[ARP]: Introduce the arp_hdr_len helper.

There are some place, that calculate the ARP header length. These
calculations are correct, but 
 a) some operate with "magic" constants,
 b) enlarge the code length (sometimes at the cost of coding style),
 c) are not informative from the first glance.

The proposal is to introduce a helper, that includes all the good
sides of these calculations.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 5 insertions, 14 deletions

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index 8e17f65f4002..69e80bd9774a 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -570,14 +570,13 @@ struct sk_buff *arp_create(int type, int ptype, __be32 dest_ip,
          *      Allocate a buffer
          */
 
-        skb = alloc_skb(sizeof(struct arphdr)+ 2*(dev->addr_len+4)
-                                + LL_RESERVED_SPACE(dev), GFP_ATOMIC);
+        skb = alloc_skb(arp_hdr_len(dev) + LL_RESERVED_SPACE(dev), GFP_ATOMIC);
         if (skb == NULL)
                 return NULL;
 
         skb_reserve(skb, LL_RESERVED_SPACE(dev));
         skb_reset_network_header(skb);
-        arp = (struct arphdr *) skb_put(skb,sizeof(struct arphdr) + 2*(dev->addr_len+4));
+        arp = (struct arphdr *) skb_put(skb, arp_hdr_len(dev));
         skb->dev = dev;
         skb->protocol = htons(ETH_P_ARP);
         if (src_hw == NULL)
@@ -916,9 +915,7 @@ static int arp_rcv(struct sk_buff *skb, struct net_device *dev,
                 goto freeskb;
 
         /* ARP header, plus 2 device addresses, plus 2 IP addresses.  */
-        if (!pskb_may_pull(skb, (sizeof(struct arphdr) +
-                                 (2 * dev->addr_len) +
-                                 (2 * sizeof(u32)))))
+        if (!pskb_may_pull(skb, arp_hdr_len(dev)))
                 goto freeskb;
 
         arp = arp_hdr(skb);
diff --git a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c
index c90e75a66e81..f84041d1f623 100644
--- a/net/ipv4/ipconfig.c
+++ b/net/ipv4/ipconfig.c
@@ -459,10 +459,7 @@ ic_rarp_recv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt
         if (rarp->ar_pro != htons(ETH_P_IP))
                 goto drop;
 
-        if (!pskb_may_pull(skb,
-                           sizeof(struct arphdr) +
-                           (2 * dev->addr_len) +
-                           (2 * 4)))
+        if (!pskb_may_pull(skb, arp_hdr_len(dev)))
                 goto drop;
 
         /* OK, it is all there and looks valid, process... */
diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index a7591ce344d2..9b5904486184 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -233,10 +233,7 @@ unsigned int arpt_do_table(struct sk_buff *skb,
         void *table_base;
         struct xt_table_info *private;
 
-        /* ARP header, plus 2 device addresses, plus 2 IP addresses.  */
-        if (!pskb_may_pull(skb, (sizeof(struct arphdr) +
-                                 (2 * skb->dev->addr_len) +
-                                 (2 * sizeof(u32)))))
+        if (!pskb_may_pull(skb, arp_hdr_len(skb->dev)))
                 return NF_DROP;
 
         indev = in ? in->name : nulldevname;