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jackhab
Asked: 2014-03-12 04:08:38 +0800 CST

Disable TCP checksum offloading on KVM virtual network

  • 772

I have a virtual network for connecting KVM guests with the host.

I need to disable TCP checksum offloading on this network. The ethtool works fine but I want to disable it permanently and I could not find anything in virsh or QEMU documentation. Adding /etc/sysconfig/network-scripts/ifcfg-virbr1 file with the corresponding options also does not work.

virtual-machines

3 Answers

  1. Best Answer

    ethtool -K eth0 tso off in rc.local or the vm startup script. You could probably do it as a libvirt hook too

    • 3

  2. I recommend doing this with a udev rule. I put this in /etc/udev/rules.d/81-bridge.rules:

    ACTION=="add", SUBSYSTEM=="net", NAME=="virbr*", RUN+="/sbin/ethtool -K $env{INTERFACE} tx off"

    More sophisticated approaches are possible, depending on your needs.

    • 2

  3. You can disable it in the guest's interface xml:

    <driver>
      <host csum='off'/>
      <guest csum='off'/>
    </driver>

    Refer to https://libvirt.org/formatdomain.html#setting-nic-driver-specific-options

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