.dequeueIncomingMessageAndSkipInvs(common.DefaultTimeout)
+	message, err := flow.incomingRoute.DequeueWithTimeout(10 * time.Minute)
 	if err != nil {
 		return nil, err
 	}
@@ -108,7 +117,7 @@ func (flow *handleRelayInvsFlow) syncAndValidatePruningPointProof() (*externalap
 	return consensushashing.HeaderHash(pruningPointProof.Headers[0][len(pruningPointProof.Headers[0])-1]), nil
 }
 
-func (flow *handleRelayInvsFlow) downloadHeadersAndPruningUTXOSet(highHash *externalapi.DomainHash) error {
+func (flow *handleIBDFlow) downloadHeadersAndPruningUTXOSet(highHash *externalapi.DomainHash, highBlockDAAScore uint64) error {
 	proofPruningPoint, err := flow.syncAndValidatePruningPointProof()
 	if err != nil {
 		return err
@@ -125,7 +134,7 @@ func (flow *handleRelayInvsFlow) downloadHeadersAndPruningUTXOSet(highHash *exte
 		return protocolerrors.Errorf(true, "the genesis pruning point violates finality")
 	}
 
-	err = flow.syncPruningPointFutureHeaders(flow.Domain().StagingConsensus(), proofPruningPoint, highHash)
+	err = flow.syncPruningPointFutureHeaders(flow.Domain().StagingConsensus(), proofPruningPoint, highHash, highBlockDAAScore)
 	if err != nil {
 		return err
 	}
@@ -159,7 +168,7 @@ func (flow *handleRelayInvsFlow) downloadHeadersAndPruningUTXOSet(highHash *exte
 	return nil
 }
 
-func (flow *handleRelayInvsFlow) syncPruningPointsAndPruningPointAnticone(proofPruningPoint *externalapi.DomainHash) error {
+func (flow *handleIBDFlow) syncPruningPointsAndPruningPointAnticone(proofPruningPoint *externalapi.DomainHash) error {
 	log.Infof("Downloading the past pruning points and the pruning point anticone from %s", flow.peer)
 	err := flow.outgoingRoute.Enqueue(appmessage.NewMsgRequestPruningPointAndItsAnticone())
 	if err != nil {
@@ -171,6 +180,17 @@ func (flow *handleRelayInvsFlow) syncPruningPointsAndPruningPointAnticone(proofP
 		return err
 	}
 
+	message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
+	if err != nil {
+		return err
+	}
+
+	msgTrustedData, ok := message.(*appmessage.MsgTrustedData)
+	if !ok {
+		return protocolerrors.Errorf(true, "received unexpected message type. "+
+			"expected: %s, got: %s", appmessage.CmdTrustedData, message.Command())
+	}
+
 	pruningPointWithMetaData, done, err := flow.receiveBlockWithTrustedData()
 	if err != nil {
 		return err
@@ -184,7 +204,7 @@ func (flow *handleRelayInvsFlow) syncPruningPointsAndPruningPointAnticone(proofP
 		return protocolerrors.Errorf(true, "first block with trusted data is not the pruning point")
 	}
 
-	err = flow.processBlockWithTrustedData(flow.Domain().StagingConsensus(), pruningPointWithMetaData)
+	err = flow.processBlockWithTrustedData(flow.Domain().StagingConsensus(), pruningPointWithMetaData, msgTrustedData)
 	if err != nil {
 		return err
 	}
@@ -199,7 +219,7 @@ func (flow *handleRelayInvsFlow) syncPruningPointsAndPruningPointAnticone(proofP
 			break
 		}
 
-		err = flow.processBlockWithTrustedData(flow.Domain().StagingConsensus(), blockWithTrustedData)
+		err = flow.processBlockWithTrustedData(flow.Domain().StagingConsensus(), blockWithTrustedData, msgTrustedData)
 		if err != nil {
 			return err
 		}
@@ -209,21 +229,35 @@ func (flow *handleRelayInvsFlow) syncPruningPointsAndPruningPointAnticone(proofP
 	return nil
 }
 
-func (flow *handleRelayInvsFlow) processBlockWithTrustedData(
-	consensus externalapi.Consensus, block *appmessage.MsgBlockWithTrustedData) error {
+func (flow *handleIBDFlow) processBlockWithTrustedData(
+	consensus externalapi.Consensus, block *appmessage.MsgBlockWithTrustedDataV4, data *appmessage.MsgTrustedData) error {
 
-	_, err := consensus.ValidateAndInsertBlockWithTrustedData(appmessage.BlockWithTrustedDataToDomainBlockWithTrustedData(block), false)
+	blockWithTrustedData := &externalapi.BlockWithTrustedData{
+		Block:        appmessage.MsgBlockToDomainBlock(block.Block),
+		DAAWindow:    make([]*externalapi.TrustedDataDataDAAHeader, 0, len(block.DAAWindowIndices)),
+		GHOSTDAGData: make([]*externalapi.BlockGHOSTDAGDataHashPair, 0, len(block.GHOSTDAGDataIndices)),
+	}
+
+	for _, index := range block.DAAWindowIndices {
+		blockWithTrustedData.DAAWindow = append(blockWithTrustedData.DAAWindow, appmessage.TrustedDataDataDAABlockV4ToTrustedDataDataDAAHeader(data.DAAWindow[index]))
+	}
+
+	for _, index := range block.GHOSTDAGDataIndices {
+		blockWithTrustedData.GHOSTDAGData = append(blockWithTrustedData.GHOSTDAGData, appmessage.GHOSTDAGHashPairToDomainGHOSTDAGHashPair(data.GHOSTDAGData[index]))
+	}
+
+	_, err := consensus.ValidateAndInsertBlockWithTrustedData(blockWithTrustedData, false)
 	return err
 }
 
-func (flow *handleRelayInvsFlow) receiveBlockWithTrustedData() (*appmessage.MsgBlockWithTrustedData, bool, error) {
-	message, err := flow.dequeueIncomingMessageAndSkipInvs(common.DefaultTimeout)
+func (flow *handleIBDFlow) receiveBlockWithTrustedData() (*appmessage.MsgBlockWithTrustedDataV4, bool, error) {
+	message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
 	if err != nil {
 		return nil, false, err
 	}
 
 	switch downCastedMessage := message.(type) {
-	case *appmessage.MsgBlockWithTrustedData:
+	case *appmessage.MsgBlockWithTrustedDataV4:
 		return downCastedMessage, false, nil
 	case *appmessage.MsgDoneBlocksWithTrustedData:
 		return nil, true, nil
@@ -237,8 +271,8 @@ func (flow *handleRelayInvsFlow) receiveBlockWithTrustedData() (*appmessage.MsgB
 	}
 }
 
-func (flow *handleRelayInvsFlow) receivePruningPoints() (*appmessage.MsgPruningPoints, error) {
-	message, err := flow.dequeueIncomingMessageAndSkipInvs(common.DefaultTimeout)
+func (flow *handleIBDFlow) receivePruningPoints() (*appmessage.MsgPruningPoints, error) {
+	message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
 	if err != nil {
 		return nil, err
 	}
@@ -253,7 +287,7 @@ func (flow *handleRelayInvsFlow) receivePruningPoints() (*appmessage.MsgPruningP
 	return msgPruningPoints, nil
 }
 
-func (flow *handleRelayInvsFlow) validateAndInsertPruningPoints(proofPruningPoint *externalapi.DomainHash) error {
+func (flow *handleIBDFlow) validateAndInsertPruningPoints(proofPruningPoint *externalapi.DomainHash) error {
 	currentPruningPoint, err := flow.Domain().Consensus().PruningPoint()
 	if err != nil {
 		return err
@@ -297,7 +331,7 @@ func (flow *handleRelayInvsFlow) validateAndInsertPruningPoints(proofPruningPoin
 	return nil
 }
 
-func (flow *handleRelayInvsFlow) syncPruningPointUTXOSet(consensus externalapi.Consensus,
+func (flow *handleIBDFlow) syncPruningPointUTXOSet(consensus externalapi.Consensus,
 	pruningPoint *externalapi.DomainHash) (bool, error) {
 
 	log.Infof("Checking if the suggested pruning point %s is compatible to the node DAG", pruningPoint)
@@ -313,6 +347,7 @@ func (flow *handleRelayInvsFlow) syncPruningPointUTXOSet(consensus externalapi.C
 	log.Info("Fetching the pruning point UTXO set")
 	isSuccessful, err := flow.fetchMissingUTXOSet(consensus, pruningPoint)
 	if err != nil {
+		log.Infof("An error occurred while fetching the pruning point UTXO set. Stopping IBD. (%s)", err)
 		return false, err
 	}
 
@@ -325,7 +360,7 @@ func (flow *handleRelayInvsFlow) syncPruningPointUTXOSet(consensus externalapi.C
 	return true, nil
 }
 
-func (flow *handleRelayInvsFlow) fetchMissingUTXOSet(consensus externalapi.Consensus, pruningPointHash *externalapi.DomainHash) (succeed bool, err error) {
+func (flow *handleIBDFlow) fetchMissingUTXOSet(consensus externalapi.Consensus, pruningPointHash *externalapi.DomainHash) (succeed bool, err error) {
 	defer func() {
 		err := flow.Domain().StagingConsensus().ClearImportedPruningPointData()
 		if err != nil {
@@ -355,10 +390,5 @@ func (flow *handleRelayInvsFlow) fetchMissingUTXOSet(consensus externalapi.Conse
 		return false, protocolerrors.ConvertToBanningProtocolErrorIfRuleError(err, "error with pruning point UTXO set")
 	}
 
-	err = flow.OnPruningPointUTXOSetOverride()
-	if err != nil {
-		return false, err
-	}
-
 	return true, nil
 }

app/protocol/flows/v4/ping/send.go

@@ -2,6 +2,8 @@ package ping
 
 import (
 	"github.com/kaspanet/kaspad/app/protocol/common"
+	"github.com/kaspanet/kaspad/app/protocol/flowcontext"
+	"github.com/pkg/errors"
 	"time"
 
 	"github.com/kaspanet/kaspad/app/appmessage"
@@ -61,6 +63,9 @@ func (flow *sendPingsFlow) start() error {
 
 		message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
 		if err != nil {
+			if errors.Is(err, router.ErrTimeout) {
+				return errors.Wrapf(flowcontext.ErrPingTimeout, err.Error())
+			}
 			return err
 		}
 		pongMessage := message.(*appmessage.MsgPong)

app/protocol/flows/v4/register.go

@@ -0,0 +1,194 @@
+package v4
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/app/protocol/common"
+	"github.com/kaspanet/kaspad/app/protocol/flowcontext"
+	"github.com/kaspanet/kaspad/app/protocol/flows/v4/addressexchange"
+	"github.com/kaspanet/kaspad/app/protocol/flows/v4/blockrelay"
+	"github.com/kaspanet/kaspad/app/protocol/flows/v4/ping"
+	"github.com/kaspanet/kaspad/app/protocol/flows/v4/rejects"
+	"github.com/kaspanet/kaspad/app/protocol/flows/v4/transactionrelay"
+	peerpkg "github.com/kaspanet/kaspad/app/protocol/peer"
+	routerpkg "github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+)
+
+type protocolManager interface {
+	RegisterFlow(name string, router *routerpkg.Router, messageTypes []appmessage.MessageCommand, isStopping *uint32,
+		errChan chan error, initializeFunc common.FlowInitializeFunc) *common.Flow
+	RegisterOneTimeFlow(name string, router *routerpkg.Router, messageTypes []appmessage.MessageCommand,
+		isStopping *uint32, stopChan chan error, initializeFunc common.FlowInitializeFunc) *common.Flow
+	RegisterFlowWithCapacity(name string, capacity int, router *routerpkg.Router,
+		messageTypes []appmessage.MessageCommand, isStopping *uint32,
+		errChan chan error, initializeFunc common.FlowInitializeFunc) *common.Flow
+	Context() *flowcontext.FlowContext
+}
+
+// Register is used in order to register all the protocol flows to the given router.
+func Register(m protocolManager, router *routerpkg.Router, errChan chan error, isStopping *uint32) (flows []*common.Flow) {
+	flows = registerAddressFlows(m, router, isStopping, errChan)
+	flows = append(flows, registerBlockRelayFlows(m, router, isStopping, errChan)...)
+	flows = append(flows, registerPingFlows(m, router, isStopping, errChan)...)
+	flows = append(flows, registerTransactionRelayFlow(m, router, isStopping, errChan)...)
+	flows = append(flows, registerRejectsFlow(m, router, isStopping, errChan)...)
+
+	return flows
+}
+
+func registerAddressFlows(m protocolManager, router *routerpkg.Router, isStopping *uint32, errChan chan error) []*common.Flow {
+	outgoingRoute := router.OutgoingRoute()
+
+	return []*common.Flow{
+		m.RegisterFlow("SendAddresses", router, []appmessage.MessageCommand{appmessage.CmdRequestAddresses}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return addressexchange.SendAddresses(m.Context(), incomingRoute, outgoingRoute)
+			},
+		),
+
+		m.RegisterOneTimeFlow("ReceiveAddresses", router, []appmessage.MessageCommand{appmessage.CmdAddresses}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return addressexchange.ReceiveAddresses(m.Context(), incomingRoute, outgoingRoute, peer)
+			},
+		),
+	}
+}
+
+func registerBlockRelayFlows(m protocolManager, router *routerpkg.Router, isStopping *uint32, errChan chan error) []*common.Flow {
+	outgoingRoute := router.OutgoingRoute()
+
+	return []*common.Flow{
+		m.RegisterOneTimeFlow("SendVirtualSelectedParentInv", router, []appmessage.MessageCommand{},
+			isStopping, errChan, func(route *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.SendVirtualSelectedParentInv(m.Context(), outgoingRoute, peer)
+			}),
+
+		m.RegisterFlow("HandleRelayInvs", router, []appmessage.MessageCommand{
+			appmessage.CmdInvRelayBlock, appmessage.CmdBlock, appmessage.CmdBlockLocator,
+		},
+			isStopping, errChan, func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandleRelayInvs(m.Context(), incomingRoute,
+					outgoingRoute, peer)
+			},
+		),
+
+		m.RegisterFlow("HandleIBD", router, []appmessage.MessageCommand{
+			appmessage.CmdDoneHeaders, appmessage.CmdUnexpectedPruningPoint, appmessage.CmdPruningPointUTXOSetChunk,
+			appmessage.CmdBlockHeaders, appmessage.CmdIBDBlockLocatorHighestHash, appmessage.CmdBlockWithTrustedDataV4,
+			appmessage.CmdDoneBlocksWithTrustedData, appmessage.CmdIBDBlockLocatorHighestHashNotFound,
+			appmessage.CmdDonePruningPointUTXOSetChunks, appmessage.CmdIBDBlock, appmessage.CmdPruningPoints,
+			appmessage.CmdPruningPointProof,
+			appmessage.CmdTrustedData,
+		},
+			isStopping, errChan, func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandleIBD(m.Context(), incomingRoute,
+					outgoingRoute, peer)
+			},
+		),
+
+		m.RegisterFlow("HandleRelayBlockRequests", router, []appmessage.MessageCommand{appmessage.CmdRequestRelayBlocks}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandleRelayBlockRequests(m.Context(), incomingRoute, outgoingRoute, peer)
+			},
+		),
+
+		m.RegisterFlow("HandleRequestBlockLocator", router,
+			[]appmessage.MessageCommand{appmessage.CmdRequestBlockLocator}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandleRequestBlockLocator(m.Context(), incomingRoute, outgoingRoute)
+			},
+		),
+
+		m.RegisterFlow("HandleRequestHeaders", router,
+			[]appmessage.MessageCommand{appmessage.CmdRequestHeaders, appmessage.CmdRequestNextHeaders}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandleRequestHeaders(m.Context(), incomingRoute, outgoingRoute, peer)
+			},
+		),
+
+		m.RegisterFlow("HandleIBDBlockRequests", router,
+			[]appmessage.MessageCommand{appmessage.CmdRequestIBDBlocks}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandleIBDBlockRequests(m.Context(), incomingRoute, outgoingRoute)
+			},
+		),
+
+		m.RegisterFlow("HandleRequestPruningPointUTXOSet", router,
+			[]appmessage.MessageCommand{appmessage.CmdRequestPruningPointUTXOSet,
+				appmessage.CmdRequestNextPruningPointUTXOSetChunk}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandleRequestPruningPointUTXOSet(m.Context(), incomingRoute, outgoingRoute)
+			},
+		),
+
+		m.RegisterFlow("HandlePruningPointAndItsAnticoneRequests", router,
+			[]appmessage.MessageCommand{appmessage.CmdRequestPruningPointAndItsAnticone}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandlePruningPointAndItsAnticoneRequests(m.Context(), incomingRoute, outgoingRoute, peer)
+			},
+		),
+
+		m.RegisterFlow("HandleIBDBlockLocator", router,
+			[]appmessage.MessageCommand{appmessage.CmdIBDBlockLocator}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandleIBDBlockLocator(m.Context(), incomingRoute, outgoingRoute, peer)
+			},
+		),
+
+		m.RegisterFlow("HandlePruningPointProofRequests", router,
+			[]appmessage.MessageCommand{appmessage.CmdRequestPruningPointProof}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandlePruningPointProofRequests(m.Context(), incomingRoute, outgoingRoute, peer)
+			},
+		),
+	}
+}
+
+func registerPingFlows(m protocolManager, router *routerpkg.Router, isStopping *uint32, errChan chan error) []*common.Flow {
+	outgoingRoute := router.OutgoingRoute()
+
+	return []*common.Flow{
+		m.RegisterFlow("ReceivePings", router, []appmessage.MessageCommand{appmessage.CmdPing}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return ping.ReceivePings(m.Context(), incomingRoute, outgoingRoute)
+			},
+		),
+
+		m.RegisterFlow("SendPings", router, []appmessage.MessageCommand{appmessage.CmdPong}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return ping.SendPings(m.Context(), incomingRoute, outgoingRoute, peer)
+			},
+		),
+	}
+}
+
+func registerTransactionRelayFlow(m protocolManager, router *routerpkg.Router, isStopping *uint32, errChan chan error) []*common.Flow {
+	outgoingRoute := router.OutgoingRoute()
+
+	return []*common.Flow{
+		m.RegisterFlowWithCapacity("HandleRelayedTransactions", 10_000, router,
+			[]appmessage.MessageCommand{appmessage.CmdInvTransaction, appmessage.CmdTx, appmessage.CmdTransactionNotFound}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return transactionrelay.HandleRelayedTransactions(m.Context(), incomingRoute, outgoingRoute)
+			},
+		),
+		m.RegisterFlow("HandleRequestTransactions", router,
+			[]appmessage.MessageCommand{appmessage.CmdRequestTransactions}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return transactionrelay.HandleRequestedTransactions(m.Context(), incomingRoute, outgoingRoute)
+			},
+		),
+	}
+}
+
+func registerRejectsFlow(m protocolManager, router *routerpkg.Router, isStopping *uint32, errChan chan error) []*common.Flow {
+	outgoingRoute := router.OutgoingRoute()
+
+	return []*common.Flow{
+		m.RegisterFlow("HandleRejects", router,
+			[]appmessage.MessageCommand{appmessage.CmdReject}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return rejects.HandleRejects(m.Context(), incomingRoute, outgoingRoute)
+			},
+		),
+	}
+}

app/protocol/flows/v4/testing/receiveaddresses_test.go

@@ -1,11 +1,11 @@
 package testing
 
 import (
+	"github.com/kaspanet/kaspad/app/protocol/flows/v4/addressexchange"
 	"testing"
 	"time"
 
 	"github.com/kaspanet/kaspad/app/appmessage"
-	"github.com/kaspanet/kaspad/app/protocol/flows/addressexchange"
 	peerpkg "github.com/kaspanet/kaspad/app/protocol/peer"
 	"github.com/kaspanet/kaspad/domain/consensus"
 	"github.com/kaspanet/kaspad/domain/consensus/utils/testutils"

app/protocol/flows/v4/transactionrelay/handle_relayed_transactions.go

@@ -3,6 +3,7 @@ package transactionrelay
 import (
 	"github.com/kaspanet/kaspad/app/appmessage"
 	"github.com/kaspanet/kaspad/app/protocol/common"
+	"github.com/kaspanet/kaspad/app/protocol/flowcontext"
 	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
 	"github.com/kaspanet/kaspad/domain"
 	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
@@ -18,9 +19,10 @@ import (
 type TransactionsRelayContext interface {
 	NetAdapter() *netadapter.NetAdapter
 	Domain() domain.Domain
-	SharedRequestedTransactions() *SharedRequestedTransactions
+	SharedRequestedTransactions() *flowcontext.SharedRequestedTransactions
 	OnTransactionAddedToMempool()
 	EnqueueTransactionIDsForPropagation(transactionIDs []*externalapi.DomainTransactionID) error
+	IsIBDRunning() bool
 }
 
 type handleRelayedTransactionsFlow struct {
@@ -48,6 +50,10 @@ func (flow *handleRelayedTransactionsFlow) start() error {
 			return err
 		}
 
+		if flow.IsIBDRunning() {
+			continue
+		}
+
 		requestedIDs, err := flow.requestInvTransactions(inv)
 		if err != nil {
 			return err
@@ -68,7 +74,7 @@ func (flow *handleRelayedTransactionsFlow) requestInvTransactions(
 		if flow.isKnownTransaction(txID) {
 			continue
 		}
-		exists := flow.SharedRequestedTransactions().addIfNotExists(txID)
+		exists := flow.SharedRequestedTransactions().AddIfNotExists(txID)
 		if exists {
 			continue
 		}
@@ -82,7 +88,7 @@ func (flow *handleRelayedTransactionsFlow) requestInvTransactions(
 	msgGetTransactions := appmessage.NewMsgRequestTransactions(idsToRequest)
 	err = flow.outgoingRoute.Enqueue(msgGetTransactions)
 	if err != nil {
-		flow.SharedRequestedTransactions().removeMany(idsToRequest)
+		flow.SharedRequestedTransactions().RemoveMany(idsToRequest)
 		return nil, err
 	}
 	return idsToRequest, nil
@@ -151,7 +157,7 @@ func (flow *handleRelayedTransactionsFlow) readMsgTxOrNotFound() (
 func (flow *handleRelayedTransactionsFlow) receiveTransactions(requestedTransactions []*externalapi.DomainTransactionID) error {
 	// In case the function returns earlier than expected, we want to make sure sharedRequestedTransactions is
 	// clean from any pending transactions.
-	defer flow.SharedRequestedTransactions().removeMany(requestedTransactions)
+	defer flow.SharedRequestedTransactions().RemoveMany(requestedTransactions)
 	for _, expectedID := range requestedTransactions {
 		msgTx, msgTxNotFound, err := flow.readMsgTxOrNotFound()
 		if err != nil {

app/protocol/flows/v4/transactionrelay/handle_relayed_transactions_test.go

@@ -2,10 +2,11 @@ package transactionrelay_test
 
 import (
 	"errors"
+	"github.com/kaspanet/kaspad/app/protocol/flowcontext"
+	"github.com/kaspanet/kaspad/app/protocol/flows/v4/transactionrelay"
 	"strings"
 	"testing"
 
