start: resolve clone flags

[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>
 * Serge Hallyn <serge@hallyn.com>
 * Christian Brauner <christian.brauner@ubuntu.com>
 *
 * 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

#if !HAVE_DECL_PR_CAPBSET_DROP
#define PR_CAPBSET_DROP 24
#endif

#if !HAVE_DECL_PR_SET_NO_NEW_PRIVS
#define PR_SET_NO_NEW_PRIVS 38
#endif

#if !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 "confile_utils.h"
#include "console.h"
#include "error.h"
#include "list.h"
#include "log.h"
#include "lxccontainer.h"
#include "lxclock.h"
#include "lxcseccomp.h"
#include "mainloop.h"
#include "monitor.h"
#include "namespace.h"
#include "network.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_handler *handler);
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;

                DEBUG("Preserved %s namespace via fd %d", ns_info[i].proc_name, ns_fd[i]);
        }

        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 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))) {
                struct lxc_list *cur;
                bool matched = false;

                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;

                /* Keep state clients that wait on reboots. */
                if (conf) {
                        lxc_list_for_each(cur, &conf->state_clients) {
                                struct lxc_state_client *client = cur->elem;

                                if (client->clientfd != fd)
                                        continue;

                                matched = true;
                                break;
                        }
                }

                if (matched)
                        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)
{
        int ret, sig;
        sigset_t mask;
        int signals[] = {SIGBUS, SIGILL, SIGSEGV, SIGWINCH};

        /* Block everything except serious error signals. */
        ret = sigfillset(&mask);
        if (ret < 0)
                return -EBADF;

        for (sig = 0; sig < (sizeof(signals) / sizeof(signals[0])); sig++) {
                ret = sigdelset(&mask, signals[sig]);
                if (ret < 0)
                        return -EBADF;
        }

        ret = sigprocmask(SIG_BLOCK, &mask, oldmask);
        if (ret < 0) {
                SYSERROR("Failed to set signal mask");
                return -EBADF;
        }

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

        TRACE("Created signal file descriptor %d", ret);

        return ret;
}

static int signal_handler(int fd, uint32_t events, void *data,
                          struct lxc_epoll_descr *descr)
{
        int ret;
        siginfo_t info;
        struct signalfd_siginfo siginfo;
        struct lxc_handler *hdlr = data;

        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, hdlr->pid, &info, WEXITED | WNOWAIT | WNOHANG);
        if (ret == 0 && info.si_pid == hdlr->pid)
                hdlr->init_died = true;

        /* Try to figure out a reasonable exit status to report. */
        if (hdlr->init_died) {
                switch (info.si_code) {
                case CLD_EXITED:
                        hdlr->exit_status = info.si_status << 8;
                        break;
                case CLD_KILLED:
                case CLD_DUMPED:
                case CLD_STOPPED:
                        hdlr->exit_status = info.si_status << 8 | 0x7f;
                        break;
                case CLD_CONTINUED:
                        /* Huh? The waitid() told us it's dead *and* continued? */
                        WARN("Init %d dead and continued?", hdlr->pid);
                        hdlr->exit_status = 1;
                        break;
                default:
                        ERROR("Unknown si_code: %d", hdlr->init_died);
                        hdlr->exit_status = 1;
                }
        }

        if (siginfo.ssi_signo == SIGHUP) {
                kill(hdlr->pid, SIGTERM);
                INFO("Killing %d since terminal hung up", hdlr->pid);
                return hdlr->init_died ? LXC_MAINLOOP_CLOSE : 0;
        }

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

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

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

        DEBUG("Container init process %d exited.", hdlr->pid);
        return LXC_MAINLOOP_CLOSE;
}

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 lxc_state_client *client;
        struct lxc_msg msg = {.type = lxc_msg_state, .value = state};

        process_lock();
        if (state == THAWED)
                handler->state = RUNNING;
        else
                handler->state = state;

        TRACE("Set container state to %s", lxc_state2str(state));

        if (lxc_list_empty(&handler->conf->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->conf->state_clients, next) {
                client = cur->elem;

                if (client->states[state] == 0) {
                        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("%s - Failed to send message to client",
                              strerror(errno));
                }

