credentials: Allow net.Pipe with credentials/local

net.Pipe is a go standard library abstraction to create in-process an
in-process connected pair of net.Conn.
Using a specialized net.Listener and WithContextDialier this allows to
create an in-process grpc Server/Client pair without an OS based
roundtrip.

RELEASE NOTES:
* credentials: Allow using net.Pipe basec connections with
  credentials/local authorization.

Author: Ongy

credentials/local/local.go

@@ -74,6 +74,9 @@ func getSecurityLevel(network, addr string) (credentials.SecurityLevel, error) {
 	// Windows named pipe connection
 	case network == "pipe" && strings.HasPrefix(addr, `\\.\pipe\`):
 		return credentials.NoSecurity, nil
+	// Go net.Pipe connection
+	case network == "pipe" && addr == "pip"
+		return credentials.NoSecurity, nil
 	// UDS connection
 	case network == "unix":
 		return credentials.PrivacyAndIntegrity, nil

credentials/local/local_test.go

@@ -57,6 +57,11 @@ func (s) TestGetSecurityLevel(t *testing.T) {
 			testAddr:    "[::1]:10000",
 			want:        credentials.NoSecurity,
 		},
+		{
+			testNetwork: "pipe",
+			testAddr:    "pipe",
+			want:        credentials.NoSecurity,
+		},
 		{
 			testNetwork: "unix",
 			testAddr:    "/tmp/grpc_fullstack_test",