-	"github.com/kaspanet/kaspad/app/protocol/flows/transactionrelay"
 	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
 	"github.com/kaspanet/kaspad/domain"
 	"github.com/kaspanet/kaspad/domain/consensus"
@@ -24,7 +25,7 @@ import (
 type mocTransactionsRelayContext struct {
 	netAdapter                  *netadapter.NetAdapter
 	domain                      domain.Domain
-	sharedRequestedTransactions *transactionrelay.SharedRequestedTransactions
+	sharedRequestedTransactions *flowcontext.SharedRequestedTransactions
 }
 
 func (m *mocTransactionsRelayContext) NetAdapter() *netadapter.NetAdapter {
@@ -35,7 +36,7 @@ func (m *mocTransactionsRelayContext) Domain() domain.Domain {
 	return m.domain
 }
 
-func (m *mocTransactionsRelayContext) SharedRequestedTransactions() *transactionrelay.SharedRequestedTransactions {
+func (m *mocTransactionsRelayContext) SharedRequestedTransactions() *flowcontext.SharedRequestedTransactions {
 	return m.sharedRequestedTransactions
 }
 
@@ -46,6 +47,10 @@ func (m *mocTransactionsRelayContext) EnqueueTransactionIDsForPropagation(transa
 func (m *mocTransactionsRelayContext) OnTransactionAddedToMempool() {
 }
 
+func (m *mocTransactionsRelayContext) IsIBDRunning() bool {
+	return false
+}
+
 // TestHandleRelayedTransactionsNotFound tests the flow of  HandleRelayedTransactions when the peer doesn't
 // have the requested transactions in the mempool.
 func TestHandleRelayedTransactionsNotFound(t *testing.T) {
@@ -60,7 +65,7 @@ func TestHandleRelayedTransactionsNotFound(t *testing.T) {
 		}
 		defer teardown(false)
 
-		sharedRequestedTransactions := transactionrelay.NewSharedRequestedTransactions()
+		sharedRequestedTransactions := flowcontext.NewSharedRequestedTransactions()
 		adapter, err := netadapter.NewNetAdapter(config.DefaultConfig())
 		if err != nil {
 			t.Fatalf("Failed to create a NetAdapter: %v", err)
@@ -153,7 +158,7 @@ func TestOnClosedIncomingRoute(t *testing.T) {
 		}
 		defer teardown(false)
 
-		sharedRequestedTransactions := transactionrelay.NewSharedRequestedTransactions()
+		sharedRequestedTransactions := flowcontext.NewSharedRequestedTransactions()
 		adapter, err := netadapter.NewNetAdapter(config.DefaultConfig())
 		if err != nil {
 			t.Fatalf("Failed to creat a NetAdapter : %v", err)

app/protocol/flows/v4/transactionrelay/handle_requested_transactions_test.go

@@ -1,10 +1,11 @@
 package transactionrelay_test
 
 import (
+	"github.com/kaspanet/kaspad/app/protocol/flowcontext"
+	"github.com/kaspanet/kaspad/app/protocol/flows/v4/transactionrelay"
 	"testing"
 
 	"github.com/kaspanet/kaspad/app/appmessage"
-	"github.com/kaspanet/kaspad/app/protocol/flows/transactionrelay"
 	"github.com/kaspanet/kaspad/domain"
 	"github.com/kaspanet/kaspad/domain/consensus"
 	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
@@ -31,7 +32,7 @@ func TestHandleRequestedTransactionsNotFound(t *testing.T) {
 		}
 		defer teardown(false)
 
-		sharedRequestedTransactions := transactionrelay.NewSharedRequestedTransactions()
+		sharedRequestedTransactions := flowcontext.NewSharedRequestedTransactions()
 		adapter, err := netadapter.NewNetAdapter(config.DefaultConfig())
 		if err != nil {
 			t.Fatalf("Failed to create a NetAdapter: %v", err)

app/protocol/flows/v5/addressexchange/receiveaddresses.go

@@ -0,0 +1,39 @@
+package addressexchange
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/app/protocol/common"
+	peerpkg "github.com/kaspanet/kaspad/app/protocol/peer"
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/infrastructure/network/addressmanager"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+)
+
+// ReceiveAddressesContext is the interface for the context needed for the ReceiveAddresses flow.
+type ReceiveAddressesContext interface {
+	AddressManager() *addressmanager.AddressManager
+}
+
+// ReceiveAddresses asks a peer for more addresses if needed.
+func ReceiveAddresses(context ReceiveAddressesContext, incomingRoute *router.Route, outgoingRoute *router.Route,
+	peer *peerpkg.Peer) error {
+
+	subnetworkID := peer.SubnetworkID()
+	msgGetAddresses := appmessage.NewMsgRequestAddresses(false, subnetworkID)
+	err := outgoingRoute.Enqueue(msgGetAddresses)
+	if err != nil {
+		return err
+	}
+
+	message, err := incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
+	if err != nil {
+		return err
+	}
+
+	msgAddresses := message.(*appmessage.MsgAddresses)
+	if len(msgAddresses.AddressList) > addressmanager.GetAddressesMax {
+		return protocolerrors.Errorf(true, "address count exceeded %d", addressmanager.GetAddressesMax)
+	}
+
+	return context.AddressManager().AddAddresses(msgAddresses.AddressList...)
+}

app/protocol/flows/v5/addressexchange/sendaddresses.go

@@ -0,0 +1,52 @@
+package addressexchange
+
+import (
+	"math/rand"
+
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/infrastructure/network/addressmanager"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+)
+
+// SendAddressesContext is the interface for the context needed for the SendAddresses flow.
+type SendAddressesContext interface {
+	AddressManager() *addressmanager.AddressManager
+}
+
+// SendAddresses sends addresses to a peer that requests it.
+func SendAddresses(context SendAddressesContext, incomingRoute *router.Route, outgoingRoute *router.Route) error {
+	for {
+		_, err := incomingRoute.Dequeue()
+		if err != nil {
+			return err
+		}
+
+		addresses := context.AddressManager().Addresses()
+		msgAddresses := appmessage.NewMsgAddresses(shuffleAddresses(addresses))
+
+		err = outgoingRoute.Enqueue(msgAddresses)
+		if err != nil {
+			return err
+		}
+	}
+}
+
+// shuffleAddresses randomizes the given addresses sent if there are more than the maximum allowed in one message.
+func shuffleAddresses(addresses []*appmessage.NetAddress) []*appmessage.NetAddress {
+	addressCount := len(addresses)
+
+	if addressCount < appmessage.MaxAddressesPerMsg {
+		return addresses
+	}
+
+	shuffleAddresses := make([]*appmessage.NetAddress, addressCount)
+	copy(shuffleAddresses, addresses)
+
+	rand.Shuffle(addressCount, func(i, j int) {
+		shuffleAddresses[i], shuffleAddresses[j] = shuffleAddresses[j], shuffleAddresses[i]
+	})
+
+	// Truncate it to the maximum size.
+	shuffleAddresses = shuffleAddresses[:appmessage.MaxAddressesPerMsg]
+	return shuffleAddresses
+}

app/protocol/flows/v5/blockrelay/batch_size_test.go

@@ -0,0 +1,16 @@
+package blockrelay
+
+import (
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+	"testing"
+)
+
+func TestIBDBatchSizeLessThanRouteCapacity(t *testing.T) {
+	// The `ibdBatchSize` constant must be equal at both syncer and syncee. Therefore, we do not want
+	// to set it to `router.DefaultMaxMessages` to avoid confusion and human errors.
+	// However, nonetheless we must enforce that it does not exceed `router.DefaultMaxMessages`
+	if ibdBatchSize >= router.DefaultMaxMessages {
+		t.Fatalf("IBD batch size (%d) must be smaller than router.DefaultMaxMessages (%d)",
+			ibdBatchSize, router.DefaultMaxMessages)
+	}
+}

app/protocol/flows/v5/blockrelay/block_locator.go

@@ -0,0 +1,33 @@
+package blockrelay
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/app/protocol/common"
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+)
+
+func (flow *handleRelayInvsFlow) sendGetBlockLocator(highHash *externalapi.DomainHash, limit uint32) error {
+	msgGetBlockLocator := appmessage.NewMsgRequestBlockLocator(highHash, limit)
+	return flow.outgoingRoute.Enqueue(msgGetBlockLocator)
+}
+
+func (flow *handleRelayInvsFlow) receiveBlockLocator() (blockLocatorHashes []*externalapi.DomainHash, err error) {
+	for {
+		message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
+		if err != nil {
+			return nil, err
+		}
+
+		switch message := message.(type) {
+		case *appmessage.MsgInvRelayBlock:
+			flow.invsQueue = append(flow.invsQueue, message)
+		case *appmessage.MsgBlockLocator:
+			return message.BlockLocatorHashes, nil
+		default:
+			return nil,
+				protocolerrors.Errorf(true, "received unexpected message type. "+
+					"expected: %s, got: %s", appmessage.CmdBlockLocator, message.Command())
+		}
+	}
+}

app/protocol/flows/v5/blockrelay/handle_ibd_block_locator.go

@@ -0,0 +1,86 @@
+package blockrelay
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/app/protocol/peer"
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/domain"
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+)
+
+// HandleIBDBlockLocatorContext is the interface for the context needed for the HandleIBDBlockLocator flow.
+type HandleIBDBlockLocatorContext interface {
+	Domain() domain.Domain
+}
+
+// HandleIBDBlockLocator listens to appmessage.MsgIBDBlockLocator messages and sends
+// the highest known block that's in the selected parent chain of `targetHash` to the
+// requesting peer.
+func HandleIBDBlockLocator(context HandleIBDBlockLocatorContext, incomingRoute *router.Route,
+	outgoingRoute *router.Route, peer *peer.Peer) error {
+
+	for {
+		message, err := incomingRoute.Dequeue()
+		if err != nil {
+			return err
+		}
+		ibdBlockLocatorMessage := message.(*appmessage.MsgIBDBlockLocator)
+
+		targetHash := ibdBlockLocatorMessage.TargetHash
+		log.Debugf("Received IBDBlockLocator from %s with targetHash %s", peer, targetHash)
+
+		blockInfo, err := context.Domain().Consensus().GetBlockInfo(targetHash)
+		if err != nil {
+			return err
+		}
+		if !blockInfo.Exists {
+			return protocolerrors.Errorf(true, "received IBDBlockLocator "+
+				"with an unknown targetHash %s", targetHash)
+		}
+
+		foundHighestHashInTheSelectedParentChainOfTargetHash := false
+		for _, blockLocatorHash := range ibdBlockLocatorMessage.BlockLocatorHashes {
+			blockInfo, err := context.Domain().Consensus().GetBlockInfo(blockLocatorHash)
+			if err != nil {
+				return err
+			}
+
+			// The IBD block locator is checking only existing blocks with bodies.
+			if !blockInfo.Exists || blockInfo.BlockStatus == externalapi.StatusHeaderOnly {
+				continue
+			}
+
+			isBlockLocatorHashInSelectedParentChainOfHighHash, err :=
+				context.Domain().Consensus().IsInSelectedParentChainOf(blockLocatorHash, targetHash)
+			if err != nil {
+				return err
+			}
+			if !isBlockLocatorHashInSelectedParentChainOfHighHash {
+				continue
+			}
+
+			foundHighestHashInTheSelectedParentChainOfTargetHash = true
+			log.Debugf("Found a known hash %s amongst peer %s's "+
+				"blockLocator that's in the selected parent chain of targetHash %s", blockLocatorHash, peer, targetHash)
+
+			ibdBlockLocatorHighestHashMessage := appmessage.NewMsgIBDBlockLocatorHighestHash(blockLocatorHash)
+			err = outgoingRoute.Enqueue(ibdBlockLocatorHighestHashMessage)
+			if err != nil {
+				return err
+			}
+			break
+		}
+
+		if !foundHighestHashInTheSelectedParentChainOfTargetHash {
+			log.Warnf("no hash was found in the blockLocator "+
+				"that was in the selected parent chain of targetHash %s", targetHash)
+
+			ibdBlockLocatorHighestHashNotFoundMessage := appmessage.NewMsgIBDBlockLocatorHighestHashNotFound()
+			err = outgoingRoute.Enqueue(ibdBlockLocatorHighestHashNotFoundMessage)
+			if err != nil {
+				return err
+			}
+		}
+	}
+}

app/protocol/flows/v5/blockrelay/handle_ibd_block_requests.go

@@ -0,0 +1,54 @@
+package blockrelay
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/domain"
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+	"github.com/pkg/errors"
+)
+
+// HandleIBDBlockRequestsContext is the interface for the context needed for the HandleIBDBlockRequests flow.
+type HandleIBDBlockRequestsContext interface {
+	Domain() domain.Domain
+}
+
+// HandleIBDBlockRequests listens to appmessage.MsgRequestRelayBlocks messages and sends
+// their corresponding blocks to the requesting peer.
+func HandleIBDBlockRequests(context HandleIBDBlockRequestsContext, incomingRoute *router.Route,
+	outgoingRoute *router.Route) error {
+
+	for {
+		message, err := incomingRoute.Dequeue()
+		if err != nil {
+			return err
+		}
+		msgRequestIBDBlocks := message.(*appmessage.MsgRequestIBDBlocks)
+		log.Debugf("Got request for %d ibd blocks", len(msgRequestIBDBlocks.Hashes))
+		for i, hash := range msgRequestIBDBlocks.Hashes {
+			// Fetch the block from the database.
+			blockInfo, err := context.Domain().Consensus().GetBlockInfo(hash)
+			if err != nil {
+				return err
+			}
+			if !blockInfo.Exists || blockInfo.BlockStatus == externalapi.StatusHeaderOnly {
+				return protocolerrors.Errorf(true, "block %s not found (v5)", hash)
+			}
+			block, err := context.Domain().Consensus().GetBlock(hash)
+			if err != nil {
+				return errors.Wrapf(err, "unable to fetch requested block hash %s", hash)
+			}
+
+			// TODO (Partial nodes): Convert block to partial block if needed
+
+			blockMessage := appmessage.DomainBlockToMsgBlock(block)
+			ibdBlockMessage := appmessage.NewMsgIBDBlock(blockMessage)
+			err = outgoingRoute.Enqueue(ibdBlockMessage)
+			if err != nil {
+				return err
+			}
+			log.Debugf("sent %d out of %d", i+1, len(msgRequestIBDBlocks.Hashes))
+		}
+	}
+}

app/protocol/flows/v5/blockrelay/handle_ibd_request_chain_block_locator.go

@@ -0,0 +1,85 @@
+package blockrelay
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/domain"
+	"github.com/kaspanet/kaspad/domain/consensus/model"
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+	"github.com/pkg/errors"
+)
+
+// RequestIBDChainBlockLocatorContext is the interface for the context needed for the HandleRequestBlockLocator flow.
+type RequestIBDChainBlockLocatorContext interface {
+	Domain() domain.Domain
+}
+
+type handleRequestIBDChainBlockLocatorFlow struct {
+	RequestIBDChainBlockLocatorContext
+	incomingRoute, outgoingRoute *router.Route
+}
+
+// HandleRequestIBDChainBlockLocator handles getBlockLocator messages
+func HandleRequestIBDChainBlockLocator(context RequestIBDChainBlockLocatorContext, incomingRoute *router.Route,
+	outgoingRoute *router.Route) error {
+
+	flow := &handleRequestIBDChainBlockLocatorFlow{
+		RequestIBDChainBlockLocatorContext: context,
+		incomingRoute:                      incomingRoute,
+		outgoingRoute:                      outgoingRoute,
+	}
+	return flow.start()
+}
+
+func (flow *handleRequestIBDChainBlockLocatorFlow) start() error {
+	for {
+		highHash, lowHash, err := flow.receiveRequestIBDChainBlockLocator()
+		if err != nil {
+			return err
+		}
+		log.Debugf("Received getIBDChainBlockLocator with highHash: %s, lowHash: %s", highHash, lowHash)
+
+		var locator externalapi.BlockLocator
+		if highHash == nil || lowHash == nil {
+			locator, err = flow.Domain().Consensus().CreateFullHeadersSelectedChainBlockLocator()
+		} else {
+			locator, err = flow.Domain().Consensus().CreateHeadersSelectedChainBlockLocator(lowHash, highHash)
+			if errors.Is(model.ErrBlockNotInSelectedParentChain, err) {
+				// The chain has been modified, signal it by sending an empty locator
+				locator, err = externalapi.BlockLocator{}, nil
+			}
+		}
+
+		if err != nil {
+			log.Debugf("Received error from CreateHeadersSelectedChainBlockLocator: %s", err)
+			return protocolerrors.Errorf(true, "couldn't build a block "+
+				"locator between %s and %s", lowHash, highHash)
+		}
+
+		err = flow.sendIBDChainBlockLocator(locator)
+		if err != nil {
+			return err
+		}
+	}
+}
+
+func (flow *handleRequestIBDChainBlockLocatorFlow) receiveRequestIBDChainBlockLocator() (highHash, lowHash *externalapi.DomainHash, err error) {
+
+	message, err := flow.incomingRoute.Dequeue()
+	if err != nil {
+		return nil, nil, err
+	}
+	msgGetBlockLocator := message.(*appmessage.MsgRequestIBDChainBlockLocator)
+
+	return msgGetBlockLocator.HighHash, msgGetBlockLocator.LowHash, nil
+}
+
+func (flow *handleRequestIBDChainBlockLocatorFlow) sendIBDChainBlockLocator(locator externalapi.BlockLocator) error {
+	msgIBDChainBlockLocator := appmessage.NewMsgIBDChainBlockLocator(locator)
+	err := flow.outgoingRoute.Enqueue(msgIBDChainBlockLocator)
+	if err != nil {
+		return err
+	}
+	return nil
+}

app/protocol/flows/v5/blockrelay/handle_pruning_point_and_its_anticone_requests.go

@@ -0,0 +1,158 @@
+package blockrelay
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	peerpkg "github.com/kaspanet/kaspad/app/protocol/peer"
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/domain"
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+	"github.com/kaspanet/kaspad/infrastructure/config"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+	"sync/atomic"
+)
+
+// PruningPointAndItsAnticoneRequestsContext is the interface for the context needed for the HandlePruningPointAndItsAnticoneRequests flow.
+type PruningPointAndItsAnticoneRequestsContext interface {
+	Domain() domain.Domain
+	Config() *config.Config
+}
+
+var isBusy uint32
+
+// HandlePruningPointAndItsAnticoneRequests listens to appmessage.MsgRequestPruningPointAndItsAnticone messages and sends
+// the pruning point and its anticone to the requesting peer.
+func HandlePruningPointAndItsAnticoneRequests(context PruningPointAndItsAnticoneRequestsContext, incomingRoute *router.Route,
+	outgoingRoute *router.Route, peer *peerpkg.Peer) error {
+
+	for {
+		err := func() error {
+			_, err := incomingRoute.Dequeue()
+			if err != nil {
+				return err
+			}
+
+			if !atomic.CompareAndSwapUint32(&isBusy, 0, 1) {
+				return protocolerrors.Errorf(false, "node is busy with other pruning point anticone requests")
+			}
+			defer atomic.StoreUint32(&isBusy, 0)
+
+			log.Debugf("Got request for pruning point and its anticone from %s", peer)
+
+			pruningPointHeaders, err := context.Domain().Consensus().PruningPointHeaders()
+			if err != nil {
+				return err
+			}
+
+			msgPruningPointHeaders := make([]*appmessage.MsgBlockHeader, len(pruningPointHeaders))
+			for i, header := range pruningPointHeaders {
+				msgPruningPointHeaders[i] = appmessage.DomainBlockHeaderToBlockHeader(header)
+			}
+
+			err = outgoingRoute.Enqueue(appmessage.NewMsgPruningPoints(msgPruningPointHeaders))
+			if err != nil {
+				return err
+			}
+
+			pointAndItsAnticone, err := context.Domain().Consensus().PruningPointAndItsAnticone()
+			if err != nil {
+				return err
+			}
+
+			windowSize := context.Config().NetParams().DifficultyAdjustmentWindowSize
+			daaWindowBlocks := make([]*externalapi.TrustedDataDataDAAHeader, 0, windowSize)
+			daaWindowHashesToIndex := make(map[externalapi.DomainHash]int, windowSize)
+			trustedDataDAABlockIndexes := make(map[externalapi.DomainHash][]uint64)
+
+			ghostdagData := make([]*externalapi.BlockGHOSTDAGDataHashPair, 0)
+			ghostdagDataHashToIndex := make(map[externalapi.DomainHash]int)
+			trustedDataGHOSTDAGDataIndexes := make(map[externalapi.DomainHash][]uint64)
+			for _, blockHash := range pointAndItsAnticone {
+				blockDAAWindowHashes, err := context.Domain().Consensus().BlockDAAWindowHashes(blockHash)
+				if err != nil {
+					return err
+				}
+
+				trustedDataDAABlockIndexes[*blockHash] = make([]uint64, 0, windowSize)
+				for i, daaBlockHash := range blockDAAWindowHashes {
+					index, exists := daaWindowHashesToIndex[*daaBlockHash]
+					if !exists {
+						trustedDataDataDAAHeader, err := context.Domain().Consensus().TrustedDataDataDAAHeader(blockHash, daaBlockHash, uint64(i))
+						if err != nil {
+							return err
+						}
+						daaWindowBlocks = append(daaWindowBlocks, trustedDataDataDAAHeader)
+						index = len(daaWindowBlocks) - 1
+						daaWindowHashesToIndex[*daaBlockHash] = index
+					}
+
+					trustedDataDAABlockIndexes[*blockHash] = append(trustedDataDAABlockIndexes[*blockHash], uint64(index))
+				}
+
+				ghostdagDataBlockHashes, err := context.Domain().Consensus().TrustedBlockAssociatedGHOSTDAGDataBlockHashes(blockHash)
+				if err != nil {
+					return err
+				}
+
+				trustedDataGHOSTDAGDataIndexes[*blockHash] = make([]uint64, 0, context.Config().NetParams().K)
+				for _, ghostdagDataBlockHash := range ghostdagDataBlockHashes {
+					index, exists := ghostdagDataHashToIndex[*ghostdagDataBlockHash]
+					if !exists {
+						data, err := context.Domain().Consensus().TrustedGHOSTDAGData(ghostdagDataBlockHash)
+						if err != nil {
+							return err
+						}
+						ghostdagData = append(ghostdagData, &externalapi.BlockGHOSTDAGDataHashPair{
+							Hash:         ghostdagDataBlockHash,
+							GHOSTDAGData: data,
+						})
+						index = len(ghostdagData) - 1
+						ghostdagDataHashToIndex[*ghostdagDataBlockHash] = index
+					}
+
+					trustedDataGHOSTDAGDataIndexes[*blockHash] = append(trustedDataGHOSTDAGDataIndexes[*blockHash], uint64(index))
+				}
+			}
+
+			err = outgoingRoute.Enqueue(appmessage.DomainTrustedDataToTrustedData(daaWindowBlocks, ghostdagData))
+			if err != nil {
+				return err
+			}
+
+			for i, blockHash := range pointAndItsAnticone {
+				block, err := context.Domain().Consensus().GetBlock(blockHash)
+				if err != nil {
+					return err
+				}
+
+				err = outgoingRoute.Enqueue(appmessage.DomainBlockWithTrustedDataToBlockWithTrustedDataV4(block, trustedDataDAABlockIndexes[*blockHash], trustedDataGHOSTDAGDataIndexes[*blockHash]))
+				if err != nil {
+					return err
+				}
+
+				if (i+1)%ibdBatchSize == 0 {
+					// No timeout here, as we don't care if the syncee takes its time computing,
+					// since it only blocks this dedicated flow
+					message, err := incomingRoute.Dequeue()
+					if err != nil {
+						return err
+					}
+					if _, ok := message.(*appmessage.MsgRequestNextPruningPointAndItsAnticoneBlocks); !ok {
+						return protocolerrors.Errorf(true, "received unexpected message type. "+
+							"expected: %s, got: %s", appmessage.CmdRequestNextPruningPointAndItsAnticoneBlocks, message.Command())
+					}
+				}
+			}
+
+			err = outgoingRoute.Enqueue(appmessage.NewMsgDoneBlocksWithTrustedData())
+			if err != nil {
+				return err
+			}
+
+			log.Debugf("Sent pruning point and its anticone to %s", peer)
+			return nil
+		}()
+		if err != nil {
+			return err
+		}
+	}
+}

