ACK: [SRU][N][PATCH 0/1] test_vxlan_vnifiltering.sh from ubuntu_kselftests_net failed on linux-oem-6.8 (with ipv6 default rdst)

[Andrei Gherzan]

On 2026/09/22 01:28PM, AceLan Kao via kernel-team wrote:
> From: "Chia-Lin Kao (AceLan)" <acelan.kao at canonical.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/2071590
> 
> [Impact]
> The ubuntu_kselftests_net test test_vxlan_vnifiltering.sh fails on and off.
> One subtest fails while the other 26 pass:
> 
> TEST: VM connectivity over vnifiltering vxlan (ipv4 default rdst) [ OK ]
> TEST: VM connectivity over vnifiltering vxlan (ipv6 default rdst) [ OK ]
> TEST: VM connectivity over vnifiltering vxlan pervni remote (ipv4 default rdst) [ OK ]
> TEST: VM connectivity over vnifiltering vxlan pervni remote (ipv6 default rdst) [FAIL]
> #
> Tests passed: 26
> Tests failed: 1
> not ok 1 selftests: net: test_vxlan_vnifiltering.sh # exit=1
> 
> Only the subtests that use an IPv6 underlay remote fail. Every IPv4 subtest
> passes in the same run.
> 
> The test sends one ping with a 1 second deadline right after it sets up the
> network. The IPv6 underlay addresses are still doing Duplicate Address
> Detection at that point, so the address cannot be used as a tunnel source
> yet. The single packet is dropped and the test gives up.
> 
> Slow machines lose this race more often. Seen on arm64 64k, lowlatency,
> lowlatency 64k, nvidia-lowlatency, azure and gcp instances. Also seen on
> amd64 gcp instances, so this is not arm64 only.
> 
> This is a test bug. The VXLAN driver is fine.
> 
> [Fix]
> Replace the single ping with slowwait, which retries every 100ms for up to
> 5 seconds. Also drop a pointless fixed "sleep 1".
> 
> 948670361c0c1 selftests: net: use slowwait to make sure IPv6 setup finished
> 
> Upstream in v6.17.
> 
> slowwait() already exists in tools/testing/selftests/net/lib.sh on the
> target branches, so no other patch is needed first.
> 
> [Test Plan]
> Run the test on a slow or loaded machine, arm64 or a small cloud instance:
> 
> $ cd tools/testing/selftests/net
> $ sudo ./test_vxlan_vnifiltering.sh
> 
> Repeat 20 times, the failure does not happen every run:
> 
> $ for i in $(seq 20); do sudo ./test_vxlan_vnifiltering.sh | tail -3; done
> 
> Without patch: "VM connectivity over vnifiltering vxlan pervni remote
> (ipv6 default rdst) [FAIL]" shows up in some runs, Tests failed: 1
> 
> With patch: all runs report Tests passed: 27, Tests failed: 0
> 
> [Where problems could occur]
> Could break test_vxlan_vnifiltering.sh itself. Nothing outside the test
> tree is touched, so no kernel code is at risk.
> 
> slowwait retries until the command succeeds. If a real VXLAN datapath bug
> shows up later, this test now waits 5 seconds per ping before reporting it,
> so a broken run takes longer to finish. In the worst case, a full failure
> goes from a few seconds to about 50 seconds.
> 
> If slowwait is missing from lib.sh on a branch, the test would abort with
> "slowwait: command not found" and every connectivity subtest would fail.
> Check lib.sh has slowwait() before applying.
> 
> [Other Info]
> Test only change, no kernel code changes.
> 
> Already in noble hwe-6.17 and hwe-7.0. Missing from noble 6.8 (master)
> which is the only branch still hitting this.
> 
> Hangbin Liu (1):
>   selftests: net: use slowwait to make sure IPv6 setup finished
> 
>  tools/testing/selftests/net/test_vxlan_vnifiltering.sh | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)

Acked-by: Andrei Gherzan <andrei.gherzan at canonical.com>

-- 
Andrei Gherzan
gpg: rsa4096/D4D94F67AD0E9640
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