tree-wide: struct bdev -> struct lxc_storage

[mirror_lxc.git] / src / lxc / start.c

/*
 * lxc: linux Container library
 *
 * (C) Copyright IBM Corp. 2007, 2008
 *
 * Authors:
 * Daniel Lezcano <daniel.lezcano at free.fr>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#define _GNU_SOURCE
#include "config.h"

#include <alloca.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#include <poll.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/file.h>
#include <sys/mount.h>
#include <sys/param.h>
#include <sys/prctl.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/un.h>
#include <sys/wait.h>

#if HAVE_LIBCAP
#include <sys/capability.h>
#endif

#ifndef HAVE_DECL_PR_CAPBSET_DROP
#define PR_CAPBSET_DROP 24
#endif

#ifndef HAVE_DECL_PR_SET_NO_NEW_PRIVS
#define PR_SET_NO_NEW_PRIVS 38
#endif

#ifndef HAVE_DECL_PR_GET_NO_NEW_PRIVS
#define PR_GET_NO_NEW_PRIVS 39
#endif

#include "af_unix.h"
#include "caps.h"
#include "cgroup.h"
#include "commands.h"
#include "commands_utils.h"
#include "conf.h"
#include "console.h"
#include "error.h"
#include "log.h"
#include "lxccontainer.h"
#include "lxclock.h"
#include "lxcseccomp.h"
#include "lxcutmp.h"
#include "mainloop.h"
#include "monitor.h"
#include "namespace.h"
#include "start.h"
#include "storage.h"
#include "storage_utils.h"
#include "sync.h"
#include "utils.h"
#include "lsm/lsm.h"

lxc_log_define(lxc_start, lxc);

extern void mod_all_rdeps(struct lxc_container *c, bool inc);
static bool do_destroy_container(struct lxc_conf *conf);
static int lxc_rmdir_onedev_wrapper(void *data);
static void lxc_destroy_container_on_signal(struct lxc_handler *handler,
                                            const char *name);

static void print_top_failing_dir(const char *path)
{
        size_t len = strlen(path);
        char *copy = alloca(len + 1), *p, *e, saved;
        strcpy(copy, path);

        p = copy;
        e = copy + len;
        while (p < e) {
                while (p < e && *p == '/')
                        p++;
                while (p < e && *p != '/')
                        p++;
                saved = *p;
                *p = '\0';
                if (access(copy, X_OK)) {
                        SYSERROR("Could not access %s. Please grant it x "
                                 "access, or add an ACL for the container "
                                 "root.", copy);
                        return;
                }
                *p = saved;
        }
}

static void close_ns(int ns_fd[LXC_NS_MAX])
{
        int i;

        for (i = 0; i < LXC_NS_MAX; i++) {
                if (ns_fd[i] > -1) {
                        close(ns_fd[i]);
                        ns_fd[i] = -1;
                }
        }
}

/* preserve_ns: open /proc/@pid/ns/@ns for each namespace specified
 * in clone_flags.
 * Return true on success, false on failure.
 */
static bool preserve_ns(int ns_fd[LXC_NS_MAX], int clone_flags, pid_t pid)
{
        int i, ret;

        for (i = 0; i < LXC_NS_MAX; i++)
                ns_fd[i] = -1;

        ret = lxc_preserve_ns(pid, "");
        if (ret < 0) {
                SYSERROR("Kernel does not support attaching to namespaces.");
                return false;
        } else {
                close(ret);
        }

        for (i = 0; i < LXC_NS_MAX; i++) {
                if ((clone_flags & ns_info[i].clone_flag) == 0)
                        continue;
                ns_fd[i] = lxc_preserve_ns(pid, ns_info[i].proc_name);
                if (ns_fd[i] < 0)
                        goto error;
        }

        return true;

error:
        if (errno == ENOENT)
                SYSERROR("Kernel does not support attaching to %s namespaces.", ns_info[i].proc_name);
        else
                SYSERROR("Failed to open file descriptor for %s namespace: %s.", ns_info[i].proc_name, strerror(errno));
        close_ns(ns_fd);
        return false;
}

static int attach_ns(const int ns_fd[LXC_NS_MAX]) {
        int i;

        for (i = 0; i < LXC_NS_MAX; i++) {
                if (ns_fd[i] < 0)
                        continue;

                if (setns(ns_fd[i], 0) != 0)
                        goto error;
        }
        return 0;

error:
        SYSERROR("Failed to attach %s namespace.", ns_info[i].proc_name);
        return -1;
}

static int match_fd(int fd)
{
        return (fd == 0 || fd == 1 || fd == 2);
}

int lxc_check_inherited(struct lxc_conf *conf, bool closeall,
                        int *fds_to_ignore, size_t len_fds)
{
        struct dirent *direntp;
        int fd, fddir;
        size_t i;
        DIR *dir;

        if (conf && conf->close_all_fds)
                closeall = true;

restart:
        dir = opendir("/proc/self/fd");
        if (!dir) {
                WARN("Failed to open directory: %s.", strerror(errno));
                return -1;
        }

        fddir = dirfd(dir);

        while ((direntp = readdir(dir))) {
                if (!direntp)
                        break;

                if (!strcmp(direntp->d_name, "."))
                        continue;

                if (!strcmp(direntp->d_name, ".."))
                        continue;

                if (lxc_safe_int(direntp->d_name, &fd) < 0) {
                        INFO("Could not parse file descriptor for: %s", direntp->d_name);
                        continue;
                }

                for (i = 0; i < len_fds; i++)
                        if (fds_to_ignore[i] == fd)
                                break;

                if (fd == fddir || fd == lxc_log_fd ||
                    (i < len_fds && fd == fds_to_ignore[i]))
                        continue;

                if (current_config && fd == current_config->logfd)
                        continue;

                if (match_fd(fd))
                        continue;

                if (closeall) {
                        close(fd);
                        closedir(dir);
                        INFO("Closed inherited fd: %d.", fd);
                        goto restart;
                }
                WARN("Inherited fd: %d.", fd);
        }

        /* Only enable syslog at this point to avoid the above logging function
         * to open a new fd and make the check_inherited function enter an
         * infinite loop.
         */
        lxc_log_enable_syslog();

        closedir(dir); /* cannot fail */
        return 0;
}

static int setup_signal_fd(sigset_t *oldmask)
{
        sigset_t mask;
        int fd;

        /* Block everything except serious error signals. */
        if (sigfillset(&mask) ||
            sigdelset(&mask, SIGILL) ||
            sigdelset(&mask, SIGSEGV) ||
            sigdelset(&mask, SIGBUS) ||
            sigdelset(&mask, SIGWINCH) ||
            sigprocmask(SIG_BLOCK, &mask, oldmask)) {
                SYSERROR("Failed to set signal mask.");
                return -1;
        }

        fd = signalfd(-1, &mask, 0);
        if (fd < 0) {
                SYSERROR("Failed to create signal file descriptor.");
                return -1;
        }

        if (fcntl(fd, F_SETFD, FD_CLOEXEC)) {
                SYSERROR("Failed to set FD_CLOEXEC on the signal file descriptor: %d.", fd);
                close(fd);
                return -1;
        }

