fs/nfs/dns_resolve.c

   1 /*
   2  * linux/fs/nfs/dns_resolve.c
   3  *
   4  * Copyright (c) 2009 Trond Myklebust <Trond.Myklebust@netapp.com>
   5  *
   6  * Resolves DNS hostnames into valid ip addresses
   7  */
   8
   9 #ifdef CONFIG_NFS_USE_KERNEL_DNS
  10
  11 #include <linux/module.h>
  12 #include <linux/sunrpc/clnt.h>
  13 #include <linux/sunrpc/addr.h>
  14 #include <linux/dns_resolver.h>
  15 #include "dns_resolve.h"
  16
  17 ssize_t nfs_dns_resolve_name(struct net *net, char *name, size_t namelen,
  18                 struct sockaddr *sa, size_t salen)
  19 {
  20         ssize_t ret;
  21         char *ip_addr = NULL;
  22         int ip_len;
  23
  24         ip_len = dns_query(NULL, name, namelen, NULL, &ip_addr, NULL);
  25         if (ip_len > 0)
  26                 ret = rpc_pton(net, ip_addr, ip_len, sa, salen);
  27         else
  28                 ret = -ESRCH;
  29         kfree(ip_addr);
  30         return ret;
  31 }
  32 EXPORT_SYMBOL_GPL(nfs_dns_resolve_name);
  33
  34 #else
  35
  36 #include <linux/module.h>
  37 #include <linux/hash.h>
  38 #include <linux/string.h>
  39 #include <linux/kmod.h>
  40 #include <linux/slab.h>
  41 #include <linux/module.h>
  42 #include <linux/socket.h>
  43 #include <linux/seq_file.h>
  44 #include <linux/inet.h>
  45 #include <linux/sunrpc/clnt.h>
  46 #include <linux/sunrpc/addr.h>
  47 #include <linux/sunrpc/cache.h>
  48 #include <linux/sunrpc/svcauth.h>
  49 #include <linux/sunrpc/rpc_pipe_fs.h>
  50
  51 #include "dns_resolve.h"
  52 #include "cache_lib.h"
  53 #include "netns.h"
  54
  55 #define NFS_DNS_HASHBITS 4
  56 #define NFS_DNS_HASHTBL_SIZE (1 << NFS_DNS_HASHBITS)
  57
  58 struct nfs_dns_ent {
  59         struct cache_head h;
  60
  61         char *hostname;
  62         size_t namelen;
  63
  64         struct sockaddr_storage addr;
  65         size_t addrlen;
  66 };
  67
  68
  69 static void nfs_dns_ent_update(struct cache_head *cnew,
  70                 struct cache_head *ckey)
  71 {
  72         struct nfs_dns_ent *new;
  73         struct nfs_dns_ent *key;
  74
  75         new = container_of(cnew, struct nfs_dns_ent, h);
  76         key = container_of(ckey, struct nfs_dns_ent, h);
  77
  78         memcpy(&new->addr, &key->addr, key->addrlen);
  79         new->addrlen = key->addrlen;
  80 }
  81
  82 static void nfs_dns_ent_init(struct cache_head *cnew,
  83                 struct cache_head *ckey)
  84 {
  85         struct nfs_dns_ent *new;
  86         struct nfs_dns_ent *key;
  87
  88         new = container_of(cnew, struct nfs_dns_ent, h);
  89         key = container_of(ckey, struct nfs_dns_ent, h);
  90
  91         kfree(new->hostname);
  92         new->hostname = kstrndup(key->hostname, key->namelen, GFP_KERNEL);
  93         if (new->hostname) {
  94                 new->namelen = key->namelen;
  95                 nfs_dns_ent_update(cnew, ckey);
  96         } else {
  97                 new->namelen = 0;
  98                 new->addrlen = 0;
  99         }
 100 }
 101
 102 static void nfs_dns_ent_put(struct kref *ref)
 103 {
 104         struct nfs_dns_ent *item;
 105
 106         item = container_of(ref, struct nfs_dns_ent, h.ref);
 107         kfree(item->hostname);
 108         kfree(item);
 109 }
 110
 111 static struct cache_head *nfs_dns_ent_alloc(void)
 112 {
 113         struct nfs_dns_ent *item = kmalloc(sizeof(*item), GFP_KERNEL);
 114
 115         if (item != NULL) {
 116                 item->hostname = NULL;
 117                 item->namelen = 0;
 118                 item->addrlen = 0;
 119                 return &item->h;
 120         }
 121         return NULL;
 122 };
 123
 124 static unsigned int nfs_dns_hash(const struct nfs_dns_ent *key)
 125 {
 126         return hash_str(key->hostname, NFS_DNS_HASHBITS);
 127 }
 128
 129 static void nfs_dns_request(struct cache_detail *cd,
