// SPDX-License-Identifier: GPL-2.0
/*
 * DFS referral cache routines
 *
 * Copyright (c) 2018-2019 Paulo Alcantara <palcantara@suse.de>
 */

#include <linux/rcupdate.h>
#include <linux/rculist.h>
#include <linux/jhash.h>
#include <linux/ktime.h>
#include <linux/slab.h>
#include <linux/nls.h>
#include <linux/workqueue.h>
#include "cifsglob.h"
#include "smb2pdu.h"
#include "smb2proto.h"
#include "cifsproto.h"
#include "cifs_debug.h"
#include "cifs_unicode.h"
#include "smb2glob.h"

#include "dfs_cache.h"

#define DFS_CACHE_HTABLE_SIZE 32
#define DFS_CACHE_MAX_ENTRIES 64

#define IS_INTERLINK_SET(v) ((v) & (DFSREF_REFERRAL_SERVER | \
                                    DFSREF_STORAGE_SERVER))

struct dfs_cache_tgt {
        char *t_name;
        struct list_head t_list;
};

struct dfs_cache_entry {
        struct hlist_node ce_hlist;
        const char *ce_path;
        int ce_ttl;
        int ce_srvtype;
        int ce_flags;
        struct timespec64 ce_etime;
        int ce_path_consumed;
        int ce_numtgts;
        struct list_head ce_tlist;
        struct dfs_cache_tgt *ce_tgthint;
        struct rcu_head ce_rcu;
};

static struct kmem_cache *dfs_cache_slab __read_mostly;

struct dfs_cache_vol_info {
        char *vi_fullpath;
        struct smb_vol vi_vol;
        char *vi_mntdata;
        struct list_head vi_list;
};

struct dfs_cache {
        struct mutex dc_lock;
        struct nls_table *dc_nlsc;
        struct list_head dc_vol_list;
        int dc_ttl;
        struct delayed_work dc_refresh;
};

static struct dfs_cache dfs_cache;

/*
 * Number of entries in the cache
 */
static size_t dfs_cache_count;

static DEFINE_MUTEX(dfs_cache_list_lock);
static struct hlist_head dfs_cache_htable[DFS_CACHE_HTABLE_SIZE];

static void refresh_cache_worker(struct work_struct *work);

static inline bool is_path_valid(const char *path)
{
        return path && (strchr(path + 1, '\\') || strchr(path + 1, '/'));
}

static inline int get_normalized_path(const char *path, char **npath)
{
        if (*path == '\\') {
                *npath = (char *)path;
        } else {
                *npath = kstrndup(path, strlen(path), GFP_KERNEL);
                if (!*npath)
                        return -ENOMEM;
                convert_delimiter(*npath, '\\');
        }
        return 0;
}

static inline void free_normalized_path(const char *path, char *npath)
{
        if (path != npath)
                kfree(npath);
}

static inline bool cache_entry_expired(const struct dfs_cache_entry *ce)
{
        struct timespec64 ts;

        ktime_get_coarse_real_ts64(&ts);
        return timespec64_compare(&ts, &ce->ce_etime) >= 0;
}

static inline void free_tgts(struct dfs_cache_entry *ce)
{
        struct dfs_cache_tgt *t, *n;

        list_for_each_entry_safe(t, n, &ce->ce_tlist, t_list) {
                list_del(&t->t_list);
                kfree(t->t_name);
                kfree(t);
        }
}

static void free_cache_entry(struct rcu_head *rcu)
{
        struct dfs_cache_entry *ce = container_of(rcu, struct dfs_cache_entry,
                                                  ce_rcu);
        kmem_cache_free(dfs_cache_slab, ce);
}

static inline void flush_cache_ent(struct dfs_cache_entry *ce)
{
        if (hlist_unhashed(&ce->ce_hlist))
                return;

        hlist_del_init_rcu(&ce->ce_hlist);
        kfree_const(ce->ce_path);
        free_tgts(ce);
        dfs_cache_count--;
        call_rcu(&ce->ce_rcu, free_cache_entry);
}

static void flush_cache_ents(void)
{
        int i;

        rcu_read_lock();
        for (i = 0; i < DFS_CACHE_HTABLE_SIZE; i++) {
                struct hlist_head *l = &dfs_cache_htable[i];
                struct dfs_cache_entry *ce;

                hlist_for_each_entry_rcu(ce, l, ce_hlist)
                        flush_cache_ent(ce);
        }
        rcu_read_unlock();
}

/*
 * dfs cache /proc file
 */
static int dfscache_proc_show(struct seq_file *m, void *v)
{
        int bucket;
        struct dfs_cache_entry *ce;
        struct dfs_cache_tgt *t;

        seq_puts(m, "DFS cache\n---------\n");

        mutex_lock(&dfs_cache_list_lock);

        rcu_read_lock();
        hash_for_each_rcu(dfs_cache_htable, bucket, ce, ce_hlist) {
                seq_printf(m,
                           "cache entry: path=%s,type=%s,ttl=%d,etime=%ld,"
                           "interlink=%s,path_consumed=%d,expired=%s\n",
                           ce->ce_path,
                           ce->ce_srvtype == DFS_TYPE_ROOT ? "root" : "link",
                           ce->ce_ttl, ce->ce_etime.tv_nsec,
                           IS_INTERLINK_SET(ce->ce_flags) ? "yes" : "no",
                           ce->ce_path_consumed,
                           cache_entry_expired(ce) ? "yes" : "no");

                list_for_each_entry(t, &ce->ce_tlist, t_list) {
                        seq_printf(m, "  %s%s\n",
                                   t->t_name,
                                   ce->ce_tgthint == t ? " (target hint)" : "");
                }

