[mosquitto-dev] persistent_client_expiration, async connections with lib

[Steve Prior <sprior@xxxxxxxxxxxx>]

So far I've posted two questions here and haven't received any response 
whatsoever, don't know if I'm asking bad questions - I hope not.

Previously I started with the assumption that I've started a mosquitto 
connection with clean_session=true with an  async connection, then called 
mosquitto_loop_start().

I had noticed that in the event that the broker unexpectedly disconnects a 
connection it appears that libmosquitto will attempt to reconnect.  Since I had 
used clean_session=true it also appears that any existing subscriptions will be 
lost (am I correct in this???) which means that a client with subscriptions will 
need to set an on_disconnect callback not to reconnect, but to resubscribe to 
previous subscriptions.  This seems a little odd to me if correct that the 
library tries to be so helpful about re-establishing the connection but then 
requires manual intervention to resubscribe.

If this is true it would seem to encourage clients to connect with 
clean_session=false.  But then according to the documentation for mosquitto.conf 
for the persistent_client_expiration option "Badly designed clients may set 
clean session to false whilst using a randomly generated client id."  This 
sounds like unless this option is set clients which set clean session to false 
whilst using a randomly generated client id effectively set up a potential 
resource leak on the server which opens up a denial of service attack.

I'm trying to follow along with the code and intent here and could really use 
some clarification.

Steve Prior