[NETFILTER]: nf_conntrack: Introduces nf_ct_get_tuplepr and uses it

nf_ct_get_tuple() requires the offset to transport header and that bothers
callers such as icmp[v6] l4proto modules. This introduces new function
to simplify them.

Signed-off-by: Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/netfilter/nf_conntrack_proto_icmp.c b/net/ipv4/netfilter/nf_conntrack_proto_icmp.c
index 0fe8fb0..b8b7999 100644
--- a/net/ipv4/netfilter/nf_conntrack_proto_icmp.c
+++ b/net/ipv4/netfilter/nf_conntrack_proto_icmp.c
@@ -136,40 +136,22 @@
 		 unsigned int hooknum)
 {
 	struct nf_conntrack_tuple innertuple, origtuple;
-	struct {
-		struct icmphdr icmp;
-		struct iphdr ip;
-	} _in, *inside;
 	struct nf_conntrack_l4proto *innerproto;
 	struct nf_conntrack_tuple_hash *h;
-	int dataoff;
 
 	NF_CT_ASSERT(skb->nfct == NULL);
 
-	/* Not enough header? */
-	inside = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_in), &_in);
-	if (inside == NULL)
-		return -NF_ACCEPT;
-
-	/* Ignore ICMP's containing fragments (shouldn't happen) */
-	if (inside->ip.frag_off & htons(IP_OFFSET)) {
-		pr_debug("icmp_error_message: fragment of proto %u\n",
-			 inside->ip.protocol);
+	/* Are they talking about one of our connections? */
+	if (!nf_ct_get_tuplepr(skb,
+			       skb_network_offset(skb) + ip_hdrlen(skb)
+						       + sizeof(struct icmphdr),
+			       PF_INET, &origtuple)) {
+		pr_debug("icmp_error_message: failed to get tuple\n");
 		return -NF_ACCEPT;
 	}
 
 	/* rcu_read_lock()ed by nf_hook_slow */
-	innerproto = __nf_ct_l4proto_find(PF_INET, inside->ip.protocol);
-
-	dataoff = ip_hdrlen(skb) + sizeof(inside->icmp);
-	/* Are they talking about one of our connections? */
-	if (!nf_ct_get_tuple(skb, dataoff, dataoff + inside->ip.ihl*4, PF_INET,
-			     inside->ip.protocol, &origtuple,
-			     &nf_conntrack_l3proto_ipv4, innerproto)) {
-		pr_debug("icmp_error_message: ! get_tuple p=%u",
-			 inside->ip.protocol);
-		return -NF_ACCEPT;
-	}
+	innerproto = __nf_ct_l4proto_find(PF_INET, origtuple.dst.protonum);
 
 	/* Ordinarily, we'd expect the inverted tupleproto, but it's
 	   been preserved inside the ICMP. */