        }
        rcu_read_unlock();

        mutex_unlock(&dfs_cache_list_lock);
        return 0;
}

static ssize_t dfscache_proc_write(struct file *file, const char __user *buffer,
                                   size_t count, loff_t *ppos)
{
        char c;
        int rc;

        rc = get_user(c, buffer);
        if (rc)
                return rc;

        if (c != '0')
                return -EINVAL;

        cifs_dbg(FYI, "clearing dfs cache");
        mutex_lock(&dfs_cache_list_lock);
        flush_cache_ents();
        mutex_unlock(&dfs_cache_list_lock);

        return count;
}

static int dfscache_proc_open(struct inode *inode, struct file *file)
{
        return single_open(file, dfscache_proc_show, NULL);
}

const struct file_operations dfscache_proc_fops = {
        .open           = dfscache_proc_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = single_release,
        .write          = dfscache_proc_write,
};

#ifdef CONFIG_CIFS_DEBUG2
static inline void dump_tgts(const struct dfs_cache_entry *ce)
{
        struct dfs_cache_tgt *t;

        cifs_dbg(FYI, "target list:\n");
        list_for_each_entry(t, &ce->ce_tlist, t_list) {
                cifs_dbg(FYI, "  %s%s\n", t->t_name,
                         ce->ce_tgthint == t ? " (target hint)" : "");
        }
}

static inline void dump_ce(const struct dfs_cache_entry *ce)
{
        cifs_dbg(FYI, "cache entry: path=%s,type=%s,ttl=%d,etime=%ld,"
                 "interlink=%s,path_consumed=%d,expired=%s\n", ce->ce_path,
                 ce->ce_srvtype == DFS_TYPE_ROOT ? "root" : "link", ce->ce_ttl,
                 ce->ce_etime.tv_nsec,
                 IS_INTERLINK_SET(ce->ce_flags) ? "yes" : "no",
                 ce->ce_path_consumed,
                 cache_entry_expired(ce) ? "yes" : "no");
        dump_tgts(ce);
}

static inline void dump_refs(const struct dfs_info3_param *refs, int numrefs)
{
        int i;

        cifs_dbg(FYI, "DFS referrals returned by the server:\n");
        for (i = 0; i < numrefs; i++) {
                const struct dfs_info3_param *ref = &refs[i];

                cifs_dbg(FYI,
                         "\n"
                         "flags:         0x%x\n"
                         "path_consumed: %d\n"
                         "server_type:   0x%x\n"
                         "ref_flag:      0x%x\n"
                         "path_name:     %s\n"
                         "node_name:     %s\n"
                         "ttl:           %d (%dm)\n",
                         ref->flags, ref->path_consumed, ref->server_type,
                         ref->ref_flag, ref->path_name, ref->node_name,
                         ref->ttl, ref->ttl / 60);
        }
}
#else
#define dump_tgts(e)
#define dump_ce(e)
#define dump_refs(r, n)
#endif

/**
 * dfs_cache_init - Initialize DFS referral cache.
 *
 * Return zero if initialized successfully, otherwise non-zero.
 */
int dfs_cache_init(void)
{
        int i;

        dfs_cache_slab = kmem_cache_create("cifs_dfs_cache",
                                           sizeof(struct dfs_cache_entry), 0,
                                           SLAB_HWCACHE_ALIGN, NULL);
        if (!dfs_cache_slab)
                return -ENOMEM;

        for (i = 0; i < DFS_CACHE_HTABLE_SIZE; i++)
                INIT_HLIST_HEAD(&dfs_cache_htable[i]);

        INIT_LIST_HEAD(&dfs_cache.dc_vol_list);
        mutex_init(&dfs_cache.dc_lock);
        INIT_DELAYED_WORK(&dfs_cache.dc_refresh, refresh_cache_worker);
        dfs_cache.dc_ttl = -1;
        dfs_cache.dc_nlsc = load_nls_default();

        cifs_dbg(FYI, "%s: initialized DFS referral cache\n", __func__);
        return 0;
}

static inline unsigned int cache_entry_hash(const void *data, int size)
{
        unsigned int h;

        h = jhash(data, size, 0);
        return h & (DFS_CACHE_HTABLE_SIZE - 1);
}

/* Check whether second path component of @path is SYSVOL or NETLOGON */
static inline bool is_sysvol_or_netlogon(const char *path)
{
        const char *s;
        char sep = path[0];

        s = strchr(path + 1, sep) + 1;
        return !strncasecmp(s, "sysvol", strlen("sysvol")) ||
                !strncasecmp(s, "netlogon", strlen("netlogon"));
}

/* Return target hint of a DFS cache entry */
static inline char *get_tgt_name(const struct dfs_cache_entry *ce)
{
        struct dfs_cache_tgt *t = ce->ce_tgthint;

        return t ? t->t_name : ERR_PTR(-ENOENT);
}

/* Return expire time out of a new entry's TTL */
static inline struct timespec64 get_expire_time(int ttl)
{
        struct timespec64 ts = {
                .tv_sec = ttl,
                .tv_nsec = 0,
        };
        struct timespec64 now;

        ktime_get_coarse_real_ts64(&now);
        return timespec64_add(now, ts);
}

/* Allocate a new DFS target */
static inline struct dfs_cache_tgt *alloc_tgt(const char *name)
{
        struct dfs_cache_tgt *t;

        t = kmalloc(sizeof(*t), GFP_KERNEL);
        if (!t)
                return ERR_PTR(-ENOMEM);
        t->t_name = kstrndup(name, strlen(name), GFP_KERNEL);
        if (!t->t_name) {
                kfree(t);
                return ERR_PTR(-ENOMEM);
        }
        INIT_LIST_HEAD(&t->t_list);
        return t;
}

