DNS Update fix. A misconfigured server could crash during DNS update

processing if the configuration included overlapping pools or
multiple fixed-address entries for a single address.  This issue
affected both IPv4 and IPv6. The fix allows a server to detect such
conditions, provides the user with extra information and recommended
steps to fix the problem.  If the user enables the appropriate option
in site.h then server will be terminated

includes/dhcpd.h

@@ -3,7 +3,7 @@
    Definitions for dhcpd... */
 
 /*
- * Copyright (c) 2004-2010 by Internet Systems Consortium, Inc. ("ISC")
+ * Copyright (c) 2004-2011 by Internet Systems Consortium, Inc. ("ISC")
  * Copyright (c) 1996-2003 by Internet Software Consortium
  *
  * Permission to use, copy, modify, and distribute this software for any
@@ -3529,3 +3529,6 @@ ddns_modify_ptr(dhcp_ddns_cb_t *ddns_cb);
 
 void
 ddns_cancel(dhcp_ddns_cb_t *ddns_cb);
+
+#define MAX_ADDRESS_STRING_LEN \
+   (sizeof("ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"))

includes/site.h

@@ -217,6 +217,10 @@
    but is only included for backwards compatibility. */
 /* #define REPLY_TO_SOURCE_PORT */
 
+/* Define this if you want to enable strict checks in DNS Updates mechanism.
+   Do not enable this unless are DHCP developer. */
+/* #define DNS_UPDATES_MEMORY_CHECKS */
+
 /* Define this if you want to allow domain list in domain-name option.
    RFC2132 does not allow that behavior, but it is somewhat used due
    to historic reasons. Note that it may be removed some time in the