ipv4: Namespecify the tcp_keepalive_intvl sysctl knob

This is the final part required to namespaceify the tcp
keep alive mechanism.

Signed-off-by: Nikolay Borisov <kernel@kyup.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index 6e26ea2..2b7907a 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -96,6 +96,7 @@
 
 	int sysctl_tcp_keepalive_time;
 	int sysctl_tcp_keepalive_probes;
+	int sysctl_tcp_keepalive_intvl;
 
 	struct ping_group_range ping_group_range;