/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2009-2010 The FreeBSD Foundation
 * Copyright (c) 2010-2011 Pawel Jakub Dawidek <pawel@dawidek.net>
 * All rights reserved.
 *
 * This software was developed by Pawel Jakub Dawidek under sponsorship from
 * the FreeBSD Foundation.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS 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 AUTHORS 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 <sys/param.h>
#include <sys/linker.h>
#include <sys/module.h>
#include <sys/stat.h>
#include <sys/wait.h>

#include <err.h>
#include <errno.h>
#include <libutil.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysexits.h>
#include <time.h>
#include <unistd.h>

#include <activemap.h>
#include <pjdlog.h>

#include "control.h"
#include "event.h"
#include "hast.h"
#include "hast_proto.h"
#include "hastd.h"
#include "hooks.h"
#include "subr.h"

/* Path to configuration file. */
const char *cfgpath = HAST_CONFIG;
/* Hastd configuration. */
static struct hastd_config *cfg;
/* Was SIGINT or SIGTERM signal received? */
bool sigexit_received = false;
/* Path to pidfile. */
static const char *pidfile;
/* Pidfile handle. */
struct pidfh *pfh;
/* Do we run in foreground? */
static bool foreground;

/* How often check for hooks running for too long. */
#define REPORT_INTERVAL 5

static void
usage(void)
{

        errx(EX_USAGE, "[-dFh] [-c config] [-P pidfile]");
}

static void
g_gate_load(void)
{

        if (modfind("g_gate") == -1) {
                /* Not present in kernel, try loading it. */
                if (kldload("geom_gate") == -1 || modfind("g_gate") == -1) {
                        if (errno != EEXIST) {
                                pjdlog_exit(EX_OSERR,
                                    "Unable to load geom_gate module");
                        }
                }
        }
}

void
descriptors_cleanup(struct hast_resource *res)
{
        struct hast_resource *tres, *tmres;
        struct hastd_listen *lst;

        TAILQ_FOREACH_SAFE(tres, &cfg->hc_resources, hr_next, tmres) {
                if (tres == res) {
                        PJDLOG_VERIFY(res->hr_role == HAST_ROLE_SECONDARY ||
                            (res->hr_remotein == NULL &&
                             res->hr_remoteout == NULL));
                        continue;
                }
                if (tres->hr_remotein != NULL)
                        proto_close(tres->hr_remotein);
                if (tres->hr_remoteout != NULL)
                        proto_close(tres->hr_remoteout);
                if (tres->hr_ctrl != NULL)
                        proto_close(tres->hr_ctrl);
                if (tres->hr_event != NULL)
                        proto_close(tres->hr_event);
                if (tres->hr_conn != NULL)
                        proto_close(tres->hr_conn);
                TAILQ_REMOVE(&cfg->hc_resources, tres, hr_next);
                free(tres);
        }
        if (cfg->hc_controlin != NULL)
                proto_close(cfg->hc_controlin);
        proto_close(cfg->hc_controlconn);
        while ((lst = TAILQ_FIRST(&cfg->hc_listen)) != NULL) {
                TAILQ_REMOVE(&cfg->hc_listen, lst, hl_next);
                if (lst->hl_conn != NULL)
                        proto_close(lst->hl_conn);
                free(lst);
        }
        (void)pidfile_close(pfh);
        hook_fini();
        pjdlog_fini();
}

static const char *
dtype2str(mode_t mode)
{

        if (S_ISBLK(mode))
                return ("block device");
        else if (S_ISCHR(mode))
                return ("character device");
        else if (S_ISDIR(mode))
                return ("directory");
        else if (S_ISFIFO(mode))
                return ("pipe or FIFO");
        else if (S_ISLNK(mode))
                return ("symbolic link");
        else if (S_ISREG(mode))
                return ("regular file");
        else if (S_ISSOCK(mode))
                return ("socket");
        else if (S_ISWHT(mode))
                return ("whiteout");
        else
                return ("unknown");
}

void
descriptors_assert(const struct hast_resource *res, int pjdlogmode)
{
        char msg[256];
        struct stat sb;
        long maxfd;
        bool isopen;
        mode_t mode;
        int fd;

        /*
         * At this point descriptor to syslog socket is closed, so if we want
         * to log assertion message, we have to first store it in 'msg' local
         * buffer and then open syslog socket and log it.
         */
        msg[0] = '\0';

