[NOD-1550] Don't request blocks for invs that are known to be orphans (#1108)

* [NOD-1550] Implement IsOrphan().

* [NOD-1550] Don't request blocks for invs that are known to be orphans.

app/protocol/flowcontext/flow_context.go

@@ -53,7 +53,7 @@ type FlowContext struct {
 	peersMutex sync.RWMutex
 
 	orphans      map[externalapi.DomainHash]*externalapi.DomainBlock
-	orphansMutex sync.Mutex
+	orphansMutex sync.RWMutex
 }
 
 // New returns a new instance of FlowContext.

app/protocol/flowcontext/ibd.go

@@ -58,11 +58,15 @@ func (f *FlowContext) selectPeerForIBD(syncInfo *externalapi.SyncInfo) (*peerpkg
 
 	for _, peer := range f.peers {
 		peerSelectedTipHash := peer.SelectedTipHash()
+
+		if f.IsOrphan(peerSelectedTipHash) {
+			continue
+		}
+
 		blockInfo, err := f.domain.Consensus().GetBlockInfo(peerSelectedTipHash)
 		if err != nil {
 			return nil, err
 		}
-
 		if syncInfo.State == externalapi.SyncStateHeadersFirst {
 			if !blockInfo.Exists {
 				return peer, nil

app/protocol/flowcontext/orphans.go

@@ -18,6 +18,15 @@ func (f *FlowContext) AddOrphan(orphanBlock *externalapi.DomainBlock) {
 	log.Infof("Received a block with missing parents, adding to orphan pool: %s", orphanHash)
 }
 
+// IsOrphan returns whether the given blockHash belongs to an orphan block
+func (f *FlowContext) IsOrphan(blockHash *externalapi.DomainHash) bool {
+	f.orphansMutex.RLock()
+	defer f.orphansMutex.RUnlock()
+
+	_, ok := f.orphans[*blockHash]
+	return ok
+}
+
 // UnorphanBlocks removes the block from the orphan set, and remove all of the blocks that are not orphans anymore.
 func (f *FlowContext) UnorphanBlocks(rootBlock *externalapi.DomainBlock) ([]*externalapi.DomainBlock, error) {
 	f.orphansMutex.Lock()

app/protocol/flows/blockrelay/handle_relay_invs.go

@@ -26,6 +26,7 @@ type RelayInvsContext interface {
 	IsInIBD() bool
 	Broadcast(message appmessage.Message) error
 	AddOrphan(orphanBlock *externalapi.DomainBlock)
+	IsOrphan(blockHash *externalapi.DomainHash) bool
 }
 
 type handleRelayInvsFlow struct {
@@ -71,6 +72,10 @@ func (flow *handleRelayInvsFlow) start() error {
 			continue
 		}
 
+		if flow.IsOrphan(inv.Hash) {
+			continue
+		}
+
 		err = flow.StartIBDIfRequired()
 		if err != nil {
 			return err