client: implement support for "unix" resolver scheme

balancer/rls/internal/config.go

@@ -201,7 +201,7 @@ func (*rlsBB) ParseConfig(c json.RawMessage) (serviceconfig.LoadBalancingConfig,
 	if lookupService == "" {
 		return nil, fmt.Errorf("rls: empty lookup_service in service config {%+v}", string(c))
 	}
-	parsedTarget := grpcutil.ParseTarget(lookupService)
+	parsedTarget := grpcutil.ParseTarget(lookupService, false)
 	if parsedTarget.Scheme == "" {
 		parsedTarget.Scheme = resolver.GetDefaultScheme()
 	}

clientconn.go

@@ -23,7 +23,6 @@ import (
 	"errors"
 	"fmt"
 	"math"
-	"net"
 	"reflect"
 	"strings"
 	"sync"
@@ -48,6 +47,7 @@ import (
 	_ "google.golang.org/grpc/balancer/roundrobin"           // To register roundrobin.
 	_ "google.golang.org/grpc/internal/resolver/dns"         // To register dns resolver.
 	_ "google.golang.org/grpc/internal/resolver/passthrough" // To register passthrough resolver.
+	_ "google.golang.org/grpc/internal/resolver/unix"        // To register unix resolver.
 )
 
 const (
@@ -191,16 +191,6 @@ func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *
 	}
 	cc.mkp = cc.dopts.copts.KeepaliveParams
 
-	if cc.dopts.copts.Dialer == nil {
-		cc.dopts.copts.Dialer = func(ctx context.Context, addr string) (net.Conn, error) {
-			network, addr := parseDialTarget(addr)
-			return (&net.Dialer{}).DialContext(ctx, network, addr)
-		}
-		if cc.dopts.withProxy {
-			cc.dopts.copts.Dialer = newProxyDialer(cc.dopts.copts.Dialer)
-		}
-	}
-
 	if cc.dopts.copts.UserAgent != "" {
 		cc.dopts.copts.UserAgent += " " + grpcUA
 	} else {
@@ -244,8 +234,7 @@ func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *
 	}
 
 	// Determine the resolver to use.
-	cc.parsedTarget = grpcutil.ParseTarget(cc.target)
-	unixScheme := strings.HasPrefix(cc.target, "unix:")
+	cc.parsedTarget = grpcutil.ParseTarget(cc.target, cc.dopts.copts.Dialer != nil)
 	channelz.Infof(logger, cc.channelzID, "parsed scheme: %q", cc.parsedTarget.Scheme)
 	resolverBuilder := cc.getResolver(cc.parsedTarget.Scheme)
 	if resolverBuilder == nil {
@@ -268,7 +257,7 @@ func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *
 		cc.authority = creds.Info().ServerName
 	} else if cc.dopts.insecure && cc.dopts.authority != "" {
 		cc.authority = cc.dopts.authority
-	} else if unixScheme {
+	} else if strings.HasPrefix(cc.target, "unix:") {
 		cc.authority = "localhost"
 	} else {
 		// Use endpoint from "scheme://authority/endpoint" as the default

dialoptions.go

@@ -71,7 +71,6 @@ type dialOptions struct {
 	// we need to be able to configure this in tests.
 	resolveNowBackoff func(int) time.Duration
 	resolvers         []resolver.Builder
-	withProxy         bool
 }
 
 // DialOption configures how we set up the connection.
@@ -325,7 +324,7 @@ func WithInsecure() DialOption {
 // later release.
 func WithNoProxy() DialOption {
 	return newFuncDialOption(func(o *dialOptions) {
-		o.withProxy = false
+		o.copts.UseProxy = false
 	})
 }
 
