Bart De Schuymer wrote:

Hi Lennert,

skb->protocol is not set for locally generated packets when the packet
is still in the IP stack. I don't know what happens with it after the IP
stack is finished with the packet.

It is set shortly before the packet leaves the IP stack,
in ip_finish_output. This is after LOCAL_OUT, but before
POST_ROUTING. So your fix looks fine.

The comment in skbuff.h says "packet protocol from driver", from which I
tend to conclude that skb->protocol is only set by drivers when a packet
enters the box. Too bad stuff like this isn't clearly spelled out, the
FIXME for the dst field has been sitting there for probably more than a
year too. Anyway, it wouldn't hurt if the skb->protocol field always
held the right value.

The IP stack knows it's IP anyway :) After that it has to
hold the right value.

Regards
Patrick