                /* 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 ret;
        bool has_console = true;
        struct lxc_epoll_descr descr, descr_console;

        if (handler->conf->console.path && !strcmp(handler->conf->console.path, "none"))
                has_console = false;

        ret = lxc_mainloop_open(&descr);
        if (ret < 0) {
                ERROR("Failed to create mainloop");
                goto out_sigfd;
        }

        if (has_console) {
                ret = lxc_mainloop_open(&descr_console);
                if (ret < 0) {
                        ERROR("Failed to create console mainloop");
                        goto out_mainloop;
                }
        }

        ret = lxc_mainloop_add_handler(&descr, handler->sigfd, signal_handler, handler);
        if (ret < 0) {
                ERROR("Failed to add signal handler for %d to mainloop", handler->sigfd);
                goto out_mainloop_console;
        }

        if (has_console) {
                struct lxc_console *console = &handler->conf->console;

                ret = lxc_console_mainloop_add(&descr, console);
                if (ret < 0) {
                        ERROR("Failed to add console handlers to mainloop");
                        goto out_mainloop_console;
                }

                ret = lxc_console_mainloop_add(&descr_console, console);
                if (ret < 0) {
                        ERROR("Failed to add console handlers to console mainloop");
                        goto out_mainloop_console;
                }
        }

        ret = lxc_cmd_mainloop_add(name, &descr, handler);
        if (ret < 0) {
                ERROR("Failed to add command handler to mainloop");
                goto out_mainloop_console;
        }

        TRACE("Mainloop is ready");

        ret = lxc_mainloop(&descr, -1);
        close(descr.epfd);
        descr.epfd = -EBADF;
        if (ret < 0 || !handler->init_died)
                goto out_mainloop_console;

        if (has_console)
                ret = lxc_mainloop(&descr_console, 0);

out_mainloop_console:
        if (has_console) {
                lxc_mainloop_close(&descr_console);
                TRACE("Closed console mainloop");
        }

out_mainloop:
        lxc_mainloop_close(&descr);
        TRACE("Closed mainloop");

out_sigfd:
        close(handler->sigfd);
        TRACE("Closed signal file descriptor %d", handler->sigfd);
        handler->sigfd = -EBADF;

        return ret;
}

void lxc_zero_handler(struct lxc_handler *handler)
{
        int i;

        memset(handler, 0, sizeof(struct lxc_handler));

        handler->clone_flags = -1;

        handler->pinfd = -1;

        handler->sigfd = -1;

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

        handler->data_sock[0] = -1;
        handler->data_sock[1] = -1;

        handler->state_socket_pair[0] = -1;
        handler->state_socket_pair[1] = -1;

        handler->sync_sock[0] = -1;
        handler->sync_sock[1] = -1;
}

static void lxc_put_nsfds(struct lxc_handler *handler)
{
        int i;

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

                close(handler->nsfd[i]);
                handler->nsfd[i] = -EBADF;
        }
}

void lxc_free_handler(struct lxc_handler *handler)
{
        if (handler->pinfd >= 0)
                close(handler->pinfd);

        if (handler->sigfd >= 0)
                close(handler->sigfd);

        lxc_put_nsfds(handler);

        if (handler->conf && handler->conf->reboot == 0)
                if (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]);

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

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));

        /* Note that am_host_unpriv() checks the effective uid. We probably don't
         * care if we are real root only if we are running as root so this
         * should be fine.
         */
        handler->am_root = !am_host_unpriv();
        handler->data_sock[0] = handler->data_sock[1] = -1;
        handler->conf = conf;
        handler->lxcpath = lxcpath;
        handler->pinfd = -1;
        handler->sigfd = -EBADF;
        handler->init_died = false;
        handler->state_socket_pair[0] = handler->state_socket_pair[1] = -1;
        if (handler->conf->reboot == 0)
                lxc_list_init(&handler->conf->state_clients);

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

        handler->name = name;

        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 (handler->conf->reboot == 0) {
                handler->conf->maincmd_fd = lxc_cmd_init(name, lxcpath, "command");
                if (handler->conf->maincmd_fd < 0) {
                        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)
{
        int ret;
        const char *loglevel;
        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.");

        loglevel = lxc_log_priority_to_string(lxc_log_get_level());
        if (setenv("LXC_LOG_LEVEL", loglevel, 1))
                SYSERROR("Failed to set environment variable LXC_LOG_LEVEL=%s", loglevel);

        if (conf->hooks_version == 0)
                ret = setenv("LXC_HOOK_VERSION", "0", 1);
        else
                ret = setenv("LXC_HOOK_VERSION", "1", 1);
        if (ret < 0)
                SYSERROR("Failed to set environment variable LXC_HOOK_VERSION=%u", conf->hooks_version);
        /* End of environment variable setup for hooks. */

