sd-netlink: refcount multicast groups

Track the number of matches installed for a given multicast group, and leave the
group once no matches depend on it.

In order to handle passed-in sockets that are already members of multicast groups
we initialize the refcount based on the membership once we take over the socket.
This way we will leave the socket in the state we found it once we finish with
it.

On kernels that do not fully support reading out the multicast group membership
we fall back to never leaving any groups (as before).

1 files changed, 5 insertions, 1 deletions

diff --git a/src/libsystemd/sd-netlink/netlink-internal.h b/src/libsystemd/sd-netlink/netlink-internal.h
index 4026e2c341..b9cb80668d 100644
--- a/src/libsystemd/sd-netlink/netlink-internal.h
+++ b/src/libsystemd/sd-netlink/netlink-internal.h
@@ -64,6 +64,9 @@ struct sd_netlink {
                 struct sockaddr_nl nl;
         } sockaddr;
 
+        Hashmap *broadcast_group_refs;
+        bool broadcast_group_dont_leave:1; /* until we can rely on 4.2 */
+
         sd_netlink_message **rqueue;
         unsigned rqueue_size;
         size_t rqueue_allocated;
@@ -124,7 +127,8 @@ int message_new_empty(sd_netlink *rtnl, sd_netlink_message **ret);
 
 int socket_open(int family);
 int socket_bind(sd_netlink *nl);
-int socket_join_broadcast_group(sd_netlink *nl, unsigned group);
+int socket_broadcast_group_ref(sd_netlink *nl, unsigned group);
+int socket_broadcast_group_unref(sd_netlink *nl, unsigned group);
 int socket_write_message(sd_netlink *nl, sd_netlink_message *m);
 int socket_read_message(sd_netlink *nl);