1 files changed, 48 insertions, 4 deletions

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 59dc7d1..d00a903 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -106,6 +106,7 @@ struct nl_pid_hash {
 struct netlink_table {
 	struct nl_pid_hash hash;
 	struct hlist_head mc_list;
+	unsigned long *listeners;
 	unsigned int nl_nonroot;
 	unsigned int groups;
 	struct module *module;
@@ -296,6 +297,24 @@ static inline int nl_pid_hash_dilute(struct nl_pid_hash *hash, int len)
 
 static const struct proto_ops netlink_ops;
 
+static void
+netlink_update_listeners(struct sock *sk)
+{
+	struct netlink_table *tbl = &nl_table[sk->sk_protocol];
+	struct hlist_node *node;
+	unsigned long mask;
+	unsigned int i;
+
+	for (i = 0; i < NLGRPSZ(tbl->groups)/sizeof(unsigned long); i++) {
+		mask = 0;
+		sk_for_each_bound(sk, node, &tbl->mc_list)
+			mask |= nlk_sk(sk)->groups[i];
+		tbl->listeners[i] = mask;
+	}
+	/* this function is only called with the netlink table "grabbed", which
+	 * makes sure updates are visible before bind or setsockopt return. */
+}
+
 static int netlink_insert(struct sock *sk, u32 pid)
 {
 	struct nl_pid_hash *hash = &nl_table[sk->sk_protocol].hash;
@@ -456,12 +475,14 @@ static int netlink_release(struct socket *sock)
 	if (nlk->module)
 		module_put(nlk->module);
 
+	netlink_table_grab();
 	if (nlk->flags & NETLINK_KERNEL_SOCKET) {
-		netlink_table_grab();
+		kfree(nl_table[sk->sk_protocol].listeners);
 		nl_table[sk->sk_protocol].module = NULL;
 		nl_table[sk->sk_protocol].registered = 0;
-		netlink_table_ungrab();
-	}
+	} else if (nlk->subscriptions)
+		netlink_update_listeners(sk);
+	netlink_table_ungrab();
 
 	kfree(nlk->groups);
 	nlk->groups = NULL;
@@ -589,6 +610,7 @@ static int netlink_bind(struct socket *sock, struct sockaddr *addr, int addr_len
 	                                 hweight32(nladdr->nl_groups) -
 	                                 hweight32(nlk->groups[0]));
 	nlk->groups[0] = (nlk->groups[0] & ~0xffffffffUL) | nladdr->nl_groups; 
+	netlink_update_listeners(sk);
 	netlink_table_ungrab();
 
 	return 0;
@@ -807,6 +829,17 @@ retry:
 	return netlink_sendskb(sk, skb, ssk->sk_protocol);
 }
 
+int netlink_has_listeners(struct sock *sk, unsigned int group)
+{
+	int res = 0;
+
+	BUG_ON(!(nlk_sk(sk)->flags & NETLINK_KERNEL_SOCKET));
+	if (group - 1 < nl_table[sk->sk_protocol].groups)
+		res = test_bit(group - 1, nl_table[sk->sk_protocol].listeners);
+	return res;
+}
+EXPORT_SYMBOL_GPL(netlink_has_listeners);
+
 static __inline__ int netlink_broadcast_deliver(struct sock *sk, struct sk_buff *skb)
 {
 	struct netlink_sock *nlk = nlk_sk(sk);
@@ -1011,6 +1044,7 @@ static int netlink_setsockopt(struct socket *sock, int level, int optname,
 		else
 			__clear_bit(val - 1, nlk->groups);
 		netlink_update_subscriptions(sk, subscriptions);
+		netlink_update_listeners(sk);
 		netlink_table_ungrab();
 		err = 0;
 		break;
@@ -1237,6 +1271,7 @@ netlink_kernel_create(int unit, unsigned int groups,
 	struct socket *sock;
 	struct sock *sk;
 	struct netlink_sock *nlk;
+	unsigned long *listeners = NULL;
 
 	if (!nl_table)
 		return NULL;
@@ -1250,6 +1285,13 @@ netlink_kernel_create(int unit, unsigned int groups,
 	if (__netlink_create(sock, unit) < 0)
 		goto out_sock_release;
 
+	if (groups < 32)
+		groups = 32;
+
+	listeners = kzalloc(NLGRPSZ(groups), GFP_KERNEL);
+	if (!listeners)
+		goto out_sock_release;
+
 	sk = sock->sk;
 	sk->sk_data_ready = netlink_data_ready;
 	if (input)
@@ -1262,7 +1304,8 @@ netlink_kernel_create(int unit, unsigned int groups,
 	nlk->flags |= NETLINK_KERNEL_SOCKET;
 
 	netlink_table_grab();
-	nl_table[unit].groups = groups < 32 ? 32 : groups;
+	nl_table[unit].groups = groups;
+	nl_table[unit].listeners = listeners;
 	nl_table[unit].module = module;
 	nl_table[unit].registered = 1;
 	netlink_table_ungrab();
@@ -1270,6 +1313,7 @@ netlink_kernel_create(int unit, unsigned int groups,
 	return sk;
 
 out_sock_release:
+	kfree(listeners);
 	sock_release(sock);
 	return NULL;
 }