# ipv6_onoff.dpatch by Francesco Paolo Lovergine <frankie@debian.org>

diff -urNad proftpd-dfsg-1.3.0~/include/netaddr.h proftpd-dfsg-1.3.0/include/netaddr.h
--- proftpd-dfsg-1.3.0~/include/netaddr.h	2006-11-22 19:44:32.000000000 +0100
+++ proftpd-dfsg-1.3.0/include/netaddr.h	2006-11-22 19:44:46.000000000 +0100
@@ -1,6 +1,6 @@
 /*
  * ProFTPD - FTP server daemon
- * Copyright (c) 2003-2005 The ProFTPD Project team
+ * Copyright (c) 2003-2006 The ProFTPD Project team
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -344,7 +344,7 @@
 /* Returns TRUE if the given pr_netaddr_t contains a loopback address,
  * FALSE otherwise.
  */
-int pr_netaddr_loopback(const pr_netaddr_t *);
+int pr_netaddr_is_loopback(const pr_netaddr_t *);
 
 /* Returns TRUE if the given pr_netaddr_t is of the AF_INET6 family and
  * contains an IPv4-mapped IPv6 address; otherwise FALSE is returned.  A
@@ -352,6 +352,15 @@
  */
 int pr_netaddr_is_v4mappedv6(const pr_netaddr_t *);
 
+/* Returns TRUE if IPv6 support is enabled, FALSE otherwise. */
+unsigned char pr_netaddr_use_ipv6(void);
+
+/* Disables runtime use of IPv6 functionality (assuming IPv6 is supported). */
+void pr_netaddr_disable_ipv6(void);
+
+/* Enables runtime use of IPv6 functionality (assuming IPv6 is supported). */
+void pr_netaddr_enable_ipv6(void);
+
 /* Return pointers to static memory which contains the local and remote
  * netaddr information for the sesssion.  DO NOT MODIFY the pointed-to
  * memory!  Returns NULL if no such session information exists.
diff -urNad proftpd-dfsg-1.3.0~/modules/mod_core.c proftpd-dfsg-1.3.0/modules/mod_core.c
--- proftpd-dfsg-1.3.0~/modules/mod_core.c	2006-11-22 19:44:45.000000000 +0100
+++ proftpd-dfsg-1.3.0/modules/mod_core.c	2006-11-22 19:48:23.000000000 +0100
@@ -448,14 +448,16 @@
       const char *ipstr = pr_netaddr_get_ipstr(elts[i]);
 
 #ifdef PR_USE_IPV6
-      char ipbuf[INET6_ADDRSTRLEN];
-      if (pr_netaddr_get_family(elts[i]) == AF_INET) {
+      if (pr_netaddr_use_ipv6()) {
+        char *ipbuf = pcalloc(cmd->tmp_pool, INET6_ADDRSTRLEN);
+        if (pr_netaddr_get_family(elts[i]) == AF_INET) {
 
-        /* Create the bind record using the IPv4-mapped IPv6 version of
-         * this address.
-         */
-        snprintf(ipbuf, sizeof(ipbuf), "::ffff:%s", ipstr);
-        ipstr = ipbuf;
+          /* Create the bind record using the IPv4-mapped IPv6 version of
+           * this address.
+           */
+          snprintf(ipbuf, sizeof(ipbuf), "::ffff:%s", ipstr);
+          ipstr = ipbuf;
+        }
       }
 #endif /* PR_USE_IPV6 */
 
@@ -601,6 +603,33 @@
   return HANDLED(cmd);
 }
 
+/* usage: UseIPv6 on|off */
+MODRET set_useipv6(cmd_rec *cmd) {
+#ifdef PR_USE_IPV6
+  int bool = -1;
+
+  CHECK_ARGS(cmd, 1);
+  CHECK_CONF(cmd, CONF_ROOT);
+
+  bool = get_boolean(cmd, 1);
+  if (bool == -1)
+    CONF_ERROR(cmd, "expected Boolean parameter");
+
+  if (bool == 0) {
+    pr_log_debug(DEBUG2, "disabling runtime support for IPv6 connections");
+    pr_netaddr_disable_ipv6();
+
+  } else {
+    pr_netaddr_enable_ipv6();
+  }
+
+  return HANDLED(cmd);
+#else
+  CONF_ERROR(cmd,
+    "Use of the UseIPv6 directive requires IPv6 support (--enable-ipv6)");
+#endif /* PR_USE_IPV6 */
+}
+
 MODRET set_usereversedns(cmd_rec *cmd) {
   int bool = -1;
 
