max_inflight_messages=1 broken on Mosquitto-1.6.3

[xmas79]

Hello,
it seems that max_inflight_messages=1 is broken on the new mosquitto-1.6.3 broker implementation. A client (tried with mosquitto_pub v1.6.3 and older releases as well) publishing messages with QoS2 to a such configured broker will just stuck waiting for a reply.

As I understand it, the problem seems related to outgoing QoS quota being decremented for the CONNACK packet, leaving the broker without any quota left for answering subsequent requests.

A simple "dialogue" between a broker and a client:

Log from Mosquitto Broker:

1562328636: New connection from 192.168.0.87 on port 1883.
1562328636: New client connected from 192.168.0.87 as mosquitto_pub (p2, c1, k60).
1562328636: No will message specified.
1562328636: Sending CONNACK to mosquitto_pub (0, 0)
1562328636: Received PUBLISH from mosquitto_pub (d0, q2, r0, m1, 'test', ... (5 bytes))
1562328696: Received PINGREQ from mosquitto_pub
1562328696: Sending PINGRESP to mosquitto_pub

Log from mosquitto_pub:

mosquitto_pub -h 192.168.0.88 -t "test" -q 2 -d -m "hello" -i "mosquitto_pub"
Client mosquitto_pub sending CONNECT
Client mosquitto_pub received CONNACK (0)
Client mosquitto_pub sending PUBLISH (d0, q2, r0, m1, 'test', ... (5 bytes))
Client mosquitto_pub sending PINGREQ
Client mosquitto_pub received PINGRESP

[ilovemilk]

I have the same problem. The issue also exists in version 1.6.2.

[ralight]

Thanks for the reports both, I believe this is now fixed in the fixes branch.