![Wang Lei](/assets/img/avatar_default.png)
Add DNS query support for AFS so that it can get the IP addresses of Volume Location servers from the DNS using an AFSDB record. This requires userspace support. /etc/request-key.conf must be configured to invoke a helper for dns_resolver type keys with a subtype of "afsdb:" in the description. Signed-off-by: Wang Lei <wang840925@gmail.com> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Steve French <sfrench@us.ibm.com>
433 lines
9.6 KiB
C
433 lines
9.6 KiB
C
/* AFS cell and server record management
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*
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* Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/key.h>
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#include <linux/ctype.h>
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#include <linux/dns_resolver.h>
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#include <linux/sched.h>
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#include <keys/rxrpc-type.h>
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#include "internal.h"
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DECLARE_RWSEM(afs_proc_cells_sem);
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LIST_HEAD(afs_proc_cells);
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static LIST_HEAD(afs_cells);
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static DEFINE_RWLOCK(afs_cells_lock);
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static DECLARE_RWSEM(afs_cells_sem); /* add/remove serialisation */
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static DECLARE_WAIT_QUEUE_HEAD(afs_cells_freeable_wq);
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static struct afs_cell *afs_cell_root;
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/*
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* allocate a cell record and fill in its name, VL server address list and
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* allocate an anonymous key
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*/
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static struct afs_cell *afs_cell_alloc(const char *name, char *vllist)
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{
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struct afs_cell *cell;
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struct key *key;
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size_t namelen;
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char keyname[4 + AFS_MAXCELLNAME + 1], *cp, *dp, *next;
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char *dvllist = NULL, *_vllist = NULL;
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char delimiter = ':';
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int ret;
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_enter("%s,%s", name, vllist);
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BUG_ON(!name); /* TODO: want to look up "this cell" in the cache */
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namelen = strlen(name);
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if (namelen > AFS_MAXCELLNAME) {
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_leave(" = -ENAMETOOLONG");
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return ERR_PTR(-ENAMETOOLONG);
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}
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/* allocate and initialise a cell record */
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cell = kzalloc(sizeof(struct afs_cell) + namelen + 1, GFP_KERNEL);
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if (!cell) {
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_leave(" = -ENOMEM");
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return ERR_PTR(-ENOMEM);
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}
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memcpy(cell->name, name, namelen);
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cell->name[namelen] = 0;
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atomic_set(&cell->usage, 1);
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INIT_LIST_HEAD(&cell->link);
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rwlock_init(&cell->servers_lock);
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INIT_LIST_HEAD(&cell->servers);
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init_rwsem(&cell->vl_sem);
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INIT_LIST_HEAD(&cell->vl_list);
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spin_lock_init(&cell->vl_lock);
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/* if the ip address is invalid, try dns query */
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if (!vllist || strlen(vllist) < 7) {
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ret = dns_query("afsdb", name, namelen, "ipv4", &dvllist, NULL);
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if (ret < 0) {
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_leave(" = %d", ret);
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return ERR_PTR(ret);
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}
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_vllist = dvllist;
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/* change the delimiter for user-space reply */
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delimiter = ',';
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} else {
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_vllist = vllist;
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}
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/* fill in the VL server list from the rest of the string */
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do {
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unsigned a, b, c, d;
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next = strchr(_vllist, delimiter);
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if (next)
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*next++ = 0;
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if (sscanf(_vllist, "%u.%u.%u.%u", &a, &b, &c, &d) != 4)
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goto bad_address;
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if (a > 255 || b > 255 || c > 255 || d > 255)
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goto bad_address;
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cell->vl_addrs[cell->vl_naddrs++].s_addr =
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htonl((a << 24) | (b << 16) | (c << 8) | d);
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} while (cell->vl_naddrs < AFS_CELL_MAX_ADDRS && (_vllist = next));
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/* create a key to represent an anonymous user */
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memcpy(keyname, "afs@", 4);
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dp = keyname + 4;
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cp = cell->name;
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do {
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*dp++ = toupper(*cp);
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} while (*cp++);
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key = rxrpc_get_null_key(keyname);
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if (IS_ERR(key)) {
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_debug("no key");
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ret = PTR_ERR(key);
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goto error;
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}
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cell->anonymous_key = key;
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_debug("anon key %p{%x}",
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cell->anonymous_key, key_serial(cell->anonymous_key));
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_leave(" = %p", cell);
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return cell;
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bad_address:
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printk(KERN_ERR "kAFS: bad VL server IP address\n");
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ret = -EINVAL;
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error:
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key_put(cell->anonymous_key);
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kfree(dvllist);
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kfree(cell);
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_leave(" = %d", ret);
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return ERR_PTR(ret);
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}
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/*
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* create a cell record
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* - "name" is the name of the cell