        TRACE("set environment variables");

        if (run_lxc_hooks(name, "pre-start", conf, 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. */
        ret = lxc_console_create(conf);
        if (ret < 0) {
                ERROR("Failed to create console");
                goto out_restore_sigmask;
        }
        TRACE("Created console");

        ret = lxc_pty_map_ids(conf, &conf->console);
        if (ret < 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;
        pid_t self;
        struct lxc_list *cur, *next;
        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);

        self = lxc_raw_getpid();
        for (i = 0; i < LXC_NS_MAX; i++) {
                if (handler->nsfd[i] < 0)
                        continue;

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

                if (handler->conf->hooks_version == 0) {
                        namespace_count++;
                        continue;
                }

                rc = setenv(ns_info[i].env_name, namespaces[namespace_count], 1);
                if (rc < 0)
                        SYSERROR("Failed to set environment variable %s=%s",
                                 ns_info[i].env_name, namespaces[namespace_count]);
                else
                        TRACE("Set environment variable %s=%s",
                              ns_info[i].env_name, namespaces[namespace_count]);

                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 (handler->conf->hooks_version == 0)
                rc = run_lxc_hooks(name, "stop", handler->conf, namespaces);
        else
                rc = run_lxc_hooks(name, "stop", handler->conf, NULL);

        while (namespace_count--)
                free(namespaces[namespace_count]);

        cgroup_destroy(handler);

        if (handler->conf->reboot == 0) {
                /* For all new state clients simply close the command socket.
                 * This will inform all state clients that the container is
                 * STOPPED and also prevents a race between a open()/close() on
                 * the command socket causing a new process to get ECONNREFUSED
                 * because we haven't yet closed the command socket.
                 */
                close(handler->conf->maincmd_fd);
                handler->conf->maincmd_fd = -1;
                TRACE("Closed command socket");

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

                /* The command socket is closed so no one can acces the command
                 * socket anymore so there's no need to lock it.
                 */
                handler->state = STOPPED;
                TRACE("Set container state to \"STOPPED\"");
        } else {
                lxc_set_state(name, handler, STOPPED);
        }

        if (run_lxc_hooks(name, "post-stop", handler->conf, 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);

        /* 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->conf->state_clients, next) {
                struct lxc_state_client *client = cur->elem;

                /* Keep state clients that want to be notified about reboots. */
                if ((handler->conf->reboot > 0) && (client->states[RUNNING] == 2))
                        continue;

                /* close state client socket */
                close(client->clientfd);
                lxc_list_del(cur);
                free(cur->elem);
                free(cur);
        }

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

        lxc_free_handler(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) {
                ;
        }
}

static int lxc_set_death_signal(int signal)
{
        int ret;
        pid_t ppid;

        ret = prctl(PR_SET_PDEATHSIG, signal, 0, 0, 0);

        /* Check whether we have been orphaned. */
        ppid = (pid_t)syscall(SYS_getppid);
        if (ppid == 1) {
                pid_t self;

                self = lxc_raw_getpid();
                ret = kill(self, SIGKILL);
                if (ret < 0)
                        return -1;
        }

        if (ret < 0) {
                SYSERROR("Failed to set PR_SET_PDEATHSIG to %d", signal);
                return -1;
        }

        return 0;
}

static int do_start(void *data)
{
        int ret;
        struct lxc_list *iterator;
        char path[PATH_MAX];
        struct lxc_handler *handler = data;
        bool have_cap_setgid;
        uid_t new_uid;
        gid_t new_gid;
        int devnull_fd = -1;

        lxc_sync_fini_parent(handler);

        /* 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.
         */
        ret = lxc_set_death_signal(SIGKILL);
        if (ret < 0) {
                SYSERROR("Failed to set PR_SET_PDEATHSIG to SIGKILL");
                goto out_warn_father;
        }

        ret = sigprocmask(SIG_SETMASK, &handler->oldmask, NULL);
        if (ret < 0) {
                SYSERROR("Failed to set signal mask");
                goto out_warn_father;
        }

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

        ret = lxc_sync_wait_parent(handler, LXC_SYNC_STARTUP);
        if (ret < 0)
                goto out_warn_father;

