vendor: add losing grpc files (#11557)

vendor/google.golang.org/grpc/attributes/attributes.go

@@ -0,0 +1,70 @@
+/*
+ *
+ * Copyright 2019 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package attributes defines a generic key/value store used in various gRPC
+// components.
+//
+// All APIs in this package are EXPERIMENTAL.
+package attributes
+
+import "fmt"
+
+// Attributes is an immutable struct for storing and retrieving generic
+// key/value pairs.  Keys must be hashable, and users should define their own
+// types for keys.
+type Attributes struct {
+	m map[interface{}]interface{}
+}
+
+// New returns a new Attributes containing all key/value pairs in kvs.  If the
+// same key appears multiple times, the last value overwrites all previous
+// values for that key.  Panics if len(kvs) is not even.
+func New(kvs ...interface{}) *Attributes {
+	if len(kvs)%2 != 0 {
+		panic(fmt.Sprintf("attributes.New called with unexpected input: len(kvs) = %v", len(kvs)))
+	}
+	a := &Attributes{m: make(map[interface{}]interface{}, len(kvs)/2)}
+	for i := 0; i < len(kvs)/2; i++ {
+		a.m[kvs[i*2]] = kvs[i*2+1]
+	}
+	return a
+}
+
+// WithValues returns a new Attributes containing all key/value pairs in a and
+// kvs.  Panics if len(kvs) is not even.  If the same key appears multiple
+// times, the last value overwrites all previous values for that key.  To
+// remove an existing key, use a nil value.
+func (a *Attributes) WithValues(kvs ...interface{}) *Attributes {
+	if len(kvs)%2 != 0 {
+		panic(fmt.Sprintf("attributes.New called with unexpected input: len(kvs) = %v", len(kvs)))
+	}
+	n := &Attributes{m: make(map[interface{}]interface{}, len(a.m)+len(kvs)/2)}
+	for k, v := range a.m {
+		n.m[k] = v
+	}
+	for i := 0; i < len(kvs)/2; i++ {
+		n.m[kvs[i*2]] = kvs[i*2+1]
+	}
+	return n
+}
+
+// Value returns the value associated with these attributes for key, or nil if
+// no value is associated with key.
+func (a *Attributes) Value(key interface{}) interface{} {
+	return a.m[key]
+}

vendor/google.golang.org/grpc/backoff/backoff.go

@@ -0,0 +1,52 @@
+/*
+ *
+ * Copyright 2019 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package backoff provides configuration options for backoff.
+//
+// More details can be found at:
+// https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md.
+//
+// All APIs in this package are experimental.
+package backoff
+
+import "time"
+
+// Config defines the configuration options for backoff.
+type Config struct {
+	// BaseDelay is the amount of time to backoff after the first failure.
+	BaseDelay time.Duration
+	// Multiplier is the factor with which to multiply backoffs after a
+	// failed retry. Should ideally be greater than 1.
+	Multiplier float64
+	// Jitter is the factor with which backoffs are randomized.
+	Jitter float64
+	// MaxDelay is the upper bound of backoff delay.
+	MaxDelay time.Duration
+}
+
+// DefaultConfig is a backoff configuration with the default values specfied
+// at https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md.
+//
+// This should be useful for callers who want to configure backoff with
+// non-default values only for a subset of the options.
+var DefaultConfig = Config{
+	BaseDelay:  1.0 * time.Second,
+	Multiplier: 1.6,
+	Jitter:     0.2,
+	MaxDelay:   120 * time.Second,
+}

vendor/google.golang.org/grpc/credentials/go12.go

@@ -0,0 +1,30 @@
+// +build go1.12
+
+/*
+ *
+ * Copyright 2019 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package credentials
+
+import "crypto/tls"
+
+// This init function adds cipher suite constants only defined in Go 1.12.
+func init() {
+	cipherSuiteLookup[tls.TLS_AES_128_GCM_SHA256] = "TLS_AES_128_GCM_SHA256"
+	cipherSuiteLookup[tls.TLS_AES_256_GCM_SHA384] = "TLS_AES_256_GCM_SHA384"
+	cipherSuiteLookup[tls.TLS_CHACHA20_POLY1305_SHA256] = "TLS_CHACHA20_POLY1305_SHA256"
+}

