kernel-packages team mailing list archive

[Dan Streetman <dan.streetman@xxxxxxxxxxxxx>]

The result of this bug is, some VMs on an affected host system will
receive some packets, but not all, so in the VM it appears that the
network doesn't work.  This was specifically seen on Windows guests, in
this case.

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https://bugs.launchpad.net/bugs/1547680

Title:
  bonded interfaces in bridge do not have LRO turned off

Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Trusty:
  In Progress

Bug description:
  The "large receive offload" functionality of some NICs is not
  compatible with packet forwarding, because it modifies incoming
  packets in an irreversible way so the packets can't be correctly
  forwarded across the bridge.  When an interface is added to a bridge,
  the kernel automatically disables LRO via dev_disable_lro(), however
  in trusty this only works for normal interfaces (or vlan/macvlan)
  added to a bridge.  When interfaces belong to a bond, and the bond is
  added to a bridge, the interfaces' LRO is not disabled, and (some)
  incoming packets are modified by LRO and then lost when passing
  through the bridge.

  Commit fbe168ba91f7c327856f205699404284c2f09e36 updates
  dev_disable_lro() to work for all types of interfaces, including
  bonds.

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