Fix persistent Websockets clients not receiving messages.

This occurs after they reconnect, having sent DISCONNECT
on a previous session.

Closes eclipse#1227. Thanks to usernametaken.

ChangeLog.txt

@@ -18,6 +18,8 @@ Broker:
  #1276.
 - Add 'extern "C"' on mosquitto_broker.h and mosquitto_plugin.h for C++ plugin
  writing. Closes #1290.
+- Fix persistent Websockets clients not receiving messages after they
+ reconnect, having sent DISCONNECT on a previous session. Closes #1227.
 
 Client library:
 - Fix typo causing build error on Windows when building without TLS support.

src/loop.c

@@ -614,12 +614,19 @@ void do_disconnect(struct mosquitto_db *db, struct mosquitto *context, int reaso
 #ifdef WITH_EPOLL
  struct epoll_event ev;
 #endif
+#ifdef WITH_WEBSOCKETS
+ bool is_duplicate = false;
+#endif
 
  if(context->state == mosq_cs_disconnected){
  return;
  }
 #ifdef WITH_WEBSOCKETS
  if(context->wsi){
+ if(context->state == mosq_cs_duplicate){
+ is_duplicate = true;
+ }
+
  if(context->state != mosq_cs_disconnecting && context->state != mosq_cs_disconnect_with_will){
  context__set_state(context, mosq_cs_disconnect_ws);
  }
@@ -636,7 +643,15 @@ void do_disconnect(struct mosquitto_db *db, struct mosquitto *context, int reaso
  context->sock = INVALID_SOCKET;
  context->pollfd_index = -1;
  }
- context__remove_from_by_id(db, context);
+ if(is_duplicate){
+ /* This occurs if another client is taking over the same client id.
+ * It is important to remove this from the by_id hash here, so it
+ * doesn't leave us with multiple clients in the hash with the same
+ * id. Websockets doesn't actually close the connection here,
+ * unlike for normal clients, which means there is extra time when
+ * there could be two clients with the same id in the hash. */
+ context__remove_from_by_id(db, context);
+ }
  }else
 #endif
  {