/*
 * Copy DFS referral information to a cache entry and conditionally update
 * target hint.
 */
static int copy_ref_data(const struct dfs_info3_param *refs, int numrefs,
                         struct dfs_cache_entry *ce, const char *tgthint)
{
        int i;

        ce->ce_ttl = refs[0].ttl;
        ce->ce_etime = get_expire_time(ce->ce_ttl);
        ce->ce_srvtype = refs[0].server_type;
        ce->ce_flags = refs[0].ref_flag;
        ce->ce_path_consumed = refs[0].path_consumed;

        for (i = 0; i < numrefs; i++) {
                struct dfs_cache_tgt *t;

                t = alloc_tgt(refs[i].node_name);
                if (IS_ERR(t)) {
                        free_tgts(ce);
                        return PTR_ERR(t);
                }
                if (tgthint && !strcasecmp(t->t_name, tgthint)) {
                        list_add(&t->t_list, &ce->ce_tlist);
                        tgthint = NULL;
                } else {
                        list_add_tail(&t->t_list, &ce->ce_tlist);
                }
                ce->ce_numtgts++;
        }

        ce->ce_tgthint = list_first_entry_or_null(&ce->ce_tlist,
                                                  struct dfs_cache_tgt, t_list);

        return 0;
}

/* Allocate a new cache entry */
static struct dfs_cache_entry *
alloc_cache_entry(const char *path, const struct dfs_info3_param *refs,
                  int numrefs)
{
        struct dfs_cache_entry *ce;
        int rc;

        ce = kmem_cache_zalloc(dfs_cache_slab, GFP_KERNEL);
        if (!ce)
                return ERR_PTR(-ENOMEM);

        ce->ce_path = kstrdup_const(path, GFP_KERNEL);
        if (!ce->ce_path) {
                kmem_cache_free(dfs_cache_slab, ce);
                return ERR_PTR(-ENOMEM);
        }
        INIT_HLIST_NODE(&ce->ce_hlist);
        INIT_LIST_HEAD(&ce->ce_tlist);

        rc = copy_ref_data(refs, numrefs, ce, NULL);
        if (rc) {
                kfree_const(ce->ce_path);
                kmem_cache_free(dfs_cache_slab, ce);
                ce = ERR_PTR(rc);
        }
        return ce;
}

static void remove_oldest_entry(void)
{
        int bucket;
        struct dfs_cache_entry *ce;
        struct dfs_cache_entry *to_del = NULL;

        rcu_read_lock();
        hash_for_each_rcu(dfs_cache_htable, bucket, ce, ce_hlist) {
                if (!to_del || timespec64_compare(&ce->ce_etime,
                                                  &to_del->ce_etime) < 0)
                        to_del = ce;
        }
        if (!to_del) {
                cifs_dbg(FYI, "%s: no entry to remove", __func__);
                goto out;
        }
        cifs_dbg(FYI, "%s: removing entry", __func__);
        dump_ce(to_del);
        flush_cache_ent(to_del);
out:
        rcu_read_unlock();
}

/* Add a new DFS cache entry */
static inline struct dfs_cache_entry *
add_cache_entry(unsigned int hash, const char *path,
                const struct dfs_info3_param *refs, int numrefs)
{
        struct dfs_cache_entry *ce;

        ce = alloc_cache_entry(path, refs, numrefs);
        if (IS_ERR(ce))
                return ce;

        hlist_add_head_rcu(&ce->ce_hlist, &dfs_cache_htable[hash]);

        mutex_lock(&dfs_cache.dc_lock);
        if (dfs_cache.dc_ttl < 0) {
                dfs_cache.dc_ttl = ce->ce_ttl;
                queue_delayed_work(cifsiod_wq, &dfs_cache.dc_refresh,
                                   dfs_cache.dc_ttl * HZ);
        } else {
                dfs_cache.dc_ttl = min_t(int, dfs_cache.dc_ttl, ce->ce_ttl);
                mod_delayed_work(cifsiod_wq, &dfs_cache.dc_refresh,
                                 dfs_cache.dc_ttl * HZ);
        }
        mutex_unlock(&dfs_cache.dc_lock);

        return ce;
}

static struct dfs_cache_entry *__find_cache_entry(unsigned int hash,
                                                  const char *path)
{
        struct dfs_cache_entry *ce;
        bool found = false;

        rcu_read_lock();
        hlist_for_each_entry_rcu(ce, &dfs_cache_htable[hash], ce_hlist) {
                if (!strcasecmp(path, ce->ce_path)) {
#ifdef CONFIG_CIFS_DEBUG2
                        char *name = get_tgt_name(ce);

                        if (IS_ERR(name)) {
                                rcu_read_unlock();
                                return ERR_CAST(name);
                        }
                        cifs_dbg(FYI, "%s: cache hit\n", __func__);
                        cifs_dbg(FYI, "%s: target hint: %s\n", __func__, name);
#endif
                        found = true;
                        break;
                }
        }
        rcu_read_unlock();
        return found ? ce : ERR_PTR(-ENOENT);
}

/*
 * Find a DFS cache entry in hash table and optionally check prefix path against
 * @path.
 * Use whole path components in the match.
 * Return ERR_PTR(-ENOENT) if the entry is not found.
 */
static inline struct dfs_cache_entry *find_cache_entry(const char *path,
                                                       unsigned int *hash)
{
        *hash = cache_entry_hash(path, strlen(path));
        return __find_cache_entry(*hash, path);
}

static inline void destroy_slab_cache(void)
{
        rcu_barrier();
        kmem_cache_destroy(dfs_cache_slab);
}

static inline void free_vol(struct dfs_cache_vol_info *vi)
{
        list_del(&vi->vi_list);
        kfree(vi->vi_fullpath);
        kfree(vi->vi_mntdata);
        cifs_cleanup_volume_info_contents(&vi->vi_vol);
        kfree(vi);
}

static inline void free_vol_list(void)
{
        struct dfs_cache_vol_info *vi, *nvi;

        list_for_each_entry_safe(vi, nvi, &dfs_cache.dc_vol_list, vi_list)
                free_vol(vi);
}