vendor/google.golang.org/grpc/credentials/tls.go

@@ -0,0 +1,220 @@
+/*
+ *
+ * Copyright 2014 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package credentials
+
+import (
+	"context"
+	"crypto/tls"
+	"crypto/x509"
+	"fmt"
+	"io/ioutil"
+	"net"
+
+	"google.golang.org/grpc/credentials/internal"
+)
+
+// TLSInfo contains the auth information for a TLS authenticated connection.
+// It implements the AuthInfo interface.
+type TLSInfo struct {
+	State tls.ConnectionState
+}
+
+// AuthType returns the type of TLSInfo as a string.
+func (t TLSInfo) AuthType() string {
+	return "tls"
+}
+
+// GetSecurityValue returns security info requested by channelz.
+func (t TLSInfo) GetSecurityValue() ChannelzSecurityValue {
+	v := &TLSChannelzSecurityValue{
+		StandardName: cipherSuiteLookup[t.State.CipherSuite],
+	}
+	// Currently there's no way to get LocalCertificate info from tls package.
+	if len(t.State.PeerCertificates) > 0 {
+		v.RemoteCertificate = t.State.PeerCertificates[0].Raw
+	}
+	return v
+}
+
+// tlsCreds is the credentials required for authenticating a connection using TLS.
+type tlsCreds struct {
+	// TLS configuration
+	config *tls.Config
+}
+
+func (c tlsCreds) Info() ProtocolInfo {
+	return ProtocolInfo{
+		SecurityProtocol: "tls",
+		SecurityVersion:  "1.2",
+		ServerName:       c.config.ServerName,
+	}
+}
+
+func (c *tlsCreds) ClientHandshake(ctx context.Context, authority string, rawConn net.Conn) (_ net.Conn, _ AuthInfo, err error) {
+	// use local cfg to avoid clobbering ServerName if using multiple endpoints
+	cfg := cloneTLSConfig(c.config)
+	if cfg.ServerName == "" {
+		serverName, _, err := net.SplitHostPort(authority)
+		if err != nil {
+			// If the authority had no host port or if the authority cannot be parsed, use it as-is.
+			serverName = authority
+		}
+		cfg.ServerName = serverName
+	}
+	conn := tls.Client(rawConn, cfg)
+	errChannel := make(chan error, 1)
+	go func() {
+		errChannel <- conn.Handshake()
+	}()
+	select {
+	case err := <-errChannel:
+		if err != nil {
+			return nil, nil, err
+		}
+	case <-ctx.Done():
+		return nil, nil, ctx.Err()
+	}
+	return internal.WrapSyscallConn(rawConn, conn), TLSInfo{conn.ConnectionState()}, nil
+}
+
+func (c *tlsCreds) ServerHandshake(rawConn net.Conn) (net.Conn, AuthInfo, error) {
+	conn := tls.Server(rawConn, c.config)
+	if err := conn.Handshake(); err != nil {
+		return nil, nil, err
+	}
+	return internal.WrapSyscallConn(rawConn, conn), TLSInfo{conn.ConnectionState()}, nil
+}
+
+func (c *tlsCreds) Clone() TransportCredentials {
+	return NewTLS(c.config)
+}
+
+func (c *tlsCreds) OverrideServerName(serverNameOverride string) error {
+	c.config.ServerName = serverNameOverride
+	return nil
+}
+
+const alpnProtoStrH2 = "h2"
+
+func appendH2ToNextProtos(ps []string) []string {
+	for _, p := range ps {
+		if p == alpnProtoStrH2 {
+			return ps
+		}
+	}
+	ret := make([]string, 0, len(ps)+1)
+	ret = append(ret, ps...)
+	return append(ret, alpnProtoStrH2)
+}
+
+// NewTLS uses c to construct a TransportCredentials based on TLS.
+func NewTLS(c *tls.Config) TransportCredentials {
+	tc := &tlsCreds{cloneTLSConfig(c)}
+	tc.config.NextProtos = appendH2ToNextProtos(tc.config.NextProtos)
+	return tc
+}
+
+// NewClientTLSFromCert constructs TLS credentials from the input certificate for client.
+// serverNameOverride is for testing only. If set to a non empty string,
+// it will override the virtual host name of authority (e.g. :authority header field) in requests.
+func NewClientTLSFromCert(cp *x509.CertPool, serverNameOverride string) TransportCredentials {
+	return NewTLS(&tls.Config{ServerName: serverNameOverride, RootCAs: cp})
+}
+
+// NewClientTLSFromFile constructs TLS credentials from the input certificate file for client.
+// serverNameOverride is for testing only. If set to a non empty string,
+// it will override the virtual host name of authority (e.g. :authority header field) in requests.
+func NewClientTLSFromFile(certFile, serverNameOverride string) (TransportCredentials, error) {
+	b, err := ioutil.ReadFile(certFile)
+	if err != nil {
+		return nil, err
+	}
+	cp := x509.NewCertPool()
+	if !cp.AppendCertsFromPEM(b) {
+		return nil, fmt.Errorf("credentials: failed to append certificates")
+	}
+	return NewTLS(&tls.Config{ServerName: serverNameOverride, RootCAs: cp}), nil
+}
+
+// NewServerTLSFromCert constructs TLS credentials from the input certificate for server.
+func NewServerTLSFromCert(cert *tls.Certificate) TransportCredentials {
+	return NewTLS(&tls.Config{Certificates: []tls.Certificate{*cert}})
+}
+
+// NewServerTLSFromFile constructs TLS credentials from the input certificate file and key
+// file for server.
+func NewServerTLSFromFile(certFile, keyFile string) (TransportCredentials, error) {
+	cert, err := tls.LoadX509KeyPair(certFile, keyFile)
+	if err != nil {
+		return nil, err
+	}
+	return NewTLS(&tls.Config{Certificates: []tls.Certificate{cert}}), nil
+}
+
+// TLSChannelzSecurityValue defines the struct that TLS protocol should return
+// from GetSecurityValue(), containing security info like cipher and certificate used.
+//
+// This API is EXPERIMENTAL.
+type TLSChannelzSecurityValue struct {
+	ChannelzSecurityValue
+	StandardName      string
+	LocalCertificate  []byte
+	RemoteCertificate []byte
+}
+
+var cipherSuiteLookup = map[uint16]string{
+	tls.TLS_RSA_WITH_RC4_128_SHA:                "TLS_RSA_WITH_RC4_128_SHA",
+	tls.TLS_RSA_WITH_3DES_EDE_CBC_SHA:           "TLS_RSA_WITH_3DES_EDE_CBC_SHA",
+	tls.TLS_RSA_WITH_AES_128_CBC_SHA:            "TLS_RSA_WITH_AES_128_CBC_SHA",
+	tls.TLS_RSA_WITH_AES_256_CBC_SHA:            "TLS_RSA_WITH_AES_256_CBC_SHA",
+	tls.TLS_RSA_WITH_AES_128_GCM_SHA256:         "TLS_RSA_WITH_AES_128_GCM_SHA256",
+	tls.TLS_RSA_WITH_AES_256_GCM_SHA384:         "TLS_RSA_WITH_AES_256_GCM_SHA384",
+	tls.TLS_ECDHE_ECDSA_WITH_RC4_128_SHA:        "TLS_ECDHE_ECDSA_WITH_RC4_128_SHA",
+	tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA:    "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA",
+	tls.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA:    "TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA",
+	tls.TLS_ECDHE_RSA_WITH_RC4_128_SHA:          "TLS_ECDHE_RSA_WITH_RC4_128_SHA",
+	tls.TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA:     "TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA",
+	tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA:      "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA",
+	tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA:      "TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA",
+	tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256:   "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256",
+	tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256: "TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256",
+	tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384:   "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384",
+	tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384: "TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384",
+	tls.TLS_FALLBACK_SCSV:                       "TLS_FALLBACK_SCSV",
+	tls.TLS_RSA_WITH_AES_128_CBC_SHA256:         "TLS_RSA_WITH_AES_128_CBC_SHA256",
+	tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256: "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256",
+	tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256:   "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256",
+	tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305:    "TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305",
+	tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305:  "TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305",
+}
+
+// cloneTLSConfig returns a shallow clone of the exported
+// fields of cfg, ignoring the unexported sync.Once, which
+// contains a mutex and must not be copied.
+//
+// If cfg is nil, a new zero tls.Config is returned.
+//
+// TODO: inline this function if possible.
+func cloneTLSConfig(cfg *tls.Config) *tls.Config {
+	if cfg == nil {
+		return &tls.Config{}
+	}
+
+	return cfg.Clone()
+}

