/**
 * (C) 2007-21 - ntop.org and contributors
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.    See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not see see <http://www.gnu.org/licenses/>
 *
 */

#include "n2n.h"

/* *************************************************** */

/** maximum length of command line arguments */
#define MAX_CMDLINE_BUFFER_LENGTH        4096

/** maximum length of a line in the configuration file */
#define MAX_CONFFILE_LINE_LENGTH         1024

/* ***************************************************** */

#ifdef HAVE_LIBCAP

#include <sys/capability.h>
#include <sys/prctl.h>
#include "network_traffic_filter.h"

static cap_value_t cap_values[] = {
    //CAP_NET_RAW,            /* Use RAW and PACKET sockets */
    CAP_NET_ADMIN         /* Needed to performs routes cleanup at exit */
};

int num_cap = sizeof(cap_values)/sizeof(cap_value_t);
#endif

// forward declaration for use in main()
void send_register_super (n2n_edge_t *eee);
void send_query_peer (n2n_edge_t * eee, const n2n_mac_t dst_mac);


/* ***************************************************** */

/** Find the address and IP mode for the tuntap device.
 *
 *    s is of the form:
 *
 * ["static"|"dhcp",":"] (<host>|<ip>) [/<cidr subnet mask>]
 *
 * for example        static:192.168.8.5/24
 *
 * Fill the parts of the string into the fileds, ip_mode only if
 * present. All strings are NULL terminated.
 *
 *    return 0 on success and -1 on error
 */
static int scan_address (char * ip_addr, size_t addr_size,
                         char * netmask, size_t netmask_size,
                         char * ip_mode, size_t mode_size,
                         char * s) {

    int retval = -1;
    char * start;
    char * end;
    int bitlen = N2N_EDGE_DEFAULT_CIDR_NM;

    if((NULL == s) || (NULL == ip_addr) || (NULL == netmask)) {
        return -1;
    }

    memset(ip_addr, 0, addr_size);
    memset(netmask, 0, netmask_size);

    start = s;
    end = strpbrk(s, ":");

    if(end) {
        // colon is present
        if(ip_mode) {
            memset(ip_mode, 0, mode_size);
            strncpy(ip_mode, start, (size_t)MIN(end - start, mode_size - 1));
        }
        start = end + 1;
    } else {
        // colon is not present
    }
    // start now points to first address character
    retval = 0; // we have got an address

    end = strpbrk(start, "/");

    if(!end)
        // no slash present -- default end
        end = s + strlen(s);

    strncpy(ip_addr, start, (size_t)MIN(end - start, addr_size - 1)); // ensure NULL term

    if(end) {
        // slash is present

        // now, handle the sub-network address
        sscanf(end + 1, "%u", &bitlen);
        bitlen = htobe32(bitlen2mask(bitlen));
        inet_ntop(AF_INET, &bitlen, netmask, netmask_size);
    }

    return retval;
}

/* *************************************************** */

static void help (int level) {

    printf("\n");
    print_n2n_version();

    if(level == 0) /* short help */ {

        printf("   basic usage:  edge <config file> (see edge.conf)\n"
               "\n"
               "            or   edge "
               " -c <community name> "
               "\n                      "
               " -l <supernode host>:<port> "
               "\n                      "
               "[-a <tap IP address>] "
               "\n                      "
#if defined(N2N_CAN_NAME_IFACE)
               "[-d <tap device name>] "
               "\n                      "
#endif
               "[-k <encryption key>] "
               "\n"
               "\n  -h    shows a quick reference including all available options"
               "\n --help gives a detailed parameter description"
               "\n   man  files for n2n, edge, and superndode contain in-depth information"
               "\n\n");

    } else if(level == 1) /* quick reference */ {

        printf(" general usage:  edge <config file> (see edge.conf)\n"
           "\n"
               "            or   edge "
               " -c <community name>"
               " -l <supernode host:port>"
            "\n                      "
               "[-p <local port>] "
#ifdef __linux__
               "[-T <type of service>] "
#endif
#ifndef __APPLE__
               "[-D] "
#endif
               "[-S] "
            "\n options for under-   "
               "[-i <registration interval>]"
               "[-L <registration ttl>]"
            "\n lying connection     "
               "[-k <key>] "
               "[-A<cipher>] "
               "[-H] "
               "[-z<compression>]"
          "\n\n tap device and       "
               "[-a [static:|dhcp:]<tap IP address>[/<cidr suffix>]] "
            "\n overlay network      "
               "[-m <tap MAC address>] "
#if defined(N2N_CAN_NAME_IFACE)
               "[-d <tap device name>] "
#endif
            "\n configuration        "
               "[-M <tap MTU>] "
               "[-r] "
               "[-E] "
               "[-I <edge description>] "
            "\n                      "
               "[-R <rule string>] "
#ifdef WIN32
               "[-x <metric>] "
#endif
          "\n\n local options        "
#ifndef WIN32
               "[-f] "
#endif
               "[-t <management port>] "
               "[-v] "
               "[-n <cidr:gateway>] "
#ifndef WIN32
            "\n                      "
               "[-u <numerical user id>]"
               "[-g <numerical group id>]"
#endif
          "\n\n environment          "
               "N2N_KEY   instead of [-k <key>]"
          "\n variables            "
          "\n                      "

