util-linux/microcom.c

   1 /* microcom.c
   2  *
   3  * bare bones 'talk to modem' program - similar to 'cu -l $device'
   4  * inspired by mgetty's microcom
   5  *
   6  */
   7 #include "busybox.h"
   8
   9 int microcom_main(int argc, char **argv);
  10 int microcom_main(int argc, char **argv)
  11 {
  12         struct pollfd pfd[2];
  13 #define sfd (pfd[1].fd)
  14         char *device_lock_file = NULL;
  15         const char *s;
  16         const char *opt_s = "9600";
  17         unsigned speed;
  18         int len;
  19         int exitcode = 1;
  20         struct termios tio0, tiosfd, tio;
  21
  22         getopt32(argv, "s:", &opt_s);
  23         argc -= optind;
  24         argv += optind;
  25         if (!argv[0])
  26                 bb_show_usage();
  27         speed = xatou(opt_s);
  28
  29         // try to create lock file in /var/lock
  30         s = bb_basename(argv[0]);
  31         if (!s[0]) {
  32                 errno = ENODEV;
  33                 bb_perror_msg_and_die("can't lock device");
  34         }
  35         device_lock_file = xasprintf("/var/lock/LCK..%s", s);
  36         sfd = open(device_lock_file, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0644);
  37         if (sfd < 0) {
  38                 if (ENABLE_FEATURE_CLEAN_UP)
  39                         free(device_lock_file);
  40                 device_lock_file = NULL;
  41                 if (errno == EEXIST)
  42                         bb_perror_msg_and_die("can't lock device");
  43                 // We don't abort on other errors: /var/lock can be
  44                 // non-writable or non-existent
  45         } else {
  46                 // %4d to make mgetty happy. It treats 4-bytes lock files as binary,
  47                 // not text, PID. Making 5+ char file. Brrr...
  48                 s = xasprintf("%4d\n", getpid());
  49                 write(sfd, s, strlen(s));
  50                 if (ENABLE_FEATURE_CLEAN_UP)
  51                         free((char*)s);
  52                 close(sfd);
  53         }
  54
  55         // open device
  56         sfd = open(argv[0], O_RDWR | O_NDELAY);
  57         if (sfd < 0) {
  58                 bb_perror_msg("can't open device");
  59                 goto unlock_and_exit;
  60         }
  61         fcntl(sfd, F_SETFL, O_RDWR); // why?
  62
  63         // put stdin to "raw mode", handle one character at a time
  64         tcgetattr(STDIN_FILENO, &tio0);
  65         tio = tio0;
  66         tio.c_lflag &= ~(ICANON|ECHO);
  67         tio.c_iflag &= ~(IXON|ICRNL);
  68         tio.c_oflag &= ~(ONLCR);
  69         tio.c_cc[VMIN] = 1;
  70         tio.c_cc[VTIME] = 0;
  71         if (tcsetattr(STDIN_FILENO, TCSANOW, &tio)) {
  72                 bb_perror_msg("can't tcsetattr for %s", "stdin");
  73                 goto unlock_and_exit;
  74         }
  75
  76         /* same thing for modem (plus: set baud rate) - TODO: make CLI option */
  77         tcgetattr(sfd, &tiosfd);
  78         tio = tiosfd;
  79         tio.c_lflag &= ~(ICANON|ECHO);
  80         tio.c_iflag &= ~(IXON|ICRNL);
  81         tio.c_oflag &= ~(ONLCR);
  82         tio.c_cc[VMIN] = 1;
  83         tio.c_cc[VTIME] = 0;
  84         cfsetispeed(&tio, tty_value_to_baud(speed));
  85         cfsetospeed(&tio, tty_value_to_baud(speed));
  86         if (tcsetattr(sfd, TCSANOW, &tio)) {
  87                 bb_perror_msg("can't tcsetattr for %s", "device");
  88                 goto unlock_and_exit;
  89         }
  90
  91         // disable SIGINT
  92         signal(SIGINT, SIG_IGN);
  93
  94         // drain stdin
  95         tcflush(STDIN_FILENO, TCIFLUSH);
  96         printf("connected to '%s' (%d bps), exit with ctrl-X...\r\n", argv[0], speed);
  97
  98         // main loop: check with poll(), then read/write bytes across
  99         pfd[0].fd = STDIN_FILENO;
 100         pfd[0].events = POLLIN;
 101         /*pfd[1].fd = sfd;*/
 102         pfd[1].events = POLLIN;
 103         while (1) {
 104                 int i;
 105                 while (-1 == poll(pfd, 2, -1) && EINTR == errno)
 106                         continue;
 107                 for (i = 0; i < 2; ++i) {
 108                         if (pfd[i].revents & POLLIN) {
 109                                 len = read(pfd[i].fd, bb_common_bufsiz1, COMMON_BUFSIZE);
 110                                 if (len > 0) {
 111                                         if (!i && 24 == bb_common_bufsiz1[0])
 112                                                 goto done; // ^X exits
 113                                         write(pfd[1-i].fd, bb_common_bufsiz1, len);
 114                                 }
 115                         }
 116                 }
 117         }
 118  done:
 119         tcsetattr(sfd, TCSANOW, &tiosfd);
 120         tcsetattr(STDIN_FILENO, TCSANOW, &tio0);
 121         tcflush(STDIN_FILENO, TCIFLUSH);
 122
 123         if (ENABLE_FEATURE_CLEAN_UP)
 124                 close(sfd);
 125         exitcode = 0;
 126
 127  unlock_and_exit:
 128         // delete lock file
 129         if (device_lock_file) {
 130                 unlink(device_lock_file);
 131                 if (ENABLE_FEATURE_CLEAN_UP)
 132                         free(device_lock_file);
 133         }
 134         return exitcode;
 135 }