Re: [lwip-users] ACK Seq number problem with FIN ACK

[Simon Goldschmidt]

Am 09.11.2007 um 16:18 schrieb Jonathan Larmour:

> Paul Andrews wrote:
> > What happens is lwip will connect to a server, exchange some data  
> > then
> > the server will send a FIN ACK. However, when lwip ACKs this, the seq
> > number is not incremented. After this, it's a whole lot of FIN ACKs
> > going back and forth and we can never re-connect. It doesn't happen
> > every time, but usually after a while it will trigger.
>
> Sorry that no-one has been able to advise you, but to ensure this  
> issue
> doesn't get forgotten about, could you post it as a bug here please:
> https://savannah.nongnu.org/bugs/?func=additem&group=lwip
>
> Have you been able to identify anything which explains why it  
> happens some
> times and not others? Is the packet trace any different (e.g.  
> different
> order), other than the acks being the expected values when it works?

In fact I also noticed this. I was testing an outgoing TCP connection  
by just connecting to www.google.com and somtimes the ACK in the FIN 
+ACK from google wasn't recognized by lwIP, which lead to numerous FIN 
+ACKs being sent by the tcp_tmr.

The packets traces were different, but I didn't trace it down (I had  
no time and forgot about it until reading jifls mail). The only thing  
I know is the server was behaving differently. I'll investigate this  
further.

Simon