[PPPOE]: Introduce pppoe_hdr()

For consistency with all the other skb->nh.raw accessors.

Also do some really obvious simplifications in pppoe_recvmsg, well the
kfree_skb one is not so obvious, but free() and kfree() have the same behaviour
(hint :-) ).
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/pppoe.c

@@ -347,7 +347,7 @@ static int pppoe_rcv_core(struct sock *sk, struct sk_buff *skb)
 	struct pppox_sock *relay_po = NULL;
 
 	if (sk->sk_state & PPPOX_BOUND) {
-		struct pppoe_hdr *ph = (struct pppoe_hdr *) skb->nh.raw;
+		struct pppoe_hdr *ph = pppoe_hdr(skb);
 		int len = ntohs(ph->length);
 		skb_pull_rcsum(skb, sizeof(struct pppoe_hdr));
 		if (pskb_trim_rcsum(skb, len))
@@ -401,7 +401,7 @@ static int pppoe_rcv(struct sk_buff *skb,
 	if (!(skb = skb_share_check(skb, GFP_ATOMIC)))
 		goto out;
 
-	ph = (struct pppoe_hdr *) skb->nh.raw;
+	ph = pppoe_hdr(skb);
 
 	po = get_item((unsigned long) ph->sid, eth_hdr(skb)->h_source, dev->ifindex);
 	if (po != NULL)
@@ -433,7 +433,7 @@ static int pppoe_disc_rcv(struct sk_buff *skb,
 	if (!(skb = skb_share_check(skb, GFP_ATOMIC)))
 		goto out;
 
-	ph = (struct pppoe_hdr *) skb->nh.raw;
+	ph = pppoe_hdr(skb);
 	if (ph->code != PADT_CODE)
 		goto abort;
 
@@ -931,8 +931,6 @@ static int pppoe_recvmsg(struct kiocb *iocb, struct socket *sock,
 	struct sock *sk = sock->sk;
 	struct sk_buff *skb = NULL;
 	int error = 0;
-	int len;
-	struct pppoe_hdr *ph = NULL;
 
 	if (sk->sk_state & PPPOX_BOUND) {
 		error = -EIO;
@@ -949,19 +947,15 @@ static int pppoe_recvmsg(struct kiocb *iocb, struct socket *sock,
 	m->msg_namelen = 0;
 
 	if (skb) {
-		error = 0;
-		ph = (struct pppoe_hdr *) skb->nh.raw;
-		len = ntohs(ph->length);
+		struct pppoe_hdr *ph = pppoe_hdr(skb);
+		const int len = ntohs(ph->length);
 
 		error = memcpy_toiovec(m->msg_iov, (unsigned char *) &ph->tag[0], len);
-		if (error < 0)
-			goto do_skb_free;
-		error = len;
+		if (error == 0)
+			error = len;
 	}
 
-do_skb_free:
-	if (skb)
-		kfree_skb(skb);
+	kfree_skb(skb);
 end:
 	return error;
 }

include/linux/if_pppox.h

@@ -112,6 +112,13 @@ struct pppoe_hdr {
 } __attribute__ ((packed));
 
 #ifdef __KERNEL__
+#include <linux/skbuff.h>
+
+static inline struct pppoe_hdr *pppoe_hdr(const struct sk_buff *skb)
+{
+	return (struct pppoe_hdr *)skb->nh.raw;
+}
+
 struct pppoe_opt {
 	struct net_device      *dev;	  /* device associated with socket*/
 	int			ifindex;  /* ifindex of device associated with socket */