Messages in this thread Patch in this message | | | Date | Fri, 2 Sep 2005 22:36:56 +0400 | From | Alexey Kuznetsov <> | Subject | Re: Possible BUG in IPv4 TCP window handling, all recent 2.4.x/2.6.x kernels |
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Hello!
> This is where things start going bad. The window starts shrinking from > 15340 all the way down to 2355 over the course of 0.3 seconds. Notice the > many duplicate acks that serve no purpose
These are not duplicate, TCP_NODELAY sender just starts flooding tiny segments, and those are normal ACKs acking those segments, note ACK field is not the same.
> Five minutes later the TCP window is still at 2355, .... > We are kind of stumped at this point, and it's proving to be a > show-stopping bug for our purposes, especially over WAN links that have > higher latency (for obvious reasons). Any kind of assistance would be > greatly appreciated.
I still do not know how the value of 184 is possible in your case, I would expect 730 as an absolute possible minumum. I see 9420 (2355*4). 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); } }
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