Imported Upstream version 0.9.5a

1 files changed, 1557 insertions, 0 deletions

diff --git a/src/vpn/gnunet-helper-vpn-windows.c b/src/vpn/gnunet-helper-vpn-windows.c
new file mode 100644
index 0000000..b810dc7
--- /dev/null
+++ b/src/vpn/gnunet-helper-vpn-windows.c
@@ -0,0 +1,1557 @@
+/*
+     This file is part of GNUnet.
+     (C) 2010, 2012 Christian Grothoff
+
+     GNUnet is free software; you can redistribute it and/or modify
+     it under the terms of the GNU General Public License as published
+     by the Free Software Foundation; either version 3, or (at your
+     option) any later version.
+
+     GNUnet 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 GNUnet; see the file COPYING.  If not, write to the
+     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+     Boston, MA 02111-1307, USA.
+ */
+
+/**
+ * @file vpn/gnunet-helper-vpn-windows.c
+ * @brief the helper for the VPN service in win32 builds. 
+ * Opens a virtual network-interface, sends data received on the if to stdout, 
+ * sends data received on stdin to the interface
+ * @author Christian M. Fuchs
+ *
+ * The following list of people have reviewed this code and considered
+ * it safe since the last modification (if you reviewed it, please
+ * have your name added to the list):
+ *
+ */
+
+#include <stdio.h>
+#include <windows.h>
+#include <setupapi.h>
+#include <ddk/cfgmgr32.h>
+#include <ddk/newdev.h>
+#include <Winsock2.h>
+#include <time.h>
+#include "platform.h"
+#include "tap-windows.h"
+/**
+ * Need 'struct GNUNET_MessageHeader'.
+ */
+#include "gnunet_common.h"
+
+/**
+ * Need VPN message types.
+ */
+#include "gnunet_protocols.h"
+
+/**
+ * Should we print (interesting|debug) messages that can happen during
+ * normal operation?
+ */
+#define DEBUG GNUNET_NO
+
+#if DEBUG
+/* FIXME: define with varargs... */
+#define LOG_DEBUG(msg) fprintf (stderr, "%s", msg);
+#else
+#define LOG_DEBUG(msg) do {} while (0)
+#endif
+
+
+/**
+ * Maximum size of a GNUnet message (GNUNET_SERVER_MAX_MESSAGE_SIZE)
+ */
+#define MAX_SIZE 65536
+
+/**
+ * Name or Path+Name of our win32 driver.
+ * The .sys and .cat files HAVE to be in the same location as this file!
+ */
+#define INF_FILE "share/gnunet/tapw32/OemWin2k.inf"
+
+/**
+ * Name or Path+Name of our win64 driver.
+ * The .sys and .cat files HAVE to be in the same location as this file!
+ */
+#define INF_FILE64 "share/gnunet/tapw64/OemWin2k.inf"
+
+/**
+ * Hardware ID used in the inf-file. 
+ * This might change over time, as openvpn advances their driver
+ */
+#define HARDWARE_ID "tap0901"
+
+/**
+ * Minimum major-id of the driver version we can work with
+ */
+#define TAP_WIN_MIN_MAJOR 9
+
+/**
+ * Minimum minor-id of the driver version we can work with. 
+ * v <= 7 has buggy IPv6.
+ * v == 8 is broken for small IPv4 Packets
+ */
+#define TAP_WIN_MIN_MINOR 9
+
+/**
+ * Time in seconds to wait for our virtual device to go up after telling it to do so.
+ * 
+ * openvpn doesn't specify a value, 4 seems sane for testing, even for openwrt
+ * (in fact, 4 was chosen by a fair dice roll...)
+ */
+#define TAP32_POSTUP_WAITTIME 4
+
+/**
+ * Location of the network interface list resides in registry.
+ */
+#define INTERFACE_REGISTRY_LOCATION "SYSTEM\\CurrentControlSet\\Control\\Network\\{4D36E972-E325-11CE-BFC1-08002BE10318}"
+
+/**
+ * Our local process' PID. Used for creating a sufficiently unique additional 
+ * hardware ID for our device.
+ */
+static char secondary_hwid[LINE_LEN / 2];
+
+/**
+ * Device's visible Name, used to identify a network device in netsh.
+ * eg: "Local Area Connection 9"
+ */
+static char device_visible_name[256];
+
+/** 
+ * This is our own local instance of a virtual network interface
+ * It is (somewhat) equivalent to using tun/tap in unixoid systems
+ * 
+ * Upon initialization, we create such an device node.
+ * Upon termination, we remove it again.
+ * 
+ * If we crash this device might stay around.
+ */
+static HDEVINFO DeviceInfo = INVALID_HANDLE_VALUE;
+
+/**
+ * Registry Key we hand over to windows to spawn a new virtual interface
+ */
+static SP_DEVINFO_DATA DeviceNode;
+
+/**
+ * GUID of our virtual device in the form of 
+ * {12345678-1234-1234-1234-123456789abc} - in hex
+ */
+static char device_guid[256];
+
+
+/**
+ * Possible states of an IO facility.
+ */
+enum IO_State
+{
+
+  /** 
+   * overlapped I/O is ready for work 
+   */
+  IOSTATE_READY = 0,
+
+  /** 
+   * overlapped I/O has been queued 
+   */
+  IOSTATE_QUEUED,
+
+  /** 
+   * overlapped I/O has finished, but is waiting for it's write-partner 
+   */
+  IOSTATE_WAITING, 
+  
+  /** 
+   * there is a full buffer waiting
+   */
+  IOSTATE_RESUME,
+
+  /** 
+   * Operlapped IO states for facility objects
+   * overlapped I/O has failed, stop processing 
+   */
+  IOSTATE_FAILED 
+
+};
+
+
+/** 
+ * A IO Object + read/writebuffer + buffer-size for windows asynchronous IO handling
+ */
+struct io_facility
+{
+  /**
+   * The mode the state machine associated with this object is in.
+   */
+  enum IO_State facility_state;
+
+  /**
+   * If the path is open or blocked in general (used for quickly checking)
+   */
+  BOOL path_open; // BOOL is winbool (int), NOT boolean (unsigned char)!
+
+  /**
+   * Windows Object-Handle (used for accessing TAP and STDIN/STDOUT)
+   */
+  HANDLE handle;
+
+  /**
+   * Overlaped IO structure used for asynchronous IO in windows.
+   */
+  OVERLAPPED overlapped;
+
+  /**
+   * Buffer for reading things to and writing from...
+   */
+  unsigned char buffer[MAX_SIZE];
+
+  /**
+   * How much of this buffer was used when reading or how much data can be written
+   */
+  DWORD buffer_size;
+
+  /**
+   * Amount of data actually written or read by readfile/writefile.
