/*
 * Copyright (c) 2001, Adam Dunkels.
 * Copyright (c) 2009, Joakim Eriksson, Niclas Finne.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior
 *    written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This file is part of the uIP TCP/IP stack.
 *
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <time.h>
#include <sys/types.h>

#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <termios.h>
#include <sys/ioctl.h>

#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <err.h>

in_addr_t giaddr;
in_addr_t netaddr;
in_addr_t circuit_addr;

int ssystem(const char *fmt, ...) __attribute__((__format__(__printf__, 1, 2)));
void write_to_serial(int outfd, void *inbuf, int len);

//#define PROGRESS(s) fprintf(stderr, s)
#define PROGRESS(s) do { } while (0)

#define USAGE_STRING "usage: tapslip6 [-B baudrate] [-s siodev] [-t tundev] ipaddress netmask"

char tundev[1024] = { "tap0" };

int
ssystem(const char *fmt, ...) __attribute__((__format__(__printf__, 1, 2)));

int
ssystem(const char *fmt, ...)
{
    char cmd[128];
    va_list ap;
    va_start(ap, fmt);
    vsnprintf(cmd, sizeof(cmd), fmt, ap);
    va_end(ap);
    printf("%s\n", cmd);
    fflush(stdout);
    return system(cmd);
}

#define SLIP_END     0300
#define SLIP_ESC     0333
#define SLIP_ESC_END 0334
#define SLIP_ESC_ESC 0335

static void
print_packet(u_int8_t *p, int len)
{
    int i;

    for (i = 0; i < len; i++) {
        printf("%02x", p[i]);

        if ((i & 3) == 3) {
            printf(" ");
        }

        if ((i & 15) == 15) {
            printf("\n");
        }
    }

    printf("\n");
}

int
is_sensible_string(const unsigned char *s, int len)
{
    int i;

    for (i = 1; i < len; i++) {
        if (s[i] == 0 || s[i] == '\r' || s[i] == '\n' || s[i] == '\t') {
            continue;
        }
        else if (s[i] < ' ' || '~' < s[i]) {
            return 0;
        }
    }

    return 1;
}



/*
 * Read from serial, when we have a packet write it to tun. No output
 * buffering, input buffered by stdio.
 */
void
serial_to_tun(FILE *inslip, int outfd)
{
    static union {
        unsigned char inbuf[2000];
    } uip;
    static int inbufptr = 0;

    int ret;
    unsigned char c;

#ifdef linux
    ret = fread(&c, 1, 1, inslip);

    if (ret == -1 || ret == 0) {
        err(1, "serial_to_tun: read");
    }

    goto after_fread;
#endif

read_more:

    if (inbufptr >= sizeof(uip.inbuf)) {
        inbufptr = 0;
    }

    ret = fread(&c, 1, 1, inslip);
#ifdef linux
after_fread:
#endif

    if (ret == -1) {
        err(1, "serial_to_tun: read");
    }

    if (ret == 0) {
        clearerr(inslip);
        return;
        fprintf(stderr, "serial_to_tun: EOF\n");
        exit(1);
    }

    /*  fprintf(stderr, ".");*/
    switch (c) {
        case SLIP_END:
            if (inbufptr > 0) {
                if (uip.inbuf[0] == '!') {
                    if (uip.inbuf[1] == 'M') {
                        /* Read gateway MAC address and autoconfigure tap0 interface */
                        char macs[24];
                        int i, pos;

                        for (i = 0, pos = 0; i < 16; i++) {
                            macs[pos++] = uip.inbuf[2 + i];

                            if ((i & 1) == 1 && i < 14) {
                                macs[pos++] = ':';
                            }
                        }

                        macs[pos] = '\0';
                        printf("*** Gateway's MAC address: %s\n", macs);

                        ssystem("ifconfig %s down", tundev);
                        ssystem("ifconfig %s hw ether %s", tundev, &macs[6]);
                        ssystem("ifconfig %s up", tundev);
                    }

#define DEBUG_LINE_MARKER '\r'
                }
                else if (uip.inbuf[0] == DEBUG_LINE_MARKER) {
                    fwrite(uip.inbuf + 1, inbufptr - 1, 1, stdout);
                }
                else if (is_sensible_string(uip.inbuf, inbufptr)) {
                    fwrite(uip.inbuf, inbufptr, 1, stdout);
                }
                else {
                    printf("Writing to tun  len: %d\n", inbufptr);

