802.1Q Double-Tagging

Linux Kernel Upstream Release Notes v5.17

This section describes the configuration of 802.1Q double-tagging support to the hypervisor per Virtual Function (VF). The Virtual Machine (VM) attached to the VF (via SR-IOV) can send traffic with or without C-VLAN. Once a VF is configured to VST encapsulation, the adapter's hardware will insert C-VLAN to any packet from the VF to the physical port. On the receive side, the adapter hardware will strip the C-VLAN from any packet coming from the wire to that VF.

  1. Add the required C-VLAN tag (on the hypervisor) per port per VF. There are two ways to add the C-VLAN:

    1. By using sysfs:

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      echo '100:0:802.1q' > /sys/class/net/ens1f0/device/sriov/0/vlan

    2. By using the ip link command (available only when using the latest Kernel version):

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      ip link set dev ens1f0 vf 0 vlan 100

      Check the configuration using the ip link show command:

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      # ip link show ens1f0 ens1f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT qlen 1000 link/ether ec:0d:9a:44:37:84 brd ff:ff:ff:ff:ff:ff vf 0 MAC 00:00:00:00:00:00, vlan 100, spoof checking off, link-state auto, trust off vf 1 MAC 00:00:00:00:00:00, spoof checking off, link-state auto, trust off vf 2 MAC 00:00:00:00:00:00, spoof checking off, link-state auto, trust off vf 3 MAC 00:00:00:00:00:00, spoof checking off, link-state auto, trust off vf 4 MAC 00:00:00:00:00:00, spoof checking off, link-state auto, trust off

  2. Create a VLAN interface on the VM and add an IP address.

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    # ip link add link ens5 ens5.40 type vlan protocol 802.1q id 40 # ip addr add 42.134.135.7/16 brd 42.134.255.255 dev ens5.40 # ip link set dev ens5.40 up

  3. To verify the setup, run ping between the two VMs and open Wireshark or tcpdump to capture the packet.

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