        maxfd = sysconf(_SC_OPEN_MAX);
        if (maxfd == -1) {
                pjdlog_init(pjdlogmode);
                pjdlog_prefix_set("[%s] (%s) ", res->hr_name,
                    role2str(res->hr_role));
                pjdlog_errno(LOG_WARNING, "sysconf(_SC_OPEN_MAX) failed");
                pjdlog_fini();
                maxfd = 16384;
        }
        for (fd = 0; fd <= maxfd; fd++) {
                if (fstat(fd, &sb) == 0) {
                        isopen = true;
                        mode = sb.st_mode;
                } else if (errno == EBADF) {
                        isopen = false;
                        mode = 0;
                } else {
                        (void)snprintf(msg, sizeof(msg),
                            "Unable to fstat descriptor %d: %s", fd,
                            strerror(errno));
                        break;
                }
                if (fd == STDIN_FILENO || fd == STDOUT_FILENO ||
                    fd == STDERR_FILENO) {
                        if (!isopen) {
                                (void)snprintf(msg, sizeof(msg),
                                    "Descriptor %d (%s) is closed, but should be open.",
                                    fd, (fd == STDIN_FILENO ? "stdin" :
                                    (fd == STDOUT_FILENO ? "stdout" : "stderr")));
                                break;
                        }
                } else if (fd == proto_descriptor(res->hr_event)) {
                        if (!isopen) {
                                (void)snprintf(msg, sizeof(msg),
                                    "Descriptor %d (event) is closed, but should be open.",
                                    fd);
                                break;
                        }
                        if (!S_ISSOCK(mode)) {
                                (void)snprintf(msg, sizeof(msg),
                                    "Descriptor %d (event) is %s, but should be %s.",
                                    fd, dtype2str(mode), dtype2str(S_IFSOCK));
                                break;
                        }
                } else if (fd == proto_descriptor(res->hr_ctrl)) {
                        if (!isopen) {
                                (void)snprintf(msg, sizeof(msg),
                                    "Descriptor %d (ctrl) is closed, but should be open.",
                                    fd);
                                break;
                        }
                        if (!S_ISSOCK(mode)) {
                                (void)snprintf(msg, sizeof(msg),
                                    "Descriptor %d (ctrl) is %s, but should be %s.",
                                    fd, dtype2str(mode), dtype2str(S_IFSOCK));
                                break;
                        }
                } else if (res->hr_role == HAST_ROLE_PRIMARY &&
                    fd == proto_descriptor(res->hr_conn)) {
                        if (!isopen) {
                                (void)snprintf(msg, sizeof(msg),
                                    "Descriptor %d (conn) is closed, but should be open.",
                                    fd);
                                break;
                        }
                        if (!S_ISSOCK(mode)) {
                                (void)snprintf(msg, sizeof(msg),
                                    "Descriptor %d (conn) is %s, but should be %s.",
                                    fd, dtype2str(mode), dtype2str(S_IFSOCK));
                                break;
                        }
                } else if (res->hr_role == HAST_ROLE_SECONDARY &&
                    res->hr_conn != NULL &&
                    fd == proto_descriptor(res->hr_conn)) {
                        if (isopen) {
                                (void)snprintf(msg, sizeof(msg),
                                    "Descriptor %d (conn) is open, but should be closed.",
                                    fd);
                                break;
                        }
                } else if (res->hr_role == HAST_ROLE_SECONDARY &&
                    fd == proto_descriptor(res->hr_remotein)) {
                        if (!isopen) {
                                (void)snprintf(msg, sizeof(msg),
                                    "Descriptor %d (remote in) is closed, but should be open.",
                                    fd);
                                break;
                        }
                        if (!S_ISSOCK(mode)) {
                                (void)snprintf(msg, sizeof(msg),
                                    "Descriptor %d (remote in) is %s, but should be %s.",
                                    fd, dtype2str(mode), dtype2str(S_IFSOCK));
                                break;
                        }
                } else if (res->hr_role == HAST_ROLE_SECONDARY &&
                    fd == proto_descriptor(res->hr_remoteout)) {
                        if (!isopen) {
                                (void)snprintf(msg, sizeof(msg),
                                    "Descriptor %d (remote out) is closed, but should be open.",
                                    fd);
                                break;
                        }
                        if (!S_ISSOCK(mode)) {
                                (void)snprintf(msg, sizeof(msg),
                                    "Descriptor %d (remote out) is %s, but should be %s.",
                                    fd, dtype2str(mode), dtype2str(S_IFSOCK));
                                break;
                        }
                } else {
                        if (isopen) {
                                (void)snprintf(msg, sizeof(msg),
                                    "Descriptor %d is open (%s), but should be closed.",
                                    fd, dtype2str(mode));
                                break;
                        }
                }
        }
        if (msg[0] != '\0') {
                pjdlog_init(pjdlogmode);
                pjdlog_prefix_set("[%s] (%s) ", res->hr_name,
                    role2str(res->hr_role));
                PJDLOG_ABORT("%s", msg);
        }
}

static void
child_exit_log(unsigned int pid, int status)
{

        if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
                pjdlog_debug(1, "Worker process exited gracefully (pid=%u).",
                    pid);
        } else if (WIFSIGNALED(status)) {
                pjdlog_error("Worker process killed (pid=%u, signal=%d).",
                    pid, WTERMSIG(status));
        } else {
                pjdlog_error("Worker process exited ungracefully (pid=%u, exitcode=%d).",
                    pid, WIFEXITED(status) ? WEXITSTATUS(status) : -1);
        }
}

static void
child_exit(void)
{
        struct hast_resource *res;
        int status;
        pid_t pid;

        while ((pid = wait3(&status, WNOHANG, NULL)) > 0) {
                /* Find resource related to the process that just exited. */
                TAILQ_FOREACH(res, &cfg->hc_resources, hr_next) {
                        if (pid == res->hr_workerpid)
                                break;
                }
                if (res == NULL) {
                        /*
                         * This can happen when new connection arrives and we
                         * cancel child responsible for the old one or if this
                         * was hook which we executed.
                         */
                        hook_check_one(pid, status);
                        continue;
                }
                pjdlog_prefix_set("[%s] (%s) ", res->hr_name,
                    role2str(res->hr_role));
                child_exit_log(pid, status);
                child_cleanup(res);
                if (res->hr_role == HAST_ROLE_PRIMARY) {
                        /*
                         * Restart child process if it was killed by signal
                         * or exited because of temporary problem.
                         */
                        if (WIFSIGNALED(status) ||
                            (WIFEXITED(status) &&
                             WEXITSTATUS(status) == EX_TEMPFAIL)) {
                                sleep(1);
                                pjdlog_info("Restarting worker process.");
                                hastd_primary(res);
                        } else {
                                res->hr_role = HAST_ROLE_INIT;
                                pjdlog_info("Changing resource role back to %s.",
                                    role2str(res->hr_role));
                        }
                }
                pjdlog_prefix_set("%s", "");
        }
}

static bool
resource_needs_restart(const struct hast_resource *res0,
    const struct hast_resource *res1)
{

