util-linux/microcom.c

   1 /*
   2  * bare bones 'talk to modem' program - similar to 'cu -l $device'
   3  * inspired by mgetty's microcom
   4  *
   5  * Copyright (C) 2007 by Vladimir Dronnikov <dronnikov@gmail.ru>
   6  *
   7  * Licensed under GPLv2, see file LICENSE in this tarball for details.
   8  */
   9 #include "busybox.h"
  10
  11 int microcom_main(int argc, char **argv);
  12 int microcom_main(int argc, char **argv)
  13 {
  14         struct pollfd pfd[2];
  15 #define sfd (pfd[1].fd)
  16         char *device_lock_file = NULL;
  17         const char *s;
  18         const char *opt_s = "9600";
  19         unsigned speed;
  20         int len;
  21         int exitcode = 1;
  22         struct termios tio0, tiosfd, tio;
  23
  24         getopt32(argv, "s:", &opt_s);
  25         argc -= optind;
  26         argv += optind;
  27         if (!argv[0])
  28                 bb_show_usage();
  29         speed = xatou(opt_s);
  30
  31         // try to create lock file in /var/lock
  32         s = bb_basename(argv[0]);
  33         if (!s[0]) {
  34                 errno = ENODEV;
  35                 bb_perror_msg_and_die("can't lock device");
  36         }
  37         device_lock_file = xasprintf("/var/lock/LCK..%s", s);
  38         sfd = open(device_lock_file, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0644);
  39         if (sfd < 0) {
  40                 if (ENABLE_FEATURE_CLEAN_UP)
  41                         free(device_lock_file);
  42                 device_lock_file = NULL;
  43                 if (errno == EEXIST)
  44                         bb_perror_msg_and_die("can't lock device");
  45                 // We don't abort on other errors: /var/lock can be
  46                 // non-writable or non-existent
  47         } else {
  48                 // %4d to make mgetty happy. It treats 4-bytes lock files as binary,
  49                 // not text, PID. Making 5+ char file. Brrr...
  50                 s = xasprintf("%4d\n", getpid());
  51                 write(sfd, s, strlen(s));
  52                 if (ENABLE_FEATURE_CLEAN_UP)
  53                         free((char*)s);
  54                 close(sfd);
  55         }
  56
  57         // open device
  58         sfd = open(argv[0], O_RDWR | O_NDELAY);
  59         if (sfd < 0) {
  60                 bb_perror_msg("can't open device");
  61                 goto unlock_and_exit;
  62         }
  63         fcntl(sfd, F_SETFL, O_RDWR); // why?
  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                 while (-1 == poll(pfd, 2, -1) && EINTR == errno)
 108                         continue;
 109                 for (i = 0; i < 2; ++i) {
 110                         if (pfd[i].revents & POLLIN) {
 111                                 len = read(pfd[i].fd, bb_common_bufsiz1, COMMON_BUFSIZE);
 112                                 if (len > 0) {
 113                                         if (!i && 24 == bb_common_bufsiz1[0])
 114                                                 goto done; // ^X exits
 115                                         write(pfd[1-i].fd, bb_common_bufsiz1, len);
 116                                 }
 117                         }
 118                 }
 119         }
 120  done:
 121         tcsetattr(sfd, TCSANOW, &tiosfd);
 122         tcsetattr(STDIN_FILENO, TCSANOW, &tio0);
 123         tcflush(STDIN_FILENO, TCIFLUSH);
 124
 125         if (ENABLE_FEATURE_CLEAN_UP)
 126                 close(sfd);
 127         exitcode = 0;
 128
 129  unlock_and_exit:
 130         // delete lock file
 131         if (device_lock_file) {
 132                 unlink(device_lock_file);
 133                 if (ENABLE_FEATURE_CLEAN_UP)
 134                         free(device_lock_file);
 135         }
 136         return exitcode;
 137 }