I repeated the test with tso off in the NIC. Process as follows:
1. Stop Exim, remove fastopen exclusion in transport conf.
2. ethtool -K eth0 tso off; ethtool -K eth0 tx off
3. Restart exim, retest.
Still experiencing timeouts in a similar fashion much as before - tshark
summary:
https://www.chromosphere.co.uk/wp-content/blogs.dir/1/files/2022/08/tfo_nic.txt
Of note, here's the output from ethtool --show-offload when I ran the test:
# ethtool --show-offload eth0
Features for eth0:
rx-checksumming: on [fixed]
tx-checksumming: off
tx-checksum-ipv4: off [fixed]
tx-checksum-ip-generic: off
tx-checksum-ipv6: off [fixed]
tx-checksum-fcoe-crc: off [fixed]
tx-checksum-sctp: off [fixed]
scatter-gather: on
tx-scatter-gather: on
tx-scatter-gather-fraglist: off [fixed]
tcp-segmentation-offload: off
tx-tcp-segmentation: off
tx-tcp-ecn-segmentation: off
tx-tcp-mangleid-segmentation: off
tx-tcp6-segmentation: off
generic-segmentation-offload: on
generic-receive-offload: on
large-receive-offload: off [fixed]
rx-vlan-offload: off [fixed]
tx-vlan-offload: off [fixed]
ntuple-filters: off [fixed]
receive-hashing: off [fixed]
highdma: on [fixed]
rx-vlan-filter: on [fixed]
vlan-challenged: off [fixed]
tx-lockless: off [fixed]
netns-local: off [fixed]
tx-gso-robust: on [fixed]
tx-fcoe-segmentation: off [fixed]
tx-gre-segmentation: off [fixed]
tx-gre-csum-segmentation: off [fixed]
tx-ipxip4-segmentation: off [fixed]
tx-ipxip6-segmentation: off [fixed]
tx-udp_tnl-segmentation: off [fixed]
tx-udp_tnl-csum-segmentation: off [fixed]
tx-gso-partial: off [fixed]
tx-tunnel-remcsum-segmentation: off [fixed]
tx-sctp-segmentation: off [fixed]
tx-esp-segmentation: off [fixed]
tx-udp-segmentation: off [fixed]
tx-gso-list: off [fixed]
fcoe-mtu: off [fixed]
tx-nocache-copy: off
loopback: off [fixed]
rx-fcs: off [fixed]
rx-all: off [fixed]
tx-vlan-stag-hw-insert: off [fixed]
rx-vlan-stag-hw-parse: off [fixed]
rx-vlan-stag-filter: off [fixed]
l2-fwd-offload: off [fixed]
hw-tc-offload: off [fixed]
esp-hw-offload: off [fixed]
esp-tx-csum-hw-offload: off [fixed]
rx-udp_tunnel-port-offload: off [fixed]
tls-hw-tx-offload: off [fixed]
tls-hw-rx-offload: off [fixed]
rx-gro-hw: on [fixed]
tls-hw-record: off [fixed]
rx-gro-list: off
macsec-hw-offload: off [fixed]
On Fri, 12 Aug 2022 at 07:09, Viktor Dukhovni via Exim-users <
exim-users@???> wrote:
> On Fri, Aug 12, 2022 at 06:30:21AM +0100, Andrew C Aitchison via
> Exim-users wrote:
>
> > > It looks *strongly* like an interoperability problem between the Linux
> > > kernel TCP implementation and the Google TCP/TLS termination
> front-ends,
> > > unless all the Exim users who lately somewhat regularly show up to
> > > report this issue are behind some as yet unidentified set of
> > > middle-boxes that break TCP state.
> > >
> > > It would perhaps be useful to also see any reports of success sending
> > > sufficiently large messages to Gmail from the reported Exim builds and
> > > Linux versions. If some users are not seeing any issues, then it would
> > > be good to know how their situation is differs.
> >
> > Might be good to know who is using openssl and who is using gnu-tls,
> > so that we can rule in or out the tls implementation.
>
> Surely irrelevant, this is a *TCP-layer* problem. If not in the Linux
> kernel, perhaps in the TCP offload in the network card.
>
> --
> Viktor.
>
> --
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>
