1 files changed, 18 insertions, 0 deletions
diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h
index fa5ae9432d38..1ca39629031b 100644
--- a/net/l2tp/l2tp_core.h
+++ b/net/l2tp/l2tp_core.h
@@ -12,6 +12,9 @@
 #ifndef _L2TP_CORE_H_
 #define _L2TP_CORE_H_
 
+#include <net/dst.h>
+#include <net/sock.h>
+
 /* Just some random numbers */
 #define L2TP_TUNNEL_MAGIC	0x42114DDA
 #define L2TP_SESSION_MAGIC	0x0C04EB7D
@@ -268,6 +271,21 @@ static inline int l2tp_get_l2specific_len(struct l2tp_session *session)
 	}
 }
 
+static inline u32 l2tp_tunnel_dst_mtu(const struct l2tp_tunnel *tunnel)
+{
+	struct dst_entry *dst;
+	u32 mtu;
+
+	dst = sk_dst_get(tunnel->sock);
+	if (!dst)
+		return 0;
+
+	mtu = dst_mtu(dst);
+	dst_release(dst);
+
+	return mtu;
+}
+
 #define l2tp_printk(ptr, type, func, fmt, ...)				\
 do {									\
 	if (((ptr)->debug) & (type))					\