This is the start of the BETA21 branch.

It includes the --topology feature, and
TAP-Win32 driver changes to allow
non-admin access.



git-svn-id: http://svn.openvpn.net/projects/openvpn/branches/BETA21/openvpn@580 e7ae566f-a301-0410-adde-c780ea21d3b5

1 files changed, 3434 insertions, 0 deletions

diff --git a/tun.c b/tun.c
new file mode 100644
index 0000000..03df0c8
--- /dev/null
+++ b/tun.c
@@ -0,0 +1,3434 @@
+/*
+ *  OpenVPN -- An application to securely tunnel IP networks
+ *             over a single TCP/UDP port, with support for SSL/TLS-based
+ *             session authentication and key exchange,
+ *             packet encryption, packet authentication, and
+ *             packet compression.
+ *
+ *  Copyright (C) 2002-2005 OpenVPN Solutions LLC <info@openvpn.net>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2
+ *  as published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program (see the file COPYING included with this
+ *  distribution); if not, write to the Free Software Foundation, Inc.,
+ *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+/*
+ * Support routines for configuring and accessing TUN/TAP
+ * virtual network adapters.
+ *
+ * This file is based on the TUN/TAP driver interface routines
+ * from VTun by Maxim Krasnyansky <max_mk@yahoo.com>.
+ */
+
+#ifdef WIN32
+#include "config-win32.h"
+#else
+#include "config.h"
+#endif
+
+#include "syshead.h"
+
+#include "tun.h"
+#include "fdmisc.h"
+#include "common.h"
+#include "misc.h"
+#include "socket.h"
+#include "manage.h"
+
+#include "memdbg.h"
+
+#ifdef TARGET_SOLARIS
+static void solaris_error_close (struct tuntap *tt, const struct env_set *es, const char *actual);
+#endif
+
+bool
+is_dev_type (const char *dev, const char *dev_type, const char *match_type)
+{
+  ASSERT (match_type);
+  if (!dev)
+    return false;
+  if (dev_type)
+    return !strcmp (dev_type, match_type);
+  else
+    return !strncmp (dev, match_type, strlen (match_type));
+}
+
+int
+dev_type_enum (const char *dev, const char *dev_type)
+{
+  if (is_dev_type (dev, dev_type, "tun"))
+    return DEV_TYPE_TUN;
+  else if (is_dev_type (dev, dev_type, "tap"))
+    return DEV_TYPE_TAP;
+  else if (is_dev_type (dev, dev_type, "null"))
+    return DEV_TYPE_NULL;
+  else
+    return DEV_TYPE_UNDEF;
+}
+
+const char *
+dev_type_string (const char *dev, const char *dev_type)
+{
+  switch (dev_type_enum (dev, dev_type))
+    {
+    case DEV_TYPE_TUN:
+      return "tun";
+    case DEV_TYPE_TAP:
+      return "tap";
+    case DEV_TYPE_NULL:
+      return "null";
+    default:
+      return "[unknown-dev-type]";
+    }
+}
+
+const char *
+dev_component_in_dev_node (const char *dev_node)
+{
+  const char *ret;
+  const int dirsep = OS_SPECIFIC_DIRSEP;
+
+  if (dev_node)
+    {
+      ret = strrchr (dev_node, dirsep);
+      if (ret && *ret)
+	++ret;
+      else
+	ret = dev_node;
+      if (*ret)
+	return ret;
+    }
+  return NULL;
+}
+
+/*
+ * Try to predict the actual TUN/TAP device instance name,
+ * before the device is actually opened.
+ */
+const char *
+guess_tuntap_dev (const char *dev,
+		  const char *dev_type,
+		  const char *dev_node,
+		  struct gc_arena *gc)
+{
+#ifdef WIN32
+  const int dt = dev_type_enum (dev, dev_type);
+  if (dt == DEV_TYPE_TUN || dt == DEV_TYPE_TAP)
+    {
+      return get_netsh_id (dev_node, gc);
+    }
+#endif
+
+  /* default case */
+  return dev;
+}
+
+/*
+ * Called by the open_tun function of OSes to check if we
+ * explicitly support IPv6.
+ *
+ * In this context, explicit means that the OS expects us to
+ * do something special to the tun socket in order to support
+ * IPv6, i.e. it is not transparent.
+ *
+ * ipv6_explicitly_supported should be set to false if we don't
+ * have any explicit IPv6 code in the tun device handler.
+ *
+ * If ipv6_explicitly_supported is true, then we have explicit
+ * OS-specific tun dev code for handling IPv6.  If so, tt->ipv6
+ * is set according to the --tun-ipv6 command line option.
+ */
+static void
+ipv6_support (bool ipv6, bool ipv6_explicitly_supported, struct tuntap* tt)
+{
+  tt->ipv6 = false;
+  if (ipv6_explicitly_supported)
+    tt->ipv6 = ipv6;
+  else if (ipv6)
+    msg (M_WARN, "NOTE: explicit support for IPv6 tun devices is not provided for this OS");
+}
+
+/* --ifconfig-nowarn disables some options sanity checking */
+static const char ifconfig_warn_how_to_silence[] = "(silence this warning with --ifconfig-nowarn)";
+
+/*
+ * If !tun, make sure ifconfig_remote_netmask looks
+ *  like a netmask.
+ *
+ * If tun, make sure ifconfig_remote_netmask looks
+ *  like an IPv4 address.
+ */
+static void
+ifconfig_sanity_check (bool tun, in_addr_t addr)
+{
+  struct gc_arena gc = gc_new ();
+  const bool looks_like_netmask = ((addr & 0xFF000000) == 0xFF000000);
+  if (tun)
+    {
+      if (looks_like_netmask)
+	msg (M_WARN, "WARNING: Since you are using --dev tun, the second argument to --ifconfig must be an IP address.  You are using something (%s) that looks more like a netmask. %s",
+	     print_in_addr_t (addr, 0, &gc),
+	     ifconfig_warn_how_to_silence);
+    }
+  else /* tap */
+    {
+      if (!looks_like_netmask)
+	msg (M_WARN, "WARNING: Since you are using --dev tap, the second argument to --ifconfig must be a netmask, for example something like 255.255.255.0. %s",
+	     ifconfig_warn_how_to_silence);
+    }
+  gc_free (&gc);
+}
+
+/*
+ * For TAP-style devices, generate a broadcast address.
+ */
+static in_addr_t
+generate_ifconfig_broadcast_addr (in_addr_t local,
+				  in_addr_t netmask)
+{
+  return local | ~netmask;
+}
+
+/*
+ * Check that --local and --remote addresses do not
+ * clash with ifconfig addresses or subnet.
+ */
+static void
+check_addr_clash (const char *name,
+		  int type,
+		  in_addr_t public,
+		  in_addr_t local,
+		  in_addr_t remote_netmask)
+{
+  struct gc_arena gc = gc_new ();
+#if 0
+  msg (M_INFO, "CHECK_ADDR_CLASH type=%d public=%s local=%s, remote_netmask=%s",
+       type,
+       print_in_addr_t (public, 0, &gc),
+       print_in_addr_t (local, 0, &gc),
+       print_in_addr_t (remote_netmask, 0, &gc));
+#endif
+
+  if (public)
+    {
+      if (type == DEV_TYPE_TUN)
+	{
+	  const in_addr_t test_netmask = 0xFFFFFF00;
+	  const in_addr_t public_net = public & test_netmask;
+	  const in_addr_t local_net = local & test_netmask;
+	  const in_addr_t remote_net = remote_netmask & test_netmask;
+
+	  if (public == local || public == remote_netmask)
+	    msg (M_WARN,
+		 "WARNING: --%s address [%s] conflicts with --ifconfig address pair [%s, %s]. %s",
+		 name,
+		 print_in_addr_t (public, 0, &gc),
+		 print_in_addr_t (local, 0, &gc),
+		 print_in_addr_t (remote_netmask, 0, &gc),
+		 ifconfig_warn_how_to_silence);
+
+	  if (public_net == local_net || public_net == remote_net)
+	    msg (M_WARN,
+		 "WARNING: potential conflict between --%s address [%s] and --ifconfig address pair [%s, %s] -- this is a warning only that is triggered when local/remote addresses exist within the same /24 subnet as --ifconfig endpoints. %s",
+		 name,
+		 print_in_addr_t (public, 0, &gc),
+		 print_in_addr_t (local, 0, &gc),
+		 print_in_addr_t (remote_netmask, 0, &gc),
+		 ifconfig_warn_how_to_silence);
+	}
+      else if (type == DEV_TYPE_TAP)
+	{
+	  const in_addr_t public_network = public & remote_netmask;
+	  const in_addr_t virtual_network = local & remote_netmask;
+	  if (public_network == virtual_network)
+	    msg (M_WARN,
+		 "WARNING: --%s address [%s] conflicts with --ifconfig subnet [%s, %s] -- local and remote addresses cannot be inside of the --ifconfig subnet. %s",
+		 name,
+		 print_in_addr_t (public, 0, &gc),
+		 print_in_addr_t (local, 0, &gc),
+		 print_in_addr_t (remote_netmask, 0, &gc),
+		 ifconfig_warn_how_to_silence);
+	}
+    }
+  gc_free (&gc);
+}
+
+/*
+ * Complain if --dev tap and --ifconfig is used on an OS for which
+ * we don't have a custom tap ifconfig template below.
+ */
+static void
+no_tap_ifconfig ()
+{
+  msg (M_FATAL, "Sorry but you cannot use --dev tap and --ifconfig together on this OS because I have not yet been programmed to understand the appropriate ifconfig syntax to use for TAP-style devices on this OS.  Your best alternative is to use an --up script and do the ifconfig command manually.");
+}
+
+/*
+ * Return a string to be used for options compatibility check
+ * between peers.
+ */
+const char *
+ifconfig_options_string (const struct tuntap* tt, bool remote, bool disable, struct gc_arena *gc)
+{
+  struct buffer out = alloc_buf_gc (256, gc);
+  if (tt->did_ifconfig_setup && !disable)
+    {
+      if (tt->type == DEV_TYPE_TUN)
+	{
+	  const char *l, *r;
+	  if (remote)
+	    {
+	      r = print_in_addr_t (tt->local, 0, gc);
+	      l = print_in_addr_t (tt->remote_netmask, 0, gc);
+	    }
+	  else
+	    {
+	      l = print_in_addr_t (tt->local, 0, gc);
+	      r = print_in_addr_t (tt->remote_netmask, 0, gc);
+	    }
+	  buf_printf (&out, "%s %s", r, l);
+	}
+      else if (tt->type == DEV_TYPE_TAP)
+	{
+	  buf_printf (&out, "%s %s",
+		      print_in_addr_t (tt->local & tt->remote_netmask, 0, gc),
+		      print_in_addr_t (tt->remote_netmask, 0, gc));
+	}
+      else
+	buf_printf (&out, "[undef]");
+    }
+  return BSTR (&out);
+}
+
+/*
+ * Return a status string describing wait state.
+ */
+const char *
+tun_stat (const struct tuntap *tt, unsigned int rwflags, struct gc_arena *gc)
+{
+  struct buffer out = alloc_buf_gc (64, gc);
+  if (tt)
+    {
+      if (rwflags & EVENT_READ)
+	{
+	  buf_printf (&out, "T%s",
+		      (tt->rwflags_debug & EVENT_READ) ? "R" : "r");
+#ifdef WIN32
+	  buf_printf (&out, "%s",
+		      overlapped_io_state_ascii (&tt->reads));
+#endif
+	}
+      if (rwflags & EVENT_WRITE)
+	{
+	  buf_printf (&out, "T%s",
+		      (tt->rwflags_debug & EVENT_WRITE) ? "W" : "w");
+#ifdef WIN32
+	  buf_printf (&out, "%s",
+		      overlapped_io_state_ascii (&tt->writes));
+#endif
+	}
+    }
+  else
+    {
+      buf_printf (&out, "T?");
+    }
+  return BSTR (&out);
+}
+
+/*
+ * Init tun/tap object.
+ *
+ * Set up tuntap structure for ifconfig,
+ * but don't execute yet.
+ */
+struct tuntap *
+init_tun (const char *dev,       /* --dev option */
+	  const char *dev_type,  /* --dev-type option */
+	  const char *ifconfig_local_parm,          /* --ifconfig parm 1 */
+	  const char *ifconfig_remote_netmask_parm, /* --ifconfig parm 2 */
+	  in_addr_t local_public,
+	  in_addr_t remote_public,
+	  const bool strict_warn,
+	  struct env_set *es)
+{
+  struct gc_arena gc = gc_new ();
+  struct tuntap *tt;
+
+  ALLOC_OBJ (tt, struct tuntap);
+  clear_tuntap (tt);
+
+  tt->type = dev_type_enum (dev, dev_type);
+
+  if (ifconfig_local_parm && ifconfig_remote_netmask_parm)
+    {
+      bool tun = false;
+      const char *ifconfig_local = NULL;
+      const char *ifconfig_remote_netmask = NULL;
+      const char *ifconfig_broadcast = NULL;
+
+      /*
+       * We only handle TUN/TAP devices here, not --dev null devices.
+       */
+      if (tt->type == DEV_TYPE_TUN)
+	tun = true;
+      else if (tt->type == DEV_TYPE_TAP)
+	tun = false;
+      else
+	msg (M_FATAL, "'%s' is not a TUN/TAP device.  The --ifconfig option works only for TUN/TAP devices.", dev);
+
+      /*
+       * Convert arguments to binary IPv4 addresses.
+       */
+
+      tt->local = getaddr (
+			   GETADDR_RESOLVE
+			   | GETADDR_HOST_ORDER
+			   | GETADDR_FATAL_ON_SIGNAL
+			   | GETADDR_FATAL,
+			   ifconfig_local_parm,
+			   0,
+			   NULL,
+			   NULL);
+
+      tt->remote_netmask = getaddr (
+				    (tun ? GETADDR_RESOLVE : 0)
+				    | GETADDR_HOST_ORDER
+				    | GETADDR_FATAL_ON_SIGNAL
+				    | GETADDR_FATAL,
+				    ifconfig_remote_netmask_parm,
+				    0,
+				    NULL,
+				    NULL);
+
+      /*
+       * Look for common errors in --ifconfig parms
+       */
+      if (strict_warn)
+	{
+	  ifconfig_sanity_check (tun, tt->remote_netmask);
+
+	  /*
+	   * If local_public or remote_public addresses are defined,
+	   * make sure they do not clash with our virtual subnet.