+   */
+  DWORD buffer_size_processed;
+  
+  /**
+   * How much of this buffer we have writte in total
+   */
+  DWORD buffer_size_written;
+};
+
+/**
+ * ReOpenFile is only available as of XP SP2 and 2003 SP1
+ */
+WINBASEAPI HANDLE WINAPI ReOpenFile (HANDLE, DWORD, DWORD, DWORD);
+
+/**
+ * IsWow64Process definition for our is_win64, as this is a kernel function
+ */
+typedef BOOL (WINAPI *LPFN_ISWOW64PROCESS) (HANDLE, PBOOL);
+
+/**
+ * Determines if the host OS is win32 or win64
+ * 
+ * @return true if 
+ */
+BOOL
+is_win64 ()
+{
+#if defined(_WIN64)
+  //this is a win64 binary, 
+  return TRUE; 
+#elif defined(_WIN32)
+  //this is a 32bit binary, and we need to check if we are running in WOW64
+  BOOL success = FALSE;
+  BOOL on_wow64 = FALSE;
+  LPFN_ISWOW64PROCESS IsWow64Process = (LPFN_ISWOW64PROCESS) GetProcAddress (GetModuleHandle ("kernel32"), "IsWow64Process");
+  
+  if (NULL != IsWow64Process)
+      success = IsWow64Process (GetCurrentProcess (), &on_wow64);
+  
+  return success && on_wow64;
+#endif
+}
+/**
+ * Wrapper for executing a shellcommand in windows.
+ * 
+ * @param command - the command + parameters to execute
+ * @return * exitcode of the program executed, 
+ *         * EINVAL (cmd/file not found)
+ *         * EPIPE (could not read STDOUT)
+ */
+static int
+execute_shellcommand (const char *command)
+{
+  FILE *pipe;
+
+  if ( (NULL == command) ||
+       (NULL == (pipe = _popen (command, "rt"))) )
+    return EINVAL;
+
+#if DEBUG
+  fprintf (stderr, "DEBUG: Command output: \n");
+  char output[LINE_LEN];
+  while (NULL != fgets (output, sizeof (output), pipe))
+    fprintf (stderr, "%s", output);
+#endif
+
+  return _pclose (pipe);
+}
+
+
+/**
+ * @brief Sets the IPv6-Address given in address on the interface dev
+ *
+ * @param address the IPv6-Address
+ * @param prefix_len the length of the network-prefix
+ */
+static int
+set_address6 (const char *address, unsigned long prefix_len)
+{
+  int ret = EINVAL;
+  char command[LINE_LEN];
+  struct sockaddr_in6 sa6;
+
+  /*
+   * parse the new address
+   */
+  memset (&sa6, 0, sizeof (struct sockaddr_in6));
+  sa6.sin6_family = AF_INET6;
+  if (1 != inet_pton (AF_INET6, address, &sa6.sin6_addr.s6_addr))
+    {
+      fprintf (stderr, "ERROR: Failed to parse address `%s': %s\n", address,
+               strerror (errno));
+      return -1;
+    }
+
+  /*
+   * prepare the command
+   */
+  snprintf (command, LINE_LEN,
+            "netsh interface ipv6 add address \"%s\" %s/%d store=active",
+            device_visible_name, address, prefix_len);
+  /*
+   * Set the address
+   */
+  ret = execute_shellcommand (command);
+
+  /* Did it work?*/
+  if (0 != ret)
+    fprintf (stderr, "FATAL: Setting IPv6 address failed: %s\n", strerror (ret));
+  return ret;
+}
+
+
+/**
+ * @brief Removes the IPv6-Address given in address from the interface dev
+ *
+ * @param dev the interface to remove
+ * @param address the IPv4-Address
+ * @param mask the netmask
+ */
+static void
+remove_address6 (const char *address)
+{
+  char command[LINE_LEN];
+  int ret = EINVAL;
+
+  // sanity checking was already done in set_address6
+  /*
+   * prepare the command
+   */
+  snprintf (command, LINE_LEN,
+            "netsh interface ipv6 delete address \"%s\" store=persistent",
+            device_visible_name, address);
+  /*
+   * Set the address
+   */
+  ret = execute_shellcommand (command);
+
+  /* Did it work?*/
+  if (0 != ret)
+    fprintf (stderr, "FATAL: removing IPv6 address failed: %s\n", strerror (ret));
+}
+
+
+/**
+ * @brief Sets the IPv4-Address given in address on the interface dev
+ *
+ * @param dev the interface to configure
+ * @param address the IPv4-Address
+ * @param mask the netmask
+ */
+static int
+set_address4 (const char *address, const char *mask)
+{
+  int ret = EINVAL;
+  char command[LINE_LEN];
+
+  struct sockaddr_in addr;
+  addr.sin_family = AF_INET;
+
+  /*
+   * Parse the address
+   */
+  if (1 != inet_pton (AF_INET, address, &addr.sin_addr.s_addr))
+    {
+      fprintf (stderr, "ERROR: Failed to parse address `%s': %s\n", address,
+               strerror (errno));
+      return -1;
+    }
+  // Set Device to Subnet-Mode? 
+  // do we really need tun.c:2925 ?
+
+  /*
+   * prepare the command
+   */
+  snprintf (command, LINE_LEN,
+            "netsh interface ipv4 add address \"%s\" %s %s store=active",
+            device_visible_name, address, mask);
+  /*
+   * Set the address
+   */
+  ret = execute_shellcommand (command);
+
+  /* Did it work?*/
+  if (0 != ret)
+    fprintf (stderr, "FATAL: Setting IPv4 address failed: %s\n", strerror (ret));
+  return ret;
+}
+
+
+/**
+ * @brief Removes the IPv4-Address given in address from the interface dev
+ *
+ * @param dev the interface to remove
+ * @param address the IPv4-Address
+ * @param mask the netmask
+ */
+static void
+remove_address4 (const char *address)
+{
+  char command[LINE_LEN];
+  int ret = EINVAL;
+
+  // sanity checking was already done in set_address4
+
+  /*
+   * prepare the command
+   */
+  snprintf (command, LINE_LEN,
+            "netsh interface ipv4 delete address \"%s\" gateway=all store=persistent",
+            device_visible_name, address);
+  /*
+   * Set the address
+   */
+  ret = execute_shellcommand (command);
+
+  /* Did it work?*/
+  if (0 != ret)
+    fprintf (stderr, "FATAL: removing IPv4 address failed: %s\n", strerror (ret));
+}
+
+
+/**
+ * Setup a new virtual interface to use for tunneling. 
+ * 
+ * @return: TRUE if setup was successful, else FALSE
+ */
+static BOOL
+setup_interface ()
+{
+  /*
+   * where to find our inf-file. (+ the "full" path, after windows found")
+   * 
+   * We do not directly input all the props here, because openvpn will update
+   * these details over time.
+   */
+  char inf_file_path[MAX_PATH];
+  char * temp_inf_filename;
+  char hwidlist[LINE_LEN + 4];
+  char class_name[128];
+  GUID class_guid;
+  int str_length = 0;
+
+  /** 
+   * Set the device's hardware ID and add it to a list.
+   * This information will later on identify this device in registry. 