          "\n meaning of the       "
#ifndef __APPLE__
                                  "[-D]  enable PMTU discovery"
#endif
          "\n flag options         [-S]  do not connect p2p, always use supernode"
          "\n                      [-H]  enable header encryption"
          "\n                      [-r]  enable packet forwarding through n2n community"
          "\n                      [-E]  accept multicast MAC addresses"
#ifndef WIN32
          "\n                      [-f]  do not fork but run in foreground"
#endif
          "\n                      [-v]  make more verbose, repeat as required"
          "\n                      "

          "\n  -h    shows this quick reference including all available options"
          "\n --help gives a detailed parameter description"
          "\n   man  files for n2n, edge, and superndode contain in-depth information"
          "\n\n");

    } else /* long help */ {

        printf(" general usage:  edge <config file> (see edge.conf)\n"
               "\n"
               "            or   edge  -c <community name> -l <supernode host:port>\n"
               "                      [further optional command line parameters]\n\n"
        );
        printf (" OPTIONS FOR THE UNDERLYING NETWORK CONNECTION\n");
        printf (" ---------------------------------------------\n\n");
        printf(" -c <community>    | n2n community name the edge belongs to\n");
        printf(" -l <host:port>    | supernode ip address or name, and port\n");
        printf(" -p <local port>   | fixed local UDP port\n");
#ifdef __linux__
        printf(" -T <tos>          | TOS for packets, e.g. 0x48 for SSH like priority\n");
#endif
#ifndef __APPLE__
        printf(" -D                | enable PMTU discovery, it can reduce fragmentation but\n"
               "                   | causes connections to stall if not properly supported\n");
#endif
        printf(" -S                | do not connect p2p, always use the supernode\n");
        printf(" -i <reg_interval> | registration interval, for NAT hole punching (default\n"
               "                   | 20 seconds)\n");
        printf(" -L <reg_ttl>      | TTL for registration packet for NAT hole punching through\n"
               "                   | supernode (default 0 for not set)\n");
        printf(" -k <key>          | encryption key (ASCII) - also N2N_KEY=<key>\n");
        printf(" -A1               | disable payload encryption, do not use with key, defaults\n"
               "                   | to AES then\n");
        printf(" -A2 ... -A5 or -A | choose a cipher for payload encryption, requires a key,\n"
               "                   | -A2 = Twofish, -A3 or -A (deprecated) = AES (default),\n"
               "                   | -A4 = ChaCha20, -A5 = Speck-CTR\n");
        printf(" -H                | use header encryption, supernode needs fixed community\n");
        printf(" -z1 ... -z2 or -z | compress outgoing data packets, -z1 or -z lzo1x,\n"
               "                   | "
#ifdef N2N_HAVE_ZSTD
                                     "-z2 = zstd, "
#endif
                                     "disabled by default\n");
        printf ("\n");
        printf (" TAP DEVICE AND OVERLAY NETWORK CONFIGURATION\n");
        printf (" --------------------------------------------\n\n");
        printf(" -a [mode]<ip>[/n] | interface address and optional CIDR subnet, default '/24',\n"
               "                   | mode = [static|dhcp]:, for DHCP use '-r -a dhcp:0.0.0.0',\n"
               "                   | edge draws IP address from supernode if no '-a ...' given\n");
        printf(" -m <mac>          | fixed MAC address for the TAP interface, e.g.\n"
               "                   | '-m 10:20:30:40:50:60', random otherwise\n");
#if defined(N2N_CAN_NAME_IFACE)
        printf(" -d <device>       | TAP device name\n");
#endif
        printf(" -M <mtu>          | specify n2n MTU of TAP interface, default %d\n", DEFAULT_MTU);
        printf(" -r                | enable packet forwarding through n2n community\n");
        printf(" -E                | accept multicast MAC addresses, drop by default\n");
        printf(" -I <description>  | annotate the edge's description used for easier\n"
               "                   | identification in management port output\n");
        printf(" -R <rule>         | drop or accept packets by rules, can be set multiple times\n");
        printf("                   | rule format:    'src_ip/n:[s_port,e_port],...\n"
               "                   |    |on same|  ...dst_ip/n:[s_port,e_port],...\n"
               "                   |    | line  |  ...TCP+/-,UDP+/-,ICMP+/-'\n");
#ifdef WIN32
        printf(" -x <metric>       | set TAP interface metric, defaults to 0 (auto),\n"
               "                   | e.g. set to 1 for better multiplayer game detection\n");
#endif
        printf ("\n");
        printf (" LOCAL OPTIONS\n");
        printf (" -------------\n\n");
#ifndef WIN32
        printf(" -f                | do not fork and run as a daemon, rather run in foreground\n");
#endif
        printf(" -t <port>         | management UDP port, for multiple edges on a machine\n");
        printf(" -v                | make more verbose, repeat as required\n");
        printf(" -n <cidr:gateway> | route an IPv4 network via the gateway, use 0.0.0.0/0 for\n"
               "                   | the default gateway, can be set multiple times\n");
#ifndef WIN32
        printf(" -u <UID>          | numeric user ID to use when privileges are dropped\n");
        printf(" -g <GID>          | numeric group ID to use when privileges are dropped\n");
#endif
        printf ("\n");
        printf (" ENVIRONMENT VARIABLES\n");
        printf (" ---------------------\n\n");
        printf("     N2N_KEY       | encryption key (ASCII), not with '-k ...'\n");
#ifdef WIN32
        printf ("\n");
        printf (" AVAILABLE TAP ADAPTERS\n");
        printf (" ----------------------\n\n");
        win_print_available_adapters();
#endif
        printf ("\n"
                "\n  -h    shows a quick reference including all available options"
                "\n --help gives this detailed parameter description"
                "\n   man  files for n2n, edge, and superndode contain in-depth information"
                "\n\n");
    }