+	   */
+
+	  check_addr_clash ("local",
+			    tt->type,
+			    local_public,
+			    tt->local,
+			    tt->remote_netmask);
+
+	  check_addr_clash ("remote",
+			    tt->type,
+			    remote_public,
+			    tt->local,
+			    tt->remote_netmask);
+	}
+
+      /*
+       * Set ifconfig parameters
+       */
+      ifconfig_local = print_in_addr_t (tt->local, 0, &gc);
+      ifconfig_remote_netmask = print_in_addr_t (tt->remote_netmask, 0, &gc);
+
+      /*
+       * If TAP-style interface, generate broadcast address.
+       */
+      if (!tun)
+	{
+	  tt->broadcast = generate_ifconfig_broadcast_addr (tt->local, tt->remote_netmask);
+	  ifconfig_broadcast = print_in_addr_t (tt->broadcast, 0, &gc);
+	}
+
+      /*
+       * Set environmental variables with ifconfig parameters.
+       */
+      if (es)
+	{
+	  setenv_str (es, "ifconfig_local", ifconfig_local);
+	  if (tun)
+	    {
+	      setenv_str (es, "ifconfig_remote", ifconfig_remote_netmask);
+	    }
+	  else
+	    {
+	      setenv_str (es, "ifconfig_netmask", ifconfig_remote_netmask);
+	      setenv_str (es, "ifconfig_broadcast", ifconfig_broadcast);
+	    }
+	}
+
+      tt->did_ifconfig_setup = true;
+    }
+  gc_free (&gc);
+  return tt;
+}
+
+/*
+ * Platform specific tun initializations
+ */
+void
+init_tun_post (struct tuntap *tt,
+	       const struct frame *frame,
+	       const struct tuntap_options *options)
+{
+  tt->options = *options;
+#ifdef WIN32
+  overlapped_io_init (&tt->reads, frame, FALSE, true);
+  overlapped_io_init (&tt->writes, frame, TRUE, true);
+  tt->rw_handle.read = tt->reads.overlapped.hEvent;
+  tt->rw_handle.write = tt->writes.overlapped.hEvent;
+  tt->adapter_index = ~0;
+#endif
+}
+
+/* execute the ifconfig command through the shell */
+void
+do_ifconfig (struct tuntap *tt,
+	     const char *actual,    /* actual device name */
+	     int tun_mtu,
+	     const struct env_set *es)
+{
+  struct gc_arena gc = gc_new ();
+
+  if (tt->did_ifconfig_setup)
+    {
+      bool tun = false;
+      const char *ifconfig_local = NULL;
+      const char *ifconfig_remote_netmask = NULL;
+      const char *ifconfig_broadcast = NULL;
+      char command_line[256];
+
+      /*
+       * We only handle TUN/TAP devices here, not --dev null devices.
+       */
+      if (tt->type == DEV_TYPE_TUN)
+	tun = true;
+      else if (tt->type == DEV_TYPE_TAP)
+	tun = false;
+      else
+	ASSERT (0); /* should have been caught in init_tun */
+
+      /*
+       * Set ifconfig parameters
+       */
+      ifconfig_local = print_in_addr_t (tt->local, 0, &gc);
+      ifconfig_remote_netmask = print_in_addr_t (tt->remote_netmask, 0, &gc);
+
+      /*
+       * If TAP-style device, generate broadcast address.
+       */
+      if (!tun)
+	ifconfig_broadcast = print_in_addr_t (tt->broadcast, 0, &gc);
+
+#ifdef ENABLE_MANAGEMENT
+  if (management)
+    {
+      management_set_state (management,
+			    OPENVPN_STATE_ASSIGN_IP,
+			    NULL,
+			    tt->local);
+    }
+#endif
+
+
+#if defined(TARGET_LINUX)
+#ifdef CONFIG_FEATURE_IPROUTE
+	/*
+	 * Set the MTU for the device
+	 */
+	openvpn_snprintf (command_line, sizeof (command_line),
+			  IPROUTE_PATH " link set dev %s up mtu %d",
+			  actual,
+			  tun_mtu
+			  );
+	  msg (M_INFO, "%s", command_line);
+	  system_check (command_line, es, S_FATAL, "Linux ip link set failed");
+
+	if (tun) {
+
+		/*
+		 * Set the address for the device
+		 */
+		openvpn_snprintf (command_line, sizeof (command_line),
+				  IPROUTE_PATH " addr add dev %s local %s peer %s",
+				  actual,
+				  ifconfig_local,
+				  ifconfig_remote_netmask
+				  );
+		  msg (M_INFO, "%s", command_line);
+		  system_check (command_line, es, S_FATAL, "Linux ip addr add failed");
+	} else {
+		openvpn_snprintf (command_line, sizeof (command_line),
+				  IPROUTE_PATH " addr add dev %s %s/%d broadcast %s",
+				  actual,
+				  ifconfig_local,
+				  count_netmask_bits(ifconfig_remote_netmask),
+				  ifconfig_broadcast
+				  );
+		  msg (M_INFO, "%s", command_line);
+		  system_check (command_line, es, S_FATAL, "Linux ip addr add failed");
+	}
+	tt->did_ifconfig = true;
+#else
+      if (tun)
+	openvpn_snprintf (command_line, sizeof (command_line),
+			  IFCONFIG_PATH " %s %s pointopoint %s mtu %d",
+			  actual,
+			  ifconfig_local,
+			  ifconfig_remote_netmask,
+			  tun_mtu
+			  );
+      else
+	openvpn_snprintf (command_line, sizeof (command_line),
+			  IFCONFIG_PATH " %s %s netmask %s mtu %d broadcast %s",
+			  actual,
+			  ifconfig_local,
+			  ifconfig_remote_netmask,
+			  tun_mtu,
+			  ifconfig_broadcast
+			  );
+      msg (M_INFO, "%s", command_line);
+      system_check (command_line, es, S_FATAL, "Linux ifconfig failed");
+      tt->did_ifconfig = true;
+
+#endif /*CONFIG_FEATURE_IPROUTE*/
+#elif defined(TARGET_SOLARIS)
+
+      /* Solaris 2.6 (and 7?) cannot set all parameters in one go...
+       * example:
+       *    ifconfig tun2 10.2.0.2 10.2.0.1 mtu 1450 up
+       *    ifconfig tun2 netmask 255.255.255.255
+       */
+      if (tun)
+	{
+	  openvpn_snprintf (command_line, sizeof (command_line),
+			    IFCONFIG_PATH " %s %s %s mtu %d up",
+			    actual,
+			    ifconfig_local,
+			    ifconfig_remote_netmask,
+			    tun_mtu
+			    );
+
+	  msg (M_INFO, "%s", command_line);
+	  if (!system_check (command_line, es, 0, "Solaris ifconfig phase-1 failed"))
+	    solaris_error_close (tt, es, actual);
+
+	  openvpn_snprintf (command_line, sizeof (command_line),
+			    IFCONFIG_PATH " %s netmask 255.255.255.255",
+			    actual
+			    );
+	}
+      else
+	no_tap_ifconfig ();
+
+      msg (M_INFO, "%s", command_line);
+      if (!system_check (command_line, es, 0, "Solaris ifconfig phase-2 failed"))
+	solaris_error_close (tt, es, actual);
+
+      tt->did_ifconfig = true;
+
+#elif defined(TARGET_OPENBSD)
+
+      /*
+       * OpenBSD tun devices appear to be persistent by default.  It seems in order
+       * to make this work correctly, we need to delete the previous instance
+       * (if it exists), and re-ifconfig.  Let me know if you know a better way.
+       */
+
+      openvpn_snprintf (command_line, sizeof (command_line),
+			IFCONFIG_PATH " %s destroy",
+			actual);
+      msg (M_INFO, "%s", command_line);
+      system_check (command_line, es, 0, NULL);
+      openvpn_snprintf (command_line, sizeof (command_line),
+			IFCONFIG_PATH " %s create",
+			actual);
+      msg (M_INFO, "%s", command_line);
+      system_check (command_line, es, 0, NULL);
+      msg (M_INFO, "NOTE: Tried to delete pre-existing tun/tap instance -- No Problem if failure");
+
+      /* example: ifconfig tun2 10.2.0.2 10.2.0.1 mtu 1450 netmask 255.255.255.255 up */
+      if (tun)
+	openvpn_snprintf (command_line, sizeof (command_line),
+			  IFCONFIG_PATH " %s %s %s mtu %d netmask 255.255.255.255 up",
+			  actual,
+			  ifconfig_local,
+			  ifconfig_remote_netmask,
+			  tun_mtu
+			  );
+      else
+	openvpn_snprintf (command_line, sizeof (command_line),
+			  IFCONFIG_PATH " %s %s netmask %s mtu %d broadcast %s link0",
+			  actual,
+			  ifconfig_local,
+			  ifconfig_remote_netmask,
+			  tun_mtu,
+			  ifconfig_broadcast
+			  );
+      msg (M_INFO, "%s", command_line);
+      system_check (command_line, es, S_FATAL, "OpenBSD ifconfig failed");
+      tt->did_ifconfig = true;
+
+#elif defined(TARGET_NETBSD)
+
+      if (tun)
+	openvpn_snprintf (command_line, sizeof (command_line),
+			  IFCONFIG_PATH " %s %s %s mtu %d netmask 255.255.255.255 up",
+			  actual,
+			  ifconfig_local,
+			  ifconfig_remote_netmask,
+			  tun_mtu
+			  );
+      else
+	no_tap_ifconfig ();
+      msg (M_INFO, "%s", command_line);
+      system_check (command_line, es, S_FATAL, "NetBSD ifconfig failed");
+      tt->did_ifconfig = true;
+
+#elif defined(TARGET_DARWIN)
+
+      /*
+       * Darwin (i.e. Mac OS X) seems to exhibit similar behaviour to OpenBSD...
+       */
+
+      openvpn_snprintf (command_line, sizeof (command_line),
+			IFCONFIG_PATH " %s delete",
+			actual);
+      msg (M_INFO, "%s", command_line);
+      system_check (command_line, es, 0, NULL);
+      msg (M_INFO, "NOTE: Tried to delete pre-existing tun/tap instance -- No Problem if failure");
+
+
+      /* example: ifconfig tun2 10.2.0.2 10.2.0.1 mtu 1450 netmask 255.255.255.255 up */
+      if (tun)
+	openvpn_snprintf (command_line, sizeof (command_line),
+			  IFCONFIG_PATH " %s %s %s mtu %d netmask 255.255.255.255 up",
+			  actual,
+			  ifconfig_local,
+			  ifconfig_remote_netmask,
+			  tun_mtu
+			  );
+      else
+	openvpn_snprintf (command_line, sizeof (command_line),
+			  IFCONFIG_PATH " %s %s netmask %s mtu %d up",
+			  actual,
+			  ifconfig_local,
+			  ifconfig_remote_netmask,
+			  tun_mtu
+			  );
+
+      msg (M_INFO, "%s", command_line);
+      system_check (command_line, es, S_FATAL, "Mac OS X ifconfig failed");
+      tt->did_ifconfig = true;
+
+#elif defined(TARGET_FREEBSD)
+
+      /* example: ifconfig tun2 10.2.0.2 10.2.0.1 mtu 1450 netmask 255.255.255.255 up */
+      if (tun)
+	openvpn_snprintf (command_line, sizeof (command_line),
+			  IFCONFIG_PATH " %s %s %s mtu %d netmask 255.255.255.255 up",
+			  actual,
+			  ifconfig_local,
+			  ifconfig_remote_netmask,
+			  tun_mtu
+			  );
+      else
+	openvpn_snprintf (command_line, sizeof (command_line),
+			  IFCONFIG_PATH " %s %s netmask %s mtu %d up",
+			  actual,
+			  ifconfig_local,
+			  ifconfig_remote_netmask,
+			  tun_mtu
+			  );
+	
+      msg (M_INFO, "%s", command_line);
+      system_check (command_line, es, S_FATAL, "FreeBSD ifconfig failed");
+      tt->did_ifconfig = true;
+
+#elif defined (WIN32)
+      {
+	const char *netmask;
+
+	/*
+	 * Make sure that both ifconfig addresses are part of the
+	 * same .252 subnet.
+	 */
+	if (tun)
+	  {
+	    verify_255_255_255_252 (tt->local, tt->remote_netmask);
+	    tt->adapter_netmask = ~3;
+	    netmask = print_in_addr_t (tt->adapter_netmask, 0, &gc);
+	  }
+	else
+	  {
+	    netmask = ifconfig_remote_netmask;
+	    tt->adapter_netmask = tt->remote_netmask;
+	  }
+
+	/* example: netsh interface ip set address my-tap static 10.3.0.1 255.255.255.0 */
+	openvpn_snprintf (command_line, sizeof (command_line),
+			  "netsh interface ip set address \"%s\" static %s %s",
+			  actual,
+			  ifconfig_local,
+			  netmask);
+	
+	switch (tt->options.ip_win32_type)
+	  {
+	  case IPW32_SET_MANUAL:
+	    msg (M_INFO, "******** NOTE:  Please manually set the IP/netmask of '%s' to %s/%s (if it is not already set)",
+		 actual,
+		 ifconfig_local,
+		 netmask);
+	    break;
+	  case IPW32_SET_NETSH:
+	    if (!strcmp (actual, "NULL"))
+	      msg (M_FATAL, "Error: When using --ip-win32 netsh, if you have more than one TAP-Win32 adapter, you must also specify --dev-node");
+	    netcmd_semaphore_lock ();
+	    msg (M_INFO, "%s", command_line);
+	    system_check (command_line, es, S_FATAL, "ERROR: netsh command failed");
+	    netcmd_semaphore_release ();
+	    break;
+	  }
+	tt->did_ifconfig = true;
+      }
+
+#else
+      msg (M_FATAL, "Sorry, but I don't know how to do 'ifconfig' commands on this operating system.  You should ifconfig your TUN/TAP device manually or use an --up script.");
+#endif
+    }
+  gc_free (&gc);
+}
+
+void
+clear_tuntap (struct tuntap *tuntap)
+{
+  CLEAR (*tuntap);
+#ifdef WIN32
+  tuntap->hand = NULL;
+#else
+  tuntap->fd = -1;
+#endif
+#ifdef TARGET_SOLARIS
+  tuntap->ip_fd = -1;
+#endif
+  tuntap->ipv6 = false;
+}
+
+static void
+open_null (struct tuntap *tt)
+{
+  tt->actual_name = string_alloc ("null", NULL);
+}
+
+#ifndef WIN32
+static void
+open_tun_generic (const char *dev, const char *dev_type, const char *dev_node,
+		  bool ipv6, bool ipv6_explicitly_supported, bool dynamic,
+		  struct tuntap *tt)
+{
+  char tunname[256];
+  char dynamic_name[256];
+  bool dynamic_opened = false;
+
+  ipv6_support (ipv6, ipv6_explicitly_supported, tt);
+
+  if (tt->type == DEV_TYPE_NULL)
+    {
+      open_null (tt);
+    }
+  else
+    {
+      /*
+       * --dev-node specified, so open an explicit device node
+       */
+      if (dev_node)
+	{
+	  openvpn_snprintf (tunname, sizeof (tunname), "%s", dev_node);
+	}
+      else
+	{
+	  /*
+	   * dynamic open is indicated by --dev specified without
+	   * explicit unit number.  Try opening /dev/[dev]n
+	   * where n = [0, 255].
