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>
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 97b2553..8793c2b 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -526,6 +526,8 @@
 	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;