2 files changed, 21 insertions, 11 deletions

diff --git a/src/vnet/dns/dns.c b/src/vnet/dns/dns.c
index 54b75aa1708..93b7fb8b9f4 100644
--- a/src/vnet/dns/dns.c
+++ b/src/vnet/dns/dns.c
@@ -72,6 +72,7 @@ dns_enable_disable (dns_main_t * dm, int is_enable)
 {
   vlib_thread_main_t *tm = &vlib_thread_main;
   u32 n_vlib_mains = tm->n_vlib_mains;
+  vlib_main_t *vm = dm->vlib_main;
 
   if (is_enable)
     {
@@ -79,6 +80,23 @@ dns_enable_disable (dns_main_t * dm, int is_enable)
 	  && (vec_len (dm->ip6_name_servers) == 0))
 	return VNET_API_ERROR_NO_NAME_SERVERS;
 
+      if (dm->udp_ports_registered == 0)
+	{
+	  udp_register_dst_port (vm, UDP_DST_PORT_dns_reply,
+				 dns46_reply_node.index, 1 /* is_ip4 */ );
+
+	  udp_register_dst_port (vm, UDP_DST_PORT_dns_reply6,
+				 dns46_reply_node.index, 0 /* is_ip4 */ );
+
+	  udp_register_dst_port (vm, UDP_DST_PORT_dns,
+				 dns4_request_node.index, 1 /* is_ip4 */ );
+
+	  udp_register_dst_port (vm, UDP_DST_PORT_dns6,
+				 dns6_request_node.index, 0 /* is_ip4 */ );
+
+	  dm->udp_ports_registered = 1;
+	}
+
       if (dm->cache_entry_by_name == 0)
 	{
 	  if (n_vlib_mains > 1)
@@ -1597,17 +1615,6 @@ dns_init (vlib_main_t * vm)
   dm->max_ttl_in_seconds = 86400;
   dm->random_seed = 0xDEADDABE;
 
-  udp_register_dst_port (vm, UDP_DST_PORT_dns_reply, dns46_reply_node.index,
-			 1 /* is_ip4 */ );
-
-  udp_register_dst_port (vm, UDP_DST_PORT_dns_reply6, dns46_reply_node.index,
-			 0 /* is_ip4 */ );
-
-  udp_register_dst_port (vm, UDP_DST_PORT_dns, dns4_request_node.index,
-			 1 /* is_ip4 */ );
-
-  udp_register_dst_port (vm, UDP_DST_PORT_dns6, dns6_request_node.index,
-			 0 /* is_ip4 */ );
   return 0;
 }
 
diff --git a/src/vnet/dns/dns.h b/src/vnet/dns/dns.h
index 59a61ed7687..c747e2ecd38 100644
--- a/src/vnet/dns/dns.h
+++ b/src/vnet/dns/dns.h
@@ -101,6 +101,9 @@ typedef struct
   /** enable / disable flag */
   int is_enabled;
 
+  /** udp port registration complete */
+  int udp_ports_registered;
+
   /** upstream name servers, e.g. 8.8.8.8 */
   ip4_address_t *ip4_name_servers;
   ip6_address_t *ip6_name_servers;