+	   */
+	  if (dynamic && !has_digit(dev))
+	    {
+	      int i;
+	      for (i = 0; i < 256; ++i)
+		{
+		  openvpn_snprintf (tunname, sizeof (tunname),
+				    "/dev/%s%d", dev, i);
+		  openvpn_snprintf (dynamic_name, sizeof (dynamic_name),
+				    "%s%d", dev, i);
+		  if ((tt->fd = open (tunname, O_RDWR)) > 0)
+		    {
+		      dynamic_opened = true;
+		      break;
+		    }
+		  msg (D_READ_WRITE | M_ERRNO, "Tried opening %s (failed)", tunname);
+		}
+	      if (!dynamic_opened)
+		msg (M_FATAL, "Cannot allocate TUN/TAP dev dynamically");
+	    }
+	  /*
+	   * explicit unit number specified
+	   */
+	  else
+	    {
+	      openvpn_snprintf (tunname, sizeof (tunname), "/dev/%s", dev);
+	    }
+	}
+
+      if (!dynamic_opened)
+	{
+	  if ((tt->fd = open (tunname, O_RDWR)) < 0)
+	    msg (M_ERR, "Cannot open TUN/TAP dev %s", tunname);
+	}
+
+      set_nonblock (tt->fd);
+      set_cloexec (tt->fd); /* don't pass fd to scripts */
+      msg (M_INFO, "TUN/TAP device %s opened", tunname);
+
+      /* tt->actual_name is passed to up and down scripts and used as the ifconfig dev name */
+      tt->actual_name = string_alloc (dynamic_opened ? dynamic_name : dev, NULL);
+    }
+}
+
+static void
+close_tun_generic (struct tuntap *tt)
+{
+  if (tt->fd >= 0)
+    close (tt->fd);
+  if (tt->actual_name)
+    free (tt->actual_name);
+  clear_tuntap (tt);
+}
+
+#endif
+
+#if defined(TARGET_LINUX)
+
+#ifdef HAVE_LINUX_IF_TUN_H	/* New driver support */
+
+#ifndef HAVE_LINUX_SOCKIOS_H
+#error header file linux/sockios.h required
+#endif
+
+#if defined(HAVE_TUN_PI) && defined(HAVE_IPHDR) && defined(HAVE_IOVEC) && defined(ETH_P_IPV6) && defined(ETH_P_IP) && defined(HAVE_READV) && defined(HAVE_WRITEV)
+#define LINUX_IPV6 1
+/* #warning IPv6 ON */
+#else
+#define LINUX_IPV6 0
+/* #warning IPv6 OFF */
+#endif
+
+#if !PEDANTIC
+
+void
+open_tun (const char *dev, const char *dev_type, const char *dev_node, bool ipv6, struct tuntap *tt)
+{
+  struct ifreq ifr;
+
+  /*
+   * Set tt->ipv6 to true if
+   * (a) we have the capability of supporting --tun-ipv6, and
+   * (b) --tun-ipv6 was specified.
+   */
+  ipv6_support (ipv6, LINUX_IPV6, tt);
+
+  /*
+   * We handle --dev null specially, we do not open /dev/null for this.
+   */
+  if (tt->type == DEV_TYPE_NULL)
+    {
+      open_null (tt);
+    }
+  else
+    {
+      /*
+       * Process --dev-node
+       */
+      const char *node = dev_node;
+      if (!node)
+	node = "/dev/net/tun";
+
+      /*
+       * Open the interface
+       */
+      if ((tt->fd = open (node, O_RDWR)) < 0)
+	{
+	  msg (M_WARN | M_ERRNO, "Note: Cannot open TUN/TAP dev %s", node);
+	  goto linux_2_2_fallback;
+	}
+
+      /*
+       * Process --tun-ipv6
+       */
+      CLEAR (ifr);
+      if (!tt->ipv6)
+	ifr.ifr_flags = IFF_NO_PI;
+
+#if defined(IFF_ONE_QUEUE) && defined(SIOCSIFTXQLEN)
+      ifr.ifr_flags |= IFF_ONE_QUEUE;
+#endif
+
+      /*
+       * Figure out if tun or tap device
+       */
+      if (tt->type == DEV_TYPE_TUN)
+	{
+	  ifr.ifr_flags |= IFF_TUN;
+	}
+      else if (tt->type == DEV_TYPE_TAP)
+	{
+	  ifr.ifr_flags |= IFF_TAP;
+	}
+      else
+	{
+	  msg (M_FATAL, "I don't recognize device %s as a tun or tap device",
+	       dev);
+	}
+
+      /*
+       * Set an explicit name, if --dev is not tun or tap
+       */
+      if (strcmp(dev, "tun") && strcmp(dev, "tap"))
+	strncpynt (ifr.ifr_name, dev, IFNAMSIZ);
+
+      /*
+       * Use special ioctl that configures tun/tap device with the parms
+       * we set in ifr
+       */
+      if (ioctl (tt->fd, TUNSETIFF, (void *) &ifr) < 0)
+	{
+	  msg (M_WARN | M_ERRNO, "Note: Cannot ioctl TUNSETIFF %s", dev);
+	  goto linux_2_2_fallback;
+	}
+
+      msg (M_INFO, "TUN/TAP device %s opened", ifr.ifr_name);
+
+      /*
+       * Try making the TX send queue bigger
+       */
+#if defined(IFF_ONE_QUEUE) && defined(SIOCSIFTXQLEN)
+      {
+	struct ifreq netifr;
+	int ctl_fd;
+
+	if ((ctl_fd = socket (AF_INET, SOCK_DGRAM, 0)) >= 0)
+	  {
+	    CLEAR (netifr);
+	    strncpynt (netifr.ifr_name, ifr.ifr_name, IFNAMSIZ);
+	    netifr.ifr_qlen = tt->options.txqueuelen;
+	    if (ioctl (ctl_fd, SIOCSIFTXQLEN, (void *) &netifr) >= 0)
+	      msg (D_OSBUF, "TUN/TAP TX queue length set to %d", tt->options.txqueuelen);
+	    else
+	      msg (M_WARN | M_ERRNO, "Note: Cannot set tx queue length on %s", ifr.ifr_name);
+	    close (ctl_fd);
+	  }
+	else
+	  {
+	    msg (M_WARN | M_ERRNO, "Note: Cannot open control socket on %s", ifr.ifr_name);
+	  }
+      }
+#endif
+
+      set_nonblock (tt->fd);
+      set_cloexec (tt->fd);
+      tt->actual_name = string_alloc (ifr.ifr_name, NULL);
+    }
+  return;
+
+ linux_2_2_fallback:
+  msg (M_INFO, "Note: Attempting fallback to kernel 2.2 TUN/TAP interface");
+  if (tt->fd >= 0)
+    {
+      close (tt->fd);
+      tt->fd = -1;
+    }
+  open_tun_generic (dev, dev_type, dev_node, ipv6, false, true, tt);
+}
+
+#else
+
+void
+open_tun (const char *dev, const char *dev_type, const char *dev_node, bool ipv6, struct tuntap *tt)
+{
+  ASSERT (0);
+}
+
+#endif
+
+#else
+
+void
+open_tun (const char *dev, const char *dev_type, const char *dev_node, bool ipv6, struct tuntap *tt)
+{
+  open_tun_generic (dev, dev_type, dev_node, ipv6, false, true, tt);
+}
+
+#endif /* HAVE_LINUX_IF_TUN_H */
+
+#ifdef TUNSETPERSIST
+
+void
+tuncfg (const char *dev, const char *dev_type, const char *dev_node, bool ipv6, int persist_mode)
+{
+  struct tuntap *tt;
+
+  ALLOC_OBJ (tt, struct tuntap);
+  clear_tuntap (tt);
+  tt->type = dev_type_enum (dev, dev_type);
+  open_tun (dev, dev_type, dev_node, ipv6, tt);
+  if (ioctl (tt->fd, TUNSETPERSIST, persist_mode) < 0)
+    msg (M_ERR, "Cannot ioctl TUNSETPERSIST(%d) %s", persist_mode, dev);
+  close_tun (tt);
+  msg (M_INFO, "Persist state set to: %s", (persist_mode ? "ON" : "OFF"));
+}
+
+#endif /* TUNSETPERSIST */
+
+void
+close_tun (struct tuntap *tt)
+{
+  if (tt)
+    {
+      close_tun_generic (tt);
+      free (tt);
+    }
+}
+
+int
+write_tun (struct tuntap* tt, uint8_t *buf, int len)
+{
+#if LINUX_IPV6
+  if (tt->ipv6)
+    {
+      struct tun_pi pi;
+      struct iphdr *iph;
+      struct iovec vect[2];
+      int ret;
+
+      iph = (struct iphdr *)buf;
+
+      pi.flags = 0;
+
+      if(iph->version == 6)
+	pi.proto = htons(ETH_P_IPV6);
+      else
+	pi.proto = htons(ETH_P_IP);
+
+      vect[0].iov_len = sizeof(pi);
+      vect[0].iov_base = &pi;
+      vect[1].iov_len = len;
+      vect[1].iov_base = buf;
+
+      ret = writev(tt->fd, vect, 2);
+      return(ret - sizeof(pi));
+    }
+  else
+#endif
+    return write (tt->fd, buf, len);
+}
+
+int
+read_tun (struct tuntap* tt, uint8_t *buf, int len)
+{
+#if LINUX_IPV6
+  if (tt->ipv6)
+    {
+      struct iovec vect[2];
+      struct tun_pi pi;
+      int ret;
+
+      vect[0].iov_len = sizeof(pi);
+      vect[0].iov_base = &pi;
+      vect[1].iov_len = len;
+      vect[1].iov_base = buf;
+
+      ret = readv(tt->fd, vect, 2);
+      return(ret - sizeof(pi));
+    }
+  else
+#endif
+    return read (tt->fd, buf, len);
+}
+
+#elif defined(TARGET_SOLARIS)
+
+#ifndef TUNNEWPPA
+#error I need the symbol TUNNEWPPA from net/if_tun.h
+#endif
+
+void
+open_tun (const char *dev, const char *dev_type, const char *dev_node, bool ipv6, struct tuntap *tt)
+{
+  int if_fd, muxid, ppa = -1;
+  struct ifreq ifr;
+  const char *ptr;
+  const char *ip_node;
+  const char *dev_tuntap_type;
+  int link_type;
+  bool is_tun;
+
+  ipv6_support (ipv6, false, tt);
+
+  if (tt->type == DEV_TYPE_NULL)
+    {
+      open_null (tt);
+      return;
+    }
+
+  if (tt->type == DEV_TYPE_TUN)
+    {
+      ip_node = "/dev/udp";
+      if (!dev_node)
+	dev_node = "/dev/tun";
+      dev_tuntap_type = "tun";
+      link_type = I_PLINK;
+      is_tun = true;
+    }
+  else if (tt->type == DEV_TYPE_TAP)
+    {
+      ip_node = "/dev/ip";
+      if (!dev_node)
+	dev_node = "/dev/tap";
+      dev_tuntap_type = "tap";
+      link_type = I_PLINK; /* was: I_LINK */
+      is_tun = false;
+    }
+  else
+    {
+      msg (M_FATAL, "I don't recognize device %s as a tun or tap device",
+	   dev);
+    }
+  
+  /* get unit number */
+  if (*dev)
+    {
+      ptr = dev;
+      while (*ptr && !isdigit ((int) *ptr))
+	ptr++;
+      ppa = atoi (ptr);
+    }
+
+  if ((tt->ip_fd = open (ip_node, O_RDWR, 0)) < 0)
+    msg (M_ERR, "Can't open %s", ip_node);
+
+  if ((tt->fd = open (dev_node, O_RDWR, 0)) < 0)
+    msg (M_ERR, "Can't open %s", dev_node);
+
+  /* Assign a new PPA and get its unit number. */
+  if ((ppa = ioctl (tt->fd, TUNNEWPPA, ppa)) < 0)
+    msg (M_ERR, "Can't assign new interface");
+
+  if ((if_fd = open (dev_node, O_RDWR, 0)) < 0)
+    msg (M_ERR, "Can't open %s (2)", dev_node);
+
+  if (ioctl (if_fd, I_PUSH, "ip") < 0)
+    msg (M_ERR, "Can't push IP module");
+
+  /* Assign ppa according to the unit number returned by tun device */
+  if (ioctl (if_fd, IF_UNITSEL, (char *) &ppa) < 0)
+    msg (M_ERR, "Can't set PPA %d", ppa);
+
+  if ((muxid = ioctl (tt->ip_fd, link_type, if_fd)) < 0)
+    msg (M_ERR, "Can't link %s device to IP", dev_tuntap_type);
+
+  close (if_fd);
+
+  tt->actual_name = (char *) malloc (32);
+  check_malloc_return (tt->actual_name);
+
+  openvpn_snprintf (tt->actual_name, 32, "%s%d", dev_tuntap_type, ppa);
+
+  CLEAR (ifr);
+  strncpynt (ifr.ifr_name, tt->actual_name, sizeof (ifr.ifr_name));
+  ifr.ifr_ip_muxid = muxid;
+
+  if (ioctl (tt->ip_fd, SIOCSIFMUXID, &ifr) < 0)
+    {
+      ioctl (tt->ip_fd, I_PUNLINK, muxid);
+      msg (M_ERR, "Can't set multiplexor id");
+    }
+
+  set_nonblock (tt->fd);
+  set_cloexec (tt->fd);
+  set_cloexec (tt->ip_fd);
+
+  msg (M_INFO, "TUN/TAP device %s opened", tt->actual_name);
+}
+
+static void
+solaris_close_tun (struct tuntap *tt)
+{
+  if (tt)
+    {
+      if (tt->ip_fd >= 0)
+	{
+	  struct ifreq ifr;
+	  CLEAR (ifr);
+	  strncpynt (ifr.ifr_name, tt->actual_name, sizeof (ifr.ifr_name));
+
+	  if (ioctl (tt->ip_fd, SIOCGIFFLAGS, &ifr) < 0)
+	    msg (M_WARN | M_ERRNO, "Can't get iface flags");
+
+	  if (ioctl (tt->ip_fd, SIOCGIFMUXID, &ifr) < 0)
+	    msg (M_WARN | M_ERRNO, "Can't get multiplexor id");
+
+	  if (ioctl (tt->ip_fd, I_PUNLINK, ifr.ifr_ip_muxid) < 0)
+	    msg (M_WARN | M_ERRNO, "Can't unlink interface");
+
+	  close (tt->ip_fd);
+	  tt->ip_fd = -1;
+	}
+
+      if (tt->fd >= 0)
+	{
+	  close (tt->fd);
+	  tt->fd = -1;
+	}
+    }
+}
+
+/*
+ * Close TUN device. 
