/* ifchd.c - interface change daemon
 *
 * Copyright (c) 2004-2012 Nicholas J. Kain <njkain at gmail dot com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 *
 * - 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT HOLDER OR CONTRIBUTORS 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.
 */

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/epoll.h>
#include <sys/signalfd.h>
#include <sys/stat.h>
#include <fcntl.h>

#include <time.h>
#include <pwd.h>
#include <grp.h>

#include <signal.h>
#include <errno.h>

#include <getopt.h>

#include "ifchd-defines.h"
#include "log.h"
#include "chroot.h"
#include "pidfile.h"
#include "signals.h"
#include "ifch_proto.h"
#include "strl.h"
#include "cap.h"
#include "io.h"
#include "linux.h"
#include "seccomp-bpf.h"

enum states {
    STATE_NOTHING,
    STATE_INTERFACE,
    STATE_IP,
    STATE_SUBNET,
    STATE_TIMEZONE,
    STATE_ROUTER,
    STATE_DNS,
    STATE_LPRSVR,
    STATE_HOSTNAME,
    STATE_DOMAIN,
    STATE_IPTTL,
    STATE_MTU,
    STATE_BROADCAST,
    STATE_NTPSVR,
    STATE_WINS
};

struct ifchd_client clients[SOCK_QUEUE];

static int epollfd, signalFd;
/* Extra two event slots are for signalFd and the listen socket. */
static struct epoll_event events[SOCK_QUEUE+2];

int resolv_conf_fd = -1;
/* int ntp_conf_fd = -1; */

/* If true, allow HOSTNAME changes from dhcp server. */
int allow_hostname = 0;

static uid_t peer_uid;
static gid_t peer_gid;
static pid_t peer_pid;

static int gflags_verbose = 0;

static void writeordie(int fd, const char *buf, int len)
{
    if (safe_write(fd, buf, len) == -1)
        suicide("write returned error");
}

static void epoll_add(int fd)
{
    struct epoll_event ev;
    int r;
    ev.events = EPOLLIN | EPOLLRDHUP | EPOLLERR | EPOLLHUP;
    ev.data.fd = fd;
    r = epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &ev);
    if (r == -1)
        suicide("epoll_add failed %s", strerror(errno));
}

static void epoll_del(int fd)
{
    struct epoll_event ev;
    int r;
    ev.events = EPOLLIN | EPOLLRDHUP | EPOLLERR | EPOLLHUP;
    ev.data.fd = fd;
    r = epoll_ctl(epollfd, EPOLL_CTL_DEL, fd, &ev);
    if (r == -1)
        suicide("epoll_del failed %s", strerror(errno));
}

static int enforce_seccomp(void)
{
    struct sock_filter filter[] = {
        VALIDATE_ARCHITECTURE,
        EXAMINE_SYSCALL,
        ALLOW_SYSCALL(read),
        ALLOW_SYSCALL(write),
        ALLOW_SYSCALL(sendto), // used for glibc syslog routines
        ALLOW_SYSCALL(epoll_wait),
        ALLOW_SYSCALL(epoll_ctl),
        ALLOW_SYSCALL(close),
        ALLOW_SYSCALL(socket),
        ALLOW_SYSCALL(getsockopt),
        ALLOW_SYSCALL(accept),
        ALLOW_SYSCALL(listen),
        ALLOW_SYSCALL(ioctl),
        ALLOW_SYSCALL(fsync),
        ALLOW_SYSCALL(lseek),
        ALLOW_SYSCALL(truncate),
        ALLOW_SYSCALL(fcntl),
        ALLOW_SYSCALL(unlink),
        ALLOW_SYSCALL(bind),
        ALLOW_SYSCALL(chmod),

        ALLOW_SYSCALL(rt_sigreturn),
#ifdef __NR_sigreturn
        ALLOW_SYSCALL(sigreturn),
#endif
        ALLOW_SYSCALL(exit_group),
        ALLOW_SYSCALL(exit),
        KILL_PROCESS,
    };
    struct sock_fprog prog = {
        .len = (unsigned short)(sizeof filter / sizeof filter[0]),
        .filter = filter,
    };
    if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0))
        return -1;
    if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog))
        return -1;
    return 0;
}

