Re: Possible BUG in IPv4 TCP window handling, all recent 2.4.x/2.6.x kernels

[Ion Badulescu <lists@limebrokerage.com>]

Hi Alexey,

On Fri, 2 Sep 2005, Alexey Kuznetsov wrote:

> Anyway, ignoring this puzzle, the following patch for 2.4 should help.
>
>
> --- net/ipv4/tcp_input.c.orig	2003-02-20 20:38:39.000000000 +0300
> +++ net/ipv4/tcp_input.c	2005-09-02 22:28:00.845952888 +0400
> @@ -343,8 +343,6 @@
> 			app_win -= tp->ack.rcv_mss;
> 		app_win = max(app_win, 2U*tp->advmss);
>
> -		if (!ofo_win)
> -			tp->window_clamp = min(tp->window_clamp, app_win);
> 		tp->rcv_ssthresh = min(tp->window_clamp, 2U*tp->advmss);
> 	}
> }

I'm very happy to report that the above patch, applied to 2.6.12.6, seems 
to have cured the TCP window problem we were experiencing. I've been 
testing it extensively over the last 4 weeks, and I have yet to see any 
repeats of the previous behavior.

The TCP window now usually settles to around 4k (unscaled, 16k scaled),
which is smallish but good enough for our purposes.

Thanks,
-Ion