This is a simplified version of the netlink_has_listeners patch
to let netlink multicast senders check for listeners before
generating messages. The last version also had a bug that made
the mask only contain the subscribed groups of the socket used
for the last bind operation. This version should be fine for
net-2.6.17, my upcoming netfilter patches will add the first
two users.
[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 <[EMAIL PROTECTED]>
---
commit 8331484fd769c56bfb3e1755683b24968ed6cf21
tree 029676c5859ca3084036f5db1afab31c6d7a6eb8
parent 03ea07c692769c3e43f3bee89c687b43df857189
author Patrick McHardy <[EMAIL PROTECTED]> Thu, 16 Feb 2006 02:37:03 +0100
committer Patrick McHardy <[EMAIL PROTECTED]> Thu, 16 Feb 2006 02:37:03 +0100
include/linux/netlink.h | 1 +
net/netlink/af_netlink.c | 52 ++++++++++++++++++++++++++++++++++++++++++----
2 files changed, 49 insertions(+), 4 deletions(-)
diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index c256ebe..f8f3d1c 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -151,6 +151,7 @@ struct netlink_skb_parms
extern struct sock *netlink_kernel_create(int unit, unsigned int groups, void (*input)(struct sock *sk, int len), struct module *module);
extern void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err);
+extern int netlink_has_listeners(struct sock *sk, unsigned int group);
extern int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 pid, int nonblock);
extern int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 pid,
__u32 group, gfp_t allocation);
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 6b9772d..f767a95 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(str
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
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 *s
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 soc
else
__clear_bit(val - 1, nlk->groups);
netlink_update_subscriptions(sk, subscriptions);
+ netlink_update_listeners(sk);
netlink_table_ungrab();
err = 0;
break;
@@ -1236,6 +1270,7 @@ netlink_kernel_create(int unit, unsigned
struct socket *sock;
struct sock *sk;
struct netlink_sock *nlk;
+ unsigned long *listeners = NULL;
if (!nl_table)
return NULL;
@@ -1249,6 +1284,13 @@ netlink_kernel_create(int unit, unsigned
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)
@@ -1261,7 +1303,8 @@ netlink_kernel_create(int unit, unsigned
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();
@@ -1269,6 +1312,7 @@ netlink_kernel_create(int unit, unsigned
return sk;
out_sock_release:
+ kfree(listeners);
sock_release(sock);
return NULL;
}
