[NETFILTER]: ctnetlink: check for listeners before sending expectation events

This patch uses nfnetlink_has_listeners to check for listeners in
userspace.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/ip_conntrack_netlink.c b/net/ipv4/netfilter/ip_conntrack_netlink.c
index 38708e6cfae7..ef84f43f0734 100644
--- a/net/ipv4/netfilter/ip_conntrack_netlink.c
+++ b/net/ipv4/netfilter/ip_conntrack_netlink.c
@@ -1257,6 +1257,9 @@ static int ctnetlink_expect_event(struct notifier_block *this,
         } else
                 return NOTIFY_DONE;
 
+        if (!nfnetlink_has_listeners(NFNLGRP_CONNTRACK_EXP_NEW))
+                return NOTIFY_DONE;
+
         skb = alloc_skb(NLMSG_GOODSIZE, GFP_ATOMIC);
         if (!skb)
                 return NOTIFY_DONE;