Allow wildcards in domain patterns.

Domain patterns in --address, --server and --local have, for many years,
matched complete labels only, so
--server=/google.com/1.2.3.4
will apply to google.com and www.google.com but NOT supergoogle.com

This commit introduces an optional '*' at the LHS of the domain string which
changes this behaviour so as to include substring matches _within_ labels. So,
--server=/*google.com/1.2.3.4
applies to google.com, www.google.com AND supergoogle.com.

man/dnsmasq.8

@@ -460,13 +460,22 @@ repeated domain or ipaddr parts as required.
 More specific domains take precedence over less specific domains, so:
 .B --server=/google.com/1.2.3.4
 .B --server=/www.google.com/2.3.4.5
-will send queries for *.google.com to 1.2.3.4, except *www.google.com,
+will send queries for google.com and gmail.google.com to 1.2.3.4, but www.google.com
-which will go to 2.3.4.5
+will go to 2.3.4.5
+
+Matching of domains is normally done on complete labels, so /google.com/ matches google.com and www.google.com
+but NOT supergoogle.com. This can be overridden with a * at the start of a pattern only: /*google.com/
+will match google.com and www.google.com AND supergoogle.com. The non-wildcard form has priority, so
+if /google.com/ and /*google.com/ are both specified then google.com and www.google.com will match /google.com/
+and /*google.com/ will only match supergoogle.com.
+
+For historical reasons, the pattern /.google.com/ is equivalent to /google.com/ if you wish to match any subdomain
+of google.com but NOT google.com itself, use /*.google.com/
 
 The special server address '#' means, "use the standard servers", so
 .B --server=/google.com/1.2.3.4
 .B --server=/www.google.com/#
-will send queries for *.google.com to 1.2.3.4, except *www.google.com which will
+will send queries for google.com and its subdomains to 1.2.3.4, except www.google.com (and its subdomains) which will
 be forwarded as usual.
 
 Also permitted is a -S

src/dnsmasq.h

@@ -537,7 +537,7 @@ union mysockaddr {
 #define SERV_WARNED_RECURSIVE 64  /* avoid warning spam */
 #define SERV_FROM_DBUS       128  /* 1 if source is DBus */
 #define SERV_MARK            256  /* for mark-and-delete and log code */
-/* #define SERV_COUNTED         512  /* workspace for log code */ 
+#define SERV_WILDCARD        512  /* domain has leading '*' */ 
 #define SERV_USE_RESOLV     1024  /* forward this domain in the normal way */
 #define SERV_FROM_RESOLV    2048  /* 1 for servers from resolv, 0 for command line. */
 #define SERV_FROM_FILE      4096  /* read from --servers-file */
@@ -1103,6 +1103,7 @@ extern struct daemon {
   struct iname *if_names, *if_addrs, *if_except, *dhcp_except, *auth_peers, *tftp_interfaces;
   struct bogus_addr *bogus_addr, *ignore_addr;
   struct server *servers, *local_domains, **serverarray, *no_rebind;
+  int server_has_wildcard;
   int serverarraysz, serverarrayhwm;
   struct ipsets *ipsets;
   u32 allowlist_mask;

src/domain-match.c

@@ -32,10 +32,18 @@ void build_server_array(void)
 #ifdef HAVE_LOOP
     if (!(serv->flags & SERV_LOOP))
 #endif
+      {
 	count++;
+	if (serv->flags & SERV_WILDCARD)
+	  daemon->server_has_wildcard = 1;
+      }
   
   for (serv = daemon->local_domains; serv; serv = serv->next)
+    {
       count++;
+      if (serv->flags & SERV_WILDCARD)
+	daemon->server_has_wildcard = 1;
+    }
   
   daemon->serverarraysz = count;
 
@@ -92,13 +100,13 @@ void build_server_array(void)
    reply of IPv4 or IPV6.
    return 0 if nothing found, 1 otherwise.
 */
-int lookup_domain(char *qdomain, int flags, int *lowout, int *highout)
+int lookup_domain(char *domain, int flags, int *lowout, int *highout)
 {
   int rc, crop_query, nodots;
   ssize_t qlen;
   int try, high, low = 0;
   int nlow = 0, nhigh = 0;
-  char *cp;
+  char *cp, *qdomain = domain;
 