/* Writes a new resolv.conf based on the information we have received. */
static void write_resolve_conf(struct ifchd_client *cl)
{
    const static char ns_str[] = "nameserver ";
    const static char dom_str[] = "domain ";
    const static char srch_str[] = "search ";
    int r;
    off_t off;
    char buf[MAX_BUF];

    if (resolv_conf_fd == -1)
        return;
    if (strlen(cl->namesvrs) == 0)
        return;

    if (lseek(resolv_conf_fd, 0, SEEK_SET) == -1)
        return;

    char *p = cl->namesvrs;
    while (p && (*p != '\0')) {
        char *q = strchr(p, ' ');
        if (!q)
            q = strchr(p, '\0');
        else
            *q++ = '\0';
        strlcpy(buf, p, sizeof buf);

        writeordie(resolv_conf_fd, ns_str, strlen(ns_str));
        writeordie(resolv_conf_fd, buf, strlen(buf));
        writeordie(resolv_conf_fd, "\n", 1);

        p = q;
    }

    p = cl->domains;
    int numdoms = 0;
    while (p && (*p != '\0')) {
        char *q = strchr(p, ' ');
        if (!q)
            q = strchr(p, '\0');
        else
            *q++ = '\0';
        strlcpy(buf, p, sizeof buf);

        if (numdoms == 0) {
            writeordie(resolv_conf_fd, dom_str, strlen(dom_str));
            writeordie(resolv_conf_fd, buf, strlen(buf));
        } else {
            if (numdoms == 1) {
                writeordie(resolv_conf_fd, "\n", 1);
                writeordie(resolv_conf_fd, srch_str, strlen(srch_str));
                writeordie(resolv_conf_fd, buf, strlen(buf));
            } else {
                writeordie(resolv_conf_fd, " ", 1);
                writeordie(resolv_conf_fd, buf, strlen(buf));
            }
        }

        ++numdoms;
        p = q;
        if (numdoms > 6)
            break;
    }
    writeordie(resolv_conf_fd, "\n", 1);

    off = lseek(resolv_conf_fd, 0, SEEK_CUR);
    if (off == -1) {
        log_line("write_resolve_conf: lseek returned error: %s\n",
                strerror(errno));
        return;
    }
  retry:
    r = ftruncate(resolv_conf_fd, off);
    if (r == -1) {
        if (errno == EINTR)
            goto retry;
        log_line("write_resolve_conf: ftruncate returned error: %s\n",
                 strerror(errno));
        return;
    }
    r = fsync(resolv_conf_fd);
    if (r == -1) {
        log_line("write_resolve_conf: fsync returned error: %s\n",
                 strerror(errno));
        return;
    }
}

/* XXX: addme */
static void perform_timezone(struct ifchd_client *cl, char *str)
{}

/* Add a dns server to the /etc/resolv.conf -- we already have a fd. */
static void perform_dns(struct ifchd_client *cl, char *str)
{
    if (!str || resolv_conf_fd == -1)
        return;
    strlcpy(cl->namesvrs, str, MAX_BUF);
    write_resolve_conf(cl);
}

/* Updates for print daemons are too non-standard to be useful. */
static void perform_lprsvr(struct ifchd_client *cl, char *str)
{}

/* Sets machine hostname. */
static void perform_hostname(struct ifchd_client *cl, char *str)
{
    if (!allow_hostname || !str)
        return;
    if (sethostname(str, strlen(str) + 1) == -1)
        log_line("sethostname returned %s\n", strerror(errno));
}

/* update "domain" and "search" in /etc/resolv.conf */
static void perform_domain(struct ifchd_client *cl, char *str)
{
    if (!str || resolv_conf_fd == -1)
        return;
    strlcpy(cl->domains, str, MAX_BUF);
    write_resolve_conf(cl);
}

