[NETFILTER]: Keep conntrack reference until IPsec policy checks are done

Keep the conntrack reference until policy checks have been performed for
IPsec NAT support. The reference needs to be dropped before a packet is
queued to avoid having the conntrack module unloadable.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/input.c

@@ -225,6 +225,7 @@ int sctp_rcv(struct sk_buff *skb)
 
 	if (!xfrm_policy_check(sk, XFRM_POLICY_IN, skb, family))
 		goto discard_release;
+	nf_reset(skb);
 
 	ret = sk_filter(sk, skb, 1);
 	if (ret)