/**
 * dfs_cache_destroy - destroy DFS referral cache
 */
void dfs_cache_destroy(void)
{
        cancel_delayed_work_sync(&dfs_cache.dc_refresh);
        unload_nls(dfs_cache.dc_nlsc);
        free_vol_list();
        mutex_destroy(&dfs_cache.dc_lock);

        flush_cache_ents();
        destroy_slab_cache();
        mutex_destroy(&dfs_cache_list_lock);

        cifs_dbg(FYI, "%s: destroyed DFS referral cache\n", __func__);
}

static inline struct dfs_cache_entry *
__update_cache_entry(const char *path, const struct dfs_info3_param *refs,
                     int numrefs)
{
        int rc;
        unsigned int h;
        struct dfs_cache_entry *ce;
        char *s, *th = NULL;

        ce = find_cache_entry(path, &h);
        if (IS_ERR(ce))
                return ce;

        if (ce->ce_tgthint) {
                s = ce->ce_tgthint->t_name;
                th = kstrndup(s, strlen(s), GFP_KERNEL);
                if (!th)
                        return ERR_PTR(-ENOMEM);
        }

        free_tgts(ce);
        ce->ce_numtgts = 0;

        rc = copy_ref_data(refs, numrefs, ce, th);
        kfree(th);

        if (rc)
                ce = ERR_PTR(rc);

        return ce;
}

/* Update an expired cache entry by getting a new DFS referral from server */
static struct dfs_cache_entry *
update_cache_entry(const unsigned int xid, struct cifs_ses *ses,
                   const struct nls_table *nls_codepage, int remap,
                   const char *path, struct dfs_cache_entry *ce)
{
        int rc;
        struct dfs_info3_param *refs = NULL;
        int numrefs = 0;

        cifs_dbg(FYI, "%s: update expired cache entry\n", __func__);
        /*
         * Check if caller provided enough parameters to update an expired
         * entry.
         */
        if (!ses || !ses->server || !ses->server->ops->get_dfs_refer)
                return ERR_PTR(-ETIME);
        if (unlikely(!nls_codepage))
                return ERR_PTR(-ETIME);

        cifs_dbg(FYI, "%s: DFS referral request for %s\n", __func__, path);

        rc = ses->server->ops->get_dfs_refer(xid, ses, path, &refs, &numrefs,
                                             nls_codepage, remap);
        if (rc)
                ce = ERR_PTR(rc);
        else
                ce = __update_cache_entry(path, refs, numrefs);

        dump_refs(refs, numrefs);
        free_dfs_info_array(refs, numrefs);

        return ce;
}

/*
 * Find, create or update a DFS cache entry.
 *
 * If the entry wasn't found, it will create a new one. Or if it was found but
 * expired, then it will update the entry accordingly.
 *
 * For interlinks, __cifs_dfs_mount() and expand_dfs_referral() are supposed to
 * handle them properly.
 */
static struct dfs_cache_entry *
do_dfs_cache_find(const unsigned int xid, struct cifs_ses *ses,
                  const struct nls_table *nls_codepage, int remap,
                  const char *path, bool noreq)
{
        int rc;
        unsigned int h;
        struct dfs_cache_entry *ce;
        struct dfs_info3_param *nrefs;
        int numnrefs;

        cifs_dbg(FYI, "%s: search path: %s\n", __func__, path);

        ce = find_cache_entry(path, &h);
        if (IS_ERR(ce)) {
                cifs_dbg(FYI, "%s: cache miss\n", __func__);
                /*
                 * If @noreq is set, no requests will be sent to the server for
                 * either updating or getting a new DFS referral.
                 */
                if (noreq)
                        return ce;
                /*
                 * No cache entry was found, so check for valid parameters that
                 * will be required to get a new DFS referral and then create a
                 * new cache entry.
                 */
                if (!ses || !ses->server || !ses->server->ops->get_dfs_refer) {
                        ce = ERR_PTR(-EOPNOTSUPP);
                        return ce;
                }
                if (unlikely(!nls_codepage)) {
                        ce = ERR_PTR(-EINVAL);
                        return ce;
                }

                nrefs = NULL;
                numnrefs = 0;

                cifs_dbg(FYI, "%s: DFS referral request for %s\n", __func__,
                         path);

                rc = ses->server->ops->get_dfs_refer(xid, ses, path, &nrefs,
                                                     &numnrefs, nls_codepage,
                                                     remap);
                if (rc) {
                        ce = ERR_PTR(rc);
                        return ce;
                }

                dump_refs(nrefs, numnrefs);

                cifs_dbg(FYI, "%s: new cache entry\n", __func__);

                if (dfs_cache_count >= DFS_CACHE_MAX_ENTRIES) {
                        cifs_dbg(FYI, "%s: reached max cache size (%d)",
                                 __func__, DFS_CACHE_MAX_ENTRIES);
                        remove_oldest_entry();
                }
                ce = add_cache_entry(h, path, nrefs, numnrefs);
                free_dfs_info_array(nrefs, numnrefs);

                if (IS_ERR(ce))
                        return ce;

                dfs_cache_count++;
        }

        dump_ce(ce);

        /* Just return the found cache entry in case @noreq is set */
        if (noreq)
                return ce;

        if (cache_entry_expired(ce)) {
                cifs_dbg(FYI, "%s: expired cache entry\n", __func__);
                ce = update_cache_entry(xid, ses, nls_codepage, remap, path,
                                        ce);
                if (IS_ERR(ce)) {
                        cifs_dbg(FYI, "%s: failed to update expired entry\n",
                                 __func__);
                }
        }
        return ce;
}

