[NETFILTER]: nf_nat: autoload IPv4 connection tracking

Without this patch, the generic L3 tracker would kick in
if nf_conntrack_ipv4 was not loaded before nf_nat, which
would lead to translation problems with ICMP errors.

NAT does not make sense without IPv4 connection tracking
anyway, so just add a call to need_ipv4_conntrack().
Signed-off-by: NJan Engelhardt <jengelh@computergmbh.de>
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/netfilter/nf_nat_core.c

@@ -629,6 +629,8 @@ static int __init nf_nat_init(void)
 	size_t i;
 	int ret;
 
+	need_ipv4_conntrack();
+
 	ret = nf_ct_extend_register(&nat_extend);
 	if (ret < 0) {
 		printk(KERN_ERR "nf_nat_core: Unable to register extension\n");