    exit(0);
}

/* *************************************************** */

static void setPayloadCompression (n2n_edge_conf_t *conf, int compression) {

    /* even though 'compression' and 'conf->compression' share the same encoding scheme,
     * a switch-statement under conditional compilation is used to sort out the
     * unsupported optarguments */
    switch (compression) {
        case 1: {
            conf->compression = N2N_COMPRESSION_ID_LZO;
            break;
        }
#ifdef N2N_HAVE_ZSTD
        case 2: {
            conf->compression = N2N_COMPRESSION_ID_ZSTD;
            break;
        }
#endif
        default: {
            conf->compression = N2N_COMPRESSION_ID_NONE;
            // internal comrpession scheme numbering differs from cli counting by one, hence plus one
            // (internal: 0 == invalid, 1 == none, 2 == lzo, 3 == zstd)
            traceEvent(TRACE_NORMAL, "the %s compression given by -z_ option is not supported in this version.", compression_str(compression + 1));
            exit(1); // to make the user aware
        }
    }
}

/* *************************************************** */

static void setPayloadEncryption (n2n_edge_conf_t *conf, int cipher) {

    /* even though 'cipher' and 'conf->transop_id' share the same encoding scheme,
     * a switch-statement under conditional compilation is used to sort out the
     * unsupported ciphers */
    switch (cipher) {
        case 1: {
            conf->transop_id = N2N_TRANSFORM_ID_NULL;
            break;
        }

        case 2: {
            conf->transop_id = N2N_TRANSFORM_ID_TWOFISH;
            break;
        }

        case 3: {
            conf->transop_id = N2N_TRANSFORM_ID_AES;
            break;
        }

        case 4: {
            conf->transop_id = N2N_TRANSFORM_ID_CHACHA20;
            break;
        }

        case 5: {
            conf->transop_id = N2N_TRANSFORM_ID_SPECK;
            break;
        }

        default: {
            conf->transop_id = N2N_TRANSFORM_ID_INVAL;
            traceEvent(TRACE_NORMAL, "the %s cipher given by -A_ option is not supported in this version.", transop_str(cipher));
            exit(1);
        }
    }
}

/* *************************************************** */

static int setOption (int optkey, char *optargument, n2n_tuntap_priv_config_t *ec, n2n_edge_conf_t *conf) {

    /* traceEvent(TRACE_NORMAL, "Option %c = %s", optkey, optargument ? optargument : ""); */

    switch(optkey) {
        case 'a': /* IP address and mode of TUNTAP interface */ {
            scan_address(ec->ip_addr, N2N_NETMASK_STR_SIZE,
                                     ec->netmask, N2N_NETMASK_STR_SIZE,
                                     ec->ip_mode, N2N_IF_MODE_SIZE,
                                     optargument);
            break;
        }

        case 'c': /* community as a string */ {
            memset(conf->community_name, 0, N2N_COMMUNITY_SIZE);
            strncpy((char *)conf->community_name, optargument, N2N_COMMUNITY_SIZE);
            conf->community_name[N2N_COMMUNITY_SIZE - 1] = '\0';
            break;
        }

        case 'E': /* multicast ethernet addresses accepted. */ {
            conf->drop_multicast = 0;
            traceEvent(TRACE_DEBUG, "Enabling ethernet multicast traffic");
            break;
        }

#ifndef WIN32
        case 'u': /* unprivileged uid */ {
            ec->userid = atoi(optargument);
            break;
        }

        case 'g': /* unprivileged uid */ {
            ec->groupid = atoi(optargument);
            break;
        }
#endif

