lnrpc: receive custom message

lnrpc/lightning.proto

@@ -563,6 +563,27 @@ service Lightning {
     */
     rpc SendCustomMessage (SendCustomMessageRequest)
         returns (SendCustomMessageResponse);
+
+    /* lncli: `subscribecustom`
+    SubscribeCustomMessages subscribes to a stream of incoming custom peer
+    messages.
+    */
+    rpc SubscribeCustomMessages (SubscribeCustomMessagesRequest)
+        returns (stream CustomMessage);
+}
+
+message SubscribeCustomMessagesRequest {
+}
+
+message CustomMessage {
+    // Peer from which the message originates
+    bytes peer = 1;
+
+    // Message type. This value will be in the custom range (>= 32768).
+    uint32 type = 2;
+
+    // Raw message data
+    bytes data = 3;
 }
 
 message SendCustomMessageRequest {