 130                 struct cache_head *ch,
 131                 char **bpp, int *blen)
 132 {
 133         struct nfs_dns_ent *key = container_of(ch, struct nfs_dns_ent, h);
 134
 135         qword_add(bpp, blen, key->hostname);
 136         (*bpp)[-1] = '\n';
 137 }
 138
 139 static int nfs_dns_upcall(struct cache_detail *cd,
 140                 struct cache_head *ch)
 141 {
 142         struct nfs_dns_ent *key = container_of(ch, struct nfs_dns_ent, h);
 143         int ret;
 144
 145         ret = nfs_cache_upcall(cd, key->hostname);
 146         if (ret)
 147                 ret = sunrpc_cache_pipe_upcall(cd, ch, nfs_dns_request);
 148         return ret;
 149 }
 150
 151 static int nfs_dns_match(struct cache_head *ca,
 152                 struct cache_head *cb)
 153 {
 154         struct nfs_dns_ent *a;
 155         struct nfs_dns_ent *b;
 156
 157         a = container_of(ca, struct nfs_dns_ent, h);
 158         b = container_of(cb, struct nfs_dns_ent, h);
 159
 160         if (a->namelen == 0 || a->namelen != b->namelen)
 161                 return 0;
 162         return memcmp(a->hostname, b->hostname, a->namelen) == 0;
 163 }
 164
 165 static int nfs_dns_show(struct seq_file *m, struct cache_detail *cd,
 166                 struct cache_head *h)
 167 {
 168         struct nfs_dns_ent *item;
 169         long ttl;
 170
 171         if (h == NULL) {
 172                 seq_puts(m, "# ip address      hostname        ttl\n");
 173                 return 0;
 174         }
 175         item = container_of(h, struct nfs_dns_ent, h);
 176         ttl = item->h.expiry_time - seconds_since_boot();
 177         if (ttl < 0)
 178                 ttl = 0;
 179
 180         if (!test_bit(CACHE_NEGATIVE, &h->flags)) {
 181                 char buf[INET6_ADDRSTRLEN+IPV6_SCOPE_ID_LEN+1];
 182
 183                 rpc_ntop((struct sockaddr *)&item->addr, buf, sizeof(buf));
 184                 seq_printf(m, "%15s ", buf);
 185         } else
 186                 seq_puts(m, "<none>          ");
 187         seq_printf(m, "%15s %ld\n", item->hostname, ttl);
 188         return 0;
 189 }
 190
 191 static struct nfs_dns_ent *nfs_dns_lookup(struct cache_detail *cd,
 192                 struct nfs_dns_ent *key)
 193 {
 194         struct cache_head *ch;
 195
 196         ch = sunrpc_cache_lookup(cd,
 197                         &key->h,
 198                         nfs_dns_hash(key));
 199         if (!ch)
 200                 return NULL;
 201         return container_of(ch, struct nfs_dns_ent, h);
 202 }
 203
 204 static struct nfs_dns_ent *nfs_dns_update(struct cache_detail *cd,
 205                 struct nfs_dns_ent *new,
 206                 struct nfs_dns_ent *key)
 207 {
 208         struct cache_head *ch;
 209
 210         ch = sunrpc_cache_update(cd,
 211                         &new->h, &key->h,
 212                         nfs_dns_hash(key));
 213         if (!ch)
 214                 return NULL;
 215         return container_of(ch, struct nfs_dns_ent, h);
 216 }
 217
 218 static int nfs_dns_parse(struct cache_detail *cd, char *buf, int buflen)
 219 {
 220         char buf1[NFS_DNS_HOSTNAME_MAXLEN+1];
 221         struct nfs_dns_ent key, *item;
 222         unsigned int ttl;
 223         ssize_t len;
 224         int ret = -EINVAL;
 225
 226         if (buf[buflen-1] != '\n')
 227                 goto out;
 228         buf[buflen-1] = '\0';
 229
 230         len = qword_get(&buf, buf1, sizeof(buf1));
 231         if (len <= 0)
 232                 goto out;
 233         key.addrlen = rpc_pton(cd->net, buf1, len,
 234                         (struct sockaddr *)&key.addr,
 235                         sizeof(key.addr));
 236
 237         len = qword_get(&buf, buf1, sizeof(buf1));
 238         if (len <= 0)
 239                 goto out;
 240
 241         key.hostname = buf1;
 242         key.namelen = len;
