/*
 * storage_backend_gluster.c: storage backend for Gluster handling
 *
 * Copyright (C) 2013 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>

#include <glusterfs/api/glfs.h>

#include "storage_backend_gluster.h"
#include "storage_conf.h"
#include "viralloc.h"
#include "virerror.h"
#include "virlog.h"
#include "virstoragefile.h"
#include "virstring.h"
#include "viruri.h"

#define VIR_FROM_THIS VIR_FROM_STORAGE

struct _virStorageBackendGlusterState {
    glfs_t *vol;

    /* Accept the same URIs as qemu's block/gluster.c:
     * gluster[+transport]://[server[:port]]/vol/[dir/]image[?socket=...] */
    virURI *uri;

    char *volname; /* vol from URI, no '/' */
    char *dir; /* dir from URI, or "/"; always starts and ends in '/' */
};

typedef struct _virStorageBackendGlusterState virStorageBackendGlusterState;
typedef virStorageBackendGlusterState *virStorageBackendGlusterStatePtr;

static void
virStorageBackendGlusterClose(virStorageBackendGlusterStatePtr state)
{
    if (!state)
        return;

    /* Yuck - glusterfs-api-3.4.1 appears to always return -1 for
     * glfs_fini, with errno containing random data, so there's no way
     * to tell if it succeeded. 3.4.2 is supposed to fix this.*/
    if (state->vol && glfs_fini(state->vol) < 0)
        VIR_DEBUG("shutdown of gluster volume %s failed with errno %d",
                  state->volname, errno);

    virURIFree(state->uri);
    VIR_FREE(state->volname);
    VIR_FREE(state->dir);
    VIR_FREE(state);
}

static virStorageBackendGlusterStatePtr
virStorageBackendGlusterOpen(virStoragePoolObjPtr pool)
{
    virStorageBackendGlusterStatePtr ret = NULL;
    const char *name = pool->def->source.name;
    const char *dir = pool->def->source.dir;
    bool trailing_slash = true;

    /* Volume name must not contain '/'; optional path allows use of a
     * subdirectory within the volume name.  */
    if (strchr(name, '/')) {
        virReportError(VIR_ERR_XML_ERROR,
                       _("gluster pool name '%s' must not contain /"),
                       name);
        return NULL;
    }
    if (dir) {
        if (*dir != '/') {
            virReportError(VIR_ERR_XML_ERROR,
                           _("gluster pool path '%s' must start with /"),
                           dir);
            return NULL;
        }
        if (strchr(dir, '\0')[-1] != '/')
            trailing_slash = false;
    }

    if (VIR_ALLOC(ret) < 0)
        return NULL;

    if (VIR_STRDUP(ret->volname, name) < 0)
        goto error;
    if (virAsprintf(&ret->dir, "%s%s", dir ? dir : "/",
                    trailing_slash ? "" : "/") < 0)
        goto error;

    /* FIXME: Currently hard-coded to tcp transport; XML needs to be
     * extended to allow alternate transport */
    if (VIR_ALLOC(ret->uri) < 0)
        goto error;
    if (VIR_STRDUP(ret->uri->scheme, "gluster") < 0)
        goto error;
    if (VIR_STRDUP(ret->uri->server, pool->def->source.hosts[0].name) < 0)
        goto error;
    if (virAsprintf(&ret->uri->path, "/%s%s", ret->volname, ret->dir) < 0)
        goto error;
    ret->uri->port = pool->def->source.hosts[0].port;

    /* Actually connect to glfs */
    if (!(ret->vol = glfs_new(ret->volname))) {
        virReportOOMError();
        goto error;
    }

    if (glfs_set_volfile_server(ret->vol, "tcp",
                                ret->uri->server, ret->uri->port) < 0 ||
        glfs_init(ret->vol) < 0) {
        char *uri = virURIFormat(ret->uri);

        virReportSystemError(errno, _("failed to connect to %s"),
                             NULLSTR(uri));
        VIR_FREE(uri);
        goto error;
    }

    if (glfs_chdir(ret->vol, ret->dir) < 0) {
        virReportSystemError(errno,
                             _("failed to change to directory '%s' in '%s'"),
                             ret->dir, ret->volname);
        goto error;
    }

    return ret;

error:
    virStorageBackendGlusterClose(ret);
    return NULL;
}


/* Populate *volptr for the given name and stat information, or leave
 * it NULL if the entry should be skipped (such as ".").  Return 0 on
 * success, -1 on failure. */
static int
virStorageBackendGlusterRefreshVol(virStorageBackendGlusterStatePtr state,
                                   const char *name,
                                   struct stat *st,
                                   virStorageVolDefPtr *volptr)
{
    char *tmp;
    int ret = -1;
    virStorageVolDefPtr vol = NULL;