        PJDLOG_ASSERT(strcmp(res0->hr_name, res1->hr_name) == 0);

        if (strcmp(res0->hr_provname, res1->hr_provname) != 0)
                return (true);
        if (strcmp(res0->hr_localpath, res1->hr_localpath) != 0)
                return (true);
        if (res0->hr_role == HAST_ROLE_INIT ||
            res0->hr_role == HAST_ROLE_SECONDARY) {
                if (strcmp(res0->hr_remoteaddr, res1->hr_remoteaddr) != 0)
                        return (true);
                if (strcmp(res0->hr_sourceaddr, res1->hr_sourceaddr) != 0)
                        return (true);
                if (res0->hr_replication != res1->hr_replication)
                        return (true);
                if (res0->hr_checksum != res1->hr_checksum)
                        return (true);
                if (res0->hr_compression != res1->hr_compression)
                        return (true);
                if (res0->hr_timeout != res1->hr_timeout)
                        return (true);
                if (strcmp(res0->hr_exec, res1->hr_exec) != 0)
                        return (true);
                /*
                 * When metaflush has changed we don't really need restart,
                 * but it is just easier this way.
                 */
                if (res0->hr_metaflush != res1->hr_metaflush)
                        return (true);
        }
        return (false);
}

static bool
resource_needs_reload(const struct hast_resource *res0,
    const struct hast_resource *res1)
{

        PJDLOG_ASSERT(strcmp(res0->hr_name, res1->hr_name) == 0);
        PJDLOG_ASSERT(strcmp(res0->hr_provname, res1->hr_provname) == 0);
        PJDLOG_ASSERT(strcmp(res0->hr_localpath, res1->hr_localpath) == 0);

        if (res0->hr_role != HAST_ROLE_PRIMARY)
                return (false);

        if (strcmp(res0->hr_remoteaddr, res1->hr_remoteaddr) != 0)
                return (true);
        if (strcmp(res0->hr_sourceaddr, res1->hr_sourceaddr) != 0)
                return (true);
        if (res0->hr_replication != res1->hr_replication)
                return (true);
        if (res0->hr_checksum != res1->hr_checksum)
                return (true);
        if (res0->hr_compression != res1->hr_compression)
                return (true);
        if (res0->hr_timeout != res1->hr_timeout)
                return (true);
        if (strcmp(res0->hr_exec, res1->hr_exec) != 0)
                return (true);
        if (res0->hr_metaflush != res1->hr_metaflush)
                return (true);
        return (false);
}

static void
resource_reload(const struct hast_resource *res)
{
        struct nv *nvin, *nvout;
        int error;

        PJDLOG_ASSERT(res->hr_role == HAST_ROLE_PRIMARY);

        nvout = nv_alloc();
        nv_add_uint8(nvout, CONTROL_RELOAD, "cmd");
        nv_add_string(nvout, res->hr_remoteaddr, "remoteaddr");
        nv_add_string(nvout, res->hr_sourceaddr, "sourceaddr");
        nv_add_int32(nvout, (int32_t)res->hr_replication, "replication");
        nv_add_int32(nvout, (int32_t)res->hr_checksum, "checksum");
        nv_add_int32(nvout, (int32_t)res->hr_compression, "compression");
        nv_add_int32(nvout, (int32_t)res->hr_timeout, "timeout");
        nv_add_string(nvout, res->hr_exec, "exec");
        nv_add_int32(nvout, (int32_t)res->hr_metaflush, "metaflush");
        if (nv_error(nvout) != 0) {
                nv_free(nvout);
                pjdlog_error("Unable to allocate header for reload message.");
                return;
        }
        if (hast_proto_send(res, res->hr_ctrl, nvout, NULL, 0) == -1) {
                pjdlog_errno(LOG_ERR, "Unable to send reload message");
                nv_free(nvout);
                return;
        }
        nv_free(nvout);

        /* Receive response. */
        if (hast_proto_recv_hdr(res->hr_ctrl, &nvin) == -1) {
                pjdlog_errno(LOG_ERR, "Unable to receive reload reply");
                return;
        }
        error = nv_get_int16(nvin, "error");
        nv_free(nvin);
        if (error != 0) {
                pjdlog_common(LOG_ERR, 0, error, "Reload failed");
                return;
        }
}

static void
hastd_reload(void)
{
        struct hastd_config *newcfg;
        struct hast_resource *nres, *cres, *tres;
        struct hastd_listen *nlst, *clst;
        struct pidfh *newpfh;
        unsigned int nlisten;
        uint8_t role;
        pid_t otherpid;

        pjdlog_info("Reloading configuration...");

        newpfh = NULL;

        newcfg = yy_config_parse(cfgpath, false);
        if (newcfg == NULL)
                goto failed;

        /*
         * Check if control address has changed.
         */
        if (strcmp(cfg->hc_controladdr, newcfg->hc_controladdr) != 0) {
                if (proto_server(newcfg->hc_controladdr,
                    &newcfg->hc_controlconn) == -1) {
                        pjdlog_errno(LOG_ERR,
                            "Unable to listen on control address %s",
                            newcfg->hc_controladdr);
                        goto failed;
                }
        }
        /*
         * Check if any listen address has changed.
         */
        nlisten = 0;
        TAILQ_FOREACH(nlst, &newcfg->hc_listen, hl_next) {
                TAILQ_FOREACH(clst, &cfg->hc_listen, hl_next) {
                        if (strcmp(nlst->hl_addr, clst->hl_addr) == 0)
                                break;
                }
                if (clst != NULL && clst->hl_conn != NULL) {
                        pjdlog_info("Keep listening on address %s.",
                            nlst->hl_addr);
                        nlst->hl_conn = clst->hl_conn;
                        nlisten++;
                } else if (proto_server(nlst->hl_addr, &nlst->hl_conn) == 0) {
                        pjdlog_info("Listening on new address %s.",
                            nlst->hl_addr);
                        nlisten++;
                } else {
                        pjdlog_errno(LOG_WARNING,
                            "Unable to listen on address %s", nlst->hl_addr);
                }
        }
        if (nlisten == 0) {
                pjdlog_error("No addresses to listen on.");
                goto failed;
        }
        /*
         * Check if pidfile's path has changed.
         */
        if (!foreground && pidfile == NULL &&
            strcmp(cfg->hc_pidfile, newcfg->hc_pidfile) != 0) {
                newpfh = pidfile_open(newcfg->hc_pidfile, 0600, &otherpid);
                if (newpfh == NULL) {
                        if (errno == EEXIST) {
                                pjdlog_errno(LOG_WARNING,
                                    "Another hastd is already running, pidfile: %s, pid: %jd.",
                                    newcfg->hc_pidfile, (intmax_t)otherpid);
                        } else {
                                pjdlog_errno(LOG_WARNING,
                                    "Unable to open or create pidfile %s",
                                    newcfg->hc_pidfile);
                        }
                } else if (pidfile_write(newpfh) == -1) {
                        /* Write PID to a file. */
                        pjdlog_errno(LOG_WARNING,
                            "Unable to write PID to file %s",
                            newcfg->hc_pidfile);
                } else {
                        pjdlog_debug(1, "PID stored in %s.",
                            newcfg->hc_pidfile);
                }
        }

