Add --synth-domain

CHANGELOG

@@ -15,6 +15,9 @@ version 2.67
 	    Fix --dhcp-match, --dhcp-vendorclass and --dhcp-userclass
 	    to work with BOOTP and well as DHCP. Thanks to Peter
 	    Korsgaard for spotting the problem. 
+
+	    Add --synth-domain. Thanks to Vishvananda Ishaya for
+	    suggesting this.
 	
 
 version 2.66

Makefile

@@ -65,7 +65,7 @@ version =     -DVERSION='\"`$(top)/bld/get-version $(top)`\"'
 objs = cache.o rfc1035.o util.o option.o forward.o network.o \
        dnsmasq.o dhcp.o lease.o rfc2131.o netlink.o dbus.o bpf.o \
        helper.o tftp.o log.o conntrack.o dhcp6.o rfc3315.o \
-       dhcp-common.o outpacket.o radv.o slaac.o auth.o ipset.o
+       dhcp-common.o outpacket.o radv.o slaac.o auth.o ipset.o domain.o
 
 hdrs = dnsmasq.h config.h dhcp-protocol.h dhcp6-protocol.h \
        dns-protocol.h radv-protocol.h

bld/Android.mk

@@ -8,7 +8,7 @@ LOCAL_SRC_FILES :=  bpf.c cache.c dbus.c dhcp.c dnsmasq.c \
                     netlink.c network.c option.c rfc1035.c \
 		    rfc2131.c tftp.c util.c conntrack.c \
 		    dhcp6.c rfc3315.c dhcp-common.c outpacket.c \
-		    radv.c slaac.c auth.c ipset.c
+		    radv.c slaac.c auth.c ipset.c domain.c
 
 LOCAL_MODULE := dnsmasq
 

man/dnsmasq.8

@@ -519,6 +519,21 @@ the name. More than one name may be associated with an interface
 address by repeating the flag; in that case the first instance is used
 for the reverse address-to-name mapping.
 .TP
+.B --synth-domain=<domain>,<address range>
+Create artificial A/AAAA and PTR records for an address range. The
+records use the address, with periods (or colons for IPv6) replaced
+with dashes.
+
+An example should make this clearer.
+.B --synth-domain=thekelleys.org.uk,192.168.0.0/24 
+will result in a query for 192-168-0-56.thekelleys.org.uk returning
+192.168.0.56 and a reverse query vice versa. The same applies to IPv6, but IPv6 addresses may start with '::'
+but DNS labels may not start with '-' so in this case a zero is added
+in front of the label. ::1 becomes 0--1.
+
+The address range can be of the form
+<ip address>,<ip address> or <ip address>/<netmask>
+.TP
 .B --add-mac
 Add the MAC address of the requestor to DNS queries which are
 forwarded upstream. This may be used to DNS filtering by the upstream

src/cache.c

@@ -971,38 +971,6 @@ void cache_reload(void)
       total_size = read_hostsfile(ah->fname, ah->index, total_size, (struct crec **)daemon->packet, revhashsz);
 } 
 
-char *get_domain(struct in_addr addr)
-{
-  struct cond_domain *c;
-
-  for (c = daemon->cond_domain; c; c = c->next)
-    if (!c->is6 &&
-	ntohl(addr.s_addr) >= ntohl(c->start.s_addr) &&
-        ntohl(addr.s_addr) <= ntohl(c->end.s_addr))
-      return c->domain;
-
-  return daemon->domain_suffix;
-}
-
-
-#ifdef HAVE_IPV6
-char *get_domain6(struct in6_addr *addr)
-{
-  struct cond_domain *c;
-
-  u64 addrpart = addr6part(addr);
-  
-  for (c = daemon->cond_domain; c; c = c->next)
-    if (c->is6 &&
-	is_same_net6(addr, &c->start6, 64) &&
-	addrpart >= addr6part(&c->start6) &&
-        addrpart <= addr6part(&c->end6))
-      return c->domain;
-  
-  return daemon->domain_suffix;
-}
-#endif
-
 #ifdef HAVE_DHCP
 struct in_addr a_record_from_hosts(char *name, time_t now)
 {