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* - "vllist" is a colon separated list of IP addresses in "a.b.c.d" format
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*/
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struct afs_cell *afs_cell_create(const char *name, char *vllist)
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{
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struct afs_cell *cell;
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int ret;
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_enter("%s,%s", name, vllist);
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down_write(&afs_cells_sem);
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read_lock(&afs_cells_lock);
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list_for_each_entry(cell, &afs_cells, link) {
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if (strcasecmp(cell->name, name) == 0)
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goto duplicate_name;
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}
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read_unlock(&afs_cells_lock);
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cell = afs_cell_alloc(name, vllist);
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if (IS_ERR(cell)) {
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_leave(" = %ld", PTR_ERR(cell));
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up_write(&afs_cells_sem);
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return cell;
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}
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/* add a proc directory for this cell */
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ret = afs_proc_cell_setup(cell);
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if (ret < 0)
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goto error;
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#ifdef CONFIG_AFS_FSCACHE
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/* put it up for caching (this never returns an error) */
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cell->cache = fscache_acquire_cookie(afs_cache_netfs.primary_index,
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&afs_cell_cache_index_def,
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cell);
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#endif
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/* add to the cell lists */
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write_lock(&afs_cells_lock);
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list_add_tail(&cell->link, &afs_cells);
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write_unlock(&afs_cells_lock);
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down_write(&afs_proc_cells_sem);
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list_add_tail(&cell->proc_link, &afs_proc_cells);
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up_write(&afs_proc_cells_sem);
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up_write(&afs_cells_sem);
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_leave(" = %p", cell);
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return cell;
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error:
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up_write(&afs_cells_sem);
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key_put(cell->anonymous_key);
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kfree(cell);
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_leave(" = %d", ret);
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return ERR_PTR(ret);
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duplicate_name:
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read_unlock(&afs_cells_lock);
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up_write(&afs_cells_sem);
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return ERR_PTR(-EEXIST);
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}
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/*
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* set the root cell information
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* - can be called with a module parameter string
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* - can be called from a write to /proc/fs/afs/rootcell
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*/
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int afs_cell_init(char *rootcell)
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{
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struct afs_cell *old_root, *new_root;
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char *cp;
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_enter("");
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if (!rootcell) {
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/* module is loaded with no parameters, or built statically.
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* - in the future we might initialize cell DB here.
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*/
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_leave(" = 0 [no root]");
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return 0;
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}
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cp = strchr(rootcell, ':');
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if (!cp)
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_debug("kAFS: no VL server IP addresses specified");
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else
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*cp++ = 0;
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/* allocate a cell record for the root cell */
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new_root = afs_cell_create(rootcell, cp);
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if (IS_ERR(new_root)) {
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_leave(" = %ld", PTR_ERR(new_root));
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return PTR_ERR(new_root);
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}
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/* install the new cell */
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write_lock(&afs_cells_lock);
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old_root = afs_cell_root;
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afs_cell_root = new_root;
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write_unlock(&afs_cells_lock);
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afs_put_cell(old_root);
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_leave(" = 0");
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return 0;
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}
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/*
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* lookup a cell record
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*/
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struct afs_cell *afs_cell_lookup(const char *name, unsigned namesz)
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{
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struct afs_cell *cell;
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_enter("\"%*.*s\",", namesz, namesz, name ? name : "");
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down_read(&afs_cells_sem);
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read_lock(&afs_cells_lock);
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if (name) {
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/* if the cell was named, look for it in the cell record list */
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list_for_each_entry(cell, &afs_cells, link) {
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if (strncmp(cell->name, name, namesz) == 0) {
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afs_get_cell(cell);
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goto found;
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}
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}
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cell = ERR_PTR(-ENOENT);
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found:
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;
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} else {
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cell = afs_cell_root;
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if (!cell) {
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/* this should not happen unless user tries to mount
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* when root cell is not set. Return an impossibly
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* bizzare errno to alert the user. Things like
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* ENOENT might be "more appropriate" but they happen
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* for other reasons.