/* I don't think this can be done without a netfilter extension
 * that isn't in the mainline kernels. */
static void perform_ipttl(struct ifchd_client *cl, char *str)
{}

/* XXX: addme */
static void perform_ntpsrv(struct ifchd_client *cl, char *str)
{}

/* Maybe Samba cares about this feature?  I don't know. */
static void perform_wins(struct ifchd_client *cl, char *str)
{}

static void ifchd_client_init(struct ifchd_client *p)
{
    p->fd = -1;
    p->idle_time = time(NULL);
    p->state = STATE_NOTHING;

    memset(p->ibuf, 0, sizeof p->ibuf);
    memset(p->ifnam, 0, sizeof p->ifnam);
    memset(p->namesvrs, 0, sizeof p->namesvrs);
    memset(p->domains, 0, sizeof p->domains);
}

static void ifchd_client_wipe(struct ifchd_client *p)
{
    if (p->fd >= 0) {
        epoll_del(p->fd);
        close(p->fd);
    }
    ifchd_client_init(p);
}

static void ifchd_client_new(struct ifchd_client *p, int fd)
{
    ifchd_client_wipe(p);
    p->fd = fd;
    epoll_add(fd);
}

/* Conditionally accepts a new connection and initializes data structures. */
static void add_sk(int sk)
{
    int i;

    if (authorized_peer(sk, peer_pid, peer_uid, peer_gid)) {
        for (i = 0; i < SOCK_QUEUE; i++) {
            struct ifchd_client *p = &clients[i];
            if (p->fd == -1) {
                ifchd_client_new(p, sk);
                return;
            }
        }
    }
    close(sk);
}

/* Closes idle connections. */
static void close_idle_sk(void)
{
    int i;

    for (i=0; i<SOCK_QUEUE; i++) {
        struct ifchd_client *p = &clients[i];
        if (p->fd == -1)
            continue;
        if (time(NULL) - p->idle_time > CONN_TIMEOUT)
            ifchd_client_wipe(p);
    }
}

/*
 * Returns -1 on fatal error.
 */
static int execute_buffer(struct ifchd_client *cl, char *newbuf)
{
    char buf[MAX_BUF * 2];
    char *p = buf, *endp;

    memset(buf, 0, sizeof buf);
    strlcat(buf, cl->ibuf, sizeof buf);
    strlcat(buf, newbuf, sizeof buf);

    for (endp = p;;p = endp) {
        if (cl->state == STATE_NOTHING) {
            char *colon = strchr(p, ':');
            if (!colon)
                break;
            char *semi = strchr(p, ';');
            if (semi && semi < colon) {
                log_line("bad syntax: STATE_NOTHING and a ';' came before ':'");
                return -1;
            }
            *colon = '\0';
            endp = colon + 1;
        } else {
            char *semi = strchr(p, ';');
            if (!semi)
                break;
            char *colon = strchr(p, ':');
            if (colon && colon < semi) {
                log_line("bad syntax: !STATE_NOTHING and a ':' came before ';'");
                return -1;
            }
            *semi = '\0';
            endp = semi + 1;
        }

        if (!strlen(p))
            continue;

