ttynvt: Optionally add delay during close

Optionally "Give network and remote end some time to close the
connection".

More or less like suggested by Jo Luxer:
https://gitlab.com/lars-thrane-as/ttynvt/-/merge_requests/4

src/ttynvt.c

@@ -46,9 +46,11 @@ static struct ttynvt_param {
     unsigned int    quiet;
     unsigned int    debug;
     int             logstd;
+    const char     *close_delay;
     /* Derived */
     char            host[64];
     unsigned int    port;
+    unsigned int    close_delay_us;
     /* Picked up */
     int             foreground;
 } ttynvt_param;
@@ -115,6 +117,20 @@ static void ttynvt_interrupted(fuse_req_t req, void *data)
     pthread_kill(thread, SIGUSR2);
 }
 
+
+static void _ttynvt_sleep_us(unsigned int tus)
+{
+    struct timespec ts;
+
+    ts.tv_sec = tus / 1000000;
+    tus -= ts.tv_sec * 1000000;
+    ts.tv_nsec = tus * 1000;
+
+    while (nanosleep(&ts, &ts))
+        ;
+}
+
+
 static int _check_dev(void)
 {
     int             rc;
@@ -1128,6 +1144,9 @@ static void ttynvt_release(fuse_req_t req, struct fuse_file_info *info)
     pthread_mutex_destroy(&tty->tty_lock);
     pthread_mutex_destroy(&tty->poll_lock);
 
+    if (ttynvt_param.close_delay_us)
+        _ttynvt_sleep_us(ttynvt_param.close_delay_us);
+
     _fd_close(tty->fds[FD_NET].fd);
     _fd_close(tty->fds[FD_MASTER].fd);
     _fd_close(tty->fds[FD_SLAVE].fd);
@@ -1167,6 +1186,7 @@ static const struct fuse_opt ttynvt_opts[] = {
     TTYNET_OPT("-n %s", dev_name, 0),
     TTYNET_OPT("--name=%s", dev_name, 0),
     TTYNET_OPT("-q", quiet, 1),
+    TTYNET_OPT("-s %s", close_delay, 0),
     TTYNET_OPT("-S %s", server, 0),
     TTYNET_OPT("--server=%s", server, 0),
     FUSE_OPT_KEY("-h", 0),
@@ -1186,6 +1206,7 @@ static void print_help(void)
             "\t-n name, --name=name (default: ttyNVT0)\n"
             "\t\tDevice will be created in /dev/$name.\n"
             "\t-q\t\tBe quiet (suppress informational messages)\n"
+            "\t-s delay \t\tDelay at close in ms (use u suffix for us)\n"
             "\t-S server, --server=host:port\n");
 }
 
@@ -1250,6 +1271,16 @@ int main(int argc, char *argv[])
 
     snprintf(dev_name, sizeof(dev_name), "DEVNAME=%s", ttynvt_param.dev_name);
 
+    if (ttynvt_param.close_delay)
+    {
+        char            ch = 'm';
+
+        sscanf(ttynvt_param.close_delay, "%u%c",
+               &ttynvt_param.close_delay_us, &ch);
+        if (ch != 'u')
+            ttynvt_param.close_delay_us *= 1000;        // To milliseconds
+    }
+
     struct cuse_info ci = {
         .dev_major = ttynvt_param.major,
         .dev_minor = ttynvt_param.minor,