/* Set up a new DFS referral from a given cache entry */
static int setup_ref(const char *path, const struct dfs_cache_entry *ce,
                     struct dfs_info3_param *ref, const char *tgt)
{
        int rc;

        cifs_dbg(FYI, "%s: set up new ref\n", __func__);

        memset(ref, 0, sizeof(*ref));

        ref->path_name = kstrndup(path, strlen(path), GFP_KERNEL);
        if (!ref->path_name)
                return -ENOMEM;

        ref->path_consumed = ce->ce_path_consumed;

        ref->node_name = kstrndup(tgt, strlen(tgt), GFP_KERNEL);
        if (!ref->node_name) {
                rc = -ENOMEM;
                goto err_free_path;
        }

        ref->ttl = ce->ce_ttl;
        ref->server_type = ce->ce_srvtype;
        ref->ref_flag = ce->ce_flags;

        return 0;

err_free_path:
        kfree(ref->path_name);
        ref->path_name = NULL;
        return rc;
}

/* Return target list of a DFS cache entry */
static int get_tgt_list(const struct dfs_cache_entry *ce,
                        struct dfs_cache_tgt_list *tl)
{
        int rc;
        struct list_head *head = &tl->tl_list;
        struct dfs_cache_tgt *t;
        struct dfs_cache_tgt_iterator *it, *nit;

        memset(tl, 0, sizeof(*tl));
        INIT_LIST_HEAD(head);

        list_for_each_entry(t, &ce->ce_tlist, t_list) {
                it = kzalloc(sizeof(*it), GFP_KERNEL);
                if (!it) {
                        rc = -ENOMEM;
                        goto err_free_it;
                }

                it->it_name = kstrndup(t->t_name, strlen(t->t_name),
                                       GFP_KERNEL);
                if (!it->it_name) {
                        kfree(it);
                        rc = -ENOMEM;
                        goto err_free_it;
                }

                if (ce->ce_tgthint == t)
                        list_add(&it->it_list, head);
                else
                        list_add_tail(&it->it_list, head);
        }
        tl->tl_numtgts = ce->ce_numtgts;

        return 0;

err_free_it:
        list_for_each_entry_safe(it, nit, head, it_list) {
                kfree(it->it_name);
                kfree(it);
        }
        return rc;
}

/**
 * dfs_cache_find - find a DFS cache entry
 *
 * If it doesn't find the cache entry, then it will get a DFS referral
 * for @path and create a new entry.
 *
 * In case the cache entry exists but expired, it will get a DFS referral
 * for @path and then update the respective cache entry.
 *
 * These parameters are passed down to the get_dfs_refer() call if it
 * needs to be issued:
 * @xid: syscall xid
 * @ses: smb session to issue the request on
 * @nls_codepage: charset conversion
 * @remap: path character remapping type
 * @path: path to lookup in DFS referral cache.
 *
 * @ref: when non-NULL, store single DFS referral result in it.
 * @tgt_list: when non-NULL, store complete DFS target list in it.
 *
 * Return zero if the target was found, otherwise non-zero.
 */
int dfs_cache_find(const unsigned int xid, struct cifs_ses *ses,
                   const struct nls_table *nls_codepage, int remap,
                   const char *path, struct dfs_info3_param *ref,
                   struct dfs_cache_tgt_list *tgt_list)
{
        int rc;
        char *npath;
        struct dfs_cache_entry *ce;

        if (unlikely(!is_path_valid(path)))
                return -EINVAL;

        rc = get_normalized_path(path, &npath);
        if (rc)
                return rc;

        mutex_lock(&dfs_cache_list_lock);
        ce = do_dfs_cache_find(xid, ses, nls_codepage, remap, npath, false);
        if (!IS_ERR(ce)) {
                if (ref)
                        rc = setup_ref(path, ce, ref, get_tgt_name(ce));
                else
                        rc = 0;
                if (!rc && tgt_list)
                        rc = get_tgt_list(ce, tgt_list);
        } else {
                rc = PTR_ERR(ce);
        }
        mutex_unlock(&dfs_cache_list_lock);
        free_normalized_path(path, npath);
        return rc;
}

/**
 * dfs_cache_noreq_find - find a DFS cache entry without sending any requests to
 * the currently connected server.
 *
 * NOTE: This function will neither update a cache entry in case it was
 * expired, nor create a new cache entry if @path hasn't been found. It heavily
 * relies on an existing cache entry.
 *
 * @path: path to lookup in the DFS referral cache.
 * @ref: when non-NULL, store single DFS referral result in it.
 * @tgt_list: when non-NULL, store complete DFS target list in it.
 *
 * Return 0 if successful.
 * Return -ENOENT if the entry was not found.
 * Return non-zero for other errors.
 */
int dfs_cache_noreq_find(const char *path, struct dfs_info3_param *ref,
                         struct dfs_cache_tgt_list *tgt_list)
{
        int rc;
        char *npath;
        struct dfs_cache_entry *ce;

        if (unlikely(!is_path_valid(path)))
                return -EINVAL;

        rc = get_normalized_path(path, &npath);
        if (rc)
                return rc;

        mutex_lock(&dfs_cache_list_lock);
        ce = do_dfs_cache_find(0, NULL, NULL, 0, npath, true);
        if (IS_ERR(ce)) {
                rc = PTR_ERR(ce);
                goto out;
        }

        if (ref)
                rc = setup_ref(path, ce, ref, get_tgt_name(ce));
        else
                rc = 0;
        if (!rc && tgt_list)
                rc = get_tgt_list(ce, tgt_list);
out:
        mutex_unlock(&dfs_cache_list_lock);
        free_normalized_path(path, npath);
        return rc;
}