+ */
+void
+close_tun (struct tuntap *tt)
+{
+  if (tt)
+    {
+      solaris_close_tun (tt);
+
+      if (tt->actual_name)
+	free (tt->actual_name);
+      
+      clear_tuntap (tt);
+      free (tt);
+    }
+}
+
+static void
+solaris_error_close (struct tuntap *tt, const struct env_set *es, const char *actual)
+{
+  char command_line[256];
+
+  openvpn_snprintf (command_line, sizeof (command_line),
+		    IFCONFIG_PATH " %s unplumb",
+		    actual);
+
+  msg (M_INFO, "%s", command_line);
+  system_check (command_line, es, 0, "Solaris ifconfig unplumb failed");
+  close_tun (tt);
+  msg (M_FATAL, "Solaris ifconfig failed");
+}
+
+int
+write_tun (struct tuntap* tt, uint8_t *buf, int len)
+{
+  struct strbuf sbuf;
+  sbuf.len = len;
+  sbuf.buf = (char *)buf;
+  return putmsg (tt->fd, NULL, &sbuf, 0) >= 0 ? sbuf.len : -1;
+}
+
+int
+read_tun (struct tuntap* tt, uint8_t *buf, int len)
+{
+  struct strbuf sbuf;
+  int f = 0;
+
+  sbuf.maxlen = len;
+  sbuf.buf = (char *)buf;
+  return getmsg (tt->fd, NULL, &sbuf, &f) >= 0 ? sbuf.len : -1;
+}
+
+#elif defined(TARGET_OPENBSD)
+
+#if !defined(HAVE_READV) || !defined(HAVE_WRITEV)
+#error openbsd build requires readv & writev library functions
+#endif
+
+/*
+ * OpenBSD has a slightly incompatible TUN device from
+ * the rest of the world, in that it prepends a
+ * uint32 to the beginning of the IP header
+ * to designate the protocol (why not just
+ * look at the version field in the IP header to
+ * determine v4 or v6?).
+ *
+ * We strip off this field on reads and
+ * put it back on writes.
+ *
+ * I have not tested TAP devices on OpenBSD,
+ * but I have conditionalized the special
+ * TUN handling code described above to
+ * go away for TAP devices.
+ */
+
+void
+open_tun (const char *dev, const char *dev_type, const char *dev_node, bool ipv6, struct tuntap *tt)
+{
+  open_tun_generic (dev, dev_type, dev_node, ipv6, true, true, tt);
+
+  /* Enable multicast on the interface */
+  if (tt->fd >= 0)
+    {
+      struct tuninfo info;
+
+      if (ioctl (tt->fd, TUNGIFINFO, &info) < 0) {
+	msg (M_WARN | M_ERRNO, "Can't get interface info: %s",
+	  strerror(errno));
+      }
+
+      info.flags |= IFF_MULTICAST;
+
+      if (ioctl (tt->fd, TUNSIFINFO, &info) < 0) {
+	msg (M_WARN | M_ERRNO, "Can't set interface info: %s",
+	  strerror(errno));
+      }
+    }
+}
+
+void
+close_tun (struct tuntap* tt)
+{
+  if (tt)
+    {
+      close_tun_generic (tt);
+      free (tt);
+    }
+}
+
+static inline int
+openbsd_modify_read_write_return (int len)
+{
+ if (len > 0)
+    return len > sizeof (u_int32_t) ? len - sizeof (u_int32_t) : 0;
+  else
+    return len;
+}
+
+int
+write_tun (struct tuntap* tt, uint8_t *buf, int len)
+{
+  if (tt->type == DEV_TYPE_TUN)
+    {
+      u_int32_t type;
+      struct iovec iv[2];
+      struct ip *iph;
+
+      iph = (struct ip *) buf;
+
+      if (tt->ipv6 && iph->ip_v == 6)
+	type = htonl (AF_INET6);
+      else 
+	type = htonl (AF_INET);
+
+      iv[0].iov_base = &type;
+      iv[0].iov_len = sizeof (type);
+      iv[1].iov_base = buf;
+      iv[1].iov_len = len;
+
+      return openbsd_modify_read_write_return (writev (tt->fd, iv, 2));
+    }
+  else
+    return write (tt->fd, buf, len);
+}
+
+int
+read_tun (struct tuntap* tt, uint8_t *buf, int len)
+{
+  if (tt->type == DEV_TYPE_TUN)
+    {
+      u_int32_t type;
+      struct iovec iv[2];
+
+      iv[0].iov_base = &type;
+      iv[0].iov_len = sizeof (type);
+      iv[1].iov_base = buf;
+      iv[1].iov_len = len;
+
+      return openbsd_modify_read_write_return (readv (tt->fd, iv, 2));
+    }
+  else
+    return read (tt->fd, buf, len);
+}
+
+#elif defined(TARGET_NETBSD)
+
+/*
+ * NetBSD does not support IPv6 on tun out of the box,
+ * but there exists a patch. When this patch is applied,
+ * only two things are left to openvpn:
+ * 1. Activate multicasting (this has already been done
+ *    before by the kernel, but we make sure that nobody
+ *    has deactivated multicasting inbetween.
+ * 2. Deactivate "link layer mode" (otherwise NetBSD 
+ *    prepends the address family to the packet, and we
+ *    would run into the same trouble as with OpenBSD.
+ */
+
+void
+open_tun (const char *dev, const char *dev_type, const char *dev_node, bool ipv6, struct tuntap *tt)
+{
+    open_tun_generic (dev, dev_type, dev_node, ipv6, true, true, tt);
+    if (tt->fd >= 0)
+      {
+        int i = IFF_POINTOPOINT|IFF_MULTICAST;
+        ioctl (tt->fd, TUNSIFMODE, &i);  /* multicast on */
+        i = 0;
+        ioctl (tt->fd, TUNSLMODE, &i);   /* link layer mode off */
+      }
+}
+
+void
+close_tun (struct tuntap *tt)
+{
+  if (tt)
+    {
+      close_tun_generic (tt);
+      free (tt);
+    }
+}
+
+int
+write_tun (struct tuntap* tt, uint8_t *buf, int len)
+{
+    return write (tt->fd, buf, len);
+}
+
+int
+read_tun (struct tuntap* tt, uint8_t *buf, int len)
+{
+    return read (tt->fd, buf, len);
+}
+
+#elif defined(TARGET_FREEBSD)
+
+static inline int
+freebsd_modify_read_write_return (int len)
+{
+  if (len > 0)
+    return len > sizeof (u_int32_t) ? len - sizeof (u_int32_t) : 0;
+  else
+    return len;
+}
+
+void
+open_tun (const char *dev, const char *dev_type, const char *dev_node, bool ipv6, struct tuntap *tt)
+{
+  open_tun_generic (dev, dev_type, dev_node, ipv6, true, true, tt);
+
+  if (tt->fd >= 0)
+    {
+      int i = 0;
+
+      /* Disable extended modes */
+      ioctl (tt->fd, TUNSLMODE, &i);
+      i = 1;
+      ioctl (tt->fd, TUNSIFHEAD, &i);
+    }
+}
+
+void
+close_tun (struct tuntap *tt)
+{
+  if (tt)
+    {
+      close_tun_generic (tt);
+      free (tt);
+    }
+}
+
+int
+write_tun (struct tuntap* tt, uint8_t *buf, int len)
+{
+  if (tt->type == DEV_TYPE_TUN)
+    {
+      u_int32_t type;
+      struct iovec iv[2];
+      struct ip *iph;
+
+      iph = (struct ip *) buf;
+
+      if (tt->ipv6 && iph->ip_v == 6)
+        type = htonl (AF_INET6);
+      else 
+        type = htonl (AF_INET);
+
+      iv[0].iov_base = (char *)&type;
+      iv[0].iov_len = sizeof (type);
+      iv[1].iov_base = buf;
+      iv[1].iov_len = len;
+
+      return freebsd_modify_read_write_return (writev (tt->fd, iv, 2));
+    }
+  else
+    return write (tt->fd, buf, len);
+}
+
+int
+read_tun (struct tuntap* tt, uint8_t *buf, int len)
+{
+  if (tt->type == DEV_TYPE_TUN)
+    {
+      u_int32_t type;
+      struct iovec iv[2];
+
+      iv[0].iov_base = (char *)&type;
+      iv[0].iov_len = sizeof (type);
+      iv[1].iov_base = buf;
+      iv[1].iov_len = len;
+
+      return freebsd_modify_read_write_return (readv (tt->fd, iv, 2));
+    }
+  else
+    return read (tt->fd, buf, len);
+}
+
+#elif defined(WIN32)
+
+int
+tun_read_queue (struct tuntap *tt, int maxsize)
+{
+  if (tt->reads.iostate == IOSTATE_INITIAL)
+    {
+      DWORD len;
+      BOOL status;
+      int err;
+
+      /* reset buf to its initial state */
+      tt->reads.buf = tt->reads.buf_init;
+
+      len = maxsize ? maxsize : BLEN (&tt->reads.buf);
+      ASSERT (len <= BLEN (&tt->reads.buf));
+
+      /* the overlapped read will signal this event on I/O completion */
+      ASSERT (ResetEvent (tt->reads.overlapped.hEvent));
+
+      status = ReadFile(
+		      tt->hand,
+		      BPTR (&tt->reads.buf),
+		      len,
+		      &tt->reads.size,
+		      &tt->reads.overlapped
+		      );
+
+      if (status) /* operation completed immediately? */
+	{
+	  /* since we got an immediate return, we must signal the event object ourselves */
+	  ASSERT (SetEvent (tt->reads.overlapped.hEvent));
+
+	  tt->reads.iostate = IOSTATE_IMMEDIATE_RETURN;
+	  tt->reads.status = 0;
+
+	  dmsg (D_WIN32_IO, "WIN32 I/O: TAP Read immediate return [%d,%d]",
+	       (int) len,
+	       (int) tt->reads.size);	       
+	}
+      else
+	{
+	  err = GetLastError (); 
+	  if (err == ERROR_IO_PENDING) /* operation queued? */
+	    {
+	      tt->reads.iostate = IOSTATE_QUEUED;
+	      tt->reads.status = err;
+	      dmsg (D_WIN32_IO, "WIN32 I/O: TAP Read queued [%d]",
+		   (int) len);
+	    }
+	  else /* error occurred */
+	    {
+	      struct gc_arena gc = gc_new ();
+	      ASSERT (SetEvent (tt->reads.overlapped.hEvent));
+	      tt->reads.iostate = IOSTATE_IMMEDIATE_RETURN;
+	      tt->reads.status = err;
+	      dmsg (D_WIN32_IO, "WIN32 I/O: TAP Read error [%d] : %s",
+		   (int) len,
+		   strerror_win32 (status, &gc));
+	      gc_free (&gc);
+	    }
+	}
+    }
+  return tt->reads.iostate;
+}
+
+int
+tun_write_queue (struct tuntap *tt, struct buffer *buf)
+{
+  if (tt->writes.iostate == IOSTATE_INITIAL)
+    {
+      BOOL status;
+      int err;
+ 
+      /* make a private copy of buf */
+      tt->writes.buf = tt->writes.buf_init;
+      tt->writes.buf.len = 0;
+      ASSERT (buf_copy (&tt->writes.buf, buf));
+
+      /* the overlapped write will signal this event on I/O completion */
+      ASSERT (ResetEvent (tt->writes.overlapped.hEvent));
+
+      status = WriteFile(
+			tt->hand,
+			BPTR (&tt->writes.buf),
+			BLEN (&tt->writes.buf),
+			&tt->writes.size,
+			&tt->writes.overlapped
+			);
+
+      if (status) /* operation completed immediately? */
+	{
+	  tt->writes.iostate = IOSTATE_IMMEDIATE_RETURN;
+
+	  /* since we got an immediate return, we must signal the event object ourselves */
+	  ASSERT (SetEvent (tt->writes.overlapped.hEvent));
+
+	  tt->writes.status = 0;
+
+	  dmsg (D_WIN32_IO, "WIN32 I/O: TAP Write immediate return [%d,%d]",
+	       BLEN (&tt->writes.buf),
+	       (int) tt->writes.size);	       
+	}
+      else
+	{
+	  err = GetLastError (); 
+	  if (err == ERROR_IO_PENDING) /* operation queued? */
+	    {
+	      tt->writes.iostate = IOSTATE_QUEUED;
+	      tt->writes.status = err;
+	      dmsg (D_WIN32_IO, "WIN32 I/O: TAP Write queued [%d]",
+		   BLEN (&tt->writes.buf));
+	    }
+	  else /* error occurred */
+	    {
+	      struct gc_arena gc = gc_new ();
+	      ASSERT (SetEvent (tt->writes.overlapped.hEvent));
+	      tt->writes.iostate = IOSTATE_IMMEDIATE_RETURN;
+	      tt->writes.status = err;
+	      dmsg (D_WIN32_IO, "WIN32 I/O: TAP Write error [%d] : %s",
+		   BLEN (&tt->writes.buf),
+		   strerror_win32 (err, &gc));
+	      gc_free (&gc);
+	    }
+	}
+    }
+  return tt->writes.iostate;
+}
+
+int
+tun_finalize (
+	      HANDLE h,
+	      struct overlapped_io *io,
+	      struct buffer *buf)
+{
+  int ret = -1;
+  BOOL status;
+
+  switch (io->iostate)
+    {
+    case IOSTATE_QUEUED:
+      status = GetOverlappedResult(
+				   h,
+				   &io->overlapped,
+				   &io->size,
+				   FALSE
+				   );
+      if (status)
+	{
+	  /* successful return for a queued operation */
+	  if (buf)
+	    *buf = io->buf;
+	  ret = io->size;
+	  io->iostate = IOSTATE_INITIAL;
+	  ASSERT (ResetEvent (io->overlapped.hEvent));
+	  dmsg (D_WIN32_IO, "WIN32 I/O: TAP Completion success [%d]", ret);
+	}
+      else
+	{
+	  /* error during a queued operation */
+	  ret = -1;
+	  if (GetLastError() != ERROR_IO_INCOMPLETE)
+	    {
+	      /* if no error (i.e. just not finished yet),
+		 then DON'T execute this code */
+	      io->iostate = IOSTATE_INITIAL;
+	      ASSERT (ResetEvent (io->overlapped.hEvent));
+	      msg (D_WIN32_IO | M_ERRNO, "WIN32 I/O: TAP Completion error");
+	    }
+	}
+      break;
+
+    case IOSTATE_IMMEDIATE_RETURN:
+      io->iostate = IOSTATE_INITIAL;
+      ASSERT (ResetEvent (io->overlapped.hEvent));
+      if (io->status)
+	{
+	  /* error return for a non-queued operation */
+	  SetLastError (io->status);
+	  ret = -1;
+	  msg (D_WIN32_IO | M_ERRNO, "WIN32 I/O: TAP Completion non-queued error");
+	}
+      else
+	{
+	  /* successful return for a non-queued operation */
+	  if (buf)
+	    *buf = io->buf;
+	  ret = io->size;
+	  dmsg (D_WIN32_IO, "WIN32 I/O: TAP Completion non-queued success [%d]", ret);
+	}
+      break;
+
+    case IOSTATE_INITIAL: /* were we called without proper queueing? */
+      SetLastError (ERROR_INVALID_FUNCTION);
+      ret = -1;
+      dmsg (D_WIN32_IO, "WIN32 I/O: TAP Completion BAD STATE");
+      break;
+
+    default:
+      ASSERT (0);
+    }
+
+  if (buf)
+    buf->len = ret;
+  return ret;
+}
+
+const struct tap_reg *
+get_tap_reg (struct gc_arena *gc)
+{
+  HKEY adapter_key;
+  LONG status;
+  DWORD len;
+  struct tap_reg *first = NULL;
+  struct tap_reg *last = NULL;
+  int i = 0;
+
+  status = RegOpenKeyEx(
+			HKEY_LOCAL_MACHINE,
+			ADAPTER_KEY,
+			0,
+			KEY_READ,
+			&adapter_key);
+
+  if (status != ERROR_SUCCESS)
+    msg (M_FATAL, "Error opening registry key: %s", ADAPTER_KEY);
+
+  while (true)
+    {
+      char enum_name[256];
+      char unit_string[256];
+      HKEY unit_key;
+      char component_id_string[] = "ComponentId";
+      char component_id[256];
+      char net_cfg_instance_id_string[] = "NetCfgInstanceId";
+      char net_cfg_instance_id[256];
+      DWORD data_type;
+
+      len = sizeof (enum_name);
+      status = RegEnumKeyEx(
+			    adapter_key,
+			    i,
+			    enum_name,
+			    &len,
+			    NULL,
+			    NULL,
+			    NULL,
+			    NULL);
+      if (status == ERROR_NO_MORE_ITEMS)
+	break;
+      else if (status != ERROR_SUCCESS)
+	msg (M_FATAL, "Error enumerating registry subkeys of key: %s",
+	     ADAPTER_KEY);
+
+      openvpn_snprintf (unit_string, sizeof(unit_string), "%s\\%s",
+			ADAPTER_KEY, enum_name);
+
+      status = RegOpenKeyEx(
+			    HKEY_LOCAL_MACHINE,
+			    unit_string,
+			    0,
+			    KEY_READ,
+			    &unit_key);
+
+      if (status != ERROR_SUCCESS)
+	dmsg (D_REGISTRY, "Error opening registry key: %s", unit_string);
+      else
+	{
+	  len = sizeof (component_id);
+	  status = RegQueryValueEx(
+				   unit_key,
+				   component_id_string,
+				   NULL,
+				   &data_type,
+				   component_id,
+				   &len);
+
+	  if (status != ERROR_SUCCESS || data_type != REG_SZ)
+	    dmsg (D_REGISTRY, "Error opening registry key: %s\\%s",
+		 unit_string, component_id_string);
+	  else
+	    {	      
+	      len = sizeof (net_cfg_instance_id);
+	      status = RegQueryValueEx(
+				       unit_key,
+				       net_cfg_instance_id_string,
+				       NULL,
+				       &data_type,
+				       net_cfg_instance_id,
+				       &len);
+
+	      if (status == ERROR_SUCCESS && data_type == REG_SZ)
+		{
+		  if (!strcmp (component_id, TAP_COMPONENT_ID))
+		    {
+		      struct tap_reg *reg;
+		      ALLOC_OBJ_CLEAR_GC (reg, struct tap_reg, gc);
+		      reg->guid = string_alloc (net_cfg_instance_id, gc);
+		      
+		      /* link into return list */
+		      if (!first)
+			first = reg;
+		      if (last)
+			last->next = reg;
+		      last = reg;
+		    }
+		}
+	    }
+	  RegCloseKey (unit_key);
+	}
+      ++i;
+    }
+
+  RegCloseKey (adapter_key);
+  return first;
+}
+
+const struct panel_reg *
+get_panel_reg (struct gc_arena *gc)
+{
+  LONG status;
+  HKEY network_connections_key;
+  DWORD len;
+  struct panel_reg *first = NULL;
+  struct panel_reg *last = NULL;
+  int i = 0;
+
+  status = RegOpenKeyEx(
+			HKEY_LOCAL_MACHINE,
+			NETWORK_CONNECTIONS_KEY,
+			0,
+			KEY_READ,
+			&network_connections_key);
+
+  if (status != ERROR_SUCCESS)
+    msg (M_FATAL, "Error opening registry key: %s", NETWORK_CONNECTIONS_KEY);
+
+  while (true)
+    {
+      char enum_name[256];
+      char connection_string[256];
+      HKEY connection_key;
+      char name_data[256];
+      DWORD name_type;
+      const char name_string[] = "Name";
+
+      len = sizeof (enum_name);
+      status = RegEnumKeyEx(
+			    network_connections_key,
+			    i,
+			    enum_name,
+			    &len,
+			    NULL,
+			    NULL,
+			    NULL,
+			    NULL);
+      if (status == ERROR_NO_MORE_ITEMS)
+	break;
+      else if (status != ERROR_SUCCESS)
+	msg (M_FATAL, "Error enumerating registry subkeys of key: %s",
+	     NETWORK_CONNECTIONS_KEY);
+
+      openvpn_snprintf (connection_string, sizeof(connection_string),
+			"%s\\%s\\Connection",
+			NETWORK_CONNECTIONS_KEY, enum_name);
+
+      status = RegOpenKeyEx(
+			    HKEY_LOCAL_MACHINE,
+			    connection_string,
+			    0,
+			    KEY_READ,
+			    &connection_key);
+
+      if (status != ERROR_SUCCESS)
+	dmsg (D_REGISTRY, "Error opening registry key: %s", connection_string);
+      else
+	{
+	  len = sizeof (name_data);
+	  status = RegQueryValueEx(
+				   connection_key,
+				   name_string,
+				   NULL,
+				   &name_type,
+				   name_data,
+				   &len);
+
+	  if (status != ERROR_SUCCESS || name_type != REG_SZ)
+	    dmsg (D_REGISTRY, "Error opening registry key: %s\\%s\\%s",
+		 NETWORK_CONNECTIONS_KEY, connection_string, name_string);
+	  else
+	    {
+	      struct panel_reg *reg;
+
+	      ALLOC_OBJ_CLEAR_GC (reg, struct panel_reg, gc);
+	      reg->name = string_alloc (name_data, gc);
+	      reg->guid = string_alloc (enum_name, gc);
+		      
+	      /* link into return list */
+	      if (!first)
+		first = reg;
+	      if (last)
+		last->next = reg;
+	      last = reg;
+	    }
+	  RegCloseKey (connection_key);
+	}
+      ++i;
+    }
+
+  RegCloseKey (network_connections_key);
+
+  return first;
+}
+
+/*
+ * Check that two addresses are part of the same 255.255.255.252 subnet.
+ */
+void
+verify_255_255_255_252 (in_addr_t local, in_addr_t remote)
+{
+  struct gc_arena gc = gc_new ();
+  const unsigned int mask = 3;
+  const char *err = NULL;
+
+  if (local == remote)
+    {
+      err = "must be different";
+      goto error;
+    }
+  if ((local & (~mask)) != (remote & (~mask)))
+    {
+      err = "must exist within the same 255.255.255.252 subnet.  This is a limitation of --dev tun when used with the TAP-WIN32 driver";
+      goto error;
+    }
+  if ((local & mask) == 0
+      || (local & mask) == 3
+      || (remote & mask) == 0
+      || (remote & mask) == 3)
+    {
+      err = "cannot use the first or last address within a given 255.255.255.252 subnet.  This is a limitation of --dev tun when used with the TAP-WIN32 driver";
+      goto error;
+    }
+
+  gc_free (&gc);
+  return;
+
+ error:
+  msg (M_FATAL, "There is a problem in your selection of --ifconfig endpoints [local=%s, remote=%s].  The local and remote VPN endpoints %s.  Try '" PACKAGE " --show-valid-subnets' option for more info.",
+       print_in_addr_t (local, 0, &gc),
+       print_in_addr_t (remote, 0, &gc),
+       err);
+  gc_free (&gc);
+}
+
+void show_valid_win32_tun_subnets (void)
+{
+  int i;
+  int col = 0;
+
+  printf ("On Windows, point-to-point IP support (i.e. --dev tun)\n");
+  printf ("is emulated by the TAP-Win32 driver.  The major limitation\n");
+  printf ("imposed by this approach is that the --ifconfig local and\n");
+  printf ("remote endpoints must be part of the same 255.255.255.252\n");
+  printf ("subnet.  The following list shows examples of endpoint\n");
+  printf ("pairs which satisfy this requirement.  Only the final\n");
+  printf ("component of the IP address pairs is at issue.\n\n");
+  printf ("As an example, the following option would be correct:\n");
+  printf ("    --ifconfig 10.7.0.5 10.7.0.6 (on host A)\n");
+  printf ("    --ifconfig 10.7.0.6 10.7.0.5 (on host B)\n");
+  printf ("because [5,6] is part of the below list.\n\n");
+
+  for (i = 0; i < 256; i += 4)
+    {
+      printf("[%3d,%3d] ", i+1, i+2);
+      if (++col > 4)
+	{
+	  col = 0;
+	  printf ("\n");
+	}
+    }
+  if (col)
+    printf ("\n");
+}
+
+void
+show_tap_win32_adapters (int msglev, int warnlev)
+{
+  struct gc_arena gc = gc_new ();
+
+  bool warn_panel_null = false;
+  bool warn_panel_dup = false;
+  bool warn_tap_dup = false;
+
+  int links;
+
+  const struct tap_reg *tr;
+  const struct tap_reg *tr1;
+  const struct panel_reg *pr;
+
+  const struct tap_reg *tap_reg = get_tap_reg (&gc);
+  const struct panel_reg *panel_reg = get_panel_reg (&gc);
+
+  msg (msglev, "Available TAP-WIN32 adapters [name, GUID]:");
+
+  /* loop through each TAP-Win32 adapter registry entry */
+  for (tr = tap_reg; tr != NULL; tr = tr->next)
+    {
+      links = 0;
+
+      /* loop through each network connections entry in the control panel */
+      for (pr = panel_reg; pr != NULL; pr = pr->next)
+	{
+	  if (!strcmp (tr->guid, pr->guid))
+	    {
+	      msg (msglev, "'%s' %s", pr->name, tr->guid);
+	      ++links;
+	    }
+	}
+
+      if (links > 1)
+	{
+	  warn_panel_dup = true;
+	}
+      else if (links == 0)
+	{
+	  /* a TAP adapter exists without a link from the network
+	     connections control panel */
+	  warn_panel_null = true;
+	  msg (msglev, "[NULL] %s", tr->guid);
+	}
+    }
+
+  /* check for TAP-Win32 adapter duplicated GUIDs */
+  for (tr = tap_reg; tr != NULL; tr = tr->next)
+    {
+      for (tr1 = tap_reg; tr1 != NULL; tr1 = tr1->next)
+	{
+	  if (tr != tr1 && !strcmp (tr->guid, tr1->guid))
+	    warn_tap_dup = true;
+	}
+    }
+
+  /* warn on registry inconsistencies */
+  if (warn_tap_dup)
+    msg (warnlev, "WARNING: Some TAP-Win32 adapters have duplicate GUIDs");
+
+  if (warn_panel_dup)
+    msg (warnlev, "WARNING: Some TAP-Win32 adapters have duplicate links from the Network Connections control panel");
+
+  if (warn_panel_null)
+    msg (warnlev, "WARNING: Some TAP-Win32 adapters have no link from the Network Connections control panel");
+
+  gc_free (&gc);
+}
+
+/*
+ * Confirm that GUID is a TAP-Win32 adapter.
+ */
+static bool
+is_tap_win32 (const char *guid, const struct tap_reg *tap_reg)
+{
+  const struct tap_reg *tr;
+
+  for (tr = tap_reg; tr != NULL; tr = tr->next)
+    {
+      if (guid && !strcmp (tr->guid, guid))
+	return true;
+    }
+
+  return false;
+}
+
+static const char *
+guid_to_name (const char *guid, const struct panel_reg *panel_reg)
+{
+  const struct panel_reg *pr;
+
+  for (pr = panel_reg; pr != NULL; pr = pr->next)
+    {
+      if (guid && !strcmp (pr->guid, guid))
+	return pr->name;
+    }
+
+  return NULL;
+}
+
+static const char *
+name_to_guid (const char *name, const struct tap_reg *tap_reg, const struct panel_reg *panel_reg)
+{
+  const struct panel_reg *pr;
+
+  for (pr = panel_reg; pr != NULL; pr = pr->next)
+    {
+      if (name && !strcmp (pr->name, name) && is_tap_win32 (pr->guid, tap_reg))
+	return pr->guid;
+    }
+
+  return NULL;
+}
+
+static void
+at_least_one_tap_win32 (const struct tap_reg *tap_reg)
+{
+  if (!tap_reg)
+    msg (M_FATAL, "There are no TAP-Win32 adapters on this system.  You should be able to create a TAP-Win32 adapter by going to Start -> All Programs -> " PACKAGE_NAME " -> Add a new TAP-Win32 virtual ethernet adapter.");
+}
+
+/*
+ * Get an adapter GUID and optional actual_name from the 
+ * registry for the TAP device # = device_number.
