Re: [lwip-users] Accepting TCP connections when out of PCBs

[address@hidden]

address@hidden wrote
> I have a question regarding accepting client PCBs on a listening PCB:
>
> Is it by design that the stack aborts an already connected PCB, if it fails to 
> allocate a free TCP PCB from the memory pools to handle pending connection 
> requests?

Yes, that's by design. Note that pcbs have a priority (pcb->prio) and 
only connections that have a lower priority (value) than the newly 
allocated pcb will be closed.

One could argue though, whether this check should be changed from 
'old_prio <= new_prio' to 'old_prio < new_prio'. However, this would 
break existing applications relying on this behaviour.

> How do I protect my existing connections in this 'out of memory' situation?

If you don't want them to get aborted, set the priority higher than the 
priority of the listening pcb.

> I'm using RAW API 1.4.1 with memory pools enabled and backlog disabled.

Hmm... lwIP 1.4.1 has not been 'officially' released, yet. I think I 
tagged the git repository, though...

Simon