@@ -3110,9 +3139,15 @@
   port = ((p1 << 8) | p2);
 
 #ifdef PR_USE_IPV6
-  if (pr_netaddr_get_family(session.c->remote_addr) == AF_INET6)
-    snprintf(buf, sizeof(buf), "::ffff:%u.%u.%u.%u", h1, h2, h3, h4);
-  else
+  if (pr_netaddr_use_ipv6()) {
+    if (pr_netaddr_get_family(session.c->remote_addr) == AF_INET6) {
+      snprintf(buf, sizeof(buf), "::ffff:%u.%u.%u.%u", h1, h2, h3, h4);
+
+    } else {
+      snprintf(buf, sizeof(buf), "%u.%u.%u.%u", h1, h2, h3, h4);
+    }
+
+  } else
 #endif /* PR_USE_IPV6 */
   snprintf(buf, sizeof(buf), "%u.%u.%u.%u", h1, h2, h3, h4);
   buf[sizeof(buf)-1] = '\0';
@@ -3139,15 +3174,17 @@
     pr_netaddr_t *remote_addr = session.c->remote_addr;
 
 #ifdef PR_USE_IPV6
-    /* We can only compare the PORT-given address against the remote client
-     * address if the remote client address is an IPv4-mapped IPv6 address.
-     */
-    if (pr_netaddr_get_family(remote_addr) == AF_INET6 &&
-        pr_netaddr_is_v4mappedv6(remote_addr) != TRUE) {
-      pr_log_pri(PR_LOG_WARNING, "Refused PORT %s (IPv4/IPv6 address mismatch)",
-        cmd->arg);
-      pr_response_add_err(R_500, "Illegal PORT command");
-      return ERROR(cmd);
+     if (pr_netaddr_use_ipv6()) {
+       /* We can only compare the PORT-given address against the remote client
+        * address if the remote client address is an IPv4-mapped IPv6 address.
+        */
+       if (pr_netaddr_get_family(remote_addr) == AF_INET6 &&
+           pr_netaddr_is_v4mappedv6(remote_addr) != TRUE) {
+         pr_log_pri(PR_LOG_WARNING,
+           "Refused PORT %s (IPv4/IPv6 address mismatch)", cmd->arg);
+         pr_response_add_err(R_500, "Illegal PORT command");
+         return ERROR(cmd);
+       }
     }
 #endif /* PR_USE_IPV6 */
 
@@ -3244,12 +3281,16 @@
 
 #ifdef PR_USE_IPV6
     case 2:
-      break;
+       if (pr_netaddr_use_ipv6())
+         break;
 #endif /* PR_USE_IPV6 */
 
     default:
 #ifdef PR_USE_IPV6
-      pr_response_add_err(R_522, "Network protocol not supported, use (1,2)");
+       if (pr_netaddr_use_ipv6())
+         pr_response_add_err(R_522, "Network protocol not supported, use (1,2)");
+       else
+         pr_response_add_err(R_522, "Network protocol not supported, use (1)");
 #else
       pr_response_add_err(R_522, "Network protocol not supported, use (1)");
 #endif /* PR_USE_IPV6 */
@@ -3435,8 +3476,10 @@
 
 #ifdef PR_USE_IPV6
       case AF_INET6:
-        family = 2;
-        break;
+        if (pr_netaddr_use_ipv6()) {
+          family = 2;
+          break;
+        }
 #endif /* PR_USE_IPV6 */
 
       default:
@@ -3451,12 +3494,16 @@
 
 #ifdef PR_USE_IPV6
     case 2:
-      break;
+       if (pr_netaddr_use_ipv6())
+         break;
 #endif /* PR_USE_IPV6 */
 