        switch (cl->state) {
            case STATE_NOTHING:
                if (strncmp(p, CMD_INTERFACE, sizeof(CMD_INTERFACE)) == 0)
                    cl->state = STATE_INTERFACE;
                if (strncmp(p, CMD_IP, sizeof(CMD_IP)) == 0)
                    cl->state = STATE_IP;
                if (strncmp(p, CMD_SUBNET, sizeof(CMD_SUBNET)) == 0)
                    cl->state = STATE_SUBNET;
                if (strncmp(p, CMD_TIMEZONE, sizeof(CMD_TIMEZONE)) == 0)
                    cl->state = STATE_TIMEZONE;
                if (strncmp(p, CMD_ROUTER, sizeof(CMD_ROUTER)) == 0)
                    cl->state = STATE_ROUTER;
                if (strncmp(p, CMD_DNS, sizeof(CMD_DNS)) == 0)
                    cl->state = STATE_DNS;
                if (strncmp(p, CMD_LPRSVR, sizeof(CMD_LPRSVR)) == 0)
                    cl->state = STATE_LPRSVR;
                if (strncmp(p, CMD_HOSTNAME, sizeof(CMD_HOSTNAME)) == 0)
                    cl->state = STATE_HOSTNAME;
                if (strncmp(p, CMD_DOMAIN, sizeof(CMD_DOMAIN)) == 0)
                    cl->state = STATE_DOMAIN;
                if (strncmp(p, CMD_IPTTL, sizeof(CMD_IPTTL)) == 0)
                    cl->state = STATE_IPTTL;
                if (strncmp(p, CMD_MTU, sizeof(CMD_MTU)) == 0)
                    cl->state = STATE_MTU;
                if (strncmp(p, CMD_BROADCAST, sizeof(CMD_BROADCAST)) == 0)
                    cl->state = STATE_BROADCAST;
                if (strncmp(p, CMD_NTPSVR, sizeof(CMD_NTPSVR)) == 0)
                    cl->state = STATE_NTPSVR;
                if (strncmp(p, CMD_WINS, sizeof(CMD_WINS)) == 0)
                    cl->state = STATE_WINS;
                break;

            case STATE_INTERFACE:
                perform_interface(cl, p);
                cl->state = STATE_NOTHING;
                break;

            case STATE_IP:
                perform_ip(cl, p);
                cl->state = STATE_NOTHING;
                break;

            case STATE_SUBNET:
                perform_subnet(cl, p);
                cl->state = STATE_NOTHING;
                break;

            case STATE_TIMEZONE:
                perform_timezone(cl, p);
                cl->state = STATE_NOTHING;
                break;

            case STATE_ROUTER:
                perform_router(cl, p);
                cl->state = STATE_NOTHING;
                break;

            case STATE_DNS:
                perform_dns(cl, p);
                cl->state = STATE_NOTHING;
                break;

            case STATE_LPRSVR:
                perform_lprsvr(cl, p);
                cl->state = STATE_NOTHING;
                break;

            case STATE_HOSTNAME:
                perform_hostname(cl, p);
                cl->state = STATE_NOTHING;
                break;

            case STATE_DOMAIN:
                perform_domain(cl, p);
                cl->state = STATE_NOTHING;
                break;

            case STATE_IPTTL:
                perform_ipttl(cl, p);
                cl->state = STATE_NOTHING;
                break;

            case STATE_MTU:
                perform_mtu(cl, p);
                cl->state = STATE_NOTHING;
                break;

            case STATE_BROADCAST:
                perform_broadcast(cl, p);
                cl->state = STATE_NOTHING;
                break;

            case STATE_NTPSVR:
                perform_ntpsrv(cl, p);
                cl->state = STATE_NOTHING;
                break;

            case STATE_WINS:
                perform_wins(cl, p);
                cl->state = STATE_NOTHING;
                break;

            default:
                log_line("warning: invalid state in dispatch_work\n");
                break;
        }
    }
    size_t remsize = strlen(endp);
    if (remsize > MAX_BUF - 1)
        return -1;
    strlcpy(cl->ibuf, endp, MAX_BUF);
    return 0;
}

/* Opens a non-blocking listening socket with the appropriate properties. */
static int get_listen(void)
{
    int lsock, ret;
    static const struct sockaddr_un lsock_addr =
    {
        .sun_family = AF_UNIX,
        .sun_path = "/var/state/ifchange"
    };

    lsock = socket(AF_UNIX, SOCK_STREAM, 0);
    if (lsock == -1)
        suicide("dispatch_work - failed to create socket");

    fcntl(lsock, F_SETFL, O_NONBLOCK);

