[NETFILTER]: ctnetlink: avoid unneccessary event message generation

Avoid unneccessary event message generation by checking for netlink
listeners before building a message.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/netfilter/nfnetlink.h b/include/linux/netfilter/nfnetlink.h
index 934a247..9f5b12c 100644 (file)
--- a/include/linux/netfilter/nfnetlink.h
+++ b/include/linux/netfilter/nfnetlink.h
@@ -164,6 +164,7 @@ extern void nfattr_parse(struct nfattr *tb[], int maxattr,
        __res;                                                          \
 })
 
+extern int nfnetlink_has_listeners(unsigned int group);
 extern int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, 
                          int echo);
 extern int nfnetlink_unicast(struct sk_buff *skb, u_int32_t pid, int flags);

diff --git a/net/ipv4/netfilter/ip_conntrack_netlink.c b/net/ipv4/netfilter/ip_conntrack_netlink.c
index e0b5926..5ce2e3f 100644 (file)
--- a/net/ipv4/netfilter/ip_conntrack_netlink.c
+++ b/net/ipv4/netfilter/ip_conntrack_netlink.c
@@ -327,9 +327,10 @@ static int ctnetlink_conntrack_event(struct notifier_block *this,
                group = NFNLGRP_CONNTRACK_UPDATE;
        } else 
                return NOTIFY_DONE;
-       
-  /* FIXME: Check if there are any listeners before, don't hurt performance */
-       
+
+       if (!nfnetlink_has_listeners(group))
+               return NOTIFY_DONE;
+
        skb = alloc_skb(NLMSG_GOODSIZE, GFP_ATOMIC);
        if (!skb)
                return NOTIFY_DONE;

diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index aef3cb4..5eadf00 100644 (file)
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -338,9 +338,10 @@ static int ctnetlink_conntrack_event(struct notifier_block *this,
                group = NFNLGRP_CONNTRACK_UPDATE;
        } else
                return NOTIFY_DONE;
-       
-  /* FIXME: Check if there are any listeners before, don't hurt performance */
-       
+
+       if (!nfnetlink_has_listeners(group))
+               return NOTIFY_DONE;
+
        skb = alloc_skb(NLMSG_GOODSIZE, GFP_ATOMIC);
        if (!skb)
                return NOTIFY_DONE;

diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
index f6063e8..b88e82a 100644 (file)
--- a/net/netfilter/nfnetlink.c
+++ b/net/netfilter/nfnetlink.c
@@ -191,6 +191,12 @@ nfnetlink_check_attributes(struct nfnetlink_subsystem *subsys,
         return 0;
 }
 
+int nfnetlink_has_listeners(unsigned int group)
+{
+       return netlink_has_listeners(nfnl, group);
+}
+EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
+
 int nfnetlink_send(struct sk_buff *skb, u32 pid, unsigned group, int echo)
 {
        gfp_t allocation = in_interrupt() ? GFP_ATOMIC : GFP_KERNEL;