     default:
 #ifdef PR_USE_IPV6
-      pr_response_add_err(R_522, "Network protocol not supported, use (1,2)");
+       if (pr_netaddr_use_ipv6())
+         pr_response_add_err(R_522, "Network protocol not supported, use (1,2)");
+       else
+         pr_response_add_err(R_522, "Network protocol not supported, use (1)");
 #else
       pr_response_add_err(R_522, "Network protocol not supported, use (1)");
 #endif /* PR_USE_IPV6 */
@@ -4619,6 +4666,7 @@
   { "TransferLog",		add_transferlog,		NULL },
   { "Umask",			set_umask,			NULL },
   { "UnsetEnv",			set_unsetenv,			NULL },
+  { "UseIPv6",			set_useipv6,			NULL },
   { "UseReverseDNS",		set_usereversedns,		NULL },
   { "User",			set_user,			NULL },
   { "UserOwner",		add_userowner,			NULL },
diff -urNad proftpd-dfsg-1.3.0~/src/bindings.c proftpd-dfsg-1.3.0/src/bindings.c
--- proftpd-dfsg-1.3.0~/src/bindings.c	2006-11-22 19:44:32.000000000 +0100
+++ proftpd-dfsg-1.3.0/src/bindings.c	2006-11-22 19:44:46.000000000 +0100
@@ -57,10 +57,6 @@
 static pr_ipbind_t *ipbind_default_server = NULL,
                    *ipbind_localhost_server = NULL;
 
-#ifdef PR_USE_IPV6
-static int ipv6_supported = TRUE;
-#endif /* PR_USE_IPV6 */
-
 /* Server cleanup callback function */
 static void server_cleanup_cb(void *conn) {
   *((conn_t **) conn) = NULL;
@@ -464,7 +460,7 @@
   /* Not found in binding list, and no DefaultServer, so see if it's the
    * loopback address
    */
-  if (ipbind_localhost_server && pr_netaddr_loopback(addr))
+  if (ipbind_localhost_server && pr_netaddr_is_loopback(addr))
       return ipbind_localhost_server->ib_server;
 
   return NULL;
@@ -863,7 +859,7 @@
      */
     if (!SocketBindTight) {
 #ifdef PR_USE_IPV6
-      if (ipv6_supported) {
+      if (pr_netaddr_use_ipv6()) {
         pr_inet_set_default_family(NULL, AF_INET6);
 
       } else {
@@ -907,7 +903,7 @@
       if (serv->ServerPort) {
         if (!SocketBindTight) {
 #ifdef PR_USE_IPV6
-          if (ipv6_supported) {
+          if (pr_netaddr_use_ipv6()) {
             pr_inet_set_default_family(NULL, AF_INET6);
 
           } else {
@@ -973,7 +969,7 @@
   /* Check to see whether we can actually create an IPv6 socket. */
   sock = socket(AF_INET6, SOCK_STREAM, IPPROTO_TCP);
   if (sock < 0) {
-    ipv6_supported = FALSE;
+    pr_netaddr_disable_ipv6();
 
   } else {
     close(sock);
diff -urNad proftpd-dfsg-1.3.0~/src/dirtree.c proftpd-dfsg-1.3.0/src/dirtree.c
--- proftpd-dfsg-1.3.0~/src/dirtree.c	2006-11-22 19:44:32.000000000 +0100
+++ proftpd-dfsg-1.3.0/src/dirtree.c	2006-11-22 19:44:46.000000000 +0100
@@ -2830,14 +2830,16 @@
           const char *ipstr = pr_netaddr_get_ipstr(elts[i]);
 
 #ifdef PR_USE_IPV6
-          char ipbuf[INET6_ADDRSTRLEN];
-          if (pr_netaddr_get_family(elts[i]) == AF_INET) {
+          if (pr_netaddr_use_ipv6()) {
+            char *ipbuf = pcalloc(s->pool, INET6_ADDRSTRLEN);
+            if (pr_netaddr_get_family(elts[i]) == AF_INET) {
 
