From: Guus Sliepen <guus@tinc-vpn.org>
Date: Sun, 12 Apr 2015 13:36:50 +0000 (+0200)
Subject: Merge remote-tracking branch 'dechamps/windevice' into 1.1
X-Git-Tag: release-1.1pre12~186
X-Git-Url: https://www.tinc-vpn.org/git/browse?a=commitdiff_plain;h=f500a3d4e6e51ea1d88235e89e494ecb8f71ba5b;hp=417981462a2dde7800768eb58cf8f4e5238d4ad7;p=tinc

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

diff --git a/src/mingw/device.c b/src/mingw/device.c
index 19719a7a..4b821df7 100644
--- 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;
@@ -200,8 +202,12 @@ 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();
 }
 
@@ -210,10 +216,22 @@ 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);
 }
 
@@ -231,12 +249,29 @@ 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;
 	}