+   */
+  strncpy (hwidlist, HARDWARE_ID, LINE_LEN);
+  /**
+   * this is kind of over-complicated, but allows keeps things independent of 
+   * how the openvpn-hwid is actually stored. 
+   * 
+   * A HWID list is double-\0 terminated and \0 separated
+   */
+  str_length = strlen (hwidlist) + 1;
+  strncpy (&hwidlist[str_length], secondary_hwid, LINE_LEN);
+  str_length += strlen (&hwidlist[str_length]) + 1;
+  
+  /** 
+   * Locate the inf-file, we need to store it somewhere where the system can
+   * find it. We need to pick the correct driver for win32/win64.
+   */
+  if (is_win64())
+    GetFullPathNameA (INF_FILE64, MAX_PATH, inf_file_path, &temp_inf_filename);
+  else
+    GetFullPathNameA (INF_FILE, MAX_PATH, inf_file_path, &temp_inf_filename);
+
+  fprintf (stderr, "INFO: Located our driver's .inf file at %s\n", inf_file_path);
+  /** 
+   * Bootstrap our device info using the drivers inf-file
+   */
+  if ( ! SetupDiGetINFClassA (inf_file_path,
+                            &class_guid,
+                            class_name, sizeof (class_name) / sizeof (char),
+                            NULL))
+    return FALSE;
+
+  /** 
+   * Collect all the other needed information... 
+   * let the system fill our this form 
+   */
+  DeviceInfo = SetupDiCreateDeviceInfoList (&class_guid, NULL);
+  if (DeviceInfo == INVALID_HANDLE_VALUE)
+    return FALSE;
+
+  DeviceNode.cbSize = sizeof (SP_DEVINFO_DATA);
+  if ( ! SetupDiCreateDeviceInfoA (DeviceInfo,
+                                 class_name,
+                                 &class_guid,
+                                 NULL,
+                                 0,
+                                 DICD_GENERATE_ID,
+                                 &DeviceNode))
+    return FALSE;
+
+  /* Deploy all the information collected into the registry */
+  if ( ! SetupDiSetDeviceRegistryPropertyA (DeviceInfo,
+                                          &DeviceNode,
+                                          SPDRP_HARDWAREID,
+                                          (LPBYTE) hwidlist,
+                                          str_length * sizeof (char)))
+    return FALSE;
+
+  /* Install our new class(=device) into the system */
+  if ( ! SetupDiCallClassInstaller (DIF_REGISTERDEVICE,
+                                  DeviceInfo,
+                                  &DeviceNode))
+    return FALSE;
+
+  /* This system call tends to take a while (several seconds!) on
+     "modern" Windoze systems */
+  if ( ! UpdateDriverForPlugAndPlayDevicesA (NULL,
+                                           secondary_hwid,
+                                           inf_file_path,
+                                           INSTALLFLAG_FORCE | INSTALLFLAG_NONINTERACTIVE,
+                                           NULL)) //reboot required? NEVER!
+    return FALSE;
+
+  fprintf (stderr, "DEBUG: successfully created a network device\n");
+  return TRUE;
+}
+
+
+/**
+ * Remove our new virtual interface to use for tunneling. 
+ * This function must be called AFTER setup_interface!
+ * 
+ * @return: TRUE if destruction was successful, else FALSE
+ */
+static BOOL
+remove_interface ()
+{
+  SP_REMOVEDEVICE_PARAMS remove;
+
+  if (INVALID_HANDLE_VALUE == DeviceInfo)
+    return FALSE;
+
+  remove.ClassInstallHeader.cbSize = sizeof (SP_CLASSINSTALL_HEADER);
+  remove.HwProfile = 0;
+  remove.Scope = DI_REMOVEDEVICE_GLOBAL;
+  remove.ClassInstallHeader.InstallFunction = DIF_REMOVE;
+  /*
+   * 1. Prepare our existing device information set, and place the 
+   *    uninstall related information into the structure
+   */
+  if ( ! SetupDiSetClassInstallParamsA (DeviceInfo,
+                                      (PSP_DEVINFO_DATA) & DeviceNode,
+                                      &remove.ClassInstallHeader,
+                                      sizeof (remove)))
+    return FALSE;
+  /*
+   * 2. Uninstall the virtual interface using the class installer
+   */
+  if ( ! SetupDiCallClassInstaller (DIF_REMOVE,
+                                  DeviceInfo,
+                                  (PSP_DEVINFO_DATA) & DeviceNode))
+    return FALSE;
+
+  SetupDiDestroyDeviceInfoList (DeviceInfo);
+  
+  fprintf (stderr, "DEBUG: removed interface successfully\n");
+
+  return TRUE;
+}
+
+
+/**
+ * Do all the lookup necessary to retrieve the inteface's actual name
+ * off the registry. 
+ * 
+ * @return: TRUE if we were able to lookup the interface's name, else FALSE
+ */
+static BOOL
+resolve_interface_name ()
+{
+  SP_DEVINFO_LIST_DETAIL_DATA device_details;
+  char pnp_instance_id [MAX_DEVICE_ID_LEN];
+  HKEY adapter_key_handle;
+  LONG status;
+  DWORD len;
+  int i = 0;
+  int retrys;
+  BOOL retval = FALSE;
+  char adapter[] = INTERFACE_REGISTRY_LOCATION;
+
+  /* We can obtain the PNP instance ID from our setupapi handle */
+  device_details.cbSize = sizeof (device_details);
+  if (CR_SUCCESS != CM_Get_Device_ID_ExA (DeviceNode.DevInst,
+                                          (PCHAR) pnp_instance_id,
+                                          MAX_DEVICE_ID_LEN,
+                                          0, //must be 0
+                                          NULL)) //hMachine, we are local
+    return FALSE;
+  
+  fprintf (stderr, "DEBUG: Resolving interface name for network device %s\n",pnp_instance_id);
+
+  /* Registry is incredibly slow, retry for up to 30 seconds to allow registry to refresh */
+  for (retrys = 0; retrys < 120 && !retval; retrys++)
+    {
+      /* sleep for 250ms*/
+      Sleep (250);
+
+      /* Now we can use this ID to locate the correct networks interface in registry */
+      if (ERROR_SUCCESS != RegOpenKeyExA (
+                                          HKEY_LOCAL_MACHINE,
+                                          adapter,
+                                          0,
+                                          KEY_READ,
+                                          &adapter_key_handle))
+        return FALSE;
+
+      /* Of course there is a multitude of entries here, with arbitrary names, 
+       * thus we need to iterate through there.
+       */
+      while (!retval)
+        {
+          char instance_key[256];
+          char query_key [256];
+          HKEY instance_key_handle;
+          char pnpinstanceid_name[] = "PnpInstanceID";
+          char pnpinstanceid_value[256];
+          char adaptername_name[] = "Name";
+          DWORD data_type;
+
+          len = 256 * sizeof (char);
+          /* optain a subkey of {4D36E972-E325-11CE-BFC1-08002BE10318} */
+          status = RegEnumKeyExA (
+                                  adapter_key_handle,
+                                  i,
+                                  instance_key,
+                                  &len,
+                                  NULL,
+                                  NULL,
+                                  NULL,
+                                  NULL);
+
+          /* this may fail due to one of two reasons: 
+           * we are at the end of the list*/
+          if (ERROR_NO_MORE_ITEMS == status)
+            break;
+          // * we found a broken registry key, continue with the next key.
