[NETFILTER] Inherit masq_index to slave connections

masq_index is used for cleanup in case the interface address changes
(such as a dialup ppp link with dynamic addreses). Without this patch,
slave connections are not evicted in such a case, since they don't inherit
masq_index.

Signed-off-by: Harald Welte <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ipv4/netfilter/ip_conntrack_core.c

···
 #ifdef CONFIG_IP_NF_CONNTRACK_MARK
 		conntrack->mark = exp->master->mark;
 #endif
+#if defined(CONFIG_IP_NF_TARGET_MASQUERADE) || \
+    defined(CONFIG_IP_NF_TARGET_MASQUERADE_MODULE)
+		/* this is ugly, but there is no other place where to put it */
+		conntrack->nat.masq_index = exp->master->nat.masq_index;
+#endif
 		nf_conntrack_get(&conntrack->master->ct_general);
 		CONNTRACK_STAT_INC(expect_new);
 	} else {