netfilter: move skb_gso_segment into nfnetlink_queue module
skb_gso_segment is expensive, so it would be nice if we could
avoid it in the future. However, userspace needs to be prepared
to receive larger-than-mtu-packets (which will also have incorrect
l3/l4 checksums), so we cannot simply remove it.
The plan is to add a per-queue feature flag that userspace can
set when binding the queue.
The problem is that in nf_queue, we only have a queue number,
not the queue context/configuration settings.
This patch should have no impact other than the skb_gso_segment
call now being in a function that has access to the queue config
data.
A new size attribute in nf_queue_entry is needed so
nfnetlink_queue can duplicate the entry of the gso skb
when segmenting the skb while also copying the route key.
The follow up patch adds switch to disable skb_gso_segment when
queue config says so.
Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>