microcom: add new applet, this time for real

1 files changed, 135 insertions, 0 deletions

diff --git a/util-linux/microcom.c b/util-linux/microcom.c
new file mode 100644
index 000000000..f6f8e07f6
--- /dev/null
+++ b/util-linux/microcom.c
@@ -0,0 +1,135 @@
+/* microcom.c
+ *
+ * bare bones 'talk to modem' program - similar to 'cu -l $device'
+ * inspired by mgetty's microcom
+ *
+ */
+#include "busybox.h"
+
+int microcom_main(int argc, char **argv);
+int microcom_main(int argc, char **argv)
+{
+        struct pollfd pfd[2];
+#define sfd (pfd[1].fd)
+        char *device_lock_file = NULL;
+        const char *s;
+        const char *opt_s = "9600";
+        unsigned speed;
+        int len;
+        int exitcode = 1;
+        struct termios tio0, tiosfd, tio;
+
+        getopt32(argv, "s:", &opt_s);
+        argc -= optind;
+        argv += optind;
+        if (!argv[0])
+                bb_show_usage();
+        speed = xatou(opt_s);
+
+        // try to create lock file in /var/lock
+        s = bb_basename(argv[0]);
+        if (!s[0]) {
+                errno = ENODEV;
+                bb_perror_msg_and_die("can't lock device");
+        }
+        device_lock_file = xasprintf("/var/lock/LCK..%s", s);
+        sfd = open(device_lock_file, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0644);
+        if (sfd < 0) {
+                if (ENABLE_FEATURE_CLEAN_UP)
+                        free(device_lock_file);
+                device_lock_file = NULL;
+                if (errno == EEXIST)
+                        bb_perror_msg_and_die("can't lock device");
+                // We don't abort on other errors: /var/lock can be
+                // non-writable or non-existent
+        } else {
+                // %4d to make mgetty happy. It treats 4-bytes lock files as binary,
+                // not text, PID. Making 5+ char file. Brrr...
+                s = xasprintf("%4d\n", getpid());
+                write(sfd, s, strlen(s));
+                if (ENABLE_FEATURE_CLEAN_UP)
+                        free((char*)s);
+                close(sfd);
+        }
+
+        // open device
+        sfd = open(argv[0], O_RDWR | O_NDELAY);
+        if (sfd < 0) {
+                bb_perror_msg("can't open device");
+                goto unlock_and_exit;
+        }
+        fcntl(sfd, F_SETFL, O_RDWR); // why?
+
+        // put stdin to "raw mode", handle one character at a time
+        tcgetattr(STDIN_FILENO, &tio0);
+        tio = tio0;
+        tio.c_lflag &= ~(ICANON|ECHO);
+        tio.c_iflag &= ~(IXON|ICRNL);
+        tio.c_oflag &= ~(ONLCR);
+        tio.c_cc[VMIN] = 1;
+        tio.c_cc[VTIME] = 0;
+        if (tcsetattr(STDIN_FILENO, TCSANOW, &tio)) {
+                bb_perror_msg("can't tcsetattr for %s", "stdin");
+                goto unlock_and_exit;
+        }
+
+        /* same thing for modem (plus: set baud rate) - TODO: make CLI option */
+        tcgetattr(sfd, &tiosfd);
+        tio = tiosfd;
+        tio.c_lflag &= ~(ICANON|ECHO);
+        tio.c_iflag &= ~(IXON|ICRNL);
+        tio.c_oflag &= ~(ONLCR);
+        tio.c_cc[VMIN] = 1;
+        tio.c_cc[VTIME] = 0;
+        cfsetispeed(&tio, tty_value_to_baud(speed));
+        cfsetospeed(&tio, tty_value_to_baud(speed));
+        if (tcsetattr(sfd, TCSANOW, &tio)) {
+                bb_perror_msg("can't tcsetattr for %s", "device");
+                goto unlock_and_exit;
+        }
+
+        // disable SIGINT
+        signal(SIGINT, SIG_IGN);
+
+        // drain stdin
+        tcflush(STDIN_FILENO, TCIFLUSH);
+        printf("connected to '%s' (%d bps), exit with ctrl-X...\r\n", argv[0], speed);
+
+        // main loop: check with poll(), then read/write bytes across
+        pfd[0].fd = STDIN_FILENO;
+        pfd[0].events = POLLIN;
+        /*pfd[1].fd = sfd;*/
+        pfd[1].events = POLLIN;
+        while (1) {
+                int i;
+                while (-1 == poll(pfd, 2, -1) && EINTR == errno)
+                        continue;
+                for (i = 0; i < 2; ++i) {
+                        if (pfd[i].revents & POLLIN) { 
+                                len = read(pfd[i].fd, bb_common_bufsiz1, COMMON_BUFSIZE);
+                                if (len > 0) {
+                                        if (!i && 24 == bb_common_bufsiz1[0])
+                                                goto done; // ^X exits
+                                        write(pfd[1-i].fd, bb_common_bufsiz1, len);
+                                }
+                        }
+                }
+        }
+ done:
+        tcsetattr(sfd, TCSANOW, &tiosfd);
+        tcsetattr(STDIN_FILENO, TCSANOW, &tio0);
+        tcflush(STDIN_FILENO, TCIFLUSH);
+
+        if (ENABLE_FEATURE_CLEAN_UP)
+                close(sfd);
+        exitcode = 0;
+
+ unlock_and_exit:
+        // delete lock file
+        if (device_lock_file) {
+                unlink(device_lock_file);
+                if (ENABLE_FEATURE_CLEAN_UP)
+                        free(device_lock_file);
+        }
+        return exitcode;
+}