[SKBUFF] introduce tr_hdr(skb)

The token ring code in the kernel is bitrotting (no surprise :) ),
it uses skb->data all around... I have an assortment of token ring
cards but no MAU, can anybody send me one, please? I promise to
make ssh work over LLC over Token Ring networks! Duh... :o)
Signed-off-by: Arnaldo Carvalho de Melo <acme@conectiva.com.br>
Signed-off-by: David S. Miller <davem@redhat.com>

include/linux/if_tr.h

@@ -48,6 +48,15 @@ struct trh_hdr {
 	__u16 rseg[8];			/* routing registers */
 };
 
+#ifdef __KERNEL__
+#include <linux/skbuff.h>
+
+static inline struct trh_hdr *tr_hdr(const struct sk_buff *skb)
+{
+	return (struct trh_hdr *)skb->mac.raw;
+}
+#endif
+
 /* This is an Token-Ring LLC structure */
 struct trllc {
 	__u8  dsap;			/* destination SAP */

include/net/llc_pdu.h

@@ -255,7 +255,7 @@ static inline void llc_pdu_decode_sa(struct sk_buff *skb, u8 *sa)
 	if (skb->protocol == ntohs(ETH_P_802_2))
 		memcpy(sa, eth_hdr(skb)->h_source, ETH_ALEN);
 	else if (skb->protocol == ntohs(ETH_P_TR_802_2))
-		memcpy(sa, ((struct trh_hdr *)skb->mac.raw)->saddr, ETH_ALEN);
+		memcpy(sa, tr_hdr(skb)->saddr, ETH_ALEN);
 }
 
 /**
@@ -270,7 +270,7 @@ static inline void llc_pdu_decode_da(struct sk_buff *skb, u8 *da)
 	if (skb->protocol == ntohs(ETH_P_802_2))
 		memcpy(da, eth_hdr(skb)->h_dest, ETH_ALEN);
 	else if (skb->protocol == ntohs(ETH_P_TR_802_2))
-		memcpy(da, ((struct trh_hdr *)skb->mac.raw)->daddr, ETH_ALEN);
+		memcpy(da, tr_hdr(skb)->daddr, ETH_ALEN);
 }
 
 /**

net/llc/llc_output.c

@@ -40,7 +40,8 @@ int llc_mac_hdr_init(struct sk_buff *skb, unsigned char *sa, unsigned char *da)
 		struct net_device *dev = skb->dev;
 		struct trh_hdr *trh;
 		
-		trh = (struct trh_hdr *)skb_push(skb, sizeof(*trh));
+		skb->mac.raw = skb_push(skb, sizeof(*trh));
+		trh = tr_hdr(skb);
 		trh->ac = AC;
 		trh->fc = LLC_FRAME;
 		if (sa)
@@ -51,7 +52,6 @@ int llc_mac_hdr_init(struct sk_buff *skb, unsigned char *sa, unsigned char *da)
 			memcpy(trh->daddr, da, dev->addr_len);
 			tr_source_route(skb, trh, dev);
 		}
-		skb->mac.raw = skb->data;
 		break;
 	}
 #endif