source: MondoRescue/branches/stable/mindi-busybox/networking/slattach.c

/* vi: set sw=4 ts=4: */
/*
 * Stripped down version of net-tools for busybox.
 *
 * Author: Ignacio Garcia Perez (iggarpe at gmail dot com)
 *
 * License: GPLv2 or later, see LICENSE file in this tarball.
 *
 * There are some differences from the standard net-tools slattach:
 *
 * - The -l option is not supported.
 *
 * - The -F options allows disabling of RTS/CTS flow control.
 */

#include "libbb.h"
#include "libiproute/utils.h" /* invarg() */

struct globals {
    int handle;
    int saved_disc;
    struct termios saved_state;
};
#define G (*(struct globals*)&bb_common_bufsiz1)
#define handle       (G.handle      )
#define saved_disc   (G.saved_disc  )
#define saved_state  (G.saved_state )
#define INIT_G() do {} while (0)


/*
 * Save tty state and line discipline
 *
 * It is fine here to bail out on errors, since we haven modified anything yet
 */
static void save_state(void)
{
    /* Save line status */
    if (tcgetattr(handle, &saved_state) < 0)
        bb_perror_msg_and_die("get state");

    /* Save line discipline */
    xioctl(handle, TIOCGETD, &saved_disc);
}

static int set_termios_state_and_warn(struct termios *state)
{
    int ret;

    ret = tcsetattr(handle, TCSANOW, state);
    if (ret < 0) {
        bb_perror_msg("set state");
        return 1; /* used as exitcode */
    }
    return 0;
}

/*
 * Restore state and line discipline for ALL managed ttys
 *
 * Restoring ALL managed ttys is the only way to have a single
 * hangup delay.
 *
 * Go on after errors: we want to restore as many controlled ttys
 * as possible.
 */
static void restore_state_and_exit(int exitcode) ATTRIBUTE_NORETURN;
static void restore_state_and_exit(int exitcode)
{
    struct termios state;

    /* Restore line discipline */
    if (ioctl_or_warn(handle, TIOCSETD, &saved_disc) < 0) {
        exitcode = 1;
    }

    /* Hangup */
    memcpy(&state, &saved_state, sizeof(state));
    cfsetispeed(&state, B0);
    cfsetospeed(&state, B0);
    if (set_termios_state_and_warn(&state))
        exitcode = 1;
    sleep(1);

    /* Restore line status */
    if (set_termios_state_and_warn(&saved_state))
        exit(EXIT_FAILURE);
    if (ENABLE_FEATURE_CLEAN_UP)
        close(handle);

    exit(exitcode);
}

/*
 * Set tty state, line discipline and encapsulation
 */
static void set_state(struct termios *state, int encap)
{
    int disc;

    /* Set line status */
    if (set_termios_state_and_warn(state))
        goto bad;
    /* Set line discliple (N_SLIP always) */
    disc = N_SLIP;
    if (ioctl_or_warn(handle, TIOCSETD, &disc) < 0) {
        goto bad;
    }

    /* Set encapsulation (SLIP, CSLIP, etc) */
    if (ioctl_or_warn(handle, SIOCSIFENCAP, &encap) < 0) {
 bad:
        restore_state_and_exit(1);
    }
}

static void sig_handler(int signo)
{
    restore_state_and_exit(0);
}

int slattach_main(int argc, char **argv);
int slattach_main(int argc, char **argv)
{
    /* Line discipline code table */
    static const char proto_names[] ALIGN1 =
        "slip\0"        /* 0 */
        "cslip\0"       /* 1 */
        "slip6\0"       /* 2 */
        "cslip6\0"      /* 3 */
        "adaptive\0"    /* 8 */
        ;

    int i, encap, opt;
    struct termios state;
    const char *proto = "cslip";
    const char *extcmd;             /* Command to execute after hangup */
    const char *baud_str;
    int baud_code = -1;             /* Line baud rate (system code) */

    enum {
        OPT_p_proto  = 1 << 0,
        OPT_s_baud   = 1 << 1,
        OPT_c_extcmd = 1 << 2,
        OPT_e_quit   = 1 << 3,
        OPT_h_watch  = 1 << 4,
        OPT_m_nonraw = 1 << 5,
        OPT_L_local  = 1 << 6,
        OPT_F_noflow = 1 << 7
    };

    INIT_G();

    /* Parse command line options */
    opt = getopt32(argv, "p:s:c:ehmLF", &proto, &baud_str, &extcmd);
    /*argc -= optind;*/
    argv += optind;

    if (!*argv)
        bb_show_usage();

    encap = index_in_strings(proto_names, proto);

    if (encap < 0)
        invarg(proto, "protocol");
    if (encap > 3)
        encap = 8;

    /* We want to know if the baud rate is valid before we start touching the ttys */
    if (opt & OPT_s_baud) {
        baud_code = tty_value_to_baud(xatoi(baud_str));
        if (baud_code < 0)
            invarg(baud_str, "baud rate");
    }

    /* Trap signals in order to restore tty states upon exit */
    if (!(opt & OPT_e_quit)) {
        signal(SIGHUP, sig_handler);
        signal(SIGINT, sig_handler);
        signal(SIGQUIT, sig_handler);
        signal(SIGTERM, sig_handler);
    }

    /* Open tty */
    handle = open(*argv, O_RDWR | O_NDELAY);
    if (handle < 0) {
        char *buf = concat_path_file("/dev", *argv);
        handle = xopen(buf, O_RDWR | O_NDELAY);
        /* maybe if (ENABLE_FEATURE_CLEAN_UP) ?? */
        free(buf);
    }

    /* Save current tty state */
    save_state();

    /* Configure tty */
    memcpy(&state, &saved_state, sizeof(state));
    if (!(opt & OPT_m_nonraw)) { /* raw not suppressed */
        memset(&state.c_cc, 0, sizeof(state.c_cc));
        state.c_cc[VMIN] = 1;
        state.c_iflag = IGNBRK | IGNPAR;
        state.c_oflag = 0;
        state.c_lflag = 0;
        state.c_cflag = CS8 | HUPCL | CREAD
                      | ((opt & OPT_L_local) ? CLOCAL : 0)
                      | ((opt & OPT_F_noflow) ? 0 : CRTSCTS);
    }

    if (opt & OPT_s_baud) {
        cfsetispeed(&state, baud_code);
        cfsetospeed(&state, baud_code);
    }

    set_state(&state, encap);

    /* Exit now if option -e was passed */
    if (opt & OPT_e_quit)
        return 0;

    /* If we're not requested to watch, just keep descriptor open
     * until we are killed */
    if (!(opt & OPT_h_watch))
        while (1)
            sleep(24*60*60);

    /* Watch line for hangup */
    while (1) {
        if (ioctl(handle, TIOCMGET, &i) < 0 || !(i & TIOCM_CAR))
            goto no_carrier;
        sleep(15);
    }

 no_carrier:

    /* Execute command on hangup */
    if (opt & OPT_c_extcmd)
        system(extcmd);

    /* Restore states and exit */
    restore_state_and_exit(0);
}