/**
 * dfs_cache_update_tgthint - update target hint of a DFS cache entry
 *
 * If it doesn't find the cache entry, then it will get a DFS referral for @path
 * and create a new entry.
 *
 * In case the cache entry exists but expired, it will get a DFS referral
 * for @path and then update the respective cache entry.
 *
 * @xid: syscall id
 * @ses: smb session
 * @nls_codepage: charset conversion
 * @remap: type of character remapping for paths
 * @path: path to lookup in DFS referral cache.
 * @it: DFS target iterator
 *
 * Return zero if the target hint was updated successfully, otherwise non-zero.
 */
int dfs_cache_update_tgthint(const unsigned int xid, struct cifs_ses *ses,
                             const struct nls_table *nls_codepage, int remap,
                             const char *path,
                             const struct dfs_cache_tgt_iterator *it)
{
        int rc;
        char *npath;
        struct dfs_cache_entry *ce;
        struct dfs_cache_tgt *t;

        if (unlikely(!is_path_valid(path)))
                return -EINVAL;

        rc = get_normalized_path(path, &npath);
        if (rc)
                return rc;

        cifs_dbg(FYI, "%s: path: %s\n", __func__, npath);

        mutex_lock(&dfs_cache_list_lock);
        ce = do_dfs_cache_find(xid, ses, nls_codepage, remap, npath, false);
        if (IS_ERR(ce)) {
                rc = PTR_ERR(ce);
                goto out;
        }

        rc = 0;

        t = ce->ce_tgthint;

        if (likely(!strcasecmp(it->it_name, t->t_name)))
                goto out;

        list_for_each_entry(t, &ce->ce_tlist, t_list) {
                if (!strcasecmp(t->t_name, it->it_name)) {
                        ce->ce_tgthint = t;
                        cifs_dbg(FYI, "%s: new target hint: %s\n", __func__,
                                 it->it_name);
                        break;
                }
        }

out:
        mutex_unlock(&dfs_cache_list_lock);
        free_normalized_path(path, npath);
        return rc;
}

/**
 * dfs_cache_noreq_update_tgthint - update target hint of a DFS cache entry
 * without sending any requests to the currently connected server.
 *
 * NOTE: This function will neither update a cache entry in case it was
 * expired, nor create a new cache entry if @path hasn't been found. It heavily
 * relies on an existing cache entry.
 *
 * @path: path to lookup in DFS referral cache.
 * @it: target iterator which contains the target hint to update the cache
 * entry with.
 *
 * Return zero if the target hint was updated successfully, otherwise non-zero.
 */
int dfs_cache_noreq_update_tgthint(const char *path,
                                   const struct dfs_cache_tgt_iterator *it)
{
        int rc;
        char *npath;
        struct dfs_cache_entry *ce;
        struct dfs_cache_tgt *t;

        if (unlikely(!is_path_valid(path)) || !it)
                return -EINVAL;

        rc = get_normalized_path(path, &npath);
        if (rc)
                return rc;

        cifs_dbg(FYI, "%s: path: %s\n", __func__, npath);

        mutex_lock(&dfs_cache_list_lock);

        ce = do_dfs_cache_find(0, NULL, NULL, 0, npath, true);
        if (IS_ERR(ce)) {
                rc = PTR_ERR(ce);
                goto out;
        }

        rc = 0;

        t = ce->ce_tgthint;

        if (unlikely(!strcasecmp(it->it_name, t->t_name)))
                goto out;

        list_for_each_entry(t, &ce->ce_tlist, t_list) {
                if (!strcasecmp(t->t_name, it->it_name)) {
                        ce->ce_tgthint = t;
                        cifs_dbg(FYI, "%s: new target hint: %s\n", __func__,
                                 it->it_name);
                        break;
                }
        }

out:
        mutex_unlock(&dfs_cache_list_lock);
        free_normalized_path(path, npath);
        return rc;
}

/**
 * dfs_cache_get_tgt_referral - returns a DFS referral (@ref) from a given
 * target iterator (@it).
 *
 * @path: path to lookup in DFS referral cache.
 * @it: DFS target iterator.
 * @ref: DFS referral pointer to set up the gathered information.
 *
 * Return zero if the DFS referral was set up correctly, otherwise non-zero.
 */
int dfs_cache_get_tgt_referral(const char *path,
                               const struct dfs_cache_tgt_iterator *it,
                               struct dfs_info3_param *ref)
{
        int rc;
        char *npath;
        struct dfs_cache_entry *ce;
        unsigned int h;

        if (!it || !ref)
                return -EINVAL;
        if (unlikely(!is_path_valid(path)))
                return -EINVAL;

        rc = get_normalized_path(path, &npath);
        if (rc)
                return rc;

        cifs_dbg(FYI, "%s: path: %s\n", __func__, npath);

        mutex_lock(&dfs_cache_list_lock);

        ce = find_cache_entry(npath, &h);
        if (IS_ERR(ce)) {
                rc = PTR_ERR(ce);
                goto out;
        }

        cifs_dbg(FYI, "%s: target name: %s\n", __func__, it->it_name);

        rc = setup_ref(path, ce, ref, it->it_name);

out:
        mutex_unlock(&dfs_cache_list_lock);
        free_normalized_path(path, npath);
        return rc;
}

static int dup_vol(struct smb_vol *vol, struct smb_vol *new)
{
        memcpy(new, vol, sizeof(*new));

        if (vol->username) {
                new->username = kstrndup(vol->username, strlen(vol->username),
                                        GFP_KERNEL);
                if (!new->username)
                        return -ENOMEM;
        }
        if (vol->password) {
                new->password = kstrndup(vol->password, strlen(vol->password),
                                         GFP_KERNEL);
                if (!new->password)
                        goto err_free_username;
        }
        if (vol->UNC) {
                cifs_dbg(FYI, "%s: vol->UNC: %s\n", __func__, vol->UNC);
                new->UNC = kstrndup(vol->UNC, strlen(vol->UNC), GFP_KERNEL);
                if (!new->UNC)
                        goto err_free_password;
        }
        if (vol->domainname) {
                new->domainname = kstrndup(vol->domainname,
                                          strlen(vol->domainname), GFP_KERNEL);
                if (!new->domainname)
                        goto err_free_unc;
        }
        if (vol->iocharset) {
                new->iocharset = kstrndup(vol->iocharset,
                                          strlen(vol->iocharset), GFP_KERNEL);
                if (!new->iocharset)
                        goto err_free_domainname;
        }
        if (vol->prepath) {
                cifs_dbg(FYI, "%s: vol->prepath: %s\n", __func__, vol->prepath);
                new->prepath = kstrndup(vol->prepath, strlen(vol->prepath),
                                        GFP_KERNEL);
                if (!new->prepath)
                        goto err_free_iocharset;
        }