@@ -595,9 +594,9 @@ func defaultDialOptions() dialOptions {
 		copts: transport.ConnectOptions{
 			WriteBufferSize: defaultWriteBufSize,
 			ReadBufferSize:  defaultReadBufSize,
+			UseProxy:        true,
 		},
 		resolveNowBackoff: internalbackoff.DefaultExponential.Backoff,
-		withProxy:         true,
 	}
 }
 

internal/grpcutil/target.go

@@ -41,15 +41,26 @@ func split2(s, sep string) (string, string, bool) {
 //
 // If target is not a valid scheme://authority/endpoint, it returns {Endpoint:
 // target}.
-func ParseTarget(target string) (ret resolver.Target) {
+func ParseTarget(target string, hasDialer bool) (ret resolver.Target) {
 	var ok bool
 	ret.Scheme, ret.Endpoint, ok = split2(target, "://")
 	if !ok {
+		if strings.HasPrefix(target, "unix:") && !hasDialer {
+			// Handle the "unix:[path]" case, because splitting on :// only
+			// handles the "unix://[/absolute/path]" case. Only handle if the
+			// dialer is nil, to avoid a behavior change with custom dialers.
+			return resolver.Target{Scheme: "unix", Endpoint: target[len("unix:"):]}
+		}
 		return resolver.Target{Endpoint: target}
 	}
 	ret.Authority, ret.Endpoint, ok = split2(ret.Endpoint, "/")
 	if !ok {
 		return resolver.Target{Endpoint: target}
 	}
+	if ret.Scheme == "unix" {
+		// Add the "/" back in the unix case, so the unix resolver receives the
+		// actual endpoint.
+		ret.Endpoint = "/" + ret.Endpoint
+	}
 	return ret
 }

internal/grpcutil/target_test.go

@@ -32,17 +32,22 @@ func TestParseTarget(t *testing.T) {
 		{Scheme: "passthrough", Authority: "", Endpoint: "/unix/socket/address"},
 	} {
 		str := test.Scheme + "://" + test.Authority + "/" + test.Endpoint
-		got := ParseTarget(str)
+		got := ParseTarget(str, false)
 		if got != test {
-			t.Errorf("ParseTarget(%q) = %+v, want %+v", str, got, test)
+			t.Errorf("ParseTarget(%q, false) = %+v, want %+v", str, got, test)
+		}
+		got = ParseTarget(str, true)
+		if got != test {
+			t.Errorf("ParseTarget(%q, true) = %+v, want %+v", str, got, test)
 		}
 	}
 }
 
 func TestParseTargetString(t *testing.T) {
 	for _, test := range []struct {
-		targetStr string
-		want      resolver.Target
+		targetStr      string
+		want           resolver.Target
+		wantWithDialer resolver.Target
 	}{
 		{targetStr: "", want: resolver.Target{Scheme: "", Authority: "", Endpoint: ""}},
 		{targetStr: ":///", want: resolver.Target{Scheme: "", Authority: "", Endpoint: ""}},
@@ -70,10 +75,23 @@ func TestParseTargetString(t *testing.T) {
 		{targetStr: "a:/b", want: resolver.Target{Scheme: "", Authority: "", Endpoint: "a:/b"}},
 		{targetStr: "a//b", want: resolver.Target{Scheme: "", Authority: "", Endpoint: "a//b"}},
 		{targetStr: "a://b", want: resolver.Target{Scheme: "", Authority: "", Endpoint: "a://b"}},
+
+		// Unix cases without custom dialer.
+		// unix:[local_path] and unix:[/absolute] have different behaviors with
+		// a custom dialer, to prevent behavior changes with custom dialers.
+		{targetStr: "unix:domain", want: resolver.Target{Scheme: "unix", Authority: "", Endpoint: "domain"}, wantWithDialer: resolver.Target{Scheme: "", Authority: "", Endpoint: "unix:domain"}},
+		{targetStr: "unix:/domain", want: resolver.Target{Scheme: "unix", Authority: "", Endpoint: "/domain"}, wantWithDialer: resolver.Target{Scheme: "", Authority: "", Endpoint: "unix:/domain"}},
 	} {
-		got := ParseTarget(test.targetStr)
+		got := ParseTarget(test.targetStr, false)
 		if got != test.want {
-			t.Errorf("ParseTarget(%q) = %+v, want %+v", test.targetStr, got, test.want)
+			t.Errorf("ParseTarget(%q, false) = %+v, want %+v", test.targetStr, got, test.want)
+		}
+		if test.wantWithDialer == (resolver.Target{}) {
+			test.wantWithDialer = test.want
+		}
+		got = ParseTarget(test.targetStr, true)
+		if got != test.wantWithDialer {
+			t.Errorf("ParseTarget(%q, true) = %+v, want %+v", test.targetStr, got, test.wantWithDialer)
 		}
 	}
 }