        DEBUG("Set SIGCHLD handler with file descriptor: %d.", fd);

        return fd;
}

static int signal_handler(int fd, uint32_t events, void *data,
                          struct lxc_epoll_descr *descr)
{
        struct signalfd_siginfo siginfo;
        siginfo_t info;
        int ret;
        pid_t *pid = data;
        bool init_died = false;

        ret = read(fd, &siginfo, sizeof(siginfo));
        if (ret < 0) {
                ERROR("Failed to read signal info from signal file descriptor: %d.", fd);
                return -1;
        }

        if (ret != sizeof(siginfo)) {
                ERROR("Unexpected size for siginfo struct.");
                return -1;
        }

        /* Check whether init is running. */
        info.si_pid = 0;
        ret = waitid(P_PID, *pid, &info, WEXITED | WNOWAIT | WNOHANG);
        if (ret == 0 && info.si_pid == *pid)
                init_died = true;

        if (siginfo.ssi_signo != SIGCHLD) {
                kill(*pid, siginfo.ssi_signo);
                INFO("Forwarded signal %d to pid %d.", siginfo.ssi_signo, *pid);
                return init_died ? 1 : 0;
        }

        if (siginfo.ssi_code == CLD_STOPPED) {
                INFO("Container init process was stopped.");
                return init_died ? 1 : 0;
        } else if (siginfo.ssi_code == CLD_CONTINUED) {
                INFO("Container init process was continued.");
                return init_died ? 1 : 0;
        }

        /* More robustness, protect ourself from a SIGCHLD sent
         * by a process different from the container init.
         */
        if (siginfo.ssi_pid != *pid) {
                NOTICE("Received SIGCHLD from pid %d instead of container init %d.", siginfo.ssi_pid, *pid);
                return init_died ? 1 : 0;
        }

        DEBUG("Container init process %d exited.", *pid);
        return 1;
}

static int lxc_serve_state_clients(const char *name,
                                   struct lxc_handler *handler,
                                   lxc_state_t state)
{
        ssize_t ret;
        struct lxc_list *cur, *next;
        struct state_client *client;
        struct lxc_msg msg = {.type = lxc_msg_state, .value = state};

        process_lock();

        /* Only set state under process lock held so that we don't cause
        *  lxc_cmd_add_state_client() to miss a state.
         */
        handler->state = state;
        TRACE("set container state to %s", lxc_state2str(state));

        if (lxc_list_empty(&handler->state_clients)) {
                TRACE("no state clients registered");
                process_unlock();
                lxc_monitor_send_state(name, state, handler->lxcpath);
                return 0;
        }

        strncpy(msg.name, name, sizeof(msg.name));
        msg.name[sizeof(msg.name) - 1] = 0;

        lxc_list_for_each_safe(cur, &handler->state_clients, next) {
                client = cur->elem;

                if (!client->states[state]) {
                        TRACE("state %s not registered for state client %d",
                              lxc_state2str(state), client->clientfd);
                        continue;
                }

                TRACE("sending state %s to state client %d",
                      lxc_state2str(state), client->clientfd);

        again:
                ret = send(client->clientfd, &msg, sizeof(msg), 0);
                if (ret <= 0) {
                        if (errno == EINTR) {
                                TRACE("Caught EINTR; retrying");
                                goto again;
                        }

                        ERROR("failed to send message to client");
                }

                /* kick client from list */
                close(client->clientfd);
                lxc_list_del(cur);
                free(cur->elem);
                free(cur);
        }
        process_unlock();

        return 0;
}

static int lxc_serve_state_socket_pair(const char *name,
                                       struct lxc_handler *handler,
                                       lxc_state_t state)
{
        ssize_t ret;

        if (!handler->backgrounded ||
            handler->state_socket_pair[1] < 0 ||
            state == STARTING)
                return 0;

        /* Close read end of the socket pair. */
        close(handler->state_socket_pair[0]);
        handler->state_socket_pair[0] = -1;

again:
        ret = lxc_abstract_unix_send_credential(handler->state_socket_pair[1],
                                                &(int){state}, sizeof(int));
        if (ret != sizeof(int)) {
                if (errno == EINTR)
                        goto again;
                SYSERROR("Failed to send state to %d",
                         handler->state_socket_pair[1]);
                return -1;
        }

        TRACE("Sent container state \"%s\" to %d", lxc_state2str(state),
              handler->state_socket_pair[1]);

        /* Close write end of the socket pair. */
        close(handler->state_socket_pair[1]);
        handler->state_socket_pair[1] = -1;

        return 0;
}

int lxc_set_state(const char *name, struct lxc_handler *handler,
                  lxc_state_t state)
{
        int ret;

        ret = lxc_serve_state_socket_pair(name, handler, state);
        if (ret < 0) {
                ERROR("Failed to synchronize via anonymous pair of unix sockets");
                return -1;
        }

        ret = lxc_serve_state_clients(name, handler, state);
        if (ret < 0)
                return -1;

        /* This function will try to connect to the legacy lxc-monitord state
         * server and only exists for backwards compatibility.
         */
        lxc_monitor_send_state(name, state, handler->lxcpath);

        return 0;
}

int lxc_poll(const char *name, struct lxc_handler *handler)
{
        int sigfd = handler->sigfd;
        int pid = handler->pid;
        struct lxc_epoll_descr descr;

        if (lxc_mainloop_open(&descr)) {
                ERROR("Failed to create LXC mainloop.");
                goto out_sigfd;
        }

        if (lxc_mainloop_add_handler(&descr, sigfd, signal_handler, &pid)) {
                ERROR("Failed to add signal handler with file descriptor %d to LXC mainloop.", sigfd);
                goto out_mainloop_open;
        }

        if (lxc_console_mainloop_add(&descr, handler->conf)) {
                ERROR("Failed to add console handler to LXC mainloop.");
                goto out_mainloop_open;
        }

        if (lxc_cmd_mainloop_add(name, &descr, handler)) {
                ERROR("Failed to add command handler to LXC mainloop.");
                goto out_mainloop_open;
        }

        if (handler->conf->need_utmp_watch) {
                #if HAVE_LIBCAP
                if (lxc_utmp_mainloop_add(&descr, handler)) {
                        ERROR("Failed to add utmp handler to LXC mainloop.");
                        goto out_mainloop_open;
                }
                #else
                        DEBUG("Not starting utmp handler as CAP_SYS_BOOT cannot be dropped without capabilities support.");
                #endif
        }
        TRACE("lxc mainloop is ready");

        return lxc_mainloop(&descr, -1);

out_mainloop_open:
        lxc_mainloop_close(&descr);

out_sigfd:
        close(sigfd);

        return -1;
}

void lxc_free_handler(struct lxc_handler *handler)
{
        if (handler->conf && handler->conf->maincmd_fd)
                close(handler->conf->maincmd_fd);

        if (handler->state_socket_pair[0] >= 0)
                close(handler->state_socket_pair[0]);

