netfilter: restart search if moved to other chain

netfilter: restart search if moved to other chain

commit 95a8d19f28e6b29377a880c6264391a62e07fccc upstream.

In case nf_conntrack_tuple_taken did not find a conflicting entry
check that all entries in this hash slot were tested and restart
in case an entry was moved to another chain.

Reported-by: Eric Dumazet <edumazet@google.com>
Fixes: ea781f197d6a ("netfilter: nf_conntrack: use SLAB_DESTROY_BY_RCU and get rid of call_rcu()")
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
[bwh: Backported to 3.2:
 - Adjust context
 - Use NF_CT_STAT_INC(), not the _ATOMIC variant, since we disable BHs]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>