-            /* Create the bind record using the IPv4-mapped IPv6 version of
-             * this address.
-             */
-            snprintf(ipbuf, sizeof(ipbuf), "::ffff:%s", ipstr);
-            ipstr = ipbuf;
+              /* Create the bind record using the IPv4-mapped IPv6 version of
+               * this address.
+               */
+              snprintf(ipbuf, sizeof(ipbuf), "::ffff:%s", ipstr);
+              ipstr = ipbuf;
+            }
           }
 #endif /* PR_USE_IPV6 */
 
diff -urNad proftpd-dfsg-1.3.0~/src/inet.c proftpd-dfsg-1.3.0/src/inet.c
--- proftpd-dfsg-1.3.0~/src/inet.c	2006-11-22 19:44:32.000000000 +0100
+++ proftpd-dfsg-1.3.0/src/inet.c	2006-11-22 19:44:46.000000000 +0100
@@ -209,7 +209,11 @@
      * support is enabled), otherwise use IPv4.
      */
 #ifdef PR_USE_IPV6
-    addr_family = AF_INET6;
+    if (pr_netaddr_use_ipv6())
+      addr_family = AF_INET6;
+
+    else
+      addr_family = AF_INET;
 #else
     addr_family = AF_INET;
 #endif /* PR_USE_IPV6 */
@@ -292,7 +296,8 @@
       pr_netaddr_set_sockaddr_any(&na);
 
 #if defined(PR_USE_IPV6) && defined(IPV6_V6ONLY)
-    if (addr_family == AF_INET6) {
+    if (pr_netaddr_use_ipv6() &&
+        addr_family == AF_INET6) {
       int on = 0;
 
 # ifdef SOL_IP
@@ -1019,7 +1024,11 @@
   pr_netaddr_clear(&na);
 
 #ifdef PR_USE_IPV6
-  pr_netaddr_set_family(&na, AF_INET6);
+  if (pr_netaddr_use_ipv6())
+    pr_netaddr_set_family(&na, AF_INET6);
+
+  else
+    pr_netaddr_set_family(&na, AF_INET);
 #else
   pr_netaddr_set_family(&na, AF_INET);
 #endif /* PR_USE_IPV6 */
@@ -1044,7 +1053,11 @@
 
   /* "Reset" the pr_netaddr_t struct for the getpeername(2) call. */
 #ifdef PR_USE_IPV6
-  pr_netaddr_set_family(&na, AF_INET6);
+  if (pr_netaddr_use_ipv6())
+    pr_netaddr_set_family(&na, AF_INET6);
+
+  else
+    pr_netaddr_set_family(&na, AF_INET);
 #else
   pr_netaddr_set_family(&na, AF_INET);
 #endif /* PR_USE_IPV6 */
diff -urNad proftpd-dfsg-1.3.0~/src/main.c proftpd-dfsg-1.3.0/src/main.c
--- proftpd-dfsg-1.3.0~/src/main.c	2006-11-22 19:44:45.000000000 +0100
+++ proftpd-dfsg-1.3.0/src/main.c	2006-11-22 19:44:46.000000000 +0100
@@ -2553,6 +2553,10 @@
     "Print version number and exit" },
   { "--version-status", "-vv",
     "Print extended version information and exit" },
+  { "--ipv4", "-4",
+    "Support IPv4 connections only" },
+  { "--ipv6", "-6",
+    "Support IPv6 connections" },
   { NULL, NULL, NULL }
 };
 
@@ -2574,7 +2578,7 @@
 
 int main(int argc, char *argv[], char **envp) {
   int optc, show_version = 0;
-  const char *cmdopts = "D:NVc:d:hlnp:qtv";
+  const char *cmdopts = "D:NVc:d:hlnp:qtv46";
   mode_t *main_umask = NULL;
   socklen_t peerlen;
   struct sockaddr peer;
@@ -2658,6 +2662,10 @@
    * --configtest
    * -v                 report version number
    * --version
+   * -4                 support IPv4 connections only
+   * --ipv4
+   * -6                 support IPv6 connections
+   * --ipv6
    */
 
   opterr = 0;
@@ -2755,6 +2763,12 @@
     case 'h':
       show_usage(0);
 
+    case 4:
+      pr_netaddr_disable_ipv6();
+
+    case 6:
+      pr_netaddr_enable_ipv6();
+
     case '?':
       pr_log_pri(PR_LOG_ERR, "unknown option: %c", (char)optopt);
       show_usage(1);
diff -urNad proftpd-dfsg-1.3.0~/src/netacl.c proftpd-dfsg-1.3.0/src/netacl.c
--- proftpd-dfsg-1.3.0~/src/netacl.c	2006-11-22 19:44:45.000000000 +0100
+++ proftpd-dfsg-1.3.0/src/netacl.c	2006-11-22 19:44:46.000000000 +0100
@@ -172,19 +172,20 @@
 