+          if (ERROR_SUCCESS != status)
+            goto cleanup;
+
+          /* prepare our new query string: */
+          snprintf (query_key, 256, "%s\\%s\\Connection",
+                    adapter,
+                    instance_key);
+
+          /* look inside instance_key\\Connection */
+          if (ERROR_SUCCESS != RegOpenKeyExA (
+                                  HKEY_LOCAL_MACHINE,
+                                  query_key,
+                                  0,
+                                  KEY_READ,
+                                  &instance_key_handle))
+            goto cleanup;
+
+          /* now, read our PnpInstanceID */
+          len = sizeof (pnpinstanceid_value);
+          status = RegQueryValueExA (instance_key_handle,
+                                     pnpinstanceid_name,
+                                     NULL, //reserved, always NULL according to MSDN
+                                     &data_type,
+                                     (LPBYTE) pnpinstanceid_value,
+                                     &len);
+
+          if (status != ERROR_SUCCESS || data_type != REG_SZ)
+            goto cleanup;
+
+          /* compare the value we got to our devices PNPInstanceID*/
+          if (0 != strncmp (pnpinstanceid_value, pnp_instance_id,
+                            sizeof (pnpinstanceid_value) / sizeof (char)))
+            goto cleanup;
+
+          len = sizeof (device_visible_name);
+          status = RegQueryValueExA (
+                                     instance_key_handle,
+                                     adaptername_name,
+                                     NULL, //reserved, always NULL according to MSDN
+                                     &data_type,
+                                     (LPBYTE) device_visible_name,
+                                     &len);
+
+          if (status != ERROR_SUCCESS || data_type != REG_SZ)
+            goto cleanup;
+
+          /* 
+           * we have successfully found OUR instance, 
+           * save the device GUID before exiting
+           */
+
+          strncpy (device_guid, instance_key, 256);
+          retval = TRUE;
+          fprintf (stderr, "DEBUG: Interface Name lookup succeeded on retry %d, got \"%s\" %s\n", retrys, device_visible_name, device_guid);
+
+cleanup:
+          RegCloseKey (instance_key_handle);
+
+          ++i;
+        }
+
+      RegCloseKey (adapter_key_handle);
+    }
+  return retval;
+}
+
+
+/**
+ * Determines the version of the installed TAP32 driver and checks if it's sufficiently new for GNUNET
+ * 
+ * @param handle the handle to our tap device
+ * @return TRUE if the version is sufficient, else FALSE
+ */
+static BOOL
+check_tapw32_version (HANDLE handle)
+{
+  ULONG version[3];
+  DWORD len;
+  memset (&(version), 0, sizeof (version));
+
+  if (DeviceIoControl (handle, TAP_WIN_IOCTL_GET_VERSION,
+                       &version, sizeof (version),
+                       &version, sizeof (version), &len, NULL))
+      fprintf (stderr, "INFO: TAP-Windows Driver Version %d.%d %s\n",
+               (int) version[0],
+               (int) version[1],
+               (version[2] ? "(DEBUG)" : ""));
+
+  if ((version[0] != TAP_WIN_MIN_MAJOR) ||
+      (version[1] < TAP_WIN_MIN_MINOR )){
+      fprintf (stderr, "FATAL:  This version of gnunet requires a TAP-Windows driver that is at least version %d.%d\n",
+               TAP_WIN_MIN_MAJOR,
+               TAP_WIN_MIN_MINOR);
+      return FALSE;
+    }
+      
+  return TRUE;
+}
+
+
+/**
+ * Creates a tun-interface called dev;
+ *
+ * @return the fd to the tun or -1 on error
+ */
+static HANDLE
+init_tun ()
+{
+  char device_path[256];
+  HANDLE handle;
+
+  if (! setup_interface ())
+    {
+      errno = ENODEV;
+      return INVALID_HANDLE_VALUE;
+    }
+
+  if (! resolve_interface_name ())
+    {
+      errno = ENODEV;
+      return INVALID_HANDLE_VALUE;
+    }
+
+  /* Open Windows TAP-Windows adapter */
+  snprintf (device_path, sizeof (device_path), "%s%s%s",
+            USERMODEDEVICEDIR,
+            device_guid,
+            TAP_WIN_SUFFIX);
+
+  handle = CreateFile (
+                       device_path,
+                       GENERIC_READ | GENERIC_WRITE,
+                       0, /* was: FILE_SHARE_READ */
+                       0,
+                       OPEN_EXISTING,
+                       FILE_ATTRIBUTE_SYSTEM | FILE_FLAG_OVERLAPPED,
+                       0
+                       );
+
+  if (INVALID_HANDLE_VALUE == handle)
+    {
+      fprintf (stderr, "FATAL: CreateFile failed on TAP device: %s\n", device_path);
+      return handle;
+    }
+
+  /* get driver version info */
+  if (! check_tapw32_version (handle))
+    {
+      CloseHandle (handle);
+      return INVALID_HANDLE_VALUE;
+    }
+
+  /* TODO (opt?): get MTU-Size */
+
+  fprintf (stderr, "DEBUG: successfully opened TAP device\n");
+  return handle;
+}
+
+
+/**
+ * Brings a TAP device up and sets it to connected state.
+ * 
+ * @param handle the handle to our TAP device 
+ * @return True if the operation succeeded, else false
+ */
+static BOOL
+tun_up (HANDLE handle)
+{
+  ULONG status = TRUE;
+  DWORD len;
+  if (! DeviceIoControl (handle, TAP_WIN_IOCTL_SET_MEDIA_STATUS,
+                        &status, sizeof (status),
+                        &status, sizeof (status), &len, NULL))
+    {
+      fprintf (stderr, "FATAL: TAP driver ignored request to UP interface (DeviceIoControl call)\n");
+      return FALSE;
+    }
+
+  /* Wait for the device to go UP, might take some time. */
+  Sleep (TAP32_POSTUP_WAITTIME * 1000);
+  fprintf (stderr, "DEBUG: successfully set TAP device to UP\n");
+
+  return TRUE;
+}
+
+
+/**
+ * Attempts to read off an input facility (tap or named pipe) in overlapped mode.
+ * 
+ * 1. 
+ * If the input facility is in IOSTATE_READY, it will issue a new read operation to the
+ * input handle. Then it goes into IOSTATE_QUEUED state. 
+ * In case the read succeeded instantly the input facility enters 3.
+ * 
+ * 2. 
+ * If the input facility is in IOSTATE_QUEUED state, it will check if the queued read has finished already.
+ * If it has finished, go to state 3.
