Flush output buffers in the tap reader thread on Windows.

This is basically a port of commit 50fcfea1 to 1.1.

src/event.c

@@ -245,6 +245,12 @@ bool event_loop(void) {
 	return true;
 }
 
+void event_flush_output(void) {
+	for splay_each(io_t, io, &io_tree)
+		if(FD_ISSET(io->fd, &writefds))
+			io->cb(io->data, IO_WRITE);
+}
+
 void event_exit(void) {
 	running = false;
 }

src/event.h

@@ -65,6 +65,7 @@ extern void signal_add(signal_t *sig, signal_cb_t cb, void *data, int signum);
 extern void signal_del(signal_t *sig);
 
 extern bool event_loop(void);
+extern void event_flush_output(void);
 extern void event_exit(void);
 
 #endif

src/mingw/device.c

@@ -80,6 +80,7 @@ static DWORD WINAPI tapreader(void *bla) {
 		packet.len = len;
 		packet.priority = 0;
 		route(myself, &packet);
+		event_flush_output();
 		LeaveCriticalSection(&mutex);
 	}
 }

src/net_socket.c

@@ -349,6 +349,9 @@ static void do_outgoing_pipe(connection_t *c, char *command) {
 }
 
 static void handle_meta_write(connection_t *c) {
+	if(c->outbuf.len <= c->outbuf.offset)
+		return;
+
 	ssize_t outlen = send(c->socket, c->outbuf.data + c->outbuf.offset, c->outbuf.len - c->outbuf.offset, 0);
 	if(outlen <= 0) {
 		if(!errno || errno == EPIPE) {