Enhance --domain to accept, interface names for the address range.

This allows hosts get a domain which relects the interface they
are attached to in a way which doesn't require hard-coding addresses.

Thanks to Sten Spans for the idea.

CHANGELOG

@@ -49,6 +49,12 @@ version 2.87
 
 	Add --conf-script configuration option.
 
+	Enhance --domain to accept, for instance,
+	--domain=net2.thekelleys.org.uk,eth2 so that hosts get a domain
+	which relects the interface they are attached to in a way which
+	doesn't require hard-coding addresses. Thanks to Sten Spans for
+	the idea.
+
 	
 version 2.86
 	Handle DHCPREBIND requests in the DHCPv6 server code.

man/dnsmasq.8

@@ -1935,7 +1935,7 @@ is the address of the relay and the second, as before, specifies an extra subnet
 addresses may be allocated from.
 
 .TP
-.B \-s, --domain=<domain>[,<address range>[,local]]
+.B \-s, --domain=<domain>[[,<address range>[,local]]|<interface>]
 Specifies DNS domains for the DHCP server. Domains may be be given 
 unconditionally (without the IP range) or for limited IP ranges. This has two effects;
 firstly it causes the DHCP server to return the domain to any hosts
@@ -1969,6 +1969,11 @@ additional flag "local" may be supplied which has the effect of adding
 is identical to
 .B --domain=thekelleys.org.uk,192.168.0.0/24
 .B --local=/thekelleys.org.uk/ --local=/0.168.192.in-addr.arpa/
+
+The address range can also be given as a network interface name, in which case
+all of the subnets currently assigned to the interface are used in matching the
+address. This allows hosts on different physical subnets to be given different
+domains in a way which updates automatically as the interface addresses change.
 .TP
 .B --dhcp-fqdn
 In the default mode, dnsmasq inserts the unqualified names of

src/dnsmasq.h

@@ -975,6 +975,8 @@ struct dhcp_bridge {
 
 struct cond_domain {
   char *domain, *prefix; /* prefix is text-prefix on domain name */
+  char *interface;       /* These two set when domain comes from interface. */
+  struct addrlist *al;
   struct in_addr start, end;
   struct in6_addr start6, end6;
   int is6, indexed, prefixlen;

src/domain.c

@@ -230,9 +230,17 @@ int is_rev_synth(int flag, union all_addr *addr, char *name)
 
 static int match_domain(struct in_addr addr, struct cond_domain *c)
 {
-  if (!c->is6 &&
-      ntohl(addr.s_addr) >= ntohl(c->start.s_addr) &&
-      ntohl(addr.s_addr) <= ntohl(c->end.s_addr))
+  if (c->interface)
+    {
+      struct addrlist *al;
+      for (al = c->al; al; al = al->next)
+	if (!(al->flags & ADDRLIST_IPV6) &&
+	    is_same_net_prefix(addr, al->addr.addr4, al->prefixlen))
+	  return 1;
+    }
+  else if (!c->is6 &&
+	   ntohl(addr.s_addr) >= ntohl(c->start.s_addr) &&
+	   ntohl(addr.s_addr) <= ntohl(c->end.s_addr))
     return 1;
 
   return 0;
@@ -259,12 +267,21 @@ char *get_domain(struct in_addr addr)
 
 static int match_domain6(struct in6_addr *addr, struct cond_domain *c)
 {
-  u64 addrpart = addr6part(addr);
-  
-  if (c->is6)
+    
+  /* subnet from interface address. */
+  if (c->interface)
+    {
+      struct addrlist *al;
+      for (al = c->al; al; al = al->next)
+	if (al->flags & ADDRLIST_IPV6 &&
+	    is_same_net6(addr, &al->addr.addr6, al->prefixlen))
+	  return 1;
+    }
+  else if (c->is6)
     {
       if (c->prefixlen >= 64)
 	{
+	  u64 addrpart = addr6part(addr);
 	  if (is_same_net6(addr, &c->start6, 64) &&
 	      addrpart >= addr6part(&c->start6) &&
 	      addrpart <= addr6part(&c->end6))
@@ -273,7 +290,7 @@ static int match_domain6(struct in6_addr *addr, struct cond_domain *c)
       else if (is_same_net6(addr, &c->start6, c->prefixlen))
 	return 1;
     }
-
+    
   return 0;
 }
 

src/network.c

@@ -231,6 +231,7 @@ static int iface_allowed(struct iface_param *param, int if_index, char *label,
 			 union mysockaddr *addr, struct in_addr netmask, int prefixlen, int iface_flags) 
 {
   struct irec *iface;
+  struct cond_domain *cond;
   int loopback;
   struct ifreq ifr;
   int tftp_ok = !!option_bool(OPT_TFTP);
@@ -453,7 +454,37 @@ static int iface_allowed(struct iface_param *param, int if_index, char *label,
 	      }
 	  }
     }
- 
+
+  /* Update addresses for domain=<domain>,<interface> */
+  for (cond = daemon->cond_domain; cond; cond = cond->next)
+    if (cond->interface && strncmp(label, cond->interface, IF_NAMESIZE) == 0)
+      {
+	struct addrlist *al;
+
+	if (param->spare)
+	  {
+	    al = param->spare;
+	    param->spare = al->next;
+	  }
+	else
+	  al = whine_malloc(sizeof(struct addrlist));
+
+	if (addr->sa.sa_family == AF_INET)
+	  {
+	    al->addr.addr4 = addr->in.sin_addr;
+	    al->flags = 0;
+	  }
+	else
+	  {
+	    al->addr.addr6 =  addr->in6.sin6_addr;
+	    al->flags = ADDRLIST_IPV6;
+	  }
+
+	al->prefixlen = prefixlen;
+	al->next = cond->al;
+	cond->al = al;
+      }
+  
   /* check whether the interface IP has been added already 
      we call this routine multiple times. */
   for (iface = daemon->interfaces; iface; iface = iface->next) 
@@ -691,6 +722,7 @@ int enumerate_interfaces(int reset)
   int errsave, ret = 1;
   struct addrlist *addr, *tmp;
   struct interface_name *intname;
+  struct cond_domain *cond;
   struct irec *iface;
 #ifdef HAVE_AUTH
   struct auth_zone *zone;
@@ -750,6 +782,19 @@ again:
       intname->addr = NULL;
     }
 
+  /* remove addresses stored against cond-domains. */
+  for (cond = daemon->cond_domain; cond; cond = cond->next)
+    {
+      for (addr = cond->al; addr; addr = tmp)
+	{
+	  tmp = addr->next;
+	  addr->next = spare;
+	  spare = addr;
+      }
+      
+      cond->al = NULL;
+    }
+  
   /* Remove list of addresses of local interfaces */
   for (addr = daemon->interface_addrs; addr; addr = tmp)
     {

src/option.c

@@ -2492,9 +2492,15 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
 			  else if (!inet_pton(AF_INET6, arg, &new->end6))
 			    ret_err_free(gen_err, new);
 			}
-		      else 
+		      else if (option == 's')
+			{
+			  /* subnet from interface. */
+			  new->interface = opt_string_alloc(comma);
+			  new->al = NULL;
+			}
+		      else
 			ret_err_free(gen_err, new);
-
+		      
 		      if (option != 's' && prefstr)
 			{
 			  if (!(new->prefix = canonicalise_opt(prefstr)) ||