/*
 * vircgroupv2.c: methods for cgroups v2 backend
 *
 * Copyright (C) 2018 Red Hat, Inc.
 *
 * 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, see
 * <http://www.gnu.org/licenses/>.
 */
#include <config.h>

#ifdef __linux__
# include <mntent.h>
#endif /* __linux__ */

#include "internal.h"

#define __VIR_CGROUP_ALLOW_INCLUDE_PRIV_H__
#include "vircgrouppriv.h"
#undef __VIR_CGROUP_ALLOW_INCLUDE_PRIV_H__

#include "vircgroup.h"
#include "vircgroupbackend.h"
#include "vircgroupv2.h"
#include "virfile.h"
#include "virlog.h"
#include "virstring.h"
#include "virsystemd.h"

VIR_LOG_INIT("util.cgroup");

#define VIR_FROM_THIS VIR_FROM_CGROUP

VIR_ENUM_DECL(virCgroupV2Controller);
VIR_ENUM_IMPL(virCgroupV2Controller, VIR_CGROUP_CONTROLLER_LAST,
              "cpu", "cpuacct", "cpuset", "memory", "devices",
              "freezer", "io", "net_cls", "perf_event", "name=systemd");

#ifdef __linux__

/* We're looking for one 'cgroup2' fs mount which has some
 * controllers enabled. */
static bool
virCgroupV2Available(void)
{
    bool ret = false;
    FILE *mounts = NULL;
    struct mntent entry;
    char buf[CGROUP_MAX_VAL];

    if (!(mounts = fopen("/proc/mounts", "r")))
        return false;

    while (getmntent_r(mounts, &entry, buf, sizeof(buf)) != NULL) {
        VIR_AUTOFREE(char *) contFile = NULL;
        VIR_AUTOFREE(char *) contStr = NULL;

        if (STRNEQ(entry.mnt_type, "cgroup2"))
            continue;

        /* Systemd uses cgroup v2 for process tracking but no controller is
         * available. We should consider this configuration as cgroup v2 is
         * not available. */
        if (virAsprintf(&contFile, "%s/cgroup.controllers", entry.mnt_dir) < 0)
            goto cleanup;

        if (virFileReadAll(contFile, 1024 * 1024, &contStr) < 0)
            goto cleanup;

        if (STREQ(contStr, ""))
            continue;

        ret = true;
        break;
    }

 cleanup:
    VIR_FORCE_FCLOSE(mounts);
    return ret;
}


static bool
virCgroupV2ValidateMachineGroup(virCgroupPtr group,
                                const char *name ATTRIBUTE_UNUSED,
                                const char *drivername,
                                const char *machinename)
{
    VIR_AUTOFREE(char *) partmachinename = NULL;
    VIR_AUTOFREE(char *) scopename = NULL;
    char *tmp;

    if (virAsprintf(&partmachinename, "%s.libvirt-%s", machinename,
                    drivername) < 0) {
        return false;
    }

    if (virCgroupPartitionEscape(&partmachinename) < 0)
        return false;

    if (!(scopename = virSystemdMakeScopeName(machinename, drivername,
                                              false))) {
        return false;
    }

    if (virCgroupPartitionEscape(&scopename) < 0)
        return false;

    if (!(tmp = strrchr(group->unified.placement, '/')))
        return false;
    tmp++;

    if (STRNEQ(tmp, partmachinename) &&
        STRNEQ(tmp, scopename)) {
        VIR_DEBUG("Name '%s' for unified does not match '%s' or '%s'",
                  tmp, partmachinename, scopename);
        return false;
    }

    return true;
}


virCgroupBackend virCgroupV2Backend = {
    .type = VIR_CGROUP_BACKEND_TYPE_V2,

    .available = virCgroupV2Available,
    .validateMachineGroup = virCgroupV2ValidateMachineGroup,
};


void
virCgroupV2Register(void)
{
    virCgroupBackendRegister(&virCgroupV2Backend);
}

#else /* !__linux__ */

void
virCgroupV2Register(void)
{
    VIR_INFO("Control groups not supported on this platform");
}

#endif /* !__linux__ */