client: fix "unix" scheme handling for some corner cases

internal/grpcutil/target.go

@@ -21,6 +21,7 @@
 package grpcutil
 
 import (
+	"net/url"
 	"strings"
 
 	"google.golang.org/grpc/resolver"
@@ -60,9 +61,45 @@ func ParseTarget(target string, skipUnixColonParsing bool) (ret resolver.Target)
 		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
+		if !skipUnixColonParsing {
+			// Add the "/" back in the unix case, so the unix resolver receives the
+			// actual endpoint.
+			ret.Endpoint = "/" + ret.Endpoint
+		} else {
+			// Custom dialer should receive "unix:///[...]".
+			return resolver.Target{Endpoint: target}
+		}
 	}
 	return ret
 }
+
+// ParseDialTarget returns the network and address to pass to dialer
+func ParseDialTarget(target string) (string, string) {
+	net := "tcp"
+
+	m1 := strings.Index(target, ":")
+	m2 := strings.Index(target, ":/")
+
+	// handle unix:addr which will fail with url.Parse
+	if m1 >= 0 && m2 < 0 {
+		if n := target[0:m1]; n == "unix" {
+			return n, target[m1+1:]
+		}
+	}
+	if m2 >= 0 {
+		t, err := url.Parse(target)
+		if err != nil {
+			return net, target
+		}
+		scheme := t.Scheme
+		addr := t.Path
+		if scheme == "unix" {
+			if addr == "" {
+				addr = t.Host
+			}
+			return scheme, addr
+		}
+	}
+
+	return net, target
+}

internal/grpcutil/target_test.go

@@ -70,17 +70,21 @@ func TestParseTargetString(t *testing.T) {
 		// If we can only parse part of the target.
 		{targetStr: "://", want: resolver.Target{Scheme: "", Authority: "", Endpoint: "://"}},
 		{targetStr: "unix://domain", want: resolver.Target{Scheme: "", Authority: "", Endpoint: "unix://domain"}},
+		{targetStr: "unix://a/b/c", want: resolver.Target{Scheme: "unix", Authority: "a", Endpoint: "/b/c"}, wantWithDialer: resolver.Target{Scheme: "", Authority: "", Endpoint: "unix://a/b/c"}},
 		{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"}},
 		{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"}},
+		// unix:[local_path], unix:[/absolute], and unix://[/absolute] have different
+		// behaviors with a custom dialer, to prevent behavior changes with custom dialers.
+		{targetStr: "unix:a/b/c", want: resolver.Target{Scheme: "unix", Authority: "", Endpoint: "a/b/c"}, wantWithDialer: resolver.Target{Scheme: "", Authority: "", Endpoint: "unix:a/b/c"}},
+		{targetStr: "unix:/a/b/c", want: resolver.Target{Scheme: "unix", Authority: "", Endpoint: "/a/b/c"}, wantWithDialer: resolver.Target{Scheme: "", Authority: "", Endpoint: "unix:/a/b/c"}},
+		{targetStr: "unix:///a/b/c", want: resolver.Target{Scheme: "unix", Authority: "", Endpoint: "/a/b/c"}, wantWithDialer: resolver.Target{Scheme: "", Authority: "", Endpoint: "unix:///a/b/c"}},
+
+		{targetStr: "passthrough:///unix:///a/b/c", want: resolver.Target{Scheme: "passthrough", Authority: "", Endpoint: "unix:///a/b/c"}},
 	} {
 		got := ParseTarget(test.targetStr, false)
 		if got != test.want {

internal/resolver/unix/unix.go

@@ -20,6 +20,8 @@
 package unix
 
 import (
+	"fmt"
+
 	"google.golang.org/grpc/internal/transport/networktype"
 	"google.golang.org/grpc/resolver"
 )
@@ -29,6 +31,9 @@ const scheme = "unix"
 type builder struct{}
 
 func (*builder) Build(target resolver.Target, cc resolver.ClientConn, _ resolver.BuildOptions) (resolver.Resolver, error) {
+	if target.Authority != "" {
+		return nil, fmt.Errorf("invalid (non-empty) authority: %v", target.Authority)
+	}
 	cc.UpdateState(resolver.State{Addresses: []resolver.Address{networktype.Set(resolver.Address{Addr: target.Endpoint}, "unix")}})
 	return &nopResolver{}, nil
 }

internal/transport/http2_client.go

@@ -143,13 +143,16 @@ func dial(ctx context.Context, fn func(context.Context, string) (net.Conn, error
 		return fn(ctx, addr.Addr)
 	}
 	networkType := "tcp"
+	address := addr.Addr
 	if n, ok := networktype.Get(addr); ok {
 		networkType = n
+	} else {
+		networkType, address = grpcutil.ParseDialTarget(address)
 	}
 	if networkType == "tcp" && useProxy {
-		return proxyDial(ctx, addr.Addr, grpcUA)
+		return proxyDial(ctx, address, grpcUA)
 	}
-	return (&net.Dialer{}).DialContext(ctx, networkType, addr.Addr)
+	return (&net.Dialer{}).DialContext(ctx, networkType, address)
 }
 
 func isTemporary(err error) bool {