internal/resolver/unix/unix.go

@@ -0,0 +1,49 @@
+/*
+ *
+ * Copyright 2020 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 unix implements a resolver for unix targets.
+package unix
+
+import (
+	"google.golang.org/grpc/internal/transport/networktype"
+	"google.golang.org/grpc/resolver"
+)
+
+const scheme = "unix"
+
+type builder struct{}
+
+func (*builder) Build(target resolver.Target, cc resolver.ClientConn, _ resolver.BuildOptions) (resolver.Resolver, error) {
+	cc.UpdateState(resolver.State{Addresses: []resolver.Address{networktype.Set(resolver.Address{Addr: target.Endpoint}, "unix")}})
+	return &unixResolver{}, nil
+}
+
+func (*builder) Scheme() string {
+	return scheme
+}
+
+type unixResolver struct {
+}
+
+func (*unixResolver) ResolveNow(resolver.ResolveNowOptions) {}
+
+func (*unixResolver) Close() {}
+
+func init() {
+	resolver.Register(&builder{})
+}

internal/transport/http2_client.go

@@ -33,6 +33,7 @@ import (
 	"golang.org/x/net/http2"
 	"golang.org/x/net/http2/hpack"
 	"google.golang.org/grpc/internal/grpcutil"
+	"google.golang.org/grpc/internal/transport/networktype"
 
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/credentials"
@@ -137,11 +138,18 @@ type http2Client struct {
 	connectionID uint64
 }
 
-func dial(ctx context.Context, fn func(context.Context, string) (net.Conn, error), addr string) (net.Conn, error) {
+func dial(ctx context.Context, fn func(context.Context, string) (net.Conn, error), addr resolver.Address, useProxy bool, grpcUA string) (net.Conn, error) {
 	if fn != nil {
-		return fn(ctx, addr)
+		return fn(ctx, addr.Addr)
 	}
-	return (&net.Dialer{}).DialContext(ctx, "tcp", addr)
+	networkType := "tcp"
+	if n, ok := networktype.Get(addr); ok {
+		networkType = n
+	}
+	if networkType == "tcp" && useProxy {
+		return proxyDial(ctx, addr.Addr, grpcUA)
+	}
+	return (&net.Dialer{}).DialContext(ctx, networkType, addr.Addr)
 }
 
 func isTemporary(err error) bool {
@@ -172,7 +180,7 @@ func newHTTP2Client(connectCtx, ctx context.Context, addr resolver.Address, opts
 		}
 	}()
 
-	conn, err := dial(connectCtx, opts.Dialer, addr.Addr)
+	conn, err := dial(connectCtx, opts.Dialer, addr, opts.UseProxy, opts.UserAgent)
 	if err != nil {
 		if opts.FailOnNonTempDialError {
 			return nil, connectionErrorf(isTemporary(err), err, "transport: error while dialing: %v", err)

internal/transport/networktype/networktype.go

@@ -0,0 +1,46 @@
+/*
+ *
+ * Copyright 2020 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 networktype declares the network type to be used in the default
+// dailer. Attribute of a resolver.Address.
+package networktype
+
+import (
+	"google.golang.org/grpc/resolver"
+)
+
+// keyType is the key to use for storing State in Attributes.
+type keyType string
+
+const key = keyType("grpc.internal.transport.networktype")
+
+// Set returns a copy of the provided address with attributes containing networkType.
+func Set(address resolver.Address, networkType string) resolver.Address {
+	address.Attributes = address.Attributes.WithValues(key, networkType)
+	return address
+}
+
+// Get returns the network type in the resolver.Address and true, or "", false
+// if not present.
+func Get(address resolver.Address) (string, bool) {
+	v := address.Attributes.Value(key)
+	if v == nil {
+		return "", false
+	}
+	return v.(string), true
+}