[ofa-general] S/G support for connected mode?!

[Roland Dreier]

> I see the under connected mode the ipoib driver does not advertise S/G
> (NETIF_F_SG) support at its features bitmap. I understand that this would
> force the stack to do a copy in case the packet to be sent is made of
> page/fragments held at the SKB, etc.
>
> Doesn't it make sense to support S/G also for connected mode? I know that
> for CSUM support, if S/G is not supported, then the stack ignores the NETIF_F_IP_CSUM
> bit even if its being set by the nic, but does it apply also the other way -
> that is if CSUM is not supported then the stack ignores NETIF_F_SG? if yes, why?

As I understand things, F_SG is not used if F_IP_CSUM isn't set.
Because the network
stack would have to compute the the checksum anyway, so it basically
has to linearize
the skb anyway.

 - R.