Don't BIND DHCP socket if more interfaces may come along later.

CHANGELOG

@@ -50,6 +50,12 @@ version 2.67
 	    Log when the maximum number of concurrent DNS queries is
 	    reached. Thanks to Marcelo Salhab Brogliato for the patch.
 
+	    If wildcards are used in --interface, don't assume that 
+	    there will only ever be one available interface for DHCP
+	    just because there is one at start-up. More may appear, so
+	    we can't use SO_BINDTODEVICE. Thanks to Natrio for the bug
+	    report. 
+
 		
 version 2.66
             Add the ability to act as an authoritative DNS

src/dhcp-common.c

@@ -347,21 +347,27 @@ void bindtodevice(int fd)
      to that device. This is for the use case of  (eg) OpenStack, which runs a new
      dnsmasq instance for each VLAN interface it creates. Without the BINDTODEVICE, 
      individual processes don't always see the packets they should.
-     SO_BINDTODEVICE is only available Linux. */
+     SO_BINDTODEVICE is only available Linux. 
+
+     Note that if wildcards are used in --interface, or a configured interface doesn't
+     yet exist, then more interfaces may arrive later, so we can't safely assert there
+     is only one interface and proceed.
+*/
   
   struct irec *iface, *found;
-  
+  struct iname *if_tmp;
+
+  for (if_tmp = daemon->if_names; if_tmp; if_tmp = if_tmp->next)
+    if (if_tmp->name && (!if_tmp->used || strchr(if_tmp->name, '*')))
+      return;
+
   for (found = NULL, iface = daemon->interfaces; iface; iface = iface->next)
     if (iface->dhcp_ok)
       {
 	if (!found)
 	  found = iface;
 	else if (strcmp(found->name, iface->name) != 0) 
-	  {
-	    /* more than one. */
-	    found = NULL;
-	    break;
-	  }
+	  return; /* more than one. */
       }
   
   if (found)