/*
   Copyright 2014-present Facebook. All Rights Reserved
   This file is part of GlusterFS.

   Author :
   Shreyas Siravara <shreyas.siravara@gmail.com>

   This file is licensed to you under your choice of the GNU Lesser
   General Public License, version 3 or any later version (LGPLv3 or
   later), or the GNU General Public License, version 2 (GPLv2), in all
   cases as published by the Free Software Foundation.
*/

#include <glusterfs/refcount.h>
#include "auth-cache.h"
#include "nfs3.h"
#include "exports.h"
#include "nfs-messages.h"

enum auth_cache_lookup_results {
    ENTRY_FOUND = 0,
    ENTRY_NOT_FOUND = -1,
    ENTRY_EXPIRED = -2,
};

struct auth_cache_entry {
    GF_REF_DECL;  /* refcounting */
    data_t *data; /* data_unref() on refcount == 0 */

    time_t timestamp;
    struct export_item *item;
};

/* Given a filehandle and an ip, creates a colon delimited hashkey.
 */
static char *
make_hashkey(struct nfs3_fh *fh, const char *host)
{
    char *hashkey = NULL;
    char exportid[256] = {
        0,
    };
    char gfid[256] = {
        0,
    };
    char mountid[256] = {
        0,
    };
    size_t nbytes = 0;

    gf_uuid_unparse(fh->exportid, exportid);
    gf_uuid_unparse(fh->gfid, gfid);
    gf_uuid_unparse(fh->mountid, mountid);

    nbytes = strlen(exportid) + strlen(host) + strlen(mountid) + 3;
    hashkey = GF_MALLOC(nbytes, gf_common_mt_char);
    if (!hashkey)
        return NULL;

    snprintf(hashkey, nbytes, "%s:%s:%s", exportid, mountid, host);

    return hashkey;
}

/**
 * auth_cache_init -- Initialize an auth cache and set the ttl_sec
 *
 * @ttl_sec : The TTL to set in seconds
 *
 * @return : allocated auth cache struct, NULL if allocation failed.
 */
struct auth_cache *
auth_cache_init(time_t ttl_sec)
{
    struct auth_cache *cache = GF_CALLOC(1, sizeof(*cache),
                                         gf_nfs_mt_auth_cache);

    GF_VALIDATE_OR_GOTO("auth-cache", cache, out);

    cache->cache_dict = dict_new();
    if (!cache->cache_dict) {
        GF_FREE(cache);
        cache = NULL;
        goto out;
    }

    LOCK_INIT(&cache->lock);
    cache->ttl_sec = ttl_sec;
out:
    return cache;
}

/* auth_cache_entry_free -- called by refcounting subsystem on refcount == 0
 *
 * @to_free: auth_cache_entry that has refcount == 0 and needs to get free'd
 */
void
auth_cache_entry_free(void *to_free)
{
    struct auth_cache_entry *entry = to_free;
    data_t *entry_data = NULL;

    GF_VALIDATE_OR_GOTO(GF_NFS, entry, out);
    GF_VALIDATE_OR_GOTO(GF_NFS, entry->data, out);

    entry_data = entry->data;
    /* set data_t->data to NULL, otherwise data_unref() tries to free it */
    entry_data->data = NULL;
    data_unref(entry_data);

    GF_FREE(entry);
out:
    return;
}

/**
 * auth_cache_entry_init -- Initialize an auth cache entry
 *
 * @return: Pointer to an allocated auth cache entry, NULL if allocation
 *          failed.
 */
static struct auth_cache_entry *
auth_cache_entry_init()
{
    struct auth_cache_entry *entry = NULL;

    entry = GF_CALLOC(1, sizeof(*entry), gf_nfs_mt_auth_cache_entry);
    if (!entry)
        gf_msg(GF_NFS, GF_LOG_WARNING, ENOMEM, NFS_MSG_NO_MEMORY,
               "failed to allocate entry");
    else
        GF_REF_INIT(entry, auth_cache_entry_free);

    return entry;
}

/**
 * auth_cache_add -- Add an auth_cache_entry to the cache->dict
 *
 * @return: 0 on success, non-zero otherwise.
 */
static int
auth_cache_add(struct auth_cache *cache, char *hashkey,
               struct auth_cache_entry *entry)
{
    int ret = -1;
    data_t *entry_data = NULL;

    GF_VALIDATE_OR_GOTO(GF_NFS, cache, out);
    GF_VALIDATE_OR_GOTO(GF_NFS, cache->cache_dict, out);

    /* FIXME: entry is passed as parameter, this can never fail? */
    entry = GF_REF_GET(entry);
    if (!entry) {
        /* entry does not have any references */
        ret = -1;
        goto out;
    }

    entry_data = bin_to_data(entry, sizeof(*entry));
    if (!entry_data) {
        ret = -1;
        GF_REF_PUT(entry);
        goto out;
    }

    /* we'll take an extra ref on the data_t, it gets unref'd when the
     * auth_cache_entry is released */
    entry->data = data_ref(entry_data);