        return 0;

err_free_iocharset:
        kfree(new->iocharset);
err_free_domainname:
        kfree(new->domainname);
err_free_unc:
        kfree(new->UNC);
err_free_password:
        kzfree(new->password);
err_free_username:
        kfree(new->username);
        kfree(new);
        return -ENOMEM;
}

/**
 * dfs_cache_add_vol - add a cifs volume during mount() that will be handled by
 * DFS cache refresh worker.
 *
 * @mntdata: mount data.
 * @vol: cifs volume.
 * @fullpath: origin full path.
 *
 * Return zero if volume was set up correctly, otherwise non-zero.
 */
int dfs_cache_add_vol(char *mntdata, struct smb_vol *vol, const char *fullpath)
{
        int rc;
        struct dfs_cache_vol_info *vi;

        if (!vol || !fullpath || !mntdata)
                return -EINVAL;

        cifs_dbg(FYI, "%s: fullpath: %s\n", __func__, fullpath);

        vi = kzalloc(sizeof(*vi), GFP_KERNEL);
        if (!vi)
                return -ENOMEM;

        vi->vi_fullpath = kstrndup(fullpath, strlen(fullpath), GFP_KERNEL);
        if (!vi->vi_fullpath) {
                rc = -ENOMEM;
                goto err_free_vi;
        }

        rc = dup_vol(vol, &vi->vi_vol);
        if (rc)
                goto err_free_fullpath;

        vi->vi_mntdata = mntdata;

        mutex_lock(&dfs_cache.dc_lock);
        list_add_tail(&vi->vi_list, &dfs_cache.dc_vol_list);
        mutex_unlock(&dfs_cache.dc_lock);
        return 0;

err_free_fullpath:
        kfree(vi->vi_fullpath);
err_free_vi:
        kfree(vi);
        return rc;
}

static inline struct dfs_cache_vol_info *find_vol(const char *fullpath)
{
        struct dfs_cache_vol_info *vi;

        list_for_each_entry(vi, &dfs_cache.dc_vol_list, vi_list) {
                cifs_dbg(FYI, "%s: vi->vi_fullpath: %s\n", __func__,
                         vi->vi_fullpath);
                if (!strcasecmp(vi->vi_fullpath, fullpath))
                        return vi;
        }
        return ERR_PTR(-ENOENT);
}

/**
 * dfs_cache_update_vol - update vol info in DFS cache after failover
 *
 * @fullpath: fullpath to look up in volume list.
 * @server: TCP ses pointer.
 *
 * Return zero if volume was updated, otherwise non-zero.
 */
int dfs_cache_update_vol(const char *fullpath, struct TCP_Server_Info *server)
{
        int rc;
        struct dfs_cache_vol_info *vi;

        if (!fullpath || !server)
                return -EINVAL;

        cifs_dbg(FYI, "%s: fullpath: %s\n", __func__, fullpath);

        mutex_lock(&dfs_cache.dc_lock);

        vi = find_vol(fullpath);
        if (IS_ERR(vi)) {
                rc = PTR_ERR(vi);
                goto out;
        }

        cifs_dbg(FYI, "%s: updating volume info\n", __func__);
        memcpy(&vi->vi_vol.dstaddr, &server->dstaddr,
               sizeof(vi->vi_vol.dstaddr));
        rc = 0;

out:
        mutex_unlock(&dfs_cache.dc_lock);
        return rc;
}

/**
 * dfs_cache_del_vol - remove volume info in DFS cache during umount()
 *
 * @fullpath: fullpath to look up in volume list.
 */
void dfs_cache_del_vol(const char *fullpath)
{
        struct dfs_cache_vol_info *vi;

        if (!fullpath || !*fullpath)
                return;

        cifs_dbg(FYI, "%s: fullpath: %s\n", __func__, fullpath);

        mutex_lock(&dfs_cache.dc_lock);
        vi = find_vol(fullpath);
        if (!IS_ERR(vi))
                free_vol(vi);
        mutex_unlock(&dfs_cache.dc_lock);
}

/* Get all tcons that are within a DFS namespace and can be refreshed */
static void get_tcons(struct TCP_Server_Info *server, struct list_head *head)
{
        struct cifs_ses *ses;
        struct cifs_tcon *tcon;

        INIT_LIST_HEAD(head);

        spin_lock(&cifs_tcp_ses_lock);
        list_for_each_entry(ses, &server->smb_ses_list, smb_ses_list) {
                list_for_each_entry(tcon, &ses->tcon_list, tcon_list) {
                        if (!tcon->need_reconnect && !tcon->need_reopen_files &&
                            tcon->dfs_path) {
                                tcon->tc_count++;
                                list_add_tail(&tcon->ulist, head);
                        }
                }
                if (ses->tcon_ipc && !ses->tcon_ipc->need_reconnect &&
                    ses->tcon_ipc->dfs_path) {
                        list_add_tail(&ses->tcon_ipc->ulist, head);
                }
        }
        spin_unlock(&cifs_tcp_ses_lock);
}

static inline bool is_dfs_link(const char *path)
{
        char *s;

