From: Todd C. Miller <Todd.Miller@sudo.ws>
Date: Wed, 31 Jan 2018 21:55:20 +0000 (-0700)
Subject: In device_issue_read() there is no need to reset Offset and OffsetHigh
X-Git-Tag: release-1.1pre16~28
X-Git-Url: https://www.tinc-vpn.org/git/browse?p=tinc;a=commitdiff_plain;h=8145a3392bdcff4d7856ba72e66a90d73d887c00

In device_issue_read() there is no need to reset Offset and OffsetHigh
to 0; they are only used for seekable files (not sockets).

Reset the write event before the call to WriteFile().  This is
consistent with how the read event is reset before ReadFile().

Clear device_write_packet.len() if WriteFile() fails with an error
other than ERROR_IO_PENDING; otherwise write_packet() will call
GetOverlappedResult() the next time it is run even though there is
no write in progress.
---

diff --git a/src/mingw/device.c b/src/mingw/device.c
index d90c69b0..eb3663d7 100644
--- a/src/mingw/device.c
+++ b/src/mingw/device.c
@@ -48,9 +48,6 @@ static const char *device_info = "Windows tap device";
 extern char *myport;
 
 static void device_issue_read() {
-	device_read_overlapped.Offset = 0;
-	device_read_overlapped.OffsetHigh = 0;
-
 	int status;
 
 	for(;;) {
@@ -311,9 +308,13 @@ static bool write_packet(vpn_packet_t *packet) {
 		   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;
+			if(GetLastError() != ERROR_IO_INCOMPLETE) {
+				logger(DEBUG_ALWAYS, LOG_ERR, "Error completing previously queued write to %s %s: %s", device_info, device, winerror(GetLastError()));
+			} else {
+				logger(DEBUG_TRAFFIC, LOG_ERR, "Previous overlapped write to %s %s still in progress", device_info, device);
+				// drop this packet
+				return true;
+			}
 		}
 	}
 
@@ -321,10 +322,14 @@ static bool write_packet(vpn_packet_t *packet) {
 
 	memcpy(&device_write_packet, packet, sizeof(*packet));
 
+	ResetEvent(device_write_overlapped.hEvent);
+
 	if(WriteFile(device_handle, DATA(&device_write_packet), device_write_packet.len, &outlen, &device_write_overlapped)) {
+		// Write was completed immediately.
 		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()));
+		device_write_packet.len = 0;
 		return false;
 	}