app/protocol/flows/v5/blockrelay/handle_pruning_point_proof_requests.go

@@ -0,0 +1,40 @@
+package blockrelay
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	peerpkg "github.com/kaspanet/kaspad/app/protocol/peer"
+	"github.com/kaspanet/kaspad/domain"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+)
+
+// PruningPointProofRequestsContext is the interface for the context needed for the HandlePruningPointProofRequests flow.
+type PruningPointProofRequestsContext interface {
+	Domain() domain.Domain
+}
+
+// HandlePruningPointProofRequests listens to appmessage.MsgRequestPruningPointProof messages and sends
+// the pruning point proof to the requesting peer.
+func HandlePruningPointProofRequests(context PruningPointProofRequestsContext, incomingRoute *router.Route,
+	outgoingRoute *router.Route, peer *peerpkg.Peer) error {
+
+	for {
+		_, err := incomingRoute.Dequeue()
+		if err != nil {
+			return err
+		}
+
+		log.Debugf("Got request for pruning point proof from %s", peer)
+
+		pruningPointProof, err := context.Domain().Consensus().BuildPruningPointProof()
+		if err != nil {
+			return err
+		}
+		pruningPointProofMessage := appmessage.DomainPruningPointProofToMsgPruningPointProof(pruningPointProof)
+		err = outgoingRoute.Enqueue(pruningPointProofMessage)
+		if err != nil {
+			return err
+		}
+
+		log.Debugf("Sent pruning point proof to %s", peer)
+	}
+}

app/protocol/flows/v5/blockrelay/handle_relay_block_requests.go

@@ -0,0 +1,53 @@
+package blockrelay
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	peerpkg "github.com/kaspanet/kaspad/app/protocol/peer"
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/domain"
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+	"github.com/pkg/errors"
+)
+
+// RelayBlockRequestsContext is the interface for the context needed for the HandleRelayBlockRequests flow.
+type RelayBlockRequestsContext interface {
+	Domain() domain.Domain
+}
+
+// HandleRelayBlockRequests listens to appmessage.MsgRequestRelayBlocks messages and sends
+// their corresponding blocks to the requesting peer.
+func HandleRelayBlockRequests(context RelayBlockRequestsContext, incomingRoute *router.Route,
+	outgoingRoute *router.Route, peer *peerpkg.Peer) error {
+
+	for {
+		message, err := incomingRoute.Dequeue()
+		if err != nil {
+			return err
+		}
+		getRelayBlocksMessage := message.(*appmessage.MsgRequestRelayBlocks)
+		log.Debugf("Got request for relay blocks with hashes %s", getRelayBlocksMessage.Hashes)
+		for _, hash := range getRelayBlocksMessage.Hashes {
+			// Fetch the block from the database.
+			blockInfo, err := context.Domain().Consensus().GetBlockInfo(hash)
+			if err != nil {
+				return err
+			}
+			if !blockInfo.Exists || blockInfo.BlockStatus == externalapi.StatusHeaderOnly {
+				return protocolerrors.Errorf(true, "block %s not found", hash)
+			}
+			block, err := context.Domain().Consensus().GetBlock(hash)
+			if err != nil {
+				return errors.Wrapf(err, "unable to fetch requested block hash %s", hash)
+			}
+
+			// TODO (Partial nodes): Convert block to partial block if needed
+
+			err = outgoingRoute.Enqueue(appmessage.DomainBlockToMsgBlock(block))
+			if err != nil {
+				return err
+			}
+			log.Debugf("Relayed block with hash %s", hash)
+		}
+	}
+}

app/protocol/flows/v5/blockrelay/handle_relay_invs.go

@@ -0,0 +1,416 @@
+package blockrelay
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/app/protocol/common"
+	"github.com/kaspanet/kaspad/app/protocol/flowcontext"
+	peerpkg "github.com/kaspanet/kaspad/app/protocol/peer"
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/domain"
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+	"github.com/kaspanet/kaspad/domain/consensus/ruleerrors"
+	"github.com/kaspanet/kaspad/domain/consensus/utils/consensushashing"
+	"github.com/kaspanet/kaspad/domain/consensus/utils/hashset"
+	"github.com/kaspanet/kaspad/infrastructure/config"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+	"github.com/pkg/errors"
+)
+
+// orphanResolutionRange is the maximum amount of blockLocator hashes
+// to search for known blocks. See isBlockInOrphanResolutionRange for
+// further details
+var orphanResolutionRange uint32 = 5
+
+// RelayInvsContext is the interface for the context needed for the HandleRelayInvs flow.
+type RelayInvsContext interface {
+	Domain() domain.Domain
+	Config() *config.Config
+	OnNewBlock(block *externalapi.DomainBlock, virtualChangeSet *externalapi.VirtualChangeSet) error
+	OnVirtualChange(virtualChangeSet *externalapi.VirtualChangeSet) error
+	OnPruningPointUTXOSetOverride() error
+	SharedRequestedBlocks() *flowcontext.SharedRequestedBlocks
+	Broadcast(message appmessage.Message) error
+	AddOrphan(orphanBlock *externalapi.DomainBlock)
+	GetOrphanRoots(orphanHash *externalapi.DomainHash) ([]*externalapi.DomainHash, bool, error)
+	IsOrphan(blockHash *externalapi.DomainHash) bool
+	IsIBDRunning() bool
+	IsRecoverableError(err error) bool
+}
+
+type handleRelayInvsFlow struct {
+	RelayInvsContext
+	incomingRoute, outgoingRoute *router.Route
+	peer                         *peerpkg.Peer
+	invsQueue                    []*appmessage.MsgInvRelayBlock
+}
+
+// HandleRelayInvs listens to appmessage.MsgInvRelayBlock messages, requests their corresponding blocks if they
+// are missing, adds them to the DAG and propagates them to the rest of the network.
+func HandleRelayInvs(context RelayInvsContext, incomingRoute *router.Route, outgoingRoute *router.Route,
+	peer *peerpkg.Peer) error {
+
+	flow := &handleRelayInvsFlow{
+		RelayInvsContext: context,
+		incomingRoute:    incomingRoute,
+		outgoingRoute:    outgoingRoute,
+		peer:             peer,
+		invsQueue:        make([]*appmessage.MsgInvRelayBlock, 0),
+	}
+	err := flow.start()
+	// Currently, HandleRelayInvs flow is the only place where IBD is triggered, so the channel can be closed now
+	close(peer.IBDRequestChannel())
+	return err
+}
+
+func (flow *handleRelayInvsFlow) start() error {
+	for {
+		log.Debugf("Waiting for inv")
+		inv, err := flow.readInv()
+		if err != nil {
+			return err
+		}
+
+		log.Debugf("Got relay inv for block %s", inv.Hash)
+
+		blockInfo, err := flow.Domain().Consensus().GetBlockInfo(inv.Hash)
+		if err != nil {
+			return err
+		}
+		if blockInfo.Exists && blockInfo.BlockStatus != externalapi.StatusHeaderOnly {
+			if blockInfo.BlockStatus == externalapi.StatusInvalid {
+				return protocolerrors.Errorf(true, "sent inv of an invalid block %s",
+					inv.Hash)
+			}
+			log.Debugf("Block %s already exists. continuing...", inv.Hash)
+			continue
+		}
+
+		isGenesisVirtualSelectedParent, err := flow.isGenesisVirtualSelectedParent()
+		if err != nil {
+			return err
+		}
+
+		if flow.IsOrphan(inv.Hash) {
+			if flow.Config().NetParams().DisallowDirectBlocksOnTopOfGenesis && !flow.Config().AllowSubmitBlockWhenNotSynced && isGenesisVirtualSelectedParent {
+				log.Infof("Cannot process orphan %s for a node with only the genesis block. The node needs to IBD "+
+					"to the recent pruning point before normal operation can resume.", inv.Hash)
+				continue
+			}
+
+			log.Debugf("Block %s is a known orphan. Requesting its missing ancestors", inv.Hash)
+			err := flow.AddOrphanRootsToQueue(inv.Hash)
+			if err != nil {
+				return err
+			}
+			continue
+		}
+
+		// Block relay is disabled during IBD
+		if flow.IsIBDRunning() {
+			log.Debugf("Got block %s while in IBD. continuing...", inv.Hash)
+			continue
+		}
+
+		log.Debugf("Requesting block %s", inv.Hash)
+		block, exists, err := flow.requestBlock(inv.Hash)
+		if err != nil {
+			return err
+		}
+		if exists {
+			log.Debugf("Aborting requesting block %s because it already exists", inv.Hash)
+			continue
+		}
+
+		err = flow.banIfBlockIsHeaderOnly(block)
+		if err != nil {
+			return err
+		}
+
+		if flow.Config().NetParams().DisallowDirectBlocksOnTopOfGenesis && !flow.Config().AllowSubmitBlockWhenNotSynced && !flow.Config().Devnet && flow.isChildOfGenesis(block) {
+			log.Infof("Cannot process %s because it's a direct child of genesis.", consensushashing.BlockHash(block))
+			continue
+		}
+
+		log.Debugf("Processing block %s", inv.Hash)
+		oldVirtualInfo, err := flow.Domain().Consensus().GetVirtualInfo()
+		if err != nil {
+			return err
+		}
+		missingParents, virtualChangeSet, err := flow.processBlock(block)
+		if err != nil {
+			if errors.Is(err, ruleerrors.ErrPrunedBlock) {
+				log.Infof("Ignoring pruned block %s", inv.Hash)
+				continue
+			}
+
+			if errors.Is(err, ruleerrors.ErrDuplicateBlock) {
+				log.Infof("Ignoring duplicate block %s", inv.Hash)
+				continue
+			}
+			return err
+		}
+		if len(missingParents) > 0 {
+			log.Debugf("Block %s is orphan and has missing parents: %s", inv.Hash, missingParents)
+			err := flow.processOrphan(block)
+			if err != nil {
+				return err
+			}
+			continue
+		}
+
+		oldVirtualParents := hashset.New()
+		for _, parent := range oldVirtualInfo.ParentHashes {
+			oldVirtualParents.Add(parent)
+		}
+
+		newVirtualInfo, err := flow.Domain().Consensus().GetVirtualInfo()
+		if err != nil {
+			return err
+		}
+
+		for _, parent := range newVirtualInfo.ParentHashes {
+			if oldVirtualParents.Contains(parent) {
+				continue
+			}
+
+			block, err := flow.Domain().Consensus().GetBlock(parent)
+			if err != nil {
+				return err
+			}
+			blockHash := consensushashing.BlockHash(block)
+			log.Debugf("Relaying block %s", blockHash)
+			err = flow.relayBlock(block)
+			if err != nil {
+				return err
+			}
+		}
+
+		log.Infof("Accepted block %s via relay", inv.Hash)
+		err = flow.OnNewBlock(block, virtualChangeSet)
+		if err != nil {
+			return err
+		}
+	}
+}
+
+func (flow *handleRelayInvsFlow) banIfBlockIsHeaderOnly(block *externalapi.DomainBlock) error {
+	if len(block.Transactions) == 0 {
+		return protocolerrors.Errorf(true, "sent header of %s block where expected block with body",
+			consensushashing.BlockHash(block))
+	}
+
+	return nil
+}
+
+func (flow *handleRelayInvsFlow) readInv() (*appmessage.MsgInvRelayBlock, error) {
+	if len(flow.invsQueue) > 0 {
+		var inv *appmessage.MsgInvRelayBlock
+		inv, flow.invsQueue = flow.invsQueue[0], flow.invsQueue[1:]
+		return inv, nil
+	}
+
+	msg, err := flow.incomingRoute.Dequeue()
+	if err != nil {
+		return nil, err
+	}
+
+	inv, ok := msg.(*appmessage.MsgInvRelayBlock)
+	if !ok {
+		return nil, protocolerrors.Errorf(true, "unexpected %s message in the block relay handleRelayInvsFlow while "+
+			"expecting an inv message", msg.Command())
+	}
+	return inv, nil
+}
+
+func (flow *handleRelayInvsFlow) requestBlock(requestHash *externalapi.DomainHash) (*externalapi.DomainBlock, bool, error) {
+	exists := flow.SharedRequestedBlocks().AddIfNotExists(requestHash)
+	if exists {
+		return nil, true, nil
+	}
+
+	// In case the function returns earlier than expected, we want to make sure flow.SharedRequestedBlocks() is
+	// clean from any pending blocks.
+	defer flow.SharedRequestedBlocks().Remove(requestHash)
+
+	getRelayBlocksMsg := appmessage.NewMsgRequestRelayBlocks([]*externalapi.DomainHash{requestHash})
+	err := flow.outgoingRoute.Enqueue(getRelayBlocksMsg)
+	if err != nil {
+		return nil, false, err
+	}
+
+	msgBlock, err := flow.readMsgBlock()
+	if err != nil {
+		return nil, false, err
+	}
+
+	block := appmessage.MsgBlockToDomainBlock(msgBlock)
+	blockHash := consensushashing.BlockHash(block)
+	if !blockHash.Equal(requestHash) {
+		return nil, false, protocolerrors.Errorf(true, "got unrequested block %s", blockHash)
+	}
+
+	return block, false, nil
+}
+
+// readMsgBlock returns the next msgBlock in msgChan, and populates invsQueue with any inv messages that meanwhile arrive.
+//
+// Note: this function assumes msgChan can contain only appmessage.MsgInvRelayBlock and appmessage.MsgBlock messages.
+func (flow *handleRelayInvsFlow) readMsgBlock() (msgBlock *appmessage.MsgBlock, err error) {
+	for {
+		message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
+		if err != nil {
+			return nil, err
+		}
+
+		switch message := message.(type) {
+		case *appmessage.MsgInvRelayBlock:
+			flow.invsQueue = append(flow.invsQueue, message)
+		case *appmessage.MsgBlock:
+			return message, nil
+		default:
+			return nil, errors.Errorf("unexpected message %s", message.Command())
+		}
+	}
+}
+
+func (flow *handleRelayInvsFlow) processBlock(block *externalapi.DomainBlock) ([]*externalapi.DomainHash, *externalapi.VirtualChangeSet, error) {
+	blockHash := consensushashing.BlockHash(block)
+	virtualChangeSet, err := flow.Domain().Consensus().ValidateAndInsertBlock(block, true)
+	if err != nil {
+		if !errors.As(err, &ruleerrors.RuleError{}) {
+			return nil, nil, errors.Wrapf(err, "failed to process block %s", blockHash)
+		}
+
+		missingParentsError := &ruleerrors.ErrMissingParents{}
+		if errors.As(err, missingParentsError) {
+			return missingParentsError.MissingParentHashes, nil, nil
+		}
+		// A duplicate block should not appear to the user as a warning and is already reported in the calling function
+		if !errors.Is(err, ruleerrors.ErrDuplicateBlock) {
+			log.Warnf("Rejected block %s from %s: %s", blockHash, flow.peer, err)
+		}
+		return nil, nil, protocolerrors.Wrapf(true, err, "got invalid block %s from relay", blockHash)
+	}
+	return nil, virtualChangeSet, nil
+}
+
+func (flow *handleRelayInvsFlow) relayBlock(block *externalapi.DomainBlock) error {
+	blockHash := consensushashing.BlockHash(block)
+	return flow.Broadcast(appmessage.NewMsgInvBlock(blockHash))
+}
+
+func (flow *handleRelayInvsFlow) processOrphan(block *externalapi.DomainBlock) error {
+	blockHash := consensushashing.BlockHash(block)
+
+	// Return if the block has been orphaned from elsewhere already
+	if flow.IsOrphan(blockHash) {
+		log.Debugf("Skipping orphan processing for block %s because it is already an orphan", blockHash)
+		return nil
+	}
+
+	// Add the block to the orphan set if it's within orphan resolution range
+	isBlockInOrphanResolutionRange, err := flow.isBlockInOrphanResolutionRange(blockHash)
+	if err != nil {
+		return err
+	}
+	if isBlockInOrphanResolutionRange {
+		if flow.Config().NetParams().DisallowDirectBlocksOnTopOfGenesis && !flow.Config().AllowSubmitBlockWhenNotSynced {
+			isGenesisVirtualSelectedParent, err := flow.isGenesisVirtualSelectedParent()
+			if err != nil {
+				return err
+			}
+
+			if isGenesisVirtualSelectedParent {
+				log.Infof("Cannot process orphan %s for a node with only the genesis block. The node needs to IBD "+
+					"to the recent pruning point before normal operation can resume.", blockHash)
+				return nil
+			}
+		}
+
+		log.Debugf("Block %s is within orphan resolution range. "+
+			"Adding it to the orphan set", blockHash)
+		flow.AddOrphan(block)
+		log.Debugf("Requesting block %s missing ancestors", blockHash)
+		return flow.AddOrphanRootsToQueue(blockHash)
+	}
+
+	// Start IBD unless we already are in IBD
+	log.Debugf("Block %s is out of orphan resolution range. "+
+		"Attempting to start IBD against it.", blockHash)
+
+	// Send the block to IBD flow via the IBDRequestChannel.
+	// Note that this is a non-blocking send, since if IBD is already running, there is no need to trigger it
+	select {
+	case flow.peer.IBDRequestChannel() <- block:
+	default:
+	}
+	return nil
+}
+
+func (flow *handleRelayInvsFlow) isGenesisVirtualSelectedParent() (bool, error) {
+	virtualSelectedParent, err := flow.Domain().Consensus().GetVirtualSelectedParent()
+	if err != nil {
+		return false, err
+	}
+
+	return virtualSelectedParent.Equal(flow.Config().NetParams().GenesisHash), nil
+}
+
+func (flow *handleRelayInvsFlow) isChildOfGenesis(block *externalapi.DomainBlock) bool {
+	parents := block.Header.DirectParents()
+	return len(parents) == 1 && parents[0].Equal(flow.Config().NetParams().GenesisHash)
+}
+
+// isBlockInOrphanResolutionRange finds out whether the given blockHash should be
+// retrieved via the unorphaning mechanism or via IBD. This method sends a
+// getBlockLocator request to the peer with a limit of orphanResolutionRange.
+// In the response, if we know none of the hashes, we should retrieve the given
+// blockHash via IBD. Otherwise, via unorphaning.
+func (flow *handleRelayInvsFlow) isBlockInOrphanResolutionRange(blockHash *externalapi.DomainHash) (bool, error) {
+	err := flow.sendGetBlockLocator(blockHash, orphanResolutionRange)
+	if err != nil {
+		return false, err
+	}
+
+	blockLocatorHashes, err := flow.receiveBlockLocator()
+	if err != nil {
+		return false, err
+	}
+	for _, blockLocatorHash := range blockLocatorHashes {
+		blockInfo, err := flow.Domain().Consensus().GetBlockInfo(blockLocatorHash)
+		if err != nil {
+			return false, err
+		}
+		if blockInfo.Exists && blockInfo.BlockStatus != externalapi.StatusHeaderOnly {
+			return true, nil
+		}
+	}
+	return false, nil
+}
+
+func (flow *handleRelayInvsFlow) AddOrphanRootsToQueue(orphan *externalapi.DomainHash) error {
+	orphanRoots, orphanExists, err := flow.GetOrphanRoots(orphan)
+	if err != nil {
+		return err
+	}
+
+	if !orphanExists {
+		log.Infof("Orphan block %s was missing from the orphan pool while requesting for its roots. This "+
+			"probably happened because it was randomly evicted immediately after it was added.", orphan)
+	}
+
+	if len(orphanRoots) == 0 {
+		// In some rare cases we get here when there are no orphan roots already
+		return nil
+	}
+	log.Infof("Block %s has %d missing ancestors. Adding them to the invs queue...", orphan, len(orphanRoots))
+
+	invMessages := make([]*appmessage.MsgInvRelayBlock, len(orphanRoots))
+	for i, root := range orphanRoots {
+		log.Debugf("Adding block %s missing ancestor %s to the invs queue", orphan, root)
+		invMessages[i] = appmessage.NewMsgInvBlock(root)
+	}
+
+	flow.invsQueue = append(invMessages, flow.invsQueue...)
+	return nil
+}

