Inflight messages limitation logic

[croja]

I little confused about how mechanism restricting amount of inflight messages implemented in mosquitto client library.

When someone publishes message to mosquitto client - it queued with some state - waiting for acknowledgment or invalid, depending on max inflight messages policy and current inflight messages count. When max inflight messages set to 0 then all incoming messages marked as waiting for acknowledgment, and no invalid messages possible in queue. It's OK for me. I don't understand handling of received acknowledgments - it checks queue looking for invalid messages, (to schedule such messages for writing), even if no such messages possible in queue.

lib/messages_mosq.c:251 _mosquitto_message_remove()

while(cur){
    if(mosq->max_inflight_messages == 0 || mosq->inflight_messages < mosq->max_inflight_messages){
        if(cur->msg.qos > 0 && cur->state == mosq_ms_invalid){
            // increase inflight messages count and schedule message for writing
        } else {
             return 
        }
    }
}

It doesn't beat the logic, but looks like some extra work: in case if max inflight messages is unlimited, it will iterate over whole queue of messages again and again, doing nothing useful (because cur->state == mosq_ms_invalid is never true in case when mosq->max_inflight_messages == 0).

This extra work executed under out_messages-mutex lock, so queueing of new messages blocked. I suggest following:

if(mosq->max_inflight_messages != 0 && mosq->inflight_messages < mosq->max_inflight_messages){
    // search for invalid messages
}