/* AFS cell and server record management
 *
 * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/key.h>
#include <linux/ctype.h>
#include <linux/dns_resolver.h>
#include <linux/sched.h>
#include <keys/rxrpc-type.h>
#include "internal.h"

DECLARE_RWSEM(afs_proc_cells_sem);
LIST_HEAD(afs_proc_cells);

static LIST_HEAD(afs_cells);
static DEFINE_RWLOCK(afs_cells_lock);
static DECLARE_RWSEM(afs_cells_sem); /* add/remove serialisation */
static DECLARE_WAIT_QUEUE_HEAD(afs_cells_freeable_wq);
static struct afs_cell *afs_cell_root;

/*
 * allocate a cell record and fill in its name, VL server address list and
 * allocate an anonymous key
 */
static struct afs_cell *afs_cell_alloc(const char *name, unsigned namelen,
                                       char *vllist)
{
        struct afs_cell *cell;
        struct key *key;
        char keyname[4 + AFS_MAXCELLNAME + 1], *cp, *dp, *next;
        char  *dvllist = NULL, *_vllist = NULL;
        char  delimiter = ':';
        int ret;

        _enter("%*.*s,%s", namelen, namelen, name ?: "", vllist);

        BUG_ON(!name); /* TODO: want to look up "this cell" in the cache */

        if (namelen > AFS_MAXCELLNAME) {
                _leave(" = -ENAMETOOLONG");
                return ERR_PTR(-ENAMETOOLONG);
        }

        /* allocate and initialise a cell record */
        cell = kzalloc(sizeof(struct afs_cell) + namelen + 1, GFP_KERNEL);
        if (!cell) {
                _leave(" = -ENOMEM");
                return ERR_PTR(-ENOMEM);
        }

        memcpy(cell->name, name, namelen);
        cell->name[namelen] = 0;

        atomic_set(&cell->usage, 1);
        INIT_LIST_HEAD(&cell->link);
        rwlock_init(&cell->servers_lock);
        INIT_LIST_HEAD(&cell->servers);
        init_rwsem(&cell->vl_sem);
        INIT_LIST_HEAD(&cell->vl_list);
        spin_lock_init(&cell->vl_lock);

        /* if the ip address is invalid, try dns query */
        if (!vllist || strlen(vllist) < 7) {
                ret = dns_query("afsdb", name, namelen, "ipv4", &dvllist, NULL);
                if (ret < 0) {
                        if (ret == -ENODATA || ret == -EAGAIN || ret == -ENOKEY)
                                /* translate these errors into something
                                 * userspace might understand */
                                ret = -EDESTADDRREQ;
                        _leave(" = %d", ret);
                        return ERR_PTR(ret);
                }
                _vllist = dvllist;

                /* change the delimiter for user-space reply */
                delimiter = ',';

        } else {
                _vllist = vllist;
        }

        /* fill in the VL server list from the rest of the string */
        do {
                unsigned a, b, c, d;

                next = strchr(_vllist, delimiter);
                if (next)
                        *next++ = 0;

                if (sscanf(_vllist, "%u.%u.%u.%u", &a, &b, &c, &d) != 4)
                        goto bad_address;

                if (a > 255 || b > 255 || c > 255 || d > 255)
                        goto bad_address;

                cell->vl_addrs[cell->vl_naddrs++].s_addr =
                        htonl((a << 24) | (b << 16) | (c << 8) | d);

        } while (cell->vl_naddrs < AFS_CELL_MAX_ADDRS && (_vllist = next));

        /* create a key to represent an anonymous user */
        memcpy(keyname, "afs@", 4);
        dp = keyname + 4;
        cp = cell->name;
        do {
                *dp++ = toupper(*cp);
        } while (*cp++);

        key = rxrpc_get_null_key(keyname);
        if (IS_ERR(key)) {
                _debug("no key");
                ret = PTR_ERR(key);
                goto error;
        }
        cell->anonymous_key = key;

        _debug("anon key %p{%x}",
               cell->anonymous_key, key_serial(cell->anonymous_key));

        _leave(" = %p", cell);
        return cell;

bad_address:
        printk(KERN_ERR "kAFS: bad VL server IP address\n");
        ret = -EINVAL;
error:
        key_put(cell->anonymous_key);
        kfree(dvllist);
        kfree(cell);
        _leave(" = %d", ret);
        return ERR_PTR(ret);
}