    (void) unlink("/var/state/ifchange");
    ret = bind(lsock, (struct sockaddr *) &lsock_addr, sizeof(lsock_addr));
    if (ret)
        suicide("dispatch_work - failed to bind socket");
    ret = chmod("/var/state/ifchange", S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
    if (ret)
        suicide("dispatch_work - failed to chmod socket");
    ret = listen(lsock, SOCK_QUEUE);
    if (ret)
        suicide("dispatch_work - failed to listen on socket");

    return lsock;
}

static void accept_conns(int *lsock)
{
    int ret;
    struct sockaddr_un sock_addr;
    socklen_t sock_len = sizeof(sock_addr);

    for(;;)
    {
        ret = accept(*lsock, (struct sockaddr *) &sock_addr, &sock_len);
        if (ret != -1) {
            add_sk(ret);
            return;
        }
        switch (errno) {
            case EAGAIN:
#ifdef LINUX
            case ENETDOWN:
            case EPROTO:
            case ENOPROTOOPT:
            case EHOSTDOWN:
            case ENONET:
            case EHOSTUNREACH:
            case EOPNOTSUPP:
            case ENETUNREACH:
#endif
                return;

            case EINTR:
                continue;

            case EBADF:
            case ENOTSOCK:
            case EINVAL:
                log_line("warning: accept returned %s!\n", strerror(errno));

                epoll_del(*lsock);
                close(*lsock);

                *lsock = get_listen();
                epoll_add(*lsock);
                return;

            case ECONNABORTED:
            case EMFILE:
            case ENFILE:
                log_line("warning: accept returned %s!\n", strerror(errno));
                return;

            default:
                log_line("warning: accept returned a mysterious error: %s\n",
                        strerror(errno));
                return;
        }
    }
}

static void setup_signals()
{
    sigset_t mask;
    sigemptyset(&mask);
    sigaddset(&mask, SIGPIPE);
    sigaddset(&mask, SIGUSR1);
    sigaddset(&mask, SIGUSR2);
    sigaddset(&mask, SIGTSTP);
    sigaddset(&mask, SIGTTIN);
    sigaddset(&mask, SIGCHLD);
    sigaddset(&mask, SIGHUP);
    sigaddset(&mask, SIGINT);
    sigaddset(&mask, SIGTERM);
    if (sigprocmask(SIG_BLOCK, &mask, NULL) < 0)
        suicide("sigprocmask failed");
    signalFd = signalfd(-1, &mask, SFD_NONBLOCK);
    if (signalFd < 0)
        suicide("signalfd failed");
}

static void signal_dispatch()
{
    int t, off = 0;
    struct signalfd_siginfo si;
  again:
    t = read(signalFd, (char *)&si + off, sizeof si - off);
    if (t < sizeof si - off) {
        if (t < 0) {
            if (t == EAGAIN || t == EWOULDBLOCK || t == EINTR)
                goto again;
            else
                suicide("signalfd read error");
        }
        off += t;
    }
    switch (si.ssi_signo) {
        case SIGINT:
        case SIGTERM:
            exit(EXIT_SUCCESS);
        default:
            break;
    }
}

static void process_client_fd(int fd)
{
    struct ifchd_client *cl = NULL;
    int r;
    char buf[MAX_BUF];

    for (int j = 0; j < SOCK_QUEUE; ++j) {
        if (clients[j].fd == fd) {
            cl = &clients[j];
            break;
        }
    }
    if (!cl)
        suicide("epoll returned pending read for untracked fd");

    cl->idle_time = time(NULL);
    memset(buf, '\0', sizeof buf);

    r = safe_read(cl->fd, buf, sizeof buf - 1);
    if (r == 0) {
        // Remote end hung up.
        goto fail;
    } else if (r < 0) {
        if (errno == EAGAIN || errno == EWOULDBLOCK)
            return;
        log_line("error reading from client fd: %s", strerror(errno));
        goto fail;
    }

    if (execute_buffer(cl, buf) == -1) {
        log_line("execute_buffer was passed invalid commands");
        goto fail;
    }
    return;
  fail:
    ifchd_client_wipe(cl);
}

/* Core function that handles connections, gathers input, and calls
 * the state machine to do actual work. */
static void dispatch_work(void)
{
    int lsock;

