path: root/fs/cifs/dfs_cache.c

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

#include <linux/jhash.h>
#include <linux/ktime.h>
#include <linux/slab.h>
#include <linux/proc_fs.h>
#include <linux/nls.h>
#include <linux/workqueue.h>
#include <linux/uuid.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 "dns_resolve.h"

#include "dfs_cache.h"

#define CACHE_HTABLE_SIZE 32
#define CACHE_MAX_ENTRIES 64
#define CACHE_MIN_TTL 120 /* 2 minutes */

#define IS_DFS_INTERLINK(v) (((v) & DFSREF_REFERRAL_SERVER) && !((v) & DFSREF_STORAGE_SERVER))

struct cache_dfs_tgt {
	char *name;
	int path_consumed;
	struct list_head list;
};

struct cache_entry {
	struct hlist_node hlist;
	const char *path;
	int hdr_flags; /* RESP_GET_DFS_REFERRAL.ReferralHeaderFlags */
	int ttl; /* DFS_REREFERRAL_V3.TimeToLive */
	int srvtype; /* DFS_REREFERRAL_V3.ServerType */
	int ref_flags; /* DFS_REREFERRAL_V3.ReferralEntryFlags */
	struct timespec64 etime;
	int path_consumed; /* RESP_GET_DFS_REFERRAL.PathConsumed */
	int numtgts;
	struct list_head tlist;
	struct cache_dfs_tgt *tgthint;
};

/* List of referral server sessions per dfs mount */
struct mount_group {
	struct list_head list;
	uuid_t id;
	struct cifs_ses *sessions[CACHE_MAX_ENTRIES];
	int num_sessions;
	spinlock_t lock;
	struct list_head refresh_list;
	struct kref refcount;
};

static struct kmem_cache *cache_slab __read_mostly;
static struct workqueue_struct *dfscache_wq __read_mostly;

static int cache_ttl;
static DEFINE_SPINLOCK(cache_ttl_lock);

static struct nls_table *cache_cp;

/*
 * Number of entries in the cache
 */
static atomic_t cache_count;

static struct hlist_head cache_htable[CACHE_HTABLE_SIZE];
static DECLARE_RWSEM(htable_rw_lock);

static LIST_HEAD(mount_group_list);
static DEFINE_MUTEX(mount_group_list_lock);

static void refresh_cache_worker(struct work_struct *work);

static DECLARE_DELAYED_WORK(refresh_task, refresh_cache_worker);

static void get_ipc_unc(const char *ref_path, char *ipc, size_t ipclen)
{
	const char *host;
	size_t len;

	extract_unc_hostname(ref_path, &host, &len);
	scnprintf(ipc, ipclen, "\\\\%.*s\\IPC$", (int)len, host);
}

static struct cifs_ses *find_ipc_from_server_path(struct cifs_ses **ses, const char *path)
{
	char unc[SERVER_NAME_LENGTH + sizeof("//x/IPC$")] = {0};

	get_ipc_unc(path, unc, sizeof(unc));
	for (; *ses; ses++) {
		if (!strcasecmp(unc, (*ses)->tcon_ipc->treeName))
			return *ses;
	}
	return ERR_PTR(-ENOENT);
}

static void __mount_group_release(struct mount_group *mg)
{
	int i;

	for (i = 0; i < mg->num_sessions; i++)
		cifs_put_smb_se