All of lore.kernel.org
 help / color / mirror / Atom feed
From: Willy Tarreau <w@1wt.eu>
To: Klavs Klavsen <kl@vsen.dk>
Cc: Eric Dumazet <eric.dumazet@gmail.com>, netdev@vger.kernel.org
Subject: Re: TCP fast retransmit issues
Date: Wed, 26 Jul 2017 16:18:47 +0200	[thread overview]
Message-ID: <20170726141847.GC1737@1wt.eu> (raw)
In-Reply-To: <fd335e0a0c914b9c42a754da2d24b1c3@vsen.dk>

On Wed, Jul 26, 2017 at 04:08:19PM +0200, Klavs Klavsen wrote:
> Grabbed on both ends.
> 
> http://blog.klavsen.info/fast-retransmit-problem-junos-linux (updated to new
> dump - from client scp'ing)
> http://blog.klavsen.info/fast-retransmit-problem-junos-linux-receiving-side
> (receiving host)

So bingo, Eric guessed right, the client's sequence numbers are translated
on their way to/from the server, but the SACK fields are not :

Server :
15:59:54.292867 IP (tos 0x8, ttl 64, id 15878, offset 0, flags [DF], proto TCP (6), length 64)
    192.168.32.44.22 > 62.242.222.50.35002: Flags [.], cksum 0xfe2b (incorrect -> 0xce0e), seq 1568063538, ack 3903858556,
    win 10965, options [nop,nop,TS val 529899820 ecr 774272020,nop,nop,sack 1 {3903859904:3903861252}], length 0

Client :
15:59:54.297388 IP (tos 0x8, ttl 56, id 15878, offset 0, flags [DF], proto TCP (6), length 64)
    192.168.32.44.22 > 62.242.222.50.35002: Flags [.], cksum 0xbb2c (correct), seq 1568063538, ack 2684453645,
    win 10965, options [nop,nop,TS val 529899820 ecr 774272020,nop,nop,sack 1 {3903859904:3903861252}], length 0

To there's very likely a broken firewall in the middle that is waiting for
a bug fix, or to have its feature disabled. Sometimes it can also happen
on firewalls performing some SYN proxying except that it would mangle the
server's sequence numbers instead of the client ones.

Willy

  reply	other threads:[~2017-07-26 14:18 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-07-26 11:07 TCP fast retransmit issues Klavs Klavsen
2017-07-26 11:49 ` Eric Dumazet
2017-07-26 12:18   ` Klavs Klavsen
2017-07-26 13:31     ` Eric Dumazet
2017-07-26 13:42       ` Willy Tarreau
2017-07-26 14:32         ` Eric Dumazet
2017-07-26 14:50           ` Willy Tarreau
2017-07-26 16:43             ` Neal Cardwell
2017-07-26 17:06               ` Neal Cardwell
2017-07-26 18:38                 ` Neal Cardwell
2017-07-26 19:02                   ` Neal Cardwell
2017-07-28 22:54                     ` Neal Cardwell
2017-08-01  3:17                       ` Neal Cardwell
2017-07-28  6:53           ` Christoph Paasch
2017-07-26 14:08       ` Klavs Klavsen
2017-07-26 14:18         ` Willy Tarreau [this message]
2017-07-26 14:25           ` Klavs Klavsen
2017-07-26 14:38             ` Willy Tarreau
2017-07-28  6:36               ` Klavs Klavsen
2017-07-28  7:27                 ` Willy Tarreau
2017-08-17 13:20                   ` Jeremy Harris

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20170726141847.GC1737@1wt.eu \
    --to=w@1wt.eu \
    --cc=eric.dumazet@gmail.com \
    --cc=kl@vsen.dk \
    --cc=netdev@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.