#ifndef WIN32
        case 'f' : /* do not fork as daemon */ {
            ec->daemon = 0;
            break;
        }
#endif /* #ifndef WIN32 */

        case 'm' : /* TUNTAP MAC address */ {
            strncpy(ec->device_mac, optargument, N2N_MACNAMSIZ);
            ec->device_mac[N2N_MACNAMSIZ - 1] = '\0';
            break;
        }

        case 'M' : /* TUNTAP MTU */ {
            ec->mtu = atoi(optargument);
            break;
        }

#ifndef __APPLE__
        case 'D' : /* enable PMTU discovery */ {
            conf->disable_pmtu_discovery = 0;
            break;
        }
#endif

        case 'k': /* encrypt key */ {
            if(conf->encrypt_key) free(conf->encrypt_key);
            conf->encrypt_key = strdup(optargument);
            traceEvent(TRACE_DEBUG, "encrypt_key = '%s'\n", conf->encrypt_key);
            break;
        }

        case 'r': /* enable packet routing across n2n endpoints */ {
            conf->allow_routing = 1;
            break;
        }

        case 'A': {
            int cipher;

            if(optargument) {
                cipher = atoi(optargument);
            } else {
                traceEvent(TRACE_NORMAL, "the use of the solitary -A switch is deprecated and might not be supported in future versions. "
                           "please use -A3 instead to choose a the AES cipher for payload encryption.");

                cipher = N2N_TRANSFORM_ID_AES; // default, if '-A' only
            }

            setPayloadEncryption(conf, cipher);
            break;
        }

        case 'H': /* indicate header encryption */ {
            /* we cannot be sure if this gets parsed before the community name is set.
             * so, only an indicator is set, action is taken later*/
            conf->header_encryption = HEADER_ENCRYPTION_ENABLED;
            break;
        }

        case 'z': {
            int compression;

            if(optargument) {
                compression = atoi(optargument);
            } else
                compression = 1; // default, if '-z' only, equals -z1

            setPayloadCompression(conf, compression);
            break;
        }

        case 'l': /* supernode-list */
            if(optargument) {
                if(edge_conf_add_supernode(conf, optargument) != 0) {
                    traceEvent(TRACE_WARNING, "Too many supernodes!");
                    exit(1);
                }
                break;
            }

        case 'i': /* supernode registration interval */
            conf->register_interval = atoi(optargument);
            break;

        case 'L': /* supernode registration interval */
            conf->register_ttl = atoi(optarg);
            break;

#if defined(N2N_CAN_NAME_IFACE)
        case 'd': /* TUNTAP name */ {
            strncpy(ec->tuntap_dev_name, optargument, N2N_IFNAMSIZ);
            ec->tuntap_dev_name[N2N_IFNAMSIZ - 1] = '\0';
            break;
        }
#endif

        case 'I': /* Device Description (hint) */ {
            memset(conf->dev_desc, 0, N2N_DESC_SIZE);
            /* reserve possible last char as null terminator. */
            strncpy((char *)conf->dev_desc, optargument, N2N_DESC_SIZE-1);
            break;
        }

        case 'p': {
            conf->local_port = atoi(optargument);

            if(conf->local_port == 0) {
                traceEvent(TRACE_WARNING, "Bad local port format");
                break;
            }

            break;
        }

        case 't': {
            conf->mgmt_port = atoi(optargument);
            break;
        }

#ifdef __linux__
        case 'T': {
            if((optargument[0] == '0') && (optargument[1] == 'x'))
                conf->tos = strtol(&optargument[2], NULL, 16);
            else
                conf->tos = atoi(optargument);

            break;
        }
#endif

        case 'n': {
            char cidr_net[64], gateway[64];
            n2n_route_t route;

            if(sscanf(optargument, "%63[^/]/%hhd:%63s", cidr_net, &route.net_bitlen, gateway) != 3) {
                traceEvent(TRACE_WARNING, "Bad cidr/gateway format '%d'. See -h.", optargument);
                break;
            }

            route.net_addr = inet_addr(cidr_net);
            route.gateway = inet_addr(gateway);

            if((route.net_bitlen < 0) || (route.net_bitlen > 32)) {
                traceEvent(TRACE_WARNING, "Bad prefix '%d' in '%s'", route.net_bitlen, optargument);
                break;
            }

            if(route.net_addr == INADDR_NONE) {
                traceEvent(TRACE_WARNING, "Bad network '%s' in '%s'", cidr_net, optargument);
                break;
            }

            if(route.gateway == INADDR_NONE) {
                traceEvent(TRACE_WARNING, "Bad gateway '%s' in '%s'", gateway, optargument);
                break;
            }

            traceEvent(TRACE_DEBUG, "Adding %s/%d via %s", cidr_net, route.net_bitlen, gateway);

            conf->routes = realloc(conf->routes, sizeof(struct n2n_route) * (conf->num_routes + 1));
            conf->routes[conf->num_routes] = route;
            conf->num_routes++;

            break;
        }

        case 'S': {
            conf->allow_p2p = 0;
            break;
        }

        case 'h': /* quick reference */ {
            help(1);
            break;
        }

