[DISPATCH-1271] The LWS_CALLBACK_USER handler in http-libwebsockets.c is never triggered

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.5.0
• Assignee: Unassigned
• Reporter: Jiri Daněk
• Created: 25/Feb/19 08:51
• Updated: 10/Apr/19 06:33

Description

        lws_callback_all_protocol(hs->context, &protocols[1], LWS_CALLBACK_USER);
        lws_callback_all_protocol(hs->context, &protocols[2], LWS_CALLBACK_USER);

The problem is that lws_callback_all_protocol compares pointers to protocol structs with protocol parameter. They are never equal, because early on in listener_start, lws_create_vhost gets called, and it allocates a copy of the protocols array only for that vhost.

I expected that this will cause dispatch not to send heartbeats to clients connected over amqpws (since pn_transport_tick is not called). I tested that with qpid-jms, and it turned out that the heartbeats are flowing correctly. In other words, I am not aware of any user-visible bug caused by this. Is calling _tick unnecessary? What is it there for? I saw that dispatch is not sending its own heartbeats on the amqpws connections.

LWS_VISIBLE int
lws_callback_all_protocol(struct lws_context *context,
			  const struct lws_protocols *protocol, int reason)
{
	struct lws_context_per_thread *pt = &context->pt[0];
	unsigned int n, m = context->count_threads;
	struct lws *wsi;

	while (m--) {
		for (n = 0; n < pt->fds_count; n++) {
			wsi = wsi_from_fd(context, pt->fds[n].fd);
			if (!wsi)
				continue;
			if (wsi->protocol == protocol)
				protocol->callback(wsi, reason, wsi->user_space,
						   NULL, 0);
		}
		pt++;
	}

	return 0;
}

LWS_VISIBLE struct lws_vhost *
lws_create_vhost(struct lws_context *context,
		 const struct lws_context_creation_info *info)
{
    [...]
    
	/*
	 * give the vhost a unified list of protocols including the
	 * ones that came from plugins
	 */
	lwsp = lws_zalloc(sizeof(struct lws_protocols) * (vh->count_protocols +
				   context->plugin_protocol_count + 1),
			  "vhost-specific plugin table");
	if (!lwsp) {
		lwsl_err("OOM\n");
		return NULL;
	}

	m = vh->count_protocols;
	memcpy(lwsp, pcols, sizeof(struct lws_protocols) * m);

    [...]

	if (
#ifdef LWS_WITH_PLUGINS
	    (context->plugin_list) ||
#endif
	    context->options & LWS_SERVER_OPTION_EXPLICIT_VHOSTS)
		vh->protocols = lwsp;
	else {
		vh->protocols = pcols;
		lws_free(lwsp);
	}

    [...]
}

Issue Links

• is related to: DISPATCH-1270 Inapropriate use of CLOCK_REALTIME for periodic timer