diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
index 5976bde..b9a6b0a 100644
--- a/include/net/inet_connection_sock.h
+++ b/include/net/inet_connection_sock.h
@@ -126,6 +126,8 @@
 
 		/* Information on the current probe. */
 		int		  probe_size;
+
+		u32		  probe_timestamp;
 	} icsk_mtup;
 	u32			  icsk_ca_priv[16];
 	u32			  icsk_user_timeout;
diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index e051d39..8f3a1a1 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -88,6 +88,7 @@
 	int sysctl_tcp_mtu_probing;
 	int sysctl_tcp_base_mss;
 	int sysctl_tcp_probe_threshold;
+	u32 sysctl_tcp_probe_interval;
 
 	struct ping_group_range ping_group_range;
 
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 1ad82e3..2e11e38 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -67,6 +67,9 @@
 /* The least MTU to use for probing */
 #define TCP_BASE_MSS		1024
 
+/* probing interval, default to 10 minutes as per RFC4821 */
+#define TCP_PROBE_INTERVAL	600
+
 /* Specify interval when tcp mtu probing will stop */
 #define TCP_PROBE_THRESHOLD	8