Re: [lwip-users] transfer stucks when snd_wnd is less than TCP_MSS

[Kieran Mansley]

On Fri, 2007-03-09 at 14:03 +0200, Vlad wrote:
> Ok, this is conversation between remote end and router:

> 04:29:45.297380 IP remote > router: . ack 80660 win 137 <nop,nop,timestamp 
> 73615212 4388653>
> [... here we hangs ..... ]
> 04:30:45.297688 IP remote > router: F 1:1(0) ack 80660 win 137 
> <nop,nop,timestamp 73675222 4388653>   <=== reset connection after 60 sec 
> timeout
> 
> I didn't see here nothing strange.

Other than it's advertising a tiny window (137 octets) and then never
sending a window update to increase it.

I notice though that the SYN has the tcp window scaling option in it -
I'm not sure if tcpdump is reporting the subsequent packets' window
sizes before or after applying this multiplier.  If this were the case
then it would be advertising >32KB of space, so no problem there.  In
that case it would definitely point the finger at whatever this thing is
in the middle: it doesn't send a window update and so the connection
stops.

One thing that lwIP might be able to do in a situation like this is to
send zero-window probes.  This isn't something we currently support
though.

Kieran