[NETFILTER]: Fix TCP header offset used in tcp_manip_pkt().

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

net/ipv4/netfilter/ip_nat_proto_tcp.c

@@ -105,7 +105,7 @@ tcp_manip_pkt(struct sk_buff **pskb,
 		return 0;
 
 	iph = (struct iphdr *)((*pskb)->data + iphdroff);
-	hdr = (struct tcphdr *)((*pskb)->data + iph->ihl*4);
+	hdr = (struct tcphdr *)((*pskb)->data + hdroff);
 
 	if (maniptype == IP_NAT_MANIP_SRC) {
 		/* Get rid of src ip and src pt */