[ovs-dev] [PATCH] Support vlan_group workaround implemented in XenServer kernels.
jesse at nicira.com
Wed Mar 16 14:18:55 PDT 2011
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>
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