+ * If it has failed, set IOSTATE_FAILED
+ * 
+ * 3.
+ * If the output facility is in state IOSTATE_READY, the read-buffer is copied to the output buffer.
+ *   The input facility enters state IOSTATE_READY
+ *   The output facility enters state IOSTATE_READY
+ * If the output facility is in state IOSTATE_QUEUED, the input facility enters IOSTATE_WAITING
+ * 
+ * IOSTATE_WAITING is reset by the output facility, once it has completed.
+ * 
+ * @param input_facility input named pipe or file to work with.
+ * @param output_facility output pipe or file to hand over data to.
+ * @return false if an event reset was impossible (OS error), else true
+ */
+static BOOL
+attempt_read_tap (struct io_facility * input_facility,
+                  struct io_facility * output_facility)
+{
+  struct GNUNET_MessageHeader * hdr;
+  unsigned short size;
+  
+  switch (input_facility->facility_state)
+    {
+    case IOSTATE_READY:
+      { 
+        if (! ResetEvent (input_facility->overlapped.hEvent))
+          {
+            return FALSE;
+          }
+
+        input_facility->buffer_size = 0;
+
+        /* Check how the task is handled */
+        if (ReadFile (input_facility->handle,
+                      input_facility->buffer,
+                      sizeof (input_facility->buffer) - sizeof (struct GNUNET_MessageHeader),
+                      &input_facility->buffer_size,
+                      &input_facility->overlapped))
+          {/* async event processed immediately*/
+
+            /* reset event manually*/
+            if (! SetEvent (input_facility->overlapped.hEvent))
+              return FALSE;
+            
+            fprintf (stderr, "DEBUG: tap read succeeded immediately\n");
+            
+            /* we successfully read something from the TAP and now need to
+             * send it our via STDOUT. Is that possible at the moment? */
+            if ((IOSTATE_READY == output_facility->facility_state ||
+                 IOSTATE_WAITING == output_facility->facility_state)
+                && (0 < input_facility->buffer_size))
+              { /* hand over this buffers content and apply message header for gnunet */
+                hdr = (struct GNUNET_MessageHeader *) output_facility->buffer;
+                size = input_facility->buffer_size + sizeof (struct GNUNET_MessageHeader);
+                
+                memcpy (output_facility->buffer + sizeof (struct GNUNET_MessageHeader),
+                        input_facility->buffer,
+                        input_facility->buffer_size);
+
+                output_facility->buffer_size = size;
+                hdr->size = htons (size);
+                hdr->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
+                output_facility->facility_state = IOSTATE_READY;
+              }
+            else if (0 < input_facility->buffer_size)
+                /* If we have have read our buffer, wait for our write-partner*/
+                input_facility->facility_state = IOSTATE_WAITING;
+          }
+        else /* operation was either queued or failed*/
+          {
+            int err = GetLastError ();
+            if (ERROR_IO_PENDING == err)
+              { /* operation queued */
+                input_facility->facility_state = IOSTATE_QUEUED;
+              }
+            else
+              { /* error occurred, let the rest of the elements finish */
+                input_facility->path_open = FALSE;
+                input_facility->facility_state = IOSTATE_FAILED;
+                if (IOSTATE_WAITING == output_facility->facility_state)
+                  output_facility->path_open = FALSE;
+
+                fprintf (stderr, "FATAL: Read from handle failed, allowing write to finish\n");
+              }
+          }
+      }
+      return TRUE;
+      // We are queued and should check if the read has finished
+    case IOSTATE_QUEUED:
+      {
+        // there was an operation going on already, check if that has completed now.
+
+        if (GetOverlappedResult (input_facility->handle,
+                                 &input_facility->overlapped,
+                                 &input_facility->buffer_size,
+                                 FALSE))
+          {/* successful return for a queued operation */
+            if (! ResetEvent (input_facility->overlapped.hEvent))
+              return FALSE;
+
+            fprintf (stderr, "DEBUG: tap read succeeded delayed\n");
+            
+            /* we successfully read something from the TAP and now need to
+             * send it our via STDOUT. Is that possible at the moment? */
+            if ((IOSTATE_READY == output_facility->facility_state ||
+                 IOSTATE_WAITING == output_facility->facility_state)
+                && 0 < input_facility->buffer_size)
+              { /* hand over this buffers content and apply message header for gnunet */
+                hdr = (struct GNUNET_MessageHeader *) output_facility->buffer;
+                size = input_facility->buffer_size + sizeof (struct GNUNET_MessageHeader);
+                
+                memcpy (output_facility->buffer + sizeof (struct GNUNET_MessageHeader),
+                        input_facility->buffer,
+                        input_facility->buffer_size);
+
+                output_facility->buffer_size = size;
+                hdr->size = htons(size);
+                hdr->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
+                output_facility->facility_state = IOSTATE_READY;
+                input_facility->facility_state = IOSTATE_READY;
+              }
+            else if (0 < input_facility->buffer_size)
+              { /* If we have have read our buffer, wait for our write-partner*/
+                input_facility->facility_state = IOSTATE_WAITING;
+                // TODO: shall we attempt to fill our buffer or should we wait for our write-partner to finish?
+              }
+          }
+        else
+          { /* operation still pending/queued or failed? */
+            int err = GetLastError ();
+            if ((ERROR_IO_INCOMPLETE != err) && (ERROR_IO_PENDING != err))
+              { /* error occurred, let the rest of the elements finish */
+                input_facility->path_open = FALSE;
+                input_facility->facility_state = IOSTATE_FAILED;
+                if (IOSTATE_WAITING == output_facility->facility_state)
+                  output_facility->path_open = FALSE;
+                fprintf (stderr, "FATAL: Read from handle failed, allowing write to finish\n");
+              }
+          }
+      }
+      return TRUE;
+    case IOSTATE_RESUME:
+      hdr = (struct GNUNET_MessageHeader *) output_facility->buffer;
+      size = input_facility->buffer_size + sizeof (struct GNUNET_MessageHeader);
+
+      memcpy (output_facility->buffer + sizeof (struct GNUNET_MessageHeader),
+              input_facility->buffer,
+              input_facility->buffer_size);
+
+      output_facility->buffer_size = size;
+      hdr->size = htons (size);
+      hdr->type = htons (GNUNET_MESSAGE_TYPE_VPN_HELPER);
+      output_facility->facility_state = IOSTATE_READY;
+      input_facility->facility_state = IOSTATE_READY;
+      return TRUE;
+    default:
+      return TRUE;
+    }
+}
+
+
+/**
+ * Attempts to read off an input facility (tap or named pipe) in overlapped mode.
+ * 
+ * 1. 
+ * If the input facility is in IOSTATE_READY, it will issue a new read operation to the
+ * input handle. Then it goes into IOSTATE_QUEUED state. 
+ * In case the read succeeded instantly the input facility enters 3.
+ * 
+ * 2. 
+ * If the input facility is in IOSTATE_QUEUED state, it will check if the queued read has finished already.
+ * If it has finished, go to state 3.