+ */
+static const char *
+get_unspecified_device_guid (const int device_number,
+		             char *actual_name,
+		             int actual_name_size,
+			     const struct tap_reg *tap_reg_src,
+			     const struct panel_reg *panel_reg_src,
+		             struct gc_arena *gc)
+{
+  const struct tap_reg *tap_reg = tap_reg_src;
+  struct buffer ret = clear_buf ();
+  struct buffer actual = clear_buf ();
+  int i;
+
+  ASSERT (device_number >= 0);
+
+  /* Make sure we have at least one TAP adapter */
+  if (!tap_reg)
+    return NULL;
+
+  /* The actual_name output buffer may be NULL */
+  if (actual_name)
+    {
+      ASSERT (actual_name_size > 0);
+      buf_set_write (&actual, actual_name, actual_name_size);
+    }
+
+  /* Move on to specified device number */
+  for (i = 0; i < device_number; i++)
+    {
+      tap_reg = tap_reg->next;
+      if (!tap_reg)
+	return NULL;
+    }
+
+  /* Save Network Panel name (if exists) in actual_name */
+  if (actual_name)
+    {
+      const char *act = guid_to_name (tap_reg->guid, panel_reg_src);
+      if (act)
+	buf_printf (&actual, "%s", act);
+      else
+	buf_printf (&actual, "NULL");
+    }
+
+  /* Save GUID for return value */
+  ret = alloc_buf_gc (256, gc);
+  buf_printf (&ret, "%s", tap_reg->guid);
+  return BSTR (&ret);
+}
+
+/*
+ * Lookup a --dev-node adapter name in the registry
+ * returning the GUID and optional actual_name.
+ */
+static const char *
+get_device_guid (const char *name,
+		 char *actual_name,
+		 int actual_name_size,
+		 const struct tap_reg *tap_reg,
+		 const struct panel_reg *panel_reg,
+		 struct gc_arena *gc)
+{
+  struct buffer ret = alloc_buf_gc (256, gc);
+  struct buffer actual = clear_buf ();
+
+  /* Make sure we have at least one TAP adapter */
+  if (!tap_reg)
+    return NULL;
+
+  /* The actual_name output buffer may be NULL */
+  if (actual_name)
+    {
+      ASSERT (actual_name_size > 0);
+      buf_set_write (&actual, actual_name, actual_name_size);
+    }
+
+  /* Check if GUID was explicitly specified as --dev-node parameter */
+  if (is_tap_win32 (name, tap_reg))
+    {
+      const char *act = guid_to_name (name, panel_reg);
+      buf_printf (&ret, "%s", name);
+      if (act)
+	buf_printf (&actual, "%s", act);
+      else
+	buf_printf (&actual, "NULL");
+      return BSTR (&ret);
+    }
+
+  /* Lookup TAP adapter in network connections list */
+  {
+    const char *guid = name_to_guid (name, tap_reg, panel_reg);
+    if (guid)
+      {
+	buf_printf (&actual, "%s", name);
+	buf_printf (&ret, "%s", guid);
+	return BSTR (&ret);
+      }
+  }
+
+  return NULL;
+}
+
+/*
+ * Return a TAP name for netsh commands.
+ */
+const char *
+get_netsh_id (const char *dev_node, struct gc_arena *gc)
+{
+  const struct tap_reg *tap_reg = get_tap_reg (gc);
+  const struct panel_reg *panel_reg = get_panel_reg (gc);
+  struct buffer actual = alloc_buf_gc (256, gc);
+  const char *guid;
+
+  at_least_one_tap_win32 (tap_reg);
+
+  if (dev_node)
+    {
+      guid = get_device_guid (dev_node, BPTR (&actual), BCAP (&actual), tap_reg, panel_reg, gc);
+    }
+  else
+    {
+      guid = get_unspecified_device_guid (0, BPTR (&actual), BCAP (&actual), tap_reg, panel_reg, gc);
+
+      if (get_unspecified_device_guid (1, NULL, 0, tap_reg, panel_reg, gc)) /* ambiguous if more than one TAP-Win32 adapter */
+	guid = NULL;
+    }
+
+  if (!guid)
+    return "NULL";         /* not found */
+  else if (strcmp (BPTR (&actual), "NULL"))
+    return BPTR (&actual); /* control panel name */
+  else
+    return guid;           /* no control panel name, return GUID instead */
+}
+
+/*
+ * Get adapter info list
+ */
+const IP_ADAPTER_INFO *
+get_adapter_info_list (struct gc_arena *gc)
+{
+  ULONG size = 0;
+  IP_ADAPTER_INFO *pi = NULL;
+  DWORD status;
+
+  if ((status = GetAdaptersInfo (NULL, &size)) != ERROR_BUFFER_OVERFLOW)
+    {
+      msg (M_INFO, "GetAdaptersInfo #1 failed (status=%u) : %s",
+	   (unsigned int)status,
+	   strerror_win32 (status, gc));
+    }
+  else
+    {
+      pi = (PIP_ADAPTER_INFO) gc_malloc (size, false, gc);
+      if ((status = GetAdaptersInfo (pi, &size)) == NO_ERROR)
+	return pi;
+      else
+	{
+	  msg (M_INFO, "GetAdaptersInfo #2 failed (status=%u) : %s",
+	       (unsigned int)status,
+	       strerror_win32 (status, gc));
+	}
+    }
+  return pi;
+}
+
+static const IP_INTERFACE_INFO *
+get_interface_info_list (struct gc_arena *gc)
+{
+  ULONG size = 0;
+  IP_INTERFACE_INFO *ii = NULL;
+  DWORD status;
+
+  if ((status = GetInterfaceInfo (NULL, &size)) != ERROR_INSUFFICIENT_BUFFER)
+    {
+      msg (M_INFO, "GetInterfaceInfo #1 failed (status=%u) : %s",
+	   (unsigned int)status,
+	   strerror_win32 (status, gc));
+    }
+  else
+    {
+      ii = (PIP_INTERFACE_INFO) gc_malloc (size, false, gc);
+      if ((status = GetInterfaceInfo (ii, &size)) == NO_ERROR)
+	return ii;
+      else
+	{
+	  msg (M_INFO, "GetInterfaceInfo #2 failed (status=%u) : %s",
+	       (unsigned int)status,
+	       strerror_win32 (status, gc));
+	}
+    }
+  return ii;
+}
+
+static const IP_ADAPTER_INDEX_MAP *
+get_interface_info (DWORD index, struct gc_arena *gc)
+{
+  const IP_INTERFACE_INFO *list = get_interface_info_list (gc);
+  if (list)
+    {
+      int i;
+      for (i = 0; i < list->NumAdapters; ++i)
+	{
+	  const IP_ADAPTER_INDEX_MAP *inter = &list->Adapter[i];
+	  if (index == inter->Index)
+	    return inter;
+	}
+    }
+  return NULL;
+}
+
+/*
+ * Given an adapter index, return a pointer to the
+ * IP_ADAPTER_INFO structure for that adapter.
+ */
+
+static const IP_ADAPTER_INFO *
+get_adapter (const IP_ADAPTER_INFO *ai, DWORD index)
+{
+  if (ai && index != (DWORD)~0)
+    {
+      const IP_ADAPTER_INFO *a;
+
+      /* find index in the linked list */
+      for (a = ai; a != NULL; a = a->Next)
+	{
+	  if (a->Index == index)
+	    return a;
+	}
+    }
+  return NULL;
+}
+
+static const IP_ADAPTER_INFO *
+get_adapter_info (DWORD index, struct gc_arena *gc)
+{
+  return get_adapter (get_adapter_info_list (gc), index);
+}
+
+static int
+get_adapter_n_ip_netmask (const IP_ADAPTER_INFO *ai)
+{
+  if (ai)
+    {
+      int n = 0;
+      const IP_ADDR_STRING *ip = &ai->IpAddressList;
+
+      while (ip)
+	{
+	  ++n;
+	  ip = ip->Next;
+	}
+      return n;
+    }
+  else
+    return 0;
+}
+
+static bool
+get_adapter_ip_netmask (const IP_ADAPTER_INFO *ai, const int n, in_addr_t *ip, in_addr_t *netmask)
+{
+  bool ret = false;
+  *ip = 0;
+  *netmask = 0;
+
+  if (ai)
+    {
+      const IP_ADDR_STRING *iplist = &ai->IpAddressList;
+      int i = 0;
+
+      while (iplist)
+	{
+	  if (i == n)
+	    break;
+	  ++i;
+	  iplist = iplist->Next;
+	}
+
+      if (iplist)
+	{
+	  const unsigned int getaddr_flags = GETADDR_HOST_ORDER;
+	  const char *ip_str = iplist->IpAddress.String;
+	  const char *netmask_str = iplist->IpMask.String;
+	  bool succeed1 = false;
+	  bool succeed2 = false;
+
+	  if (ip_str && netmask_str && strlen (ip_str) && strlen (netmask_str))
+	    {
+	      *ip = getaddr (getaddr_flags, ip_str, 0, &succeed1, NULL);
+	      *netmask = getaddr (getaddr_flags, netmask_str, 0, &succeed2, NULL);
+	      ret = (succeed1 == true && succeed2 == true);
+	    }
+	}
+    }
+
+  return ret;
+}
+
+const IP_ADAPTER_INFO *
+get_tun_adapter (const struct tuntap *tt, const IP_ADAPTER_INFO *list)
+{
+  if (list && tt)
+    return get_adapter (list, tt->adapter_index);
+  else
+    return NULL;
+}
+
+bool
+is_adapter_up (const struct tuntap *tt, const IP_ADAPTER_INFO *list)
+{
+  int i;
+  bool ret = false;
+
+  const IP_ADAPTER_INFO *ai = get_tun_adapter (tt, list);
+
+  if (ai)
+    {
+      const int n = get_adapter_n_ip_netmask (ai);
+
+      /* loop once for every IP/netmask assigned to adapter */
+      for (i = 0; i < n; ++i)
+	{
+	  in_addr_t ip, netmask;
+	  if (get_adapter_ip_netmask (ai, i, &ip, &netmask))
+	    {
+	      if (tt->local && tt->adapter_netmask)
+		{
+		  /* wait for our --ifconfig parms to match the actual adapter parms */
+		  if (tt->local == ip && tt->adapter_netmask == netmask)
+		    ret = true;
+		}
+	      else
+		{
+		  /* --ifconfig was not defined, maybe using a real DHCP server */
+		  if (ip && netmask)
+		    ret = true;
+		}
+	    }
+	}
+    }
+  else
+    ret = true; /* this can occur when TAP adapter is bridged */
+
+  return ret;
+}
+
+bool
+is_ip_in_adapter_subnet (const IP_ADAPTER_INFO *ai, const in_addr_t ip, in_addr_t *highest_netmask)
+{
+  int i;
+  bool ret = false;
+
+  if (highest_netmask)
+    *highest_netmask = 0;
+
+  if (ai)
+    {
+      const int n = get_adapter_n_ip_netmask (ai);
+      for (i = 0; i < n; ++i)
+	{
+	  in_addr_t adapter_ip, adapter_netmask;
+	  if (get_adapter_ip_netmask (ai, i, &adapter_ip, &adapter_netmask))
+	    {
+	      if (adapter_ip && adapter_netmask && (ip & adapter_netmask) == (adapter_ip & adapter_netmask))
+		{
+		  if (highest_netmask && adapter_netmask > *highest_netmask)
+		    *highest_netmask = adapter_netmask;
+		  ret = true;
+		}
+	    }
+	}
+    }
+  return ret;
+}
+
+DWORD
+adapter_index_of_ip (const IP_ADAPTER_INFO *list, const in_addr_t ip, int *count)
+{
+  struct gc_arena gc = gc_new ();
+  DWORD ret = ~0;
+  in_addr_t highest_netmask = 0;
+  bool first = true;
+
+  if (count)
+    *count = 0;
+
+  while (list)
+    {
+      in_addr_t hn;
+
+      if (is_ip_in_adapter_subnet (list, ip, &hn))
+	{
+	  if (first || hn > highest_netmask)
+	    {
+	      highest_netmask = hn;
+	      if (count)
+		*count = 1;
+	      ret = list->Index;
+	      first = false;
+	    }
+	  else if (hn == highest_netmask)
+	    {
+	      if (count)
+		++*count;
+	    }
+	}
+      list = list->Next;
+    }
+
+  dmsg (D_ROUTE_DEBUG, "DEBUG: IP Locate: ip=%s nm=%s index=%d count=%d",
+       print_in_addr_t (ip, 0, &gc),
+       print_in_addr_t (highest_netmask, 0, &gc),
+       (int)ret,
+       count ? *count : -1);
+
+  if (ret == ~0 && count)
+    *count = 0;
+
+  gc_free (&gc);
+  return ret;
+}
+
+/*
+ * Given an adapter index, return true if the adapter
+ * is DHCP disabled.
+ */
+static bool
+dhcp_disabled (DWORD index)
+{
+  struct gc_arena gc = gc_new ();
+  const IP_ADAPTER_INFO *ai = get_adapter_info (index, &gc);
+  bool ret = false;
+
+  if (ai && !ai->DhcpEnabled)
+    ret = true;
+
+  gc_free (&gc);
+  return ret;
+}
+
+/*
+ * Delete all temporary address/netmask pairs which were added
+ * to adapter (given by index) by previous calls to AddIPAddress.