                    /*	print_packet(uip.inbuf, inbufptr);*/
                    if (write(outfd, uip.inbuf, inbufptr) != inbufptr) {
                        err(1, "serial_to_tun: write");
                    }
                }

                inbufptr = 0;
            }

            break;

        case SLIP_ESC:
            if (fread(&c, 1, 1, inslip) != 1) {
                clearerr(inslip);
                /* Put ESC back and give up! */
                ungetc(SLIP_ESC, inslip);
                return;
            }

            switch (c) {
                case SLIP_ESC_END:
                    c = SLIP_END;
                    break;

                case SLIP_ESC_ESC:
                    c = SLIP_ESC;
                    break;
            }

            /* FALLTHROUGH */
        default:
            uip.inbuf[inbufptr++] = c;
            break;
    }

    goto read_more;
}

unsigned char slip_buf[2000];
int slip_end, slip_begin;


void
slip_send(int fd, unsigned char c)
{
    if (slip_end >= sizeof(slip_buf)) {
        err(1, "slip_send overflow");
    }

    slip_buf[slip_end] = c;
    slip_end++;
}

int
slip_empty()
{
    return slip_end == 0;
}

void
slip_flushbuf(int fd)
{
    int n;

    if (slip_empty()) {
        return;
    }

    n = write(fd, slip_buf + slip_begin, (slip_end - slip_begin));

    if (n == -1 && errno != EAGAIN) {
        err(1, "slip_flushbuf write failed");
    }
    else if (n == -1) {
        PROGRESS("Q");		/* Outqueueis full! */
    }
    else {
        slip_begin += n;

        if (slip_begin == slip_end) {
            slip_begin = slip_end = 0;
        }
    }
}

void
write_to_serial(int outfd, void *inbuf, int len)
{
    u_int8_t *p = inbuf;
    int i;

    /*  printf("Got packet of length %d - write SLIP\n", len);*/
    /*  print_packet(p, len);*/

    /* It would be ``nice'' to send a SLIP_END here but it's not
     * really necessary.
     */
    /* slip_send(outfd, SLIP_END); */
    /*  printf("writing packet to serial!!!%d\n", len);*/
    for (i = 0; i < len; i++) {
        switch (p[i]) {
            case SLIP_END:
                slip_send(outfd, SLIP_ESC);
                slip_send(outfd, SLIP_ESC_END);
                break;

            case SLIP_ESC:
                slip_send(outfd, SLIP_ESC);
                slip_send(outfd, SLIP_ESC_ESC);
                break;

            default:
                slip_send(outfd, p[i]);
                break;
        }

    }

    slip_send(outfd, SLIP_END);
    PROGRESS("t");
}


/*
 * Read from tun, write to slip.
 */
void
tun_to_serial(int infd, int outfd)
{
    struct {
        unsigned char inbuf[2000];
    } uip;
    int size;

    if ((size = read(infd, uip.inbuf, 2000)) == -1) {
        err(1, "tun_to_serial: read");
    }

    write_to_serial(outfd, uip.inbuf, size);
}

#ifndef BAUDRATE
#define BAUDRATE B115200
#endif
speed_t b_rate = BAUDRATE;

void
stty_telos(int fd)
{
    struct termios tty;
    speed_t speed = b_rate;
    int i;

    if (tcflush(fd, TCIOFLUSH) == -1) {
        err(1, "tcflush");
    }

    if (tcgetattr(fd, &tty) == -1) {
        err(1, "tcgetattr");
    }

    cfmakeraw(&tty);

    /* Nonblocking read. */
    tty.c_cc[VTIME] = 0;
    tty.c_cc[VMIN] = 0;
    tty.c_cflag &= ~CRTSCTS;
    tty.c_cflag &= ~HUPCL;
    tty.c_cflag &= ~CLOCAL;

    cfsetispeed(&tty, speed);
    cfsetospeed(&tty, speed);

    if (tcsetattr(fd, TCSAFLUSH, &tty) == -1) {
        err(1, "tcsetattr");
    }

#if 1
    /* Nonblocking read and write. */
    /* if (fcntl(fd, F_SETFL, O_NONBLOCK) == -1) err(1, "fcntl"); */

    tty.c_cflag |= CLOCAL;

    if (tcsetattr(fd, TCSAFLUSH, &tty) == -1) {
        err(1, "tcsetattr");
    }

    i = TIOCM_DTR;

    if (ioctl(fd, TIOCMBIS, &i) == -1) {
        err(1, "ioctl");
    }

#endif

    usleep(10 * 1000);		/* Wait for hardware 10ms. */

    /* Flush input and output buffers. */
    if (tcflush(fd, TCIOFLUSH) == -1) {
        err(1, "tcflush");
    }
}

int
devopen(const char *dev, int flags)
{
    char t[1024];
    strcpy(t, "/dev/");
    strcat(t, dev);
    return open(t, flags);
}