        if (handler->state_socket_pair[1] >= 0)
                close(handler->state_socket_pair[1]);

        if (handler->name)
                free(handler->name);

        handler->conf = NULL;
        free(handler);
}

struct lxc_handler *lxc_init_handler(const char *name, struct lxc_conf *conf,
                                     const char *lxcpath, bool daemonize)
{
        int i, ret;
        struct lxc_handler *handler;

        handler = malloc(sizeof(*handler));
        if (!handler) {
                ERROR("failed to allocate memory");
                return NULL;
        }

        memset(handler, 0, sizeof(*handler));

        handler->ttysock[0] = handler->ttysock[1] = -1;
        handler->conf = conf;
        handler->lxcpath = lxcpath;
        handler->pinfd = -1;
        handler->state_socket_pair[0] = handler->state_socket_pair[1] = -1;
        lxc_list_init(&handler->state_clients);

        for (i = 0; i < LXC_NS_MAX; i++)
                handler->nsfd[i] = -1;

        handler->name = strdup(name);
        if (!handler->name) {
                ERROR("failed to allocate memory");
                goto on_error;
        }

        if (daemonize && !handler->conf->reboot) {
                /* Create socketpair() to synchronize on daemonized startup.
                 * When the container reboots we don't need to synchronize again
                 * currently so don't open another socketpair().
                 */
                ret = socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0,
                                 handler->state_socket_pair);
                if (ret < 0) {
                        ERROR("Failed to create anonymous pair of unix sockets");
                        goto on_error;
                }
                TRACE("Created anonymous pair {%d,%d} of unix sockets",
                      handler->state_socket_pair[0],
                      handler->state_socket_pair[1]);
        }

        if (lxc_cmd_init(name, handler, lxcpath)) {
                ERROR("failed to set up command socket");
                goto on_error;
        }

        TRACE("unix domain socket %d for command server is ready",
              handler->conf->maincmd_fd);

        return handler;

on_error:
        lxc_free_handler(handler);

        return NULL;
}

int lxc_init(const char *name, struct lxc_handler *handler)
{
        struct lxc_conf *conf = handler->conf;

        lsm_init();
        TRACE("initialized LSM");

        if (lxc_read_seccomp_config(conf) != 0) {
                ERROR("Failed loading seccomp policy.");
                goto out_close_maincmd_fd;
        }
        TRACE("read seccomp policy");

        /* Begin by setting the state to STARTING. */
        if (lxc_set_state(name, handler, STARTING)) {
                ERROR("Failed to set state for container \"%s\" to \"%s\".", name, lxc_state2str(STARTING));
                goto out_close_maincmd_fd;
        }
        TRACE("set container state to \"STARTING\"");

        /* Start of environment variable setup for hooks. */
        if (name && setenv("LXC_NAME", name, 1))
                SYSERROR("Failed to set environment variable: LXC_NAME=%s.", name);

        if (conf->rcfile && setenv("LXC_CONFIG_FILE", conf->rcfile, 1))
                SYSERROR("Failed to set environment variable: LXC_CONFIG_FILE=%s.", conf->rcfile);

        if (conf->rootfs.mount && setenv("LXC_ROOTFS_MOUNT", conf->rootfs.mount, 1))
                SYSERROR("Failed to set environment variable: LXC_ROOTFS_MOUNT=%s.", conf->rootfs.mount);

        if (conf->rootfs.path && setenv("LXC_ROOTFS_PATH", conf->rootfs.path, 1))
                SYSERROR("Failed to set environment variable: LXC_ROOTFS_PATH=%s.", conf->rootfs.path);

        if (conf->console.path && setenv("LXC_CONSOLE", conf->console.path, 1))
                SYSERROR("Failed to set environment variable: LXC_CONSOLE=%s.", conf->console.path);

        if (conf->console.log_path && setenv("LXC_CONSOLE_LOGPATH", conf->console.log_path, 1))
                SYSERROR("Failed to set environment variable: LXC_CONSOLE_LOGPATH=%s.", conf->console.log_path);

        if (setenv("LXC_CGNS_AWARE", "1", 1))
                SYSERROR("Failed to set environment variable LXC_CGNS_AWARE=1.");
        /* End of environment variable setup for hooks. */

        TRACE("set environment variables");

        if (run_lxc_hooks(name, "pre-start", conf, handler->lxcpath, NULL)) {
                ERROR("Failed to run lxc.hook.pre-start for container \"%s\".", name);
                goto out_aborting;
        }
        TRACE("ran pre-start hooks");

        /* The signal fd has to be created before forking otherwise if the child
         * process exits before we setup the signal fd, the event will be lost
         * and the command will be stuck.
         */
        handler->sigfd = setup_signal_fd(&handler->oldmask);
        if (handler->sigfd < 0) {
                ERROR("Failed to setup SIGCHLD fd handler.");
                goto out_delete_tty;
        }
        TRACE("set up signal fd");

        /* Do this after setting up signals since it might unblock SIGWINCH. */
        if (lxc_console_create(conf)) {
                ERROR("Failed to create console for container \"%s\".", name);
                goto out_restore_sigmask;
        }
        TRACE("created console");

        if (lxc_ttys_shift_ids(conf) < 0) {
                ERROR("Failed to shift tty into container.");
                goto out_restore_sigmask;
        }
        TRACE("shifted tty ids");

        INFO("container \"%s\" is initialized", name);
        return 0;

out_restore_sigmask:
        sigprocmask(SIG_SETMASK, &handler->oldmask, NULL);
out_delete_tty:
        lxc_delete_tty(&conf->tty_info);
out_aborting:
        lxc_set_state(name, handler, ABORTING);
out_close_maincmd_fd:
        close(conf->maincmd_fd);
        conf->maincmd_fd = -1;
        return -1;
}

void lxc_fini(const char *name, struct lxc_handler *handler)
{
        int i, rc;
        struct lxc_list *cur, *next;
        pid_t self = getpid();
        char *namespaces[LXC_NS_MAX + 1];
        size_t namespace_count = 0;

