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

[Neal Cardwell]

On Sat, Apr 2, 2022 at 10:14 AM Florian Westphal <fw@xxxxxxxxx> wrote:
>
> Jaco Kroon <jaco@xxxxxxxxx> wrote:
> > Including sysctl net.netfilter.nf_conntrack_log_invalid=6- which
> > generates lots of logs, something specific I should be looking for?  I
> > suspect these relate:
> >
> > [Sat Apr  2 10:31:53 2022] nf_ct_proto_6: SEQ is over the upper bound
> > (over the window of the receiver) IN= OUT=bond0
> > SRC=2c0f:f720:0000:0003:d6ae:52ff:feb8:f27b
> > DST=2a00:1450:400c:0c08:0000:0000:0000:001a LEN=2928 TC=0 HOPLIMIT=64
> > FLOWLBL=867133 PROTO=TCP SPT=48920 DPT=25 SEQ=2689938314 ACK=4200412020
> > WINDOW=447 RES=0x00 ACK PSH URGP=0 OPT (0101080A2F36C1C120EDFB91) UID=8
> > GID=12
>
> I thought this had "liberal mode" enabled for tcp conntrack?
> The above implies its off.

Jaco's email said: "Our core firewalls already had
nf_conntrack_tcp_be_liberal". But this log is from the client machine
itself, not the core firewall machines. AFAICT it seems the client
machine does not have "liberal mode" enabled.

neal