[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>
This commit is contained in:
Patrick McHardy 2006-03-20 18:52:01 -08:00 committed by David S. Miller
parent a242769248
commit 4277a083ec
2 changed files with 49 additions and 4 deletions

View file

@ -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);