/***
  This file is part of eudev, forked from systemd.

  Copyright 2011 Lennart Poettering

  systemd 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.

  systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
***/

#include <string.h>
#include <errno.h>
#include <unistd.h>

#include "util.h"
#include "virt.h"
#include "fileio.h"

int detect_container(const char **id) {

        static thread_local int cached_found = -1;
        static thread_local const char *cached_id = NULL;

        _cleanup_free_ char *m = NULL;
        const char *_id = NULL, *e = NULL;
        int r;

        if (_likely_(cached_found >= 0)) {

                if (id)
                        *id = cached_id;

                return cached_found;
        }

        /* /proc/vz exists in container and outside of the container,
         * /proc/bc only outside of the container. */
        if (access("/proc/vz", F_OK) >= 0 &&
            access("/proc/bc", F_OK) < 0) {
                _id = "openvz";
                r = 1;
                goto finish;
        }

        if (getpid() == 1) {
                /* If we are PID 1 we can just check our own
                 * environment variable */

                e = getenv("container");
                if (isempty(e)) {
                        r = 0;
                        goto finish;
                }
        } else {

                /* Otherwise, PID 1 dropped this information into a
                 * file in /run. This is better than accessing
                 * /proc/1/environ, since we don't need CAP_SYS_PTRACE
                 * for that. */

                r = read_one_line_file("/run/systemd/container", &m);
                if (r == -ENOENT) {
                        r = 0;
                        goto finish;
                }
                if (r < 0)
                        return r;

                e = m;
        }

        /* We only recognize a selected few here, since we want to
         * enforce a redacted namespace */
        if (streq(e, "lxc"))
                _id ="lxc";
        else if (streq(e, "lxc-libvirt"))
                _id = "lxc-libvirt";
        else if (streq(e, "systemd-nspawn"))
                _id = "systemd-nspawn";
        else if (streq(e, "docker"))
                _id = "docker";
        else
                _id = "other";

        r = 1;

finish:
        cached_found = r;

        cached_id = _id;
        if (id)
                *id = _id;

        return r;
}