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

David Laight [off-list ref] writes:

From: Måns Rullgård

quoted

Sent: 10 December 2016 13:25

...

quoted

I solved this problem in an Ethernet driver by copying the initial part
of the packet to an aligned skb and appending the remainder using
skb_add_rx_frag().  The kernel network stack only cares about the
headers, so the alignment of the packet payload doesn't matter.

That rather depends on where the packet payload ends up.
It is likely that it will be copied to userspace (or maybe
into some aligned kernel buffer).
In which case you get an expensive misaligned copy.

There's not much to be done about that.  The only other option is to
bypass DMA entirely, and that's sure to be even worse.

What do the hardware engineers think the ethernet interface will
be used for!

Ticking boxes in marketing material.

-- 
Måns Rullgård