        /* The STOPPING state is there for future cleanup code which can take
         * awhile.
         */
        lxc_set_state(name, handler, STOPPING);

        for (i = 0; i < LXC_NS_MAX; i++) {
                if (handler->nsfd[i] != -1) {
                        rc = asprintf(&namespaces[namespace_count], "%s:/proc/%d/fd/%d",
                                      ns_info[i].proc_name, self, handler->nsfd[i]);
                        if (rc == -1) {
                                SYSERROR("Failed to allocate memory.");
                                break;
                        }
                        ++namespace_count;
                }
        }
        namespaces[namespace_count] = NULL;

        if (handler->conf->reboot && setenv("LXC_TARGET", "reboot", 1))
                SYSERROR("Failed to set environment variable: LXC_TARGET=reboot.");

        if (!handler->conf->reboot && setenv("LXC_TARGET", "stop", 1))
                SYSERROR("Failed to set environment variable: LXC_TARGET=stop.");

        if (run_lxc_hooks(name, "stop", handler->conf, handler->lxcpath, namespaces))
                ERROR("Failed to run lxc.hook.stop for container \"%s\".", name);

        while (namespace_count--)
                free(namespaces[namespace_count]);
        for (i = 0; i < LXC_NS_MAX; i++) {
                if (handler->nsfd[i] != -1) {
                        close(handler->nsfd[i]);
                        handler->nsfd[i] = -1;
                }
        }

        if (handler->netnsfd >= 0) {
                close(handler->netnsfd);
                handler->netnsfd = -1;
        }

        lxc_set_state(name, handler, STOPPED);

        if (run_lxc_hooks(name, "post-stop", handler->conf, handler->lxcpath, NULL)) {
                ERROR("Failed to run lxc.hook.post-stop for container \"%s\".", name);
                if (handler->conf->reboot) {
                        WARN("Container will be stopped instead of rebooted.");
                        handler->conf->reboot = 0;
                        if (setenv("LXC_TARGET", "stop", 1))
                                WARN("Failed to set environment variable: LXC_TARGET=stop.");
                }
        }

        /* Reset mask set by setup_signal_fd. */
        if (sigprocmask(SIG_SETMASK, &handler->oldmask, NULL))
                WARN("Failed to restore signal mask.");

        lxc_console_delete(&handler->conf->console);
        lxc_delete_tty(&handler->conf->tty_info);

        /* close the command socket */
        close(handler->conf->maincmd_fd);
        handler->conf->maincmd_fd = -1;

        /* The command socket is now closed, no more state clients can register
         * themselves from now on. So free the list of state clients.
         */
        lxc_list_for_each_safe(cur, &handler->state_clients, next) {
                struct state_client *client = cur->elem;
                /* close state client socket */
                close(client->clientfd);
                lxc_list_del(cur);
                free(cur->elem);
                free(cur);
        }

        free(handler->name);
        if (handler->ttysock[0] != -1) {
                close(handler->ttysock[0]);
                close(handler->ttysock[1]);
        }

        if (handler->conf->ephemeral == 1 && handler->conf->reboot != 1)
                lxc_destroy_container_on_signal(handler, name);

        cgroup_destroy(handler);
        free(handler);
}

void lxc_abort(const char *name, struct lxc_handler *handler)
{
        int ret, status;

        lxc_set_state(name, handler, ABORTING);
        if (handler->pid > 0)
                kill(handler->pid, SIGKILL);
        while ((ret = waitpid(-1, &status, 0)) > 0) {
                ;
        }
}

#include <sys/reboot.h>
#include <linux/reboot.h>

/* reboot(LINUX_REBOOT_CMD_CAD_ON) will return -EINVAL in a child pid namespace
 * if container reboot support exists.  Otherwise, it will either succeed or
 * return -EPERM.
 */
static int container_reboot_supported(void *arg)
{
        int *cmd = arg;
        int ret;

        ret = reboot(*cmd);
        if (ret == -1 && errno == EINVAL)
                return 1;
        return 0;
}

static int must_drop_cap_sys_boot(struct lxc_conf *conf)
{
        FILE *f;
        int ret, cmd, v, flags;
        long stack_size = 4096;
        void *stack = alloca(stack_size);
        int status;
        pid_t pid;

        f = fopen("/proc/sys/kernel/ctrl-alt-del", "r");
        if (!f) {
                DEBUG("failed to open /proc/sys/kernel/ctrl-alt-del");
                return 1;
        }

        ret = fscanf(f, "%d", &v);
        fclose(f);
        if (ret != 1) {
                DEBUG("Failed to read /proc/sys/kernel/ctrl-alt-del.");
                return 1;
        }
        cmd = v ? LINUX_REBOOT_CMD_CAD_ON : LINUX_REBOOT_CMD_CAD_OFF;

        flags = CLONE_NEWPID | SIGCHLD;
        if (!lxc_list_empty(&conf->id_map))
                flags |= CLONE_NEWUSER;

#ifdef __ia64__
        pid = __clone2(container_reboot_supported, stack, stack_size, flags,  &cmd);
#else
        stack += stack_size;
        pid = clone(container_reboot_supported, stack, flags, &cmd);
#endif
        if (pid < 0) {
                if (flags & CLONE_NEWUSER)
                        ERROR("Failed to clone (%#x): %s (includes CLONE_NEWUSER).", flags, strerror(errno));
                else
                        ERROR("Failed to clone (%#x): %s.", flags, strerror(errno));
                return -1;
        }
        if (wait(&status) < 0) {
                SYSERROR("Unexpected wait error: %s.", strerror(errno));
                return -1;
        }

        if (WEXITSTATUS(status) != 1)
                return 1;

        return 0;
}

/* netpipe is used in the unprivileged case to transfer the ifindexes from
 * parent to child
 */
static int netpipe = -1;

static inline int count_veths(struct lxc_list *network)
{
        struct lxc_list *iterator;
        struct lxc_netdev *netdev;
        int count = 0;

        lxc_list_for_each(iterator, network) {
                netdev = iterator->elem;
                if (netdev->type != LXC_NET_VETH)
                        continue;
                count++;
        }
        return count;
}

static int read_unpriv_netifindex(struct lxc_list *network)
{
        struct lxc_list *iterator;
        struct lxc_netdev *netdev;

        if (netpipe == -1)
                return 0;
        lxc_list_for_each(iterator, network) {
                netdev = iterator->elem;
                if (netdev->type != LXC_NET_VETH)
                        continue;
                if (!(netdev->name = malloc(IFNAMSIZ))) {
                        ERROR("Out of memory.");
                        close(netpipe);
                        return -1;
                }
                if (read(netpipe, netdev->name, IFNAMSIZ) != IFNAMSIZ) {
                        close(netpipe);
                        return -1;
                }
        }
        close(netpipe);
        return 0;
}

static int do_start(void *data)
{
        struct lxc_list *iterator;
        struct lxc_handler *handler = data;
        int devnull_fd = -1, ret;
        char path[PATH_MAX];

        if (sigprocmask(SIG_SETMASK, &handler->oldmask, NULL)) {
                SYSERROR("Failed to set signal mask.");
                return -1;
        }

        /* This prctl must be before the synchro, so if the parent dies before
         * we set the parent death signal, we will detect its death with the
         * synchro right after, otherwise we have a window where the parent can
         * exit before we set the pdeath signal leading to a unsupervized
         * container.
         */
        if (prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0)) {
                SYSERROR("Failed to set PR_SET_PDEATHSIG to SIGKILL.");
                return -1;
        }

        lxc_sync_fini_parent(handler);

        /* Don't leak the pinfd to the container. */
        if (handler->pinfd >= 0) {
                close(handler->pinfd);
        }

        if (lxc_sync_wait_parent(handler, LXC_SYNC_STARTUP))
                return -1;

