[NETLINK]: Ignore !NLM_F_REQUEST messages directly in netlink_run_queue()

netlink_rcv_skb() is changed to skip messages which don't have the
NLM_F_REQUEST bit to avoid every netlink family having to perform this
check on their own.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 8488c15..7b45598 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1470,10 +1470,15 @@
 
 	while (skb->len >= nlmsg_total_size(0)) {
 		nlh = nlmsg_hdr(skb);
+		err = 0;
 
 		if (nlh->nlmsg_len < NLMSG_HDRLEN || skb->len < nlh->nlmsg_len)
 			return 0;
 
+		/* Only requests are handled by the kernel */
+		if (!(nlh->nlmsg_flags & NLM_F_REQUEST))
+			goto skip;
+
 		if (cb(skb, nlh, &err) < 0) {
 			/* Not an error, but we have to interrupt processing
 			 * here. Note: that in this case we do not pull
@@ -1481,9 +1486,10 @@
 			 */
 			if (err == 0)
 				return -1;
+		}
+skip:
+		if (nlh->nlmsg_flags & NLM_F_ACK || err)
 			netlink_ack(skb, nlh, err);
-		} else if (nlh->nlmsg_flags & NLM_F_ACK)
-			netlink_ack(skb, nlh, 0);
 
 		netlink_queue_skip(nlh, skb);
 	}