src/dnsmasq.h

@@ -789,7 +789,7 @@ extern struct daemon {
   struct name_list *secondary_forward_server;
   int group_set, osport;
   char *domain_suffix;
-  struct cond_domain *cond_domain;
+  struct cond_domain *cond_domain, *synth_domains;
   char *runfile; 
   char *lease_change_command;
   struct iname *if_names, *if_addrs, *if_except, *dhcp_except, *auth_peers;
@@ -907,15 +907,19 @@ void cache_unhash_dhcp(void);
 void dump_cache(time_t now);
 char *cache_get_name(struct crec *crecp);
 struct crec *cache_enumerate(int init);
-char *get_domain(struct in_addr addr);
-#ifdef HAVE_IPV6
-char *get_domain6(struct in6_addr *addr);
-#endif
 #ifdef HAVE_DNSSEC
 struct keydata *keydata_alloc(char *data, size_t len);
 void keydata_free(struct keydata *blocks);
 #endif
 
+/* domain.c */
+char *get_domain(struct in_addr addr);
+#ifdef HAVE_IPV6
+char *get_domain6(struct in6_addr *addr);
+#endif
+int is_name_synthetic(int flags, char *name, struct all_addr *addr);
+int is_rev_synth(int flag, struct all_addr *addr, char *name);
+
 /* rfc1035.c */
 unsigned int extract_request(struct dns_header *header, size_t qlen, 
 			       char *name, unsigned short *typep);

src/domain.c

@@ -0,0 +1,200 @@
+/* dnsmasq is Copyright (c) 2000-2013 Simon Kelley
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 dated June, 1991, or
+   (at your option) version 3 dated 29 June, 2007.
+ 
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+     
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "dnsmasq.h"
+
+
+static struct cond_domain *search_domain(struct in_addr addr, struct cond_domain *c);
+#ifdef HAVE_IPV6
+static struct cond_domain *search_domain6(struct in6_addr *addr, struct cond_domain *c);
+#endif
+
+
+int is_name_synthetic(int flags, char *name, struct all_addr *addr)
+{
+  char *p;
+  struct cond_domain *c = NULL;
+  int prot = AF_INET;
+
+#ifdef HAVE_IPV6
+  if (flags & F_IPV6)
+    prot = AF_INET6;
+#endif
+
+  /* NB, must not alter name if we return zero */
+  for (p = name; *p; p++)
+    {
+      char c = *p;
+      
+      if ((c >='0' && c <= '9') || c == '-')
+	continue;
+      
+#ifdef HAVE_IPV6
+      if (prot == AF_INET6 && ((c >='A' && c <= 'F') || (c >='a' && c <= 'f'))) 
+	continue;
+#endif
+      
+      break;
+    }
+  
+  if (*p != '.')
+    return 0;
+  
+  *p = 0;	
+
+  for (p = name; *p; p++)
+    if (*p == '-')
+      {
+	if (prot == AF_INET)
+	  *p = '.';
+#ifdef HAVE_IPV6
+	else
+	  *p = ':';
+#endif
+      }
+ 
+  if (inet_pton(prot, name, addr))
+    for (c = daemon->synth_domains; c; c = c->next)
+      if (hostname_isequal(c->domain, p+1))
+	{
+	  if (prot == AF_INET)
+	    {
+	      if (!c->is6 &&
+		  ntohl(addr->addr.addr4.s_addr) >= ntohl(c->start.s_addr) &&
+		  ntohl(addr->addr.addr4.s_addr) <= ntohl(c->end.s_addr))
+		break;
+	    }
+#ifdef HAVE_IPV6
+	  else
+	    {
+	      u64 addrpart = addr6part(&addr->addr.addr6);
+	      
+	      if (c->is6 &&
+		  is_same_net6(&addr->addr.addr6, &c->start6, 64) &&
+		  addrpart >= addr6part(&c->start6) &&
+		  addrpart <= addr6part(&c->end6))
+		break;
+	    }
+#endif
+	}
+  
+  /* restore name */
+  for (p = name; *p; p++)
+    if (*p == '.' || *p == ':')
+      *p = '-';
+  
+  *p = '.';
+  
+  return (c != NULL);
+  
+}
+
+
+int is_rev_synth(int flag, struct all_addr *addr, char *name)
+{
+   struct cond_domain *c;
+
+   if (flag & F_IPV4 && (c = search_domain(addr->addr.addr4, daemon->synth_domains))) 
+     {
+       char *p;
+       
+       inet_ntop(AF_INET, &addr->addr.addr4, name, ADDRSTRLEN);
+       for (p = name; *p; p++)
+	 if (*p == '.')
+	   *p = '-';
+
+       strncat(name, ".", MAXDNAME);
+       strncat(name, c->domain, MAXDNAME);
+
+       return 1;
+     }
+
+#ifdef HAVE_IPV6
+   if (flag & F_IPV6 && (c = search_domain6(&addr->addr.addr6, daemon->synth_domains))) 
+     {
+       char *p;
+       
+       inet_ntop(AF_INET6, &addr->addr.addr6, name, ADDRSTRLEN);
+
+       /* IPv6 presentation address can start with ":", but valid domain names
+	  cannot start with "-" so prepend a zero in that case. */
+       if (*name == ':')
+	 {
+	   *name = '0';
+	   inet_ntop(AF_INET6, &addr->addr.addr6, name+1, ADDRSTRLEN);
+	 }
+
+       for (p = name; *p; p++)
+	 if (*p == ':')
+	   *p = '-';
+
+       strncat(name, ".", MAXDNAME);
+       strncat(name, c->domain, MAXDNAME);
+       
+       return 1;
+     }
+#endif
+   
+   return 0;
+}
+
+
+static struct cond_domain *search_domain(struct in_addr addr, struct cond_domain *c)
+{
+  for (; c; c = c->next)
+    if (!c->is6 &&
+	ntohl(addr.s_addr) >= ntohl(c->start.s_addr) &&
+        ntohl(addr.s_addr) <= ntohl(c->end.s_addr))
+      return c;
+
+  return NULL;
+}
+
+char *get_domain(struct in_addr addr)
+{
+  struct cond_domain *c;
+
+  if ((c = search_domain(addr, daemon->cond_domain)))
+    return c->domain;
+
+  return daemon->domain_suffix;
+} 
+
+#ifdef HAVE_IPV6
+static struct cond_domain *search_domain6(struct in6_addr *addr, struct cond_domain *c)
+{
+  u64 addrpart = addr6part(addr);
+  
+  for (; c; c = c->next)
+    if (c->is6 &&
+	is_same_net6(addr, &c->start6, 64) &&
+	addrpart >= addr6part(&c->start6) &&
+        addrpart <= addr6part(&c->end6))
+      return c;
+  
+  return NULL;
+}
+
+char *get_domain6(struct in6_addr *addr)
+{
+  struct cond_domain *c;
+
+  if ((c = search_domain6(addr, daemon->cond_domain)))
+    return c->domain;
+
+  return daemon->domain_suffix;
+} 
+#endif

