[ovs-dev] [PATCH] Support vlan_group workaround implemented in XenServer kernels.

[Jesse Gross]

On Tue, Mar 15, 2011 at 12:18 PM, Ben Pfaff <blp at nicira.com> wrote:
> Some Linux network drivers support a feature called "VLAN acceleration",
> associated with a data structure called a "vlan_group".  A vlan_group is,
> abstractly, a dictionary that maps from a VLAN ID (in the range 0...4095)
> to a VLAN device, that is, a Linux network device associated with a
> particular VLAN, e.g. "eth0.9" for VLAN 9 on eth0.
>
> Some drivers that support VLAN acceleration have bugs that fall roughly
> into the following categories:
>
>    * Some NICs strip VLAN tags on receive if no vlan_group is registered,
>      so that the tag is completely lost.
>
>    * Some drivers size their receive buffers based on whether a vlan_group
>      is enabled, meaning that a maximum size packet with a VLAN tag will
>      not fit if a vlan_group is not configured.
>
>    * On transmit some drivers expect that VLAN acceleration will be used
>      if it is available (which can only be done if a vlan_group is
>      configured).  In these cases, the driver may fail to parse the packet
>      and correctly setup checksum offloading and/or TSO.
>
> The correct long term solution is to fix these driver bugs.  To cope until
> then, we have prepared a patch to the Linux kernel network stack that works
> around these problems.  This commit adds support for the workaround
> implemented by that patch.
>
> Signed-off-by: Ben Pfaff <blp at nicira.com>

Acked-by: Jesse Gross <jesse at nicira.com>