l2tp: l2tp-decap-local don't accept packets unless configured

Change-Id: I2e48eb772dc44912192d0684b8ee631d8d975e9e
Signed-off-by: Jakub Grajciar <jgrajcia@cisco.com>
diff --git a/src/vnet/l2tp/decap.c b/src/vnet/l2tp/decap.c
index 5fc25f5..787cc11 100644
--- a/src/vnet/l2tp/decap.c
+++ b/src/vnet/l2tp/decap.c
@@ -292,14 +292,6 @@
 };
 /* *INDENT-ON* */
 
-#ifndef CLIB_MARCH_VARIANT
-void
-l2tp_decap_init (void)
-{
-  ip6_register_protocol (IP_PROTOCOL_L2TP, l2t_decap_local_node.index);
-}
-#endif /* CLIB_MARCH_VARIANT */
-
 /*
  * fd.io coding-style-patch-verification: ON
  *
diff --git a/src/vnet/l2tp/l2tp.c b/src/vnet/l2tp/l2tp.c
index 6758db3..42ecfa6 100644
--- a/src/vnet/l2tp/l2tp.c
+++ b/src/vnet/l2tp/l2tp.c
@@ -399,6 +399,12 @@
   if (sw_if_index)
     *sw_if_index = hi->sw_if_index;
 
+  if (!lm->proto_registered)
+    {
+      ip6_register_protocol (IP_PROTOCOL_L2TP, l2t_decap_local_node.index);
+      lm->proto_registered = true;
+    }
+
   return 0;
 }
 
@@ -729,9 +735,10 @@
   pi = ip_get_protocol_info (im, IP_PROTOCOL_L2TP);
   pi->unformat_pg_edit = unformat_pg_l2tp_header;
 
+  lm->proto_registered = false;
+
   /* insure these nodes are included in build */
   l2tp_encap_init (vm);
-  l2tp_decap_init ();
 
   return 0;
 }
diff --git a/src/vnet/l2tp/l2tp.h b/src/vnet/l2tp/l2tp.h
index a91f00c..4987338 100644
--- a/src/vnet/l2tp/l2tp.h
+++ b/src/vnet/l2tp/l2tp.h
@@ -80,6 +80,8 @@
   vlib_main_t *vlib_main;
   vnet_main_t *vnet_main;
 
+  bool proto_registered;
+
 } l2t_main_t;
 
 /* Packet trace structure */
@@ -118,7 +120,6 @@
 uword unformat_pg_l2tp_header (unformat_input_t * input, va_list * args);
 
 void l2tp_encap_init (vlib_main_t * vm);
-void l2tp_decap_init (void);
 int create_l2tpv3_ipv6_tunnel (l2t_main_t * lm,
 			       ip6_address_t * client_address,
 			       ip6_address_t * our_address,