src/option.c

@@ -128,8 +128,9 @@ struct myoption {
 #define LOPT_AUTHSFS   317
 #define LOPT_AUTHPEER  318
 #define LOPT_IPSET     319
+#define LOPT_SYNTH     320
 #ifdef OPTION6_PREFIX_CLASS 
-#define LOPT_PREF_CLSS 320
+#define LOPT_PREF_CLSS 321
 #endif
 
 #ifdef HAVE_GETOPT_LONG
@@ -264,6 +265,7 @@ static const struct myoption opts[] =
     { "auth-sec-servers", 1, 0, LOPT_AUTHSFS },
     { "auth-peer", 1, 0, LOPT_AUTHPEER }, 
     { "ipset", 1, 0, LOPT_IPSET },
+    { "synth-domain", 1, 0, LOPT_SYNTH },
 #ifdef OPTION6_PREFIX_CLASS 
     { "dhcp-prefix-class", 1, 0, LOPT_PREF_CLSS },
 #endif
@@ -406,6 +408,7 @@ static struct {
   { LOPT_AUTHSFS, ARG_DUP, "<NS>[,<NS>...]", gettext_noop("Secondary authoritative nameservers for forward domains"), NULL },
   { LOPT_AUTHPEER, ARG_DUP, "<ipaddr>[,<ipaddr>...]", gettext_noop("Peers which are allowed to do zone transfer"), NULL },
   { LOPT_IPSET, ARG_DUP, "/<domain>/<ipset>[,<ipset>...]", gettext_noop("Specify ipsets to which matching domains should be added"), NULL },
+  { LOPT_SYNTH, ARG_DUP, "<domain>,<range>", gettext_noop("Specify a domain and address range for sythesised names"), NULL },
 #ifdef OPTION6_PREFIX_CLASS 
   { LOPT_PREF_CLSS, ARG_DUP, "set:tag,<class>", gettext_noop("Specify DHCPv6 prefix class"), NULL },
 #endif
@@ -1687,7 +1690,8 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
 
       break;
 
