Sebastien Roy wrote:
> Cathy Zhou wrote:
>> I am adding this in the PSARC fast-track, and the diffs are posted
>> below. The following link is also updated
>>
>> http://opensolaris.org/os/project/clearview/uv_addendum_fasttrack
>
> ...
>
>> + ** HCKSUM_VLANCKSUM bit of MAC_CAPAB_HCKSUM
>> +
>> + The HCKSUM_VLANCKSUM bit can be set in combination with other
>> + MAC_CAPAB_HCKSUM bits (HCKSUM_INET_PARTIAL, HCKSUM_INET_FULL_V4,
>> + HCKSUM_INET_FULL_V6, or/and HCKSUM_IPHDRCKSUM), to indicate that
>> + a MAC is capable of doing the specified hardware checksum
>> offloading
>> + for VLAN frames.
>
> Can you add to the specification an explanation of why this is needed?
> In other words, GLDv3 previously (wrongly) assumed that all devices
> which claimed to support various flavors of hardware checksum offload
> could so with VLAN-tagged frames. This flag is presumably needed for
> some potential drivers out there that do hardware checksum, but only for
> non-vlan-tagged frames (correct?).
>
How about this:
** HCKSUM_VLANCKSUM bit of MAC_CAPAB_HCKSUM
Today, GLDv3 assumes that all Ethernet MACs that claim HW checksum
offloading capabilities could do HW checksum for both untagged
and VLAN-tagged packets. But in reality, there are some drivers that
can only support HW checksum for packets whose true payload is at the
right offset (reported in DL_INFO_ACK). For example, they will not be
able to handle HW checksum for VLAN-tagged packets, as VLAN tag are
embeded at the start of the payload section, which result in the true
payload starting at a different offset.
The HCKSUM_VLANCKSUM bit can be set in combination with other
MAC_CAPAB_HCKSUM bits (HCKSUM_INET_PARTIAL, HCKSUM_INET_FULL_V4,
HCKSUM_INET_FULL_V6, or/and HCKSUM_IPHDRCKSUM), to indicate that
a MAC is not capable of doing the specified HW checksum offloading
for packets with extra VLAN tag headers.
> Do we know of any such drivers offhand?
I don't know NICs enough to know whether there is such hardware.
But for those legacy drivers unified to GLDv3, UV always chooses not to
advertise there HW checksum capability on VLAN streams, unless they support
VLAN PPA access themselves. Therefore, we need a bit to indicate it is
different from the traditional GLDv3 drivers (that can support HW checksum
for VLAN frames).
Thanks
- Cathy
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