   /* may be no configured servers. */
   if (daemon->serverarraysz == 0)
@@ -177,17 +185,37 @@ int lookup_domain(char *qdomain, int flags, int *lowout, int *highout)
 	};
       
       if (rc == 0)
+	{
+	  int found = 1;
+
+	  if (daemon->server_has_wildcard)
+	    {
+	      /* if we have example.com and *example.com we need to check against *example.com, 
+		 but the binary search may have found either. Use the fact that example.com is sorted before *example.com
+		 We favour example.com in the case that both match (ie www.example.com) */
+	      while (try != 0 && order(qdomain, qlen, daemon->serverarray[try-1]) == 0)
+		try--;
+	      
+	      if (!(qdomain == domain || *qdomain == 0 || *(qdomain-1) == '.'))
+		{
+		  while (try < daemon->serverarraysz-1 && order(qdomain, qlen, daemon->serverarray[try+1]) == 0)
+		    try++;
+		  
+		  if (!(daemon->serverarray[try]->flags & SERV_WILDCARD))
+		     found = 0;
+		}
+	    }
+	  
+	  if (found)
 	    {
 	      /* We've matched a setting which says to use servers without a domain.
 		 Continue the search with empty query */
 	      if (daemon->serverarray[try]->flags & SERV_USE_RESOLV)
 		crop_query = qlen;
-	  else
+	      else if (filter_servers(try, flags, &nlow, &nhigh))
-	    {
 		/* We have a match, but it may only be (say) an IPv6 address, and
 		   if the query wasn't for an AAAA record, it's no good, and we need
 		   to continue generalising */
-	      if (filter_servers(try, flags, &nlow, &nhigh))
 		break;
 	    }
 	}
@@ -197,9 +225,11 @@ int lookup_domain(char *qdomain, int flags, int *lowout, int *highout)
 	crop_query = 1;
 
       /* strip chars off the query based on the largest possible remaining match,
-	 then continue to the start of the next label. */
+	 then continue to the start of the next label unless we have a wildcard
+	 domain somewhere, in which case we have to go one at a time. */
       qlen -= crop_query;
       qdomain += crop_query;
+      if (!daemon->server_has_wildcard)
 	while (qlen > 0 &&  (*(qdomain-1) != '.'))
 	  qlen--, qdomain++;
     }
@@ -449,13 +479,22 @@ static int order(char *qdomain, size_t qlen, struct server *serv)
 
 static int order_servers(struct server *s1, struct server *s2)
 {
+  int rc;
+
   /* need full comparison of dotless servers in 
      order_qsort() and filter_servers() */
 
   if (s1->flags & SERV_FOR_NODOTS)
      return (s2->flags & SERV_FOR_NODOTS) ? 0 : 1;
    
-   return order(s1->domain, s1->domain_len, s2);
+  if ((rc = order(s1->domain, s1->domain_len, s2)) != 0)
+    return rc;
+
+  /* For identical domains, sort wildcard ones first */
+  if (s1->flags & SERV_WILDCARD)
+    return (s2->flags & SERV_WILDCARD) ? 0 : 1;
+
+  return (s2->flags & SERV_WILDCARD) ? -1 : 0;
 }
   
 static int order_qsort(const void *a, const void *b)
@@ -540,8 +579,16 @@ int add_update_server(int flags,
   
   if (!domain || strlen(domain) == 0)
     alloc_domain = whine_malloc(1);
-  else if (!(alloc_domain = canonicalise((char *)domain, NULL)))
+  else
+    {
+      if (*domain == '*')
+	{
+	  domain++;
+	  flags |= SERV_WILDCARD;
+	}
+      if (!(alloc_domain = canonicalise((char *)domain, NULL)))
 	return 0;
+    }
   
   /* See if there is a suitable candidate, and unmark
      only do this for forwarding servers, not 

src/network.c

@@ -1588,7 +1588,7 @@ void check_servers(int no_loop_check)
       
       if (strlen(serv->domain) != 0 || (serv->flags & SERV_FOR_NODOTS))
 	{
-	  char *s1, *s2, *s3 = "";
+	  char *s1, *s2, *s3 = "", *s4 = "";
 
 #ifdef HAVE_DNSSEC
 	  if (option_bool(OPT_DNSSEC_VALID) && !(serv->flags & SERV_DO_DNSSEC))
@@ -1599,9 +1599,9 @@ void check_servers(int no_loop_check)
 	  else if (strlen(serv->domain) == 0)
 	    s1 = _("default"), s2 = "";
 	  else
-	    s1 = _("domain"), s2 = serv->domain;
+	    s1 = _("domain"), s2 = serv->domain, s4 = (serv->flags & SERV_WILDCARD) ? "*" : "";
 	  
-	  my_syslog(LOG_INFO, _("using nameserver %s#%d for %s %s %s"), daemon->namebuff, port, s1, s2, s3);
+	  my_syslog(LOG_INFO, _("using nameserver %s#%d for %s %s%s %s"), daemon->namebuff, port, s1, s4, s2, s3);
 	}
 #ifdef HAVE_LOOP
       else if (serv->flags & SERV_LOOP)