From 52eae659832ba529f97290e1ce0572cea66b5939 Mon Sep 17 00:00:00 2001
From: Gilbert Wong <gilbertwong96@icloud.com>
Date: Mon, 8 Oct 2018 20:02:32 +0800
Subject: [PATCH] Fix topic_name validation bug Prior to this change, Prior to
 this change, the validation for the mqtt5.0 publish packet which both
 contains zero-length topic name and topic alias is wrong.

This change fix this bug.
---
 src/emqx_packet.erl | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/emqx_packet.erl b/src/emqx_packet.erl
index 1d1e29c6a..7c51688dc 100644
--- a/src/emqx_packet.erl
+++ b/src/emqx_packet.erl
@@ -55,6 +55,8 @@ validate(?UNSUBSCRIBE_PACKET(PacketId, TopicFilters)) ->
     validate_packet_id(PacketId)
         andalso ok == lists:foreach(fun emqx_topic:validate/1, TopicFilters);
 
+validate(?PUBLISH_PACKET(_QoS, <<>>, #{'Topic-Alias':= _I}, _)) ->
+    true;
 validate(?PUBLISH_PACKET(_QoS, <<>>, _, _, _)) ->
     error(topic_name_invalid);
 validate(?PUBLISH_PACKET(_QoS, Topic, _, Properties, _)) ->