        case '@': /* long help */ {
            help(2);
            break;
        }

        case 'v': /* verbose */
            setTraceLevel(getTraceLevel() + 1);
            break;

        case 'R': /* network traffic filter */ {
            filter_rule_t *new_rule = malloc(sizeof(filter_rule_t));
            memset(new_rule, 0, sizeof(filter_rule_t));

            if(process_traffic_filter_rule_str(optargument, new_rule)) {
                HASH_ADD(hh, conf->network_traffic_filter_rules, key, sizeof(filter_rule_key_t), new_rule);
            } else {
                free(new_rule);
                traceEvent(TRACE_WARNING, "Invalid filter rule: %s", optargument);
                return(-1);
            }
            break;
        }
#ifdef WIN32
        case 'x': {
            conf->metric = atoi(optargument);
            ec->metric = atoi(optargument);
            break;
        }
#endif
        default: {
            traceEvent(TRACE_WARNING, "Unknown option -%c: Ignored", (char)optkey);
            return(-1);
        }
    }

    return(0);
}

/* *********************************************** */


static const struct option long_options[] =
    {
        { "community",         required_argument, NULL, 'c' },
        { "supernode-list",    required_argument, NULL, 'l' },
        { "tap-device",        required_argument, NULL, 'd' },
        { "euid",              required_argument, NULL, 'u' },
        { "egid",              required_argument, NULL, 'g' },
        { "help"     ,         no_argument,       NULL, '@' }, /* special character '@' to identify long help case */
        { "verbose",           no_argument,       NULL, 'v' },
        { NULL,                0,                 NULL,  0  }
    };

/* *************************************************** */

/* read command line options */
static int loadFromCLI (int argc, char *argv[], n2n_edge_conf_t *conf, n2n_tuntap_priv_config_t *ec) {

    u_char c;

    while ((c = getopt_long(argc, argv,
                            "k:a:bc:Eu:g:m:M:s:d:l:p:fvhrt:i:I:SDL:z::A::Hn:R:"
#ifdef __linux__
                            "T:"
#endif
#ifdef WIN32
                            "x:"
#endif
                            ,
                            long_options, NULL)) != '?') {

        if(c == 255) break;
        setOption(c, optarg, ec, conf);

    }

    return 0;
}

/* *************************************************** */

static char *trim (char *s) {

    char *end;

    while(isspace(s[0]) || (s[0] == '"') || (s[0] == '\'')) s++;
    if(s[0] == 0) return s;

    end = &s[strlen(s) - 1];
    while(end > s
                && (isspace(end[0])|| (end[0] == '"') || (end[0] == '\'')))
        end--;
    end[1] = 0;

    return s;
}

/* *************************************************** */

/* parse the configuration file */
static int loadFromFile (const char *path, n2n_edge_conf_t *conf, n2n_tuntap_priv_config_t *ec) {

    char buffer[4096], *line;
    char *line_vec[3];
    int tmp;

    FILE *fd;

    fd = fopen(path, "r");

    if(fd == NULL) {
        traceEvent(TRACE_WARNING, "Config file %s not found", path);
        return -1;
    }

    // we mess around with optind, better save it
    tmp = optind;

    while((line = fgets(buffer, sizeof(buffer), fd)) != NULL) {
        line = trim(line);

        if(strlen(line) < 2 || line[0] == '#')
            continue;

        // executable, cannot be omitted, content can be anything
        line_vec[0] = line;
        // first token, e.g. `-p` or `-A3', eventually followed by a whitespace or '=' delimiter
        line_vec[1] = strtok(line, "\t =");
        // separate parameter option, if present
        line_vec[2] = strtok(NULL, "");
        if(line_vec[2])
            line_vec[2] = trim(line_vec[2]);
        // not to duplicate the option parser code, call loadFromCLI and pretend we have no option read yet at all
        optind = 0;
        // if second token present (optional argument, not part of first), then announce 3 vector members
        loadFromCLI(line_vec[2] ? 3 : 2, line_vec, conf, ec);
    }

    fclose(fd);
    optind = tmp;

    return 0;
}

/* ************************************** */

static void daemonize () {
#ifndef WIN32
    int childpid;

    traceEvent(TRACE_NORMAL, "Parent process is exiting (this is normal)");

    signal(SIGPIPE, SIG_IGN);
    signal(SIGHUP,  SIG_IGN);
    signal(SIGCHLD, SIG_IGN);
    signal(SIGQUIT, SIG_IGN);

    if((childpid = fork()) < 0)
        traceEvent(TRACE_ERROR, "Occurred while daemonizing (errno=%d)",
                   errno);
    else {
        if(!childpid) { /* child */
            int rc;

