netfilter: conntrack: allow sctp hearbeat after connection re-use

netfilter: conntrack: allow sctp hearbeat after connection re-use

BugLink: https://bugs.launchpad.net/bugs/1896824
[ Upstream commit cc5453a5b7e90c39f713091a7ebc53c1f87d1700 ]

If an sctp connection gets re-used, heartbeats are flagged as invalid
because their vtag doesn't match.

Handle this in a similar way as TCP conntrack when it suspects that the
endpoints and conntrack are out-of-sync.

When a HEARTBEAT request fails its vtag validation, flag this in the
conntrack state and accept the packet.

When a HEARTBEAT_ACK is received with an invalid vtag in the reverse
direction after we allowed such a HEARTBEAT through, assume we are
out-of-sync and re-set the vtag info.

v2: remove left-over snippet from an older incarnation that moved
    new_state/old_state assignments, thats not needed so keep that
    as-is.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: William Breathitt Gray <william.gray@canonical.com>