[Bug 2071590] Re: test_vxlan_vnifiltering.sh from ubuntu_kselftests_net failed on linux-oem-6.8 (with ipv6 default rdst)

** Tags added: kernel-daily-bug -- You received this bug notification because you are subscribed to linux in Ubuntu. Matching subscriptions: Bgg, Bmail, Nb https://bugs.launchpad.net/bugs/2071590 Title: test_vxlan_vnifiltering.sh from ubuntu_kselftests_net failed on linux- oem-6.8 (with ipv6 default rdst) Status in linux package in Ubuntu: Invalid Status in linux source package in Noble: Fix Committed Bug description: [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. ============================================== Test complains about: TAP version 13 1..1 # timeout set to 0 # selftests: net: test_vxlan_vnifiltering.sh # TEST: Create traditional vxlan device [ OK ] # TEST: Cannot create vnifilter device without external flag [ OK ] # TEST: Creating external vxlan device with vnifilter flag [ OK ] # TEST: Cannot set in-use vni id on vnifiltering device [ OK ] # TEST: Set new vni id on vnifiltering device [ OK ] # TEST: Create second external vxlan device with vnifilter flag [ OK ] # TEST: Cannot set in-use vni id on vnifiltering device [ OK ] # TEST: Set new vni id on vnifiltering device [ OK ] # TEST: Update vni id on vnifiltering device [ OK ] # TEST: Add new vni id on vnifiltering device [ OK ] # TEST: Set multicast group on existing vni [ OK ] # TEST: Set multicast group on existing vni [ OK ] # TEST: Cannot set vnifilter flag on a device [ OK ] # TEST: Cannot unset vnifilter flag on a device [ OK ] # 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] # TEST: VM connectivity over vnifiltering vxlan mgroup (ipv4 default rdst) [ OK ] # TEST: VM connectivity over vnifiltering vxlan mgroup (ipv6 default rdst) [ OK ] # TEST: VM connectivity over vnifiltering vxlan pervni mgroup (ipv4 default rdst) [ OK ] # TEST: VM connectivity over vnifiltering vxlan pervni mgroup (ipv6 default rdst) [ OK ] # TEST: VM connectivity over vnifiltering vxlan pervni remote mix (ipv4 default rdst) [ OK ] # TEST: VM connectivity over vnifiltering vxlan pervni remote mix (ipv6 default rdst) [ OK ] # TEST: VM connectivity over traditional vxlan (ipv4 default rdst) [ OK ] # TEST: VM connectivity over traditional vxlan (ipv6 default rdst) [ OK ] # TEST: VM connectivity over metadata nonfiltering vxlan (ipv4 default rdst) [ OK ] # # Tests passed: 26 # Tests failed: 1 not ok 1 selftests: net: test_vxlan_vnifiltering.sh # exit=1 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2071590/+subscriptions