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authorPatrick McHardy <kaber@trash.net>2006-03-21 05:52:01 +0300
committerDavid S. Miller <davem@davemloft.net>2006-03-21 05:52:01 +0300
commit4277a083ecd2c8771058641132bcecea04ca6608 (patch)
treec35d659c63fa4d64e2569e5eebd76e1b3fba9a15 /net/netlink
parenta24276924875802853b5bdc12c56d29f1c1bbc79 (diff)
downloadlinux-4277a083ecd2c8771058641132bcecea04ca6608.tar.xz
[NETLINK]: Add netlink_has_listeners for avoiding unneccessary event message generation
Keep a bitmask of multicast groups with subscribed listeners to let netlink users check for listeners before generating multicast messages. Queries don't perform any locking, which may result in false positives, it is guaranteed however that any new subscriptions are visible before bind() or setsockopt() return. Signed-off-by: Patrick McHardy <kaber@trash.net> ACKed-by: Jamal Hadi Salim<hadi@cyberus.ca> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/netlink')
-rw-r--r--net/netlink/af_netlink.c52
1 files changed, 48 insertions, 4 deletions
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 59dc7d140600..d00a9034cb5f 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;
}