-    case 's': /* --domain */
+    case 's':         /* --domain */
+    case LOPT_SYNTH:  /* --synth-domain */
       if (strcmp (arg, "#") == 0)
 	set_option_bool(OPT_RESOLV_DOMAIN);
       else
@@ -1702,7 +1706,7 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
 		{
 		  struct cond_domain *new = opt_malloc(sizeof(struct cond_domain));
 		  char *netpart;
-
+		  
 		  unhide_metas(comma);
 		  if ((netpart = split_chr(comma, '/')))
 		    {
@@ -1723,7 +1727,8 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
 				 local=/<domain>/
 				 local=/xxx.yyy.zzz.in-addr.arpa/ */
 
-			      if (strcmp(arg, "local") != 0 || 
+			      if (strcmp(arg, "local") != 0 ||
+				  option != 's' ||
 				  (msize != 8 && msize != 16 && msize != 24))
 				ret_err(gen_err);
 			      else
@@ -1779,7 +1784,9 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
 				 local=/<domain>/
 				 local=/xxx.yyy.zzz.ip6.arpa/ */
 
-			      if (strcmp(arg, "local") != 0 || ((msize & 4) != 0))
+			      if (strcmp(arg, "local") != 0 || 
+				  option != 's' ||
+				  ((msize & 4) != 0))
 				ret_err(gen_err);
 			      else 
 				{
@@ -1813,7 +1820,7 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
 		      else
 			ret_err(gen_err);
 		    }
-		  else 
+		  else  
 		    {
 		      arg = split(comma);
 		      if (inet_pton(AF_INET, comma, &new->start))
@@ -1839,11 +1846,21 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
 		    }
 
 		  new->domain = d;
-		  new->next = daemon->cond_domain;
-		  daemon->cond_domain = new;		     
+		  if (option  == 's')
+		    {
+		      new->next = daemon->cond_domain;
+		      daemon->cond_domain = new;
+		    }
+		  else
+		    {
+		      new->next = daemon->synth_domains;
+		      daemon->synth_domains = new;
+		    }
 		}
-	      else
+	      else if (option == 's')
 		daemon->domain_suffix = d;
+	      else 
+		ret_err(gen_err);
 	    }
 	}
       break;

src/rfc1035.c

@@ -1517,6 +1517,19 @@ size_t answer_request(struct dns_header *header, char *limit, size_t qlen,
 			  }
 		      }
 		  } while ((crecp = cache_find_by_addr(crecp, &addr, now, is_arpa)));
+	      else if (is_rev_synth(is_arpa, &addr, name))
+		{
+		  ans = 1;
+		  if (!dryrun)
+		    {
+		      log_query(F_CONFIG | F_REVERSE | is_arpa, name, &addr, NULL); 
+		      
+		      if (add_resource_record(header, limit, &trunc, nameoffset, &ansp, 
+					      daemon->local_ttl, NULL,
+					      T_PTR, C_IN, "d", name))
+			      anscount++;
+		    }
+		}
 	      else if (is_arpa == F_IPV4 && 
 		       option_bool(OPT_BOGUSPRIV) && 
 		       private_net(addr.addr.addr4, 1))
@@ -1687,6 +1700,17 @@ size_t answer_request(struct dns_header *header, char *limit, size_t qlen,
 			}
 		    } while ((crecp = cache_find_by_name(crecp, name, now, flag | F_CNAME)));
 		}
+	      else if (is_name_synthetic(flag, name, &addr))
+		{
+		  ans = 1;
+		  if (!dryrun)
+		    {
+		      log_query(F_FORWARD | F_CONFIG | flag, name, &addr, NULL);
+		      if (add_resource_record(header, limit, &trunc, nameoffset, &ansp, 
+					      daemon->local_ttl, NULL, type, C_IN, type == T_A ? "4" : "6", &addr))
+			anscount++;
+		    }
+		}
 	    }
 
 	  if (qtype == T_CNAME || qtype == T_ANY)