xds: add xDS transport custom dial options support

internal/xds/bootstrap/bootstrap.go

@@ -179,9 +179,9 @@ type ServerConfig struct {
 	// As part of unmarshalling the JSON config into this struct, we ensure that
 	// the credentials config is valid by building an instance of the specified
 	// credentials and store it here for easy access.
-	selectedCreds   ChannelCreds
-	credsDialOption grpc.DialOption
-	dialerOption    grpc.DialOption
+	selectedCreds    ChannelCreds
+	credsDialOption  grpc.DialOption
+	extraDialOptions []grpc.DialOption
 
 	cleanups []func()
 }
@@ -224,8 +224,8 @@ func (sc *ServerConfig) ServerFeaturesIgnoreResourceDeletion() bool {
 // server.
 func (sc *ServerConfig) DialOptions() []grpc.DialOption {
 	dopts := []grpc.DialOption{sc.credsDialOption}
-	if sc.dialerOption != nil {
-		dopts = append(dopts, sc.dialerOption)
+	if sc.extraDialOptions != nil {
+		dopts = append(dopts, sc.extraDialOptions...)
 	}
 	return dopts
 }
@@ -283,11 +283,18 @@ func (sc *ServerConfig) MarshalJSON() ([]byte, error) {
 }
 
 // dialer captures the Dialer method specified via the credentials bundle.
+// Deprecated: use extradDialOptions. Will take precedence over this.
 type dialer interface {
 	// Dialer specifies how to dial the xDS server.
 	Dialer(context.Context, string) (net.Conn, error)
 }
 
+// extraDialOptions captures custom dial options specified via
+// credentials.Bundle.
+type extraDialOptions interface {
+	DialOptions() []grpc.DialOption
+}
+
 // UnmarshalJSON takes the json data (a server) and unmarshals it to the struct.
 func (sc *ServerConfig) UnmarshalJSON(data []byte) error {
 	server := serverConfigJSON{}
@@ -311,8 +318,10 @@ func (sc *ServerConfig) UnmarshalJSON(data []byte) error {
 		}
 		sc.selectedCreds = cc
 		sc.credsDialOption = grpc.WithCredentialsBundle(bundle)
-		if d, ok := bundle.(dialer); ok {
-			sc.dialerOption = grpc.WithContextDialer(d.Dialer)
+		if d, ok := bundle.(extraDialOptions); ok {
+			sc.extraDialOptions = d.DialOptions()
+		} else if d, ok := bundle.(dialer); ok {
+			sc.extraDialOptions = []grpc.DialOption{grpc.WithContextDialer(d.Dialer)}
 		}
 		sc.cleanups = append(sc.cleanups, cancel)
 		break

