net: openvswitch: fix TTL decrement exception action execution

net: openvswitch: fix TTL decrement exception action execution

[ Upstream commit 09d6217254c004f6237cc2c2bfe604af58e9a8c5 ]

Currently, the exception actions are not processed correctly as the wrong
dataset is passed. This change fixes this, including the misleading
comment.

In addition, a check was added to make sure we work on an IPv4 packet,
and not just assume if it's not IPv6 it's IPv4.

This was all tested using OVS with patch,
https://patchwork.ozlabs.org/project/openvswitch/list/?series=21639,
applied and sending packets with a TTL of 1 (and 0), both with IPv4
and IPv6.

Fixes: 69929d4c49e1 ("net: openvswitch: fix TTL decrement action netlink message format")
Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
Link: https://lore.kernel.org/r/160733569860.3007.12938188180387116741.stgit@wsfd-netdev64.ntdv.lab.eng.bos.redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>