            //traceEvent(TRACE_NORMAL, "Bye bye: I'm becoming a daemon...");
            rc = chdir("/");
            if(rc != 0)
                traceEvent(TRACE_ERROR, "Error while moving to / directory");

            setsid();    /* detach from the terminal */

            fclose(stdin);
            fclose(stdout);
            /* fclose(stderr); */

            /*
             * clear any inherited file mode creation mask
             */
            //umask(0);

            /*
             * Use line buffered stdout
             */
            /* setlinebuf (stdout); */
            setvbuf(stdout, (char *)NULL, _IOLBF, 0);
        } else /* father */
            exit(0);
    }
#endif
}

/* *************************************************** */

static int keep_on_running;

#if defined(__linux__) || defined(WIN32)
#ifdef WIN32
BOOL WINAPI term_handler(DWORD sig)
#else
    static void term_handler(int sig)
#endif
{
    static int called = 0;

    if(called) {
        traceEvent(TRACE_NORMAL, "Ok I am leaving now");
        _exit(0);
    } else {
        traceEvent(TRACE_NORMAL, "Shutting down...");
        called = 1;
    }

    keep_on_running = 0;
#ifdef WIN32
    return(TRUE);
#endif
}
#endif /* defined(__linux__) || defined(WIN32) */

/* *************************************************** */

/** Entry point to program from kernel. */
int main (int argc, char* argv[]) {

    int rc;
    tuntap_dev tuntap;            /* a tuntap device */
    n2n_edge_t *eee;              /* single instance for this program */
    n2n_edge_conf_t conf;         /* generic N2N edge config */
    n2n_tuntap_priv_config_t ec;  /* config used for standalone program execution */
    uint8_t runlevel = 0;         /* bootstrap: runlevel */
    uint8_t seek_answer = 1;      /*            expecting answer from supernode */
    time_t now_time, last_action; /*            timeout */
    macstr_t mac_buf;             /*            output mac address */
    fd_set socket_mask;           /*            for supernode answer */
    struct timeval wait_time;     /*            timeout for sn answer */

#ifndef WIN32
    struct passwd *pw = NULL;
#endif
#ifdef HAVE_LIBCAP
    cap_t caps;
#endif
#ifdef WIN32
    initWin32();
#endif

    /* Defaults */
    edge_init_conf_defaults(&conf);
    memset(&ec, 0, sizeof(ec));
    ec.mtu = DEFAULT_MTU;
    ec.daemon = 1;        /* By default run in daemon mode. */

#ifndef WIN32
    if(((pw = getpwnam("n2n")) != NULL) ||
       ((pw = getpwnam("nobody")) != NULL)) {
        ec.userid = pw->pw_uid;
        ec.groupid = pw->pw_gid;
    }
#endif

#ifdef WIN32
    ec.tuntap_dev_name[0] = '\0';
    ec.metric = 0;
#else
    snprintf(ec.tuntap_dev_name, sizeof(ec.tuntap_dev_name), N2N_EDGE_DEFAULT_DEV_NAME);
#endif
    snprintf(ec.netmask, sizeof(ec.netmask), N2N_EDGE_DEFAULT_NETMASK);

    if((argc >= 2) && (argv[1][0] != '-')) {
        rc = loadFromFile(argv[1], &conf, &ec);
        if(argc > 2)
            rc = loadFromCLI(argc, argv, &conf, &ec);
    } else if(argc > 1)
        rc = loadFromCLI(argc, argv, &conf, &ec);
    else

#ifdef WIN32
        // load from current directory
        rc = loadFromFile("edge.conf", &conf, &ec);
#else
        rc = -1;
#endif

    if(conf.transop_id == N2N_TRANSFORM_ID_NULL) {
        if(conf.encrypt_key) {
            /* make sure that AES is default cipher if key only (and no cipher) is specified */
            traceEvent(TRACE_WARNING, "Switching to AES as key was provided.");
            conf.transop_id = N2N_TRANSFORM_ID_AES;
        }
    }

    if(rc < 0)
        help(0); /* short help */

    if(edge_verify_conf(&conf) != 0)
        help(0); /* short help */

    traceEvent(TRACE_NORMAL, "Starting n2n edge %s %s", PACKAGE_VERSION, PACKAGE_BUILDDATE);

#if defined(HAVE_OPENSSL_1_1)
    traceEvent(TRACE_NORMAL, "Using %s", OpenSSL_version(0));
#endif

    traceEvent(TRACE_NORMAL, "Using compression: %s.", compression_str(conf.compression));
    traceEvent(TRACE_NORMAL, "Using %s cipher.", transop_str(conf.transop_id));

    /* Random seed */
    n2n_srand (n2n_seed());