#ifdef linux
#include <linux/if.h>
#include <linux/if_tun.h>

int
tun_alloc(char *dev)
{
    struct ifreq ifr;
    int fd, err;

    if ((fd = open("/dev/net/tun", O_RDWR)) < 0) {
        return -1;
    }

    memset(&ifr, 0, sizeof(ifr));

    /* Flags: IFF_TUN   - TUN device (no Ethernet headers)
     *        IFF_TAP   - TAP device
     *
     *        IFF_NO_PI - Do not provide packet information
     */
    ifr.ifr_flags = IFF_TAP | IFF_NO_PI;

    if (*dev != 0) {
        strncpy(ifr.ifr_name, dev, IFNAMSIZ);
    }

    if ((err = ioctl(fd, TUNSETIFF, (void *) &ifr)) < 0) {
        close(fd);
        return err;
    }

    strcpy(dev, ifr.ifr_name);
    return fd;
}
#else
int
tun_alloc(char *dev)
{
    return devopen(dev, O_RDWR);
}
#endif

const char *ipaddr;
const char *netmask;

void
cleanup(void)
{
    ssystem("ifconfig %s down", tundev);
#ifndef linux
    ssystem("sysctl -w net.ipv6.conf.all.forwarding=1");
#endif
    /* ssystem("arp -d %s", ipaddr); */
    ssystem("netstat -nr"
            " | awk '{ if ($2 == \"%s\") print \"route delete -net \"$1; }'"
            " | sh",
            tundev);
}

void
sigcleanup(int signo)
{
    fprintf(stderr, "signal %d\n", signo);
    exit(0);			/* exit(0) will call cleanup() */
}

static int got_sigalarm;
static int request_mac;

void
sigalarm(int signo)
{
    got_sigalarm = 1;
    return;
}

void
sigalarm_reset()
{
#ifdef linux
#define TIMEOUT (997*1000)
#else
#define TIMEOUT (2451*1000)
#endif
    ualarm(TIMEOUT, TIMEOUT);
    got_sigalarm = 0;
}

void
ifconf(const char *tundev, const char *ipaddr, const char *netmask)
{
    struct in_addr netname;
    netname.s_addr = inet_addr(ipaddr) & inet_addr(netmask);

#ifdef linux
    ssystem("ifconfig %s inet `hostname` up", tundev);

    if (strcmp(ipaddr, "0.0.0.0") != 0) {
        ssystem("route add -net %s netmask %s dev %s",
                inet_ntoa(netname), netmask, tundev);
    }

#else
    ssystem("ifconfig %s inet `hostname` %s up", tundev, ipaddr);

    if (strcmp(ipaddr, "0.0.0.0") != 0) {
        ssystem("route add -net %s -netmask %s -interface %s",
                inet_ntoa(netname), netmask, tundev);
    }

    ssystem("sysctl -w net.inet.ip.forwarding=1");
#endif /* !linux */

    ssystem("ifconfig %s\n", tundev);
}

int
main(int argc, char **argv)
{
    int c;
    int tunfd, slipfd;
    fd_set rset, wset;
    FILE *inslip;
    const char *siodev = NULL;
    int baudrate = -2;
    request_mac = 1;
    setvbuf(stdout, NULL, _IOLBF, 0); /* Line buffered output. */

    while ((c = getopt(argc, argv, "B:D:hs:t:")) != -1) {
        switch (c) {
            case 'B':
                baudrate = atoi(optarg);
                break;

            case 's':
                if (strncmp("/dev/", optarg, 5) == 0) {
                    siodev = optarg + 5;
                }
                else {
                    siodev = optarg;
                }

                break;