        /* No failures from now on. */

        /*
         * Switch to new control socket.
         */
        if (newcfg->hc_controlconn != NULL) {
                pjdlog_info("Control socket changed from %s to %s.",
                    cfg->hc_controladdr, newcfg->hc_controladdr);
                proto_close(cfg->hc_controlconn);
                cfg->hc_controlconn = newcfg->hc_controlconn;
                newcfg->hc_controlconn = NULL;
                strlcpy(cfg->hc_controladdr, newcfg->hc_controladdr,
                    sizeof(cfg->hc_controladdr));
        }
        /*
         * Switch to new pidfile.
         */
        if (newpfh != NULL) {
                pjdlog_info("Pidfile changed from %s to %s.", cfg->hc_pidfile,
                    newcfg->hc_pidfile);
                (void)pidfile_remove(pfh);
                pfh = newpfh;
                (void)strlcpy(cfg->hc_pidfile, newcfg->hc_pidfile,
                    sizeof(cfg->hc_pidfile));
        }
        /*
         * Switch to new listen addresses. Close all that were removed.
         */
        while ((clst = TAILQ_FIRST(&cfg->hc_listen)) != NULL) {
                TAILQ_FOREACH(nlst, &newcfg->hc_listen, hl_next) {
                        if (strcmp(nlst->hl_addr, clst->hl_addr) == 0)
                                break;
                }
                if (nlst == NULL && clst->hl_conn != NULL) {
                        proto_close(clst->hl_conn);
                        pjdlog_info("No longer listening on address %s.",
                            clst->hl_addr);
                }
                TAILQ_REMOVE(&cfg->hc_listen, clst, hl_next);
                free(clst);
        }
        TAILQ_CONCAT(&cfg->hc_listen, &newcfg->hc_listen, hl_next);

        /*
         * Stop and remove resources that were removed from the configuration.
         */
        TAILQ_FOREACH_SAFE(cres, &cfg->hc_resources, hr_next, tres) {
                TAILQ_FOREACH(nres, &newcfg->hc_resources, hr_next) {
                        if (strcmp(cres->hr_name, nres->hr_name) == 0)
                                break;
                }
                if (nres == NULL) {
                        control_set_role(cres, HAST_ROLE_INIT);
                        TAILQ_REMOVE(&cfg->hc_resources, cres, hr_next);
                        pjdlog_info("Resource %s removed.", cres->hr_name);
                        free(cres);
                }
        }
        /*
         * Move new resources to the current configuration.
         */
        TAILQ_FOREACH_SAFE(nres, &newcfg->hc_resources, hr_next, tres) {
                TAILQ_FOREACH(cres, &cfg->hc_resources, hr_next) {
                        if (strcmp(cres->hr_name, nres->hr_name) == 0)
                                break;
                }
                if (cres == NULL) {
                        TAILQ_REMOVE(&newcfg->hc_resources, nres, hr_next);
                        TAILQ_INSERT_TAIL(&cfg->hc_resources, nres, hr_next);
                        pjdlog_info("Resource %s added.", nres->hr_name);
                }
        }
        /*
         * Deal with modified resources.
         * Depending on what has changed exactly we might want to perform
         * different actions.
         *
         * We do full resource restart in the following situations:
         * Resource role is INIT or SECONDARY.
         * Resource role is PRIMARY and path to local component or provider
         * name has changed.
         * In case of PRIMARY, the worker process will be killed and restarted,
         * which also means removing /dev/hast/<name> provider and
         * recreating it.
         *
         * We do just reload (send SIGHUP to worker process) if we act as
         * PRIMARY, but only if remote address, source address, replication
         * mode, timeout, execution path or metaflush has changed.
         * For those, there is no need to restart worker process.
         * If PRIMARY receives SIGHUP, it will reconnect if remote address or
         * source address has changed or it will set new timeout if only timeout
         * has changed or it will update metaflush if only metaflush has
         * changed.
         */
        TAILQ_FOREACH_SAFE(nres, &newcfg->hc_resources, hr_next, tres) {
                TAILQ_FOREACH(cres, &cfg->hc_resources, hr_next) {
                        if (strcmp(cres->hr_name, nres->hr_name) == 0)
                                break;
                }
                PJDLOG_ASSERT(cres != NULL);
                if (resource_needs_restart(cres, nres)) {
                        pjdlog_info("Resource %s configuration was modified, restarting it.",
                            cres->hr_name);
                        role = cres->hr_role;
                        control_set_role(cres, HAST_ROLE_INIT);
                        TAILQ_REMOVE(&cfg->hc_resources, cres, hr_next);
                        free(cres);
                        TAILQ_REMOVE(&newcfg->hc_resources, nres, hr_next);
                        TAILQ_INSERT_TAIL(&cfg->hc_resources, nres, hr_next);
                        control_set_role(nres, role);
                } else if (resource_needs_reload(cres, nres)) {
                        pjdlog_info("Resource %s configuration was modified, reloading it.",
                            cres->hr_name);
                        strlcpy(cres->hr_remoteaddr, nres->hr_remoteaddr,
                            sizeof(cres->hr_remoteaddr));
                        strlcpy(cres->hr_sourceaddr, nres->hr_sourceaddr,
                            sizeof(cres->hr_sourceaddr));
                        cres->hr_replication = nres->hr_replication;
                        cres->hr_checksum = nres->hr_checksum;
                        cres->hr_compression = nres->hr_compression;
                        cres->hr_timeout = nres->hr_timeout;
                        strlcpy(cres->hr_exec, nres->hr_exec,
                            sizeof(cres->hr_exec));
                        cres->hr_metaflush = nres->hr_metaflush;
                        if (cres->hr_workerpid != 0)
                                resource_reload(cres);
                }
        }