app/protocol/flows/v5/blockrelay/handle_request_anticone.go

@@ -0,0 +1,95 @@
+package blockrelay
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/app/protocol/peer"
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/domain"
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+	"github.com/kaspanet/kaspad/infrastructure/config"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+	"sort"
+)
+
+// RequestAnticoneContext is the interface for the context needed for the HandleRequestHeaders flow.
+type RequestAnticoneContext interface {
+	Domain() domain.Domain
+	Config() *config.Config
+}
+
+type handleRequestAnticoneFlow struct {
+	RequestAnticoneContext
+	incomingRoute, outgoingRoute *router.Route
+	peer                         *peer.Peer
+}
+
+// HandleRequestAnticone handles RequestAnticone messages
+func HandleRequestAnticone(context RequestAnticoneContext, incomingRoute *router.Route,
+	outgoingRoute *router.Route, peer *peer.Peer) error {
+
+	flow := &handleRequestAnticoneFlow{
+		RequestAnticoneContext: context,
+		incomingRoute:          incomingRoute,
+		outgoingRoute:          outgoingRoute,
+		peer:                   peer,
+	}
+	return flow.start()
+}
+
+func (flow *handleRequestAnticoneFlow) start() error {
+	for {
+		blockHash, contextHash, err := receiveRequestAnticone(flow.incomingRoute)
+		if err != nil {
+			return err
+		}
+		log.Debugf("Received requestAnticone with blockHash: %s, contextHash: %s", blockHash, contextHash)
+		log.Debugf("Getting past(%s) cap anticone(%s) for peer %s", contextHash, blockHash, flow.peer)
+
+		// GetAnticone is expected to be called by the syncee for getting the anticone of the header selected tip
+		// intersected by past of relayed block, and is thus expected to be bounded by mergeset limit since
+		// we relay blocks only if they enter virtual's mergeset. We add 2 for a small margin error.
+		blockHashes, err := flow.Domain().Consensus().GetAnticone(blockHash, contextHash,
+			flow.Config().ActiveNetParams.MergeSetSizeLimit+2)
+		if err != nil {
+			return protocolerrors.Wrap(true, err, "Failed querying anticone")
+		}
+		log.Debugf("Got %d header hashes in past(%s) cap anticone(%s)", len(blockHashes), contextHash, blockHash)
+
+		blockHeaders := make([]*appmessage.MsgBlockHeader, len(blockHashes))
+		for i, blockHash := range blockHashes {
+			blockHeader, err := flow.Domain().Consensus().GetBlockHeader(blockHash)
+			if err != nil {
+				return err
+			}
+			blockHeaders[i] = appmessage.DomainBlockHeaderToBlockHeader(blockHeader)
+		}
+
+		// We sort the headers in bottom-up topological order before sending
+		sort.Slice(blockHeaders, func(i, j int) bool {
+			return blockHeaders[i].BlueWork.Cmp(blockHeaders[j].BlueWork) < 0
+		})
+
+		blockHeadersMessage := appmessage.NewBlockHeadersMessage(blockHeaders)
+		err = flow.outgoingRoute.Enqueue(blockHeadersMessage)
+		if err != nil {
+			return err
+		}
+
+		err = flow.outgoingRoute.Enqueue(appmessage.NewMsgDoneHeaders())
+		if err != nil {
+			return err
+		}
+	}
+}
+
+func receiveRequestAnticone(incomingRoute *router.Route) (blockHash *externalapi.DomainHash,
+	contextHash *externalapi.DomainHash, err error) {
+
+	message, err := incomingRoute.Dequeue()
+	if err != nil {
+		return nil, nil, err
+	}
+	msgRequestAnticone := message.(*appmessage.MsgRequestAnticone)
+
+	return msgRequestAnticone.BlockHash, msgRequestAnticone.ContextHash, nil
+}

app/protocol/flows/v5/blockrelay/handle_request_block_locator.go

@@ -0,0 +1,75 @@
+package blockrelay
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/domain"
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+)
+
+// RequestBlockLocatorContext is the interface for the context needed for the HandleRequestBlockLocator flow.
+type RequestBlockLocatorContext interface {
+	Domain() domain.Domain
+}
+
+type handleRequestBlockLocatorFlow struct {
+	RequestBlockLocatorContext
+	incomingRoute, outgoingRoute *router.Route
+}
+
+// HandleRequestBlockLocator handles getBlockLocator messages
+func HandleRequestBlockLocator(context RequestBlockLocatorContext, incomingRoute *router.Route,
+	outgoingRoute *router.Route) error {
+
+	flow := &handleRequestBlockLocatorFlow{
+		RequestBlockLocatorContext: context,
+		incomingRoute:              incomingRoute,
+		outgoingRoute:              outgoingRoute,
+	}
+	return flow.start()
+}
+
+func (flow *handleRequestBlockLocatorFlow) start() error {
+	for {
+		highHash, limit, err := flow.receiveGetBlockLocator()
+		if err != nil {
+			return err
+		}
+		log.Debugf("Received getBlockLocator with highHash: %s, limit: %d", highHash, limit)
+
+		locator, err := flow.Domain().Consensus().CreateBlockLocatorFromPruningPoint(highHash, limit)
+		if err != nil || len(locator) == 0 {
+			if err != nil {
+				log.Debugf("Received error from CreateBlockLocatorFromPruningPoint: %s", err)
+			}
+			return protocolerrors.Errorf(true, "couldn't build a block "+
+				"locator between the pruning point and %s", highHash)
+		}
+
+		err = flow.sendBlockLocator(locator)
+		if err != nil {
+			return err
+		}
+	}
+}
+
+func (flow *handleRequestBlockLocatorFlow) receiveGetBlockLocator() (highHash *externalapi.DomainHash, limit uint32, err error) {
+
+	message, err := flow.incomingRoute.Dequeue()
+	if err != nil {
+		return nil, 0, err
+	}
+	msgGetBlockLocator := message.(*appmessage.MsgRequestBlockLocator)
+
+	return msgGetBlockLocator.HighHash, msgGetBlockLocator.Limit, nil
+}
+
+func (flow *handleRequestBlockLocatorFlow) sendBlockLocator(locator externalapi.BlockLocator) error {
+	msgBlockLocator := appmessage.NewMsgBlockLocator(locator)
+	err := flow.outgoingRoute.Enqueue(msgBlockLocator)
+	if err != nil {
+		return err
+	}
+	return nil
+}

app/protocol/flows/v5/blockrelay/handle_request_headers.go

@@ -0,0 +1,116 @@
+package blockrelay
+
+import (
+	"github.com/kaspanet/kaspad/app/protocol/peer"
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/domain"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+)
+
+// This constant must be equal at both syncer and syncee. Therefore, never (!!) change this constant unless a new p2p
+// version is introduced. See `TestIBDBatchSizeLessThanRouteCapacity` as well.
+const ibdBatchSize = 99
+
+// RequestHeadersContext is the interface for the context needed for the HandleRequestHeaders flow.
+type RequestHeadersContext interface {
+	Domain() domain.Domain
+}
+
+type handleRequestHeadersFlow struct {
+	RequestHeadersContext
+	incomingRoute, outgoingRoute *router.Route
+	peer                         *peer.Peer
+}
+
+// HandleRequestHeaders handles RequestHeaders messages
+func HandleRequestHeaders(context RequestHeadersContext, incomingRoute *router.Route,
+	outgoingRoute *router.Route, peer *peer.Peer) error {
+
+	flow := &handleRequestHeadersFlow{
+		RequestHeadersContext: context,
+		incomingRoute:         incomingRoute,
+		outgoingRoute:         outgoingRoute,
+		peer:                  peer,
+	}
+	return flow.start()
+}
+
+func (flow *handleRequestHeadersFlow) start() error {
+	for {
+		lowHash, highHash, err := receiveRequestHeaders(flow.incomingRoute)
+		if err != nil {
+			return err
+		}
+		log.Debugf("Received requestHeaders with lowHash: %s, highHash: %s", lowHash, highHash)
+
+		isLowSelectedAncestorOfHigh, err := flow.Domain().Consensus().IsInSelectedParentChainOf(lowHash, highHash)
+		if err != nil {
+			return err
+		}
+		if !isLowSelectedAncestorOfHigh {
+			return protocolerrors.Errorf(true, "Expected %s to be on the selected chain of %s",
+				lowHash, highHash)
+		}
+
+		for !lowHash.Equal(highHash) {
+			log.Debugf("Getting block headers between %s and %s to %s", lowHash, highHash, flow.peer)
+
+			// GetHashesBetween is a relatively heavy operation so we limit it
+			// in order to avoid locking the consensus for too long
+			// maxBlocks MUST be >= MergeSetSizeLimit + 1
+			const maxBlocks = 1 << 10
+			blockHashes, _, err := flow.Domain().Consensus().GetHashesBetween(lowHash, highHash, maxBlocks)
+			if err != nil {
+				return err
+			}
+			log.Debugf("Got %d header hashes above lowHash %s", len(blockHashes), lowHash)
+
+			blockHeaders := make([]*appmessage.MsgBlockHeader, len(blockHashes))
+			for i, blockHash := range blockHashes {
+				blockHeader, err := flow.Domain().Consensus().GetBlockHeader(blockHash)
+				if err != nil {
+					return err
+				}
+				blockHeaders[i] = appmessage.DomainBlockHeaderToBlockHeader(blockHeader)
+			}
+
+			blockHeadersMessage := appmessage.NewBlockHeadersMessage(blockHeaders)
+			err = flow.outgoingRoute.Enqueue(blockHeadersMessage)
+			if err != nil {
+				return err
+			}
+
+			message, err := flow.incomingRoute.Dequeue()
+			if err != nil {
+				return err
+			}
+			if _, ok := message.(*appmessage.MsgRequestNextHeaders); !ok {
+				return protocolerrors.Errorf(true, "received unexpected message type. "+
+					"expected: %s, got: %s", appmessage.CmdRequestNextHeaders, message.Command())
+			}
+
+			// The next lowHash is the last element in blockHashes
+			lowHash = blockHashes[len(blockHashes)-1]
+		}
+
+		err = flow.outgoingRoute.Enqueue(appmessage.NewMsgDoneHeaders())
+		if err != nil {
+			return err
+		}
+	}
+}
+
+func receiveRequestHeaders(incomingRoute *router.Route) (lowHash *externalapi.DomainHash,
+	highHash *externalapi.DomainHash, err error) {
+
+	message, err := incomingRoute.Dequeue()
+	if err != nil {
+		return nil, nil, err
+	}
+	msgRequestIBDBlocks := message.(*appmessage.MsgRequestHeaders)
+
+	return msgRequestIBDBlocks.LowHash, msgRequestIBDBlocks.HighHash, nil
+}

app/protocol/flows/v5/blockrelay/handle_request_pruning_point_utxo_set.go

@@ -0,0 +1,140 @@
+package blockrelay
+
+import (
+	"errors"
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/app/protocol/common"
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/domain"
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+	"github.com/kaspanet/kaspad/domain/consensus/ruleerrors"
+	"github.com/kaspanet/kaspad/infrastructure/logger"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+)
+
+// HandleRequestPruningPointUTXOSetContext is the interface for the context needed for the HandleRequestPruningPointUTXOSet flow.
+type HandleRequestPruningPointUTXOSetContext interface {
+	Domain() domain.Domain
+}
+
+type handleRequestPruningPointUTXOSetFlow struct {
+	HandleRequestPruningPointUTXOSetContext
+	incomingRoute, outgoingRoute *router.Route
+}
+
+// HandleRequestPruningPointUTXOSet listens to appmessage.MsgRequestPruningPointUTXOSet messages and sends
+// the pruning point UTXO set and block body.
+func HandleRequestPruningPointUTXOSet(context HandleRequestPruningPointUTXOSetContext, incomingRoute,
+	outgoingRoute *router.Route) error {
+
+	flow := &handleRequestPruningPointUTXOSetFlow{
+		HandleRequestPruningPointUTXOSetContext: context,
+		incomingRoute:                           incomingRoute,
+		outgoingRoute:                           outgoingRoute,
+	}
+
+	return flow.start()
+}
+
+func (flow *handleRequestPruningPointUTXOSetFlow) start() error {
+	for {
+		msgRequestPruningPointUTXOSet, err := flow.waitForRequestPruningPointUTXOSetMessages()
+		if err != nil {
+			return err
+		}
+
+		err = flow.handleRequestPruningPointUTXOSetMessage(msgRequestPruningPointUTXOSet)
+		if err != nil {
+			return err
+		}
+	}
+}
+
+func (flow *handleRequestPruningPointUTXOSetFlow) handleRequestPruningPointUTXOSetMessage(
+	msgRequestPruningPointUTXOSet *appmessage.MsgRequestPruningPointUTXOSet) error {
+
+	onEnd := logger.LogAndMeasureExecutionTime(log, "handleRequestPruningPointUTXOSetFlow")
+	defer onEnd()
+
+	log.Debugf("Got request for pruning point UTXO set")
+
+	return flow.sendPruningPointUTXOSet(msgRequestPruningPointUTXOSet)
+}
+
+func (flow *handleRequestPruningPointUTXOSetFlow) waitForRequestPruningPointUTXOSetMessages() (
+	*appmessage.MsgRequestPruningPointUTXOSet, error) {
+
+	message, err := flow.incomingRoute.Dequeue()
+	if err != nil {
+		return nil, err
+	}
+	msgRequestPruningPointUTXOSet, ok := message.(*appmessage.MsgRequestPruningPointUTXOSet)
+	if !ok {
+		// TODO: Change to shouldBan: true once we fix the bug of getting redundant messages
+		return nil, protocolerrors.Errorf(false, "received unexpected message type. "+
+			"expected: %s, got: %s", appmessage.CmdRequestPruningPointUTXOSet, message.Command())
+	}
+	return msgRequestPruningPointUTXOSet, nil
+}
+
+func (flow *handleRequestPruningPointUTXOSetFlow) sendPruningPointUTXOSet(
+	msgRequestPruningPointUTXOSet *appmessage.MsgRequestPruningPointUTXOSet) error {
+
+	// Send the UTXO set in `step`-sized chunks
+	const step = 1000
+	var fromOutpoint *externalapi.DomainOutpoint
+	chunksSent := 0
+	for {
+		pruningPointUTXOs, err := flow.Domain().Consensus().GetPruningPointUTXOs(
+			msgRequestPruningPointUTXOSet.PruningPointHash, fromOutpoint, step)
+		if err != nil {
+			if errors.Is(err, ruleerrors.ErrWrongPruningPointHash) {
+				return flow.outgoingRoute.Enqueue(appmessage.NewMsgUnexpectedPruningPoint())
+			}
+		}
+
+		log.Debugf("Retrieved %d UTXOs for pruning block %s",
+			len(pruningPointUTXOs), msgRequestPruningPointUTXOSet.PruningPointHash)
+
+		outpointAndUTXOEntryPairs :=
+			appmessage.DomainOutpointAndUTXOEntryPairsToOutpointAndUTXOEntryPairs(pruningPointUTXOs)
+		err = flow.outgoingRoute.Enqueue(appmessage.NewMsgPruningPointUTXOSetChunk(outpointAndUTXOEntryPairs))
+		if err != nil {
+			return err
+		}
+
+		finished := len(pruningPointUTXOs) < step
+		if finished && chunksSent%ibdBatchSize != 0 {
+			log.Debugf("Finished sending UTXOs for pruning block %s",
+				msgRequestPruningPointUTXOSet.PruningPointHash)
+
+			return flow.outgoingRoute.Enqueue(appmessage.NewMsgDonePruningPointUTXOSetChunks())
+		}
+
+		if len(pruningPointUTXOs) > 0 {
+			fromOutpoint = pruningPointUTXOs[len(pruningPointUTXOs)-1].Outpoint
+		}
+		chunksSent++
+
+		// Wait for the peer to request more chunks every `ibdBatchSize` chunks
+		if chunksSent%ibdBatchSize == 0 {
+			message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
+			if err != nil {
+				return err
+			}
+			_, ok := message.(*appmessage.MsgRequestNextPruningPointUTXOSetChunk)
+			if !ok {
+				// TODO: Change to shouldBan: true once we fix the bug of getting redundant messages
+				return protocolerrors.Errorf(false, "received unexpected message type. "+
+					"expected: %s, got: %s", appmessage.CmdRequestNextPruningPointUTXOSetChunk, message.Command())
+			}
+
+			if finished {
+				log.Debugf("Finished sending UTXOs for pruning block %s",
+					msgRequestPruningPointUTXOSet.PruningPointHash)
+
+				return flow.outgoingRoute.Enqueue(appmessage.NewMsgDonePruningPointUTXOSetChunks())
+			}
+		}
+	}
+}

