/* vi: set sw=4 ts=4: */
/*
 * Stripped down version of net-tools for busybox.
 *
 * Author: Ignacio Garcia Perez (iggarpe at gmail dot com)
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 *
 * 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.
 */
//config:config SLATTACH
//config:       bool "slattach (6.2 kb)"
//config:       default y
//config:       help
//config:       slattach configures serial line as SLIP network interface.

//applet:IF_SLATTACH(APPLET(slattach, BB_DIR_SBIN, BB_SUID_DROP))
/* shouldn't be NOEXEC: may sleep indefinitely */

//kbuild:lib-$(CONFIG_SLATTACH) += slattach.o

//usage:#define slattach_trivial_usage
//usage:       "[-ehmLF] [-c SCRIPT] [-s BAUD] [-p PROTOCOL] SERIAL_DEVICE"
//usage:#define slattach_full_usage "\n\n"
//usage:       "Configure serial line as SLIP network interface\n"
//usage:     "\n        -p PROT Protocol: slip, cslip (default), slip6, clisp6, adaptive"
//usage:     "\n        -s BAUD Line speed"
//usage:     "\n        -e      Exit after initialization"
//usage:     "\n        -h      Exit if carrier is lost (else never exits)"
//usage:     "\n        -c PROG Run PROG on carrier loss"
//usage:     "\n        -m      Do NOT set raw 8bit mode"
//usage:     "\n        -L      Enable 3-wire operation"
//usage:     "\n        -F      Disable RTS/CTS flow control"

#include "libbb.h"
#include "common_bufsiz.h"
#include "libiproute/utils.h" /* invarg_1_to_2() */

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

#define serial_fd 3

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

        ret = tcsetattr(serial_fd, TCSANOW, state);
        if (ret != 0) {
                bb_simple_perror_msg("tcsetattr");
                return 1; /* used as exitcode */
        }
        return ret; /* 0 */
}

static void restore_state_and_exit(int exitcode) NORETURN;
static void restore_state_and_exit(int exitcode)
{
        struct termios state;

        /* Restore line discipline */
        if (ioctl_or_warn(serial_fd, TIOCSETD, &G.saved_disc)) {
                exitcode = 1;
        }

        /* Hangup */
        memcpy(&state, &G.saved_state, sizeof(state));
        cfsetispeed(&state, B0);
        cfsetospeed(&state, B0);
        exitcode |= tcsetattr_serial_or_warn(&state);
        sleep1();

        /* Restore line status */
        if (tcsetattr_serial_or_warn(&G.saved_state))
                exit(EXIT_FAILURE);

        if (ENABLE_FEATURE_CLEAN_UP)
                close(serial_fd);

        exit(exitcode);
}

static void sig_handler(int signo UNUSED_PARAM)
{
        restore_state_and_exit(EXIT_SUCCESS);
}

int slattach_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int slattach_main(int argc UNUSED_PARAM, 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 */
                ;
        static const int int_N_SLIP = N_SLIP;

        int encap, opt, fd;
        struct termios state;
        const char *proto = "cslip";
        const char *extcmd;   /* Command to execute after hangup */
        const char *baud_str;
        int baud_code = baud_code; /* for compiler */

        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" "\0" "=1",
                                &proto, &baud_str, &extcmd
        );
        /*argc -= optind;*/
        argv += optind;

        encap = index_in_strings(proto_names, proto);
        if (encap < 0)
                invarg_1_to_2(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_1_to_2(baud_str, "baud rate");
        }

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

        /* Save current tty state */
        if (tcgetattr(serial_fd, &G.saved_state) != 0)
                bb_simple_perror_msg_and_die("tcgetattr");
        /* Save line discipline */
        xioctl(serial_fd, TIOCGETD, &G.saved_disc);

        /* Trap signals in order to restore tty states upon exit */
        if (!(opt & OPT_e_quit)) {
                bb_signals(0
                        + (1 << SIGHUP)
                        + (1 << SIGINT)
                        + (1 << SIGQUIT)
                        + (1 << SIGTERM)
                        , sig_handler);
        }

        /* Configure tty */
        memcpy(&state, &G.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);
                cfsetispeed(&state, cfgetispeed(&G.saved_state));
                cfsetospeed(&state, cfgetospeed(&G.saved_state));
        }
        if (opt & OPT_s_baud) {
                cfsetispeed(&state, baud_code);
                cfsetospeed(&state, baud_code);
        }
        /* Set line status */
        if (tcsetattr_serial_or_warn(&state))
                goto bad;
        /* Set line disclipline (N_SLIP always) */
        if (ioctl_or_warn(serial_fd, TIOCSETD, (void*)&int_N_SLIP))
                goto bad;
        /* Set encapsulation (SLIP, CSLIP, etc) */
        if (ioctl_or_warn(serial_fd, SIOCSIFENCAP, &encap))
                goto bad;

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

        /* 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) {
                int modem_stat;
                if (ioctl(serial_fd, TIOCMGET, &modem_stat))
                        break;
                if (!(modem_stat & TIOCM_CAR))
                        break;
                sleep(15);
        }

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

        /* Restore states and exit */
        restore_state_and_exit(EXIT_SUCCESS);
 bad:
        restore_state_and_exit(EXIT_FAILURE);
}