        /* Unshare CLONE_NEWNET after CLONE_NEWUSER. See
         * https://github.com/lxc/lxd/issues/1978.
         */
        if ((handler->clone_flags & (CLONE_NEWNET | CLONE_NEWUSER)) ==
            (CLONE_NEWNET | CLONE_NEWUSER)) {
                ret = unshare(CLONE_NEWNET);
                if (ret < 0) {
                        SYSERROR("Failed to unshare CLONE_NEWNET.");
                        goto out_warn_father;
                }
                INFO("Unshared CLONE_NEWNET.");
        }

        /* Tell the parent task it can begin to configure the container and wait
         * for it to finish.
         */
        if (lxc_sync_barrier_parent(handler, LXC_SYNC_CONFIGURE))
                return -1;

        if (read_unpriv_netifindex(&handler->conf->network) < 0)
                goto out_warn_father;

        /* If we are in a new user namespace, become root there to have
         * privilege over our namespace.
         */
        if (!lxc_list_empty(&handler->conf->id_map)) {
                if (lxc_switch_uid_gid(0, 0) < 0)
                        goto out_warn_father;

                /* Drop groups only after we switched to a valid gid in the new
                 * user namespace.
                 */
                if (lxc_setgroups(0, NULL) < 0)
                        goto out_warn_father;
        }

        if (access(handler->lxcpath, X_OK)) {
                print_top_failing_dir(handler->lxcpath);
                goto out_warn_father;
        }

        #if HAVE_LIBCAP
        if (handler->conf->need_utmp_watch) {
                if (prctl(PR_CAPBSET_DROP, CAP_SYS_BOOT, 0, 0, 0)) {
                        SYSERROR("Failed to remove the CAP_SYS_BOOT capability.");
                        goto out_warn_father;
                }
                DEBUG("Dropped the CAP_SYS_BOOT capability.");
        }
        #endif

        ret = snprintf(path, sizeof(path), "%s/dev/null", handler->conf->rootfs.mount);
        if (ret < 0 || ret >= sizeof(path))
                goto out_warn_father;

        /* In order to checkpoint restore, we need to have everything in the
         * same mount namespace. However, some containers may not have a
         * reasonable /dev (in particular, they may not have /dev/null), so we
         * can't set init's std fds to /dev/null by opening it from inside the
         * container.
         *
         * If that's the case, fall back to using the host's /dev/null. This
         * means that migration won't work, but at least we won't spew output
         * where it isn't wanted.
         */
        if (handler->backgrounded && !handler->conf->autodev && access(path, F_OK) < 0) {
                devnull_fd = open_devnull();

                if (devnull_fd < 0)
                        goto out_warn_father;
                WARN("Using /dev/null from the host for container init's "
                     "standard file descriptors. Migration will not work.");
        }

        /* Ask father to setup cgroups and wait for him to finish. */
        if (lxc_sync_barrier_parent(handler, LXC_SYNC_CGROUP))
                goto out_error;

        /* Unshare cgroup namespace after we have setup our cgroups. If we do it
         * earlier we end up with a wrong view of /proc/self/cgroup. For
         * example, assume we unshare(CLONE_NEWCGROUP) first, and then create
         * the cgroup for the container, say /sys/fs/cgroup/cpuset/lxc/c, then
         * /proc/self/cgroup would show us:
         *
         *      8:cpuset:/lxc/c
         *
         * whereas it should actually show
         *
         *      8:cpuset:/
         */
        if (cgns_supported()) {
                if (unshare(CLONE_NEWCGROUP) < 0) {
                        INFO("Failed to unshare CLONE_NEWCGROUP.");
                        goto out_warn_father;
                }
                INFO("Unshared CLONE_NEWCGROUP.");
        }

        /* Setup the container, ip, names, utsname, ... */
        if (lxc_setup(handler)) {
                ERROR("Failed to setup container \"%s\".", handler->name);
                goto out_warn_father;
        }

        /* Set the label to change to when we exec(2) the container's init. */
        if (lsm_process_label_set(NULL, handler->conf, 1, 1) < 0)
                goto out_warn_father;

        /* Set PR_SET_NO_NEW_PRIVS after we changed the lsm label. If we do it
         * before we aren't allowed anymore.
         */
        if (handler->conf->no_new_privs) {
                if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) < 0) {
                        SYSERROR("Could not set PR_SET_NO_NEW_PRIVS to block execve() gainable privileges.");
                        goto out_warn_father;
                }
                DEBUG("Set PR_SET_NO_NEW_PRIVS to block execve() gainable privileges.");
        }

        /* Some init's such as busybox will set sane tty settings on stdin,
         * stdout, stderr which it thinks is the console. We already set them
         * the way we wanted on the real terminal, and we want init to do its
         * setup on its console ie. the pty allocated in lxc_console_create() so
         * make sure that that pty is stdin,stdout,stderr.
         */
         if (handler->conf->console.slave >= 0)
                 if (set_stdfds(handler->conf->console.slave) < 0) {
                        ERROR("Failed to redirect std{in,out,err} to pty file "
                              "descriptor %d",
                              handler->conf->console.slave);
                        goto out_warn_father;
                 }

        /* If we mounted a temporary proc, then unmount it now. */
        tmp_proc_unmount(handler->conf);

        if (lxc_seccomp_load(handler->conf) != 0)
                goto out_warn_father;

        if (run_lxc_hooks(handler->name, "start", handler->conf, handler->lxcpath, NULL)) {
                ERROR("Failed to run lxc.hook.start for container \"%s\".", handler->name);
                goto out_warn_father;
        }

        /* The container has been setup. We can now switch to an unprivileged
         * uid/gid.
         */
        if (handler->conf->is_execute) {
                bool have_cap_setgid;
                uid_t new_uid = handler->conf->init_uid;
                gid_t new_gid = handler->conf->init_gid;

                /* If we are in a new user namespace we already dropped all
                 * groups when we switched to root in the new user namespace
                 * further above. Only drop groups if we can, so ensure that we
                 * have necessary privilege.
                 */
                #if HAVE_LIBCAP
                have_cap_setgid = lxc_proc_cap_is_set(CAP_SETGID, CAP_EFFECTIVE);
                #else
                have_cap_setgid = false;
                #endif
                if (lxc_list_empty(&handler->conf->id_map) && have_cap_setgid) {
                        if (lxc_setgroups(0, NULL) < 0)
                                goto out_warn_father;
                }

                if (lxc_switch_uid_gid(new_uid, new_gid) < 0)
                        goto out_warn_father;
        }