        yy_config_free(newcfg);
        pjdlog_info("Configuration reloaded successfully.");
        return;
failed:
        if (newcfg != NULL) {
                if (newcfg->hc_controlconn != NULL)
                        proto_close(newcfg->hc_controlconn);
                while ((nlst = TAILQ_FIRST(&newcfg->hc_listen)) != NULL) {
                        if (nlst->hl_conn != NULL) {
                                TAILQ_FOREACH(clst, &cfg->hc_listen, hl_next) {
                                        if (strcmp(nlst->hl_addr,
                                            clst->hl_addr) == 0) {
                                                break;
                                        }
                                }
                                if (clst == NULL || clst->hl_conn == NULL)
                                        proto_close(nlst->hl_conn);
                        }
                        TAILQ_REMOVE(&newcfg->hc_listen, nlst, hl_next);
                        free(nlst);
                }
                yy_config_free(newcfg);
        }
        if (newpfh != NULL)
                (void)pidfile_remove(newpfh);
        pjdlog_warning("Configuration not reloaded.");
}

static void
terminate_workers(void)
{
        struct hast_resource *res;

        pjdlog_info("Termination signal received, exiting.");
        TAILQ_FOREACH(res, &cfg->hc_resources, hr_next) {
                if (res->hr_workerpid == 0)
                        continue;
                pjdlog_info("Terminating worker process (resource=%s, role=%s, pid=%u).",
                    res->hr_name, role2str(res->hr_role), res->hr_workerpid);
                if (kill(res->hr_workerpid, SIGTERM) == 0)
                        continue;
                pjdlog_errno(LOG_WARNING,
                    "Unable to send signal to worker process (resource=%s, role=%s, pid=%u).",
                    res->hr_name, role2str(res->hr_role), res->hr_workerpid);
        }
}

static void
listen_accept(struct hastd_listen *lst)
{
        struct hast_resource *res;
        struct proto_conn *conn;
        struct nv *nvin, *nvout, *nverr;
        const char *resname;
        const unsigned char *token;
        char laddr[256], raddr[256];
        uint8_t version;
        size_t size;
        pid_t pid;
        int status;

        proto_local_address(lst->hl_conn, laddr, sizeof(laddr));
        pjdlog_debug(1, "Accepting connection to %s.", laddr);

        if (proto_accept(lst->hl_conn, &conn) == -1) {
                pjdlog_errno(LOG_ERR, "Unable to accept connection %s", laddr);
                return;
        }

        proto_local_address(conn, laddr, sizeof(laddr));
        proto_remote_address(conn, raddr, sizeof(raddr));
        pjdlog_info("Connection from %s to %s.", raddr, laddr);

        /* Error in setting timeout is not critical, but why should it fail? */
        if (proto_timeout(conn, HAST_TIMEOUT) == -1)
                pjdlog_errno(LOG_WARNING, "Unable to set connection timeout");

        nvin = nvout = nverr = NULL;

        /*
         * Before receiving any data see if remote host have access to any
         * resource.
         */
        TAILQ_FOREACH(res, &cfg->hc_resources, hr_next) {
                if (proto_address_match(conn, res->hr_remoteaddr))
                        break;
        }
        if (res == NULL) {
                pjdlog_error("Client %s isn't known.", raddr);
                goto close;
        }
        /* Ok, remote host can access at least one resource. */

        if (hast_proto_recv_hdr(conn, &nvin) == -1) {
                pjdlog_errno(LOG_ERR, "Unable to receive header from %s",
                    raddr);
                goto close;
        }

        resname = nv_get_string(nvin, "resource");
        if (resname == NULL) {
                pjdlog_error("No 'resource' field in the header received from %s.",
                    raddr);
                goto close;
        }
        pjdlog_debug(2, "%s: resource=%s", raddr, resname);
        version = nv_get_uint8(nvin, "version");
        pjdlog_debug(2, "%s: version=%hhu", raddr, version);
        if (version == 0) {
                /*
                 * If no version is sent, it means this is protocol version 1.
                 */
                version = 1;
        }
        token = nv_get_uint8_array(nvin, &size, "token");
        /*
         * NULL token means that this is first connection.
         */
        if (token != NULL && size != sizeof(res->hr_token)) {
                pjdlog_error("Received token of invalid size from %s (expected %zu, got %zu).",
                    raddr, sizeof(res->hr_token), size);
                goto close;
        }

        /*
         * From now on we want to send errors to the remote node.
         */
        nverr = nv_alloc();

        /* Find resource related to this connection. */
        TAILQ_FOREACH(res, &cfg->hc_resources, hr_next) {
                if (strcmp(resname, res->hr_name) == 0)
                        break;
        }
        /* Have we found the resource? */
        if (res == NULL) {
                pjdlog_error("No resource '%s' as requested by %s.",
                    resname, raddr);
                nv_add_stringf(nverr, "errmsg", "Resource not configured.");
                goto fail;
        }

        /* Now that we know resource name setup log prefix. */
        pjdlog_prefix_set("[%s] (%s) ", res->hr_name, role2str(res->hr_role));

