ipv6: helper function to get tclass

Implement helper inline function to get traffic class from IPv6 header.
Signed-off-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/ipv6.h

@@ -233,6 +233,11 @@ static inline struct ipv6hdr *ipipv6_hdr(const struct sk_buff *skb)
 	return (struct ipv6hdr *)skb_transport_header(skb);
 }
 
+static inline __u8 ipv6_tclass(const struct ipv6hdr *iph)
+{
+	return (ntohl(*(__be32 *)iph) >> 20) & 0xff;
+}
+
 /* 
    This structure contains results of exthdrs parsing
    as offsets from skb->nh.

net/ipv6/datagram.c

@@ -485,7 +485,7 @@ int datagram_recv_ctl(struct sock *sk, struct msghdr *msg, struct sk_buff *skb)
 	}
 
 	if (np->rxopt.bits.rxtclass) {
-		int tclass = (ntohl(*(__be32 *)ipv6_hdr(skb)) >> 20) & 0xff;
+		int tclass = ipv6_tclass(ipv6_hdr(skb));
 		put_cmsg(msg, SOL_IPV6, IPV6_TCLASS, sizeof(tclass), &tclass);
 	}