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) 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 /* 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 canonical 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, TCSANOW, 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         struct pollfd pfd[2];
  47         int nfd;
  48         //int sfd;
  49 #define sfd (pfd[0].fd)
  50         char *device_lock_file;
  51         const char *opt_s = "9600";
  52         speed_t speed;
  53         const char *opt_t = "100"; // 0.1 sec timeout
  54         unsigned timeout;
  55         struct termios tio0, tiosfd, tio;
  56         bool istty;
  57
  58         // fetch options
  59         opt_complementary = "-1"; /* at least one arg should be there */
  60         getopt32(argv, "s:t:", &opt_s, &opt_t);
  61         argc -= optind;
  62         argv += optind;
  63
  64         // check sanity
  65         speed = xatou(opt_s);
  66         timeout = xatou(opt_t);
  67         device_lock_file = (char *)bb_basename(argv[0]);
  68
  69         // try to create lock file in /var/lock
  70         device_lock_file = xasprintf("/var/lock/LCK..%s", device_lock_file);
  71         sfd = open(device_lock_file, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0644);
  72         if (sfd < 0) {
  73                 if (errno == EEXIST)
  74                         bb_perror_msg_and_die("can't lock device");
  75                 // We don't abort on other errors: /var/lock can be
  76                 // non-writable or non-existent
  77                 if (ENABLE_FEATURE_CLEAN_UP)
  78                         free(device_lock_file);
  79                 device_lock_file = NULL;
  80         } else {
  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         sig_catch(SIGHUP,  signal_handler);
  92         sig_catch(SIGINT,  signal_handler);
  93         sig_catch(SIGTERM, signal_handler);
  94         sig_catch(SIGPIPE, signal_handler);
  95
  96         // error exit code if we fail to open the device
  97         signalled = 1;
  98
  99         // open device
 100         sfd = open_or_warn(argv[0], O_RDWR | O_NOCTTY | O_NONBLOCK);
 101         if (sfd < 0)
 102                 goto unlock_and_exit;
 103         fcntl(sfd, F_SETFL, O_RDWR | O_NOCTTY);
 104
 105         /* put stdin to "raw mode" (if stdin is a TTY),
 106                 handle one character at a time */
 107         istty = isatty(STDIN_FILENO);
 108         if (istty) {
 109                 xget1(STDIN_FILENO, &tio, &tio0);
 110                 if (xset1(STDIN_FILENO, &tio, "stdin"))
 111                         goto close_unlock_and_exit;
 112 //              tcflush(STDIN_FILENO, TCIFLUSH);
 113                 timeout = -1; // tty input? -> set infinite timeout for poll()
 114         }
 115
 116         // same thing for modem
 117         xget1(sfd, &tio, &tiosfd);
 118         // order device to hang up at exit
 119         tio.c_cflag |= (CREAD|HUPCL);
 120         // set device speed
 121         cfsetspeed(&tio, tty_value_to_baud(speed));
 122         if (xset1(sfd, &tio, argv[0]))
 123                 goto restore0_close_unlock_and_exit;
 124
 125         // main loop: check with poll(), then read/write bytes across
 126         /* pfd[0].fd = sfd; - they are the same */
 127         pfd[0].events = POLLIN;
 128         pfd[1].fd = STDIN_FILENO;
 129         pfd[1].events = POLLIN;
 130
 131         // TODO: on piped input should we treat NL as CRNL?!
 132
 133         signalled = 0;
 134         // initially we have to poll() both stdin and device
 135         nfd = 2;
 136         while (!signalled && nfd && safe_poll(pfd, nfd, timeout) > 0) {
 137                 int i;
 138
 139                 for (i = 0; i < nfd; ++i) {
 140                         if (pfd[i].revents & (POLLIN | POLLHUP)) {
 141 //              int fd;
 142                                 char c;
 143                                 // read a byte
 144                                 if (safe_read(pfd[i].fd, &c, 1) < 1) {
 145                                         // this can occur at the end of piped input
 146                                         // from now we only poll() for device
 147                                         nfd--;
 148                                         continue;
 149                                 }
 150 //              fd = STDOUT_FILENO;
 151                                 // stdin requires additional processing
 152                                 // (TODO: must be controlled by command line switch)
 153                                 if (i) {
 154                                         // ^@ sends Break
 155                                         if (0 == c) {
 156                                                 tcsendbreak(sfd, 0);
 157                                                 continue;
 158                                         }
 159                                         // ^X exits
 160                                         if (24 == c)
 161                                                 goto done;
 162 //              fd = sfd;
 163                                 }
 164                                 // write the byte
 165                                 write(i ? sfd : STDOUT_FILENO, &c, 1);
 166 //              write(fd, &c, 1);
 167                                 // give device a chance to get data
 168                                 // wait 0.01 msec
 169                                 // (TODO: seems to be arbitrary to me)
 170                                 if (i)
 171                                         usleep(10);
 172                         }
 173                 }
 174         }
 175 done:
 176         tcsetattr(sfd, TCSANOW, &tiosfd);
 177
 178 restore0_close_unlock_and_exit:
 179         if (istty) {
 180 //              tcflush(STDIN_FILENO, TCIFLUSH);
 181                 tcsetattr(STDIN_FILENO, TCSANOW, &tio0);
 182         }
 183
 184 close_unlock_and_exit:
 185         if (ENABLE_FEATURE_CLEAN_UP)
 186                 close(sfd);
 187
 188 unlock_and_exit:
 189         // delete lock file
 190         if (device_lock_file) {
 191                 unlink(device_lock_file);
 192                 if (ENABLE_FEATURE_CLEAN_UP)
 193                         free(device_lock_file);
 194         }
 195         return signalled;
 196 }