app/protocol/flows/v5/blockrelay/ibd.go

@@ -0,0 +1,723 @@
+package blockrelay
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/app/protocol/common"
+	peerpkg "github.com/kaspanet/kaspad/app/protocol/peer"
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/domain"
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+	"github.com/kaspanet/kaspad/domain/consensus/ruleerrors"
+	"github.com/kaspanet/kaspad/domain/consensus/utils/consensushashing"
+	"github.com/kaspanet/kaspad/infrastructure/config"
+	"github.com/kaspanet/kaspad/infrastructure/logger"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+	"github.com/pkg/errors"
+	"time"
+)
+
+// IBDContext is the interface for the context needed for the HandleIBD flow.
+type IBDContext interface {
+	Domain() domain.Domain
+	Config() *config.Config
+	OnNewBlock(block *externalapi.DomainBlock, virtualChangeSet *externalapi.VirtualChangeSet) error
+	OnVirtualChange(virtualChangeSet *externalapi.VirtualChangeSet) error
+	OnPruningPointUTXOSetOverride() error
+	IsIBDRunning() bool
+	TrySetIBDRunning(ibdPeer *peerpkg.Peer) bool
+	UnsetIBDRunning()
+	IsRecoverableError(err error) bool
+}
+
+type handleIBDFlow struct {
+	IBDContext
+	incomingRoute, outgoingRoute *router.Route
+	peer                         *peerpkg.Peer
+}
+
+// HandleIBD handles IBD
+func HandleIBD(context IBDContext, incomingRoute *router.Route, outgoingRoute *router.Route,
+	peer *peerpkg.Peer) error {
+
+	flow := &handleIBDFlow{
+		IBDContext:    context,
+		incomingRoute: incomingRoute,
+		outgoingRoute: outgoingRoute,
+		peer:          peer,
+	}
+	return flow.start()
+}
+
+func (flow *handleIBDFlow) start() error {
+	for {
+		// Wait for IBD requests triggered by other flows
+		block, ok := <-flow.peer.IBDRequestChannel()
+		if !ok {
+			return nil
+		}
+		err := flow.runIBDIfNotRunning(block)
+		if err != nil {
+			return err
+		}
+	}
+}
+
+func (flow *handleIBDFlow) runIBDIfNotRunning(block *externalapi.DomainBlock) error {
+	wasIBDNotRunning := flow.TrySetIBDRunning(flow.peer)
+	if !wasIBDNotRunning {
+		log.Debugf("IBD is already running")
+		return nil
+	}
+
+	isFinishedSuccessfully := false
+	defer func() {
+		flow.UnsetIBDRunning()
+		flow.logIBDFinished(isFinishedSuccessfully)
+	}()
+
+	relayBlockHash := consensushashing.BlockHash(block)
+
+	log.Debugf("IBD started with peer %s and relayBlockHash %s", flow.peer, relayBlockHash)
+	log.Debugf("Syncing blocks up to %s", relayBlockHash)
+	log.Debugf("Trying to find highest known syncer chain block from peer %s with relay hash %s", flow.peer, relayBlockHash)
+
+	syncerHeaderSelectedTipHash, highestKnownSyncerChainHash, err := flow.negotiateMissingSyncerChainSegment()
+	if err != nil {
+		return err
+	}
+
+	shouldDownloadHeadersProof, shouldSync, err := flow.shouldSyncAndShouldDownloadHeadersProof(
+		block, highestKnownSyncerChainHash)
+	if err != nil {
+		return err
+	}
+
+	if !shouldSync {
+		return nil
+	}
+
+	if shouldDownloadHeadersProof {
+		log.Infof("Starting IBD with headers proof")
+		err := flow.ibdWithHeadersProof(syncerHeaderSelectedTipHash, relayBlockHash, block.Header.DAAScore())
+		if err != nil {
+			return err
+		}
+	} else {
+		if flow.Config().NetParams().DisallowDirectBlocksOnTopOfGenesis && !flow.Config().AllowSubmitBlockWhenNotSynced {
+			isGenesisVirtualSelectedParent, err := flow.isGenesisVirtualSelectedParent()
+			if err != nil {
+				return err
+			}
+
+			if isGenesisVirtualSelectedParent {
+				log.Infof("Cannot IBD to %s because it won't change the pruning point. The node needs to IBD "+
+					"to the recent pruning point before normal operation can resume.", relayBlockHash)
+				return nil
+			}
+		}
+
+		err = flow.syncPruningPointFutureHeaders(
+			flow.Domain().Consensus(),
+			syncerHeaderSelectedTipHash, highestKnownSyncerChainHash, relayBlockHash, block.Header.DAAScore())
+		if err != nil {
+			return err
+		}
+	}
+
+	// We start by syncing missing bodies over the syncer selected chain
+	err = flow.syncMissingBlockBodies(syncerHeaderSelectedTipHash)
+	if err != nil {
+		return err
+	}
+	relayBlockInfo, err := flow.Domain().Consensus().GetBlockInfo(relayBlockHash)
+	if err != nil {
+		return err
+	}
+	// Relay block might be in the anticone of syncer selected tip, thus
+	// check his chain for missing bodies as well.
+	// Note: this operation can be slightly optimized to avoid the full chain search since relay block
+	// is in syncer virtual mergeset which has bounded size.
+	if relayBlockInfo.BlockStatus == externalapi.StatusHeaderOnly {
+		err = flow.syncMissingBlockBodies(relayBlockHash)
+		if err != nil {
+			return err
+		}
+	}
+
+	log.Debugf("Finished syncing blocks up to %s", relayBlockHash)
+	isFinishedSuccessfully = true
+	return nil
+}
+
+func (flow *handleIBDFlow) negotiateMissingSyncerChainSegment() (*externalapi.DomainHash, *externalapi.DomainHash, error) {
+	/*
+		Algorithm:
+			Request full selected chain block locator from syncer
+			Find the highest block which we know
+			Repeat the locator step over the new range until finding max(past(syncee) \cap chain(syncer))
+	*/
+
+	// Empty hashes indicate that the full chain is queried
+	locatorHashes, err := flow.getSyncerChainBlockLocator(nil, nil, common.DefaultTimeout)
+	if err != nil {
+		return nil, nil, err
+	}
+	if len(locatorHashes) == 0 {
+		return nil, nil, protocolerrors.Errorf(true, "Expecting initial syncer chain block locator "+
+			"to contain at least one element")
+	}
+	log.Debugf("IBD chain negotiation with peer %s started and received %d hashes (%s, %s)", flow.peer,
+		len(locatorHashes), locatorHashes[0], locatorHashes[len(locatorHashes)-1])
+	syncerHeaderSelectedTipHash := locatorHashes[0]
+	var highestKnownSyncerChainHash *externalapi.DomainHash
+	chainNegotiationRestartCounter := 0
+	chainNegotiationZoomCounts := 0
+	initialLocatorLen := len(locatorHashes)
+	for {
+		var lowestUnknownSyncerChainHash, currentHighestKnownSyncerChainHash *externalapi.DomainHash
+		for _, syncerChainHash := range locatorHashes {
+			info, err := flow.Domain().Consensus().GetBlockInfo(syncerChainHash)
+			if err != nil {
+				return nil, nil, err
+			}
+			if info.Exists {
+				currentHighestKnownSyncerChainHash = syncerChainHash
+				break
+			}
+			lowestUnknownSyncerChainHash = syncerChainHash
+		}
+		// No unknown blocks, break. Note this can only happen in the first iteration
+		if lowestUnknownSyncerChainHash == nil {
+			highestKnownSyncerChainHash = currentHighestKnownSyncerChainHash
+			break
+		}
+		// No shared block, break
+		if currentHighestKnownSyncerChainHash == nil {
+			highestKnownSyncerChainHash = nil
+			break
+		}
+		// No point in zooming further
+		if len(locatorHashes) == 1 {
+			highestKnownSyncerChainHash = currentHighestKnownSyncerChainHash
+			break
+		}
+		// Zoom in
+		locatorHashes, err = flow.getSyncerChainBlockLocator(
+			lowestUnknownSyncerChainHash,
+			currentHighestKnownSyncerChainHash, time.Second*10)
+		if err != nil {
+			return nil, nil, err
+		}
+		if len(locatorHashes) > 0 {
+			if !locatorHashes[0].Equal(lowestUnknownSyncerChainHash) ||
+				!locatorHashes[len(locatorHashes)-1].Equal(currentHighestKnownSyncerChainHash) {
+				return nil, nil, protocolerrors.Errorf(true, "Expecting the high and low "+
+					"hashes to match the locator bounds")
+			}
+
+			chainNegotiationZoomCounts++
+			log.Debugf("IBD chain negotiation with peer %s zoomed in (%d) and received %d hashes (%s, %s)", flow.peer,
+				chainNegotiationZoomCounts, len(locatorHashes), locatorHashes[0], locatorHashes[len(locatorHashes)-1])
+
+			if len(locatorHashes) == 2 {
+				// We found our search target
+				highestKnownSyncerChainHash = currentHighestKnownSyncerChainHash
+				break
+			}
+
+			if chainNegotiationZoomCounts > initialLocatorLen*2 {
+				// Since the zoom-in always queries two consecutive entries in the previous locator, it is
+				// expected to decrease in size at least every two iterations
+				return nil, nil, protocolerrors.Errorf(true,
+					"IBD chain negotiation: Number of zoom-in steps %d exceeded the upper bound of 2*%d",
+					chainNegotiationZoomCounts, initialLocatorLen)
+			}
+
+		} else { // Empty locator signals a restart due to chain changes
+			chainNegotiationZoomCounts = 0
+			chainNegotiationRestartCounter++
+			if chainNegotiationRestartCounter > 32 {
+				return nil, nil, protocolerrors.Errorf(false,
+					"IBD chain negotiation with syncer %s exceeded restart limit %d", flow.peer, chainNegotiationRestartCounter)
+			}
+			log.Warnf("IBD chain negotiation with syncer %s restarted %d times", flow.peer, chainNegotiationRestartCounter)
+
+			// An empty locator signals that the syncer chain was modified and no longer contains one of
+			// the queried hashes, so we restart the search. We use a shorter timeout here to avoid a timeout attack
+			locatorHashes, err = flow.getSyncerChainBlockLocator(nil, nil, time.Second*10)
+			if err != nil {
+				return nil, nil, err
+			}
+			if len(locatorHashes) == 0 {
+				return nil, nil, protocolerrors.Errorf(true, "Expecting initial syncer chain block locator "+
+					"to contain at least one element")
+			}
+			log.Infof("IBD chain negotiation with peer %s restarted (%d) and received %d hashes (%s, %s)", flow.peer,
+				chainNegotiationRestartCounter, len(locatorHashes), locatorHashes[0], locatorHashes[len(locatorHashes)-1])
+
+			initialLocatorLen = len(locatorHashes)
+			// Reset syncer's header selected tip
+			syncerHeaderSelectedTipHash = locatorHashes[0]
+		}
+	}
+
+	log.Debugf("Found highest known syncer chain block %s from peer %s",
+		highestKnownSyncerChainHash, flow.peer)
+
+	return syncerHeaderSelectedTipHash, highestKnownSyncerChainHash, nil
+}
+
+func (flow *handleIBDFlow) isGenesisVirtualSelectedParent() (bool, error) {
+	virtualSelectedParent, err := flow.Domain().Consensus().GetVirtualSelectedParent()
+	if err != nil {
+		return false, err
+	}
+
+	return virtualSelectedParent.Equal(flow.Config().NetParams().GenesisHash), nil
+}
+
+func (flow *handleIBDFlow) logIBDFinished(isFinishedSuccessfully bool) {
+	successString := "successfully"
+	if !isFinishedSuccessfully {
+		successString = "(interrupted)"
+	}
+	log.Infof("IBD with peer %s finished %s", flow.peer, successString)
+}
+
+func (flow *handleIBDFlow) getSyncerChainBlockLocator(
+	highHash, lowHash *externalapi.DomainHash, timeout time.Duration) ([]*externalapi.DomainHash, error) {
+
+	requestIbdChainBlockLocatorMessage := appmessage.NewMsgIBDRequestChainBlockLocator(highHash, lowHash)
+	err := flow.outgoingRoute.Enqueue(requestIbdChainBlockLocatorMessage)
+	if err != nil {
+		return nil, err
+	}
+	message, err := flow.incomingRoute.DequeueWithTimeout(timeout)
+	if err != nil {
+		return nil, err
+	}
+	switch message := message.(type) {
+	case *appmessage.MsgIBDChainBlockLocator:
+		if len(message.BlockLocatorHashes) > 64 {
+			return nil, protocolerrors.Errorf(true,
+				"Got block locator of size %d>64 while expecting locator to have size "+
+					"which is logarithmic in DAG size (which should never exceed 2^64)",
+				len(message.BlockLocatorHashes))
+		}
+		return message.BlockLocatorHashes, nil
+	default:
+		return nil, protocolerrors.Errorf(true, "received unexpected message type. "+
+			"expected: %s, got: %s", appmessage.CmdIBDChainBlockLocator, message.Command())
+	}
+}
+
+func (flow *handleIBDFlow) syncPruningPointFutureHeaders(consensus externalapi.Consensus,
+	syncerHeaderSelectedTipHash, highestKnownSyncerChainHash, relayBlockHash *externalapi.DomainHash,
+	highBlockDAAScoreHint uint64) error {
+
+	log.Infof("Downloading headers from %s", flow.peer)
+
+	if highestKnownSyncerChainHash.Equal(syncerHeaderSelectedTipHash) {
+		// No need to get syncer selected tip headers, so sync relay past and return
+		return flow.syncMissingRelayPast(consensus, syncerHeaderSelectedTipHash, relayBlockHash)
+	}
+
+	err := flow.sendRequestHeaders(highestKnownSyncerChainHash, syncerHeaderSelectedTipHash)
+	if err != nil {
+		return err
+	}
+
+	highestSharedBlockHeader, err := consensus.GetBlockHeader(highestKnownSyncerChainHash)
+	if err != nil {
+		return err
+	}
+	progressReporter := newIBDProgressReporter(highestSharedBlockHeader.DAAScore(), highBlockDAAScoreHint, "block headers")
+
+	// Keep a short queue of BlockHeadersMessages so that there's
+	// never a moment when the node is not validating and inserting
+	// headers
+	blockHeadersMessageChan := make(chan *appmessage.BlockHeadersMessage, 2)
+	errChan := make(chan error)
+	spawn("handleRelayInvsFlow-syncPruningPointFutureHeaders", func() {
+		for {
+			blockHeadersMessage, doneIBD, err := flow.receiveHeaders()
+			if err != nil {
+				errChan <- err
+				return
+			}
+			if doneIBD {
+				close(blockHeadersMessageChan)
+				return
+			}
+			if len(blockHeadersMessage.BlockHeaders) == 0 {
+				// The syncer should have sent a done message if the search completed, and not an empty list
+				errChan <- protocolerrors.Errorf(true, "Received an empty headers message from peer %s", flow.peer)
+				return
+			}
+
+			blockHeadersMessageChan <- blockHeadersMessage
+
+			err = flow.outgoingRoute.Enqueue(appmessage.NewMsgRequestNextHeaders())
+			if err != nil {
+				errChan <- err
+				return
+			}
+		}
+	})
+
+	for {
+		select {
+		case ibdBlocksMessage, ok := <-blockHeadersMessageChan:
+			if !ok {
+				return flow.syncMissingRelayPast(consensus, syncerHeaderSelectedTipHash, relayBlockHash)
+			}
+			for _, header := range ibdBlocksMessage.BlockHeaders {
+				err = flow.processHeader(consensus, header)
+				if err != nil {
+					return err
+				}
+			}
+
+			lastReceivedHeader := ibdBlocksMessage.BlockHeaders[len(ibdBlocksMessage.BlockHeaders)-1]
+			progressReporter.reportProgress(len(ibdBlocksMessage.BlockHeaders), lastReceivedHeader.DAAScore)
+		case err := <-errChan:
+			return err
+		}
+	}
+}
+
+func (flow *handleIBDFlow) syncMissingRelayPast(consensus externalapi.Consensus, syncerHeaderSelectedTipHash *externalapi.DomainHash, relayBlockHash *externalapi.DomainHash) error {
+	// Finished downloading syncer selected tip blocks,
+	// check if we already have the triggering relayBlockHash
+	relayBlockInfo, err := consensus.GetBlockInfo(relayBlockHash)
+	if err != nil {
+		return err
+	}
+	if !relayBlockInfo.Exists {
+		// Send a special header request for the selected tip anticone. This is expected to
+		// be a small set, as it is bounded to the size of virtual's mergeset.
+		err = flow.sendRequestAnticone(syncerHeaderSelectedTipHash, relayBlockHash)
+		if err != nil {
+			return err
+		}
+		anticoneHeadersMessage, anticoneDone, err := flow.receiveHeaders()
+		if err != nil {
+			return err
+		}
+		if anticoneDone {
+			return protocolerrors.Errorf(true,
+				"Expected one anticone header chunk for past(%s) cap anticone(%s) but got zero",
+				relayBlockHash, syncerHeaderSelectedTipHash)
+		}
+		_, anticoneDone, err = flow.receiveHeaders()
+		if err != nil {
+			return err
+		}
+		if !anticoneDone {
+			return protocolerrors.Errorf(true,
+				"Expected only one anticone header chunk for past(%s) cap anticone(%s)",
+				relayBlockHash, syncerHeaderSelectedTipHash)
+		}
+		for _, header := range anticoneHeadersMessage.BlockHeaders {
+			err = flow.processHeader(consensus, header)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	// If the relayBlockHash has still not been received, the peer is misbehaving
+	relayBlockInfo, err = consensus.GetBlockInfo(relayBlockHash)
+	if err != nil {
+		return err
+	}
+	if !relayBlockInfo.Exists {
+		return protocolerrors.Errorf(true, "did not receive "+
+			"relayBlockHash block %s from peer %s during block download", relayBlockHash, flow.peer)
+	}
+	return nil
+}
+
+func (flow *handleIBDFlow) sendRequestAnticone(
+	syncerHeaderSelectedTipHash, relayBlockHash *externalapi.DomainHash) error {
+
+	msgRequestAnticone := appmessage.NewMsgRequestAnticone(syncerHeaderSelectedTipHash, relayBlockHash)
+	return flow.outgoingRoute.Enqueue(msgRequestAnticone)
+}
+
+func (flow *handleIBDFlow) sendRequestHeaders(
+	highestKnownSyncerChainHash, syncerHeaderSelectedTipHash *externalapi.DomainHash) error {
+
+	msgRequestHeaders := appmessage.NewMsgRequstHeaders(highestKnownSyncerChainHash, syncerHeaderSelectedTipHash)
+	return flow.outgoingRoute.Enqueue(msgRequestHeaders)
+}
+
+func (flow *handleIBDFlow) receiveHeaders() (msgIBDBlock *appmessage.BlockHeadersMessage, doneHeaders bool, err error) {
+	message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
+	if err != nil {
+		return nil, false, err
+	}
+	switch message := message.(type) {
+	case *appmessage.BlockHeadersMessage:
+		return message, false, nil
+	case *appmessage.MsgDoneHeaders:
+		return nil, true, nil
+	default:
+		return nil, false,
+			protocolerrors.Errorf(true, "received unexpected message type. "+
+				"expected: %s or %s, got: %s",
+				appmessage.CmdBlockHeaders,
+				appmessage.CmdDoneHeaders,
+				message.Command())
+	}
+}
+
+func (flow *handleIBDFlow) processHeader(consensus externalapi.Consensus, msgBlockHeader *appmessage.MsgBlockHeader) error {
+	header := appmessage.BlockHeaderToDomainBlockHeader(msgBlockHeader)
+	block := &externalapi.DomainBlock{
+		Header:       header,
+		Transactions: nil,
+	}
+
+	blockHash := consensushashing.BlockHash(block)
+	blockInfo, err := consensus.GetBlockInfo(blockHash)
+	if err != nil {
+		return err
+	}
+	if blockInfo.Exists {
+		log.Debugf("Block header %s is already in the DAG. Skipping...", blockHash)
+		return nil
+	}
+	_, err = consensus.ValidateAndInsertBlock(block, false)
+	if err != nil {
+		if !errors.As(err, &ruleerrors.RuleError{}) {
+			return errors.Wrapf(err, "failed to process header %s during IBD", blockHash)
+		}
+
+		if errors.Is(err, ruleerrors.ErrDuplicateBlock) {
+			log.Debugf("Skipping block header %s as it is a duplicate", blockHash)
+		} else {
+			log.Infof("Rejected block header %s from %s during IBD: %s", blockHash, flow.peer, err)
+			return protocolerrors.Wrapf(true, err, "got invalid block header %s during IBD", blockHash)
+		}
+	}
+
+	return nil
+}
+
+func (flow *handleIBDFlow) validatePruningPointFutureHeaderTimestamps() error {
+	headerSelectedTipHash, err := flow.Domain().StagingConsensus().GetHeadersSelectedTip()
+	if err != nil {
+		return err
+	}
+	headerSelectedTipHeader, err := flow.Domain().StagingConsensus().GetBlockHeader(headerSelectedTipHash)
+	if err != nil {
+		return err
+	}
+	headerSelectedTipTimestamp := headerSelectedTipHeader.TimeInMilliseconds()
+
+	currentSelectedTipHash, err := flow.Domain().Consensus().GetHeadersSelectedTip()
+	if err != nil {
+		return err
+	}
+	currentSelectedTipHeader, err := flow.Domain().Consensus().GetBlockHeader(currentSelectedTipHash)
+	if err != nil {
+		return err
+	}
+	currentSelectedTipTimestamp := currentSelectedTipHeader.TimeInMilliseconds()
+
+	if headerSelectedTipTimestamp < currentSelectedTipTimestamp {
+		return protocolerrors.Errorf(false, "the timestamp of the candidate selected "+
+			"tip is smaller than the current selected tip")
+	}
+
+	minTimestampDifferenceInMilliseconds := (10 * time.Minute).Milliseconds()
+	if headerSelectedTipTimestamp-currentSelectedTipTimestamp < minTimestampDifferenceInMilliseconds {
+		return protocolerrors.Errorf(false, "difference between the timestamps of "+
+			"the current pruning point and the candidate pruning point is too small. Aborting IBD...")
+	}
+	return nil
+}
+
+func (flow *handleIBDFlow) receiveAndInsertPruningPointUTXOSet(
+	consensus externalapi.Consensus, pruningPointHash *externalapi.DomainHash) (bool, error) {
+
+	onEnd := logger.LogAndMeasureExecutionTime(log, "receiveAndInsertPruningPointUTXOSet")
+	defer onEnd()
+
+	receivedChunkCount := 0
+	receivedUTXOCount := 0
+	for {
+		message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
+		if err != nil {
+			return false, err
+		}
+
+		switch message := message.(type) {
+		case *appmessage.MsgPruningPointUTXOSetChunk:
+			receivedUTXOCount += len(message.OutpointAndUTXOEntryPairs)
+			domainOutpointAndUTXOEntryPairs :=
+				appmessage.OutpointAndUTXOEntryPairsToDomainOutpointAndUTXOEntryPairs(message.OutpointAndUTXOEntryPairs)
+
+			err := consensus.AppendImportedPruningPointUTXOs(domainOutpointAndUTXOEntryPairs)
+			if err != nil {
+				return false, err
+			}
+
+			receivedChunkCount++
+			if receivedChunkCount%ibdBatchSize == 0 {
+				log.Debugf("Received %d UTXO set chunks so far, totaling in %d UTXOs",
+					receivedChunkCount, receivedUTXOCount)
+
+				requestNextPruningPointUTXOSetChunkMessage := appmessage.NewMsgRequestNextPruningPointUTXOSetChunk()
+				err := flow.outgoingRoute.Enqueue(requestNextPruningPointUTXOSetChunkMessage)
+				if err != nil {
+					return false, err
+				}
+			}
+
+		case *appmessage.MsgDonePruningPointUTXOSetChunks:
+			log.Infof("Finished receiving the UTXO set. Total UTXOs: %d", receivedUTXOCount)
+			return true, nil
+
+		case *appmessage.MsgUnexpectedPruningPoint:
+			log.Infof("Could not receive the next UTXO chunk because the pruning point %s "+
+				"is no longer the pruning point of peer %s", pruningPointHash, flow.peer)
+			return false, nil
+
+		default:
+			return false, protocolerrors.Errorf(true, "received unexpected message type. "+
+				"expected: %s or %s or %s, got: %s", appmessage.CmdPruningPointUTXOSetChunk,
+				appmessage.CmdDonePruningPointUTXOSetChunks, appmessage.CmdUnexpectedPruningPoint, message.Command(),
+			)
+		}
+	}
+}
+
+func (flow *handleIBDFlow) syncMissingBlockBodies(highHash *externalapi.DomainHash) error {
+	hashes, err := flow.Domain().Consensus().GetMissingBlockBodyHashes(highHash)
+	if err != nil {
+		return err
+	}
+	if len(hashes) == 0 {
+		// Blocks can be inserted inside the DAG during IBD if those were requested before IBD started.
+		// In rare cases, all the IBD blocks might be already inserted by the time we reach this point.
+		// In these cases - GetMissingBlockBodyHashes would return an empty array.
+		log.Debugf("No missing block body hashes found.")
+		return nil
+	}
+
+	lowBlockHeader, err := flow.Domain().Consensus().GetBlockHeader(hashes[0])
+	if err != nil {
+		return err
+	}
+	highBlockHeader, err := flow.Domain().Consensus().GetBlockHeader(hashes[len(hashes)-1])
+	if err != nil {
+		return err
+	}
+	progressReporter := newIBDProgressReporter(lowBlockHeader.DAAScore(), highBlockHeader.DAAScore(), "blocks")
+	highestProcessedDAAScore := lowBlockHeader.DAAScore()
+
+	for offset := 0; offset < len(hashes); offset += ibdBatchSize {
+		var hashesToRequest []*externalapi.DomainHash
+		if offset+ibdBatchSize < len(hashes) {
+			hashesToRequest = hashes[offset : offset+ibdBatchSize]
+		} else {
+			hashesToRequest = hashes[offset:]
+		}
+
+		err := flow.outgoingRoute.Enqueue(appmessage.NewMsgRequestIBDBlocks(hashesToRequest))
+		if err != nil {
+			return err
+		}
+
+		for _, expectedHash := range hashesToRequest {
+			message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
+			if err != nil {
+				return err
+			}
+
+			msgIBDBlock, ok := message.(*appmessage.MsgIBDBlock)
+			if !ok {
+				return protocolerrors.Errorf(true, "received unexpected message type. "+
+					"expected: %s, got: %s", appmessage.CmdIBDBlock, message.Command())
+			}
+
+			block := appmessage.MsgBlockToDomainBlock(msgIBDBlock.MsgBlock)
+			blockHash := consensushashing.BlockHash(block)
+			if !expectedHash.Equal(blockHash) {
+				return protocolerrors.Errorf(true, "expected block %s but got %s", expectedHash, blockHash)
+			}
+
+			err = flow.banIfBlockIsHeaderOnly(block)
+			if err != nil {
+				return err
+			}
+
+			virtualChangeSet, err := flow.Domain().Consensus().ValidateAndInsertBlock(block, false)
+			if err != nil {
+				if errors.Is(err, ruleerrors.ErrDuplicateBlock) {
+					log.Debugf("Skipping IBD Block %s as it has already been added to the DAG", blockHash)
+					continue
+				}
+				return protocolerrors.ConvertToBanningProtocolErrorIfRuleError(err, "invalid block %s", blockHash)
+			}
+			err = flow.OnNewBlock(block, virtualChangeSet)
+			if err != nil {
+				return err
+			}
+
+			highestProcessedDAAScore = block.Header.DAAScore()
+		}
+
+		progressReporter.reportProgress(len(hashesToRequest), highestProcessedDAAScore)
+	}
+
+	return flow.resolveVirtual(highestProcessedDAAScore)
+}
+
+func (flow *handleIBDFlow) banIfBlockIsHeaderOnly(block *externalapi.DomainBlock) error {
+	if len(block.Transactions) == 0 {
+		return protocolerrors.Errorf(true, "sent header of %s block where expected block with body",
+			consensushashing.BlockHash(block))
+	}
+
+	return nil
+}
+
+func (flow *handleIBDFlow) resolveVirtual(estimatedVirtualDAAScoreTarget uint64) error {
+	virtualDAAScoreStart, err := flow.Domain().Consensus().GetVirtualDAAScore()
+	if err != nil {
+		return err
+	}
+
+	for i := 0; ; i++ {
+		if i%10 == 0 {
+			virtualDAAScore, err := flow.Domain().Consensus().GetVirtualDAAScore()
+			if err != nil {
+				return err
+			}
+			var percents int
+			if estimatedVirtualDAAScoreTarget-virtualDAAScoreStart <= 0 {
+				percents = 100
+			} else {
+				percents = int(float64(virtualDAAScore-virtualDAAScoreStart) / float64(estimatedVirtualDAAScoreTarget-virtualDAAScoreStart) * 100)
+			}
+			log.Infof("Resolving virtual. Estimated progress: %d%%", percents)
+		}
+		virtualChangeSet, isCompletelyResolved, err := flow.Domain().Consensus().ResolveVirtual()
+		if err != nil {
+			return err
+		}
+
+		err = flow.OnVirtualChange(virtualChangeSet)
+		if err != nil {
+			return err
+		}
+
+		if isCompletelyResolved {
+			log.Infof("Resolved virtual")
+			return nil
+		}
+	}
+}