+ */
+static void
+delete_temp_addresses (DWORD index)
+{
+  struct gc_arena gc = gc_new ();
+  const IP_ADAPTER_INFO *a = get_adapter_info (index, &gc);
+
+  if (a)
+    {
+      const IP_ADDR_STRING *ip = &a->IpAddressList;
+      while (ip)
+	{
+	  DWORD status;
+	  const DWORD context = ip->Context;
+
+	  if ((status = DeleteIPAddress ((ULONG) context)) == NO_ERROR)
+	    {
+	      msg (M_INFO, "Successfully deleted previously set dynamic IP/netmask: %s/%s",
+		   ip->IpAddress.String,
+		   ip->IpMask.String);
+	    }
+	  else
+	    {
+	      const char *empty = "0.0.0.0";
+	      if (strcmp (ip->IpAddress.String, empty)
+		  || strcmp (ip->IpMask.String, empty))
+		msg (M_INFO, "NOTE: could not delete previously set dynamic IP/netmask: %s/%s (status=%u)",
+		     ip->IpAddress.String,
+		     ip->IpMask.String,
+		     (unsigned int)status);
+	    }
+	  ip = ip->Next;
+	}
+    }
+  gc_free (&gc);
+}
+
+/*
+ * Get interface index for use with IP Helper API functions.
+ */
+static DWORD
+get_interface_index (const char *guid)
+{
+  struct gc_arena gc = gc_new ();
+  ULONG index;
+  DWORD status;
+  wchar_t wbuf[256];
+  snwprintf (wbuf, SIZE (wbuf), L"\\DEVICE\\TCPIP_%S", guid);
+  wbuf [SIZE(wbuf) - 1] = 0;
+  if ((status = GetAdapterIndex (wbuf, &index)) != NO_ERROR)
+    {
+      msg (M_INFO, "NOTE: could not get adapter index for %S, status=%u : %s",
+	   wbuf,
+	   (unsigned int)status,
+	   strerror_win32 (status, &gc));
+      gc_free (&gc);
+      return (DWORD)~0;
+    }
+  else
+    {
+      gc_free (&gc);
+      return index;
+    }
+}
+
+/*
+ * Return a string representing a PIP_ADDR_STRING
+ */
+static const char *
+format_ip_addr_string (const IP_ADDR_STRING *ip, struct gc_arena *gc)
+{
+  struct buffer out = alloc_buf_gc (256, gc);
+  while (ip)
+    {
+      buf_printf (&out, "%s", ip->IpAddress.String);
+      if (strlen (ip->IpMask.String))
+	{
+	  buf_printf (&out, "/");
+	  buf_printf (&out, "%s", ip->IpMask.String);
+	}
+      buf_printf (&out, " ");
+      ip = ip->Next;
+    }
+  return BSTR (&out);
+}
+
+/*
+ * Show info for a single adapter
+ */
+static void
+show_adapter (int msglev, const IP_ADAPTER_INFO *a, struct gc_arena *gc)
+{
+  msg (msglev, "%s", a->Description);
+  msg (msglev, "  Index = %d", (int)a->Index);
+  msg (msglev, "  GUID = %s", a->AdapterName);
+  msg (msglev, "  IP = %s", format_ip_addr_string (&a->IpAddressList, gc));
+  msg (msglev, "  MAC = %s", format_hex_ex (a->Address, a->AddressLength, 0, 1, ":", gc));
+  msg (msglev, "  GATEWAY = %s", format_ip_addr_string (&a->GatewayList, gc));
+  if (a->DhcpEnabled)
+    {
+      msg (msglev, "  DHCP SERV = %s", format_ip_addr_string (&a->DhcpServer, gc));
+      msg (msglev, "  DHCP LEASE OBTAINED = %s", time_string (a->LeaseObtained, 0, false, gc));
+      msg (msglev, "  DHCP LEASE EXPIRES  = %s", time_string (a->LeaseExpires, 0, false, gc));
+    }
+  if (a->HaveWins)
+    {
+      msg (msglev, "  PRI WINS = %s", format_ip_addr_string (&a->PrimaryWinsServer, gc));
+      msg (msglev, "  SEC WINS = %s", format_ip_addr_string (&a->SecondaryWinsServer, gc));
+    }
+}
+
+/*
+ * Show current adapter list
+ */
+void
+show_adapters (int msglev)
+{
+  struct gc_arena gc = gc_new ();
+  const IP_ADAPTER_INFO *ai = get_adapter_info_list (&gc);
+
+  msg (msglev, "SYSTEM ADAPTER LIST");
+  if (ai)
+    {
+      const IP_ADAPTER_INFO *a;
+
+      /* find index in the linked list */
+      for (a = ai; a != NULL; a = a->Next)
+	{
+	  show_adapter (msglev, a, &gc);
+	}
+    }
+  gc_free (&gc);
+}
+
+/*
+ * DHCP release/renewal
+ */
+
+bool
+dhcp_release (const struct tuntap *tt)
+{
+  struct gc_arena gc = gc_new ();
+  bool ret = false;
+  if (tt && tt->options.ip_win32_type == IPW32_SET_DHCP_MASQ && tt->adapter_index != ~0)
+    {
+      const IP_ADAPTER_INDEX_MAP *inter = get_interface_info (tt->adapter_index, &gc);
+      if (inter)
+	{
+	  DWORD status = IpReleaseAddress ((IP_ADAPTER_INDEX_MAP *)inter);
+	  if (status == NO_ERROR)
+	    {
+	      msg (D_TUNTAP_INFO, "TAP: DHCP address released");
+	      ret = true;
+	    }
+	  else
+	    msg (M_WARN, "NOTE: Release of DHCP-assigned IP address lease on TAP-Win32 adapter failed: %s (code=%u)",
+		 strerror_win32 (status, &gc),
+		 (unsigned int)status);
+	}
+    }
+  gc_free (&gc);
+  return ret;
+}
+
+bool
+dhcp_renew (const struct tuntap *tt)
+{
+  struct gc_arena gc = gc_new ();
+  bool ret = false;
+  if (tt && tt->options.ip_win32_type == IPW32_SET_DHCP_MASQ && tt->adapter_index != ~0)
+    {
+      const IP_ADAPTER_INDEX_MAP *inter = get_interface_info (tt->adapter_index, &gc);
+      if (inter)
+	{
+	  DWORD status = IpRenewAddress ((IP_ADAPTER_INDEX_MAP *)inter);
+	  if (status == NO_ERROR)
+	    {
+	      msg (D_TUNTAP_INFO, "TAP: DHCP address renewal succeeded");
+	      ret = true;
+	    }
+	  else
+	    msg (M_WARN, "WARNING: Failed to renew DHCP IP address lease on TAP-Win32 adapter: %s (code=%u)",
+		 strerror_win32 (status, &gc),
+		 (unsigned int)status);
+	}
+    }
+  gc_free (&gc);
+  return ret;
+}
+
+/*
+ * Convert DHCP options from the command line / config file
+ * into a raw DHCP-format options string.
+ */
+
+static void
+write_dhcp_u8 (struct buffer *buf, const int type, const int data)
+{
+  if (!buf_safe (buf, 3))
+    msg (M_FATAL, "write_dhcp_u8: buffer overflow building DHCP options");
+  buf_write_u8 (buf, type);
+  buf_write_u8 (buf, 1);
+  buf_write_u8 (buf, data);
+}
+
+static void
+write_dhcp_u32_array (struct buffer *buf, const int type, const uint32_t *data, const unsigned int len)
+{
+  if (len > 0)
+    {
+      int i;
+      const int size = len * sizeof (uint32_t);
+
+      if (!buf_safe (buf, 2 + size))
+	msg (M_FATAL, "write_dhcp_u32_array: buffer overflow building DHCP options");
+      if (size < 1 || size > 255)
+	msg (M_FATAL, "write_dhcp_u32_array: size (%d) must be > 0 and <= 255", size);
+      buf_write_u8 (buf, type);
+      buf_write_u8 (buf, size);
+      for (i = 0; i < len; ++i)
+	buf_write_u32 (buf, data[i]);
+    }
+}
+
+static void
+write_dhcp_str (struct buffer *buf, const int type, const char *str)
+{
+  const int len = strlen (str);
+  if (!buf_safe (buf, 2 + len))
+    msg (M_FATAL, "write_dhcp_str: buffer overflow building DHCP options");
+  if (len < 1 || len > 255)
+    msg (M_FATAL, "write_dhcp_str: string '%s' must be > 0 bytes and <= 255 bytes", str);
+  buf_write_u8 (buf, type);
+  buf_write_u8 (buf, len);
+  buf_write (buf, str, len);
+}
+
+static void
+build_dhcp_options_string (struct buffer *buf, const struct tuntap_options *o)
+{
+  if (o->domain)
+    write_dhcp_str (buf, 15, o->domain);
+
+  if (o->netbios_scope)
+    write_dhcp_str (buf, 47, o->netbios_scope);
+
+  if (o->netbios_node_type)
+    write_dhcp_u8 (buf, 46, o->netbios_node_type);
+
+  write_dhcp_u32_array (buf, 6, (uint32_t*)o->dns, o->dns_len);
+  write_dhcp_u32_array (buf, 44, (uint32_t*)o->wins, o->wins_len);
+  write_dhcp_u32_array (buf, 42, (uint32_t*)o->ntp, o->ntp_len);
+  write_dhcp_u32_array (buf, 45, (uint32_t*)o->nbdd, o->nbdd_len);
+
+  /* the MS DHCP server option 'Disable Netbios-over-TCP/IP
+     is implemented as vendor option 001, value 002.
+     A value of 001 means 'leave NBT alone' which is the default */
+  if (o->disable_nbt)
+  {
+    buf_write_u8 (buf, 43);
+    buf_write_u8 (buf,  6);  /* total length field */
+    buf_write_u8 (buf,  0x001);
+    buf_write_u8 (buf,  4);  /* length of the vendor specified field */
+    buf_write_u32 (buf, 0x002);
+  }
+}
+
+void
+open_tun (const char *dev, const char *dev_type, const char *dev_node, bool ipv6, struct tuntap *tt)
+{
+  struct gc_arena gc = gc_new ();
+  char device_path[256];
+  const char *device_guid = NULL;
+  DWORD len;
+
+  /*netcmd_semaphore_lock ();*/
+
+  ipv6_support (ipv6, false, tt);
+
+  if (tt->type == DEV_TYPE_NULL)
+    {
+      open_null (tt);
+      gc_free (&gc);
+      return;
+    }
+  else if (tt->type == DEV_TYPE_TAP || tt->type == DEV_TYPE_TUN)
+    {
+      ;
+    }
+  else
+    {
+      msg (M_FATAL|M_NOPREFIX, "Unknown virtual device type: '%s'", dev);
+    }
+
+  /*
+   * Lookup the device name in the registry, using the --dev-node high level name.
