From: Eric Dumazet <dada1@xxxxxxxxxxxxx>
Date: Thu, 23 Jun 2005 00:13:21 +0200
> I also found that the memcpy() done to copy the data to the new skb suffers
> from misalignment.
> This is because of skb_reserve(skbs, 2) that was done on both skb, and
> memcpy() (at least on x86_64) doing long word copies without checking
> alignment of source or destination.
> Maybe we could :
> 1) make sure both skbs had the same skb_reserve() of 2 (thats not clear
> because tg3.c mixes the '2' and tp->rx_offset,
> and according to a comment :
> rx_offset != 2 iff this is a 5701 card running
> in PCI-X mode
> 2) and do :
> - memcpy(copy_skb->data, skb->data, len);
> + memcpy(copy_skb->data-2, skb->data-2, len+2);
> (That is copy 2 more bytes, but gain aligned copy to speedup memcpy())
Yep, good idea. Actually, the driver should be using
NET_IP_ALIGN for rx_offset unless it's the 5701 card running
in PCI-X mode case.