    LOCK(&cache->lock);
    {
        ret = dict_set(cache->cache_dict, hashkey, entry_data);
    }
    UNLOCK(&cache->lock);

    if (ret) {
        /* adding to dict failed */
        GF_REF_PUT(entry);
    }
out:
    return ret;
}

/**
 * _auth_cache_expired -- Check if the auth_cache_entry has expired
 *
 * The auth_cache->lock should have been taken when this function is called.
 *
 * @return: true when the auth_cache_entry is expired, false otherwise.
 */
static int
_auth_cache_expired(struct auth_cache *cache, struct auth_cache_entry *entry)
{
    return ((time(NULL) - entry->timestamp) > cache->ttl_sec);
}

/**
 * auth_cache_get -- Get the @hashkey entry from the cache->cache_dict
 *
 * @cache: The auth_cache that should contain the @entry.
 * @haskkey: The key associated with the auth_cache_entry.
 * @entry: The found auth_cache_entry, unmodified if not found/expired.
 *
 * The using the cache->dict requires locking, this function takes care of
 * that. When the entry is found, but has expired, it will be removed from the
 * cache_dict.
 *
 * @return: 0 when found, ENTRY_NOT_FOUND or ENTRY_EXPIRED otherwise.
 */
static enum auth_cache_lookup_results
auth_cache_get(struct auth_cache *cache, char *hashkey,
               struct auth_cache_entry **entry)
{
    enum auth_cache_lookup_results ret = ENTRY_NOT_FOUND;
    data_t *entry_data = NULL;
    struct auth_cache_entry *lookup_res = NULL;

    GF_VALIDATE_OR_GOTO(GF_NFS, cache, out);
    GF_VALIDATE_OR_GOTO(GF_NFS, cache->cache_dict, out);
    GF_VALIDATE_OR_GOTO(GF_NFS, hashkey, out);

    LOCK(&cache->lock);
    {
        entry_data = dict_get(cache->cache_dict, hashkey);
        if (!entry_data)
            goto unlock;

        /* FIXME: this is dangerous use of entry_data */
        lookup_res = GF_REF_GET((struct auth_cache_entry *)entry_data->data);
        if (lookup_res == NULL) {
            /* entry has been free'd */
            ret = ENTRY_EXPIRED;
            goto unlock;
        }

        if (_auth_cache_expired(cache, lookup_res)) {
            ret = ENTRY_EXPIRED;
            GF_REF_PUT(lookup_res->item);
            lookup_res->item = NULL;

            /* free entry and remove from the cache */
            GF_FREE(lookup_res);
            entry_data->data = NULL;
            dict_del(cache->cache_dict, hashkey);

            goto unlock;
        }

        *entry = lookup_res;
        ret = ENTRY_FOUND;
    }
unlock:
    UNLOCK(&cache->lock);

out:
    return ret;
}

/**
 * auth_cache_lookup -- Lookup an item from the cache
 *
 * @cache: cache to lookup from
 * @fh   : FH to use in lookup
 * @host_addr: Address to use in lookup
 * @timestamp: The timestamp to set when lookup succeeds
 * @can_write: Is the host authorized to write to the filehandle?
 *
 * If the current time - entry time of the cache entry > ttl_sec,
 * we remove the element from the dict and return ENTRY_EXPIRED.
 *
 * @return: ENTRY_EXPIRED if entry expired
 *          ENTRY_NOT_FOUND if entry not found in dict
 *          0 if found
 */
enum auth_cache_lookup_results
auth_cache_lookup(struct auth_cache *cache, struct nfs3_fh *fh,
                  const char *host_addr, time_t *timestamp,
                  gf_boolean_t *can_write)
{
    char *hashkey = NULL;
    struct auth_cache_entry *lookup_res = NULL;
    enum auth_cache_lookup_results ret = ENTRY_NOT_FOUND;

    GF_VALIDATE_OR_GOTO(GF_NFS, cache, out);
    GF_VALIDATE_OR_GOTO(GF_NFS, fh, out);
    GF_VALIDATE_OR_GOTO(GF_NFS, host_addr, out);
    GF_VALIDATE_OR_GOTO(GF_NFS, timestamp, out);
    GF_VALIDATE_OR_GOTO(GF_NFS, can_write, out);

    hashkey = make_hashkey(fh, host_addr);
    if (!hashkey) {
        ret = -ENOMEM;
        goto out;
    }

    ret = auth_cache_get(cache, hashkey, &lookup_res);
    switch (ret) {
        case ENTRY_FOUND:
            *timestamp = lookup_res->timestamp;
            *can_write = lookup_res->item->opts->rw;
            GF_REF_PUT(lookup_res);
            break;

        case ENTRY_NOT_FOUND:
            gf_msg_debug(GF_NFS, 0, "could not find entry for %s", host_addr);
            break;

        case ENTRY_EXPIRED:
            gf_msg_debug(GF_NFS, 0, "entry for host %s has expired", host_addr);
            break;
    }

out:
    GF_FREE(hashkey);