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*/
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cell = ERR_PTR(-EDESTADDRREQ);
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} else {
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afs_get_cell(cell);
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}
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}
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read_unlock(&afs_cells_lock);
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up_read(&afs_cells_sem);
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_leave(" = %p", cell);
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return cell;
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}
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#if 0
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/*
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* try and get a cell record
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*/
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struct afs_cell *afs_get_cell_maybe(struct afs_cell *cell)
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{
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write_lock(&afs_cells_lock);
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if (cell && !list_empty(&cell->link))
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afs_get_cell(cell);
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else
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cell = NULL;
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write_unlock(&afs_cells_lock);
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return cell;
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}
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#endif /* 0 */
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/*
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* destroy a cell record
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*/
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void afs_put_cell(struct afs_cell *cell)
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{
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if (!cell)
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return;
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_enter("%p{%d,%s}", cell, atomic_read(&cell->usage), cell->name);
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ASSERTCMP(atomic_read(&cell->usage), >, 0);
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/* to prevent a race, the decrement and the dequeue must be effectively
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* atomic */
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write_lock(&afs_cells_lock);
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if (likely(!atomic_dec_and_test(&cell->usage))) {
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write_unlock(&afs_cells_lock);
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_leave("");
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return;
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}
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ASSERT(list_empty(&cell->servers));
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ASSERT(list_empty(&cell->vl_list));
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write_unlock(&afs_cells_lock);
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wake_up(&afs_cells_freeable_wq);
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_leave(" [unused]");
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}
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/*
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* destroy a cell record
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* - must be called with the afs_cells_sem write-locked
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* - cell->link should have been broken by the caller
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*/
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static void afs_cell_destroy(struct afs_cell *cell)
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{
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_enter("%p{%d,%s}", cell, atomic_read(&cell->usage), cell->name);
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ASSERTCMP(atomic_read(&cell->usage), >=, 0);
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ASSERT(list_empty(&cell->link));
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/* wait for everyone to stop using the cell */
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if (atomic_read(&cell->usage) > 0) {
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DECLARE_WAITQUEUE(myself, current);
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_debug("wait for cell %s", cell->name);
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set_current_state(TASK_UNINTERRUPTIBLE);
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add_wait_queue(&afs_cells_freeable_wq, &myself);
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while (atomic_read(&cell->usage) > 0) {
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schedule();
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set_current_state(TASK_UNINTERRUPTIBLE);
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}
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remove_wait_queue(&afs_cells_freeable_wq, &myself);
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set_current_state(TASK_RUNNING);
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}
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_debug("cell dead");
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ASSERTCMP(atomic_read(&cell->usage), ==, 0);
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ASSERT(list_empty(&cell->servers));
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ASSERT(list_empty(&cell->vl_list));
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afs_proc_cell_remove(cell);
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down_write(&afs_proc_cells_sem);
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list_del_init(&cell->proc_link);
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up_write(&afs_proc_cells_sem);
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#ifdef CONFIG_AFS_FSCACHE
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fscache_relinquish_cookie(cell->cache, 0);
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#endif
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key_put(cell->anonymous_key);
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kfree(cell);
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_leave(" [destroyed]");
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}
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/*
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* purge in-memory cell database on module unload or afs_init() failure
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* - the timeout daemon is stopped before calling this
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*/
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void afs_cell_purge(void)
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{
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struct afs_cell *cell;
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_enter("");
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afs_put_cell(afs_cell_root);
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down_write(&afs_cells_sem);
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while (!list_empty(&afs_cells)) {
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cell = NULL;
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/* remove the next cell from the front of the list */
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write_lock(&afs_cells_lock);
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if (!list_empty(&afs_cells)) {
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cell = list_entry(afs_cells.next,
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struct afs_cell, link);
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list_del_init(&cell->link);
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}
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write_unlock(&afs_cells_lock);
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if (cell) {
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_debug("PURGING CELL %s (%d)",
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cell->name, atomic_read(&cell->usage));
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/* now the cell should be left with no references */
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afs_cell_destroy(cell);
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}
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}
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up_write(&afs_cells_sem);
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_leave("");
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}
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