Allow shorter IPv6 prefix lengths in (some) --synth-domain options.

CHANGELOG

@@ -76,6 +76,9 @@ version 2.86
 	Disallowed queries are not forwarded; they are rejected
 	with a REFUSED error code.
 
+	Allow smaller then 64 prefix lengths in synth-domain, with caveats.
+	--synth-domain=1234:4567::/56,example.com is now valid.
+
 	
 version 2.85
         Fix problem with DNS retries in 2.83/2.84.

man/dnsmasq.8

@@ -705,7 +705,8 @@ configured a zero is added in front of the label. ::1 becomes 0--1.
 V4 mapped IPv6 addresses, which have a representation like ::ffff:1.2.3.4 are handled specially, and become like 0--ffff-1-2-3-4
 
 The address range can be of the form
-<ip address>,<ip address> or <ip address>/<netmask> in both forms of the option.
+<start address>,<end address> or <ip address>/<prefix-length> in both forms of the option. For IPv6 the start and end addresses
+must fall in the same /64 network, or prefix-length must be greater than or equal to 64 except that shorter prefix lengths than 64 are allowed only if non-sequential names are in use.
 .TP
 .B --dumpfile=<path/to/file>
 Specify the location of a pcap-format file which dnsmasq uses to dump copies of network packets for debugging purposes. If the file exists when dnsmasq starts, it is not deleted; new packets are added to the end.

src/dnsmasq.h

@@ -960,10 +960,10 @@ struct dhcp_bridge {
 };
 
 struct cond_domain {
-  char *domain, *prefix;
+  char *domain, *prefix; /* prefix is text-prefix on domain name */
   struct in_addr start, end;
   struct in6_addr start6, end6;
-  int is6, indexed;
+  int is6, indexed, prefixlen;
   struct cond_domain *next;
 }; 
 

src/domain.c

@@ -18,8 +18,9 @@
 
 
 static struct cond_domain *search_domain(struct in_addr addr, struct cond_domain *c);
+static int match_domain(struct in_addr addr, struct cond_domain *c);
 static struct cond_domain *search_domain6(struct in6_addr *addr, struct cond_domain *c);
-
+static int match_domain6(struct in6_addr *addr, struct cond_domain *c);
 
 int is_name_synthetic(int flags, char *name, union all_addr *addr)
 {
@@ -135,28 +136,9 @@ int is_name_synthetic(int flags, char *name, union all_addr *addr)
 	    }
 	  
 	  if (hostname_isequal(c->domain, p+1) && inet_pton(prot, tail, addr))
-	    {
+	    found = (prot == AF_INET) ? match_domain(addr->addr4, c) : match_domain6(&addr->addr6, c);
-	      if (prot == AF_INET)
-		{
-		  if (!c->is6 &&
-		      ntohl(addr->addr4.s_addr) >= ntohl(c->start.s_addr) &&
-		      ntohl(addr->addr4.s_addr) <= ntohl(c->end.s_addr))
-		    found = 1;
-		}
-	      else
-		{
-		  u64 addrpart = addr6part(&addr->addr6);
-		  
-		  if (c->is6 &&
-		      is_same_net6(&addr->addr6, &c->start6, 64) &&
-		      addrpart >= addr6part(&c->start6) &&
-		      addrpart <= addr6part(&c->end6))
-		    found = 1;
-		}
-	    }
-
 	}
-
+      
       /* restore name */
       for (p = tail; *p; p++)
 	if (*p == '.' || *p == ':')
@@ -246,14 +228,22 @@ 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))
+    return 1;
+
+  return 0;
+}
+
 static struct cond_domain *search_domain(struct in_addr addr, struct cond_domain *c)
 {
   for (; c; c = c->next)
-    if (!c->is6 &&
+    if (match_domain(addr, c))
-	ntohl(addr.s_addr) >= ntohl(c->start.s_addr) &&
-        ntohl(addr.s_addr) <= ntohl(c->end.s_addr))
       return c;
-
+  
   return NULL;
 }
 
@@ -267,16 +257,30 @@ char *get_domain(struct in_addr addr)
   return daemon->domain_suffix;
 } 
 
-
+static int match_domain6(struct in6_addr *addr, struct cond_domain *c)
-static struct cond_domain *search_domain6(struct in6_addr *addr, struct cond_domain *c)
 {
   u64 addrpart = addr6part(addr);
   
+  if (c->is6)
+    {
+      if (c->prefixlen >= 64)
+	{
+	  if (is_same_net6(addr, &c->start6, 64) &&
+	      addrpart >= addr6part(&c->start6) &&
+	      addrpart <= addr6part(&c->end6))
+	    return 1;
+	}
+      else if (is_same_net6(addr, &c->start6, c->prefixlen))
+	return 1;
+    }
+
+  return 0;
+}
+
+static struct cond_domain *search_domain6(struct in6_addr *addr, struct cond_domain *c)
+{
   for (; c; c = c->next)
-    if (c->is6 &&
+    if (match_domain6(addr, c))
-	is_same_net6(addr, &c->start6, 64) &&
-	addrpart >= addr6part(&c->start6) &&
-        addrpart <= addr6part(&c->end6))
       return c;
   
   return NULL;

src/option.c

@@ -2268,6 +2268,7 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
 		  
 		  new->prefix = NULL;
 		  new->indexed = 0;
+		  new->prefixlen = 0;
 		  
 		  unhide_metas(comma);
 		  if ((netpart = split_chr(comma, '/')))
@@ -2313,16 +2314,17 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
 			  u64 mask = (1LLU << (128 - msize)) - 1LLU;
 			  u64 addrpart = addr6part(&new->start6);
 			  new->is6 = 1;
+			  new->prefixlen = msize;
 			  
 			  /* prefix==64 overflows the mask calculation above */
-			  if (msize == 64)
+			  if (msize <= 64)
 			    mask = (u64)-1LL;
 			  
 			  new->end6 = new->start6;
 			  setaddr6part(&new->start6, addrpart & ~mask);
 			  setaddr6part(&new->end6, addrpart | mask);
 			  
-			  if (msize < 64)
+			  if (msize < 64 && option  == 's')
 			    ret_err_free(gen_err, new);
 			  else if (arg)
 			    {
@@ -2393,15 +2395,17 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
 		  else
 		    {
 		      char *star;
-		      new->next = daemon->synth_domains;
-		      daemon->synth_domains = new;
 		      if (new->prefix &&
 			  (star = strrchr(new->prefix, '*'))
 			  && *(star+1) == 0)
 			{
 			  *star = 0;
 			  new->indexed = 1;
+			  if (new->is6 && new->prefixlen < 64)
+			    ret_err_free(_("prefix too small"), new);
 			}
+		      new->next = daemon->synth_domains;
+		      daemon->synth_domains = new;
 		    }
 		}
 	      else if (option == 's')