    /* Initialize all structures to blank state. */
    for (int i = 0; i < SOCK_QUEUE; i++)
        ifchd_client_init(&clients[i]);

    lsock = get_listen();

    epoll_add(lsock);
    epoll_add(signalFd);

    for (;;) {
        int r = epoll_wait(epollfd, events, SOCK_QUEUE + 2, -1);
        if (r == -1) {
            if (errno == EINTR)
                continue;
            else
                suicide("epoll_wait failed");
        }
        for (int i = 0; i < r; ++i) {
            int fd = events[i].data.fd;
            if (fd == lsock)
                accept_conns(&lsock);
            else if (fd == signalFd)
                signal_dispatch();
            else
                process_client_fd(fd);
        }
        close_idle_sk();
    }
}

int main(int argc, char** argv) {
    int c, t;
    uid_t uid = 0;
    gid_t gid = 0;
    char pidfile[MAX_PATH_LENGTH] = PID_FILE_DEFAULT;
    char chrootd[MAX_PATH_LENGTH] = "";
    char resolv_conf_d[MAX_PATH_LENGTH] = "";
    char *p;
    struct passwd *pws;
    struct group *grp;

    while (1) {
        int option_index = 0;
        static const struct option long_options[] = {
            {"detach", 0, 0, 'd'},
            {"nodetach", 0, 0, 'n'},
            {"pidfile", 1, 0, 'p'},
            {"quiet", 0, 0, 'q'},
            {"chroot", 1, 0, 'c'},
            {"resolve", 1, 0, 'r'},
            {"hostname", 0, 0, 'o'},
            {"user", 1, 0, 'u'},
            {"group", 1, 0, 'g'},
            {"cuser", 1, 0, 'U'},
            {"cgroup", 1, 0, 'G'},
            {"cpid", 1, 0, 'P'},
            {"interface", 1, 0, 'i'},
            {"help", 0, 0, 'h'},
            {"version", 0, 0, 'v'},
            {"verbose", 0, 0, 'V'},
            {0, 0, 0, 0}
        };

        c = getopt_long(argc, argv, "dnp:qc:r:ou:g:U:G:P:i:hvV", long_options,
                        &option_index);
        if (c == -1)
            break;

        switch (c) {

            case 'h':
                printf(
"ifchd %s, if change daemon.  Licensed under 2-clause BSD.\n", IFCHD_VERSION);
                printf(
"Copyright (C) 2004-2012 Nicholas J. Kain\n"
"Usage: ifchd [OPTIONS]\n"
"  -d, --detach                detach from TTY and daemonize\n"
"  -n, --nodetach              stay attached to TTY\n"
"  -q, --quiet                 don't print to std(out|err) or log\n"
"  -c, --chroot                path where ifchd should chroot\n"
"  -r, --resolve               path to resolv.conf or equiv\n"
"  -o, --hostname              allow dhcp to set machine hostname\n"
"  -p, --pidfile               pidfile path\n");
                printf(
"  -u, --user                  user name that ifchd should run as\n"
"  -g, --group                 group name that ifchd should run as\n"
"  -U, --cuser                 user name of clients\n"
"  -G, --cgroup                group name of clients\n"
"  -P, --cpid                  process id of client\n"
"  -i, --interface             ifchd clients may modify this interface\n"
"  -V, --verbose               log detailed messages\n"
"  -h, --help                  print this help and exit\n"
"  -v, --version               print version information and exit\n");
                exit(EXIT_FAILURE);
                break;

            case 'v':
                printf(
"ifchd %s, if change daemon.  Licensed under 2-clause BSD.\n", IFCHD_VERSION);
                printf(
"Copyright (C) 2004-2012 Nicholas J. Kain\nAll rights reserved.\n"
"This is free software; see the source for copying conditions.  There is NO\n"
"WARRANTY; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n");
                exit(EXIT_FAILURE);
                break;

            case 'd':
                gflags_detach = 1;
                break;

            case 'n':
                gflags_detach = 0;
                break;

            case 'q':
                gflags_quiet = 1;
                break;

            case 'c':
                strlcpy(chrootd, optarg, MAX_PATH_LENGTH);
                break;