 #ifdef PR_USE_IPV6
       case AF_INET6: {
-        if (acl->masklen > 128) {
-           errno = EINVAL;
-           return NULL;
-
-        } else if (pr_netaddr_is_v4mappedv6(acl->addr) == TRUE &&
-                   acl->masklen > 32) {
-
-          /* The admin may be trying to use IPv6-style masks on IPv4-mapped
-           * IPv6 addresses, which of course will not work as expected. 
-           * If the mask is 32 bits or more, warn the admin.
-           */
-          pr_log_pri(PR_LOG_WARNING, "warning: possibly using IPv6-style netmask on IPv4-mapped IPv6 address, which will not work as expected");
-          break;
+         if (pr_netaddr_use_ipv6()) {
+           if (acl->masklen > 128) {
+             errno = EINVAL;
+             return NULL;
+ 
+           } else if (pr_netaddr_is_v4mappedv6(acl->addr) == TRUE &&
+                      acl->masklen > 32) {
+             /* The admin may be trying to use IPv6-style masks on IPv4-mapped
+              * IPv6 addresses, which of course will not work as expected.
+              * If the mask is 32 bits or more, warn the admin.
+              */
+             pr_log_pri(PR_LOG_WARNING, "warning: possibly using IPv6-style netmask on IPv4-mapped IPv6 address, which will not work as expected");
+             break;
+           }
         }
       }
 #endif /* PR_USE_IPV6 */
@@ -194,7 +195,7 @@
     }
 
 #ifdef PR_USE_IPV6
-  } else if (strspn(aclstr, "0123456789ABCDEFabcdef.:") != strlen(aclstr)) {
+  } else if (pr_netaddr_use_ipv6() && strspn(aclstr, "0123456789ABCDEFabcdef.:") != strlen(aclstr)) {
 #else
   } else if (strspn(aclstr, "0123456789.") != strlen(aclstr)) {
 #endif /* PR_USE_IPV6 */
diff -urNad proftpd-dfsg-1.3.0~/src/netaddr.c proftpd-dfsg-1.3.0/src/netaddr.c
--- proftpd-dfsg-1.3.0~/src/netaddr.c	2006-11-22 19:44:45.000000000 +0100
+++ proftpd-dfsg-1.3.0/src/netaddr.c	2006-11-22 19:44:46.000000000 +0100
@@ -43,6 +43,13 @@
 /* Do reverse DNS lookups? */
 static int reverse_dns = 1;
 
+/* Use IPv6? */
+#ifdef PR_USE_IPV6
+static int use_ipv6 = TRUE;
+#else
+static int use_ipv6 = FALSE;
+#endif /* PR_USE_IPV6 */
+
 /* Provide replacements for needed functions. */
 
 #if !defined(HAVE_GETNAMEINFO) || defined(PR_USE_GETNAMEINFO)
@@ -276,9 +283,6 @@
     array_header **addrs) {
 
   struct sockaddr_in v4;
-#ifdef PR_USE_IPV6
-  struct sockaddr_in6 v6;
-#endif /* PR_USE_IPV6 */
   pr_netaddr_t *na = NULL;
   int res;
 
@@ -300,23 +304,26 @@
   na = (pr_netaddr_t *) pcalloc(p, sizeof(pr_netaddr_t));
 
 #ifdef PR_USE_IPV6
-  memset(&v6, 0, sizeof(v6));
-  v6.sin6_family = AF_INET6;
+  if (use_ipv6) {
+    struct sockaddr_in6 v6;
+    memset(&v6, 0, sizeof(v6));
+    v6.sin6_family = AF_INET6;
 
 # ifdef SIN6_LEN
-  v6.sin6_len = sizeof(struct sockaddr_in6);
+    v6.sin6_len = sizeof(struct sockaddr_in6);
 # endif /* SIN6_LEN */
 
