Change iface in the veth_interfaces table to allow NULL values, as

will be the case for a trivial link with no underlying physical iface.

sql/database-create.sql

@@ -1355,7 +1355,7 @@ CREATE TABLE veth_interfaces (
   veth_id int(10) unsigned NOT NULL auto_increment,
   mac varchar(12) NOT NULL default '000000000000',
   IP varchar(15) default NULL,
-  iface varchar(10) NOT NULL default '',
+  iface varchar(10) default NULL,
   vnode_id varchar(32) default NULL,
   PRIMARY KEY  (node_id,veth_id),
   KEY IP (IP)

sql/database-migrate.txt

@@ -613,3 +613,9 @@ last_net_act,last_cpu_act,last_ext_act);
         alter table experiments add multiplex_factor smallint(5)
 	        default NULL after forcelinkdelays;
 		
+1.151: Allow iface in the veth_interfaces table to be null to allow
+       for trivial links between veth devices (on the same node, so no
+       iface mapping).
+
+	alter table veth_interfaces change iface iface varchar(10)
+		 default NULL;