On 10/20/25 10:56 AM, Frode Nordahl wrote:
> Hello all,
> 
> On 10/20/25 10:17, Dumitru Ceara via dev wrote:
>> Hi Frode,
>>
>> Sorry for reaching out directly but I figured it might be easier for you
>> to report this to the Ubuntu kernel development team (if not, I can also
>> try to open a launchpad bug myself but my knowledge in that area is
>> limited).
>>
>> Our OVN CI (in GitHub actions) is broken since Friday, e.g.:
>> https://github.com/ovn-org/ovn/actions/runs/18622640352/job/53147265121
>>
>> These tests fail:
>>   252: system-ovn-kmod.at:1006 Load Balancer LS hairpin IPv6 UDP - larger 
>> than MTU -- parallelization=yes -- ovn_monitor_all=yes
>>        lb
>>   253: system-ovn-kmod.at:1006 Load Balancer LS hairpin IPv6 UDP - larger 
>> than MTU -- parallelization=yes -- ovn_monitor_all=no
>>        lb
>>
>> They fail with:
>>
>>   (cat datafile; sleep 3) | nc -6 -u 8800::0088 4040 -p 20000 -o 
>> udp_frag_test_c1.recvd
>> NS_EXEC_HEREDOC
>> Ncat: Version 7.92 ( https://nmap.org/ncat )
>> Ncat: Listening on 4200::1:2021
>> stderr:
>> Ncat: Message too long.
>> stdout:
>>
>> As there were no OVN (or OVS) user space changes that could've caused
>> this (the last good run was on Thursday) we had a look at other
>> components that might have changed.
>>
>> It seems there was a GitHub ubuntu:24.04 runner image change that
>> happened since.  The new version is:
>>
>>    Image: ubuntu-24.04
>>    Version: 20251014.76.1
>>    Included Software: 
>> https://github.com/actions/runner-images/blob/ubuntu24/20251014.76/images/ubuntu/Ubuntu2404-Readme.md
>>    Image Release: 
>> https://github.com/actions/runner-images/releases/tag/ubuntu24%2F20251014.76
>>
>> which uses kernel version 6.14.0-1012-azure.
>>
>> Our last known good CI runs were using kernel
>> version 6.11.0-1018-azure.
>>
>> I had a look at the linux-image-unsigned-6.14.0-1012-azure Ubuntu
>> kernel sources and it seems that we there might be a patch missing
>> there.  I think we might be hitting the same issue as in:
>>
>> https://lore.kernel.org/stable/[email protected]/
>>
>> Checking the unpacked Ubuntu kernel sources it seems the 6.11 kernel
>> didn't have the buggy patch:
>> a18dfa9925b9ef6107ea3aa5814ca3c704d34a8a "ipv6: save dontfrag in cork"
>>
>> While kernel 6.14.0-1012-azure includes the code from the buggy patch
>> but only has the first of the followup fixes:
>> - 54580ccdd8a9c6821fd6f72171d435480867e4c3 "ipv6: remove leftover ip6 cookie 
>> initializer"
>> - 096208592b09c2f5fc0c1a174694efa41c04209d "ipv6: replace ipcm6_init calls 
>> with ipcm6_init_sk" <<< the code doesn't have this commit.
>>
>> Would you happen to have some time to double check my findings and maybe
>> report this to the Ubuntu kernel team?
>>
>> Also, it seems ovn-kubernetes CI is affected by this too:
>> https://github.com/ovn-kubernetes/ovn-kubernetes/actions/runs/18638480933/job/53134392523#step:16:4399
>>
>> [FAIL] [sig-network] Networking Granular Checks: Services [It] should be 
>> able to handle large requests: udp [sig-network]
> 
> Thank you for your detailed report, Dumitru.  This appears to affect the 
> regular generic kernel in Ubuntu 25.04 (Plucky Puffin) too [0].
> 
> The good news is that I don't see this in more recent kernels, so "all" we 
> have to do is to find the missing commit ;)
> 
> 0: 
> https://autopkgtest.ubuntu.com/results/autopkgtest-plucky/plucky/amd64/o/ovn/20251002_082225_66b13@/log.gz
> 

AFAICT, 6.14.0-1014-azure should have the missing commit:
  "ipv6: replace ipcm6_init calls with ipcm6_init_sk"

I opened this ticket for GHA for now:
  https://github.com/actions/runner-images/issues/13190

Best regards, Ilya Maximets.
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