From 72bd8dbb86edf54117c5c062cbb93f2bc1f8b729 Mon Sep 17 00:00:00 2001
From: Guus Sliepen <guus@tinc-vpn.org>
Date: Mon, 18 Jan 2016 13:58:46 +0100
Subject: [PATCH] Fix compatibility with TAP-Win32 9.0.0.21 and later.
Tinc was a bit sloppy writing packets to the TAP-Win32 device using
overlapped I/O. It worked with older versions of the driver, but it
caused lots of dropped packets with newer versions of the driver (that
use the NDIS 6 API).
---
src/mingw/device.c | 62 +++++++++++++++++++++++++++++++++++++---------
1 file changed, 50 insertions(+), 12 deletions(-)
diff --git a/src/mingw/device.c b/src/mingw/device.c
index 235e0fd6..49b833ab 100644
--- a/src/mingw/device.c
+++ b/src/mingw/device.c
@@ -43,11 +43,12 @@ static uint64_t device_total_in = 0;
static uint64_t device_total_out = 0;
extern char *myport;
+OVERLAPPED r_overlapped;
+OVERLAPPED w_overlapped;
static DWORD WINAPI tapreader(void *bla) {
int status;
DWORD len;
- OVERLAPPED overlapped;
vpn_packet_t packet;
int errors = 0;
@@ -55,19 +56,17 @@ static DWORD WINAPI tapreader(void *bla) {
/* Read from tap device and send to parent */
- overlapped.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
+ r_overlapped.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
for(;;) {
- overlapped.Offset = 0;
- overlapped.OffsetHigh = 0;
- ResetEvent(overlapped.hEvent);
+ ResetEvent(r_overlapped.hEvent);
- status = ReadFile(device_handle, packet.data, MTU, &len, &overlapped);
+ status = ReadFile(device_handle, packet.data, MTU, &len, &r_overlapped);
if(!status) {
if(GetLastError() == ERROR_IO_PENDING) {
- WaitForSingleObject(overlapped.hEvent, INFINITE);
- if(!GetOverlappedResult(device_handle, &overlapped, &len, FALSE))
+ WaitForSingleObject(r_overlapped.hEvent, INFINITE);
+ if(!GetOverlappedResult(device_handle, &r_overlapped, &len, FALSE))
continue;
} else {
logger(LOG_ERR, "Error while reading from %s %s: %s", device_info,
@@ -201,6 +200,11 @@ static bool setup_device(void) {
overwrite_mac = 1;
}
+ /* Create overlapped events for tap I/O */
+
+ r_overlapped.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
+ w_overlapped.hEvent = CreateEvent(NULL, TRUE, TRUE, NULL);
+
/* Start the tap reader */
thread = CreateThread(NULL, 0, tapreader, NULL, 0, NULL);
@@ -235,14 +239,48 @@ static bool read_packet(vpn_packet_t *packet) {
static bool write_packet(vpn_packet_t *packet) {
DWORD lenout;
- OVERLAPPED overlapped = {0};
+ static vpn_packet_t queue;
ifdebug(TRAFFIC) logger(LOG_DEBUG, "Writing packet of %d bytes to %s",
packet->len, device_info);
- if(!WriteFile(device_handle, packet->data, packet->len, &lenout, &overlapped)) {
- logger(LOG_ERR, "Error while writing to %s %s: %s", device_info, device, winerror(GetLastError()));
- return false;
+ /* Check if there is something in progress */
+
+ if(queue.len) {
+ DWORD size;
+ BOOL success = GetOverlappedResult(device_handle, &w_overlapped, &size, FALSE);
+ if(success) {
+ ResetEvent(&w_overlapped);
+ queue.len = 0;
+ } else {
+ int err = GetLastError();
+ if(err != ERROR_IO_INCOMPLETE) {
+ ifdebug(TRAFFIC) logger(LOG_DEBUG, "Error completing previously queued write: %s", winerror(err));
+ ResetEvent(&w_overlapped);
+ queue.len = 0;
+ } else {
+ ifdebug(TRAFFIC) logger(LOG_DEBUG, "Previous overlapped write still in progress");
+ // drop this packet
+ return true;
+ }
+ }
+ }
+
+ /* Otherwise, try to write. */
+
+ memcpy(queue.data, packet->data, packet->len);
+
+ if(!WriteFile(device_handle, queue.data, packet->len, &lenout, &w_overlapped)) {
+ int err = GetLastError();
+ if(err != ERROR_IO_PENDING) {
+ logger(LOG_ERR, "Error while writing to %s %s: %s", device_info, device, winerror(err));
+ return false;
+ }
+ // Write is being done asynchronously.
+ queue.len = packet->len;
+ } else {
+ // Write was completed immediately.
+ ResetEvent(&w_overlapped);
}
device_total_out += packet->len;
--
2.39.5