tun: Update classid on packet injection

This patch makes tun update its socket classid every time we
inject a packet into the network stack.  This is so that any
updates made by the admin to the process writing packets to
tun is effected.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/tun.c

@@ -526,6 +526,8 @@ static inline struct sk_buff *tun_alloc_skb(struct tun_struct *tun,
 	struct sk_buff *skb;
 	int err;
 
+	sock_update_classid(sk);
+
 	/* Under a page?  Don't bother with paged skb. */
 	if (prepad + len < PAGE_SIZE || !linear)
 		linear = len;

net/core/sock.c

@@ -1064,6 +1064,7 @@ void sock_update_classid(struct sock *sk)
 	if (classid && classid != sk->sk_classid)
 		sk->sk_classid = classid;
 }
+EXPORT_SYMBOL(sock_update_classid);
 #endif
 
 /**