        /* The clearenv() and putenv() calls have been moved here to allow us to
         * use environment variables passed to the various hooks, such as the
         * start hook above. Not all of the variables like CONFIG_PATH or ROOTFS
         * are valid in this context but others are.
         */
        if (clearenv()) {
                SYSERROR("Failed to clear environment.");
                /* Don't error out though. */
        }

        lxc_list_for_each(iterator, &handler->conf->environment) {
                if (putenv((char *)iterator->elem)) {
                        SYSERROR("Failed to set environment variable: %s.", (char *)iterator->elem);
                        goto out_warn_father;
                }
        }

        if (putenv("container=lxc")) {
                SYSERROR("Failed to set environment variable: container=lxc.");
                goto out_warn_father;
        }

        if (handler->conf->pty_names) {
                if (putenv(handler->conf->pty_names)) {
                        SYSERROR("Failed to set environment variable for container ptys.");
                        goto out_warn_father;
                }
        }

        close(handler->sigfd);

        if (devnull_fd < 0) {
                devnull_fd = open_devnull();

                if (devnull_fd < 0)
                        goto out_warn_father;
        }

        if (handler->conf->console.slave < 0 && handler->backgrounded)
                if (set_stdfds(devnull_fd) < 0) {
                        ERROR("Failed to redirect std{in,out,err} to "
                              "\"/dev/null\"");
                        goto out_warn_father;
                }

        if (devnull_fd >= 0) {
                close(devnull_fd);
                devnull_fd = -1;
        }

        setsid();

        if (lxc_sync_barrier_parent(handler, LXC_SYNC_CGROUP_LIMITS))
                goto out_warn_father;

        /* After this call, we are in error because this ops should not return
         * as it execs.
         */
        handler->ops->start(handler, handler->data);

out_warn_father:
        /* We want the parent to know something went wrong, so we return a
         * special error code.
         */
        lxc_sync_wake_parent(handler, LXC_SYNC_ERROR);

out_error:
        if (devnull_fd >= 0)
                close(devnull_fd);

        return -1;
}

static int save_phys_nics(struct lxc_conf *conf)
{
        struct lxc_list *iterator;
        int am_root = (getuid() == 0);

        if (!am_root)
                return 0;

        lxc_list_for_each(iterator, &conf->network) {
                struct lxc_netdev *netdev = iterator->elem;

                if (netdev->type != LXC_NET_PHYS)
                        continue;
                conf->saved_nics = realloc(conf->saved_nics,
                                (conf->num_savednics+1)*sizeof(struct saved_nic));
                if (!conf->saved_nics)
                        return -1;
                conf->saved_nics[conf->num_savednics].ifindex = netdev->ifindex;
                conf->saved_nics[conf->num_savednics].orig_name = strdup(netdev->link);
                if (!conf->saved_nics[conf->num_savednics].orig_name)
                        return -1;
                INFO("Stored saved_nic #%d idx %d name %s.", conf->num_savednics,
                        conf->saved_nics[conf->num_savednics].ifindex,
                        conf->saved_nics[conf->num_savednics].orig_name);
                conf->num_savednics++;
        }

        return 0;
}

static int lxc_recv_ttys_from_child(struct lxc_handler *handler)
{
        int i;
        int *ttyfds;
        struct lxc_pty_info *pty_info;
        int ret = -1;
        int sock = handler->ttysock[1];
        struct lxc_conf *conf = handler->conf;
        struct lxc_tty_info *tty_info = &conf->tty_info;
        size_t num_ttyfds = (2 * conf->tty);

        if (!conf->tty)
                return 0;

        tty_info->pty_info = malloc(sizeof(*tty_info->pty_info) * conf->tty);
        if (!tty_info->pty_info)
                return -1;

        ttyfds = malloc(num_ttyfds * sizeof(int));
        if (!ttyfds)
                return -1;

        ret = lxc_abstract_unix_recv_fds(sock, ttyfds, num_ttyfds, NULL, 0);
        for (i = 0; (ret >= 0 && *ttyfds != -1) && (i < num_ttyfds); i++) {
                pty_info = &tty_info->pty_info[i / 2];
                pty_info->busy = 0;
                pty_info->slave = ttyfds[i++];
                pty_info->master = ttyfds[i];
                TRACE("received pty with master fd %d and slave fd %d from "
                      "parent", pty_info->master, pty_info->slave);
        }

        tty_info->nbtty = conf->tty;

        free(ttyfds);

        if (ret < 0)
                ERROR("failed to receive %d ttys from child: %s", conf->tty,
                      strerror(errno));
        else
                TRACE("received %d ttys from child", conf->tty);

        return ret;
}

void resolve_clone_flags(struct lxc_handler *handler)
{
        handler->clone_flags = CLONE_NEWPID | CLONE_NEWNS;

        if (!lxc_list_empty(&handler->conf->id_map))
                handler->clone_flags |= CLONE_NEWUSER;

        if (handler->conf->inherit_ns_fd[LXC_NS_NET] == -1) {
                if (!lxc_requests_empty_network(handler))
                        handler->clone_flags |= CLONE_NEWNET;
        } else {
                INFO("Inheriting a NET namespace.");
        }

        if (handler->conf->inherit_ns_fd[LXC_NS_IPC] == -1)
                handler->clone_flags |= CLONE_NEWIPC;
        else
                INFO("Inheriting an IPC namespace.");

        if (handler->conf->inherit_ns_fd[LXC_NS_UTS] == -1)
                handler->clone_flags |= CLONE_NEWUTS;
        else
                INFO("Inheriting a UTS namespace.");
}

/* lxc_spawn() performs crucial setup tasks and clone()s the new process which
 * exec()s the requested container binary.
 * Note that lxc_spawn() runs in the parent namespaces. Any operations performed
 * right here should be double checked if they'd pose a security risk. (For
 * example, any {u}mount() operations performed here will be reflected on the
 * host!)
 */
static int lxc_spawn(struct lxc_handler *handler)
{
        int failed_before_rename = 0;
        const char *name = handler->name;
        bool cgroups_connected = false;
        int saved_ns_fd[LXC_NS_MAX];
        int preserve_mask = 0, i, flags;
        int netpipepair[2], nveths;
        bool wants_to_map_ids;
        struct lxc_list *id_map;

        netpipe = -1;
        id_map = &handler->conf->id_map;
        wants_to_map_ids = !lxc_list_empty(id_map);

        for (i = 0; i < LXC_NS_MAX; i++)
                if (handler->conf->inherit_ns_fd[i] != -1)
                        preserve_mask |= ns_info[i].clone_flag;

        if (lxc_sync_init(handler))
                return -1;

        if (socketpair(AF_UNIX, SOCK_DGRAM, 0, handler->ttysock) < 0) {
                lxc_sync_fini(handler);
                return -1;
        }

        resolve_clone_flags(handler);

        if (handler->clone_flags & CLONE_NEWNET) {
                if (!lxc_list_empty(&handler->conf->network)) {

                        /* Find gateway addresses from the link device, which is
                         * no longer accessible inside the container. Do this
                         * before creating network interfaces, since goto
                         * out_delete_net does not work before lxc_clone.
                         */
                        if (lxc_find_gateway_addresses(handler)) {
                                ERROR("Failed to find gateway addresses.");
                                lxc_sync_fini(handler);
                                return -1;
                        }

                        /* That should be done before the clone because we will
                         * fill the netdev index and use them in the child.
                         */
                        if (lxc_setup_networks_in_parent_namespaces(handler)) {
                                ERROR("Failed to create the network.");
                                lxc_sync_fini(handler);
                                return -1;
                        }
                }

                if (save_phys_nics(handler->conf)) {
                        ERROR("Failed to save physical nic info.");
                        goto out_abort;
                }
        }

        if (!cgroup_init(handler)) {
                ERROR("Failed initializing cgroup support.");
                goto out_delete_net;
        }

        cgroups_connected = true;

        if (!cgroup_create(handler)) {
                ERROR("Failed creating cgroups.");
                goto out_delete_net;
        }