-  res = pr_inet_pton(AF_INET6, name, &v6.sin6_addr);
-  if (res > 0) {
-    pr_netaddr_set_family(na, AF_INET6);
-    pr_netaddr_set_sockaddr(na, (struct sockaddr *) &v6);
-    if (addrs)
-      *addrs = NULL;
+    res = pr_inet_pton(AF_INET6, name, &v6.sin6_addr);
+    if (res > 0) {
+      pr_netaddr_set_family(na, AF_INET6);
+      pr_netaddr_set_sockaddr(na, (struct sockaddr *) &v6);
+      if (addrs)
+        *addrs = NULL;
 
-    pr_log_debug(DEBUG10, "'%s' resolved to IPv6 address %s", name,
-      pr_netaddr_get_ipstr(na));
-    return na;
+      pr_log_debug(DEBUG10, "'%s' resolved to IPv6 address %s", name,
+        pr_netaddr_get_ipstr(na));
+      return na;
+    }
   }
 #endif /* PR_USE_IPV6 */
 
@@ -377,7 +384,7 @@
     }
 
 #ifdef PR_USE_IPV6
-    if (addrs) {
+    if (use_ipv6 && addrs) {
       /* Do the call again, this time for IPv6 addresses.
        *
        * We make two separate getaddrinfo(3) calls, rather than one
@@ -454,8 +461,10 @@
 
 #ifdef PR_USE_IPV6
     case AF_INET6:
-      na->na_addr.v6.sin6_family = AF_INET6;
-      break;
+      if (use_ipv6) {
+        na->na_addr.v6.sin6_family = AF_INET6;
+        break;
+      }
 #endif /* PR_USE_IPV6 */
 
     default:
@@ -483,7 +492,8 @@
  
 #ifdef PR_USE_IPV6
     case AF_INET6:
-      return sizeof(struct sockaddr_in6);
+      if (use_ipv6)
+        return sizeof(struct sockaddr_in6);
 #endif /* PR_USE_IPV6 */   
   }
 
@@ -503,7 +513,8 @@
 
 #ifdef PR_USE_IPV6
     case AF_INET6:
-      return sizeof(struct in6_addr);
+      if (use_ipv6)
+        return sizeof(struct in6_addr);
 #endif /* PR_USE_IPV6 */
   }
 
@@ -523,7 +534,8 @@
 
 #ifdef PR_USE_IPV6
     case AF_INET6:
-      return (struct sockaddr *) &na->na_addr.v6;
+      if (use_ipv6)
+        return (struct sockaddr *) &na->na_addr.v6;
 #endif /* PR_USE_IPV6 */
   }
 
@@ -545,8 +557,10 @@
 
 #ifdef PR_USE_IPV6
     case AF_INET6:
-      memcpy(&(na->na_addr.v6), addr, sizeof(struct sockaddr_in6));
-      return 0;
+      if (use_ipv6) {
+        memcpy(&(na->na_addr.v6), addr, sizeof(struct sockaddr_in6));
+        return 0;
+      }
 #endif /* PR_USE_IPV6 */
   }
 
@@ -574,12 +588,14 @@
 
 #ifdef PR_USE_IPV6
     case AF_INET6:
-      na->na_addr.v6.sin6_family = AF_INET6;
+      if (use_ipv6) {
+        na->na_addr.v6.sin6_family = AF_INET6;
 #ifdef SIN6_LEN
-      na->na_addr.v6.sin6_len = sizeof(struct sockaddr_in6);
+        na->na_addr.v6.sin6_len = sizeof(struct sockaddr_in6);
 #endif /* SIN6_LEN */
-      memcpy(&na->na_addr.v6.sin6_addr, &in6addr_any, sizeof(struct in6_addr));
-      return 0;
+        memcpy(&na->na_addr.v6.sin6_addr, &in6addr_any, sizeof(struct in6_addr));
+        return 0;
+      }
 #endif /* PR_USE_IPV6 */
   }
 
@@ -599,7 +615,8 @@
 
 #ifdef PR_USE_IPV6
     case AF_INET6:
-      return (void *) &na->na_addr.v6.sin6_addr;
+      if (use_ipv6)
+        return (void *) &na->na_addr.v6.sin6_addr;
 #endif /* PR_USE_IPV6 */
   }
 
@@ -619,7 +636,8 @@
 
 #ifdef PR_USE_IPV6
     case AF_INET6:
-      return na->na_addr.v6.sin6_port;
+      if (use_ipv6)
+        return na->na_addr.v6.sin6_port;
 #endif /* PR_USE_IPV6 */
   }
 
