Add warnings for bad combinations of Device and Interface.

[tinc] / src / mingw / device.c

diff --git a/src/mingw/device.c b/src/mingw/device.c
index e95878c..7a462ba 100644 (file)
--- a/src/mingw/device.c
+++ b/src/mingw/device.c
@@ -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;
@@ -99,6 +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 && interface)
+               logger(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)) {
@@ -219,8 +224,12 @@ 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();
 }
 
@@ -229,10 +238,22 @@ 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);
 }
 
@@ -250,12 +271,29 @@ static bool read_packet(vpn_packet_t *packet) {
 
 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;
        }