app/protocol/flows/v5/blockrelay/ibd_progress_reporter.go

@@ -0,0 +1,45 @@
+package blockrelay
+
+type ibdProgressReporter struct {
+	lowDAAScore                 uint64
+	highDAAScore                uint64
+	objectName                  string
+	totalDAAScoreDifference     uint64
+	lastReportedProgressPercent int
+	processed                   int
+}
+
+func newIBDProgressReporter(lowDAAScore uint64, highDAAScore uint64, objectName string) *ibdProgressReporter {
+	if highDAAScore <= lowDAAScore {
+		// Avoid a zero or negative diff
+		highDAAScore = lowDAAScore + 1
+	}
+	return &ibdProgressReporter{
+		lowDAAScore:                 lowDAAScore,
+		highDAAScore:                highDAAScore,
+		objectName:                  objectName,
+		totalDAAScoreDifference:     highDAAScore - lowDAAScore,
+		lastReportedProgressPercent: 0,
+		processed:                   0,
+	}
+}
+
+func (ipr *ibdProgressReporter) reportProgress(processedDelta int, highestProcessedDAAScore uint64) {
+	ipr.processed += processedDelta
+
+	// Avoid exploding numbers in the percentage report, since the original `highDAAScore` might have been only a hint
+	if highestProcessedDAAScore > ipr.highDAAScore {
+		ipr.highDAAScore = highestProcessedDAAScore + 1 // + 1 for keeping it at 99%
+		ipr.totalDAAScoreDifference = ipr.highDAAScore - ipr.lowDAAScore
+	}
+	relativeDAAScore := uint64(0)
+	if highestProcessedDAAScore > ipr.lowDAAScore {
+		// Avoid a negative diff
+		relativeDAAScore = highestProcessedDAAScore - ipr.lowDAAScore
+	}
+	progressPercent := int((float64(relativeDAAScore) / float64(ipr.totalDAAScoreDifference)) * 100)
+	if progressPercent > ipr.lastReportedProgressPercent {
+		log.Infof("IBD: Processed %d %s (%d%%)", ipr.processed, ipr.objectName, progressPercent)
+		ipr.lastReportedProgressPercent = progressPercent
+	}
+}

app/protocol/flows/v5/blockrelay/ibd_with_headers_proof.go

@@ -0,0 +1,428 @@
+package blockrelay
+
+import (
+	"fmt"
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/app/protocol/common"
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+	"github.com/kaspanet/kaspad/domain/consensus/ruleerrors"
+	"github.com/kaspanet/kaspad/domain/consensus/utils/consensushashing"
+	"github.com/pkg/errors"
+	"time"
+)
+
+func (flow *handleIBDFlow) ibdWithHeadersProof(
+	syncerHeaderSelectedTipHash, relayBlockHash *externalapi.DomainHash, highBlockDAAScore uint64) error {
+	err := flow.Domain().InitStagingConsensus()
+	if err != nil {
+		return err
+	}
+
+	err = flow.downloadHeadersAndPruningUTXOSet(syncerHeaderSelectedTipHash, relayBlockHash, highBlockDAAScore)
+	if err != nil {
+		if !flow.IsRecoverableError(err) {
+			return err
+		}
+
+		log.Infof("IBD with pruning proof from %s was unsuccessful. Deleting the staging consensus.", flow.peer)
+		deleteStagingConsensusErr := flow.Domain().DeleteStagingConsensus()
+		if deleteStagingConsensusErr != nil {
+			return deleteStagingConsensusErr
+		}
+
+		return err
+	}
+
+	log.Infof("Header download stage of IBD with pruning proof completed successfully from %s. "+
+		"Committing the staging consensus and deleting the previous obsolete one if such exists.", flow.peer)
+	err = flow.Domain().CommitStagingConsensus()
+	if err != nil {
+		return err
+	}
+
+	err = flow.OnPruningPointUTXOSetOverride()
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (flow *handleIBDFlow) shouldSyncAndShouldDownloadHeadersProof(
+	relayBlock *externalapi.DomainBlock,
+	highestKnownSyncerChainHash *externalapi.DomainHash) (shouldDownload, shouldSync bool, err error) {
+
+	var highestSharedBlockFound, isPruningPointInSharedBlockChain bool
+	if highestKnownSyncerChainHash != nil {
+		highestSharedBlockFound = true
+		pruningPoint, err := flow.Domain().Consensus().PruningPoint()
+		if err != nil {
+			return false, false, err
+		}
+
+		isPruningPointInSharedBlockChain, err = flow.Domain().Consensus().IsInSelectedParentChainOf(
+			pruningPoint, highestKnownSyncerChainHash)
+		if err != nil {
+			return false, false, err
+		}
+	}
+	// Note: in the case where `highestSharedBlockFound == true && isPruningPointInSharedBlockChain == false`
+	// we might have here info which is relevant to finality conflict decisions. This should be taken into
+	// account when we improve this aspect.
+	if !highestSharedBlockFound || !isPruningPointInSharedBlockChain {
+		hasMoreBlueWorkThanSelectedTipAndPruningDepthMoreBlueScore, err := flow.checkIfHighHashHasMoreBlueWorkThanSelectedTipAndPruningDepthMoreBlueScore(relayBlock)
+		if err != nil {
+			return false, false, err
+		}
+
+		if hasMoreBlueWorkThanSelectedTipAndPruningDepthMoreBlueScore {
+			return true, true, nil
+		}
+
+		return false, false, nil
+	}
+
+	return false, true, nil
+}
+
+func (flow *handleIBDFlow) checkIfHighHashHasMoreBlueWorkThanSelectedTipAndPruningDepthMoreBlueScore(relayBlock *externalapi.DomainBlock) (bool, error) {
+	headersSelectedTip, err := flow.Domain().Consensus().GetHeadersSelectedTip()
+	if err != nil {
+		return false, err
+	}
+
+	headersSelectedTipInfo, err := flow.Domain().Consensus().GetBlockInfo(headersSelectedTip)
+	if err != nil {
+		return false, err
+	}
+
+	if relayBlock.Header.BlueScore() < headersSelectedTipInfo.BlueScore+flow.Config().NetParams().PruningDepth() {
+		return false, nil
+	}
+
+	return relayBlock.Header.BlueWork().Cmp(headersSelectedTipInfo.BlueWork) > 0, nil
+}
+
+func (flow *handleIBDFlow) syncAndValidatePruningPointProof() (*externalapi.DomainHash, error) {
+	log.Infof("Downloading the pruning point proof from %s", flow.peer)
+	err := flow.outgoingRoute.Enqueue(appmessage.NewMsgRequestPruningPointProof())
+	if err != nil {
+		return nil, err
+	}
+	message, err := flow.incomingRoute.DequeueWithTimeout(10 * time.Minute)
+	if err != nil {
+		return nil, err
+	}
+	pruningPointProofMessage, ok := message.(*appmessage.MsgPruningPointProof)
+	if !ok {
+		return nil, protocolerrors.Errorf(true, "received unexpected message type. "+
+			"expected: %s, got: %s", appmessage.CmdPruningPointProof, message.Command())
+	}
+	pruningPointProof := appmessage.MsgPruningPointProofToDomainPruningPointProof(pruningPointProofMessage)
+	err = flow.Domain().Consensus().ValidatePruningPointProof(pruningPointProof)
+	if err != nil {
+		if errors.As(err, &ruleerrors.RuleError{}) {
+			return nil, protocolerrors.Wrapf(true, err, "pruning point proof validation failed")
+		}
+		return nil, err
+	}
+
+	err = flow.Domain().StagingConsensus().ApplyPruningPointProof(pruningPointProof)
+	if err != nil {
+		return nil, err
+	}
+
+	return consensushashing.HeaderHash(pruningPointProof.Headers[0][len(pruningPointProof.Headers[0])-1]), nil
+}
+
+func (flow *handleIBDFlow) downloadHeadersAndPruningUTXOSet(
+	syncerHeaderSelectedTipHash, relayBlockHash *externalapi.DomainHash,
+	highBlockDAAScore uint64) error {
+
+	proofPruningPoint, err := flow.syncAndValidatePruningPointProof()
+	if err != nil {
+		return err
+	}
+
+	err = flow.syncPruningPointsAndPruningPointAnticone(proofPruningPoint)
+	if err != nil {
+		return err
+	}
+
+	// TODO: Remove this condition once there's more proper way to check finality violation
+	// in the headers proof.
+	if proofPruningPoint.Equal(flow.Config().NetParams().GenesisHash) {
+		return protocolerrors.Errorf(true, "the genesis pruning point violates finality")
+	}
+
+	err = flow.syncPruningPointFutureHeaders(flow.Domain().StagingConsensus(),
+		syncerHeaderSelectedTipHash, proofPruningPoint, relayBlockHash, highBlockDAAScore)
+	if err != nil {
+		return err
+	}
+
+	log.Infof("Headers downloaded from peer %s", flow.peer)
+
+	relayBlockInfo, err := flow.Domain().StagingConsensus().GetBlockInfo(relayBlockHash)
+	if err != nil {
+		return err
+	}
+
+	if !relayBlockInfo.Exists {
+		return protocolerrors.Errorf(true, "the triggering IBD block was not sent")
+	}
+
+	err = flow.validatePruningPointFutureHeaderTimestamps()
+	if err != nil {
+		return err
+	}
+
+	log.Debugf("Syncing the current pruning point UTXO set")
+	syncedPruningPointUTXOSetSuccessfully, err := flow.syncPruningPointUTXOSet(flow.Domain().StagingConsensus(), proofPruningPoint)
+	if err != nil {
+		return err
+	}
+	if !syncedPruningPointUTXOSetSuccessfully {
+		log.Debugf("Aborting IBD because the pruning point UTXO set failed to sync")
+		return nil
+	}
+	log.Debugf("Finished syncing the current pruning point UTXO set")
+	return nil
+}
+
+func (flow *handleIBDFlow) syncPruningPointsAndPruningPointAnticone(proofPruningPoint *externalapi.DomainHash) error {
+	log.Infof("Downloading the past pruning points and the pruning point anticone from %s", flow.peer)
+	err := flow.outgoingRoute.Enqueue(appmessage.NewMsgRequestPruningPointAndItsAnticone())
+	if err != nil {
+		return err
+	}
+
+	err = flow.validateAndInsertPruningPoints(proofPruningPoint)
+	if err != nil {
+		return err
+	}
+
+	message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
+	if err != nil {
+		return err
+	}
+
+	msgTrustedData, ok := message.(*appmessage.MsgTrustedData)
+	if !ok {
+		return protocolerrors.Errorf(true, "received unexpected message type. "+
+			"expected: %s, got: %s", appmessage.CmdTrustedData, message.Command())
+	}
+
+	pruningPointWithMetaData, done, err := flow.receiveBlockWithTrustedData()
+	if err != nil {
+		return err
+	}
+
+	if done {
+		return protocolerrors.Errorf(true, "got `done` message before receiving the pruning point")
+	}
+
+	if !pruningPointWithMetaData.Block.Header.BlockHash().Equal(proofPruningPoint) {
+		return protocolerrors.Errorf(true, "first block with trusted data is not the pruning point")
+	}
+
+	err = flow.processBlockWithTrustedData(flow.Domain().StagingConsensus(), pruningPointWithMetaData, msgTrustedData)
+	if err != nil {
+		return err
+	}
+
+	i := 0
+	for ; ; i++ {
+		blockWithTrustedData, done, err := flow.receiveBlockWithTrustedData()
+		if err != nil {
+			return err
+		}
+
+		if done {
+			break
+		}
+
+		err = flow.processBlockWithTrustedData(flow.Domain().StagingConsensus(), blockWithTrustedData, msgTrustedData)
+		if err != nil {
+			return err
+		}
+
+		// We're using i+2 because we want to check if the next block will belong to the next batch, but we already downloaded
+		// the pruning point outside the loop so we use i+2 instead of i+1.
+		if (i+2)%ibdBatchSize == 0 {
+			log.Infof("Downloaded %d blocks from the pruning point anticone", i+1)
+			err := flow.outgoingRoute.Enqueue(appmessage.NewMsgRequestNextPruningPointAndItsAnticoneBlocks())
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	log.Infof("Finished downloading pruning point and its anticone from %s. Total blocks downloaded: %d", flow.peer, i+1)
+	return nil
+}
+
+func (flow *handleIBDFlow) processBlockWithTrustedData(
+	consensus externalapi.Consensus, block *appmessage.MsgBlockWithTrustedDataV4, data *appmessage.MsgTrustedData) error {
+
+	blockWithTrustedData := &externalapi.BlockWithTrustedData{
+		Block:        appmessage.MsgBlockToDomainBlock(block.Block),
+		DAAWindow:    make([]*externalapi.TrustedDataDataDAAHeader, 0, len(block.DAAWindowIndices)),
+		GHOSTDAGData: make([]*externalapi.BlockGHOSTDAGDataHashPair, 0, len(block.GHOSTDAGDataIndices)),
+	}
+
+	for _, index := range block.DAAWindowIndices {
+		blockWithTrustedData.DAAWindow = append(blockWithTrustedData.DAAWindow, appmessage.TrustedDataDataDAABlockV4ToTrustedDataDataDAAHeader(data.DAAWindow[index]))
+	}
+
+	for _, index := range block.GHOSTDAGDataIndices {
+		blockWithTrustedData.GHOSTDAGData = append(blockWithTrustedData.GHOSTDAGData, appmessage.GHOSTDAGHashPairToDomainGHOSTDAGHashPair(data.GHOSTDAGData[index]))
+	}
+
+	_, err := consensus.ValidateAndInsertBlockWithTrustedData(blockWithTrustedData, false)
+	return err
+}
+
+func (flow *handleIBDFlow) receiveBlockWithTrustedData() (*appmessage.MsgBlockWithTrustedDataV4, bool, error) {
+	message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
+	if err != nil {
+		return nil, false, err
+	}
+
+	switch downCastedMessage := message.(type) {
+	case *appmessage.MsgBlockWithTrustedDataV4:
+		return downCastedMessage, false, nil
+	case *appmessage.MsgDoneBlocksWithTrustedData:
+		return nil, true, nil
+	default:
+		return nil, false,
+			protocolerrors.Errorf(true, "received unexpected message type. "+
+				"expected: %s or %s, got: %s",
+				(&appmessage.MsgBlockWithTrustedData{}).Command(),
+				(&appmessage.MsgDoneBlocksWithTrustedData{}).Command(),
+				downCastedMessage.Command())
+	}
+}
+
+func (flow *handleIBDFlow) receivePruningPoints() (*appmessage.MsgPruningPoints, error) {
+	message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
+	if err != nil {
+		return nil, err
+	}
+
+	msgPruningPoints, ok := message.(*appmessage.MsgPruningPoints)
+	if !ok {
+		return nil,
+			protocolerrors.Errorf(true, "received unexpected message type. "+
+				"expected: %s, got: %s", appmessage.CmdPruningPoints, message.Command())
+	}
+
+	return msgPruningPoints, nil
+}
+
+func (flow *handleIBDFlow) validateAndInsertPruningPoints(proofPruningPoint *externalapi.DomainHash) error {
+	currentPruningPoint, err := flow.Domain().Consensus().PruningPoint()
+	if err != nil {
+		return err
+	}
+
+	if currentPruningPoint.Equal(proofPruningPoint) {
+		return protocolerrors.Errorf(true, "the proposed pruning point is the same as the current pruning point")
+	}
+
+	pruningPoints, err := flow.receivePruningPoints()
+	if err != nil {
+		return err
+	}
+
+	headers := make([]externalapi.BlockHeader, len(pruningPoints.Headers))
+	for i, header := range pruningPoints.Headers {
+		headers[i] = appmessage.BlockHeaderToDomainBlockHeader(header)
+	}
+
+	arePruningPointsViolatingFinality, err := flow.Domain().Consensus().ArePruningPointsViolatingFinality(headers)
+	if err != nil {
+		return err
+	}
+
+	if arePruningPointsViolatingFinality {
+		// TODO: Find a better way to deal with finality conflicts.
+		return protocolerrors.Errorf(false, "pruning points are violating finality")
+	}
+
+	lastPruningPoint := consensushashing.HeaderHash(headers[len(headers)-1])
+	if !lastPruningPoint.Equal(proofPruningPoint) {
+		return protocolerrors.Errorf(true, "the proof pruning point is not equal to the last pruning "+
+			"point in the list")
+	}
+
+	err = flow.Domain().StagingConsensus().ImportPruningPoints(headers)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (flow *handleIBDFlow) syncPruningPointUTXOSet(consensus externalapi.Consensus,
+	pruningPoint *externalapi.DomainHash) (bool, error) {
+
+	log.Infof("Checking if the suggested pruning point %s is compatible to the node DAG", pruningPoint)
+	isValid, err := flow.Domain().StagingConsensus().IsValidPruningPoint(pruningPoint)
+	if err != nil {
+		return false, err
+	}
+
+	if !isValid {
+		return false, protocolerrors.Errorf(true, "invalid pruning point %s", pruningPoint)
+	}
+
+	log.Info("Fetching the pruning point UTXO set")
+	isSuccessful, err := flow.fetchMissingUTXOSet(consensus, pruningPoint)
+	if err != nil {
+		log.Infof("An error occurred while fetching the pruning point UTXO set. Stopping IBD. (%s)", err)
+		return false, err
+	}
+
+	if !isSuccessful {
+		log.Infof("Couldn't successfully fetch the pruning point UTXO set. Stopping IBD.")
+		return false, nil
+	}
+
+	log.Info("Fetched the new pruning point UTXO set")
+	return true, nil
+}
+
+func (flow *handleIBDFlow) fetchMissingUTXOSet(consensus externalapi.Consensus, pruningPointHash *externalapi.DomainHash) (succeed bool, err error) {
+	defer func() {
+		err := flow.Domain().StagingConsensus().ClearImportedPruningPointData()
+		if err != nil {
+			panic(fmt.Sprintf("failed to clear imported pruning point data: %s", err))
+		}
+	}()
+
+	err = flow.outgoingRoute.Enqueue(appmessage.NewMsgRequestPruningPointUTXOSet(pruningPointHash))
+	if err != nil {
+		return false, err
+	}
+
+	receivedAll, err := flow.receiveAndInsertPruningPointUTXOSet(consensus, pruningPointHash)
+	if err != nil {
+		return false, err
+	}
+	if !receivedAll {
+		return false, nil
+	}
+
+	err = flow.Domain().StagingConsensus().ValidateAndInsertImportedPruningPoint(pruningPointHash)
+	if err != nil {
+		// TODO: Find a better way to deal with finality conflicts.
+		if errors.Is(err, ruleerrors.ErrSuggestedPruningViolatesFinality) {
+			return false, nil
+		}
+		return false, protocolerrors.ConvertToBanningProtocolErrorIfRuleError(err, "error with pruning point UTXO set")
+	}
+
+	return true, nil
+}

app/protocol/flows/v5/blockrelay/log.go

@@ -0,0 +1,9 @@
+package blockrelay
+
+import (
+	"github.com/kaspanet/kaspad/infrastructure/logger"
+	"github.com/kaspanet/kaspad/util/panics"
+)
+
+var log = logger.RegisterSubSystem("PROT")
+var spawn = panics.GoroutineWrapperFunc(log)

app/protocol/flows/v5/blockrelay/send_virtual_selected_parent_inv.go

@@ -0,0 +1,35 @@
+package blockrelay
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	peerpkg "github.com/kaspanet/kaspad/app/protocol/peer"
+	"github.com/kaspanet/kaspad/domain"
+	"github.com/kaspanet/kaspad/infrastructure/config"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+)
+
+// SendVirtualSelectedParentInvContext is the interface for the context needed for the SendVirtualSelectedParentInv flow.
+type SendVirtualSelectedParentInvContext interface {
+	Domain() domain.Domain
+	Config() *config.Config
+}
+
+// SendVirtualSelectedParentInv sends a peer the selected parent hash of the virtual
+func SendVirtualSelectedParentInv(context SendVirtualSelectedParentInvContext,
+	outgoingRoute *router.Route, peer *peerpkg.Peer) error {
+
+	virtualSelectedParent, err := context.Domain().Consensus().GetVirtualSelectedParent()
+	if err != nil {
+		return err
+	}
+
+	if virtualSelectedParent.Equal(context.Config().NetParams().GenesisHash) {
+		log.Debugf("Skipping sending the virtual selected parent hash to peer %s because it's the genesis", peer)
+		return nil
+	}
+
+	log.Debugf("Sending virtual selected parent hash %s to peer %s", virtualSelectedParent, peer)
+
+	virtualSelectedParentInv := appmessage.NewMsgInvBlock(virtualSelectedParent)
+	return outgoingRoute.Enqueue(virtualSelectedParentInv)
+}

