ip -d link show segfaults on vxlan interfaces due to iproute2/kernel version mismatch (ubuntu-24.04, 20260209.23)

[FloSch62]

Description

The ip -d link show command segfaults (exit code 139 / SIGSEGV) when displaying VXLAN interface details on ubuntu-24.04 runners after the latest image update.

The issue appears after the kernel was upgraded to 6.14 while iproute2 remained at 6.1.0-1ubuntu6.2, leading to a mismatch in VXLAN netlink attribute parsing (IFLA_VXLAN_FAN_MAP).

Platforms affected

• Azure DevOps
• GitHub Actions - Standard Runners
• GitHub Actions - Larger Runners

Runner images affected

• Ubuntu 22.04
• Ubuntu 24.04
• Ubuntu Slim
• macOS 14
• macOS 14 Arm64
• macOS 15
• macOS 15 Arm64
• macOS 26
• macOS 26 Arm64
• Windows Server 2022
• Windows Server 2025
• Windows Server 2025 with Visual Studio 2026

Image version and build link

Failing image version: 20260209.23.1

• Kernel: 6.14.0-1017-azure
• iproute2: 6.1.0-1ubuntu6.2

Working image version: 20260201.15.1

• Kernel: 6.11.0-1018-azure
• iproute2: 6.1.0-1ubuntu6.2

Is it regression?

Yes, Last known working image:** 20260201.15.1 ; Link to last successful build: https://github.com/srl-labs/containerlab/actions/runs/21817143647/job/62941400831 ; Link to first failing build: https://github.com/srl-labs/containerlab/actions/runs/21909689330/job/63477453296

Expected behavior

ip -d link show dev <vxlan-interface> prints detailed VXLAN interface information and exits with status code 0.

Actual behavior

ip -d link show dev <vxlan-interface> crashes with exit code 139 (segmentation fault).

This breaks CI workflows that inspect VXLAN interfaces.

Repro steps

Run on an ubuntu-24.04 runner:

- run: |
    sudo ip link add vxlan-br type bridge
    sudo ip link set dev vxlan-br up
    sudo ip link add vx-test type vxlan id 101 remote 172.20.25.23 dev vxlan-br dstport 14788
    ip -d link show dev vx-test
    echo "exit code: $?"

[pshepherd10]

Thanks for the report and repro! Yea this looks like a regression caused by the Ubuntu 24.04 runner kernel update. There currently is no newer version of iproute2. As a workaround, consider trying this to get a working version as a temporary workaround:

- name: Build from src
        run: |
          wget https://launchpad.net/ubuntu/+archive/primary/+sourcefiles/iproute2/6.18.0-1ubuntu1/iproute2_6.18.0.orig.tar.xz
          wget https://launchpad.net/ubuntu/+archive/primary/+sourcefiles/iproute2/6.18.0-1ubuntu1/iproute2_6.18.0.orig.tar.xz
          wget https://launchpad.net/ubuntu/+archive/primary/+sourcefiles/iproute2/6.18.0-1ubuntu1/iproute2_6.18.0-1ubuntu1.debian.tar.xz
          wget https://launchpad.net/ubuntu/+archive/primary/+sourcefiles/iproute2/6.18.0-1ubuntu1/iproute2_6.18.0-1ubuntu1.dsc
          
          sudo sed -i 's/^Types: deb$/Types: deb deb-src/' /etc/apt/sources.list.d/ubuntu.sources
          sudo apt-get update
          sudo apt-get install dh-package-notes libnsl-dev
          
          sudo apt-get build-dep iproute2
          dpkg-source -x iproute2_6.18.0-1ubuntu1.dsc
          cd iproute2-6.18.0
          dpkg-buildpackage -us -uc
          sudo dpkg -i ../iproute2_6.18.0-1ubuntu1_amd64.deb
      - name: dump version of ip
        run: |
          sudo ip link add vxlan0 type vxlan id 42 dev eth0 dstport 4789 group 239.1.1.1
          sudo ip link set vxlan0 up
          ip -d link show vxlan0

We plan on pinning and deploying the previous working image version this week if the above mitigation doesn't work.

[saltiyazan]

Hi @pshepherd10 ,
Any progress on this issue?