/*
 * afs_cell_crate() - create a cell record
 * @name:       is the name of the cell.
 * @namsesz:    is the strlen of the cell name.
 * @vllist:     is a colon separated list of IP addresses in "a.b.c.d" format.
 * @retref:     is T to return the cell reference when the cell exists.
 */
struct afs_cell *afs_cell_create(const char *name, unsigned namesz,
                                 char *vllist, bool retref)
{
        struct afs_cell *cell;
        int ret;

        _enter("%*.*s,%s", namesz, namesz, name ?: "", vllist);

        down_write(&afs_cells_sem);
        read_lock(&afs_cells_lock);
        list_for_each_entry(cell, &afs_cells, link) {
                if (strncasecmp(cell->name, name, namesz) == 0)
                        goto duplicate_name;
        }
        read_unlock(&afs_cells_lock);

        cell = afs_cell_alloc(name, namesz, vllist);
        if (IS_ERR(cell)) {
                _leave(" = %ld", PTR_ERR(cell));
                up_write(&afs_cells_sem);
                return cell;
        }

        /* add a proc directory for this cell */
        ret = afs_proc_cell_setup(cell);
        if (ret < 0)
                goto error;

#ifdef CONFIG_AFS_FSCACHE
        /* put it up for caching (this never returns an error) */
        cell->cache = fscache_acquire_cookie(afs_cache_netfs.primary_index,
                                             &afs_cell_cache_index_def,
                                             cell, true);
#endif

        /* add to the cell lists */
        write_lock(&afs_cells_lock);
        list_add_tail(&cell->link, &afs_cells);
        write_unlock(&afs_cells_lock);

        down_write(&afs_proc_cells_sem);
        list_add_tail(&cell->proc_link, &afs_proc_cells);
        up_write(&afs_proc_cells_sem);
        up_write(&afs_cells_sem);

        _leave(" = %p", cell);
        return cell;

error:
        up_write(&afs_cells_sem);
        key_put(cell->anonymous_key);
        kfree(cell);
        _leave(" = %d", ret);
        return ERR_PTR(ret);

duplicate_name:
        if (retref && !IS_ERR(cell))
                afs_get_cell(cell);

        read_unlock(&afs_cells_lock);
        up_write(&afs_cells_sem);

        if (retref) {
                _leave(" = %p", cell);
                return cell;
        }

        _leave(" = -EEXIST");
        return ERR_PTR(-EEXIST);
}

/*
 * set the root cell information
 * - can be called with a module parameter string
 * - can be called from a write to /proc/fs/afs/rootcell
 */
int afs_cell_init(char *rootcell)
{
        struct afs_cell *old_root, *new_root;
        char *cp;

        _enter("");

        if (!rootcell) {
                /* module is loaded with no parameters, or built statically.
                 * - in the future we might initialize cell DB here.
                 */
                _leave(" = 0 [no root]");
                return 0;
        }

        cp = strchr(rootcell, ':');
        if (!cp)
                _debug("kAFS: no VL server IP addresses specified");
        else
                *cp++ = 0;

        /* allocate a cell record for the root cell */
        new_root = afs_cell_create(rootcell, strlen(rootcell), cp, false);
        if (IS_ERR(new_root)) {
                _leave(" = %ld", PTR_ERR(new_root));
                return PTR_ERR(new_root);
        }

        /* install the new cell */
        write_lock(&afs_cells_lock);
        old_root = afs_cell_root;
        afs_cell_root = new_root;
        write_unlock(&afs_cells_lock);
        afs_put_cell(old_root);

        _leave(" = 0");
        return 0;
}

/*
 * lookup a cell record
 */
struct afs_cell *afs_cell_lookup(const char *name, unsigned namesz,
                                 bool dns_cell)
{
        struct afs_cell *cell;

        _enter("\"%*.*s\",", namesz, namesz, name ?: "");

        down_read(&afs_cells_sem);
        read_lock(&afs_cells_lock);

        if (name) {
                /* if the cell was named, look for it in the cell record list */
                list_for_each_entry(cell, &afs_cells, link) {
                        if (strncmp(cell->name, name, namesz) == 0) {
                                afs_get_cell(cell);
                                goto found;
                        }
                }
                cell = ERR_PTR(-ENOENT);
                if (dns_cell)
                        goto create_cell;
        found:
                ;
        } else {
                cell = afs_cell_root;
                if (!cell) {
                        /* this should not happen unless user tries to mount
                         * when root cell is not set. Return an impossibly
                         * bizarre errno to alert the user. Things like
                         * ENOENT might be "more appropriate" but they happen
                         * for other reasons.
                         */
                        cell = ERR_PTR(-EDESTADDRREQ);
                } else {
                        afs_get_cell(cell);
                }