        /* 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 (lxc_network_recv_veth_names_from_parent(handler) < 0) {
                ERROR("Failed to receive veth names from parent");
                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)) {
                uid_t nsuid = (handler->conf->root_nsuid_map != NULL)
                                  ? 0
                                  : handler->conf->init_uid;
                gid_t nsgid = (handler->conf->root_nsgid_map != NULL)
                                  ? 0
                                  : handler->conf->init_gid;

                ret = lxc_switch_uid_gid(nsuid, nsgid);
                if (ret < 0)
                        goto out_warn_father;

                /* Drop groups only after we switched to a valid gid in the new
                 * user namespace.
                 */
                ret = lxc_setgroups(0, NULL);
                if (ret < 0 && (handler->am_root || errno != EPERM))
                        goto out_warn_father;

                if (!handler->am_root) {
                        ret = prctl(PR_SET_DUMPABLE, 1, 0, 0, 0);
                        if (ret < 0)
                                goto out_warn_father;
                }

                /* set{g,u}id() clears deathsignal */
                ret = lxc_set_death_signal(SIGKILL);
                if (ret < 0) {
                        SYSERROR("Failed to set PR_SET_PDEATHSIG to SIGKILL");
                        goto out_warn_father;
                }
        }

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

        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 (handler->clone_flags & CLONE_NEWCGROUP) {
                if (unshare(CLONE_NEWCGROUP) < 0) {
                        INFO("Failed to unshare CLONE_NEWCGROUP.");
                        goto out_warn_father;
                }
                INFO("Unshared CLONE_NEWCGROUP.");
        }

        /* Add the requested environment variables to the current environment to
         * allow them to be used by the various hooks, such as the start hook
         * above.
         */
        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;
                }
        }

        /* Setup the container, ip, names, utsname, ... */
        ret = lxc_setup(handler);
        close(handler->data_sock[1]);
        close(handler->data_sock[0]);
        if (ret < 0) {
                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 (handler->backgrounded || handler->conf->is_execute == 0)
                         ret = set_stdfds(handler->conf->console.slave);
                 else
                         ret = lxc_console_set_stdfds(handler->conf->console.slave);
                 if (ret < 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, NULL)) {
                ERROR("Failed to run lxc.hook.start for container \"%s\".", handler->name);
                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 (handler->conf->init_cwd && chdir(handler->conf->init_cwd)) {
                SYSERROR("Could not change directory to \"%s\"", handler->conf->init_cwd);
                goto out_warn_father;
        }

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

        /* Reset the environment variables the user requested in a clear
         * environment.
         */
        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;
                }
        }

        /* The container has been setup. We can now switch to an unprivileged
         * uid/gid.
         */
        new_uid = handler->conf->init_uid;
        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;

        /* 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 lxc_recv_ttys_from_child(struct lxc_handler *handler)
{
        int i;
        struct lxc_pty_info *pty_info;
        int ret = -1;
        int sock = handler->data_sock[1];
        struct lxc_conf *conf = handler->conf;
        struct lxc_tty_info *tty_info = &conf->tty_info;

        if (!conf->tty)
                return 0;

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

        for (i = 0; i < conf->tty; i++) {
                int ttyfds[2];

                ret = lxc_abstract_unix_recv_fds(sock, ttyfds, 2, NULL, 0);
                if (ret < 0)
                        break;

                pty_info = &tty_info->pty_info[i];
                pty_info->busy = 0;
                pty_info->master = ttyfds[0];
                pty_info->slave = ttyfds[1];
                TRACE("Received pty with master fd %d and slave fd %d from "
                      "parent", pty_info->master, pty_info->slave);
        }
        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);

        tty_info->nbtty = conf->tty;

        return ret;
}

int resolve_clone_flags(struct lxc_handler *handler)
{
        int i;
        struct lxc_conf *conf = handler->conf;

        for (i = 0; i < LXC_NS_MAX; i++) {
                if (conf->ns_keep != 0) {
                        if ((conf->ns_keep & ns_info[i].clone_flag) == 0)
                                handler->clone_flags |= ns_info[i].clone_flag;
                } else if (conf->ns_clone != 0) {
                        if ((conf->ns_clone & ns_info[i].clone_flag) > 0)
                                handler->clone_flags |= ns_info[i].clone_flag;
                } else {
                        if (i == LXC_NS_USER && lxc_list_empty(&handler->conf->id_map))
                                continue;

                        if (i == LXC_NS_NET && lxc_requests_empty_network(handler))
                                continue;