vendor/google.golang.org/grpc/internal/buffer/unbounded.go

@@ -0,0 +1,85 @@
+/*
+ * Copyright 2019 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package buffer provides an implementation of an unbounded buffer.
+package buffer
+
+import "sync"
+
+// Unbounded is an implementation of an unbounded buffer which does not use
+// extra goroutines. This is typically used for passing updates from one entity
+// to another within gRPC.
+//
+// All methods on this type are thread-safe and don't block on anything except
+// the underlying mutex used for synchronization.
+//
+// Unbounded supports values of any type to be stored in it by using a channel
+// of `interface{}`. This means that a call to Put() incurs an extra memory
+// allocation, and also that users need a type assertion while reading. For
+// performance critical code paths, using Unbounded is strongly discouraged and
+// defining a new type specific implementation of this buffer is preferred. See
+// internal/transport/transport.go for an example of this.
+type Unbounded struct {
+	c       chan interface{}
+	mu      sync.Mutex
+	backlog []interface{}
+}
+
+// NewUnbounded returns a new instance of Unbounded.
+func NewUnbounded() *Unbounded {
+	return &Unbounded{c: make(chan interface{}, 1)}
+}
+
+// Put adds t to the unbounded buffer.
+func (b *Unbounded) Put(t interface{}) {
+	b.mu.Lock()
+	if len(b.backlog) == 0 {
+		select {
+		case b.c <- t:
+			b.mu.Unlock()
+			return
+		default:
+		}
+	}
+	b.backlog = append(b.backlog, t)
+	b.mu.Unlock()
+}
+
+// Load sends the earliest buffered data, if any, onto the read channel
+// returned by Get(). Users are expected to call this every time they read a
+// value from the read channel.
+func (b *Unbounded) Load() {
+	b.mu.Lock()
+	if len(b.backlog) > 0 {
+		select {
+		case b.c <- b.backlog[0]:
+			b.backlog[0] = nil
+			b.backlog = b.backlog[1:]
+		default:
+		}
+	}
+	b.mu.Unlock()
+}
+
+// Get returns a read channel on which values added to the buffer, via Put(),
+// are sent on.
+//
+// Upon reading a value from this channel, users are expected to call Load() to
+// send the next buffered value onto the channel if there is any.
+func (b *Unbounded) Get() <-chan interface{} {
+	return b.c
+}

