Cathy Zhou wrote:
>> > > My 10GbE NIC does not do HW VLAN tag insertion/removal (we
>> concluded
>> > > there was no performance benefit). On several OSes, I'm forced to
>> > > claim the device does HW VLAN tag support (and do tag
>> > > insertion/removal in the driver) to gain support for the 4 bytes of
>> > > "margin" (1518, 9018), and/or to get the OS to trust that my device
>> > > can offload checksum in combination with VLAN frames.
>> > > > Hmm, can we make the assumption that supporting margin of
>> greater than 4 > always implies that a driver can handle offload
>> checksum for VLAN frames? I > am not sure whether this is always true.
>>
>> Maybe there could be a capability flag for checksum offload in
>> combination with vlan? There seem to be plenty of bits free in the
>> 32-bit cap data for MAC_CAPAB_HCKSUM.
>>
>
> This sounds possible, or at least a similar mechanism is needed to
> make sure hardware checksum works fine for VLAN frames.
Today, checksumming support is not optional, at least for partial
checksums. If you claim to support them, you have to do both VLAN and
regular on outbound. This means that drivers which can't do this have
to do soft checksum in the driver code on transmit. Kind of a pain in
the arse.
On receive, its no big deal, because any frame can be sent up either
with or without a checksum tag, and the OS will figure it out without
consulting NIC capabilities.
-- Garrett
>
> Thanks!
> - Cathy
_______________________________________________
networking-discuss mailing list
[email protected]