            case 't':
                if (strncmp("/dev/", optarg, 5) == 0) {
                    strcpy(tundev, optarg + 5);
                }
                else {
                    strcpy(tundev, optarg);
                }

                break;

            case '?':
            case 'h':
            default:
                errx(1, USAGE_STRING);
                break;
        }
    }

    argc -= (optind - 1);
    argv += (optind - 1);

    if (argc != 3 && argc != 4) {
        errx(1, USAGE_STRING);
    }

    ipaddr = argv[1];
    netmask = argv[2];
    circuit_addr = inet_addr(ipaddr);
    netaddr = inet_addr(ipaddr) & inet_addr(netmask);

    switch (baudrate) {
        case -2:
            break;			/* Use default. */

        case 9600:
            b_rate = B9600;
            break;

        case 19200:
            b_rate = B19200;
            break;

        case 38400:
            b_rate = B38400;
            break;

        case 57600:
            b_rate = B57600;
            break;

        case 115200:
            b_rate = B115200;
            break;

        default:
            err(1, "unknown baudrate %d", baudrate);
            break;
    }


    if (siodev != NULL) {
        slipfd = devopen(siodev, O_RDWR | O_NONBLOCK);

        if (slipfd == -1) {
            err(1, "can't open siodev ``/dev/%s''", siodev);
        }
    }
    else {
        static const char *siodevs[] = {
            "ttyUSB0", "cuaU0", "ucom0" /* linux, fbsd6, fbsd5 */
        };
        int i;

        for (i = 0; i < 3; i++) {
            siodev = siodevs[i];
            slipfd = devopen(siodev, O_RDWR | O_NONBLOCK);

            if (slipfd != -1) {
                break;
            }
        }

        if (slipfd == -1) {
            err(1, "can't open siodev");
        }
    }

    fprintf(stderr, "slip started on ``/dev/%s''\n", siodev);
    stty_telos(slipfd);
    slip_send(slipfd, SLIP_END);
    inslip = fdopen(slipfd, "r");

    if (inslip == NULL) {
        err(1, "main: fdopen");
    }

    tunfd = tun_alloc(tundev);
    printf("opening: %s", tundev);

    if (tunfd == -1) {
        err(1, "main: open");
    }

    fprintf(stderr, "opened device ``/dev/%s''\n", tundev);

    atexit(cleanup);
    signal(SIGHUP, sigcleanup);
    signal(SIGTERM, sigcleanup);
    signal(SIGINT, sigcleanup);
    signal(SIGALRM, sigalarm);
    ifconf(tundev, ipaddr, netmask);

    while (1) {
        int maxfd = 0;
        FD_ZERO(&rset);
        FD_ZERO(&wset);

        /* request mac address from gateway node for autoconfiguration of
           ethernet interface tap0 */
        if (request_mac) {
            slip_send(slipfd, '?');
            slip_send(slipfd, 'M');
            slip_send(slipfd, SLIP_END);
            request_mac = 0;
        }

        if (got_sigalarm) {
            /* Send "?IPA". */
            slip_send(slipfd, '?');
            slip_send(slipfd, 'I');
            slip_send(slipfd, 'P');
            slip_send(slipfd, 'A');
            slip_send(slipfd, SLIP_END);
            got_sigalarm = 0;
        }

        if (!slip_empty()) {		/* Anything to flush? */
            FD_SET(slipfd, &wset);
        }

        FD_SET(slipfd, &rset);	/* Read from slip ASAP! */

        if (slipfd > maxfd) {
            maxfd = slipfd;
        }

        /* We only have one packet at a time queued for slip output. */
        if (slip_empty()) {
            FD_SET(tunfd, &rset);

            if (tunfd > maxfd) {
                maxfd = tunfd;
            }
        }

        int ret = select(maxfd + 1, &rset, &wset, NULL, NULL);

        if (ret == -1 && errno != EINTR) {
            err(1, "select");
        }
        else if (ret > 0) {
            if (FD_ISSET(slipfd, &rset)) {
                serial_to_tun(inslip, tunfd);
            }

            if (FD_ISSET(slipfd, &wset)) {
                slip_flushbuf(slipfd);
                sigalarm_reset();
            }

            if (slip_empty() && FD_ISSET(tunfd, &rset)) {
                tun_to_serial(tunfd, slipfd);
                slip_flushbuf(slipfd);
                sigalarm_reset();
            }
        }
    }
}