+ * If it has failed, set IOSTATE_FAILED
+ * 
+ * 3.
+ * If the facility is finished with ready
+ *   The read-buffer is copied to the output buffer, except for the GNUNET_MessageHeader.
+ *   The input facility enters state IOSTATE_READY
+ *   The output facility enters state IOSTATE_READY
+ * If the output facility is in state IOSTATE_QUEUED, the input facility enters IOSTATE_WAITING
+ * 
+ * IOSTATE_WAITING is reset by the output facility, once it has completed.
+ * 
+ * @param input_facility input named pipe or file to work with.
+ * @param output_facility output pipe or file to hand over data to.
+ * @return false if an event reset was impossible (OS error), else true
+ */
+static BOOL
+attempt_read_stdin (struct io_facility * input_facility,
+                    struct io_facility * output_facility)
+{
+  struct GNUNET_MessageHeader * hdr;
+  
+  switch (input_facility->facility_state)
+    {
+    case IOSTATE_READY:
+      {
+        input_facility->buffer_size = 0;
+        
+partial_read_iostate_ready:
+        if (! ResetEvent (input_facility->overlapped.hEvent))
+          return FALSE;
+       
+        /* Check how the task is handled */
+        if (ReadFile (input_facility->handle,
+                           input_facility->buffer + input_facility->buffer_size,
+                           sizeof (input_facility->buffer) - input_facility->buffer_size,
+                           &input_facility->buffer_size_processed,
+                           &input_facility->overlapped))
+          {/* async event processed immediately*/
+            hdr = (struct GNUNET_MessageHeader *) input_facility->buffer;
+
+            /* reset event manually*/
+            if (!SetEvent (input_facility->overlapped.hEvent))
+              return FALSE;
+
+            fprintf (stderr, "DEBUG: stdin read succeeded immediately\n");
+            input_facility->buffer_size += input_facility->buffer_size_processed;
+
+            if (ntohs (hdr->type) != GNUNET_MESSAGE_TYPE_VPN_HELPER ||
+                ntohs (hdr->size) > sizeof (input_facility->buffer))
+              {
+                fprintf (stderr, "WARNING: Protocol violation, got GNUnet Message type %h, size %h\n", ntohs (hdr->type), ntohs (hdr->size));
+                input_facility->facility_state = IOSTATE_READY;
+                return TRUE;
+              }
+            /* we got the a part of a packet */
+            if (ntohs (hdr->size) > input_facility->buffer_size)
+              goto partial_read_iostate_ready;
+
+            /* have we read more than 0 bytes of payload? (sizeread > header)*/
+            if (input_facility->buffer_size > sizeof (struct GNUNET_MessageHeader) &&
+                ((IOSTATE_READY == output_facility->facility_state) ||
+                 (IOSTATE_WAITING == output_facility->facility_state)))
+              {/* we successfully read something from the TAP and now need to
+             * send it our via STDOUT. Is that possible at the moment? */
+
+                /* hand over this buffers content and strip gnunet message header */
+                memcpy (output_facility->buffer,
+                        input_facility->buffer + sizeof (struct GNUNET_MessageHeader),
+                        input_facility->buffer_size - sizeof (struct GNUNET_MessageHeader));
+                output_facility->buffer_size = input_facility->buffer_size - sizeof (struct GNUNET_MessageHeader);
+                output_facility->facility_state = IOSTATE_READY;
+                input_facility->facility_state = IOSTATE_READY;
+              }
+            else if (input_facility->buffer_size > sizeof (struct GNUNET_MessageHeader))
+              /* If we have have read our buffer, wait for our write-partner*/
+              input_facility->facility_state = IOSTATE_WAITING;
+            else /* we read nothing */
+              input_facility->facility_state = IOSTATE_READY;
+          } 
+        else /* operation was either queued or failed*/
+          {
+            int err = GetLastError ();
+            if (ERROR_IO_PENDING == err) /* operation queued */
+                input_facility->facility_state = IOSTATE_QUEUED;
+            else
+              { /* error occurred, let the rest of the elements finish */
+                input_facility->path_open = FALSE;
+                input_facility->facility_state = IOSTATE_FAILED;
+                if (IOSTATE_WAITING == output_facility->facility_state)
+                  output_facility->path_open = FALSE;
+
+                fprintf (stderr, "FATAL: Read from handle failed, allowing write to finish\n");
+              }
+          }
+      }
+      return TRUE;
+      // We are queued and should check if the read has finished
+    case IOSTATE_QUEUED:
+      {
+        // there was an operation going on already, check if that has completed now.
+        if (GetOverlappedResult (input_facility->handle,
+                                 &input_facility->overlapped,
+                                 &input_facility->buffer_size_processed,
+                                 FALSE))
+          {/* successful return for a queued operation */
+            hdr = (struct GNUNET_MessageHeader *) input_facility->buffer;
+            
+            if (! ResetEvent (input_facility->overlapped.hEvent))
+              return FALSE;
+            
+            fprintf (stderr, "DEBUG: stdin read succeeded delayed\n");
+            input_facility->buffer_size += input_facility->buffer_size_processed;
+            
+            if ((ntohs (hdr->type) != GNUNET_MESSAGE_TYPE_VPN_HELPER) ||
+                (ntohs (hdr->size) > sizeof (input_facility->buffer)))
+              {
+                fprintf (stderr, "WARNING: Protocol violation, got GNUnet Message type %h, size %h\n", ntohs (hdr->type), ntohs (hdr->size));
+                input_facility->facility_state = IOSTATE_READY;
+                return TRUE;
+              }
+            /* we got the a part of a packet */
+            if (ntohs (hdr->size) > input_facility->buffer_size );
+              goto partial_read_iostate_ready;
+
+            /* we successfully read something from the TAP and now need to
+             * send it our via STDOUT. Is that possible at the moment? */
+            if ((IOSTATE_READY == output_facility->facility_state ||
+                 IOSTATE_WAITING == output_facility->facility_state)
+                && input_facility->buffer_size > sizeof(struct GNUNET_MessageHeader))
+              { /* hand over this buffers content and strip gnunet message header */
+                memcpy (output_facility->buffer,
+                        input_facility->buffer + sizeof(struct GNUNET_MessageHeader),
+                        input_facility->buffer_size - sizeof(struct GNUNET_MessageHeader));
+                output_facility->buffer_size = input_facility->buffer_size - sizeof(struct GNUNET_MessageHeader);
+                output_facility->facility_state = IOSTATE_READY;
+                input_facility->facility_state = IOSTATE_READY;
+              }
+            else if (input_facility->buffer_size > sizeof(struct GNUNET_MessageHeader))
+              input_facility->facility_state = IOSTATE_WAITING;
+            else
+              input_facility->facility_state = IOSTATE_READY;
+          }
+        else
+          { /* operation still pending/queued or failed? */
+            int err = GetLastError ();
+            if ((ERROR_IO_INCOMPLETE != err) && (ERROR_IO_PENDING != err))
+              { /* error occurred, let the rest of the elements finish */
+                input_facility->path_open = FALSE;
+                input_facility->facility_state = IOSTATE_FAILED;
+                if (IOSTATE_WAITING == output_facility->facility_state)
+                  output_facility->path_open = FALSE;
+                fprintf (stderr, "FATAL: Read from handle failed, allowing write to finish\n");
+              }
+          }
+      }
+      return TRUE;
+    case IOSTATE_RESUME: /* Our buffer was filled already but our write facility was busy. */
+      memcpy (output_facility->buffer,
+              input_facility->buffer + sizeof (struct GNUNET_MessageHeader),
+              input_facility->buffer_size - sizeof (struct GNUNET_MessageHeader));
+      output_facility->buffer_size = input_facility->buffer_size - sizeof (struct GNUNET_MessageHeader);
+      output_facility->facility_state = IOSTATE_READY;
+      input_facility->facility_state = IOSTATE_READY;
+      return TRUE;
+    default:
+      return TRUE;
+    }
+}
+
+
+/**
+ * Attempts to write to an output facility (tap or named pipe) in overlapped mode.