vendor/google.golang.org/grpc/internal/resolver/dns/dns_resolver.go

@@ -0,0 +1,420 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package dns implements a dns resolver to be installed as the default resolver
+// in grpc.
+package dns
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net"
+	"os"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/internal/grpcrand"
+	"google.golang.org/grpc/resolver"
+	"google.golang.org/grpc/serviceconfig"
+)
+
+// EnableSRVLookups controls whether the DNS resolver attempts to fetch gRPCLB
+// addresses from SRV records.  Must not be changed after init time.
+var EnableSRVLookups = false
+
+func init() {
+	resolver.Register(NewBuilder())
+}
+
+const (
+	defaultPort       = "443"
+	defaultDNSSvrPort = "53"
+	golang            = "GO"
+	// txtPrefix is the prefix string to be prepended to the host name for txt record lookup.
+	txtPrefix = "_grpc_config."
+	// In DNS, service config is encoded in a TXT record via the mechanism
+	// described in RFC-1464 using the attribute name grpc_config.
+	txtAttribute = "grpc_config="
+)
+
+var (
+	errMissingAddr = errors.New("dns resolver: missing address")
+
+	// Addresses ending with a colon that is supposed to be the separator
+	// between host and port is not allowed.  E.g. "::" is a valid address as
+	// it is an IPv6 address (host only) and "[::]:" is invalid as it ends with
+	// a colon as the host and port separator
+	errEndsWithColon = errors.New("dns resolver: missing port after port-separator colon")
+)
+
+var (
+	defaultResolver netResolver = net.DefaultResolver
+	// To prevent excessive re-resolution, we enforce a rate limit on DNS
+	// resolution requests.
+	minDNSResRate = 30 * time.Second
+)
+
+var customAuthorityDialler = func(authority string) func(ctx context.Context, network, address string) (net.Conn, error) {
+	return func(ctx context.Context, network, address string) (net.Conn, error) {
+		var dialer net.Dialer
+		return dialer.DialContext(ctx, network, authority)
+	}
+}
+
+var customAuthorityResolver = func(authority string) (netResolver, error) {
+	host, port, err := parseTarget(authority, defaultDNSSvrPort)
+	if err != nil {
+		return nil, err
+	}
+
+	authorityWithPort := net.JoinHostPort(host, port)
+
+	return &net.Resolver{
+		PreferGo: true,
+		Dial:     customAuthorityDialler(authorityWithPort),
+	}, nil
+}
+
+// NewBuilder creates a dnsBuilder which is used to factory DNS resolvers.
+func NewBuilder() resolver.Builder {
+	return &dnsBuilder{}
+}
+
+type dnsBuilder struct{}
+
+// Build creates and starts a DNS resolver that watches the name resolution of the target.
+func (b *dnsBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) {
+	host, port, err := parseTarget(target.Endpoint, defaultPort)
+	if err != nil {
+		return nil, err
+	}
+
+	// IP address.
+	if ipAddr, ok := formatIP(host); ok {
+		addr := []resolver.Address{{Addr: ipAddr + ":" + port}}
+		cc.UpdateState(resolver.State{Addresses: addr})
+		return deadResolver{}, nil
+	}
+
+	// DNS address (non-IP).
+	ctx, cancel := context.WithCancel(context.Background())
+	d := &dnsResolver{
+		host:                 host,
+		port:                 port,
+		ctx:                  ctx,
+		cancel:               cancel,
+		cc:                   cc,
+		rn:                   make(chan struct{}, 1),
+		disableServiceConfig: opts.DisableServiceConfig,
+	}
+
+	if target.Authority == "" {
+		d.resolver = defaultResolver
+	} else {
+		d.resolver, err = customAuthorityResolver(target.Authority)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	d.wg.Add(1)
+	go d.watcher()
+	d.ResolveNow(resolver.ResolveNowOptions{})
+	return d, nil
+}
+
+// Scheme returns the naming scheme of this resolver builder, which is "dns".
+func (b *dnsBuilder) Scheme() string {
+	return "dns"
+}
+
+type netResolver interface {
+	LookupHost(ctx context.Context, host string) (addrs []string, err error)
+	LookupSRV(ctx context.Context, service, proto, name string) (cname string, addrs []*net.SRV, err error)
+	LookupTXT(ctx context.Context, name string) (txts []string, err error)
