Add a RequestInfo struct which initially is used for passing the full…

… request method (though could later be expanded to pass more info) so that things like GetRequestMetadata can be used to apply logic based on that data.

This is a fix for grpc#3019

credentials/credentials.go

@@ -34,6 +34,7 @@ import (
 
 	"github.com/golang/protobuf/proto"
 	"google.golang.org/grpc/credentials/internal"
+	ginternal "google.golang.org/grpc/internal"
 )
 
 // PerRPCCredentials defines the common interface for the credentials which need to
@@ -334,3 +335,32 @@ func cloneTLSConfig(cfg *tls.Config) *tls.Config {
 
 	return cfg.Clone()
 }
+
+// RequestInfo contains request data to be attached to the context passed along to GetRequestMetadata calls. This API is experimental.
+type RequestInfo struct {
+	// The method passed to Invoke or NewStream for this RPC. (For proto methods, this has the format "/some.Service/Method")
+	Method string
+}
+
+// requestInfoKey is a struct to be used as the key when attaching a RequestInfo to a context object.
+type requestInfoKey struct{}
+
+// RequestInfoFromContext extracts the RequestInfo from the context. This API is experimental.
+func RequestInfoFromContext(ctx context.Context) RequestInfo {
+	ri, ok := ctx.Value(requestInfoKey{}).(RequestInfo)
+	if !ok {
+		return RequestInfo{}
+	}
+	return ri
+}
+
+// withRequestInfo adds the supplied RequestInfo to the context. This API is experimental.
+func withRequestInfo(ctx context.Context, ri RequestInfo) context.Context {
+	return context.WithValue(ctx, requestInfoKey{}, ri)
+}
+
+func init() {
+	ginternal.NewRequestInfoContext = func(ctx context.Context, ri RequestInfo) context.Context {
+		return context.WithValue(ctx, requestInfoKey{}, ri)
+	}
+}

internal/internal.go

@@ -46,7 +46,8 @@ var (
 	// pointer to the wrapped Status proto for a given status.Status without a
 	// call to proto.Clone(). The returned Status proto should not be mutated by
 	// the caller.
-	StatusRawProto interface{} // func (*status.Status) *spb.Status
+	StatusRawProto        interface{} // func (*status.Status) *spb.Status
+	NewRequestInfoContext interface{} // (this avoids a circular dependency; we do it for other things like this already)
 )
 
 // HealthChecker defines the signature of the client-side LB channel health checking function.

internal/transport/http2_client.go

@@ -35,6 +35,7 @@ import (
 
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/internal"
 	"google.golang.org/grpc/internal/channelz"
 	"google.golang.org/grpc/internal/syscall"
 	"google.golang.org/grpc/keepalive"
@@ -547,6 +548,10 @@ func (t *http2Client) getCallAuthData(ctx context.Context, audience string, call
 // streams.
 func (t *http2Client) NewStream(ctx context.Context, callHdr *CallHdr) (_ *Stream, err error) {
 	ctx = peer.NewContext(ctx, t.getPeer())
+	ri := credentials.RequestInfo{
+		Method: callHdr.Method,
+	}
+	ctx = internal.NewRequestInfoContext.(func(context.Context, credentials.RequestInfo) context.Context)(ctx, ri)
 	headerFields, err := t.createHeaderFields(ctx, callHdr)
 	if err != nil {
 		return nil, err

internal/transport/transport_test.go

@@ -37,6 +37,7 @@ import (
 	"golang.org/x/net/http2"
 	"golang.org/x/net/http2/hpack"
 	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials"
 	"google.golang.org/grpc/internal/leakcheck"
 	"google.golang.org/grpc/internal/testutils"
 	"google.golang.org/grpc/status"
@@ -1809,3 +1810,28 @@ func TestHeaderTblSize(t *testing.T) {
 		t.Fatalf("expected len(limits) = 2 within 10s, got != 2")
 	}
 }
+
+// TestRequestInfoFoundInStreamContext tests whether data passed in as callheader data gets
+// propagated into the context object as a credentials.RequestInfo object.
+func TestRequestInfoFoundInStreamContext(t *testing.T) {
+	serverConfig := &ServerConfig{}
+	server, client, cancel := setUpWithOptions(t, 0, serverConfig, suspended, ConnectOptions{})
+	defer cancel()
+	defer server.stop()
+	defer client.Close()
+
+	ch := &CallHdr{
+		Method: "someService/Method",
+	}
+	ctx, ctxCancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer ctxCancel()
+
+	s, err := client.NewStream(ctx, ch)
+	if err != nil {
+		t.Fatalf("client.NewStream() failed: %v", err)
+	}
+	ri := credentials.RequestInfoFromContext(s.ctx)
+	if ch.Method != ri.Method {
+		t.Fatalf("RequestInfo.Method == %s; want %s", ri.Method, ch.Method)
+	}
+}

test/end2end_test.go

@@ -7484,3 +7484,32 @@ func parseCfg(s string) serviceconfig.Config {
 	}
 	return c
 }
+
+type methodTestCreds struct {
+	expectedMethod string
+}
+
+func (m methodTestCreds) GetRequestMetadata(ctx context.Context, uri ...string) (map[string]string, error) {
+	ri := credentials.RequestInfoFromContext(ctx)
+	return nil, status.Errorf(codes.Unknown, ri.Method)
+}
+
+func (m methodTestCreds) RequireTransportSecurity() bool {
+	return false
+}
+
+func (s) TestGRPCMethodAccessibleToCredsViaContextRequestInfo(t *testing.T) {
+	const wantMethod = "/grpc.testing.TestService/EmptyCall"
+	ss := &stubServer{}
+	if err := ss.Start(nil, grpc.WithPerRPCCredentials(methodTestCreds{"/grpc.testing.TestService/EmptyCall"})); err != nil {
+		t.Fatalf("Error starting endpoint server: %v", err)
+	}
+	defer ss.Stop()
+
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+	defer cancel()
+
+	if _, err := ss.client.EmptyCall(ctx, &testpb.Empty{}); status.Convert(err).Message() != wantMethod {
+		t.Fatalf("ss.client.EmptyCall(_, _) = _, %v; want _, _.Message()=%q", err, wantMethod)
+	}
+}