miscutils/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) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
   7  *
   8  * Licensed under GPLv2, see file LICENSE in this tarball for details.
   9  */
  10 #include "libbb.h"
  11
  12 /* All known arches use small ints for signals */
  13 static volatile smallint signalled;
  14
  15 static void signal_handler(int signo)
  16 {
  17         signalled = signo;
  18 }
  19
  20 // set raw tty mode
  21 static void xget1(int fd, struct termios *t, struct termios *oldt)
  22 {
  23         tcgetattr(fd, oldt);
  24         *t = *oldt;
  25         cfmakeraw(t);
  26 //      t->c_lflag &= ~(ISIG|ICANON|ECHO|IEXTEN);
  27 //      t->c_iflag &= ~(BRKINT|IXON|ICRNL);
  28 //      t->c_oflag &= ~(ONLCR);
  29 //      t->c_cc[VMIN]  = 1;
  30 //      t->c_cc[VTIME] = 0;
  31 }
  32
  33 static int xset1(int fd, struct termios *tio, const char *device)
  34 {
  35         int ret = tcsetattr(fd, TCSAFLUSH, tio);
  36
  37         if (ret) {
  38                 bb_perror_msg("can't tcsetattr for %s", device);
  39         }
  40         return ret;
  41 }
  42
  43 int microcom_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  44 int microcom_main(int argc, char **argv)
  45 {
  46         int sfd;
  47         int nfd;
  48         struct pollfd pfd[2];
  49         struct termios tio0, tiosfd, tio;
  50         char *device_lock_file;
  51         enum {
  52                 OPT_X = 1 << 0, // do not respect Ctrl-X, Ctrl-@
  53                 OPT_s = 1 << 1, // baudrate
  54                 OPT_d = 1 << 2, // wait for device response, msecs
  55                 OPT_t = 1 << 3, // timeout, ms
  56         };
  57         speed_t speed = 9600;
  58         int delay = -1;
  59         int timeout = -1;
  60
  61         // fetch options
  62         unsigned opts;
  63         opt_complementary = "=1:s+:d+:t+"; // exactly one arg should be there
  64         opts = getopt32(argv, "Xs:d:t:", &speed, &delay, &timeout);
  65
  66 //      argc -= optind;
  67         argv += optind;
  68
  69         // try to create lock file in /var/lock
  70         device_lock_file = (char *)bb_basename(argv[0]);
  71         device_lock_file = xasprintf("/var/lock/LCK..%s", device_lock_file);
  72         sfd = open(device_lock_file, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0644);
  73         if (sfd < 0) {
  74                 if (errno == EEXIST)
  75                         bb_perror_msg_and_die("can't create %s", device_lock_file);
  76                 if (ENABLE_FEATURE_CLEAN_UP)
  77                         free(device_lock_file);
  78                 device_lock_file = NULL;
  79         }
  80         if (sfd > 0) {
  81                 // %4d to make mgetty happy. It treats 4-bytes lock files as binary,
  82                 // not text, PID. Making 5+ char file. Brrr...
  83                 char *s = xasprintf("%4d\n", getpid());
  84                 write(sfd, s, strlen(s));
  85                 if (ENABLE_FEATURE_CLEAN_UP)
  86                         free(s);
  87                 close(sfd);
  88         }
  89
  90         // setup signals
  91         bb_signals(0
  92                 + (1 << SIGHUP)
  93                 + (1 << SIGINT)
  94                 + (1 << SIGTERM)
  95                 + (1 << SIGPIPE)
  96                 , signal_handler);
  97
  98         // error exit code if we fail to open the device
  99         signalled = 1;
 100
 101         // put stdin to "raw mode" (if stdin is a TTY),
 102         // handle one character at a time
 103         if (isatty(STDIN_FILENO)) {
 104                 xget1(STDIN_FILENO, &tio, &tio0);
 105                 if (xset1(STDIN_FILENO, &tio, "stdin"))
 106                         goto done;
 107         }
 108
 109         // open device
 110         sfd = open_or_warn(argv[0], O_RDWR | O_NOCTTY | O_NONBLOCK);
 111         if (sfd < 0)
 112                 goto done;
 113         fcntl(sfd, F_SETFL, 0);
 114
 115         // put device to "raw mode"
 116         xget1(sfd, &tio, &tiosfd);
 117 //      tio.c_cflag |= (CREAD|HUPCL); // we just bail out on any device error
 118         // set device speed
 119         cfsetspeed(&tio, tty_value_to_baud(speed));
 120         if (xset1(sfd, &tio, argv[0]))
 121                 goto restore0_and_done;
 122
 123         // main loop: check with poll(), then read/write bytes across
 124         pfd[0].fd = sfd;
 125         pfd[0].events = POLLIN;
 126         pfd[1].fd = STDIN_FILENO;
 127         pfd[1].events = POLLIN;
 128
 129         signalled = 0;
 130         nfd = 2;
 131         while (!signalled && safe_poll(pfd, nfd, timeout) > 0) {
 132                 if (nfd > 1 && pfd[1].revents) {
 133                         char c;
 134                         // read from stdin -> write to device
 135                         if (safe_read(STDIN_FILENO, &c, 1) < 1) {
 136                                 // don't poll stdin anymore if we got EOF/error
 137                                 nfd--;
 138                                 goto skip_write;
 139                         }
 140                         // do we need special processing?
 141                         if (!(opts & OPT_X)) {
 142                                 // ^@ sends Break
 143                                 if (VINTR == c) {
 144                                         tcsendbreak(sfd, 0);
 145                                         goto skip_write;
 146                                 }
 147                                 // ^X exits
 148                                 if (24 == c)
 149                                         break;
 150                         }
 151                         write(sfd, &c, 1);
 152                         if (delay >= 0)
 153                                 safe_poll(pfd, 1, delay);
 154 skip_write: ;
 155                 }
 156                 if (pfd[0].revents) {
 157 #define iobuf bb_common_bufsiz1
 158                         ssize_t len;
 159                         // read from device -> write to stdout
 160                         len = safe_read(sfd, iobuf, sizeof(iobuf));
 161                         if (len > 0)
 162                                 full_write(STDOUT_FILENO, iobuf, len);
 163                         else {
 164                                 // EOF/error -> bail out
 165                                 signalled = SIGHUP;
 166                                 break;
 167                         }
 168                 }
 169         }
 170
 171         // restore device mode
 172         tcsetattr(sfd, TCSAFLUSH, &tiosfd);
 173
 174 restore0_and_done:
 175         if (isatty(STDIN_FILENO))
 176                 tcsetattr(STDIN_FILENO, TCSAFLUSH, &tio0);
 177
 178 done:
 179         if (device_lock_file)
 180                 unlink(device_lock_file);
 181
 182         return signalled;
 183 }