[SCTP]: Introduce sctp_hdr()

For consistency with all the other skb->h.raw accessors.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/sctp.h

@@ -63,6 +63,15 @@ typedef struct sctphdr {
 	__be32 checksum;
 } __attribute__((packed)) sctp_sctphdr_t;
 
+#ifdef __KERNEL__
+#include <linux/skbuff.h>
+
+static inline struct sctphdr *sctp_hdr(const struct sk_buff *skb)
+{
+	return (struct sctphdr *)skb->h.raw;
+}
+#endif
+
 /* Section 3.2.  Chunk Field Descriptions. */
 typedef struct sctp_chunkhdr {
 	__u8 type;

net/sctp/input.c

@@ -79,14 +79,10 @@ static void sctp_add_backlog(struct sock *sk, struct sk_buff *skb);
 /* Calculate the SCTP checksum of an SCTP packet.  */
 static inline int sctp_rcv_checksum(struct sk_buff *skb)
 {
-	struct sctphdr *sh;
-	__u32 cmp, val;
 	struct sk_buff *list = skb_shinfo(skb)->frag_list;
-
-	sh = (struct sctphdr *) skb->h.raw;
-	cmp = ntohl(sh->checksum);
-
-	val = sctp_start_cksum((__u8 *)sh, skb_headlen(skb));
+	struct sctphdr *sh = sctp_hdr(skb);
+	__u32 cmp = ntohl(sh->checksum);
+	__u32 val = sctp_start_cksum((__u8 *)sh, skb_headlen(skb));
 
 	for (; list; list = list->next)
 		val = sctp_update_cksum((__u8 *)list->data, skb_headlen(list),
@@ -138,7 +134,7 @@ int sctp_rcv(struct sk_buff *skb)
 	if (skb_linearize(skb))
 		goto discard_it;
 
-	sh = (struct sctphdr *) skb->h.raw;
+	sh = sctp_hdr(skb);
 
 	/* Pull up the IP and SCTP headers. */
 	__skb_pull(skb, skb_transport_offset(skb));
@@ -905,7 +901,7 @@ static struct sctp_association *__sctp_rcv_init_lookup(struct sk_buff *skb,
 	struct sctp_association *asoc;
 	union sctp_addr addr;
 	union sctp_addr *paddr = &addr;
-	struct sctphdr *sh = (struct sctphdr *) skb->h.raw;
+	struct sctphdr *sh = sctp_hdr(skb);
 	sctp_chunkhdr_t *ch;
 	union sctp_params params;
 	sctp_init_chunk_t *init;

net/sctp/ipv6.c

@@ -390,7 +390,7 @@ static void sctp_v6_from_skb(union sctp_addr *addr,struct sk_buff *skb,
 	addr->v6.sin6_flowinfo = 0; /* FIXME */
 	addr->v6.sin6_scope_id = ((struct inet6_skb_parm *)skb->cb)->iif;
 
-	sh = (struct sctphdr *) skb->h.raw;
+	sh = sctp_hdr(skb);
 	if (is_saddr) {
 		*port  = sh->source;
 		from = &ipv6_hdr(skb)->saddr;
@@ -765,7 +765,7 @@ static void sctp_inet6_skb_msgname(struct sk_buff *skb, char *msgname,
 	if (msgname) {
 		sctp_inet6_msgname(msgname, addr_len);
 		sin6 = (struct sockaddr_in6 *)msgname;
-		sh = (struct sctphdr *)skb->h.raw;
+		sh = sctp_hdr(skb);
 		sin6->sin6_port = sh->source;
 
 		/* Map ipv4 address into v4-mapped-on-v6 address. */

net/sctp/protocol.c

@@ -235,7 +235,7 @@ static void sctp_v4_from_skb(union sctp_addr *addr, struct sk_buff *skb,
 	port = &addr->v4.sin_port;
 	addr->v4.sin_family = AF_INET;
 
-	sh = (struct sctphdr *) skb->h.raw;
+	sh = sctp_hdr(skb);
 	if (is_saddr) {
 		*port  = sh->source;
 		from = &ip_hdr(skb)->saddr;
@@ -731,13 +731,11 @@ static void sctp_inet_event_msgname(struct sctp_ulpevent *event, char *msgname,
 /* Initialize and copy out a msgname from an inbound skb. */
 static void sctp_inet_skb_msgname(struct sk_buff *skb, char *msgname, int *len)
 {
-	struct sctphdr *sh;
-	struct sockaddr_in *sin;
-
 	if (msgname) {
+		struct sctphdr *sh = sctp_hdr(skb);
+		struct sockaddr_in *sin = (struct sockaddr_in *)msgname;
+
 		sctp_inet_msgname(msgname, len);
-		sin = (struct sockaddr_in *)msgname;
-		sh = (struct sctphdr *)skb->h.raw;
 		sin->sin_port = sh->source;
 		sin->sin_addr.s_addr = ip_hdr(skb)->saddr;
 	}