netlink: Add field to skip in-kernel notifications

The struct includes a 'skip_notify' flag that indicates if netlink
notifications to user space should be suppressed. As explained in commit
3b1137fe ("net: ipv6: Change notifications for multipath add to
RTA_MULTIPATH"), this is useful to suppress per-nexthop RTM_NEWROUTE
notifications when an IPv6 multipath route is added / deleted. Instead,
one notification is sent for the entire multipath route.

This concept is also useful for in-kernel notifications. Sending one
in-kernel notification for the addition / deletion of an IPv6 multipath
route - instead of one per-nexthop - provides a significant increase in
the insertion / deletion rate to underlying devices.

Add a 'skip_notify_kernel' flag to suppress in-kernel notifications.
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/netlink.h

@@ -381,12 +381,14 @@ struct nla_policy {
  * @nl_net: Network namespace
  * @portid: Netlink PORTID of requesting application
  * @skip_notify: Skip netlink notifications to user space
+ * @skip_notify_kernel: Skip selected in-kernel notifications
  */
 struct nl_info {
 	struct nlmsghdr		*nlh;
 	struct net		*nl_net;
 	u32			portid;
-	bool			skip_notify;
+	u8			skip_notify:1,
+				skip_notify_kernel:1;
 };
 
 /**