/* SPDX-License-Identifier: LGPL-2.1-or-later */

#include <sys/wait.h>

#include "sd-daemon.h"

#include "fd-util.h"
#include "fs-util.h"
#include "mkdir.h"
#include "process-util.h"
#include "set.h"
#include "signal-util.h"
#include "socket-util.h"
#include "stdio-util.h"
#include "umask-util.h"
#include "userdbd-manager.h"

#define LISTEN_TIMEOUT_USEC (25 * USEC_PER_SEC)

static int start_workers(Manager *m, bool explicit_request);

static int on_sigchld(sd_event_source *s, const struct signalfd_siginfo *si, void *userdata) {
        Manager *m = userdata;

        assert(s);
        assert(m);

        for (;;) {
                siginfo_t siginfo = {};
                bool removed = false;

                if (waitid(P_ALL, 0, &siginfo, WNOHANG|WEXITED) < 0) {
                        if (errno == ECHILD)
                                break;

                        log_warning_errno(errno, "Failed to invoke waitid(): %m");
                        break;
                }
                if (siginfo.si_pid == 0)
                        break;

                if (set_remove(m->workers_dynamic, PID_TO_PTR(siginfo.si_pid)))
                        removed = true;
                if (set_remove(m->workers_fixed, PID_TO_PTR(siginfo.si_pid)))
                        removed = true;

                if (!removed) {
                        log_warning("Weird, got SIGCHLD for unknown child " PID_FMT ", ignoring.", siginfo.si_pid);
                        continue;
                }

                if (siginfo.si_code == CLD_EXITED) {
                        if (siginfo.si_status == EXIT_SUCCESS)
                                log_debug("Worker " PID_FMT " exited successfully.", siginfo.si_pid);
                        else
                                log_warning("Worker " PID_FMT " died with a failure exit status %i, ignoring.", siginfo.si_pid, siginfo.si_status);
                } else if (siginfo.si_code == CLD_KILLED)
                        log_warning("Worker " PID_FMT " was killed by signal %s, ignoring.", siginfo.si_pid, signal_to_string(siginfo.si_status));
                else if (siginfo.si_code == CLD_DUMPED)
                        log_warning("Worker " PID_FMT " dumped core by signal %s, ignoring.", siginfo.si_pid, signal_to_string(siginfo.si_status));
                else
                        log_warning("Can't handle SIGCHLD of this type");
        }

        (void) start_workers(m, false); /* Fill up workers again if we fell below the low watermark */
        return 0;
}

static int on_sigusr2(sd_event_source *s, const struct signalfd_siginfo *si, void *userdata) {
        Manager *m = userdata;

        assert(s);
        assert(m);

        (void) start_workers(m, true); /* Workers told us there's more work, let's add one more worker as long as we are below the high watermark */
        return 0;
}

int manager_new(Manager **ret) {
        _cleanup_(manager_freep) Manager *m = NULL;
        int r;

        m = new(Manager, 1);
        if (!m)
                return -ENOMEM;

        *m = (Manager) {
                .listen_fd = -1,
                .worker_ratelimit = {
                        .interval = 5 * USEC_PER_SEC,
                        .burst = 50,
                },
        };

        r = sd_event_new(&m->event);
        if (r < 0)
                return r;

        r = sd_event_add_signal(m->event, NULL, SIGINT, NULL, NULL);
        if (r < 0)
                return r;

        r = sd_event_add_signal(m->event, NULL, SIGTERM, NULL, NULL);
        if (r < 0)
                return r;

        (void) sd_event_set_watchdog(m->event, true);

        m->workers_fixed = set_new(NULL);
        m->workers_dynamic = set_new(NULL);

        if (!m->workers_fixed || !m->workers_dynamic)
                return -ENOMEM;

        r = sd_event_add_signal(m->event, &m->sigusr2_event_source, SIGUSR2, on_sigusr2, m);
        if (r < 0)
                return r;

        r = sd_event_add_signal(m->event, &m->sigchld_event_source, SIGCHLD, on_sigchld, m);
        if (r < 0)
                return r;

        *ret = TAKE_PTR(m);
        return 0;
}

Manager* manager_free(Manager *m) {
        if (!m)
                return NULL;

        set_free(m->workers_fixed);
        set_free(m->workers_dynamic);

        sd_event_source_disable_unref(m->sigusr2_event_source);
        sd_event_source_disable_unref(m->sigchld_event_source);

        sd_event_unref(m->event);

        return mfree(m);
}

static size_t manager_current_workers(Manager *m) {
        assert(m);

        return set_size(m->workers_fixed) + set_size(m->workers_dynamic);
}

static int start_one_worker(Manager *m) {
        bool fixed;
        pid_t pid;
        int r;

        assert(m);

        fixed = set_size(m->workers_fixed) < USERDB_WORKERS_MIN;

        r = safe_fork("(sd-worker)", FORK_RESET_SIGNALS|FORK_DEATHSIG|FORK_LOG, &pid);
        if (r < 0)
                return log_error_errno(r, "Failed to fork new worker child: %m");
        if (r == 0) {
                char pids[DECIMAL_STR_MAX(pid_t)];
                /* Child */

                log_close();

                r = close_all_fds(&m->listen_fd, 1);
                if (r < 0) {
                        log_error_errno(r, "Failed to close fds in child: %m");
                        _exit(EXIT_FAILURE);
                }

                log_open();

                if (m->listen_fd == 3) {
                        r = fd_cloexec(3, false);
                        if (r < 0) {
                                log_error_errno(r, "Failed to turn off O_CLOEXEC for fd 3: %m");
                                _exit(EXIT_FAILURE);
                        }
                } else {
                        if (dup2(m->listen_fd, 3) < 0) { /* dup2() creates with O_CLOEXEC off */
                                log_error_errno(errno, "Failed to move listen fd to 3: %m");
                                _exit(EXIT_FAILURE);
                        }