+   */
+  {
+    const struct tap_reg *tap_reg = get_tap_reg (&gc);
+    const struct panel_reg *panel_reg = get_panel_reg (&gc);
+    char guid_buffer[256];
+
+    at_least_one_tap_win32 (tap_reg);
+
+    if (dev_node)
+      {
+        /* Get the device GUID for the device specified with --dev-node. */
+        device_guid = get_device_guid (dev_node, guid_buffer, sizeof (guid_buffer), tap_reg, panel_reg, &gc);
+
+	if (!device_guid)
+	    msg (M_FATAL, "TAP-Win32 adapter '%s' not found", dev_node);
+
+        /* Open Windows TAP-Win32 adapter */
+        openvpn_snprintf (device_path, sizeof(device_path), "%s%s%s",
+   		          USERMODEDEVICEDIR,
+		          device_guid,
+		          TAPSUFFIX);
+
+        tt->hand = CreateFile (
+			       device_path,
+			       GENERIC_READ | GENERIC_WRITE,
+			       0, /* was: FILE_SHARE_READ */
+			       0,
+			       OPEN_EXISTING,
+			       FILE_ATTRIBUTE_SYSTEM | FILE_FLAG_OVERLAPPED,
+			       0
+			       );
+
+        if (tt->hand == INVALID_HANDLE_VALUE)
+          msg (M_ERR, "CreateFile failed on TAP device: %s", device_path);
+      }
+    else 
+      {
+        int device_number = 0;
+
+        /* Try opening all TAP devices until we find one available */
+        while (true)
+          {
+            device_guid = get_unspecified_device_guid (device_number, 
+						       guid_buffer, 
+						       sizeof (guid_buffer),
+						       tap_reg,
+						       panel_reg,
+						       &gc);
+
+	    if (!device_guid)
+	      msg (M_FATAL, "All TAP-Win32 adapters on this system are currently in use.");
+
+            /* Open Windows TAP-Win32 adapter */
+            openvpn_snprintf (device_path, sizeof(device_path), "%s%s%s",
+       		  	      USERMODEDEVICEDIR,
+			      device_guid,
+			      TAPSUFFIX);
+
+            tt->hand = CreateFile (
+			 	   device_path,
+				   GENERIC_READ | GENERIC_WRITE,
+				   0, /* was: FILE_SHARE_READ */
+				   0,
+				   OPEN_EXISTING,
+				   FILE_ATTRIBUTE_SYSTEM | FILE_FLAG_OVERLAPPED,
+				   0
+				   );
+
+            if (tt->hand == INVALID_HANDLE_VALUE)
+              msg (D_TUNTAP_INFO, "CreateFile failed on TAP device: %s", device_path);
+            else
+              break;
+        
+            device_number++;
+          }
+      }
+
+    /* translate high-level device name into a device instance
+       GUID using the registry */
+    tt->actual_name = string_alloc (guid_buffer, NULL);
+  }
+
+  msg (M_INFO, "TAP-WIN32 device [%s] opened: %s", tt->actual_name, device_path);
+
+  /* get driver version info */
+  {
+    ULONG info[3];
+    CLEAR (info);
+    if (DeviceIoControl (tt->hand, TAP_IOCTL_GET_VERSION,
+			 &info, sizeof (info),
+			 &info, sizeof (info), &len, NULL))
+      {
+	msg (D_TUNTAP_INFO, "TAP-Win32 Driver Version %d.%d %s",
+	     (int) info[0],
+	     (int) info[1],
+	     (info[2] ? "(DEBUG)" : ""));
+
+      }
+    if ( !(info[0] > TAP_WIN32_MIN_MAJOR
+	   || (info[0] == TAP_WIN32_MIN_MAJOR && info[1] >= TAP_WIN32_MIN_MINOR)) )
+      msg (M_FATAL, "ERROR:  This version of " PACKAGE_NAME " requires a TAP-Win32 driver that is at least version %d.%d -- If you recently upgraded your " PACKAGE_NAME " distribution, a reboot is probably required at this point to get Windows to see the new driver.",
+	   TAP_WIN32_MIN_MAJOR,
+	   TAP_WIN32_MIN_MINOR);
+  }
+
+  /* get driver MTU */
+  {
+    ULONG mtu;
+    if (DeviceIoControl (tt->hand, TAP_IOCTL_GET_MTU,
+			 &mtu, sizeof (mtu),
+			 &mtu, sizeof (mtu), &len, NULL))
+      {
+	tt->post_open_mtu = (int) mtu;
+	msg (D_MTU_INFO, "TAP-Win32 MTU=%d", (int) mtu);
+      }
+  }
+
+  /* set point-to-point mode if TUN device */
+
+  if (tt->type == DEV_TYPE_TUN)
+    {
+      in_addr_t ep[2];
+      ep[0] = htonl (tt->local);
+      ep[1] = htonl (tt->remote_netmask);
+      if (!tt->did_ifconfig_setup)
+	{
+	  msg (M_FATAL, "ERROR: --dev tun also requires --ifconfig");
+	}
+      if (!DeviceIoControl (tt->hand, TAP_IOCTL_CONFIG_POINT_TO_POINT,
+			    ep, sizeof (ep),
+			    ep, sizeof (ep), &len, NULL))
+	msg (M_FATAL, "ERROR: The TAP-Win32 driver rejected a DeviceIoControl call to set Point-to-Point mode, which is required for --dev tun");
+    }
+
+  /* should we tell the TAP-Win32 driver to masquerade as a DHCP server as a means
+     of setting the adapter address? */
+  if (tt->did_ifconfig_setup && tt->options.ip_win32_type == IPW32_SET_DHCP_MASQ)
+    {
+      uint32_t ep[4];
+
+      /* We will answer DHCP requests with a reply to set IP/subnet to these values */
+      ep[0] = htonl (tt->local);
+      ep[1] = htonl (tt->adapter_netmask);
+
+      /* At what IP address should the DHCP server masquerade at? */
+      if (tt->type == DEV_TYPE_TUN)
+	{
+	  ep[2] = htonl (tt->remote_netmask);
+	  if (tt->options.dhcp_masq_custom_offset)
+	    msg (M_WARN, "WARNING: because you are using '--dev tun' mode, the '--ip-win32 dynamic [offset]' option is ignoring the offset parameter");
+	}
+      else
+	{
+	  in_addr_t dsa; /* DHCP server addr */
+
+	  ASSERT (tt->type == DEV_TYPE_TAP);
+
+	  if (tt->options.dhcp_masq_offset < 0)
+	    dsa = (tt->local | (~tt->adapter_netmask)) + tt->options.dhcp_masq_offset;
+	  else
+	    dsa = (tt->local & tt->adapter_netmask) + tt->options.dhcp_masq_offset;
+
+	  if (dsa == tt->local)
+	    msg (M_FATAL, "ERROR: There is a clash between the --ifconfig local address and the internal DHCP server address -- both are set to %s -- please use the --ip-win32 dynamic option to choose a different free address from the --ifconfig subnet for the internal DHCP server", print_in_addr_t (dsa, 0, &gc));
+
+	  if ((tt->local & tt->adapter_netmask) != (dsa & tt->adapter_netmask))
+	    msg (M_FATAL, "ERROR: --tap-win32 dynamic [offset] : offset is outside of --ifconfig subnet");
+
+	  ep[2] = htonl (dsa);
+	}
+
+      /* lease time in seconds */
+      ep[3] = (uint32_t) tt->options.dhcp_lease_time;
+
+      ASSERT (ep[3] > 0);
+
+      if (!DeviceIoControl (tt->hand, TAP_IOCTL_CONFIG_DHCP_MASQ,
+			    ep, sizeof (ep),
+			    ep, sizeof (ep), &len, NULL))
+	msg (M_FATAL, "ERROR: The TAP-Win32 driver rejected a DeviceIoControl call to set TAP_IOCTL_CONFIG_DHCP_MASQ mode");
+
+      msg (M_INFO, "Notified TAP-Win32 driver to set a DHCP IP/netmask of %s/%s on interface %s [DHCP-serv: %s, lease-time: %d]",
+	   print_in_addr_t (tt->local, 0, &gc),
+	   print_in_addr_t (tt->adapter_netmask, 0, &gc),
+	   device_guid,
+	   print_in_addr_t (ep[2], IA_NET_ORDER, &gc),
+	   ep[3]
+	   );
+
+      /* user-supplied DHCP options capability */
+      if (tt->options.dhcp_options)
+	{
+	  struct buffer buf = alloc_buf (256);
+	  build_dhcp_options_string (&buf, &tt->options);
+	  msg (D_DHCP_OPT, "DHCP option string: %s", format_hex (BPTR (&buf), BLEN (&buf), 0, &gc));
+	  if (!DeviceIoControl (tt->hand, TAP_IOCTL_CONFIG_DHCP_SET_OPT,
+				BPTR (&buf), BLEN (&buf),
+				BPTR (&buf), BLEN (&buf), &len, NULL))
+	    msg (M_FATAL, "ERROR: The TAP-Win32 driver rejected a TAP_IOCTL_CONFIG_DHCP_SET_OPT DeviceIoControl call");
+	  free_buf (&buf);
+	}
+    }
+
+  /* set driver media status to 'connected' */
+  {
+    ULONG status = TRUE;
+    if (!DeviceIoControl (tt->hand, TAP_IOCTL_SET_MEDIA_STATUS,
+			  &status, sizeof (status),
+			  &status, sizeof (status), &len, NULL))
+      msg (M_WARN, "WARNING: The TAP-Win32 driver rejected a TAP_IOCTL_SET_MEDIA_STATUS DeviceIoControl call.");
+  }
+
+  /* possible wait for adapter to come up */
+  {
+    int s = tt->options.tap_sleep;
+    if (s > 0)
+      {
+	msg (M_INFO, "Sleeping for %d seconds...", s);
+	openvpn_sleep (s);
+      }
+  }
+
+  /* possibly use IP Helper API to set IP address on adapter */
+  {
+    DWORD index = get_interface_index (device_guid);
+    tt->adapter_index = index;
+    
+    /* flush arp cache */
+    if (index != (DWORD)~0)
+      {
+	DWORD status;
+
+	if ((status = FlushIpNetTable (index)) == NO_ERROR)
+	  msg (M_INFO, "Successful ARP Flush on interface [%u] %s",
+	       (unsigned int)index,
+	       device_guid);
+	else
+	  msg (M_WARN, "NOTE: FlushIpNetTable failed on interface [%u] %s (status=%u) : %s",
+	       (unsigned int)index,
+	       device_guid,
+	       (unsigned int)status,
+	       strerror_win32 (status, &gc));
+      }
+
+    /*
+     * If the TAP-Win32 driver is masquerading as a DHCP server
+     * make sure the TCP/IP properties for the adapter are
+     * set correctly.
+     */
+    if (tt->did_ifconfig_setup && tt->options.ip_win32_type == IPW32_SET_DHCP_MASQ)
+      {
+	/* check dhcp enable status */
+	if (dhcp_disabled (index))
+	  msg (M_WARN, "WARNING: You have selected '--ip-win32 dynamic', which will not work unless the TAP-Win32 TCP/IP properties are set to 'Obtain an IP address automatically'");
+
+	/* force an explicit DHCP lease renewal on TAP adapter? */
+	if (tt->options.dhcp_pre_release)
+	  dhcp_release (tt);
+	if (tt->options.dhcp_renew)
+	  dhcp_renew (tt);
+      }
+
+    if (tt->did_ifconfig_setup && tt->options.ip_win32_type == IPW32_SET_IPAPI)
+      {
+	DWORD status;
+	const char *error_suffix = "I am having trouble using the Windows 'IP helper API' to automatically set the IP address -- consider using other --ip-win32 methods (not 'ipapi')";
+
+	/* couldn't get adapter index */
+	if (index == (DWORD)~0)
+	  {
+	    msg (M_FATAL, "ERROR: unable to get adapter index for interface %s -- %s",
+		 device_guid,
+		 error_suffix);
+	  }
+
+	/* check dhcp enable status */
+	if (dhcp_disabled (index))
+	  msg (M_WARN, "NOTE: You have selected (explicitly or by default) '--ip-win32 ipapi', which has a better chance of working correctly if the TAP-Win32 TCP/IP properties are set to 'Obtain an IP address automatically'");
+
+	/* delete previously added IP addresses which were not
+	   correctly deleted */
+	delete_temp_addresses (index);
+
+	/* add a new IP address */
+	if ((status = AddIPAddress (htonl(tt->local),
+				    htonl(tt->adapter_netmask),
+				    index,
+				    &tt->ipapi_context,
+				    &tt->ipapi_instance)) == NO_ERROR)
+	  msg (M_INFO, "Succeeded in adding a temporary IP/netmask of %s/%s to interface %s using the Win32 IP Helper API",
+	       print_in_addr_t (tt->local, 0, &gc),
+	       print_in_addr_t (tt->adapter_netmask, 0, &gc),
+	       device_guid
+	       );
+	else
+	  msg (M_FATAL, "ERROR: AddIPAddress %s/%s failed on interface %s, index=%d, status=%u (windows error: '%s') -- %s",
+	       print_in_addr_t (tt->local, 0, &gc),
+	       print_in_addr_t (tt->adapter_netmask, 0, &gc),
+	       device_guid,
+	       (int)index,
+	       (unsigned int)status,
+	       strerror_win32 (status, &gc),
+	       error_suffix);
+	tt->ipapi_context_defined = true;
+      }
+  }
+  /*netcmd_semaphore_release ();*/
+  gc_free (&gc);
+}
+
+const char *
+tap_win32_getinfo (const struct tuntap *tt, struct gc_arena *gc)
+{
+  if (tt && tt->hand != NULL)
+    {
+      struct buffer out = alloc_buf_gc (256, gc);
+      DWORD len;
+      if (DeviceIoControl (tt->hand, TAP_IOCTL_GET_INFO,
+			   BSTR (&out), BCAP (&out),
+			   BSTR (&out), BCAP (&out),
+			   &len, NULL))
+	{
+	  return BSTR (&out);
+	}
+    }
+  return NULL;
+}
+
+void
+tun_show_debug (struct tuntap *tt)
+{
+  if (tt && tt->hand != NULL)
+    {
+      struct buffer out = alloc_buf (1024);
+      DWORD len;
+      while (DeviceIoControl (tt->hand, TAP_IOCTL_GET_LOG_LINE,
+			      BSTR (&out), BCAP (&out),
+			      BSTR (&out), BCAP (&out),
+			      &len, NULL))
+	{
+	  msg (D_TAP_WIN32_DEBUG, "TAP-Win32: %s", BSTR (&out));
+	}
+      free_buf (&out);
+    }
+}
+
+void
+close_tun (struct tuntap *tt)
+{
+  struct gc_arena gc = gc_new ();
+
+  if (tt)
+    {
+#if 1
+      if (tt->ipapi_context_defined)
+	{
+	  DWORD status;
+	  if ((status = DeleteIPAddress (tt->ipapi_context)) != NO_ERROR)
+	    {
+	      msg (M_WARN, "Warning: DeleteIPAddress[%u] failed on TAP-Win32 adapter, status=%u : %s",
+		   (unsigned int)tt->ipapi_context,
+		   (unsigned int)status,
+		   strerror_win32 (status, &gc));
+	    }
+	}
+#endif
+
+      if (tt->options.dhcp_release)
+	dhcp_release (tt);
+
+      if (tt->hand != NULL)
+	{
+	  dmsg (D_WIN32_IO_LOW, "Attempting CancelIO on TAP-Win32 adapter");
+	  if (!CancelIo (tt->hand))
+	    msg (M_WARN | M_ERRNO, "Warning: CancelIO failed on TAP-Win32 adapter");
+	}
+
+      dmsg (D_WIN32_IO_LOW, "Attempting close of overlapped read event on TAP-Win32 adapter");
+      overlapped_io_close (&tt->reads);
+
+      dmsg (D_WIN32_IO_LOW, "Attempting close of overlapped write event on TAP-Win32 adapter");
+      overlapped_io_close (&tt->writes);
+
+      if (tt->hand != NULL)
+	{
+	  dmsg (D_WIN32_IO_LOW, "Attempting CloseHandle on TAP-Win32 adapter");
+	  if (!CloseHandle (tt->hand))
+	    msg (M_WARN | M_ERRNO, "Warning: CloseHandle failed on TAP-Win32 adapter");
+	}
+
+      if (tt->actual_name)
+	free (tt->actual_name);
+
+      clear_tuntap (tt);
+      free (tt);
+    }
+  gc_free (&gc);
+}
+
+/*
+ * Convert --ip-win32 constants between index and ascii form.
+ */
+
+struct ipset_names {
+  const char *short_form;
+};
+
+/* Indexed by IPW32_SET_x */
+static const struct ipset_names ipset_names[] = {
+  {"manual"},
+  {"netsh"},
+  {"ipapi"},
+  {"dynamic"}
+};
+
+int
+ascii2ipset (const char* name)
+{
+  int i;
+  ASSERT (IPW32_SET_N == SIZE (ipset_names));
+  for (i = 0; i < IPW32_SET_N; ++i)
+    if (!strcmp (name, ipset_names[i].short_form))
+      return i;
+  return -1;
+}
+
+const char *
+ipset2ascii (int index)
+{
+  ASSERT (IPW32_SET_N == SIZE (ipset_names));
+  if (index < 0 || index >= IPW32_SET_N)
+    return "[unknown --ip-win32 type]";
+  else
+    return ipset_names[index].short_form;
+}
+
+const char *
+ipset2ascii_all (struct gc_arena *gc)
+{
+  struct buffer out = alloc_buf_gc (256, gc);
+  int i;
+
+  ASSERT (IPW32_SET_N == SIZE (ipset_names));
+  for (i = 0; i < IPW32_SET_N; ++i)
+    {
+      if (i)
+	buf_printf(&out, " ");
+      buf_printf(&out, "[%s]", ipset2ascii(i));
+    }
+  return BSTR (&out);
+}
+
+#else /* generic */
+
+void
+open_tun (const char *dev, const char *dev_type, const char *dev_node, bool ipv6, struct tuntap *tt)
+{
+  open_tun_generic (dev, dev_type, dev_node, ipv6, false, true, tt);
+}
+
+void
+close_tun (struct tuntap* tt)
+{
+  if (tt)
+    {
+      close_tun_generic (tt);
+      free (tt);
+    }
+}
+
+int
+write_tun (struct tuntap* tt, uint8_t *buf, int len)
+{
+  return write (tt->fd, buf, len);
+}
+
+int
+read_tun (struct tuntap* tt, uint8_t *buf, int len)
+{
+  return read (tt->fd, buf, len);
+}
+
+#endif