        /* If the rootfs is not a blockdev, prevent the container from marking
         * it readonly.
         * If the container is unprivileged then skip rootfs pinning.
         */
        if (!wants_to_map_ids) {
                handler->pinfd = pin_rootfs(handler->conf->rootfs.path);
                if (handler->pinfd == -1)
                        INFO("Failed to pin the rootfs for container \"%s\".", handler->name);
        }

        if (!preserve_ns(saved_ns_fd, preserve_mask, getpid()))
                goto out_delete_net;

        if (attach_ns(handler->conf->inherit_ns_fd) < 0)
                goto out_delete_net;

        if (am_unpriv() && (nveths = count_veths(&handler->conf->network))) {
                if (pipe(netpipepair) < 0) {
                        SYSERROR("Failed to create pipe.");
                        goto out_delete_net;
                }
                /* Store netpipe in the global var for do_start's use. */
                netpipe = netpipepair[0];
        }

        /* Create a process in a new set of namespaces. */
        flags = handler->clone_flags;
        if (handler->clone_flags & CLONE_NEWUSER) {
                /* If CLONE_NEWUSER and CLONE_NEWNET was requested, we need to
                 * clone a new user namespace first and only later unshare our
                 * network namespace to ensure that network devices ownership is
                 * set up correctly.
                 */
                flags &= ~CLONE_NEWNET;
        }
        handler->pid = lxc_clone(do_start, handler, flags);
        if (handler->pid < 0) {
                SYSERROR("Failed to clone a new set of namespaces.");
                goto out_delete_net;
        }
        for (i = 0; i < LXC_NS_MAX; i++)
                if (flags & ns_info[i].clone_flag)
                        INFO("Cloned %s.", ns_info[i].flag_name);

        if (!preserve_ns(handler->nsfd, handler->clone_flags | preserve_mask, handler->pid))
                INFO("Failed to preserve namespace for lxc.hook.stop.");

        if (attach_ns(saved_ns_fd))
                WARN("Failed to restore saved namespaces.");

        lxc_sync_fini_child(handler);

        /* Map the container uids. The container became an invalid userid the
         * moment it was cloned with CLONE_NEWUSER. This call doesn't change
         * anything immediately, but allows the container to setuid(0) (0 being
         * mapped to something else on the host.) later to become a valid uid
         * again.
         */
        if (wants_to_map_ids && lxc_map_ids(id_map, handler->pid)) {
                ERROR("Failed to set up id mapping.");
                goto out_delete_net;
        }

        if (lxc_sync_wake_child(handler, LXC_SYNC_STARTUP)) {
                failed_before_rename = 1;
                goto out_delete_net;
        }

        if (lxc_sync_wait_child(handler, LXC_SYNC_CONFIGURE)) {
                failed_before_rename = 1;
                goto out_delete_net;
        }

        if (!cgroup_create_legacy(handler)) {
                ERROR("Failed to setup legacy cgroups for container \"%s\".", name);
                goto out_delete_net;
        }
        if (!cgroup_setup_limits(handler, false)) {
                ERROR("Failed to setup cgroup limits for container \"%s\".", name);
                goto out_delete_net;
        }

        if (!cgroup_enter(handler))
                goto out_delete_net;

        if (!cgroup_chown(handler))
                goto out_delete_net;

        if (failed_before_rename)
                goto out_delete_net;

        /* Create the network configuration. */
        if (handler->clone_flags & CLONE_NEWNET) {
                if (lxc_assign_network(handler->lxcpath, handler->name,
                                       &handler->conf->network, handler->pid)) {
                        ERROR("Failed to create the configured network.");
                        goto out_delete_net;
                }
        }

        if (netpipe != -1) {
                struct lxc_list *iterator;
                struct lxc_netdev *netdev;

                close(netpipe);
                lxc_list_for_each(iterator, &handler->conf->network) {
                        netdev = iterator->elem;
                        if (netdev->type != LXC_NET_VETH)
                                continue;
                        if (write(netpipepair[1], netdev->name, IFNAMSIZ) != IFNAMSIZ) {
                                ERROR("Error writing veth name to container.");
                                goto out_delete_net;
                        }
                }
                close(netpipepair[1]);
        }

        /* Tell the child to continue its initialization. We'll get
         * LXC_SYNC_CGROUP when it is ready for us to setup cgroups.
         */
        if (lxc_sync_barrier_child(handler, LXC_SYNC_POST_CONFIGURE))
                goto out_delete_net;

        if (!lxc_list_empty(&handler->conf->limits) && setup_resource_limits(&handler->conf->limits, handler->pid)) {
                ERROR("failed to setup resource limits for '%s'", name);
                goto out_delete_net;
        }

        if (lxc_sync_barrier_child(handler, LXC_SYNC_CGROUP_UNSHARE))
                goto out_delete_net;

        if (!cgroup_setup_limits(handler, true)) {
                ERROR("Failed to setup the devices cgroup for container \"%s\".", name);
                goto out_delete_net;
        }
        TRACE("Set up cgroup device limits");

        cgroup_disconnect();
        cgroups_connected = false;

        /* Tell the child to complete its initialization and wait for it to exec
         * or return an error. (The child will never return
         * LXC_SYNC_POST_CGROUP+1. It will either close the sync pipe, causing
         * lxc_sync_barrier_child to return success, or return a different
         * value, causing us to error out).
         */
        if (lxc_sync_barrier_child(handler, LXC_SYNC_POST_CGROUP))
                return -1;

        /* Read tty fds allocated by child. */
        if (lxc_recv_ttys_from_child(handler) < 0) {
                ERROR("Failed to receive tty info from child process.");
                goto out_delete_net;
        }

        if (handler->ops->post_start(handler, handler->data))
                goto out_abort;

        if (lxc_set_state(name, handler, RUNNING)) {
                ERROR("Failed to set state for container \"%s\" to \"%s\".", name,
                      lxc_state2str(RUNNING));
                goto out_abort;
        }

        lxc_sync_fini(handler);
        handler->netnsfd = lxc_preserve_ns(handler->pid, "net");

        return 0;

out_delete_net:
        if (cgroups_connected)
                cgroup_disconnect();
        if (handler->clone_flags & CLONE_NEWNET)
                lxc_delete_network(handler);
out_abort:
        lxc_abort(name, handler);
        lxc_sync_fini(handler);
        if (handler->pinfd >= 0) {
                close(handler->pinfd);
                handler->pinfd = -1;
        }

        return -1;
}

int __lxc_start(const char *name, struct lxc_handler *handler,
                struct lxc_operations* ops, void *data, const char *lxcpath,
                bool backgrounded)
{
        int status;
        int err = -1;
        bool removed_all_netdevs = true;
        struct lxc_conf *conf = handler->conf;