                        handler->clone_flags |= ns_info[i].clone_flag;
                }

                if (!conf->ns_share[i])
                        continue;

                handler->clone_flags &= ~ns_info[i].clone_flag;
                TRACE("Sharing %s namespace", ns_info[i].proc_name);
        }

        return 0;
}

/* Note that this function is used with clone(CLONE_VM). Some glibc versions
 * used to reset the pid/tid to -1 when CLONE_VM was used without CLONE_THREAD.
 * But since the memory between parent and child is shared on CLONE_VM this
 * would invalidate the getpid() cache that glibc used to maintain and so
 * getpid() in the child would return the parent's pid. This is all fixed in
 * newer glibc versions where the getpid() cache is removed and the pid/tid is
 * not reset anymore.
 * However, if for whatever reason you - dear commiter - somehow need to get the
 * pid of the dummy intermediate process for do_share_ns() you need to call
 * lxc_raw_getpid(). The next lxc_raw_clone() call does not employ CLONE_VM and
 * will be fine.
 */
static inline int do_share_ns(void *arg)
{
        int i, flags, ret;
        struct lxc_handler *handler = arg;

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

                ret = setns(handler->nsfd[i], 0);
                if (ret < 0)
                        return -1;

                DEBUG("Inherited %s namespace", ns_info[i].proc_name);
        }

        flags = handler->on_clone_flags;
        flags |= CLONE_PARENT;
        handler->pid = lxc_raw_clone_cb(do_start, handler, flags);
        if (handler->pid < 0)
                return -1;

        return 0;
}

/* 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 i, ret;
        char pidstr[20];
        bool wants_to_map_ids;
        struct lxc_list *id_map;
        const char *name = handler->name;
        const char *lxcpath = handler->lxcpath;
        bool cgroups_connected = false, share_ns = false;
        struct lxc_conf *conf = handler->conf;

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

        for (i = 0; i < LXC_NS_MAX; i++) {
                if (!conf->ns_share[i])
                        continue;

                handler->nsfd[i] = lxc_inherit_namespace(conf->ns_share[i], lxcpath, ns_info[i].proc_name);
                if (handler->nsfd[i] < 0)
                        return -1;

                share_ns = true;
        }

        if (lxc_sync_init(handler))
                return -1;

        ret = socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0,
                         handler->data_sock);
        if (ret < 0) {
                lxc_sync_fini(handler);
                return -1;
        }

        ret = resolve_clone_flags(handler);
        if (ret < 0) {
                lxc_sync_fini(handler);
                return -1;
        }

        if (handler->clone_flags & CLONE_NEWNET) {
                if (!lxc_list_empty(&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_create_network_priv(handler)) {
                                ERROR("Failed to create the network.");
                                lxc_sync_fini(handler);
                                return -1;
                        }
                }
        }

        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(conf->rootfs.path);
                if (handler->pinfd == -1)
                        INFO("Failed to pin the rootfs for container \"%s\".", handler->name);
        }

        /* Create a process in a new set of namespaces. */
        handler->on_clone_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.
                 */
                handler->on_clone_flags &= ~CLONE_NEWNET;
        }
        /* The cgroup namespace gets unshare()ed not clone()ed. */
        handler->on_clone_flags &= ~CLONE_NEWCGROUP;

        if (share_ns) {
                pid_t attacher_pid;

                attacher_pid = lxc_clone(do_share_ns, handler, CLONE_VFORK | CLONE_VM | CLONE_FILES);
                if (attacher_pid < 0) {
                        SYSERROR(LXC_CLONE_ERROR);
                        goto out_delete_net;
                }

                ret = wait_for_pid(attacher_pid);
                if (ret < 0) {
                        SYSERROR("Intermediate process failed");
                        goto out_delete_net;
                }
        } else {
                handler->pid = lxc_raw_clone_cb(do_start, handler, handler->on_clone_flags);
        }
        if (handler->pid < 0) {
                SYSERROR(LXC_CLONE_ERROR);
                goto out_delete_net;
        }
        TRACE("Cloned child process %d", handler->pid);

        for (i = 0; i < LXC_NS_MAX; i++)
                if (handler->on_clone_flags & ns_info[i].clone_flag)
                        INFO("Cloned %s", ns_info[i].flag_name);

        if (!preserve_ns(handler->nsfd, handler->on_clone_flags, handler->pid)) {
                ERROR("Failed to preserve cloned namespaces for lxc.hook.stop");
                goto out_delete_net;
        }

