On Windows, don't cancel I/O when disabling the device.

[tinc] / src / mingw / device.c

diff --git a/src/mingw/device.c b/src/mingw/device.c
index 4b821df..dfdb964 100644 (file)
--- a/src/mingw/device.c
+++ b/src/mingw/device.c
@@ -101,6 +101,9 @@ static bool setup_device(void) {
        get_config_string(lookup_config(config_tree, "Device"), &device);
        get_config_string(lookup_config(config_tree, "Interface"), &iface);
 
+       if(device && iface)
+               logger(DEBUG_ALWAYS, LOG_WARNING, "Warning: both Device and Interface specified, results may not be as expected");
+
        /* Open registry and look for network adapters */
 
        if(RegOpenKeyEx(HKEY_LOCAL_MACHINE, NETWORK_CONNECTIONS_KEY, 0, KEY_READ, &key)) {
@@ -177,6 +180,25 @@ 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)) {
@@ -192,6 +214,9 @@ static bool setup_device(void) {
 
        logger(DEBUG_ALWAYS, LOG_INFO, "%s (%s) is a %s", device, iface, device_info);
 
+       device_read_overlapped.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
+       device_write_overlapped.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
+
        return true;
 }
 
@@ -204,9 +229,6 @@ static void enable_device(void) {
 
        /* 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();
 }
@@ -215,6 +237,19 @@ static void disable_device(void) {
        logger(DEBUG_ALWAYS, LOG_INFO, "Disabling %s", device_info);
 
        io_del(&device_read_io);
+
+       ULONG status = 0;
+       DWORD len;
+       DeviceIoControl(device_handle, TAP_IOCTL_SET_MEDIA_STATUS, &status, sizeof status, &status, sizeof status, &len, NULL);
+
+       /* Note that we don't try to cancel ongoing I/O here - we just stop listening.
+          This is because some TAP-Win32 drivers don't seem to handle cancellation very well,
+          especially when combined with other events such as the computer going to sleep - cases
+          were observed where the GetOverlappedResult() would just block indefinitely and never
+          return in that case. */
+}
+
+static void close_device(void) {
        CancelIo(device_handle);
 
        /* According to MSDN, CancelIo() does not necessarily wait for the operation to complete.
@@ -231,11 +266,6 @@ static void disable_device(void) {
        CloseHandle(device_read_overlapped.hEvent);
        CloseHandle(device_write_overlapped.hEvent);
 
-       ULONG status = 0;
-       DeviceIoControl(device_handle, TAP_IOCTL_SET_MEDIA_STATUS, &status, sizeof status, &status, sizeof status, &len, NULL);
-}
-
-static void close_device(void) {
        CloseHandle(device_handle); device_handle = INVALID_HANDLE_VALUE;
 
        free(device); device = NULL;