app/protocol/flows/v5/ping/receive.go

@@ -0,0 +1,42 @@
+package ping
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+)
+
+// ReceivePingsContext is the interface for the context needed for the ReceivePings flow.
+type ReceivePingsContext interface {
+}
+
+type receivePingsFlow struct {
+	ReceivePingsContext
+	incomingRoute, outgoingRoute *router.Route
+}
+
+// ReceivePings handles all ping messages coming through incomingRoute.
+// This function assumes that incomingRoute will only return MsgPing.
+func ReceivePings(context ReceivePingsContext, incomingRoute *router.Route, outgoingRoute *router.Route) error {
+	flow := &receivePingsFlow{
+		ReceivePingsContext: context,
+		incomingRoute:       incomingRoute,
+		outgoingRoute:       outgoingRoute,
+	}
+	return flow.start()
+}
+
+func (flow *receivePingsFlow) start() error {
+	for {
+		message, err := flow.incomingRoute.Dequeue()
+		if err != nil {
+			return err
+		}
+		pingMessage := message.(*appmessage.MsgPing)
+
+		pongMessage := appmessage.NewMsgPong(pingMessage.Nonce)
+		err = flow.outgoingRoute.Enqueue(pongMessage)
+		if err != nil {
+			return err
+		}
+	}
+}

app/protocol/flows/v5/ping/send.go

@@ -0,0 +1,77 @@
+package ping
+
+import (
+	"github.com/kaspanet/kaspad/app/protocol/common"
+	"github.com/kaspanet/kaspad/app/protocol/flowcontext"
+	"github.com/pkg/errors"
+	"time"
+
+	"github.com/kaspanet/kaspad/app/appmessage"
+	peerpkg "github.com/kaspanet/kaspad/app/protocol/peer"
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+	"github.com/kaspanet/kaspad/util/random"
+)
+
+// SendPingsContext is the interface for the context needed for the SendPings flow.
+type SendPingsContext interface {
+	ShutdownChan() <-chan struct{}
+}
+
+type sendPingsFlow struct {
+	SendPingsContext
+	incomingRoute, outgoingRoute *router.Route
+	peer                         *peerpkg.Peer
+}
+
+// SendPings starts sending MsgPings every pingInterval seconds to the
+// given peer.
+// This function assumes that incomingRoute will only return MsgPong.
+func SendPings(context SendPingsContext, incomingRoute *router.Route, outgoingRoute *router.Route, peer *peerpkg.Peer) error {
+	flow := &sendPingsFlow{
+		SendPingsContext: context,
+		incomingRoute:    incomingRoute,
+		outgoingRoute:    outgoingRoute,
+		peer:             peer,
+	}
+	return flow.start()
+}
+
+func (flow *sendPingsFlow) start() error {
+	const pingInterval = 2 * time.Minute
+	ticker := time.NewTicker(pingInterval)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-flow.ShutdownChan():
+			return nil
+		case <-ticker.C:
+		}
+
+		nonce, err := random.Uint64()
+		if err != nil {
+			return err
+		}
+		flow.peer.SetPingPending(nonce)
+
+		pingMessage := appmessage.NewMsgPing(nonce)
+		err = flow.outgoingRoute.Enqueue(pingMessage)
+		if err != nil {
+			return err
+		}
+
+		message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
+		if err != nil {
+			if errors.Is(err, router.ErrTimeout) {
+				return errors.Wrapf(flowcontext.ErrPingTimeout, err.Error())
+			}
+			return err
+		}
+		pongMessage := message.(*appmessage.MsgPong)
+		if pongMessage.Nonce != pingMessage.Nonce {
+			return protocolerrors.New(true, "nonce mismatch between ping and pong")
+		}
+		flow.peer.SetPingIdle()
+	}
+}

app/protocol/flows/v5/register.go

@@ -0,0 +1,209 @@
+package v5
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/app/protocol/common"
+	"github.com/kaspanet/kaspad/app/protocol/flowcontext"
+	"github.com/kaspanet/kaspad/app/protocol/flows/v5/addressexchange"
+	"github.com/kaspanet/kaspad/app/protocol/flows/v5/blockrelay"
+	"github.com/kaspanet/kaspad/app/protocol/flows/v5/ping"
+	"github.com/kaspanet/kaspad/app/protocol/flows/v5/rejects"
+	"github.com/kaspanet/kaspad/app/protocol/flows/v5/transactionrelay"
+	peerpkg "github.com/kaspanet/kaspad/app/protocol/peer"
+	routerpkg "github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+)
+
+type protocolManager interface {
+	RegisterFlow(name string, router *routerpkg.Router, messageTypes []appmessage.MessageCommand, isStopping *uint32,
+		errChan chan error, initializeFunc common.FlowInitializeFunc) *common.Flow
+	RegisterOneTimeFlow(name string, router *routerpkg.Router, messageTypes []appmessage.MessageCommand,
+		isStopping *uint32, stopChan chan error, initializeFunc common.FlowInitializeFunc) *common.Flow
+	RegisterFlowWithCapacity(name string, capacity int, router *routerpkg.Router,
+		messageTypes []appmessage.MessageCommand, isStopping *uint32,
+		errChan chan error, initializeFunc common.FlowInitializeFunc) *common.Flow
+	Context() *flowcontext.FlowContext
+}
+
+// Register is used in order to register all the protocol flows to the given router.
+func Register(m protocolManager, router *routerpkg.Router, errChan chan error, isStopping *uint32) (flows []*common.Flow) {
+	flows = registerAddressFlows(m, router, isStopping, errChan)
+	flows = append(flows, registerBlockRelayFlows(m, router, isStopping, errChan)...)
+	flows = append(flows, registerPingFlows(m, router, isStopping, errChan)...)
+	flows = append(flows, registerTransactionRelayFlow(m, router, isStopping, errChan)...)
+	flows = append(flows, registerRejectsFlow(m, router, isStopping, errChan)...)
+
+	return flows
+}
+
+func registerAddressFlows(m protocolManager, router *routerpkg.Router, isStopping *uint32, errChan chan error) []*common.Flow {
+	outgoingRoute := router.OutgoingRoute()
+
+	return []*common.Flow{
+		m.RegisterFlow("SendAddresses", router, []appmessage.MessageCommand{appmessage.CmdRequestAddresses}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return addressexchange.SendAddresses(m.Context(), incomingRoute, outgoingRoute)
+			},
+		),
+
+		m.RegisterOneTimeFlow("ReceiveAddresses", router, []appmessage.MessageCommand{appmessage.CmdAddresses}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return addressexchange.ReceiveAddresses(m.Context(), incomingRoute, outgoingRoute, peer)
+			},
+		),
+	}
+}
+
+func registerBlockRelayFlows(m protocolManager, router *routerpkg.Router, isStopping *uint32, errChan chan error) []*common.Flow {
+	outgoingRoute := router.OutgoingRoute()
+
+	return []*common.Flow{
+		m.RegisterOneTimeFlow("SendVirtualSelectedParentInv", router, []appmessage.MessageCommand{},
+			isStopping, errChan, func(route *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.SendVirtualSelectedParentInv(m.Context(), outgoingRoute, peer)
+			}),
+
+		m.RegisterFlow("HandleRelayInvs", router, []appmessage.MessageCommand{
+			appmessage.CmdInvRelayBlock, appmessage.CmdBlock, appmessage.CmdBlockLocator,
+		},
+			isStopping, errChan, func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandleRelayInvs(m.Context(), incomingRoute,
+					outgoingRoute, peer)
+			},
+		),
+
+		m.RegisterFlow("HandleIBD", router, []appmessage.MessageCommand{
+			appmessage.CmdDoneHeaders, appmessage.CmdUnexpectedPruningPoint, appmessage.CmdPruningPointUTXOSetChunk,
+			appmessage.CmdBlockHeaders, appmessage.CmdIBDBlockLocatorHighestHash, appmessage.CmdBlockWithTrustedDataV4,
+			appmessage.CmdDoneBlocksWithTrustedData, appmessage.CmdIBDBlockLocatorHighestHashNotFound,
+			appmessage.CmdDonePruningPointUTXOSetChunks, appmessage.CmdIBDBlock, appmessage.CmdPruningPoints,
+			appmessage.CmdPruningPointProof,
+			appmessage.CmdTrustedData,
+			appmessage.CmdIBDChainBlockLocator,
+		},
+			isStopping, errChan, func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandleIBD(m.Context(), incomingRoute,
+					outgoingRoute, peer)
+			},
+		),
+
+		m.RegisterFlow("HandleRelayBlockRequests", router, []appmessage.MessageCommand{appmessage.CmdRequestRelayBlocks}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandleRelayBlockRequests(m.Context(), incomingRoute, outgoingRoute, peer)
+			},
+		),
+
+		m.RegisterFlow("HandleRequestBlockLocator", router,
+			[]appmessage.MessageCommand{appmessage.CmdRequestBlockLocator}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandleRequestBlockLocator(m.Context(), incomingRoute, outgoingRoute)
+			},
+		),
+
+		m.RegisterFlow("HandleRequestHeaders", router,
+			[]appmessage.MessageCommand{appmessage.CmdRequestHeaders, appmessage.CmdRequestNextHeaders}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandleRequestHeaders(m.Context(), incomingRoute, outgoingRoute, peer)
+			},
+		),
+
+		m.RegisterFlow("HandleIBDBlockRequests", router,
+			[]appmessage.MessageCommand{appmessage.CmdRequestIBDBlocks}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandleIBDBlockRequests(m.Context(), incomingRoute, outgoingRoute)
+			},
+		),
+
+		m.RegisterFlow("HandleRequestPruningPointUTXOSet", router,
+			[]appmessage.MessageCommand{appmessage.CmdRequestPruningPointUTXOSet,
+				appmessage.CmdRequestNextPruningPointUTXOSetChunk}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandleRequestPruningPointUTXOSet(m.Context(), incomingRoute, outgoingRoute)
+			},
+		),
+
+		m.RegisterFlow("HandlePruningPointAndItsAnticoneRequests", router,
+			[]appmessage.MessageCommand{appmessage.CmdRequestPruningPointAndItsAnticone, appmessage.CmdRequestNextPruningPointAndItsAnticoneBlocks}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandlePruningPointAndItsAnticoneRequests(m.Context(), incomingRoute, outgoingRoute, peer)
+			},
+		),
+
+		m.RegisterFlow("HandleIBDBlockLocator", router,
+			[]appmessage.MessageCommand{appmessage.CmdIBDBlockLocator}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandleIBDBlockLocator(m.Context(), incomingRoute, outgoingRoute, peer)
+			},
+		),
+
+		m.RegisterFlow("HandleRequestIBDChainBlockLocator", router,
+			[]appmessage.MessageCommand{appmessage.CmdRequestIBDChainBlockLocator}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandleRequestIBDChainBlockLocator(m.Context(), incomingRoute, outgoingRoute)
+			},
+		),
+
+		m.RegisterFlow("HandleRequestAnticone", router,
+			[]appmessage.MessageCommand{appmessage.CmdRequestAnticone}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandleRequestAnticone(m.Context(), incomingRoute, outgoingRoute, peer)
+			},
+		),
+
+		m.RegisterFlow("HandlePruningPointProofRequests", router,
+			[]appmessage.MessageCommand{appmessage.CmdRequestPruningPointProof}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return blockrelay.HandlePruningPointProofRequests(m.Context(), incomingRoute, outgoingRoute, peer)
+			},
+		),
+	}
+}
+
+func registerPingFlows(m protocolManager, router *routerpkg.Router, isStopping *uint32, errChan chan error) []*common.Flow {
+	outgoingRoute := router.OutgoingRoute()
+
+	return []*common.Flow{
+		m.RegisterFlow("ReceivePings", router, []appmessage.MessageCommand{appmessage.CmdPing}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return ping.ReceivePings(m.Context(), incomingRoute, outgoingRoute)
+			},
+		),
+
+		m.RegisterFlow("SendPings", router, []appmessage.MessageCommand{appmessage.CmdPong}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return ping.SendPings(m.Context(), incomingRoute, outgoingRoute, peer)
+			},
+		),
+	}
+}
+
+func registerTransactionRelayFlow(m protocolManager, router *routerpkg.Router, isStopping *uint32, errChan chan error) []*common.Flow {
+	outgoingRoute := router.OutgoingRoute()
+
+	return []*common.Flow{
+		m.RegisterFlowWithCapacity("HandleRelayedTransactions", 10_000, router,
+			[]appmessage.MessageCommand{appmessage.CmdInvTransaction, appmessage.CmdTx, appmessage.CmdTransactionNotFound}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return transactionrelay.HandleRelayedTransactions(m.Context(), incomingRoute, outgoingRoute)
+			},
+		),
+		m.RegisterFlow("HandleRequestTransactions", router,
+			[]appmessage.MessageCommand{appmessage.CmdRequestTransactions}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return transactionrelay.HandleRequestedTransactions(m.Context(), incomingRoute, outgoingRoute)
+			},
+		),
+	}
+}
+
+func registerRejectsFlow(m protocolManager, router *routerpkg.Router, isStopping *uint32, errChan chan error) []*common.Flow {
+	outgoingRoute := router.OutgoingRoute()
+
+	return []*common.Flow{
+		m.RegisterFlow("HandleRejects", router,
+			[]appmessage.MessageCommand{appmessage.CmdReject}, isStopping, errChan,
+			func(incomingRoute *routerpkg.Route, peer *peerpkg.Peer) error {
+				return rejects.HandleRejects(m.Context(), incomingRoute, outgoingRoute)
+			},
+		),
+	}
+}

app/protocol/flows/v5/rejects/handle_rejects.go

@@ -0,0 +1,37 @@
+package rejects
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+)
+
+// HandleRejectsContext is the interface for the context needed for the HandleRejects flow.
+type HandleRejectsContext interface {
+}
+
+type handleRejectsFlow struct {
+	HandleRejectsContext
+	incomingRoute, outgoingRoute *router.Route
+}
+
+// HandleRejects handles all reject messages coming through incomingRoute.
+// This function assumes that incomingRoute will only return MsgReject.
+func HandleRejects(context HandleRejectsContext, incomingRoute *router.Route, outgoingRoute *router.Route) error {
+	flow := &handleRejectsFlow{
+		HandleRejectsContext: context,
+		incomingRoute:        incomingRoute,
+		outgoingRoute:        outgoingRoute,
+	}
+	return flow.start()
+}
+
+func (flow *handleRejectsFlow) start() error {
+	message, err := flow.incomingRoute.Dequeue()
+	if err != nil {
+		return err
+	}
+	rejectMessage := message.(*appmessage.MsgReject)
+
+	return protocolerrors.Errorf(false, "got reject message: `%s`", rejectMessage.Reason)
+}

app/protocol/flows/v5/testing/common_test.go

@@ -0,0 +1,24 @@
+package testing
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/pkg/errors"
+)
+
+func checkFlowError(t *testing.T, err error, isProtocolError bool, shouldBan bool, contains string) {
+	pErr := protocolerrors.ProtocolError{}
+	if errors.As(err, &pErr) != isProtocolError {
+		t.Fatalf("Unexepcted error %+v", err)
+	}
+
+	if pErr.ShouldBan != shouldBan {
+		t.Fatalf("Exepcted shouldBan %t but got %t", shouldBan, pErr.ShouldBan)
+	}
+
+	if !strings.Contains(err.Error(), contains) {
+		t.Fatalf("Unexpected error. Expected error to contain '%s' but got: %+v", contains, err)
+	}
+}

app/protocol/flows/v5/testing/receiveaddresses_test.go

@@ -0,0 +1,51 @@
+package testing
+
+import (
+	"github.com/kaspanet/kaspad/app/protocol/flows/v5/addressexchange"
+	"testing"
+	"time"
+
+	"github.com/kaspanet/kaspad/app/appmessage"
+	peerpkg "github.com/kaspanet/kaspad/app/protocol/peer"
+	"github.com/kaspanet/kaspad/domain/consensus"
+	"github.com/kaspanet/kaspad/domain/consensus/utils/testutils"
+	"github.com/kaspanet/kaspad/infrastructure/network/addressmanager"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+)
+
+type fakeReceiveAddressesContext struct{}
+
+func (f fakeReceiveAddressesContext) AddressManager() *addressmanager.AddressManager {
+	return nil
+}
+
+func TestReceiveAddressesErrors(t *testing.T) {
+	testutils.ForAllNets(t, true, func(t *testing.T, consensusConfig *consensus.Config) {
+		incomingRoute := router.NewRoute("incoming")
+		outgoingRoute := router.NewRoute("outgoing")
+		peer := peerpkg.New(nil)
+		errChan := make(chan error)
+		go func() {
+			errChan <- addressexchange.ReceiveAddresses(fakeReceiveAddressesContext{}, incomingRoute, outgoingRoute, peer)
+		}()
+
+		_, err := outgoingRoute.DequeueWithTimeout(time.Second)
+		if err != nil {
+			t.Fatalf("DequeueWithTimeout: %+v", err)
+		}
+
+		// Sending addressmanager.GetAddressesMax+1 addresses should trigger a ban
+		err = incomingRoute.Enqueue(appmessage.NewMsgAddresses(make([]*appmessage.NetAddress,
+			addressmanager.GetAddressesMax+1)))
+		if err != nil {
+			t.Fatalf("Enqueue: %+v", err)
+		}
+
+		select {
+		case err := <-errChan:
+			checkFlowError(t, err, true, true, "address count exceeded")
+		case <-time.After(time.Second):
+			t.Fatalf("timed out after %s", time.Second)
+		}
+	})
+}

app/protocol/flows/v5/testing/testing.go

@@ -0,0 +1,4 @@
+package testing
+
+// Because of a bug in Go coverage fails if you have packages with test files only. See https://github.com/golang/go/issues/27333
+// So this is a dummy non-test go file in the package.

app/protocol/flows/v5/transactionrelay/handle_relayed_transactions.go

@@ -0,0 +1,209 @@
+package transactionrelay
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/app/protocol/common"
+	"github.com/kaspanet/kaspad/app/protocol/flowcontext"
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/domain"
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+	"github.com/kaspanet/kaspad/domain/consensus/utils/consensushashing"
+	"github.com/kaspanet/kaspad/domain/miningmanager/mempool"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+	"github.com/pkg/errors"
+)
+
+// TransactionsRelayContext is the interface for the context needed for the
+// HandleRelayedTransactions and HandleRequestedTransactions flows.
+type TransactionsRelayContext interface {
+	NetAdapter() *netadapter.NetAdapter
+	Domain() domain.Domain
+	SharedRequestedTransactions() *flowcontext.SharedRequestedTransactions
+	OnTransactionAddedToMempool()
+	EnqueueTransactionIDsForPropagation(transactionIDs []*externalapi.DomainTransactionID) error
+	IsIBDRunning() bool
+}
+
+type handleRelayedTransactionsFlow struct {
+	TransactionsRelayContext
+	incomingRoute, outgoingRoute *router.Route
+	invsQueue                    []*appmessage.MsgInvTransaction
+}
+
+// HandleRelayedTransactions listens to appmessage.MsgInvTransaction messages, requests their corresponding transactions if they
+// are missing, adds them to the mempool and propagates them to the rest of the network.
+func HandleRelayedTransactions(context TransactionsRelayContext, incomingRoute *router.Route, outgoingRoute *router.Route) error {
+	flow := &handleRelayedTransactionsFlow{
+		TransactionsRelayContext: context,
+		incomingRoute:            incomingRoute,
+		outgoingRoute:            outgoingRoute,
+		invsQueue:                make([]*appmessage.MsgInvTransaction, 0),
+	}
+	return flow.start()
+}
+
+func (flow *handleRelayedTransactionsFlow) start() error {
+	for {
+		inv, err := flow.readInv()
+		if err != nil {
+			return err
+		}
+
+		if flow.IsIBDRunning() {
+			continue
+		}
+
+		requestedIDs, err := flow.requestInvTransactions(inv)
+		if err != nil {
+			return err
+		}
+
+		err = flow.receiveTransactions(requestedIDs)
+		if err != nil {
+			return err
+		}
+	}
+}
+
+func (flow *handleRelayedTransactionsFlow) requestInvTransactions(
+	inv *appmessage.MsgInvTransaction) (requestedIDs []*externalapi.DomainTransactionID, err error) {
+
+	idsToRequest := make([]*externalapi.DomainTransactionID, 0, len(inv.TxIDs))
+	for _, txID := range inv.TxIDs {
+		if flow.isKnownTransaction(txID) {
+			continue
+		}
+		exists := flow.SharedRequestedTransactions().AddIfNotExists(txID)
+		if exists {
+			continue
+		}
+		idsToRequest = append(idsToRequest, txID)
+	}
+
+	if len(idsToRequest) == 0 {
+		return idsToRequest, nil
+	}
+
+	msgGetTransactions := appmessage.NewMsgRequestTransactions(idsToRequest)
+	err = flow.outgoingRoute.Enqueue(msgGetTransactions)
+	if err != nil {
+		flow.SharedRequestedTransactions().RemoveMany(idsToRequest)
+		return nil, err
+	}
+	return idsToRequest, nil
+}
+
+func (flow *handleRelayedTransactionsFlow) isKnownTransaction(txID *externalapi.DomainTransactionID) bool {
+	// Ask the transaction memory pool if the transaction is known
+	// to it in any form (main pool or orphan).
+	if _, ok := flow.Domain().MiningManager().GetTransaction(txID); ok {
+		return true
+	}
+
+	return false
+}
+
+func (flow *handleRelayedTransactionsFlow) readInv() (*appmessage.MsgInvTransaction, error) {
+	if len(flow.invsQueue) > 0 {
+		var inv *appmessage.MsgInvTransaction
+		inv, flow.invsQueue = flow.invsQueue[0], flow.invsQueue[1:]
+		return inv, nil
+	}
+
+	msg, err := flow.incomingRoute.Dequeue()
+	if err != nil {
+		return nil, err
+	}
+
+	inv, ok := msg.(*appmessage.MsgInvTransaction)
+	if !ok {
+		return nil, protocolerrors.Errorf(true, "unexpected %s message in the block relay flow while "+
+			"expecting an inv message", msg.Command())
+	}
+	return inv, nil
+}
+
+func (flow *handleRelayedTransactionsFlow) broadcastAcceptedTransactions(acceptedTxIDs []*externalapi.DomainTransactionID) error {
+	return flow.EnqueueTransactionIDsForPropagation(acceptedTxIDs)
+}
+
+// readMsgTxOrNotFound returns the next msgTx or msgTransactionNotFound in incomingRoute,
+// returning only one of the message types at a time.
+//
+// and populates invsQueue with any inv messages that meanwhile arrive.
+func (flow *handleRelayedTransactionsFlow) readMsgTxOrNotFound() (
+	msgTx *appmessage.MsgTx, msgNotFound *appmessage.MsgTransactionNotFound, err error) {
+
+	for {
+		message, err := flow.incomingRoute.DequeueWithTimeout(common.DefaultTimeout)
+		if err != nil {
+			return nil, nil, err
+		}
+
+		switch message := message.(type) {
+		case *appmessage.MsgInvTransaction:
+			flow.invsQueue = append(flow.invsQueue, message)
+		case *appmessage.MsgTx:
+			return message, nil, nil
+		case *appmessage.MsgTransactionNotFound:
+			return nil, message, nil
+		default:
+			return nil, nil, errors.Errorf("unexpected message %s", message.Command())
+		}
+	}
+}
+
+func (flow *handleRelayedTransactionsFlow) receiveTransactions(requestedTransactions []*externalapi.DomainTransactionID) error {
+	// In case the function returns earlier than expected, we want to make sure sharedRequestedTransactions is
+	// clean from any pending transactions.
+	defer flow.SharedRequestedTransactions().RemoveMany(requestedTransactions)
+	for _, expectedID := range requestedTransactions {
+		msgTx, msgTxNotFound, err := flow.readMsgTxOrNotFound()
+		if err != nil {
+			return err
+		}
+		if msgTxNotFound != nil {
+			if !msgTxNotFound.ID.Equal(expectedID) {
+				return protocolerrors.Errorf(true, "expected transaction %s, but got %s",
+					expectedID, msgTxNotFound.ID)
+			}
+
+			continue
+		}
+		tx := appmessage.MsgTxToDomainTransaction(msgTx)
+		txID := consensushashing.TransactionID(tx)
+		if !txID.Equal(expectedID) {
+			return protocolerrors.Errorf(true, "expected transaction %s, but got %s",
+				expectedID, txID)
+		}
+
+		acceptedTransactions, err :=
+			flow.Domain().MiningManager().ValidateAndInsertTransaction(tx, false, true)
+		if err != nil {
+			ruleErr := &mempool.RuleError{}
+			if !errors.As(err, ruleErr) {
+				return errors.Wrapf(err, "failed to process transaction %s", txID)
+			}
+
+			shouldBan := false
+			if txRuleErr := (&mempool.TxRuleError{}); errors.As(ruleErr.Err, txRuleErr) {
+				if txRuleErr.RejectCode == mempool.RejectInvalid {
+					shouldBan = true
+				}
+			}
+
+			if !shouldBan {
+				continue
+			}
+
+			return protocolerrors.Errorf(true, "rejected transaction %s: %s", txID, ruleErr)
+		}
+		err = flow.broadcastAcceptedTransactions(consensushashing.TransactionIDs(acceptedTransactions))
+		if err != nil {
+			return err
+		}
+		flow.OnTransactionAddedToMempool()
+	}
+	return nil
+}