        /* Does the remote host have access to this resource? */
        if (!proto_address_match(conn, res->hr_remoteaddr)) {
                pjdlog_error("Client %s has no access to the resource.", raddr);
                nv_add_stringf(nverr, "errmsg", "No access to the resource.");
                goto fail;
        }
        /* Is the resource marked as secondary? */
        if (res->hr_role != HAST_ROLE_SECONDARY) {
                pjdlog_warning("We act as %s for the resource and not as %s as requested by %s.",
                    role2str(res->hr_role), role2str(HAST_ROLE_SECONDARY),
                    raddr);
                nv_add_stringf(nverr, "errmsg",
                    "Remote node acts as %s for the resource and not as %s.",
                    role2str(res->hr_role), role2str(HAST_ROLE_SECONDARY));
                if (res->hr_role == HAST_ROLE_PRIMARY) {
                        /*
                         * If we act as primary request the other side to wait
                         * for us a bit, as we might be finishing cleanups.
                         */
                        nv_add_uint8(nverr, 1, "wait");
                }
                goto fail;
        }
        /* Does token (if exists) match? */
        if (token != NULL && memcmp(token, res->hr_token,
            sizeof(res->hr_token)) != 0) {
                pjdlog_error("Token received from %s doesn't match.", raddr);
                nv_add_stringf(nverr, "errmsg", "Token doesn't match.");
                goto fail;
        }
        /*
         * If there is no token, but we have half-open connection
         * (only remotein) or full connection (worker process is running)
         * we have to cancel those and accept the new connection.
         */
        if (token == NULL) {
                PJDLOG_ASSERT(res->hr_remoteout == NULL);
                pjdlog_debug(1, "Initial connection from %s.", raddr);
                if (res->hr_workerpid != 0) {
                        PJDLOG_ASSERT(res->hr_remotein == NULL);
                        pjdlog_debug(1,
                            "Worker process exists (pid=%u), stopping it.",
                            (unsigned int)res->hr_workerpid);
                        /* Stop child process. */
                        if (kill(res->hr_workerpid, SIGINT) == -1) {
                                pjdlog_errno(LOG_ERR,
                                    "Unable to stop worker process (pid=%u)",
                                    (unsigned int)res->hr_workerpid);
                                /*
                                 * Other than logging the problem we
                                 * ignore it - nothing smart to do.
                                 */
                        }
                        /* Wait for it to exit. */
                        else if ((pid = waitpid(res->hr_workerpid,
                            &status, 0)) != res->hr_workerpid) {
                                /* We can only log the problem. */
                                pjdlog_errno(LOG_ERR,
                                    "Waiting for worker process (pid=%u) failed",
                                    (unsigned int)res->hr_workerpid);
                        } else {
                                child_exit_log(res->hr_workerpid, status);
                        }
                        child_cleanup(res);
                } else if (res->hr_remotein != NULL) {
                        char oaddr[256];

                        proto_remote_address(res->hr_remotein, oaddr,
                            sizeof(oaddr));
                        pjdlog_debug(1,
                            "Canceling half-open connection from %s on connection from %s.",
                            oaddr, raddr);
                        proto_close(res->hr_remotein);
                        res->hr_remotein = NULL;
                }
        }

        /*
         * Checks and cleanups are done.
         */

        if (token == NULL) {
                if (version > HAST_PROTO_VERSION) {
                        pjdlog_info("Remote protocol version %hhu is not supported, falling back to version %hhu.",
                            version, (unsigned char)HAST_PROTO_VERSION);
                        version = HAST_PROTO_VERSION;
                }
                pjdlog_debug(1, "Negotiated protocol version %hhu.", version);
                res->hr_version = version;
                arc4random_buf(res->hr_token, sizeof(res->hr_token));
                nvout = nv_alloc();
                nv_add_uint8(nvout, version, "version");
                nv_add_uint8_array(nvout, res->hr_token,
                    sizeof(res->hr_token), "token");
                if (nv_error(nvout) != 0) {
                        pjdlog_common(LOG_ERR, 0, nv_error(nvout),
                            "Unable to prepare return header for %s", raddr);
                        nv_add_stringf(nverr, "errmsg",
                            "Remote node was unable to prepare return header: %s.",
                            strerror(nv_error(nvout)));
                        goto fail;
                }
                if (hast_proto_send(res, conn, nvout, NULL, 0) == -1) {
                        int error = errno;

                        pjdlog_errno(LOG_ERR, "Unable to send response to %s",
                            raddr);
                        nv_add_stringf(nverr, "errmsg",
                            "Remote node was unable to send response: %s.",
                            strerror(error));
                        goto fail;
                }
                res->hr_remotein = conn;
                pjdlog_debug(1, "Incoming connection from %s configured.",
                    raddr);
        } else {
                res->hr_remoteout = conn;
                pjdlog_debug(1, "Outgoing connection to %s configured.", raddr);
                hastd_secondary(res, nvin);
        }
        nv_free(nvin);
        nv_free(nvout);
        nv_free(nverr);
        pjdlog_prefix_set("%s", "");
        return;
fail:
        if (nv_error(nverr) != 0) {
                pjdlog_common(LOG_ERR, 0, nv_error(nverr),
                    "Unable to prepare error header for %s", raddr);
                goto close;
        }
        if (hast_proto_send(NULL, conn, nverr, NULL, 0) == -1) {
                pjdlog_errno(LOG_ERR, "Unable to send error to %s", raddr);
                goto close;
        }
close:
        if (nvin != NULL)
                nv_free(nvin);
        if (nvout != NULL)
                nv_free(nvout);
        if (nverr != NULL)
                nv_free(nverr);
        proto_close(conn);
        pjdlog_prefix_set("%s", "");
}

static void
connection_migrate(struct hast_resource *res)
{
        struct proto_conn *conn;
        int16_t val = 0;

        pjdlog_prefix_set("[%s] (%s) ", res->hr_name, role2str(res->hr_role));