+ *
+ * TODO: high level description
+ * 
+ * @param output_facility output pipe or file to hand over data to.
+ * @param input_facility input named pipe or file to work with.
+ * @return false if an event reset was impossible (OS error), else true
+ */
+static BOOL
+attempt_write (struct io_facility * output_facility,
+               struct io_facility * input_facility)
+{
+  switch (output_facility->facility_state)
+    {
+    case IOSTATE_READY:
+      output_facility->buffer_size_written = 0;
+      
+continue_partial_write:
+      if (! ResetEvent (output_facility->overlapped.hEvent))
+        return FALSE;
+
+      /* Check how the task was handled */
+      if (WriteFile (output_facility->handle,
+                          output_facility->buffer + output_facility->buffer_size_written,
+                          output_facility->buffer_size - output_facility->buffer_size_written,
+                          &output_facility->buffer_size_processed,
+                          &output_facility->overlapped))
+        {/* async event processed immediately*/
+
+          fprintf (stderr, "DEBUG: write succeeded immediately\n");
+          output_facility->buffer_size_written += output_facility->buffer_size_processed;
+          
+          /* reset event manually*/
+          if (! SetEvent (output_facility->overlapped.hEvent))
+            return FALSE;
+
+          /* partial write */
+          if (output_facility->buffer_size_written < output_facility->buffer_size)
+            goto continue_partial_write;
+          
+          /* we are now waiting for our buffer to be filled*/
+          output_facility->facility_state = IOSTATE_WAITING;
+
+          /* we successfully wrote something and now need to reset our reader */
+          if (IOSTATE_WAITING == input_facility->facility_state)
+            input_facility->facility_state = IOSTATE_RESUME;
+          else if (IOSTATE_FAILED == input_facility->facility_state)
+            output_facility->path_open = FALSE;
+        }
+      else /* operation was either queued or failed*/
+        {
+          int err = GetLastError ();
+          if (ERROR_IO_PENDING == err)
+            { /* operation queued */
+              output_facility->facility_state = IOSTATE_QUEUED;
+            }
+          else
+            { /* error occurred, close this path */
+              output_facility->path_open = FALSE;
+              output_facility->facility_state = IOSTATE_FAILED;
+              fprintf (stderr, "FATAL: Write to handle failed, exiting\n");
+            }
+        }
+      return TRUE;
+    case IOSTATE_QUEUED:
+      // there was an operation going on already, check if that has completed now.
+      
+      if (GetOverlappedResult (output_facility->handle,
+                                    &output_facility->overlapped,
+                                    &output_facility->buffer_size_processed,
+                                    FALSE))
+        {/* successful return for a queued operation */
+          if (! ResetEvent (output_facility->overlapped.hEvent))
+            return FALSE;
+          
+          fprintf (stderr, "DEBUG: write succeeded delayed\n");
+          output_facility->buffer_size_written += output_facility->buffer_size_processed;
+          
+          /* partial write */
+          if (output_facility->buffer_size_written < output_facility->buffer_size)
+            goto continue_partial_write;
+          
+          /* we are now waiting for our buffer to be filled*/
+          output_facility->facility_state = IOSTATE_WAITING;
+          
+          /* we successfully wrote something and now need to reset our reader */
+          if (IOSTATE_WAITING == input_facility->facility_state)
+            input_facility->facility_state = IOSTATE_RESUME;
+          else if (IOSTATE_FAILED == input_facility->facility_state)
+            output_facility->path_open = FALSE;
+        }
+      else
+        { /* operation still pending/queued or failed? */
+          int err = GetLastError ();
+          if ((ERROR_IO_INCOMPLETE != err) && (ERROR_IO_PENDING != err))
+            { /* error occurred, close this path */
+              output_facility->path_open = FALSE;
+              output_facility->facility_state = IOSTATE_FAILED;
+              fprintf (stderr, "FATAL: Write to handle failed, exiting\n");
+            }
+        }
+    default: 
+      return TRUE;
+    }
+}
+
+
+/**
+ * Initialize a overlapped structure
+ * 
+ * @param elem the element to initilize
+ * @param initial_state the initial state for this instance
+ * @param signaled if the hEvent created should default to signaled or not
+ * @return true on success, else false
+ */
+static BOOL
+initialize_io_facility (struct io_facility * elem,
+                        int initial_state,
+                        BOOL signaled)
+{
+  elem->path_open = TRUE;
+  elem->handle = INVALID_HANDLE_VALUE;
+  elem->facility_state = initial_state;
+  elem->buffer_size = 0;
+  elem->overlapped.hEvent = CreateEvent (NULL, TRUE, signaled, NULL);
+  if (NULL == elem->overlapped.hEvent)
+    return FALSE;
+
+  return TRUE;
+}
+
+
+/**
+ * Start forwarding to and from the tunnel.
+ *
+ * @param fd_tun tunnel FD
+ */
+static void
+run (HANDLE tap_handle)
+{
+  /* IO-Facility for reading from our virtual interface */
+  struct io_facility tap_read;
+  /* IO-Facility for writing to our virtual interface */
+  struct io_facility tap_write;
+  /* IO-Facility for reading from stdin */
+  struct io_facility std_in;
+  /* IO-Facility for writing to stdout */
+  struct io_facility std_out;
+
+  HANDLE parent_std_in_handle = GetStdHandle (STD_INPUT_HANDLE);
+  HANDLE parent_std_out_handle = GetStdHandle (STD_OUTPUT_HANDLE);
+
+  /* tun up: */
+  /* we do this HERE and not beforehand (in init_tun()), in contrast to openvpn
+   * to remove the need to flush the arp cache, handle DHCP and wrong IPs.
+   *  
+   * DHCP and such are all features we will never use in gnunet afaik.
+   * But for openvpn those are essential.