#ifndef WIN32
    /* If running suid root then we need to setuid before using the force. */
    if(setuid(0) != 0)
        traceEvent(TRACE_ERROR, "Unable to become root [%u/%s]", errno, strerror(errno));
    /* setgid(0); */
#endif

    if(conf.encrypt_key && !strcmp((char*)conf.community_name, conf.encrypt_key))
        traceEvent(TRACE_WARNING, "Community and encryption key must differ, otherwise security will be compromised");

    if((eee = edge_init(&conf, &rc)) == NULL) {
        traceEvent(TRACE_ERROR, "Failed in edge_init");
        exit(1);
    }
    memcpy(&(eee->tuntap_priv_conf), &ec, sizeof(ec));

    if((0 == strcmp("static", eee->tuntap_priv_conf.ip_mode)) ||
         ((eee->tuntap_priv_conf.ip_mode[0] == '\0') && (eee->tuntap_priv_conf.ip_addr[0] != '\0'))) {
        traceEvent(TRACE_NORMAL, "Use manually set IP address.");
        eee->conf.tuntap_ip_mode = TUNTAP_IP_MODE_STATIC;
    } else if(0 == strcmp("dhcp", eee->tuntap_priv_conf.ip_mode)) {
        traceEvent(TRACE_NORMAL, "Obtain IP from other edge DHCP services.");
        eee->conf.tuntap_ip_mode = TUNTAP_IP_MODE_DHCP;
    } else {
        traceEvent(TRACE_NORMAL, "Automatically assign IP address by supernode.");
        eee->conf.tuntap_ip_mode = TUNTAP_IP_MODE_SN_ASSIGN;
    }

    // mini main loop for bootstrap, not using main loop code because some of its mechanisms do not fit in here
    // for the sake of quickly establishing connection. REVISIT when a more elegant way to re-use main loop code
    // is found

    // if more than one supernode given, find at least one who is alive to faster establish connection
    if(HASH_COUNT(eee->conf.supernodes) <= 1) {
        // skip the initial supernode ping
        traceEvent(TRACE_DEBUG, "Skip PING to supernode.");
        runlevel = 2;
    }

    eee->last_sup = 1; /* to prevent gratuitous arp packet */
    eee->curr_sn = eee->conf.supernodes;

    while(runlevel < 5) {

        now_time = time(NULL);

        // we do not use switch-case because we also check for 'greater than'

        if(runlevel == 0) { /* PING to all known supernodes */
            last_action = now_time;
            eee->sn_pong = 0;
            send_query_peer(eee, null_mac);
            traceEvent(TRACE_NORMAL, "Send PING to supernodes.");
            runlevel++;
        }

        if(runlevel == 1) { /* PING has been sent to all known supernodes */
            if(eee->sn_pong) {
                // first answer
                eee->sn_pong = 0;
                sn_selection_sort(&(eee->conf.supernodes));
                eee->curr_sn = eee->conf.supernodes;
                traceEvent(TRACE_NORMAL, "Received first PONG from supernode [%s].", eee->curr_sn->ip_addr);
                runlevel++;
            }
            if(last_action <= (now_time - BOOTSTRAP_TIMEOUT)) {
                // timeout
                runlevel--;
                // skip waiting for answer to direcly go to send PING again
                seek_answer = 0;
                traceEvent(TRACE_DEBUG, "PONG timeout.");
            }
        }

        // by the way, have every later PONG cause the remaining (!) list to be sorted because the entries
        // before have already been tried; as opposed to initial PONG, do not change curr_sn
        if(runlevel > 1) {
            if(eee->sn_pong) {
                eee->sn_pong = 0;
                if(eee->curr_sn->hh.next) {
                    sn_selection_sort((peer_info_t**)&(eee->curr_sn->hh.next));
                    traceEvent(TRACE_DEBUG, "Received additional PONG from supernode.");
                    // here, it is hard to detemine from which one, so no details to output
                }
            }
        }

        if(runlevel == 2) { /* send REGISTER_SUPER to get auto ip address from a supernode */
            if(eee->conf.tuntap_ip_mode == TUNTAP_IP_MODE_SN_ASSIGN) {
                last_action = now_time;
                eee->sn_wait = 1;
                send_register_super(eee);
                runlevel++;
                traceEvent(TRACE_NORMAL, "Send REGISTER_SUPER to supernode [%s] asking for IP address.",
                                         eee->curr_sn->ip_addr);
            } else {
                runlevel += 2; /* skip waiting for TUNTAP IP address */
                traceEvent(TRACE_DEBUG, "Skip auto IP address asignment.");
            }
        }

        if(runlevel == 3) { /* REGISTER_SUPER to get auto ip address from a sn has been sent */
            if(!eee->sn_wait) { /* TUNTAP IP address received */
                runlevel++;
                traceEvent(TRACE_NORMAL, "Received REGISTER_SUPER_ACK from supernode for IP address asignment.");
                // it should be from curr_sn, but we can't determine definitely here, so no details to output
            }
            if(last_action <= (now_time - BOOTSTRAP_TIMEOUT)) {
                // timeout, so try next supernode
                if(eee->curr_sn->hh.next)
                    eee->curr_sn = eee->curr_sn->hh.next;
                else
                    eee->curr_sn = eee->conf.supernodes;
                runlevel--;
                // skip waiting for answer to direcly go to send REGISTER_SUPER again
                seek_answer = 0;
                traceEvent(TRACE_DEBUG, "REGISTER_SUPER_ACK timeout.");
            }
        }

