Updating error frowarding from Transfer failures

Author: alexlivekit

pkg/sip/protocol.go

@@ -375,7 +375,12 @@ func handleReferNotify(cseq uint32, status int, reason string, referCseq uint32,
 			Code:   livekit.SIPStatusCode(status),
 			Status: reason,
 		}
-		result = psrpc.NewErrorf(psrpc.Canceled, "call transfer failed: %w", st)
+		psrpcErrCode := psrpc.UpstreamServerError
+		if status < 500 || status >= 600 {
+			// Common 6xx codes: 603 Declined, 608 Rejected
+			psrpcErrCode = psrpc.UpstreamClientError
+		}
+		result = psrpc.NewErrorf(psrpcErrCode, "call transfer failed: %w", st)
 	}
 	select {
 	case referDone <- result:
@@ -413,6 +418,10 @@ func sipStatusForErrorCode(code psrpc.ErrorCode) sip.StatusCode {
 		return sip.StatusServiceUnavailable
 	case psrpc.Unauthenticated:
 		return sip.StatusUnauthorized
+	case psrpc.UpstreamServerError:
+		return sip.StatusBadGateway
+	case psrpc.UpstreamClientError:
+		return sip.StatusTemporarilyUnavailable
 	default:
 		return sip.StatusInternalServerError
 	}