        s = strchr(path + 1, '\\');
        if (!s)
                return false;
        return !!strchr(s + 1, '\\');
}

static inline char *get_dfs_root(const char *path)
{
        char *s, *npath;

        s = strchr(path + 1, '\\');
        if (!s)
                return ERR_PTR(-EINVAL);

        s = strchr(s + 1, '\\');
        if (!s)
                return ERR_PTR(-EINVAL);

        npath = kstrndup(path, s - path, GFP_KERNEL);
        if (!npath)
                return ERR_PTR(-ENOMEM);

        return npath;
}

/* Find root SMB session out of a DFS link path */
static struct cifs_ses *find_root_ses(struct dfs_cache_vol_info *vi,
                                      struct cifs_tcon *tcon, const char *path)
{
        char *rpath;
        int rc;
        struct dfs_info3_param ref = {0};
        char *mdata = NULL, *devname = NULL;
        bool is_smb3 = tcon->ses->server->vals->header_preamble_size == 0;
        struct TCP_Server_Info *server;
        struct cifs_ses *ses;
        struct smb_vol vol;

        rpath = get_dfs_root(path);
        if (IS_ERR(rpath))
                return ERR_CAST(rpath);

        memset(&vol, 0, sizeof(vol));

        rc = dfs_cache_noreq_find(rpath, &ref, NULL);
        if (rc) {
                ses = ERR_PTR(rc);
                goto out;
        }

        mdata = cifs_compose_mount_options(vi->vi_mntdata, rpath, &ref,
                                           &devname);
        free_dfs_info_param(&ref);

        if (IS_ERR(mdata)) {
                ses = ERR_CAST(mdata);
                mdata = NULL;
                goto out;
        }

        rc = cifs_setup_volume_info(&vol, mdata, devname, is_smb3);
        kfree(devname);

        if (rc) {
                ses = ERR_PTR(rc);
                goto out;
        }

        server = cifs_find_tcp_session(&vol);
        if (IS_ERR_OR_NULL(server)) {
                ses = ERR_PTR(-EHOSTDOWN);
                goto out;
        }
        if (server->tcpStatus != CifsGood) {
                cifs_put_tcp_session(server, 0);
                ses = ERR_PTR(-EHOSTDOWN);
                goto out;
        }

        ses = cifs_get_smb_ses(server, &vol);

out:
        cifs_cleanup_volume_info_contents(&vol);
        kfree(mdata);
        kfree(rpath);

        return ses;
}

/* Refresh DFS cache entry from a given tcon */
static void do_refresh_tcon(struct dfs_cache *dc, struct dfs_cache_vol_info *vi,
                            struct cifs_tcon *tcon)
{
        int rc = 0;
        unsigned int xid;
        char *path, *npath;
        unsigned int h;
        struct dfs_cache_entry *ce;
        struct dfs_info3_param *refs = NULL;
        int numrefs = 0;
        struct cifs_ses *root_ses = NULL, *ses;

        xid = get_xid();

        path = tcon->dfs_path + 1;

        rc = get_normalized_path(path, &npath);
        if (rc)
                goto out;

        mutex_lock(&dfs_cache_list_lock);
        ce = find_cache_entry(npath, &h);
        mutex_unlock(&dfs_cache_list_lock);

        if (IS_ERR(ce)) {
                rc = PTR_ERR(ce);
                goto out;
        }

        if (!cache_entry_expired(ce))
                goto out;

        /* If it's a DFS Link, then use root SMB session for refreshing it */
        if (is_dfs_link(npath)) {
                ses = root_ses = find_root_ses(vi, tcon, npath);
                if (IS_ERR(ses)) {
                        rc = PTR_ERR(ses);
                        root_ses = NULL;
                        goto out;
                }
        } else {
                ses = tcon->ses;
        }

        if (unlikely(!ses->server->ops->get_dfs_refer)) {
                rc = -EOPNOTSUPP;
        } else {
                rc = ses->server->ops->get_dfs_refer(xid, ses, path, &refs,
                                                     &numrefs, dc->dc_nlsc,
                                                     tcon->remap);
                if (!rc) {
                        mutex_lock(&dfs_cache_list_lock);
                        ce = __update_cache_entry(npath, refs, numrefs);
                        mutex_unlock(&dfs_cache_list_lock);
                        dump_refs(refs, numrefs);
                        free_dfs_info_array(refs, numrefs);
                        if (IS_ERR(ce))
                                rc = PTR_ERR(ce);
                }
        }

out:
        if (root_ses)
                cifs_put_smb_ses(root_ses);

        free_xid(xid);
        free_normalized_path(path, npath);
}

/*
 * Worker that will refresh DFS cache based on lowest TTL value from a DFS
 * referral.
 */
static void refresh_cache_worker(struct work_struct *work)
{
        struct dfs_cache *dc = container_of(work, struct dfs_cache,
                                            dc_refresh.work);
        struct dfs_cache_vol_info *vi;
        struct TCP_Server_Info *server;
        LIST_HEAD(list);
        struct cifs_tcon *tcon, *ntcon;

        mutex_lock(&dc->dc_lock);

        list_for_each_entry(vi, &dc->dc_vol_list, vi_list) {
                server = cifs_find_tcp_session(&vi->vi_vol);
                if (IS_ERR_OR_NULL(server))
                        continue;
                if (server->tcpStatus != CifsGood)
                        goto next;
                get_tcons(server, &list);
                list_for_each_entry_safe(tcon, ntcon, &list, ulist) {
                        do_refresh_tcon(dc, vi, tcon);
                        list_del_init(&tcon->ulist);
                        cifs_put_tcon(tcon);
                }
next:
                cifs_put_tcp_session(server, 0);
        }
        queue_delayed_work(cifsiod_wq, &dc->dc_refresh, dc->dc_ttl * HZ);
        mutex_unlock(&dc->dc_lock);
}