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

From: Jaco Kroon
Date: Fri Apr 01 2022 - 07:54:46 EST


On 2022/04/01 02:15, Florian Westphal wrote:

Incidently, I always find your initials to be interesting considering
(as far as I know) you work on netfilter firewall.

> Eric Dumazet <edumazet@xxxxxxxxxx> wrote:
>> Next step would be to attempt removing _all_ firewalls, especially not
>> common setups like yours.
>> conntrack had a bug preventing TFO deployment for a while, because
>> many boxes kept buggy kernel versions for years.
>> 356d7d88e088687b6578ca64601b0a2c9d145296 netfilter: nf_conntrack: fix
>> tcp_in_window for Fast Open
> Jaco could also try with
> net.netfilter.nf_conntrack_tcp_be_liberal=1
> and, if that helps, with liberal=0 and
> sysctl net.netfilter.nf_conntrack_log_invalid=6
> (check dmesg/syslog/nflog).

Our core firewalls already had nf_conntrack_tcp_be_liberal for other
reasons (asymmetric routing combined with conntrackd left-over if I
recall), so maybe that's why it got through there ... don't exactly want
to just flip that setting though, is there a way to log if it would have
dropped anything, without actually dropping it (yet)?

Will do this first, first need to confirm that I can reproduce in a dev

Kind Regards,