    *volptr = NULL;

    /* Silently skip '.' and '..'.  */
    if (STREQ(name, ".") || STREQ(name, ".."))
        return 0;
    /* FIXME: support directories.  For now, silently skip them.  */
    if (S_ISDIR(st->st_mode))
        return 0;

    if (VIR_ALLOC(vol) < 0)
        goto cleanup;
    if (VIR_STRDUP(vol->name, name) < 0)
        goto cleanup;
    if (virAsprintf(&vol->key, "%s%s%s", state->volname, state->dir,
                    vol->name) < 0)
        goto cleanup;

    vol->type = VIR_STORAGE_VOL_NETWORK;
    tmp = state->uri->path;
    state->uri->path = vol->key;
    if (!(vol->target.path = virURIFormat(state->uri))) {
        state->uri->path = tmp;
        goto cleanup;
    }
    state->uri->path = tmp;

    /* FIXME - must open files to determine if they are non-raw */
    vol->target.format = VIR_STORAGE_FILE_RAW;
    vol->capacity = vol->allocation = st->st_size;

    *volptr = vol;
    vol = NULL;
    ret = 0;
cleanup:
    virStorageVolDefFree(vol);
    return ret;
}

static int
virStorageBackendGlusterRefreshPool(virConnectPtr conn ATTRIBUTE_UNUSED,
                                    virStoragePoolObjPtr pool)
{
    int ret = -1;
    virStorageBackendGlusterStatePtr state = NULL;
    struct {
        struct dirent ent;
        /* See comment below about readdir_r needing padding */
        char padding[MAX(1, 256 - (int) (sizeof(struct dirent)
                                         - offsetof(struct dirent, d_name)))];
    } de;
    struct dirent *ent;
    glfs_fd_t *dir = NULL;
    struct stat st;
    struct statvfs sb;

    if (!(state = virStorageBackendGlusterOpen(pool)))
        goto cleanup;

    /* Why oh why did glfs 3.4 decide to expose only readdir_r rather
     * than readdir?  POSIX admits that readdir_r is inherently a
     * flawed design, because systems are not required to define
     * NAME_MAX: http://austingroupbugs.net/view.php?id=696
     * http://womble.decadent.org.uk/readdir_r-advisory.html
     *
     * Fortunately, gluster appears to limit its underlying bricks to
     * only use file systems such as XFS that have a NAME_MAX of 255;
     * so we are currently guaranteed that if we provide 256 bytes of
     * tail padding, then we should have enough space to avoid buffer
     * overflow no matter whether the OS used d_name[], d_name[1], or
     * d_name[256] in its 'struct dirent'.
     * http://lists.gnu.org/archive/html/gluster-devel/2013-10/msg00083.html
     */

    if (!(dir = glfs_opendir(state->vol, state->dir))) {
        virReportSystemError(errno, _("cannot open path '%s' in '%s'"),
                             state->dir, state->volname);
        goto cleanup;
    }
    while (!(errno = glfs_readdirplus_r(dir, &st, &de.ent, &ent)) && ent) {
        virStorageVolDefPtr vol;
        int okay = virStorageBackendGlusterRefreshVol(state,
                                                      ent->d_name, &st,
                                                      &vol);

        if (okay < 0)
            goto cleanup;
        if (vol && VIR_APPEND_ELEMENT(pool->volumes.objs, pool->volumes.count,
                                      vol) < 0)
            goto cleanup;
    }
    if (errno) {
        virReportSystemError(errno, _("failed to read directory '%s' in '%s'"),
                             state->dir, state->volname);
        goto cleanup;
    }

    if (glfs_statvfs(state->vol, state->dir, &sb) < 0) {
        virReportSystemError(errno, _("cannot statvfs path '%s' in '%s'"),
                             state->dir, state->volname);
        goto cleanup;
    }

    pool->def->capacity = ((unsigned long long)sb.f_frsize *
                           (unsigned long long)sb.f_blocks);
    pool->def->available = ((unsigned long long)sb.f_bfree *
                            (unsigned long long)sb.f_frsize);
    pool->def->allocation = pool->def->capacity - pool->def->available;

    ret = 0;
cleanup:
    if (dir)
        glfs_closedir(dir);
    virStorageBackendGlusterClose(state);
    if (ret < 0)
        virStoragePoolObjClearVols(pool);
    return ret;
}

virStorageBackend virStorageBackendGluster = {
    .type = VIR_STORAGE_POOL_GLUSTER,

    .refreshPool = virStorageBackendGlusterRefreshPool,
};