        }

        read_unlock(&afs_cells_lock);
        up_read(&afs_cells_sem);
        _leave(" = %p", cell);
        return cell;

create_cell:
        read_unlock(&afs_cells_lock);
        up_read(&afs_cells_sem);

        cell = afs_cell_create(name, namesz, NULL, true);

        _leave(" = %p", cell);
        return cell;
}

#if 0
/*
 * try and get a cell record
 */
struct afs_cell *afs_get_cell_maybe(struct afs_cell *cell)
{
        write_lock(&afs_cells_lock);

        if (cell && !list_empty(&cell->link))
                afs_get_cell(cell);
        else
                cell = NULL;

        write_unlock(&afs_cells_lock);
        return cell;
}
#endif  /*  0  */

/*
 * destroy a cell record
 */
void afs_put_cell(struct afs_cell *cell)
{
        if (!cell)
                return;

        _enter("%p{%d,%s}", cell, atomic_read(&cell->usage), cell->name);

        ASSERTCMP(atomic_read(&cell->usage), >, 0);

        /* to prevent a race, the decrement and the dequeue must be effectively
         * atomic */
        write_lock(&afs_cells_lock);

        if (likely(!atomic_dec_and_test(&cell->usage))) {
                write_unlock(&afs_cells_lock);
                _leave("");
                return;
        }

        ASSERT(list_empty(&cell->servers));
        ASSERT(list_empty(&cell->vl_list));

        write_unlock(&afs_cells_lock);

        wake_up(&afs_cells_freeable_wq);

        _leave(" [unused]");
}

/*
 * destroy a cell record
 * - must be called with the afs_cells_sem write-locked
 * - cell->link should have been broken by the caller
 */
static void afs_cell_destroy(struct afs_cell *cell)
{
        _enter("%p{%d,%s}", cell, atomic_read(&cell->usage), cell->name);

        ASSERTCMP(atomic_read(&cell->usage), >=, 0);
        ASSERT(list_empty(&cell->link));

        /* wait for everyone to stop using the cell */
        if (atomic_read(&cell->usage) > 0) {
                DECLARE_WAITQUEUE(myself, current);

                _debug("wait for cell %s", cell->name);
                set_current_state(TASK_UNINTERRUPTIBLE);
                add_wait_queue(&afs_cells_freeable_wq, &myself);

                while (atomic_read(&cell->usage) > 0) {
                        schedule();
                        set_current_state(TASK_UNINTERRUPTIBLE);
                }

                remove_wait_queue(&afs_cells_freeable_wq, &myself);
                set_current_state(TASK_RUNNING);
        }

        _debug("cell dead");
        ASSERTCMP(atomic_read(&cell->usage), ==, 0);
        ASSERT(list_empty(&cell->servers));
        ASSERT(list_empty(&cell->vl_list));

        afs_proc_cell_remove(cell);

        down_write(&afs_proc_cells_sem);
        list_del_init(&cell->proc_link);
        up_write(&afs_proc_cells_sem);

#ifdef CONFIG_AFS_FSCACHE
        fscache_relinquish_cookie(cell->cache, 0);
#endif
        key_put(cell->anonymous_key);
        kfree(cell);

        _leave(" [destroyed]");
}

/*
 * purge in-memory cell database on module unload or afs_init() failure
 * - the timeout daemon is stopped before calling this
 */
void afs_cell_purge(void)
{
        struct afs_cell *cell;

        _enter("");

        afs_put_cell(afs_cell_root);

        down_write(&afs_cells_sem);

        while (!list_empty(&afs_cells)) {
                cell = NULL;

                /* remove the next cell from the front of the list */
                write_lock(&afs_cells_lock);

                if (!list_empty(&afs_cells)) {
                        cell = list_entry(afs_cells.next,
                                          struct afs_cell, link);
                        list_del_init(&cell->link);
                }

                write_unlock(&afs_cells_lock);

                if (cell) {
                        _debug("PURGING CELL %s (%d)",
                               cell->name, atomic_read(&cell->usage));

                        /* now the cell should be left with no references */
                        afs_cell_destroy(cell);
                }
        }

        up_write(&afs_cells_sem);
        _leave("");
}