Misalignment, MIPS, and ip_hdr(skb)->version

Jason A. Donenfeld Jason at zx2c4.com
Thu Dec 8 23:20:04 CET 2016


Hi David,

On Thu, Dec 8, 2016 at 1:37 AM, David Miller <davem at davemloft.net> wrote:
> You really have to land the IP header on a proper 4 byte boundary.
>
> I would suggest pushing 3 dummy garbage bytes of padding at the front
> or the end of your header.

Are you sure 3 bytes to get 4 byte alignment is really the best? I was
thinking that adding 1 byte to get 2 byte alignment might be better,
since it would then ensure that the subsequent TCP header winds up
being 4 byte aligned. Or is this in fact not the desired trade off,
and so I should stick with the 3 bytes you suggested?

Jason


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