+}
+
+// deadResolver is a resolver that does nothing.
+type deadResolver struct{}
+
+func (deadResolver) ResolveNow(resolver.ResolveNowOptions) {}
+
+func (deadResolver) Close() {}
+
+// dnsResolver watches for the name resolution update for a non-IP target.
+type dnsResolver struct {
+	host     string
+	port     string
+	resolver netResolver
+	ctx      context.Context
+	cancel   context.CancelFunc
+	cc       resolver.ClientConn
+	// rn channel is used by ResolveNow() to force an immediate resolution of the target.
+	rn chan struct{}
+	// wg is used to enforce Close() to return after the watcher() goroutine has finished.
+	// Otherwise, data race will be possible. [Race Example] in dns_resolver_test we
+	// replace the real lookup functions with mocked ones to facilitate testing.
+	// If Close() doesn't wait for watcher() goroutine finishes, race detector sometimes
+	// will warns lookup (READ the lookup function pointers) inside watcher() goroutine
+	// has data race with replaceNetFunc (WRITE the lookup function pointers).
+	wg                   sync.WaitGroup
+	disableServiceConfig bool
+}
+
+// ResolveNow invoke an immediate resolution of the target that this dnsResolver watches.
+func (d *dnsResolver) ResolveNow(resolver.ResolveNowOptions) {
+	select {
+	case d.rn <- struct{}{}:
+	default:
+	}
+}
+
+// Close closes the dnsResolver.
+func (d *dnsResolver) Close() {
+	d.cancel()
+	d.wg.Wait()
+}
+
+func (d *dnsResolver) watcher() {
+	defer d.wg.Done()
+	for {
+		select {
+		case <-d.ctx.Done():
+			return
+		case <-d.rn:
+		}
+
+		state := d.lookup()
+		d.cc.UpdateState(*state)
+
+		// Sleep to prevent excessive re-resolutions. Incoming resolution requests
+		// will be queued in d.rn.
+		t := time.NewTimer(minDNSResRate)
+		select {
+		case <-t.C:
+		case <-d.ctx.Done():
+			t.Stop()
+			return
+		}
+	}
+}
+
+func (d *dnsResolver) lookupSRV() []resolver.Address {
+	if !EnableSRVLookups {
+		return nil
+	}
+	var newAddrs []resolver.Address
+	_, srvs, err := d.resolver.LookupSRV(d.ctx, "grpclb", "tcp", d.host)
+	if err != nil {
+		grpclog.Infof("grpc: failed dns SRV record lookup due to %v.\n", err)
+		return nil
+	}
+	for _, s := range srvs {
+		lbAddrs, err := d.resolver.LookupHost(d.ctx, s.Target)
+		if err != nil {
+			grpclog.Infof("grpc: failed load balancer address dns lookup due to %v.\n", err)
+			continue
+		}
+		for _, a := range lbAddrs {
+			a, ok := formatIP(a)
+			if !ok {
+				grpclog.Errorf("grpc: failed IP parsing due to %v.\n", err)
+				continue
+			}
+			addr := a + ":" + strconv.Itoa(int(s.Port))
+			newAddrs = append(newAddrs, resolver.Address{Addr: addr, Type: resolver.GRPCLB, ServerName: s.Target})
+		}
+	}
+	return newAddrs
+}
+
+var filterError = func(err error) error {
+	if dnsErr, ok := err.(*net.DNSError); ok && !dnsErr.IsTimeout && !dnsErr.IsTemporary {
+		// Timeouts and temporary errors should be communicated to gRPC to
+		// attempt another DNS query (with backoff).  Other errors should be
+		// suppressed (they may represent the absence of a TXT record).
+		return nil
+	}
+	return err
+}
+
+func (d *dnsResolver) lookupTXT() *serviceconfig.ParseResult {
+	ss, err := d.resolver.LookupTXT(d.ctx, txtPrefix+d.host)
+	if err != nil {
+		err = filterError(err)
+		if err != nil {
+			err = fmt.Errorf("error from DNS TXT record lookup: %v", err)
+			grpclog.Infoln("grpc:", err)
+			return &serviceconfig.ParseResult{Err: err}
+		}
+		return nil
+	}
+	var res string
+	for _, s := range ss {
+		res += s
+	}
+
+	// TXT record must have "grpc_config=" attribute in order to be used as service config.
+	if !strings.HasPrefix(res, txtAttribute) {
+		grpclog.Warningf("grpc: DNS TXT record %v missing %v attribute", res, txtAttribute)
+		// This is not an error; it is the equivalent of not having a service config.
+		return nil
+	}
+	sc := canaryingSC(strings.TrimPrefix(res, txtAttribute))
+	return d.cc.ParseServiceConfig(sc)
+}
+
+func (d *dnsResolver) lookupHost() []resolver.Address {
+	var newAddrs []resolver.Address
