How to disable TX checksum offloading

Checksum offloading on a network card may cause issues in some setups, including on VMware instances and in Cilium. If you encounter such issues, take the following steps:

1. Disable TX checksum offloading by running the following commands:

   • For server machines:

     cat <<EOF | sudo tee /etc/systemd/system/disable-checksum.service
     [Unit]
     Description=Disable TX Checksum Offload
     Before=rke2-server.service
     Wants=network-online.target
     After=network-online.target
     
     [Service]
     Type=oneshot
     ExecStart=/bin/bash -c "INTERFACE=$(awk '$2 == 00000000 { print $1; exit }' /proc/net/route); ethtool -K \$INTERFACE tx-checksum-ip-generic off || ethtool -K cilium_host tx-checksum-ip-generic off || true"
     RemainAfterExit=true
     
     [Install]
     WantedBy=multi-user.target
     EOF
     sudo systemctl enable disable-checksum

   • For agent machines:

     cat <<EOF | sudo tee /etc/systemd/system/disable-checksum.service
     [Unit]
     Description=Disable TX Checksum Offload
     Before=rke2-agent.service
     Wants=network-online.target
     After=network-online.target
     
     [Service]
     Type=oneshot
     ExecStart=/bin/bash -c "INTERFACE=$(awk '$2 == 00000000 { print $1; exit }' /proc/net/route); ethtool -K \$INTERFACE tx-checksum-ip-generic off || ethtool -K cilium_host tx-checksum-ip-generic off || true"
     RemainAfterExit=true
     
     [Install]
     WantedBy=multi-user.target
     EOF
     sudo systemctl enable disable-checksum

2. Restart the affected instance by taking the steps described in Starting and shutting down a node.