--- helodnscheck2.c.orig	2011-06-15 22:30:55.571844910 +0200
+++ helodnscheck2.c	2011-06-16 08:17:36.919991526 +0200
@@ -17,6 +17,8 @@
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 ***
+* 2011-06-16 Modified to work in dualstack environment
+*            (IPv6 support) Carsten Schoene <cs@linux-administrator.com>
 * 1/16 Modified original version to check helo/ehlo instead of mail from
 ***
 *
@@ -80,6 +82,7 @@
  char *remote_ip = getenv("TCPREMOTEIP");
  char *action = getenv("HELO_DNS_CHECK");
  struct hostent* result;
+ int fIPv4 = 0;
 
   if (!action) {
     action = "";
@@ -101,11 +104,15 @@
     return 0;
   }
 
+  fIPv4 = (NULL == strchr(remote_ip, ':'));
 
   /* init DNS library */
   res_init();
 
   /* check A record */
+  if (!fIPv4) {
+  	_res.options |= RES_USE_INET6;
+  }
   result = gethostbyname(helo_domain);
 
   /* check if there is any result */
@@ -175,7 +182,11 @@
   count=0;
   while (result->h_addr_list[count] && (found==0)) {
      addr=result->h_addr_list[count];
-     inet_ntop(AF_INET, addr, print_address, 1000);
+     if (!fIPv4) {
+     	inet_ntop(AF_INET6, addr, print_address, 1000);
+     } else {
+	inet_ntop(AF_INET, addr, print_address, 1000);
+     }
      if (strcmp(print_address, remote_ip) == 0) {
 	found = 1;
      };