netdev - Re: linux 5.17.1 disregarding ACK values resulting in stalled TCP connections

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CANn89iJqKmjvJGtRHVumfP0T_SSa1uioFLgUvW+MF2ov2Ec2vQ@mail.gmail.com>
Date:   Sat, 2 Apr 2022 09:32:24 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     Neal Cardwell <ncardwell@...gle.com>
Cc:     Jaco Kroon <jaco@....co.za>, Florian Westphal <fw@...len.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>,
        Yuchung Cheng <ycheng@...gle.com>, Wei Wang <weiwan@...gle.com>
Subject: Re: linux 5.17.1 disregarding ACK values resulting in stalled TCP connections

On Sat, Apr 2, 2022 at 9:29 AM Neal Cardwell <ncardwell@...gle.com> wrote:
>
> FWIW those log entries indicate netfilter on the mail client machine
> dropping consecutive outbound skbs with 2*MSS of payload. So that
> explains the large consecutive losses of client data packets to the
> e-mail server. That seems to confirm my earlier hunch that those drops
> of consecutive client data packets "do not look like normal congestive
> packet loss".


This also explains why we have all these tiny 2-MSS packets in the pcap.

Under normal conditions, autocorking should kick in, allowing TCP to
build bigger TSO packets.