            case 'p':
                strlcpy(pidfile, optarg, MAX_PATH_LENGTH);
                break;

            case 'r':
                strlcpy(resolv_conf_d, optarg, MAX_PATH_LENGTH);
                break;

            case 'o':
                allow_hostname = 1;
                break;

            case 'u':
                t = (unsigned int) strtol(optarg, &p, 10);
                if (*p != '\0') {
                    pws = getpwnam(optarg);
                    if (pws) {
                        uid = (int)pws->pw_uid;
                        if (!gid)
                            gid = (int)pws->pw_gid;
                    } else suicide("FATAL - Invalid uid specified.");
                } else
                    uid = t;
                break;

            case 'g':
                t = (unsigned int) strtol(optarg, &p, 10);
                if (*p != '\0') {
                    grp = getgrnam(optarg);
                    if (grp) {
                        gid = (int)grp->gr_gid;
                    } else
                        suicide("FATAL - Invalid gid specified.");
                } else
                    gid = t;
                break;

            case 'U':
                t = (unsigned int) strtol(optarg, &p, 10);
                if (*p != '\0') {
                    pws = getpwnam(optarg);
                    if (pws) {
                        peer_uid = (int)pws->pw_uid;
                        if (!peer_gid)
                            peer_gid = (int)pws->pw_gid;
                    } else
                        suicide("FATAL - Invalid uid specified.");
                } else
                    peer_uid = t;
                break;

            case 'G':
                t = (unsigned int) strtol(optarg, &p, 10);
                if (*p != '\0') {
                    grp = getgrnam(optarg);
                    if (grp) {
                        peer_gid = (int)grp->gr_gid;
                    } else
                        suicide("FATAL - Invalid gid specified.");
                } else
                    peer_gid = t;
                break;

            case 'P':
                t = (unsigned int) strtol(optarg, &p, 10);
                if (*p == '\0')
                    peer_pid = t;
                break;

            case 'i':
                add_permitted_if(optarg);
                break;

            case 'V':
                gflags_verbose = 1;
                break;
        }
    }

    if (getuid())
        suicide("FATAL - I need root for CAP_NET_ADMIN and chroot!");

    if (gflags_detach)
        if (daemon(0,0)) {
            log_line("FATAL - detaching fork failed\n");
            exit(EXIT_FAILURE);
        }

    if (file_exists(pidfile, "w") == -1) {
        log_line("FATAL - cannot open pidfile for write!");
        exit(EXIT_FAILURE);
    }
    write_pid(pidfile);

    umask(077);
    setup_signals();

    /* If we are requested to update resolv.conf, preopen the fd before
     * we drop root privileges, making sure that if we create
     * resolv.conf, it will be world-readable.
     */
    if (strncmp(resolv_conf_d, "", MAX_PATH_LENGTH)) {
        umask(022);
        resolv_conf_fd = open(resolv_conf_d, O_RDWR | O_CREAT, 644);
        umask(077);
        if (resolv_conf_fd == -1) {
            suicide("FATAL - unable to open resolv.conf");
        }
    }

    if (!strncmp(chrootd, "", MAX_PATH_LENGTH))
        suicide("FATAL - No chroot path specified.  Refusing to run.");

    /* Note that failure cases are handled by called fns. */
    imprison(chrootd);
    set_cap(uid, gid, "cap_net_admin=ep");
    drop_root(uid, gid);

    /* Cover our tracks... */
    memset(chrootd, '\0', sizeof(chrootd));
    memset(resolv_conf_d, '\0', sizeof(resolv_conf_d));
    memset(pidfile, '\0', sizeof(pidfile));

    epollfd = epoll_create1(0);
    if (epollfd == -1)
        suicide("epoll_create1 failed");

    if (enforce_seccomp())
        log_line("seccomp filter cannot be installed");

    dispatch_work();

    /* Explicitly freed so memory debugger output has less static. */
    for (size_t i = 0; i < SOCK_QUEUE; ++i)
        ifchd_client_wipe(&clients[i]);

    exit(EXIT_SUCCESS);
}