+	addrs, err := d.resolver.LookupHost(d.ctx, d.host)
+	if err != nil {
+		grpclog.Warningf("grpc: failed dns A record lookup due to %v.\n", err)
+		return nil
+	}
+	for _, a := range addrs {
+		a, ok := formatIP(a)
+		if !ok {
+			grpclog.Errorf("grpc: failed IP parsing due to %v.\n", err)
+			continue
+		}
+		addr := a + ":" + d.port
+		newAddrs = append(newAddrs, resolver.Address{Addr: addr})
+	}
+	return newAddrs
+}
+
+func (d *dnsResolver) lookup() *resolver.State {
+	srv := d.lookupSRV()
+	state := &resolver.State{
+		Addresses: append(d.lookupHost(), srv...),
+	}
+	if !d.disableServiceConfig {
+		state.ServiceConfig = d.lookupTXT()
+	}
+	return state
+}
+
+// formatIP returns ok = false if addr is not a valid textual representation of an IP address.
+// If addr is an IPv4 address, return the addr and ok = true.
+// If addr is an IPv6 address, return the addr enclosed in square brackets and ok = true.
+func formatIP(addr string) (addrIP string, ok bool) {
+	ip := net.ParseIP(addr)
+	if ip == nil {
+		return "", false
+	}
+	if ip.To4() != nil {
+		return addr, true
+	}
+	return "[" + addr + "]", true
+}
+
+// parseTarget takes the user input target string and default port, returns formatted host and port info.
+// If target doesn't specify a port, set the port to be the defaultPort.
+// If target is in IPv6 format and host-name is enclosed in square brackets, brackets
+// are stripped when setting the host.
+// examples:
+// target: "www.google.com" defaultPort: "443" returns host: "www.google.com", port: "443"
+// target: "ipv4-host:80" defaultPort: "443" returns host: "ipv4-host", port: "80"
+// target: "[ipv6-host]" defaultPort: "443" returns host: "ipv6-host", port: "443"
+// target: ":80" defaultPort: "443" returns host: "localhost", port: "80"
+func parseTarget(target, defaultPort string) (host, port string, err error) {
+	if target == "" {
+		return "", "", errMissingAddr
+	}
+	if ip := net.ParseIP(target); ip != nil {
+		// target is an IPv4 or IPv6(without brackets) address
+		return target, defaultPort, nil
+	}
+	if host, port, err = net.SplitHostPort(target); err == nil {
+		if port == "" {
+			// If the port field is empty (target ends with colon), e.g. "[::1]:", this is an error.
+			return "", "", errEndsWithColon
+		}
+		// target has port, i.e ipv4-host:port, [ipv6-host]:port, host-name:port
+		if host == "" {
+			// Keep consistent with net.Dial(): If the host is empty, as in ":80", the local system is assumed.
+			host = "localhost"
+		}
+		return host, port, nil
+	}
+	if host, port, err = net.SplitHostPort(target + ":" + defaultPort); err == nil {
+		// target doesn't have port
+		return host, port, nil
+	}
+	return "", "", fmt.Errorf("invalid target address %v, error info: %v", target, err)
+}
+
+type rawChoice struct {
+	ClientLanguage *[]string        `json:"clientLanguage,omitempty"`
+	Percentage     *int             `json:"percentage,omitempty"`
+	ClientHostName *[]string        `json:"clientHostName,omitempty"`
+	ServiceConfig  *json.RawMessage `json:"serviceConfig,omitempty"`
+}
+
+func containsString(a *[]string, b string) bool {
+	if a == nil {
+		return true
+	}
+	for _, c := range *a {
+		if c == b {
+			return true
+		}
+	}
+	return false
+}
+
+func chosenByPercentage(a *int) bool {
+	if a == nil {
+		return true
+	}
+	return grpcrand.Intn(100)+1 <= *a
+}
+
+func canaryingSC(js string) string {
+	if js == "" {
+		return ""
+	}
+	var rcs []rawChoice
+	err := json.Unmarshal([]byte(js), &rcs)
+	if err != nil {
+		grpclog.Warningf("grpc: failed to parse service config json string due to %v.\n", err)
+		return ""
+	}
+	cliHostname, err := os.Hostname()
+	if err != nil {
+		grpclog.Warningf("grpc: failed to get client hostname due to %v.\n", err)
+		return ""
+	}
+	var sc string
+	for _, c := range rcs {
+		if !containsString(c.ClientLanguage, golang) ||
+			!chosenByPercentage(c.Percentage) ||
+			!containsString(c.ClientHostName, cliHostname) ||
+			c.ServiceConfig == nil {
+			continue
+		}
+		sc = string(*c.ServiceConfig)
+		break
+	}
+	return sc
+}

