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From: Neal Cardwell <ncardwell@google.com>
To: Bernd <ecki@zusammenkunft.net>
Cc: netdev <netdev@vger.kernel.org>, Eric Dumazet <edumazet@google.com>
Subject: Re: [PATCH net 2/4] tcp: tcp_fragment() should apply sane memory limits
Date: Fri, 2 Aug 2019 15:14:38 -0400
Message-ID: <CADVnQy=dvmksVaDu61+w-qtv2g_iNbWPFgbSJDtx9QaasmHonw@mail.gmail.com> (raw)
In-Reply-To: <CABOR3+yUiu1BzCojFQFADUKc5BT2-Ew_j7KFNpjP8WoMYZ+SMA@mail.gmail.com>

On Fri, Aug 2, 2019 at 3:03 PM Bernd <ecki@zusammenkunft.net> wrote:
>
> Hello,
>
> While analyzing a aborted upload packet capture I came across a odd
> trace where a sender was not responding to a duplicate SACK but
> sending further segments until it stalled.
>
> Took me some time until I remembered this fix, and actually the
> problems started since the security fix was applied.
>
> I see a high counter for TCPWqueueTooBig - and I don’t think that’s an
> actual attack.
>
> Is there a probability for triggering the limit with connections with
> big windows and large send buffers and dropped segments? If so what
> would be the plan? It does not look like it is configurable. The trace
> seem to have 100 (filled) inflight segments.
>
> Gruss
> Bernd
> --
> http://bernd.eckenfels.net

What's the exact kernel version you are using?

Eric submitted a patch recently that may address your issue:
   tcp: be more careful in tcp_fragment()
  https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git/commit/?id=b617158dc096709d8600c53b6052144d12b89fab

Would you be able to test your workload with that commit
cherry-picked, and see if the issue still occurs?

That commit was targeted to many stable releases, so you may be able
to pick up that fix from a stable branch.

cheers,
neal

  reply index

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-02 19:02 Bernd
2019-08-02 19:14 ` Neal Cardwell [this message]
2019-08-02 19:58   ` Bernd
2019-08-14 14:41     ` Marcelo Ricardo Leitner
  -- strict thread matches above, loose matches on Subject: below --
2019-06-17 17:03 [PATCH net 0/4] tcp: make sack processing more robust Eric Dumazet
2019-06-17 17:03 ` [PATCH net 2/4] tcp: tcp_fragment() should apply sane memory limits Eric Dumazet
2019-06-17 17:14   ` Jonathan Lemon
2019-06-18  0:18   ` Christoph Paasch
2019-06-18  2:28     ` Eric Dumazet
2019-06-18  3:19       ` Christoph Paasch
2019-06-18  3:44         ` Eric Dumazet
2019-06-18  3:53           ` Christoph Paasch
2019-06-18  4:08             ` Eric Dumazet
2019-07-10 18:23         ` Prout, Andrew - LLSC - MITLL
2019-07-10 18:28           ` Eric Dumazet
2019-07-10 18:53             ` Prout, Andrew - LLSC - MITLL
2019-07-10 19:26               ` Eric Dumazet
2019-07-11  7:28                 ` Christoph Paasch
2019-07-11  9:19                   ` Eric Dumazet
2019-07-11 18:26                     ` Michal Kubecek
2019-07-11 18:50                       ` Eric Dumazet
2019-07-11 10:18                   ` Eric Dumazet
2019-07-11 17:14                 ` Prout, Andrew - LLSC - MITLL
2019-07-11 18:28                   ` Eric Dumazet
2019-07-11 19:04                     ` Jonathan Lemon
2019-07-12  7:05                       ` Eric Dumazet
2019-07-16 15:13                   ` Prout, Andrew - LLSC - MITLL

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