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

[Jason A. Donenfeld]

On Wed, Dec 7, 2016 at 8:52 PM, David Miller <davem at davemloft.net> wrote:
> The only truly difficult case to handle is GRE encapsulation.  Is
> that the situation you are running into?
>
> If not, please figure out what the header configuration looks like
> in the case that hits for you, and what the originating device is
> just in case it is a device driver issue.

My case is my own driver and my own protocol, which uses a 13 byte
header. I can, if absolutely necessary, change the protocol to add
another byte of padding. Or I can choose not to decrypt in place but
rather use a different trick, like overwriting the header during
decryption, though this removes some of the scatterwalk optimizations
when src and dst are the same. Or something else. I wrote the top
email of this thread inquiring about just exactly how bad it is to
call netif_rx(skb) when skb->data is unaligned.