        if(runlevel == 4) { /* configure the TUNTAP device */
            if(tuntap_open(&tuntap, eee->tuntap_priv_conf.tuntap_dev_name, eee->tuntap_priv_conf.ip_mode,
                           eee->tuntap_priv_conf.ip_addr, eee->tuntap_priv_conf.netmask,
                           eee->tuntap_priv_conf.device_mac, eee->tuntap_priv_conf.mtu
#ifdef WIN32
                           , eee->tuntap_priv_conf.metric
#endif
                                                           ) < 0)
                exit(1);
            memcpy(&eee->device, &tuntap, sizeof(tuntap));
            traceEvent(TRACE_NORMAL, "Created local tap device IP: %s, Mask: %s, MAC: %s",
                                     eee->tuntap_priv_conf.ip_addr,
                                     eee->tuntap_priv_conf.netmask,
                                     macaddr_str(mac_buf, eee->device.mac_addr));
            runlevel = 5;
            // no more answers required
            seek_answer = 0;
        }

        // we usually wait for some answer, there however are exceptions when going back to a previous runlevel
        if(seek_answer) {
            FD_ZERO(&socket_mask);
            FD_SET(eee->udp_sock, &socket_mask);
            wait_time.tv_sec = BOOTSTRAP_TIMEOUT;
            wait_time.tv_usec = 0;

            if(select(eee->udp_sock + 1, &socket_mask, NULL, NULL, &wait_time) > 0) {
                if(FD_ISSET(eee->udp_sock, &socket_mask)) {
                    readFromIPSocket(eee, eee->udp_sock);
                }
            }
        }
        seek_answer = 1;
    }
    eee->sn_wait = 1;
    eee->last_register_req = 0;
    eee->last_sup = 0; /* to allow gratuitous arp packet after regular REGISTER_SUPER_ACK */

#ifndef WIN32
    if(eee->tuntap_priv_conf.daemon) {
        setUseSyslog(1); /* traceEvent output now goes to syslog. */
        daemonize();
    }
#endif /* #ifndef WIN32 */

#ifndef WIN32

#ifdef HAVE_LIBCAP
    /* Before dropping the privileges, retain capabilities to regain them in future. */
    caps = cap_get_proc();

    cap_set_flag(caps, CAP_PERMITTED, num_cap, cap_values, CAP_SET);
    cap_set_flag(caps, CAP_EFFECTIVE, num_cap, cap_values, CAP_SET);

    if((cap_set_proc(caps) != 0) || (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) != 0))
        traceEvent(TRACE_WARNING, "Unable to retain permitted capabilities [%s]\n", strerror(errno));
#else
#ifndef __APPLE__
    traceEvent(TRACE_WARNING, "n2n has not been compiled with libcap-dev. Some commands may fail.");
#endif
#endif /* HAVE_LIBCAP */

    if((eee->tuntap_priv_conf.userid != 0) || (eee->tuntap_priv_conf.groupid != 0)) {
        traceEvent(TRACE_NORMAL, "Dropping privileges to uid=%d, gid=%d",
                   (signed int)eee->tuntap_priv_conf.userid, (signed int)eee->tuntap_priv_conf.groupid);

        /* Finished with the need for root privileges. Drop to unprivileged user. */
        if((setgid(eee->tuntap_priv_conf.groupid) != 0)
           || (setuid(eee->tuntap_priv_conf.userid) != 0)) {
            traceEvent(TRACE_ERROR, "Unable to drop privileges [%u/%s]", errno, strerror(errno));
            exit(1);
        }
    }

    if((getuid() == 0) || (getgid() == 0))
        traceEvent(TRACE_WARNING, "Running as root is discouraged, check out the -u/-g options");
#endif

#ifdef __linux__
    signal(SIGTERM, term_handler);
    signal(SIGINT,  term_handler);
#endif
#ifdef WIN32
    SetConsoleCtrlHandler(term_handler, TRUE);
#endif

    keep_on_running = 1;
    traceEvent(TRACE_NORMAL, "edge started");
    rc = run_edge_loop(eee, &keep_on_running);
    print_edge_stats(eee);

#ifdef HAVE_LIBCAP
    /* Before completing the cleanup, regain the capabilities as some
     * cleanup tasks require them (e.g. routes cleanup). */
    cap_set_flag(caps, CAP_EFFECTIVE, num_cap, cap_values, CAP_SET);

    if(cap_set_proc(caps) != 0)
        traceEvent(TRACE_WARNING, "Could not regain the capabilities [%s]\n", strerror(errno));

    cap_free(caps);
#endif

    /* Cleanup */
    edge_term_conf(&eee->conf);
    tuntap_close(&eee->device);
    edge_term(eee);

#ifdef WIN32
    destroyWin32();
#endif

    return(rc);
}

/* ************************************** */