netfilter: nf_nat: fix action not being set for all ct states

This fixes openvswitch's handling of nat packets in the related state.

In nf_ct_nat_execute(), which is called from nf_ct_nat(), ICMP/ICMPv6
packets in the IP_CT_RELATED or IP_CT_RELATED_REPLY state, which have
not been dropped, will follow the goto, however the placement of the
goto label means that updating the action bit field will be bypassed.

This causes ovs_nat_update_key() to not be called from ovs_ct_nat()
which means the openvswitch match key for the ICMP/ICMPv6 packet is not
updated and the pre-nat value will be retained for the key, which will
result in the wrong openflow rule being matched for that packet.

Move the goto label above where the action bit field is being set so
that it is updated in all cases where the packet is accepted.

Fixes: ebddb1404900 ("net: move the nat function to nf_nat_ovs for ovs and tc")
Signed-off-by: Brad Cowie <brad@faucet.nz>
Reviewed-by: Simon Horman <horms@kernel.org>
Acked-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Aaron Conole <aconole@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net: move the nat function to nf_nat_ovs for ovs and tc

There are two nat functions are nearly the same in both OVS and
TC code, (ovs_)ct_nat_execute() and ovs_ct_nat/tcf_ct_act_nat().

This patch creates nf_nat_ovs.c under netfilter and moves them
there then exports nf_ct_nat() so that it can be shared by both
OVS and TC, and keeps the nat (type) check and nat flag update
in OVS and TC's own place, as these parts are different between
OVS and TC.

Note that in OVS nat function it was using skb->protocol to get
the proto as it already skips vlans in key_extract(), while it
doesn't in TC, and TC has to call skb_protocol() to get proto.
So in nf_ct_nat_execute(), we keep using skb_protocol() which
works for both OVS and TC contrack.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Aaron Conole <aconole@redhat.com>
Acked-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>