+   */
+  if (! tun_up (tap_handle))
+    return;
+
+  /* Initialize our overlapped IO structures*/
+  if (! (initialize_io_facility (&tap_read, IOSTATE_READY, FALSE)
+        && initialize_io_facility (&tap_write, IOSTATE_WAITING, TRUE)
+        && initialize_io_facility (&std_in, IOSTATE_READY, FALSE)
+        && initialize_io_facility (&std_out, IOSTATE_WAITING, TRUE)))
+    goto teardown_final;
+
+  /* Handles for STDIN and STDOUT */
+  tap_read.handle = tap_handle;
+  tap_write.handle = tap_handle;
+
+#ifdef DEBUG_TO_CONSOLE
+  /* Debug output to console STDIN/STDOUT*/
+  std_in.handle = parent_std_in_handle;
+  std_out.handle = parent_std_out_handle;
+  
+#else
+  fprintf (stderr, "DEBUG: reopening stdin/out for overlapped IO\n");
+  /* 
+   * Find out the types of our handles. 
+   * This part is a problem, because in windows we need to handle files, 
+   * pipes and the console differently.
+   */
+  if ((FILE_TYPE_PIPE != GetFileType (parent_std_in_handle)) ||
+      (FILE_TYPE_PIPE != GetFileType (parent_std_out_handle)))
+    {
+      fprintf (stderr, "ERROR: stdin/stdout must be named pipes\n");
+      goto teardown;
+    }
+
+  std_in.handle = ReOpenFile (parent_std_in_handle,
+                              GENERIC_READ,
+                              FILE_SHARE_WRITE | FILE_SHARE_READ,
+                              FILE_FLAG_OVERLAPPED);
+
+  if (INVALID_HANDLE_VALUE == std_in.handle)
+    {
+      fprintf (stderr, "FATAL: Could not reopen stdin for in overlapped mode, has to be a named pipe\n");
+      goto teardown;
+    }
+
+  std_out.handle = ReOpenFile (parent_std_out_handle,
+                               GENERIC_WRITE,
+                               FILE_SHARE_READ,
+                               FILE_FLAG_OVERLAPPED);
+
+  if (INVALID_HANDLE_VALUE == std_out.handle)
+    {
+      fprintf (stderr, "FATAL: Could not reopen stdout for in overlapped mode, has to be a named pipe\n");
+      goto teardown;
+    }
+#endif
+  
+  fprintf (stderr, "DEBUG: mainloop has begun\n");
+  
+  while (std_out.path_open || tap_write.path_open)
+    {
+      /* perform READ from stdin if possible */
+      if (std_in.path_open && (! attempt_read_stdin (&std_in, &tap_write)))
+        break;
+
+      /* perform READ from tap if possible */
+      if (tap_read.path_open && (! attempt_read_tap (&tap_read, &std_out)))
+        break;
+
+      /* perform WRITE to tap if possible */
+      if (tap_write.path_open && (! attempt_write (&tap_write, &std_in)))
+        break;
+
+      /* perform WRITE to STDOUT if possible */
+      if (std_out.path_open && (! attempt_write (&std_out, &tap_read)))
+        break;
+    }
+
+teardown:
+
+  fprintf (stderr, "DEBUG: teardown initiated\n");
+      
+  CancelIo (tap_handle);
+  CancelIo (std_in.handle);
+  CancelIo (std_out.handle);
+
+teardown_final:
+      
+  CloseHandle (tap_handle);
+}
+
+
+/**
+ * Open VPN tunnel interface.
+ *
+ * @param argc must be 6
+ * @param argv 0: binary name (gnunet-helper-vpn)
+ *             1: tunnel interface prefix (gnunet-vpn)
+ *             2: IPv6 address (::1), "-" to disable
+ *             3: IPv6 netmask length in bits (64), ignored if #2 is "-"
+ *             4: IPv4 address (1.2.3.4), "-" to disable
+ *             5: IPv4 netmask (255.255.0.0), ignored if #4 is "-"
+ */
+int
+main (int argc, char **argv)
+{
+  char hwid[LINE_LEN];
+  HANDLE handle;
+  int global_ret = 0;
+  BOOL have_ip4 = FALSE;
+  BOOL have_ip6 = FALSE;
+
+  if (6 != argc)
+    {
+      fprintf (stderr, "FATAL: must supply 5 arguments\nUsage:\ngnunet-helper-vpn <if name prefix> <address6 or \"-\"> <netbits6> <address4 or \"-\"> <netmask4>\n", argv[0]);
+      return 1;
+    }
+
+  strncpy (hwid, argv[1], LINE_LEN);
+  hwid[LINE_LEN - 1] = '\0';
+
+  /* 
+   * We use our PID for finding/resolving the control-panel name of our virtual 
+   * device. PIDs are (of course) unique at runtime, thus we can safely use it 
+   * as additional hardware-id for our device.
+   */
+  snprintf (secondary_hwid, LINE_LEN / 2, "%s-%d",
+            hwid,
+            _getpid ());
+
+  if (INVALID_HANDLE_VALUE == (handle = init_tun ()))
+    {
+      fprintf (stderr, "FATAL: could not initialize virtual-interface %s with IPv6 %s/%s and IPv4 %s/%s\n",
+               hwid,
+               argv[2],
+               argv[3],
+               argv[4],
+               argv[5]);
+      global_ret = -1;
+      goto cleanup;
+    }
+
+  fprintf (stderr, "DEBUG: Setting IPs, if needed\n");
+  if (0 != strcmp (argv[2], "-"))
+    {
+      const char *address = argv[2];
+      long prefix_len = atol (argv[3]);
+
+      if ((prefix_len < 1) || (prefix_len > 127))
+        {
+          fprintf (stderr, "FATAL: ipv6 prefix_len out of range\n");
+          global_ret = -1;
+          goto cleanup;
+        }
+
+      fprintf (stderr, "DEBUG: Setting IP6 address: %s/%d\n",address,prefix_len);
+      if (0 != (global_ret = set_address6 (address, prefix_len)))
+        goto cleanup;
+
+      have_ip6 = TRUE;
+    }
+
+  if (0 != strcmp (argv[4], "-"))
+    {
+      const char *address = argv[4];
+      const char *mask = argv[5];
+
+      fprintf (stderr, "DEBUG: Setting IP4 address: %s/%s\n",address,mask);
+      if (0 != (global_ret = set_address4 (address, mask)))
+        goto cleanup;
+
+      have_ip4 = TRUE;
+    }
+
+  run (handle);
+  global_ret = 0;
+cleanup:
+
+  if (have_ip4)
+    {
+      const char *address = argv[4];
+      fprintf (stderr, "DEBUG: Removing IP4 address\n");
+      remove_address4 (address);
+    }
+  if (have_ip6)
+    {
+      const char *address = argv[2];
+      fprintf (stderr, "DEBUG: Removing IP6 address\n");
+      remove_address6 (address);
+    }
+
+  fprintf (stderr, "DEBUG: removing interface\n");
+  remove_interface ();
+  fprintf (stderr, "DEBUG: graceful exit completed\n");
+
+  return global_ret;
+}