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

Hi Alexey,

Do you think this will also fix Ion's issue with small window size never 
going back up ?

Thanks
Guillaume.

Alexey Kuznetsov wrote:

Hello!

 

quoted

Here are the dumps...
   

I see. It has nothing to do with clamping. Indeed this is a very old bug.
Frankly speaking I even was aware about this at some moment
(so that if the sender was Linux it would not happen. It was fixed there. :-))

With such small window sender is forced to send a tiny segment
via SWS override timer and receiver is confused in believing this
is sender's mss, so the result is broken SWS avoidance.

I think you can cure it deleting the following lines:

                   /* If PSH is not set, packet should be
                    * full sized, provided peer TCP is not badly broken.
                    * This observation (if it is correct 8)) allows
                    * to handle super-low mtu links fairly.
                    */
                   (len >= TCP_MIN_MSS + sizeof(struct tcphdr) &&
                    !(tcp_flag_word(skb->h.th)&TCP_REMNANT))) {


in tcp_input.c:tcp_measure_rcv_mss() at receiver side.


Alexey

 

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Guillaume Autran
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MRV Communications, Inc.
Tel: (978) 952-4932 office
E-mail: gautran@mrv.com
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