[NETFILTER]: Enable ip6t_multiport.c to work without skb_linearize()

Signed-off-by: Yasuyuki KOZAKAI <yasuyuki.kozakai@toshiba.co.jp>
Signed-off-by: Patrick McHardy <kaber@trash.net>

net/ipv6/netfilter/ip6t_multiport.c

@@ -56,24 +56,29 @@ match(const struct sk_buff *skb,
       unsigned int protoff,
       int *hotdrop)
 {
-	const struct udphdr *udp = (const struct udphdr *)(skb->data + protoff);
+	u16 _ports[2], *pptr;
 	const struct ip6t_multiport *multiinfo = matchinfo;
 
-	/* Must be big enough to read ports. */
-	if (offset == 0 && skb->len - protoff < sizeof(struct udphdr)) {
+	/* Must not be a fragment. */
+	if (offset)
+		return 0;
+
+	/* Must be big enough to read ports (both UDP and TCP have
+	   them at the start). */
+	pptr = skb_header_pointer(skb, protoff, sizeof(_ports), &_ports[0]);
+	if (pptr == NULL) {
 		/* We've been asked to examine this packet, and we
-		   can't.  Hence, no choice but to drop. */
-			duprintf("ip6t_multiport:"
-				 " Dropping evil offset=0 tinygram.\n");
-			*hotdrop = 1;
-			return 0;
+		 * can't.  Hence, no choice but to drop.
+		 */
+		duprintf("ip6t_multiport:"
+			 " Dropping evil offset=0 tinygram.\n");
+		*hotdrop = 1;
+		return 0;
 	}
 
-	/* Must not be a fragment. */
-	return !offset
-		&& ports_match(multiinfo->ports,
-			       multiinfo->flags, multiinfo->count,
-			       ntohs(udp->source), ntohs(udp->dest));
+	return ports_match(multiinfo->ports,
+			   multiinfo->flags, multiinfo->count,
+			   ntohs(pptr[0]), ntohs(pptr[1]));
 }
 
 /* Called when user tries to insert an entry of this type. */