        PJDLOG_ASSERT(res->hr_role == HAST_ROLE_PRIMARY);

        if (proto_recv(res->hr_conn, &val, sizeof(val)) == -1) {
                pjdlog_errno(LOG_WARNING,
                    "Unable to receive connection command");
                return;
        }
        if (proto_client(res->hr_sourceaddr[0] != '\0' ? res->hr_sourceaddr : NULL,
            res->hr_remoteaddr, &conn) == -1) {
                val = errno;
                pjdlog_errno(LOG_WARNING,
                    "Unable to create outgoing connection to %s",
                    res->hr_remoteaddr);
                goto out;
        }
        if (proto_connect(conn, -1) == -1) {
                val = errno;
                pjdlog_errno(LOG_WARNING, "Unable to connect to %s",
                    res->hr_remoteaddr);
                proto_close(conn);
                goto out;
        }
        val = 0;
out:
        if (proto_send(res->hr_conn, &val, sizeof(val)) == -1) {
                pjdlog_errno(LOG_WARNING,
                    "Unable to send reply to connection request");
        }
        if (val == 0 && proto_connection_send(res->hr_conn, conn) == -1)
                pjdlog_errno(LOG_WARNING, "Unable to send connection");

        pjdlog_prefix_set("%s", "");
}

static void
check_signals(void)
{
        struct timespec sigtimeout;
        sigset_t mask;
        int signo;

        sigtimeout.tv_sec = 0;
        sigtimeout.tv_nsec = 0;

        PJDLOG_VERIFY(sigemptyset(&mask) == 0);
        PJDLOG_VERIFY(sigaddset(&mask, SIGHUP) == 0);
        PJDLOG_VERIFY(sigaddset(&mask, SIGINT) == 0);
        PJDLOG_VERIFY(sigaddset(&mask, SIGTERM) == 0);
        PJDLOG_VERIFY(sigaddset(&mask, SIGCHLD) == 0);

        while ((signo = sigtimedwait(&mask, NULL, &sigtimeout)) != -1) {
                switch (signo) {
                case SIGINT:
                case SIGTERM:
                        sigexit_received = true;
                        terminate_workers();
                        proto_close(cfg->hc_controlconn);
                        exit(EX_OK);
                        break;
                case SIGCHLD:
                        child_exit();
                        break;
                case SIGHUP:
                        hastd_reload();
                        break;
                default:
                        PJDLOG_ABORT("Unexpected signal (%d).", signo);
                }
        }
}

static void
main_loop(void)
{
        struct hast_resource *res;
        struct hastd_listen *lst;
        struct timeval seltimeout;
        int fd, maxfd, ret;
        time_t lastcheck, now;
        fd_set rfds;

        lastcheck = time(NULL);
        seltimeout.tv_sec = REPORT_INTERVAL;
        seltimeout.tv_usec = 0;

        for (;;) {
                check_signals();

                /* Setup descriptors for select(2). */
                FD_ZERO(&rfds);
                maxfd = fd = proto_descriptor(cfg->hc_controlconn);
                PJDLOG_ASSERT(fd >= 0);
                FD_SET(fd, &rfds);
                TAILQ_FOREACH(lst, &cfg->hc_listen, hl_next) {
                        if (lst->hl_conn == NULL)
                                continue;
                        fd = proto_descriptor(lst->hl_conn);
                        PJDLOG_ASSERT(fd >= 0);
                        FD_SET(fd, &rfds);
                        maxfd = MAX(fd, maxfd);
                }
                TAILQ_FOREACH(res, &cfg->hc_resources, hr_next) {
                        if (res->hr_event == NULL)
                                continue;
                        fd = proto_descriptor(res->hr_event);
                        PJDLOG_ASSERT(fd >= 0);
                        FD_SET(fd, &rfds);
                        maxfd = MAX(fd, maxfd);
                        if (res->hr_role == HAST_ROLE_PRIMARY) {
                                /* Only primary workers asks for connections. */
                                PJDLOG_ASSERT(res->hr_conn != NULL);
                                fd = proto_descriptor(res->hr_conn);
                                PJDLOG_ASSERT(fd >= 0);
                                FD_SET(fd, &rfds);
                                maxfd = MAX(fd, maxfd);
                        } else {
                                PJDLOG_ASSERT(res->hr_conn == NULL);
                        }
                }

                PJDLOG_ASSERT(maxfd + 1 <= (int)FD_SETSIZE);
                ret = select(maxfd + 1, &rfds, NULL, NULL, &seltimeout);
                now = time(NULL);
                if (lastcheck + REPORT_INTERVAL <= now) {
                        hook_check();
                        lastcheck = now;
                }
                if (ret == 0) {
                        /*
                         * select(2) timed out, so there should be no
                         * descriptors to check.
                         */
                        continue;
                } else if (ret == -1) {
                        if (errno == EINTR)
                                continue;
                        KEEP_ERRNO((void)pidfile_remove(pfh));
                        pjdlog_exit(EX_OSERR, "select() failed");
                }

                /*
                 * Check for signals before we do anything to update our
                 * info about terminated workers in the meantime.
                 */
                check_signals();

                if (FD_ISSET(proto_descriptor(cfg->hc_controlconn), &rfds))
                        control_handle(cfg);
                TAILQ_FOREACH(lst, &cfg->hc_listen, hl_next) {
                        if (lst->hl_conn == NULL)
                                continue;
                        if (FD_ISSET(proto_descriptor(lst->hl_conn), &rfds))
                                listen_accept(lst);
                }
                TAILQ_FOREACH(res, &cfg->hc_resources, hr_next) {
                        if (res->hr_event == NULL)
                                continue;
                        if (FD_ISSET(proto_descriptor(res->hr_event), &rfds)) {
                                if (event_recv(res) == 0)
                                        continue;
                                /* The worker process exited? */
                                proto_close(res->hr_event);
                                res->hr_event = NULL;
                                if (res->hr_conn != NULL) {
                                        proto_close(res->hr_conn);
                                        res->hr_conn = NULL;
                                }
                                continue;
                        }
                        if (res->hr_role == HAST_ROLE_PRIMARY) {
                                PJDLOG_ASSERT(res->hr_conn != NULL);
                                if (FD_ISSET(proto_descriptor(res->hr_conn),
                                    &rfds)) {
                                        connection_migrate(res);
                                }
                        } else {
                                PJDLOG_ASSERT(res->hr_conn == NULL);
                        }
                }
        }
}

