Merge remote-tracking branch 'dechamps/wintapver' into 1.1

diff --combined src/mingw/device.c
index 4b821df,e95878c..231a264
--- 1/src/mingw/device.c
--- 2/src/mingw/device.c
+++ b/src/mingw/device.c
@@@ -38,9 -38,7 +38,9 @@@ int device_fd = -1
  static HANDLE device_handle = INVALID_HANDLE_VALUE;
  static io_t device_read_io;
  static OVERLAPPED device_read_overlapped;
 +static OVERLAPPED device_write_overlapped;
  static vpn_packet_t device_read_packet;
 +static vpn_packet_t device_write_packet;
  char *device = NULL;
  char *iface = NULL;
  static char *device_info = NULL;
@@@ -177,6 -175,25 +177,25 @@@ static bool setup_device(void) 
                return false;
        }
  
+       /* Get version information from tap device */
+ 
+       {
+               ULONG info[3] = {0};
+               DWORD len;
+               if(!DeviceIoControl(device_handle, TAP_IOCTL_GET_VERSION, &info, sizeof info, &info, sizeof info, &len, NULL))
+                       logger(DEBUG_ALWAYS, LOG_WARNING, "Could not get version information from Windows tap device %s (%s): %s", device, iface, winerror(GetLastError()));
+               else {
+                       logger(DEBUG_ALWAYS, LOG_INFO, "TAP-Windows driver version: %lu.%lu%s", info[0], info[1], info[2] ? " (DEBUG)" : "");
+ 
+                       /* Warn if using >=9.21. This is because starting from 9.21, TAP-Win32 seems to use a different, less efficient write path. */
+                       if(info[0] == 9 && info[1] >= 21)
+                               logger(DEBUG_ALWAYS, LOG_WARNING,
+                                       "You are using the newer (>= 9.0.0.21, NDIS6) series of TAP-Win32 drivers. "
+                                       "Using these drivers with tinc is not recommanded as it can result in poor performance. "
+                                       "You might want to revert back to 9.0.0.9 instead.");
+               }
+       }
+ 
        /* Get MAC address from tap device */
  
        if(!DeviceIoControl(device_handle, TAP_IOCTL_GET_MAC, mymac.x, sizeof mymac.x, mymac.x, sizeof mymac.x, &len, 0)) {
@@@ -202,12 -219,8 +221,12 @@@ static void enable_device(void) 
        DWORD len;
        DeviceIoControl(device_handle, TAP_IOCTL_SET_MEDIA_STATUS, &status, sizeof status, &status, sizeof status, &len, NULL);
  
 -      io_add_event(&device_read_io, device_handle_read, NULL, CreateEvent(NULL, TRUE, FALSE, NULL));
 -      device_read_overlapped.hEvent = device_read_io.event;
 +      /* We don't use the write event directly, but GetOverlappedResult() does, internally. */
 +
 +      device_read_overlapped.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
 +      device_write_overlapped.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
 +
 +      io_add_event(&device_read_io, device_handle_read, NULL, device_read_overlapped.hEvent);
        device_issue_read();
  }
  
@@@ -216,22 -229,10 +235,22 @@@ static void disable_device(void) 
  
        io_del(&device_read_io);
        CancelIo(device_handle);
 +
 +      /* According to MSDN, CancelIo() does not necessarily wait for the operation to complete.
 +         To prevent race conditions, make sure the operation is complete
 +         before we close the event it's referencing. */
 +
 +      DWORD len;
 +      if(!GetOverlappedResult(device_handle, &device_read_overlapped, &len, TRUE) && GetLastError() != ERROR_OPERATION_ABORTED)
 +              logger(DEBUG_ALWAYS, LOG_ERR, "Could not wait for %s %s read to cancel: %s", device_info, device, winerror(GetLastError()));
 +      if(device_write_packet.len > 0 && !GetOverlappedResult(device_handle, &device_write_overlapped, &len, TRUE) && GetLastError() != ERROR_OPERATION_ABORTED)
 +              logger(DEBUG_ALWAYS, LOG_ERR, "Could not wait for %s %s write to cancel: %s", device_info, device, winerror(GetLastError()));
 +      device_write_packet.len = 0;
 +
        CloseHandle(device_read_overlapped.hEvent);
 +      CloseHandle(device_write_overlapped.hEvent);
  
        ULONG status = 0;
 -      DWORD len;
        DeviceIoControl(device_handle, TAP_IOCTL_SET_MEDIA_STATUS, &status, sizeof status, &status, sizeof status, &len, NULL);
  }
  
@@@ -249,29 -250,12 +268,29 @@@ static bool read_packet(vpn_packet_t *p
  
  static bool write_packet(vpn_packet_t *packet) {
        DWORD outlen;
 -      OVERLAPPED overlapped = {0};
  
        logger(DEBUG_TRAFFIC, LOG_DEBUG, "Writing packet of %d bytes to %s",
                           packet->len, device_info);
  
 -      if(!WriteFile(device_handle, DATA(packet), packet->len, &outlen, &overlapped)) {
 +      if(device_write_packet.len > 0) {
 +              /* Make sure the previous write operation is finished before we start the next one;
 +                 otherwise we end up with multiple write ops referencing the same OVERLAPPED structure,
 +                 which according to MSDN is a no-no. */
 +
 +              if(!GetOverlappedResult(device_handle, &device_write_overlapped, &outlen, FALSE)) {
 +                      int log_level = (GetLastError() == ERROR_IO_INCOMPLETE) ? DEBUG_TRAFFIC : DEBUG_ALWAYS;
 +                      logger(log_level, LOG_ERR, "Error while checking previous write to %s %s: %s", device_info, device, winerror(GetLastError()));
 +                      return false;
 +              }
 +      }
 +
 +      /* Copy the packet, since the write operation might still be ongoing after we return. */
 +
 +      memcpy(&device_write_packet, packet, sizeof *packet);
 +
 +      if(WriteFile(device_handle, DATA(&device_write_packet), device_write_packet.len, &outlen, &device_write_overlapped))
 +              device_write_packet.len = 0;
 +      else if (GetLastError() != ERROR_IO_PENDING) {
                logger(DEBUG_ALWAYS, LOG_ERR, "Error while writing to %s %s: %s", device_info, device, winerror(GetLastError()));
                return false;
        }