genetlink: make multicast groups const, prevent abuse

Register generic netlink multicast groups as an array with
the family and give them contiguous group IDs. Then instead
of passing the global group ID to the various functions that
send messages, pass the ID relative to the family - for most
families that's just 0 because the only have one group.

This avoids the list_head and ID in each group, adding a new
field for the mcast group ID offset to the family.

At the same time, this allows us to prevent abusing groups
again like the quota and dropmon code did, since we can now
check that a family only uses a group it owns.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 4 deletions

diff --git a/net/openvswitch/dp_notify.c b/net/openvswitch/dp_notify.c
index f4b66c84ea0b..2c631fe76be1 100644
--- a/net/openvswitch/dp_notify.c
+++ b/net/openvswitch/dp_notify.c
@@ -35,15 +35,13 @@ static void dp_detach_port_notify(struct vport *vport)
 	ovs_dp_detach_port(vport);
 	if (IS_ERR(notify)) {
 		genl_set_err(&dp_vport_genl_family, ovs_dp_get_net(dp), 0,
-			     ovs_dp_vport_multicast_group.id,
-			     PTR_ERR(notify));
+			     0, PTR_ERR(notify));
 		return;
 	}
 
 	genlmsg_multicast_netns(&dp_vport_genl_family,
 				ovs_dp_get_net(dp), notify, 0,
-				ovs_dp_vport_multicast_group.id,
-				GFP_KERNEL);
+				0, GFP_KERNEL);
 }
 
 void ovs_dp_notify_wq(struct work_struct *work)