xds/internal/xdsclient/tests/client_custom_dialopts_test.go

@@ -0,0 +1,165 @@
+/*
+ *
+ * Copyright 2024 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 xdsclient_test
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/google/uuid"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/credentials/insecure"
+	"google.golang.org/grpc/internal"
+	"google.golang.org/grpc/internal/stubserver"
+	"google.golang.org/grpc/internal/testutils"
+	"google.golang.org/grpc/internal/testutils/xds/e2e"
+	internalbootstrap "google.golang.org/grpc/internal/xds/bootstrap"
+	testgrpc "google.golang.org/grpc/interop/grpc_testing"
+	testpb "google.golang.org/grpc/interop/grpc_testing"
+	"google.golang.org/grpc/resolver"
+	"google.golang.org/grpc/xds/bootstrap"
+	xci "google.golang.org/grpc/xds/internal/xdsclient/internal"
+)
+
+// nopDialOption is a no-op grpc.DialOption with a name.
+type nopDialOption struct {
+	grpc.EmptyDialOption
+	name string
+}
+
+// testCredsBundle implements `credentials.Bundle` and `extraDialOptions`.
+type testCredsBundle struct {
+	credentials.Bundle
+	testDialOptNames []string
+}
+
+func (t *testCredsBundle) DialOptions() []grpc.DialOption {
+	var opts []grpc.DialOption
+	for _, name := range t.testDialOptNames {
+		opts = append(opts, &nopDialOption{name: name})
+	}
+	return opts
+}
+
+type testCredsBuilder struct {
+	testDialOptNames []string
+}
+
+func (t *testCredsBuilder) Build(config json.RawMessage) (credentials.Bundle, func(), error) {
+	return &testCredsBundle{
+		Bundle:           insecure.NewBundle(),
+		testDialOptNames: t.testDialOptNames,
+	}, func() {}, nil
+}
+
+func (t *testCredsBuilder) Name() string {
+	return "test_dialer_creds"
+}
+
+func (s) TestClientCustomDialOptsFromCredentialsBundle(t *testing.T) {
+	// Create and register the credentials bundle builder.
+	credsBuilder := &testCredsBuilder{
+		testDialOptNames: []string{"opt1", "opt2", "opt3"},
+	}
+	bootstrap.RegisterCredentials(credsBuilder)
+
+	// Start an xDS management server.
+	mgmtServer := e2e.StartManagementServer(t, e2e.ManagementServerOptions{})
+
+	// Create bootstrap configuration pointing to the above management server.
+	nodeID := uuid.New().String()
+	bc, err := internalbootstrap.NewContentsForTesting(internalbootstrap.ConfigOptionsForTesting{
+		Servers: []byte(fmt.Sprintf(`[{
+			"server_uri": %q,
+			"channel_creds": [{
+				"type": %q,
+				"config": {"mgmt_server_address": %q}
+			}]
+		}]`, mgmtServer.Address, credsBuilder.Name(), mgmtServer.Address)),
+		Node: []byte(fmt.Sprintf(`{"id": "%s"}`, nodeID)),
+	})
+	if err != nil {
+		t.Fatalf("Failed to create bootstrap configuration: %v", err)
+	}
+
+	// Create an xDS resolver with the above bootstrap configuration.
+	var resolverBuilder resolver.Builder
+	if newResolver := internal.NewXDSResolverWithConfigForTesting; newResolver != nil {
+		resolverBuilder, err = newResolver.(func([]byte) (resolver.Builder, error))(bc)
+		if err != nil {
+			t.Fatalf("Failed to create xDS resolver for testing: %v", err)
+		}
+	}
+
+	// Spin up a test backend.
+	server := stubserver.StartTestService(t, nil)
+	defer server.Stop()
+
+	// Configure client side xDS resources on the management server.
+	const serviceName = "my-service-client-side-xds"
+	resources := e2e.DefaultClientResources(e2e.ResourceParams{
+		DialTarget: serviceName,
+		NodeID:     nodeID,
+		Host:       "localhost",
+		Port:       testutils.ParsePort(t, server.Address),
+		SecLevel:   e2e.SecurityLevelNone,
+	})
+	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
+	defer cancel()
+	if err := mgmtServer.Update(ctx, resources); err != nil {
+		t.Fatal(err)
+	}
+
+	// Intercept a grpc.NewClient call from the xds client to validate DialOptions.
+	xci.GRPCNewClient = func(target string, opts ...grpc.DialOption) (conn *grpc.ClientConn, err error) {
+		got := map[string]int{}
+		for _, opt := range opts {
+			if mo, ok := opt.(*nopDialOption); ok {
+				got[mo.name]++
+			}
+		}
+		want := map[string]int{}
+		for _, name := range credsBuilder.testDialOptNames {
+			want[name]++
+		}
+		if !cmp.Equal(got, want) {
+			t.Errorf("grpc.NewClient() was called with unexpected DialOptions: got %v, want %v", got, want)
+		}
+		return grpc.NewClient(target, opts...)
+	}
+	defer func() { xci.GRPCNewClient = grpc.NewClient }()
+
+	// Create a ClientConn and make a successful RPC. The insecure transport
+	// credentials passed into the gRPC.NewClient is the credentials for the
+	// data plane communication with the test backend.
+	cc, err := grpc.NewClient(fmt.Sprintf("xds:///%s", serviceName), grpc.WithTransportCredentials(insecure.NewCredentials()), grpc.WithResolvers(resolverBuilder))
+	if err != nil {
+		t.Fatalf("Failed to dial local test server: %v", err)
+	}
+
+	client := testgrpc.NewTestServiceClient(cc)
+	if _, err := client.EmptyCall(ctx, &testpb.Empty{}); err != nil {
+		t.Fatalf("EmptyCall() failed: %v", err)
+	}
+	cc.Close()
+}