Support limited wildcards in the input tags for --tag-if.

CHANGELOG

@@ -163,6 +163,9 @@ version 2.85
 	Tweak TFTP code to check sender of all received packets, as
 	specified in RFC 1350 para 4.
 
+	Support some wildcard matching of input tags to --tag-if.
+	Thanks to Geoff Back for the idea and the patch.
+
 	
 version 2.84
 	Fix a problem, introduced in 2.83, which could see DNS replies

man/dnsmasq.8

@@ -1435,6 +1435,12 @@ Any number of set: and tag: forms may appear, in any order.
 tag set by another
 .B --tag-if,
 the line which sets the tag must precede the one which tests it.
+
+As an extension, the tag:<tag> clauses support limited wildcard matching,
+similar to the matching in the \fB--interface\fP directive.  This allows, for
+example, using \fB--tag-if=set:ppp,tag:ppp*\fP to set the tag 'ppp' for all requests
+received on any matching interface (ppp0, ppp1, etc).  This can be used in conjunction
+with the tag:!<tag> format meaning that no tag matching the wildcard may be set.
 .TP
 .B \-J, --dhcp-ignore=tag:<tag>[,tag:<tag>]
 When all the given tags appear in the tag set ignore the host and do

src/dhcp-common.c

@@ -79,13 +79,46 @@ ssize_t recv_dhcp_packet(int fd, struct msghdr *msg)
   return (msg->msg_flags & MSG_TRUNC) ? -1 : new_sz;
 }
 
+/* like match_netid() except that the check can have a trailing * for wildcard */
+/* started as a direct copy of match_netid() */
+int match_netid_wild(struct dhcp_netid *check, struct dhcp_netid *pool)
+{
+  struct dhcp_netid *tmp1;
+  
+  for (; check; check = check->next)
+    {
+      const int check_len = strlen(check->net);
+      const int is_wc = (check->net[check_len - 1] == '*');
+      
+      /* '#' for not is for backwards compat. */
+      if (check->net[0] != '!' && check->net[0] != '#')
+	{
+	  for (tmp1 = pool; tmp1; tmp1 = tmp1->next)
+	    if (is_wc ? (strncmp(check->net, tmp1->net, check_len-1) == 0) :
+		(strcmp(check->net, tmp1->net) == 0))
+	      break;
+	  if (!tmp1)
+	    return 0;
+	}
+      else
+	for (tmp1 = pool; tmp1; tmp1 = tmp1->next)
+	  if (is_wc ? (strncmp((check->net)+1, tmp1->net, check_len-2) == 0) :
+	      (strcmp((check->net)+1, tmp1->net) == 0))
+	    return 0;
+    }
+  return 1;
+}
+
 struct dhcp_netid *run_tag_if(struct dhcp_netid *tags)
 {
   struct tag_if *exprs;
   struct dhcp_netid_list *list;
 
+  /* this now uses match_netid_wild() above so that tag_if can
+   * be used to set a 'group of interfaces' tag.
+   */
   for (exprs = daemon->tag_if; exprs; exprs = exprs->next)
-    if (match_netid(exprs->tag, tags, 1))
+    if (match_netid_wild(exprs->tag, tags))
       for (list = exprs->set; list; list = list->next)
 	{
 	  list->list->next = tags;