Wildcard IPv6 addresses in --dhcp-host, for constructed ranges.

man/dnsmasq.8

@@ -717,7 +717,13 @@ A single
 .B dhcp-host 
 may contain an IPv4 address or an IPv6 address, or both. IPv6 addresses must be bracketed by square brackets thus:
 .B --dhcp-host=laptop,[1234::56]
-Note that in IPv6 DHCP, the hardware address is not normally available, so a client must be identified by client-id (called client DUID in IPv6-land) or hostname.
+IPv6 addresses may contain only the host-identifier part:
+.B --dhcp-host=laptop,[::56]
+in which case thay act as wildcards in constructed dhcp ranges, with
+the appropriate network part inserted. 
+Note that in IPv6 DHCP, the hardware address is not normally
+available, so a client must be identified by client-id (called client
+DUID in IPv6-land) or hostname. 
 
 The special option id:* means "ignore any client-id 
 and use MAC addresses only." This is useful when a client presents a client-id sometimes 

src/dhcp6.c

@@ -399,11 +399,19 @@ struct dhcp_context *narrow_context6(struct dhcp_context *context,
 
 static int is_config_in_context6(struct dhcp_context *context, struct dhcp_config *config)
 {
-  if (!context) /* called via find_config() from lease_update_from_configs() */
-    return 1; 
+  /* expand wildcard on contructed contexts */
+  if ((config->flags & CONFIG_WILDCARD) && 
+      (context->flags & CONTEXT_CONSTRUCTED))
+    {
+      u64 addrpart = addr6part(&config->addr6);
+      config->addr6 = context->start6;
+      setaddr6part(&config->addr6, addrpart);
+      return 1;
+    }
+  
   if (!(config->flags & CONFIG_ADDR6) || is_addr_in_context6(context, &config->addr6))
     return 1;
-  
+      
   return 0;
 }
 

src/dnsmasq.h

@@ -593,6 +593,7 @@ struct dhcp_config {
 #define CONFIG_DECLINED       1024    /* address declined by client */
 #define CONFIG_BANK           2048    /* from dhcp hosts file */
 #define CONFIG_ADDR6          4096
+#define CONFIG_WILDCARD       8192
 
 struct dhcp_opt {
   int opt, len, flags;

src/option.c

@@ -2468,6 +2468,14 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
 		  
 		  if (!inet_pton(AF_INET6, arg, &new->addr6))
 		    ret_err(_("bad IPv6 address"));
+
+		  for (i= 0; i < 8; i++)
+		    if (new->addr6.s6_addr[i] != 0)
+		      break;
+
+		  /* set WILDCARD if network part all zeros */
+		  if (i == 8)
+		    new->flags |= CONFIG_WILDCARD;
 		  
 		  new->flags |= CONFIG_ADDR6;
 		}