app/protocol/flows/v5/transactionrelay/handle_relayed_transactions_test.go

@@ -0,0 +1,196 @@
+package transactionrelay_test
+
+import (
+	"errors"
+	"github.com/kaspanet/kaspad/app/protocol/flowcontext"
+	"github.com/kaspanet/kaspad/app/protocol/flows/v5/transactionrelay"
+	"strings"
+	"testing"
+
+	"github.com/kaspanet/kaspad/app/protocol/protocolerrors"
+	"github.com/kaspanet/kaspad/domain"
+	"github.com/kaspanet/kaspad/domain/consensus"
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+	"github.com/kaspanet/kaspad/domain/consensus/utils/testutils"
+	"github.com/kaspanet/kaspad/domain/miningmanager/mempool"
+	"github.com/kaspanet/kaspad/infrastructure/logger"
+	"github.com/kaspanet/kaspad/util/panics"
+
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/infrastructure/config"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+)
+
+type mocTransactionsRelayContext struct {
+	netAdapter                  *netadapter.NetAdapter
+	domain                      domain.Domain
+	sharedRequestedTransactions *flowcontext.SharedRequestedTransactions
+}
+
+func (m *mocTransactionsRelayContext) NetAdapter() *netadapter.NetAdapter {
+	return m.netAdapter
+}
+
+func (m *mocTransactionsRelayContext) Domain() domain.Domain {
+	return m.domain
+}
+
+func (m *mocTransactionsRelayContext) SharedRequestedTransactions() *flowcontext.SharedRequestedTransactions {
+	return m.sharedRequestedTransactions
+}
+
+func (m *mocTransactionsRelayContext) EnqueueTransactionIDsForPropagation(transactionIDs []*externalapi.DomainTransactionID) error {
+	return nil
+}
+
+func (m *mocTransactionsRelayContext) OnTransactionAddedToMempool() {
+}
+
+func (m *mocTransactionsRelayContext) IsIBDRunning() bool {
+	return false
+}
+
+// TestHandleRelayedTransactionsNotFound tests the flow of  HandleRelayedTransactions when the peer doesn't
+// have the requested transactions in the mempool.
+func TestHandleRelayedTransactionsNotFound(t *testing.T) {
+	testutils.ForAllNets(t, true, func(t *testing.T, consensusConfig *consensus.Config) {
+
+		var log = logger.RegisterSubSystem("PROT")
+		var spawn = panics.GoroutineWrapperFunc(log)
+		factory := consensus.NewFactory()
+		tc, teardown, err := factory.NewTestConsensus(consensusConfig, "TestHandleRelayedTransactionsNotFound")
+		if err != nil {
+			t.Fatalf("Error setting up test consensus: %+v", err)
+		}
+		defer teardown(false)
+
+		sharedRequestedTransactions := flowcontext.NewSharedRequestedTransactions()
+		adapter, err := netadapter.NewNetAdapter(config.DefaultConfig())
+		if err != nil {
+			t.Fatalf("Failed to create a NetAdapter: %v", err)
+		}
+		domainInstance, err := domain.New(consensusConfig, mempool.DefaultConfig(&consensusConfig.Params), tc.Database())
+		if err != nil {
+			t.Fatalf("Failed to set up a domain instance: %v", err)
+		}
+		context := &mocTransactionsRelayContext{
+			netAdapter:                  adapter,
+			domain:                      domainInstance,
+			sharedRequestedTransactions: sharedRequestedTransactions,
+		}
+		incomingRoute := router.NewRoute("incoming")
+		defer incomingRoute.Close()
+		peerIncomingRoute := router.NewRoute("outgoing")
+		defer peerIncomingRoute.Close()
+
+		txID1 := externalapi.NewDomainTransactionIDFromByteArray(&[externalapi.DomainHashSize]byte{
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01})
+		txID2 := externalapi.NewDomainTransactionIDFromByteArray(&[externalapi.DomainHashSize]byte{
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02})
+		txIDs := []*externalapi.DomainTransactionID{txID1, txID2}
+		invMessage := appmessage.NewMsgInvTransaction(txIDs)
+		err = incomingRoute.Enqueue(invMessage)
+		if err != nil {
+			t.Fatalf("Unexpected error from incomingRoute.Enqueue: %v", err)
+		}
+		// The goroutine is representing the peer's actions.
+		spawn("peerResponseToTheTransactionsRequest", func() {
+			msg, err := peerIncomingRoute.Dequeue()
+			if err != nil {
+				t.Fatalf("Dequeue: %v", err)
+			}
+			inv := msg.(*appmessage.MsgRequestTransactions)
+
+			if len(txIDs) != len(inv.IDs) {
+				t.Fatalf("TestHandleRelayedTransactions: expected %d transactions ID, but got %d", len(txIDs), len(inv.IDs))
+			}
+
+			for i, id := range inv.IDs {
+				if txIDs[i].String() != id.String() {
+					t.Fatalf("TestHandleRelayedTransactions: expected equal txID: expected %s, but got %s", txIDs[i].String(), id.String())
+				}
+				err = incomingRoute.Enqueue(appmessage.NewMsgTransactionNotFound(txIDs[i]))
+				if err != nil {
+					t.Fatalf("Unexpected error from incomingRoute.Enqueue: %v", err)
+				}
+			}
+			// Insert an unexpected message type to stop the infinity loop.
+			err = incomingRoute.Enqueue(&appmessage.MsgAddresses{})
+			if err != nil {
+				t.Fatalf("Unexpected error from incomingRoute.Enqueue: %v", err)
+			}
+		})
+
+		err = transactionrelay.HandleRelayedTransactions(context, incomingRoute, peerIncomingRoute)
+		// Since we inserted an unexpected message type to stop the infinity loop,
+		// we expect the error will be infected from this specific message and also the
+		// error will count as a protocol message.
+		if protocolErr := (protocolerrors.ProtocolError{}); err == nil || !errors.As(err, &protocolErr) {
+			t.Fatalf("Expected to protocol error")
+		} else {
+			if !protocolErr.ShouldBan {
+				t.Fatalf("Exepcted shouldBan true, but got false.")
+			}
+			if !strings.Contains(err.Error(), "unexpected Addresses [code 3] message in the block relay flow while expecting an inv message") {
+				t.Fatalf("Unexpected error: expected: an error due to existence of an Addresses message "+
+					"in the block relay flow, but got: %v", protocolErr.Cause)
+			}
+		}
+	})
+}
+
+// TestOnClosedIncomingRoute verifies that an appropriate error message will be returned when
+// trying to dequeue a message from a closed route.
+func TestOnClosedIncomingRoute(t *testing.T) {
+	testutils.ForAllNets(t, true, func(t *testing.T, consensusConfig *consensus.Config) {
+
+		factory := consensus.NewFactory()
+		tc, teardown, err := factory.NewTestConsensus(consensusConfig, "TestOnClosedIncomingRoute")
+		if err != nil {
+			t.Fatalf("Error setting up test consensus: %+v", err)
+		}
+		defer teardown(false)
+
+		sharedRequestedTransactions := flowcontext.NewSharedRequestedTransactions()
+		adapter, err := netadapter.NewNetAdapter(config.DefaultConfig())
+		if err != nil {
+			t.Fatalf("Failed to creat a NetAdapter : %v", err)
+		}
+		domainInstance, err := domain.New(consensusConfig, mempool.DefaultConfig(&consensusConfig.Params), tc.Database())
+		if err != nil {
+			t.Fatalf("Failed to set up a domain instance: %v", err)
+		}
+		context := &mocTransactionsRelayContext{
+			netAdapter:                  adapter,
+			domain:                      domainInstance,
+			sharedRequestedTransactions: sharedRequestedTransactions,
+		}
+		incomingRoute := router.NewRoute("incoming")
+		outgoingRoute := router.NewRoute("outgoing")
+		defer outgoingRoute.Close()
+
+		txID := externalapi.NewDomainTransactionIDFromByteArray(&[externalapi.DomainHashSize]byte{
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01})
+		txIDs := []*externalapi.DomainTransactionID{txID}
+
+		err = incomingRoute.Enqueue(&appmessage.MsgInvTransaction{TxIDs: txIDs})
+		if err != nil {
+			t.Fatalf("Unexpected error from incomingRoute.Enqueue: %v", err)
+		}
+		incomingRoute.Close()
+		err = transactionrelay.HandleRelayedTransactions(context, incomingRoute, outgoingRoute)
+		if err == nil || !errors.Is(err, router.ErrRouteClosed) {
+			t.Fatalf("Unexpected error: expected: %v, got : %v", router.ErrRouteClosed, err)
+		}
+	})
+}

app/protocol/flows/v5/transactionrelay/handle_requested_transactions.go

@@ -0,0 +1,59 @@
+package transactionrelay
+
+import (
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+)
+
+type handleRequestedTransactionsFlow struct {
+	TransactionsRelayContext
+	incomingRoute, outgoingRoute *router.Route
+}
+
+// HandleRequestedTransactions listens to appmessage.MsgRequestTransactions messages, responding with the requested
+// transactions if those are in the mempool.
+// Missing transactions would be ignored
+func HandleRequestedTransactions(context TransactionsRelayContext, incomingRoute *router.Route, outgoingRoute *router.Route) error {
+	flow := &handleRequestedTransactionsFlow{
+		TransactionsRelayContext: context,
+		incomingRoute:            incomingRoute,
+		outgoingRoute:            outgoingRoute,
+	}
+	return flow.start()
+}
+
+func (flow *handleRequestedTransactionsFlow) start() error {
+	for {
+		msgRequestTransactions, err := flow.readRequestTransactions()
+		if err != nil {
+			return err
+		}
+
+		for _, transactionID := range msgRequestTransactions.IDs {
+			tx, ok := flow.Domain().MiningManager().GetTransaction(transactionID)
+
+			if !ok {
+				msgTransactionNotFound := appmessage.NewMsgTransactionNotFound(transactionID)
+				err := flow.outgoingRoute.Enqueue(msgTransactionNotFound)
+				if err != nil {
+					return err
+				}
+				continue
+			}
+
+			err := flow.outgoingRoute.Enqueue(appmessage.DomainTransactionToMsgTx(tx))
+			if err != nil {
+				return err
+			}
+		}
+	}
+}
+
+func (flow *handleRequestedTransactionsFlow) readRequestTransactions() (*appmessage.MsgRequestTransactions, error) {
+	msg, err := flow.incomingRoute.Dequeue()
+	if err != nil {
+		return nil, err
+	}
+
+	return msg.(*appmessage.MsgRequestTransactions), nil
+}

app/protocol/flows/v5/transactionrelay/handle_requested_transactions_test.go

@@ -0,0 +1,91 @@
+package transactionrelay_test
+
+import (
+	"github.com/kaspanet/kaspad/app/protocol/flowcontext"
+	"github.com/kaspanet/kaspad/app/protocol/flows/v5/transactionrelay"
+	"testing"
+
+	"github.com/kaspanet/kaspad/app/appmessage"
+	"github.com/kaspanet/kaspad/domain"
+	"github.com/kaspanet/kaspad/domain/consensus"
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+	"github.com/kaspanet/kaspad/domain/consensus/utils/testutils"
+	"github.com/kaspanet/kaspad/domain/miningmanager/mempool"
+	"github.com/kaspanet/kaspad/infrastructure/config"
+	"github.com/kaspanet/kaspad/infrastructure/logger"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter"
+	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"
+	"github.com/kaspanet/kaspad/util/panics"
+	"github.com/pkg/errors"
+)
+
+// TestHandleRequestedTransactionsNotFound tests the flow of  HandleRequestedTransactions
+// when the requested transactions don't found in the mempool.
+func TestHandleRequestedTransactionsNotFound(t *testing.T) {
+	testutils.ForAllNets(t, true, func(t *testing.T, consensusConfig *consensus.Config) {
+		var log = logger.RegisterSubSystem("PROT")
+		var spawn = panics.GoroutineWrapperFunc(log)
+		factory := consensus.NewFactory()
+		tc, teardown, err := factory.NewTestConsensus(consensusConfig, "TestHandleRequestedTransactionsNotFound")
+		if err != nil {
+			t.Fatalf("Error setting up test Consensus: %+v", err)
+		}
+		defer teardown(false)
+
+		sharedRequestedTransactions := flowcontext.NewSharedRequestedTransactions()
+		adapter, err := netadapter.NewNetAdapter(config.DefaultConfig())
+		if err != nil {
+			t.Fatalf("Failed to create a NetAdapter: %v", err)
+		}
+		domainInstance, err := domain.New(consensusConfig, mempool.DefaultConfig(&consensusConfig.Params), tc.Database())
+		if err != nil {
+			t.Fatalf("Failed to set up a domain Instance: %v", err)
+		}
+		context := &mocTransactionsRelayContext{
+			netAdapter:                  adapter,
+			domain:                      domainInstance,
+			sharedRequestedTransactions: sharedRequestedTransactions,
+		}
+		incomingRoute := router.NewRoute("incoming")
+		outgoingRoute := router.NewRoute("outgoing")
+		defer outgoingRoute.Close()
+
+		txID1 := externalapi.NewDomainTransactionIDFromByteArray(&[externalapi.DomainHashSize]byte{
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01})
+		txID2 := externalapi.NewDomainTransactionIDFromByteArray(&[externalapi.DomainHashSize]byte{
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02})
+		txIDs := []*externalapi.DomainTransactionID{txID1, txID2}
+		msg := appmessage.NewMsgRequestTransactions(txIDs)
+		err = incomingRoute.Enqueue(msg)
+		if err != nil {
+			t.Fatalf("Unexpected error from incomingRoute.Enqueue: %v", err)
+		}
+		// The goroutine is representing the peer's actions.
+		spawn("peerResponseToTheTransactionsMessages", func() {
+			for i, id := range txIDs {
+				msg, err := outgoingRoute.Dequeue()
+				if err != nil {
+					t.Fatalf("Dequeue: %s", err)
+				}
+				outMsg := msg.(*appmessage.MsgTransactionNotFound)
+				if txIDs[i].String() != outMsg.ID.String() {
+					t.Fatalf("TestHandleRelayedTransactions: expected equal txID: expected %s, but got %s", txIDs[i].String(), id.String())
+				}
+			}
+			// Closed the incomingRoute for stop the infinity loop.
+			incomingRoute.Close()
+		})
+
+		err = transactionrelay.HandleRequestedTransactions(context, incomingRoute, outgoingRoute)
+		// Make sure the error is due to the closed route.
+		if err == nil || !errors.Is(err, router.ErrRouteClosed) {
+			t.Fatalf("Unexpected error: expected: %v, got : %v", router.ErrRouteClosed, err)
+		}
+	})
+}

app/protocol/manager.go

@@ -2,6 +2,7 @@ package protocol
 
 import (
 	"fmt"
+	"github.com/kaspanet/kaspad/app/protocol/common"
 	"sync"
 	"sync/atomic"
 
@@ -71,11 +72,16 @@ func (m *Manager) AddBlock(block *externalapi.DomainBlock) error {
 	return m.context.AddBlock(block)
 }
 
-func (m *Manager) runFlows(flows []*flow, peer *peerpkg.Peer, errChan <-chan error, flowsWaitGroup *sync.WaitGroup) error {
+// Context returns the manager's flow context
+func (m *Manager) Context() *flowcontext.FlowContext {
+	return m.context
+}
+
+func (m *Manager) runFlows(flows []*common.Flow, peer *peerpkg.Peer, errChan <-chan error, flowsWaitGroup *sync.WaitGroup) error {
 	flowsWaitGroup.Add(len(flows))
 	for _, flow := range flows {
-		executeFunc := flow.executeFunc // extract to new variable so that it's not overwritten
-		spawn(fmt.Sprintf("flow-%s", flow.name), func() {
+		executeFunc := flow.ExecuteFunc // extract to new variable so that it's not overwritten
+		spawn(fmt.Sprintf("flow-%s", flow.Name), func() {
 			executeFunc(peer)
 			flowsWaitGroup.Done()
 		})
@@ -84,6 +90,11 @@ func (m *Manager) runFlows(flows []*flow, peer *peerpkg.Peer, errChan <-chan err
 	return <-errChan
 }
 
+// SetOnVirtualChange sets the onVirtualChangeHandler handler
+func (m *Manager) SetOnVirtualChange(onVirtualChangeHandler flowcontext.OnVirtualChangeHandler) {
+	m.context.SetOnVirtualChangeHandler(onVirtualChangeHandler)
+}
+
 // SetOnBlockAddedToDAGHandler sets the onBlockAddedToDAG handler
 func (m *Manager) SetOnBlockAddedToDAGHandler(onBlockAddedToDAGHandler flowcontext.OnBlockAddedToDAGHandler) {
 	m.context.SetOnBlockAddedToDAGHandler(onBlockAddedToDAGHandler)

app/protocol/peer/peer.go

@@ -13,10 +13,6 @@ import (
 	"github.com/kaspanet/kaspad/util/mstime"
 )
 
-// maxProtocolVersion version is the maximum supported protocol
-// version this kaspad node supports
-const maxProtocolVersion = 3
-
 // Peer holds data about a peer.
 type Peer struct {
 	connection *netadapter.NetConnection
@@ -35,6 +31,8 @@ type Peer struct {
 	lastPingNonce    uint64        // The nonce of the last ping we sent
 	lastPingTime     time.Time     // Time we sent last ping
 	lastPingDuration time.Duration // Time for last ping to return
+
+	ibdRequestChannel chan *externalapi.DomainBlock // A channel used to communicate IBD requests between flows
 }
 
 // New returns a new Peer
@@ -42,6 +40,7 @@ func New(connection *netadapter.NetConnection) *Peer {
 	return &Peer{
 		connection:        connection,
 		connectionStarted: time.Now(),
+		ibdRequestChannel: make(chan *externalapi.DomainBlock),
 	}
 }
 
@@ -76,6 +75,11 @@ func (p *Peer) AdvertisedProtocolVersion() uint32 {
 	return p.advertisedProtocolVerion
 }
 
+// ProtocolVersion returns the protocol version which is used when communicating with the peer.
+func (p *Peer) ProtocolVersion() uint32 {
+	return p.protocolVersion
+}
+
 // TimeConnected returns the time since the connection to this been has been started.
 func (p *Peer) TimeConnected() time.Duration {
 	return time.Since(p.connectionStarted)
@@ -87,7 +91,7 @@ func (p *Peer) IsOutbound() bool {
 }
 
 // UpdateFieldsFromMsgVersion updates the peer with the data from the version message.
-func (p *Peer) UpdateFieldsFromMsgVersion(msg *appmessage.MsgVersion) {
+func (p *Peer) UpdateFieldsFromMsgVersion(msg *appmessage.MsgVersion, maxProtocolVersion uint32) {
 	// Negotiate the protocol version.
 	p.advertisedProtocolVerion = msg.ProtocolVersion
 	p.protocolVersion = mathUtil.MinUint32(maxProtocolVersion, p.advertisedProtocolVerion)
@@ -142,3 +146,8 @@ func (p *Peer) LastPingDuration() time.Duration {
 
 	return p.lastPingDuration
 }
+
+// IBDRequestChannel returns the channel used in order to communicate an IBD request between peer flows
+func (p *Peer) IBDRequestChannel() chan *externalapi.DomainBlock {
+	return p.ibdRequestChannel
+}