microcom.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * bare bones 'talk to modem' program - similar to 'cu -l $device'
   4  * inspired by mgetty's microcom
   5  *
   6  * Copyright (C) 2007 by Vladimir Dronnikov <dronnikov@gmail.ru>
   7  *
   8  * Licensed under GPLv2, see file LICENSE in this tarball for details.
   9  */
  10 #include "libbb.h"
  11
  12 int microcom_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  13 int microcom_main(int argc, char **argv)
  14 {
  15         struct pollfd pfd[2];
  16 #define sfd (pfd[1].fd)
  17         char *device_lock_file = NULL;
  18         const char *s;
  19         const char *opt_s = "9600";
  20         unsigned speed;
  21         int len;
  22         int exitcode = 1;
  23         struct termios tio0, tiosfd, tio;
  24
  25         getopt32(argv, "s:", &opt_s);
  26         argc -= optind;
  27         argv += optind;
  28         if (!argv[0])
  29                 bb_show_usage();
  30         speed = xatou(opt_s);
  31
  32         // try to create lock file in /var/lock
  33         s = bb_basename(argv[0]);
  34         if (!s[0]) {
  35                 errno = ENODEV;
  36                 bb_perror_msg_and_die("can't lock device");
  37         }
  38         device_lock_file = xasprintf("/var/lock/LCK..%s", s);
  39         sfd = open(device_lock_file, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0644);
  40         if (sfd < 0) {
  41                 if (ENABLE_FEATURE_CLEAN_UP)
  42                         free(device_lock_file);
  43                 device_lock_file = NULL;
  44                 if (errno == EEXIST)
  45                         bb_perror_msg_and_die("can't lock device");
  46                 // We don't abort on other errors: /var/lock can be
  47                 // non-writable or non-existent
  48         } else {
  49                 // %4d to make mgetty happy. It treats 4-bytes lock files as binary,
  50                 // not text, PID. Making 5+ char file. Brrr...
  51                 s = xasprintf("%4d\n", getpid());
  52                 write(sfd, s, strlen(s));
  53                 if (ENABLE_FEATURE_CLEAN_UP)
  54                         free((char*)s);
  55                 close(sfd);
  56         }
  57
  58         // open device
  59         sfd = open(argv[0], O_RDWR);
  60         if (sfd < 0) {
  61                 bb_perror_msg("can't open device");
  62                 goto unlock_and_exit;
  63         }
  64
  65         // put stdin to "raw mode", handle one character at a time
  66         tcgetattr(STDIN_FILENO, &tio0);
  67         tio = tio0;
  68         tio.c_lflag &= ~(ICANON|ECHO);
  69         tio.c_iflag &= ~(IXON|ICRNL);
  70         tio.c_oflag &= ~(ONLCR);
  71         tio.c_cc[VMIN] = 1;
  72         tio.c_cc[VTIME] = 0;
  73         if (tcsetattr(STDIN_FILENO, TCSANOW, &tio)) {
  74                 bb_perror_msg("can't tcsetattr for %s", "stdin");
  75                 goto unlock_and_exit;
  76         }
  77
  78         /* same thing for modem (plus: set baud rate) - TODO: make CLI option */
  79         tcgetattr(sfd, &tiosfd);
  80         tio = tiosfd;
  81         tio.c_lflag &= ~(ICANON|ECHO);
  82         tio.c_iflag &= ~(IXON|ICRNL);
  83         tio.c_oflag &= ~(ONLCR);
  84         tio.c_cc[VMIN] = 1;
  85         tio.c_cc[VTIME] = 0;
  86         cfsetispeed(&tio, tty_value_to_baud(speed));
  87         cfsetospeed(&tio, tty_value_to_baud(speed));
  88         if (tcsetattr(sfd, TCSANOW, &tio)) {
  89                 bb_perror_msg("can't tcsetattr for %s", "device");
  90                 goto unlock_and_exit;
  91         }
  92
  93         // disable SIGINT
  94         signal(SIGINT, SIG_IGN);
  95
  96         // drain stdin
  97         tcflush(STDIN_FILENO, TCIFLUSH);
  98         printf("connected to '%s' (%d bps), exit with ctrl-X...\r\n", argv[0], speed);
  99
 100         // main loop: check with poll(), then read/write bytes across
 101         pfd[0].fd = STDIN_FILENO;
 102         pfd[0].events = POLLIN;
 103         /*pfd[1].fd = sfd;*/
 104         pfd[1].events = POLLIN;
 105         while (1) {
 106                 int i;
 107                 safe_poll(pfd, 2, -1);
 108                 for (i = 0; i < 2; ++i) {
 109                         if (pfd[i].revents & POLLIN) {
 110                                 len = read(pfd[i].fd, bb_common_bufsiz1, COMMON_BUFSIZE);
 111                                 if (len > 0) {
 112                                         if (!i && 24 == bb_common_bufsiz1[0])
 113                                                 goto done; // ^X exits
 114                                         write(pfd[1-i].fd, bb_common_bufsiz1, len);
 115                                 }
 116                         }
 117                 }
 118         }
 119  done:
 120         tcsetattr(sfd, TCSANOW, &tiosfd);
 121         tcsetattr(STDIN_FILENO, TCSANOW, &tio0);
 122         tcflush(STDIN_FILENO, TCIFLUSH);
 123
 124         if (ENABLE_FEATURE_CLEAN_UP)
 125                 close(sfd);
 126         exitcode = 0;
 127
 128  unlock_and_exit:
 129         // delete lock file
 130         if (device_lock_file) {
 131                 unlink(device_lock_file);
 132                 if (ENABLE_FEATURE_CLEAN_UP)
 133                         free(device_lock_file);
 134         }
 135         return exitcode;
 136 }