vendor/google.golang.org/grpc/internal/resolver/dns/go113.go

@@ -0,0 +1,33 @@
+// +build go1.13
+
+/*
+ *
+ * Copyright 2019 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package dns
+
+import "net"
+
+func init() {
+	filterError = func(err error) error {
+		if dnsErr, ok := err.(*net.DNSError); ok && dnsErr.IsNotFound {
+			// The name does not exist; not an error.
+			return nil
+		}
+		return err
+	}
+}

vendor/google.golang.org/grpc/internal/resolver/passthrough/passthrough.go

@@ -0,0 +1,57 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package passthrough implements a pass-through resolver. It sends the target
+// name without scheme back to gRPC as resolved address.
+package passthrough
+
+import "google.golang.org/grpc/resolver"
+
+const scheme = "passthrough"
+
+type passthroughBuilder struct{}
+
+func (*passthroughBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) {
+	r := &passthroughResolver{
+		target: target,
+		cc:     cc,
+	}
+	r.start()
+	return r, nil
+}
+
+func (*passthroughBuilder) Scheme() string {
+	return scheme
+}
+
+type passthroughResolver struct {
+	target resolver.Target
+	cc     resolver.ClientConn
+}
+
+func (r *passthroughResolver) start() {
+	r.cc.UpdateState(resolver.State{Addresses: []resolver.Address{{Addr: r.target.Endpoint}}})
+}
+
+func (*passthroughResolver) ResolveNow(o resolver.ResolveNowOptions) {}
+
+func (*passthroughResolver) Close() {}
+
+func init() {
+	resolver.Register(&passthroughBuilder{})
+}