        if (lxc_init(name, handler) < 0) {
                ERROR("Failed to initialize container \"%s\".", name);
                return -1;
        }
        handler->ops = ops;
        handler->data = data;
        handler->backgrounded = backgrounded;
        handler->netnsfd = -1;

        if (must_drop_cap_sys_boot(handler->conf)) {
                #if HAVE_LIBCAP
                DEBUG("Dropping CAP_SYS_BOOT capability.");
                #else
                DEBUG("Not dropping CAP_SYS_BOOT capability as capabilities aren't supported.");
                #endif
        } else {
                DEBUG("Not dropping CAP_SYS_BOOT or watching utmp.");
                handler->conf->need_utmp_watch = 0;
        }

        if (!attach_block_device(handler->conf)) {
                ERROR("Failed to attach block device.");
                goto out_fini_nonet;
        }

        if (geteuid() == 0 && !lxc_list_empty(&conf->id_map)) {
                /* If the backing store is a device, mount it here and now. */
                if (rootfs_is_blockdev(conf)) {
                        if (unshare(CLONE_NEWNS) < 0) {
                                ERROR("Failed to unshare CLONE_NEWNS.");
                                goto out_fini_nonet;
                        }
                        INFO("Unshared CLONE_NEWNS.");

                        remount_all_slave();
                        if (do_rootfs_setup(conf, name, lxcpath) < 0) {
                                ERROR("Error setting up rootfs mount as root before spawn.");
                                goto out_fini_nonet;
                        }
                        INFO("Set up container rootfs as host root.");
                }
        }

        err = lxc_spawn(handler);
        if (err) {
                ERROR("Failed to spawn container \"%s\".", name);
                goto out_detach_blockdev;
        }

        handler->conf->reboot = 0;

        err = lxc_poll(name, handler);
        if (err) {
                ERROR("LXC mainloop exited with error: %d.", err);
                if (handler->netnsfd >= 0) {
                        close(handler->netnsfd);
                        handler->netnsfd = -1;
                }
                goto out_abort;
        }

        while (waitpid(handler->pid, &status, 0) < 0 && errno == EINTR)
                continue;

        /* If the child process exited but was not signaled, it didn't call
         * reboot. This should mean it was an lxc-execute which simply exited.
         * In any case, treat it as a 'halt'.
         */
        if (WIFSIGNALED(status)) {
                switch(WTERMSIG(status)) {
                case SIGINT: /* halt */
                        DEBUG("Container \"%s\" is halting.", name);
                        break;
                case SIGHUP: /* reboot */
                        DEBUG("Container \"%s\" is rebooting.", name);
                        handler->conf->reboot = 1;
                        break;
                case SIGSYS: /* seccomp */
                        DEBUG("Container \"%s\" violated its seccomp policy.", name);
                        break;
                default:
                        DEBUG("Unknown exit status for container \"%s\" init %d.", name, WTERMSIG(status));
                        break;
                }
        }

        DEBUG("Pushing physical nics back to host namespace");
        lxc_restore_phys_nics_to_netns(handler->netnsfd, handler->conf);

        DEBUG("Tearing down virtual network devices used by container \"%s\".", name);
        removed_all_netdevs = lxc_delete_network(handler);

        if (handler->pinfd >= 0) {
                close(handler->pinfd);
                handler->pinfd = -1;
        }

        lxc_monitor_send_exit_code(name, status, handler->lxcpath);
        err =  lxc_error_set_and_log(handler->pid, status);
out_fini:
        if (!removed_all_netdevs) {
                DEBUG("Failed tearing down network devices used by container. Trying again!");
                removed_all_netdevs = lxc_delete_network(handler);
                if (!removed_all_netdevs)
                        DEBUG("Failed tearing down network devices used by container. Not trying again!");
        }

out_detach_blockdev:
        detach_block_device(handler->conf);

out_fini_nonet:
        lxc_fini(name, handler);
        return err;

out_abort:
        lxc_abort(name, handler);
        goto out_fini;
}

struct start_args {
        char *const *argv;
};

static int start(struct lxc_handler *handler, void* data)
{
        struct start_args *arg = data;

        NOTICE("Exec'ing \"%s\".", arg->argv[0]);

        execvp(arg->argv[0], arg->argv);
        SYSERROR("Failed to exec \"%s\".", arg->argv[0]);
        return 0;
}

static int post_start(struct lxc_handler *handler, void* data)
{
        struct start_args *arg = data;

        NOTICE("Started \"%s\" with pid \"%d\".", arg->argv[0], handler->pid);
        return 0;
}

static struct lxc_operations start_ops = {
        .start = start,
        .post_start = post_start
};

int lxc_start(const char *name, char *const argv[], struct lxc_handler *handler,
              const char *lxcpath, bool backgrounded)
{
        struct start_args start_arg = {
                .argv = argv,
        };

        handler->conf->need_utmp_watch = 1;
        return __lxc_start(name, handler, &start_ops, &start_arg, lxcpath, backgrounded);
}

static void lxc_destroy_container_on_signal(struct lxc_handler *handler,
                                            const char *name)
{
        char destroy[MAXPATHLEN];
        bool bret = true;
        int ret = 0;
        struct lxc_container *c;
        if (handler->conf->rootfs.path && handler->conf->rootfs.mount) {
                bret = do_destroy_container(handler->conf);
                if (!bret) {
                        ERROR("Error destroying rootfs for container \"%s\".", name);
                        return;
                }
        }
        INFO("Destroyed rootfs for container \"%s\".", name);

        ret = snprintf(destroy, MAXPATHLEN, "%s/%s", handler->lxcpath, name);
        if (ret < 0 || ret >= MAXPATHLEN) {
                ERROR("Error destroying directory for container \"%s\".", name);
                return;
        }

        c = lxc_container_new(name, handler->lxcpath);
        if (c) {
                if (container_disk_lock(c)) {
                        INFO("Could not update lxc_snapshots file.");
                        lxc_container_put(c);
                } else {
                        mod_all_rdeps(c, false);
                        container_disk_unlock(c);
                        lxc_container_put(c);
                }
        }

        if (am_unpriv())
                ret = userns_exec_1(handler->conf, lxc_rmdir_onedev_wrapper,
                                    destroy, "lxc_rmdir_onedev_wrapper");
        else
                ret = lxc_rmdir_onedev(destroy, NULL);

        if (ret < 0) {
                ERROR("Error destroying directory for container \"%s\".", name);
                return;
        }
        INFO("Destroyed directory for container \"%s\".", name);
}

static int lxc_rmdir_onedev_wrapper(void *data)
{
        char *arg = (char *) data;
        return lxc_rmdir_onedev(arg, NULL);
}

static bool do_destroy_container(struct lxc_conf *conf) {
        if (am_unpriv()) {
                if (userns_exec_1(conf, storage_destroy_wrapper, conf,
                                  "storage_destroy_wrapper") < 0)
                        return false;

                return true;
        }

        return storage_destroy(conf);
}