[NETLIKN]: Allow removing multicast groups.
Allow kicking listeners out of a multicast group when necessary
(for example if that group is going to be removed.)
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Patrick McHardy <kaber@trash.net>
Acked-by: Jamal Hadi Salim <hadi@cyberus.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index c386eaf..5681ce3 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1027,6 +1027,23 @@
read_unlock(&nl_table_lock);
}
+/* must be called with netlink table grabbed */
+static void netlink_update_socket_mc(struct netlink_sock *nlk,
+ unsigned int group,
+ int is_new)
+{
+ int old, new = !!is_new, subscriptions;
+
+ old = test_bit(group - 1, nlk->groups);
+ subscriptions = nlk->subscriptions - old + new;
+ if (new)
+ __set_bit(group - 1, nlk->groups);
+ else
+ __clear_bit(group - 1, nlk->groups);
+ netlink_update_subscriptions(&nlk->sk, subscriptions);
+ netlink_update_listeners(&nlk->sk);
+}
+
static int netlink_setsockopt(struct socket *sock, int level, int optname,
char __user *optval, int optlen)
{
@@ -1052,9 +1069,6 @@
break;
case NETLINK_ADD_MEMBERSHIP:
case NETLINK_DROP_MEMBERSHIP: {
- unsigned int subscriptions;
- int old, new = optname == NETLINK_ADD_MEMBERSHIP ? 1 : 0;
-
if (!netlink_capable(sock, NL_NONROOT_RECV))
return -EPERM;
err = netlink_realloc_groups(sk);
@@ -1063,14 +1077,8 @@
if (!val || val - 1 >= nlk->ngroups)
return -EINVAL;
netlink_table_grab();
- old = test_bit(val - 1, nlk->groups);
- subscriptions = nlk->subscriptions - old + new;
- if (new)
- __set_bit(val - 1, nlk->groups);
- else
- __clear_bit(val - 1, nlk->groups);
- netlink_update_subscriptions(sk, subscriptions);
- netlink_update_listeners(sk);
+ netlink_update_socket_mc(nlk, val,
+ optname == NETLINK_ADD_MEMBERSHIP);
netlink_table_ungrab();
err = 0;
break;
@@ -1351,7 +1359,9 @@
*
* This changes the number of multicast groups that are available
* on a certain netlink family. Note that it is not possible to
- * change the number of groups to below 32.
+ * change the number of groups to below 32. Also note that it does
+ * not implicitly call netlink_clear_multicast_users() when the
+ * number of groups is reduced.
*
* @sk: The kernel netlink socket, as returned by netlink_kernel_create().
* @groups: The new number of groups.
@@ -1386,6 +1396,29 @@
}
EXPORT_SYMBOL(netlink_change_ngroups);
+/**
+ * netlink_clear_multicast_users - kick off multicast listeners
+ *
+ * This function removes all listeners from the given group.
+ * @ksk: The kernel netlink socket, as returned by
+ * netlink_kernel_create().
+ * @group: The multicast group to clear.
+ */
+void netlink_clear_multicast_users(struct sock *ksk, unsigned int group)
+{
+ struct sock *sk;
+ struct hlist_node *node;
+ struct netlink_table *tbl = &nl_table[ksk->sk_protocol];
+
+ netlink_table_grab();
+
+ sk_for_each_bound(sk, node, &tbl->mc_list)
+ netlink_update_socket_mc(nlk_sk(sk), group, 0);
+
+ netlink_table_ungrab();
+}
+EXPORT_SYMBOL(netlink_clear_multicast_users);
+
void netlink_set_nonroot(int protocol, unsigned int flags)
{
if ((unsigned int)protocol < MAX_LINKS)