@@ -640,8 +658,10 @@
 
 #ifdef PR_USE_IPV6
     case AF_INET6:
-      na->na_addr.v6.sin6_port = port;
-      return 0;
+      if (use_ipv6) {
+        na->na_addr.v6.sin6_port = port;
+        return 0;
+      }
 #endif /* PR_USE_IPV6 */
   }
 
@@ -724,11 +744,13 @@
 
 #ifdef PR_USE_IPV6
     case AF_INET6:
-      res = memcmp(&a->na_addr.v6.sin6_addr, &b->na_addr.v6.sin6_addr,
-        sizeof(struct in6_addr));
-      if (tmp_pool);
-        destroy_pool(tmp_pool);
-      return res;
+       if (use_ipv6) {
+         res = memcmp(&a->na_addr.v6.sin6_addr, &b->na_addr.v6.sin6_addr,
+           sizeof(struct in6_addr));
+         if (tmp_pool)
+           destroy_pool(tmp_pool);
+         return res;
+       }
 #endif /* PR_USE_IPV6 */
   }
 
@@ -821,15 +843,17 @@
 
 #ifdef PR_USE_IPV6
     case AF_INET6: {
-      /* Make sure that the given number of bits is not more than supported
-       * for IPv6 addresses (128).
-       */
-      if (bitlen > 128) {
-        errno = EINVAL;
-        return -1;
-      }
+      if (use_ipv6) {
+        /* Make sure that the given number of bits is not more than supported
+         * for IPv6 addresses (128).
+         */
+        if (bitlen > 128) {
+          errno = EINVAL;
+          return -1;
+        }
 
-      break;
+        break;
+      }
     }
 #endif /* PR_USE_IPV6 */
 
@@ -1029,7 +1053,7 @@
 
 #ifdef PR_USE_IPV6
           case AF_INET6:
-            if (family == AF_INET6) {
+            if (use_ipv6 && family == AF_INET6) {
               for (checkaddr = hent->h_addr_list; *checkaddr; ++checkaddr) {
                 if (memcmp(*checkaddr, inaddr, hent->h_length) == 0) {
                   ok = TRUE;
@@ -1090,7 +1114,7 @@
   return NULL;
 }
 
-int pr_netaddr_loopback(const pr_netaddr_t *na) {
+int pr_netaddr_is_loopback(const pr_netaddr_t *na) {
   if (!na) {
     errno = EINVAL;
     return -1;
@@ -1103,7 +1127,6 @@
 
 #ifdef PR_USE_IPV6
     case AF_INET6:
-
       /* XXX *sigh* Different platforms implement the IN6_IS_ADDR macros
        * differently.  For example, on Linux, those macros expect to operate
        * on s6_addr32, while on Solaris, the macros operate on struct in6_addr.
@@ -1175,7 +1198,11 @@
       return -1;
 
 #ifdef PR_USE_IPV6
-    case AF_INET6:
+    case AF_INET6: {
+      if (!use_ipv6) {
+        errno = EINVAL;
+        return -1;
+      }
 
 # ifndef LINUX
       return IN6_IS_ADDR_V4MAPPED(
@@ -1184,6 +1211,7 @@
       return IN6_IS_ADDR_V4MAPPED(
         ((struct in6_addr *) pr_netaddr_get_inaddr(na))->s6_addr32);
 # endif
+    }
 #endif /* PR_USE_IPV6 */
   }
 
@@ -1234,3 +1262,22 @@
   sstrncpy(sess_remote_name, session.c->remote_name, sizeof(sess_remote_name));
   have_sess_remote_addr = TRUE;
 }
+
+unsigned char pr_netaddr_use_ipv6(void) {
+  if (use_ipv6)
+    return TRUE;
+
+  return FALSE;
+}
+
+void pr_netaddr_disable_ipv6(void) {
+#ifdef PR_USE_IPV6
+  use_ipv6 = 0;
+#endif /* PR_USE_IPV6 */
+}
+
+void pr_netaddr_enable_ipv6(void) {
+#ifdef PR_USE_IPV6
+  use_ipv6 = 1;
+#endif /* PR_USE_IPV6 */
+}