static void
dummy_sighandler(int sig __unused)
{
        /* Nothing to do. */
}

int
main(int argc, char *argv[])
{
        struct hastd_listen *lst;
        pid_t otherpid;
        int debuglevel;
        sigset_t mask;

        foreground = false;
        debuglevel = 0;

        for (;;) {
                int ch;

                ch = getopt(argc, argv, "c:dFhP:");
                if (ch == -1)
                        break;
                switch (ch) {
                case 'c':
                        cfgpath = optarg;
                        break;
                case 'd':
                        debuglevel++;
                        break;
                case 'F':
                        foreground = true;
                        break;
                case 'P':
                        pidfile = optarg;
                        break;
                case 'h':
                default:
                        usage();
                }
        }
        argc -= optind;
        argv += optind;

        pjdlog_init(PJDLOG_MODE_STD);
        pjdlog_debug_set(debuglevel);

        closefrom(MAX(MAX(STDIN_FILENO, STDOUT_FILENO), STDERR_FILENO) + 1);
        g_gate_load();

        /*
         * When path to the configuration file is relative, obtain full path,
         * so we can always find the file, even after daemonizing and changing
         * working directory to /.
         */
        if (cfgpath[0] != '/') {
                const char *newcfgpath;

                newcfgpath = realpath(cfgpath, NULL);
                if (newcfgpath == NULL) {
                        pjdlog_exit(EX_CONFIG,
                            "Unable to obtain full path of %s", cfgpath);
                }
                cfgpath = newcfgpath;
        }

        cfg = yy_config_parse(cfgpath, true);
        PJDLOG_ASSERT(cfg != NULL);

        if (pidfile != NULL) {
                if (strlcpy(cfg->hc_pidfile, pidfile,
                    sizeof(cfg->hc_pidfile)) >= sizeof(cfg->hc_pidfile)) {
                        pjdlog_exitx(EX_CONFIG, "Pidfile path is too long.");
                }
        }

        if (pidfile != NULL || !foreground) {
                pfh = pidfile_open(cfg->hc_pidfile, 0600, &otherpid);
                if (pfh == NULL) {
                        if (errno == EEXIST) {
                                pjdlog_exitx(EX_TEMPFAIL,
                                    "Another hastd is already running, pidfile: %s, pid: %jd.",
                                    cfg->hc_pidfile, (intmax_t)otherpid);
                        }
                        /*
                         * If we cannot create pidfile for other reasons,
                         * only warn.
                         */
                        pjdlog_errno(LOG_WARNING,
                            "Unable to open or create pidfile %s",
                            cfg->hc_pidfile);
                }
        }

        /*
         * Restore default actions for interesting signals in case parent
         * process (like init(8)) decided to ignore some of them (like SIGHUP).
         */
        PJDLOG_VERIFY(signal(SIGHUP, SIG_DFL) != SIG_ERR);
        PJDLOG_VERIFY(signal(SIGINT, SIG_DFL) != SIG_ERR);
        PJDLOG_VERIFY(signal(SIGTERM, SIG_DFL) != SIG_ERR);
        /*
         * Because SIGCHLD is ignored by default, setup dummy handler for it,
         * so we can mask it.
         */
        PJDLOG_VERIFY(signal(SIGCHLD, dummy_sighandler) != SIG_ERR);

        PJDLOG_VERIFY(sigemptyset(&mask) == 0);
        PJDLOG_VERIFY(sigaddset(&mask, SIGHUP) == 0);
        PJDLOG_VERIFY(sigaddset(&mask, SIGINT) == 0);
        PJDLOG_VERIFY(sigaddset(&mask, SIGTERM) == 0);
        PJDLOG_VERIFY(sigaddset(&mask, SIGCHLD) == 0);
        PJDLOG_VERIFY(sigprocmask(SIG_SETMASK, &mask, NULL) == 0);

        /* Listen on control address. */
        if (proto_server(cfg->hc_controladdr, &cfg->hc_controlconn) == -1) {
                KEEP_ERRNO((void)pidfile_remove(pfh));
                pjdlog_exit(EX_OSERR, "Unable to listen on control address %s",
                    cfg->hc_controladdr);
        }
        /* Listen for remote connections. */
        TAILQ_FOREACH(lst, &cfg->hc_listen, hl_next) {
                if (proto_server(lst->hl_addr, &lst->hl_conn) == -1) {
                        KEEP_ERRNO((void)pidfile_remove(pfh));
                        pjdlog_exit(EX_OSERR, "Unable to listen on address %s",
                            lst->hl_addr);
                }
        }

        if (!foreground) {
                if (daemon(0, 0) == -1) {
                        KEEP_ERRNO((void)pidfile_remove(pfh));
                        pjdlog_exit(EX_OSERR, "Unable to daemonize");
                }

                /* Start logging to syslog. */
                pjdlog_mode_set(PJDLOG_MODE_SYSLOG);
        }
        if (pidfile != NULL || !foreground) {
                /* Write PID to a file. */
                if (pidfile_write(pfh) == -1) {
                        pjdlog_errno(LOG_WARNING,
                            "Unable to write PID to a file %s",
                            cfg->hc_pidfile);
                } else {
                        pjdlog_debug(1, "PID stored in %s.", cfg->hc_pidfile);
                }
        }

        pjdlog_info("Started successfully, running protocol version %d.",
            HAST_PROTO_VERSION);

        pjdlog_debug(1, "Listening on control address %s.",
            cfg->hc_controladdr);
        TAILQ_FOREACH(lst, &cfg->hc_listen, hl_next)
                pjdlog_info("Listening on address %s.", lst->hl_addr);

        hook_init();

        main_loop();

        exit(0);
}