    return ret;
}

/* auth_cache_entry_purge -- free up the auth_cache_entry
 *
 * This gets called through dict_foreach() by auth_cache_purge(). Each
 * auth_cache_entry has a refcount which needs to be decremented. Once the
 * auth_cache_entry reaches refcount == 0, auth_cache_entry_free() will call
 * data_unref() to free the associated data_t.
 *
 * @d: dict that gets purged by auth_cache_purge()
 * @k: hashkey of the current entry
 * @v: data_t of the current entry
 */
int
auth_cache_entry_purge(dict_t *d, char *k, data_t *v, void *_unused)
{
    struct auth_cache_entry *entry = (struct auth_cache_entry *)v->data;

    if (entry)
        GF_REF_PUT(entry);

    return 0;
}

/**
 * auth_cache_purge -- Purge the dict in the cache and create a new empty one.
 *
 * @cache: Cache to purge
 *
 */
void
auth_cache_purge(struct auth_cache *cache)
{
    dict_t *new_cache_dict = dict_new();
    dict_t *old_cache_dict = NULL;

    if (!cache || !new_cache_dict)
        goto out;

    LOCK(&cache->lock);
    {
        old_cache_dict = cache->cache_dict;
        cache->cache_dict = new_cache_dict;
    }
    UNLOCK(&cache->lock);

    /* walk all entries and refcount-- with GF_REF_PUT() */
    dict_foreach(old_cache_dict, auth_cache_entry_purge, NULL);
    dict_unref(old_cache_dict);
out:
    return;
}

/**
 * is_nfs_fh_cached_and_writeable -- Checks if an NFS FH is cached for the given
 *                                   host
 * @cache: The fh cache
 * @host_addr: Address to use in lookup
 * @fh: The fh to use in lookup
 *
 *
 * @return: TRUE if cached, FALSE otherwise
 *
 */
gf_boolean_t
is_nfs_fh_cached(struct auth_cache *cache, struct nfs3_fh *fh,
                 const char *host_addr)
{
    int ret = 0;
    time_t timestamp = 0;
    gf_boolean_t cached = _gf_false;
    gf_boolean_t can_write = _gf_false;

    if (!fh)
        goto out;

    ret = auth_cache_lookup(cache, fh, host_addr, &timestamp, &can_write);
    cached = (ret == ENTRY_FOUND);

out:
    return cached;
}

/**
 * is_nfs_fh_cached_and_writeable -- Checks if an NFS FH is cached for the given
 *                                   host and writable
 * @cache: The fh cache
 * @host_addr: Address to use in lookup
 * @fh: The fh to use in lookup
 *
 *
 * @return: TRUE if cached & writable, FALSE otherwise
 *
 */
gf_boolean_t
is_nfs_fh_cached_and_writeable(struct auth_cache *cache, struct nfs3_fh *fh,
                               const char *host_addr)
{
    int ret = 0;
    time_t timestamp = 0;
    gf_boolean_t cached = _gf_false;
    gf_boolean_t writable = _gf_false;

    if (!fh)
        goto out;

    ret = auth_cache_lookup(cache, fh, host_addr, &timestamp, &writable);
    cached = ((ret == ENTRY_FOUND) && writable);

out:
    return cached;
}

/**
 * cache_nfs_fh -- Places the nfs file handle in the underlying dict as we are
 *                 using as our cache. The key is "exportid:gfid:host_addr", the
 *                 value is an entry struct containing the export item that
 *                 was authorized for the operation and the file handle that was
 *                 authorized.
 *
 * @cache: The cache to place fh's in
 * @fh   : The fh to cache
 * @host_addr: The address of the host
 * @export_item: The export item that was authorized
 *
 */
int
cache_nfs_fh(struct auth_cache *cache, struct nfs3_fh *fh,
             const char *host_addr, struct export_item *export_item)
{
    int ret = -EINVAL;
    char *hashkey = NULL;
    time_t timestamp = 0;
    gf_boolean_t can_write = _gf_false;
    struct auth_cache_entry *entry = NULL;

    GF_VALIDATE_OR_GOTO(GF_NFS, host_addr, out);
    GF_VALIDATE_OR_GOTO(GF_NFS, cache, out);
    GF_VALIDATE_OR_GOTO(GF_NFS, fh, out);

    /* If we could already find it in the cache, just return */
    ret = auth_cache_lookup(cache, fh, host_addr, &timestamp, &can_write);
    if (ret == 0) {
        gf_msg_trace(GF_NFS, 0,
                     "found cached auth/fh for host "
                     "%s",
                     host_addr);
        goto out;
    }

    hashkey = make_hashkey(fh, host_addr);
    if (!hashkey) {
        ret = -ENOMEM;
        goto out;
    }

    entry = auth_cache_entry_init();
    if (!entry) {
        ret = -ENOMEM;
        goto out;
    }

    entry->timestamp = time(NULL);
    /* Update entry->item if it is pointing to a different export_item */
    if (entry->item && entry->item != export_item) {
        GF_REF_PUT(entry->item);
    }
    entry->item = GF_REF_GET(export_item);

    ret = auth_cache_add(cache, hashkey, entry);
    GF_REF_PUT(entry);
    if (ret)
        goto out;

    gf_msg_trace(GF_NFS, 0, "Caching file-handle (%s)", host_addr);
    ret = 0;

out:
    GF_FREE(hashkey);

    return ret;
}