                        safe_close(m->listen_fd);
                }

                xsprintf(pids, PID_FMT, pid);
                if (setenv("LISTEN_PID", pids, 1) < 0) {
                        log_error_errno(errno, "Failed to set $LISTEN_PID: %m");
                        _exit(EXIT_FAILURE);
                }

                if (setenv("LISTEN_FDS", "1", 1) < 0) {
                        log_error_errno(errno, "Failed to set $LISTEN_FDS: %m");
                        _exit(EXIT_FAILURE);
                }


                if (setenv("USERDB_FIXED_WORKER", one_zero(fixed), 1) < 0) {
                        log_error_errno(errno, "Failed to set $USERDB_FIXED_WORKER: %m");
                        _exit(EXIT_FAILURE);
                }

                /* execl("/home/lennart/projects/systemd/build/systemd-userwork", "systemd-userwork", "xxxxxxxxxxxxxxxx", NULL); /\* With some extra space rename_process() can make use of *\/ */
                /* execl("/usr/bin/valgrind", "valgrind", "/home/lennart/projects/systemd/build/systemd-userwork", "systemd-userwork", "xxxxxxxxxxxxxxxx", NULL); /\* With some extra space rename_process() can make use of *\/ */

                execl(SYSTEMD_USERWORK_PATH, "systemd-userwork", "xxxxxxxxxxxxxxxx", NULL); /* With some extra space rename_process() can make use of */
                log_error_errno(errno, "Failed start worker process: %m");
                _exit(EXIT_FAILURE);
        }

        if (fixed)
                r = set_put(m->workers_fixed, PID_TO_PTR(pid));
        else
                r = set_put(m->workers_dynamic, PID_TO_PTR(pid));
        if (r < 0)
                return log_error_errno(r, "Failed to add child process to set: %m");

        return 0;
}

static int start_workers(Manager *m, bool explicit_request) {
        int r;

        assert(m);

        for (;;)  {
                size_t n;

                n = manager_current_workers(m);
                if (n >= USERDB_WORKERS_MIN && (!explicit_request || n >= USERDB_WORKERS_MAX))
                        break;

                if (!ratelimit_below(&m->worker_ratelimit)) {
                        /* If we keep starting workers too often, let's fail the whole daemon, something is wrong */
                        sd_event_exit(m->event, EXIT_FAILURE);

                        return log_error_errno(SYNTHETIC_ERRNO(EUCLEAN), "Worker threads requested too frequently, something is wrong.");
                }

                r = start_one_worker(m);
                if (r < 0)
                        return r;

                explicit_request = false;
        }

        return 0;
}

int manager_startup(Manager *m) {
        int n, r;

        assert(m);
        assert(m->listen_fd < 0);

        n = sd_listen_fds(false);
        if (n < 0)
                return log_error_errno(n, "Failed to determine number of passed file descriptors: %m");
        if (n > 1)
                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Expected one listening fd, got %i.", n);
        if (n == 1)
                m->listen_fd = SD_LISTEN_FDS_START;
        else {
                union sockaddr_union sockaddr = {
                        .un.sun_family = AF_UNIX,
                        .un.sun_path = "/run/systemd/userdb/io.systemd.Multiplexer",
                };

                r = mkdir_p("/run/systemd/userdb", 0755);
                if (r < 0)
                        return log_error_errno(r, "Failed to create /run/systemd/userdb: %m");

                m->listen_fd = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0);
                if (m->listen_fd < 0)
                        return log_error_errno(errno, "Failed to bind on socket: %m");

                (void) sockaddr_un_unlink(&sockaddr.un);

                RUN_WITH_UMASK(0000)
                        if (bind(m->listen_fd, &sockaddr.sa, SOCKADDR_UN_LEN(sockaddr.un)) < 0)
                                return log_error_errno(errno, "Failed to bind socket: %m");

                r = symlink_idempotent("io.systemd.Multiplexer",
                                       "/run/systemd/userdb/io.systemd.NameServiceSwitch", false);
                if (r < 0)
                        return log_error_errno(r, "Failed to bind io.systemd.Multiplexer: %m");

                r = symlink_idempotent("io.systemd.Multiplexer",
                                       "/run/systemd/userdb/io.systemd.DropIn", false);
                if (r < 0)
                        return log_error_errno(r, "Failed to bind io.systemd.Multiplexer: %m");

                if (listen(m->listen_fd, SOMAXCONN) < 0)
                        return log_error_errno(errno, "Failed to listen on socket: %m");
        }

        /* Let's make sure every accept() call on this socket times out after 25s. This allows workers to be
         * GC'ed on idle */
        if (setsockopt(m->listen_fd, SOL_SOCKET, SO_RCVTIMEO, TIMEVAL_STORE(LISTEN_TIMEOUT_USEC), sizeof(struct timeval)) < 0)
                return log_error_errno(errno, "Failed to se SO_RCVTIMEO: %m");

        return start_workers(m, false);
}