        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) {
                if (!handler->conf->ns_share[LXC_NS_USER] ||
                    (handler->conf->ns_keep & CLONE_NEWUSER) > 0) {
                        ret = lxc_map_ids(id_map, handler->pid);
                        if (ret < 0) {
                                ERROR("Failed to set up id mapping.");
                                goto out_delete_net;
                        }
                }
        }

        if (lxc_sync_wake_child(handler, LXC_SYNC_STARTUP))
                goto out_delete_net;

        if (lxc_sync_wait_child(handler, LXC_SYNC_CONFIGURE))
                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;

        /* Now we're ready to preserve the network namespace */
        ret = lxc_preserve_ns(handler->pid, "net");
        if (ret < 0) {
                ERROR("%s - Failed to preserve net namespace", strerror(errno));
                goto out_delete_net;
        }
        handler->nsfd[LXC_NS_NET] = ret;
        DEBUG("Preserved net namespace via fd %d", ret);

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

                if (lxc_create_network_unpriv(handler->lxcpath, handler->name,
                                              &conf->network,
                                              handler->pid)) {
                        ERROR("Failed to create the configured network.");
                        goto out_delete_net;
                }
        }

        if (lxc_network_send_veth_names_to_child(handler) < 0) {
                ERROR("Failed to send veth names to child");
                goto out_delete_net;
        }

        if (!lxc_list_empty(&conf->procs)) {
                ret = setup_proc_filesystem(&conf->procs, handler->pid);
                if (ret < 0)
                        goto out_delete_net;
        }

        /* 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(&conf->limits) && setup_resource_limits(&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;

        if (handler->clone_flags & CLONE_NEWCGROUP) {
                /* Now we're ready to preserve the cgroup namespace */
                ret = lxc_preserve_ns(handler->pid, "cgroup");
                if (ret < 0) {
                        ERROR("%s - Failed to preserve cgroup namespace", strerror(errno));
                        goto out_delete_net;
                }
                handler->nsfd[LXC_NS_CGROUP] = ret;
                DEBUG("Preserved cgroup namespace via fd %d", ret);
        }

        snprintf(pidstr, 20, "%d", handler->pid);
        if (setenv("LXC_PID", pidstr, 1))
                SYSERROR("Failed to set environment variable: LXC_PID=%s.", pidstr);

        /* Run any host-side start hooks */
        if (run_lxc_hooks(name, "start-host", conf, NULL)) {
                ERROR("Failed to run lxc.hook.start-host for container \"%s\".", name);
                return -1;
        }

        /* Tell the child to complete its initialization and wait for it to exec
         * or return an error. (The child will never return
         * LXC_SYNC_READY_START+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_READY_START))
                return -1;

        if (lxc_network_recv_name_and_ifindex_from_child(handler) < 0) {
                ERROR("Failed to receive names and ifindices for network "
                      "devices from child");
                goto out_delete_net;
        }

        /* Now all networks are created, network devices are moved into place,
         * and the correct names and ifindeces in the respective namespaces have
         * been recorded. The corresponding structs have now all been filled. So
         * log them for debugging purposes.
         */
        lxc_log_configured_netdevs(conf);

        /* 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);

        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;
        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;

        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;
        }
        /* close parent side of data socket */
        close(handler->data_sock[0]);
        handler->data_sock[0] = -1;
        close(handler->data_sock[1]);
        handler->data_sock[1] = -1;

        handler->conf->reboot = 0;

        err = lxc_poll(name, handler);
        if (err) {
                ERROR("LXC mainloop exited with error: %d.", err);
                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;
                }
        }

        err = lxc_restore_phys_nics_to_netns(handler);
        if (err < 0)
                ERROR("Failed to move physical network devices back to parent "
                      "network namespace");

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

        lxc_monitor_send_exit_code(name, status, handler->lxcpath);
        lxc_error_set_and_log(handler->pid, status);

out_fini:
        lxc_delete_network(handler);

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,
        };

        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);
                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 (!handler->am_root)
                ret = userns_exec_full(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_handler *handler) {
        int ret;

        if (!handler->am_root) {
                ret = userns_exec_full(handler->conf, storage_destroy_wrapper,
                                       handler->conf, "storage_destroy_wrapper");
                if (ret < 0)
                        return false;

                return true;
        }

        return storage_destroy(handler->conf);
}