[IP]: Introduce ip_hdrlen()

For the common sequence "skb->nh.iph->ihl * 4", removing a good number of open
coded skb->nh.iph uses, now to go after the rest...

Just out of curiosity, here are the idioms found to get the same result:

skb->nh.iph->ihl << 2
skb->nh.iph->ihl<<2
skb->nh.iph->ihl * 4
skb->nh.iph->ihl*4
(skb->nh.iph)->ihl * sizeof(u32)

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/ipvs/ip_vs_proto_udp.c b/net/ipv4/ipvs/ip_vs_proto_udp.c
index 03f0a41..2cd9506 100644
--- a/net/ipv4/ipvs/ip_vs_proto_udp.c
+++ b/net/ipv4/ipvs/ip_vs_proto_udp.c
@@ -22,7 +22,7 @@
 #include <linux/udp.h>
 
 #include <net/ip_vs.h>
-
+#include <net/ip.h>
 
 static struct ip_vs_conn *
 udp_conn_in_get(const struct sk_buff *skb, struct ip_vs_protocol *pp,
@@ -56,7 +56,7 @@
 	struct ip_vs_conn *cp;
 	__be16 _ports[2], *pptr;
 
-	pptr = skb_header_pointer(skb, skb->nh.iph->ihl*4,
+	pptr = skb_header_pointer(skb, ip_hdrlen(skb),
 				  sizeof(_ports), _ports);
 	if (pptr == NULL)
 		return NULL;
@@ -82,7 +82,7 @@
 	struct ip_vs_service *svc;
 	struct udphdr _udph, *uh;
 
-	uh = skb_header_pointer(skb, skb->nh.iph->ihl*4,
+	uh = skb_header_pointer(skb, ip_hdrlen(skb),
 				sizeof(_udph), &_udph);
 	if (uh == NULL) {
 		*verdict = NF_DROP;
@@ -133,7 +133,7 @@
 		 struct ip_vs_protocol *pp, struct ip_vs_conn *cp)
 {
 	struct udphdr *udph;
-	unsigned int udphoff = (*pskb)->nh.iph->ihl * 4;
+	const unsigned int udphoff = ip_hdrlen(*pskb);
 
 	/* csum_check requires unshared skb */
 	if (!ip_vs_make_skb_writable(pskb, udphoff+sizeof(*udph)))
@@ -187,7 +187,7 @@
 		 struct ip_vs_protocol *pp, struct ip_vs_conn *cp)
 {
 	struct udphdr *udph;
-	unsigned int udphoff = (*pskb)->nh.iph->ihl * 4;
+	unsigned int udphoff = ip_hdrlen(*pskb);
 
 	/* csum_check requires unshared skb */
 	if (!ip_vs_make_skb_writable(pskb, udphoff+sizeof(*udph)))
@@ -239,7 +239,7 @@
 udp_csum_check(struct sk_buff *skb, struct ip_vs_protocol *pp)
 {
 	struct udphdr _udph, *uh;
-	unsigned int udphoff = skb->nh.iph->ihl*4;
+	const unsigned int udphoff = ip_hdrlen(skb);
 
 	uh = skb_header_pointer(skb, udphoff, sizeof(_udph), &_udph);
 	if (uh == NULL)