 243         memset(&key.h, 0, sizeof(key.h));
 244
 245         if (get_uint(&buf, &ttl) < 0)
 246                 goto out;
 247         if (ttl == 0)
 248                 goto out;
 249         key.h.expiry_time = ttl + seconds_since_boot();
 250
 251         ret = -ENOMEM;
 252         item = nfs_dns_lookup(cd, &key);
 253         if (item == NULL)
 254                 goto out;
 255
 256         if (key.addrlen == 0)
 257                 set_bit(CACHE_NEGATIVE, &key.h.flags);
 258
 259         item = nfs_dns_update(cd, &key, item);
 260         if (item == NULL)
 261                 goto out;
 262
 263         ret = 0;
 264         cache_put(&item->h, cd);
 265 out:
 266         return ret;
 267 }
 268
 269 static int do_cache_lookup(struct cache_detail *cd,
 270                 struct nfs_dns_ent *key,
 271                 struct nfs_dns_ent **item,
 272                 struct nfs_cache_defer_req *dreq)
 273 {
 274         int ret = -ENOMEM;
 275
 276         *item = nfs_dns_lookup(cd, key);
 277         if (*item) {
 278                 ret = cache_check(cd, &(*item)->h, &dreq->req);
 279                 if (ret)
 280                         *item = NULL;
 281         }
 282         return ret;
 283 }
 284
 285 static int do_cache_lookup_nowait(struct cache_detail *cd,
 286                 struct nfs_dns_ent *key,
 287                 struct nfs_dns_ent **item)
 288 {
 289         int ret = -ENOMEM;
 290
 291         *item = nfs_dns_lookup(cd, key);
 292         if (!*item)
 293                 goto out_err;
 294         ret = -ETIMEDOUT;
 295         if (!test_bit(CACHE_VALID, &(*item)->h.flags)
 296                         || (*item)->h.expiry_time < seconds_since_boot()
 297                         || cd->flush_time > (*item)->h.last_refresh)
 298                 goto out_put;
 299         ret = -ENOENT;
 300         if (test_bit(CACHE_NEGATIVE, &(*item)->h.flags))
 301                 goto out_put;
 302         return 0;
 303 out_put:
 304         cache_put(&(*item)->h, cd);
 305 out_err:
 306         *item = NULL;
 307         return ret;
 308 }
 309
 310 static int do_cache_lookup_wait(struct cache_detail *cd,
 311                 struct nfs_dns_ent *key,
 312                 struct nfs_dns_ent **item)
 313 {
 314         struct nfs_cache_defer_req *dreq;
 315         int ret = -ENOMEM;
 316
 317         dreq = nfs_cache_defer_req_alloc();
 318         if (!dreq)
 319                 goto out;
 320         ret = do_cache_lookup(cd, key, item, dreq);
 321         if (ret == -EAGAIN) {
 322                 ret = nfs_cache_wait_for_upcall(dreq);
 323                 if (!ret)
 324                         ret = do_cache_lookup_nowait(cd, key, item);
 325         }
 326         nfs_cache_defer_req_put(dreq);
 327 out:
 328         return ret;
 329 }
 330
 331 ssize_t nfs_dns_resolve_name(struct net *net, char *name,
 332                 size_t namelen, struct sockaddr *sa, size_t salen)
 333 {
 334         struct nfs_dns_ent key = {
 335                 .hostname = name,
 336                 .namelen = namelen,
 337         };
 338         struct nfs_dns_ent *item = NULL;
 339         ssize_t ret;
 340         struct nfs_net *nn = net_generic(net, nfs_net_id);
 341
 342         ret = do_cache_lookup_wait(nn->nfs_dns_resolve, &key, &item);
 343         if (ret == 0) {
 344                 if (salen >= item->addrlen) {
 345                         memcpy(sa, &item->addr, item->addrlen);
 346                         ret = item->addrlen;
 347                 } else
 348                         ret = -EOVERFLOW;
 349                 cache_put(&item->h, nn->nfs_dns_resolve);
 350         } else if (ret == -ENOENT)
 351                 ret = -ESRCH;
 352         return ret;
 353 }
 354 EXPORT_SYMBOL_GPL(nfs_dns_resolve_name);
 355
 356 int nfs_dns_resolver_cache_init(struct net *net)
 357 {
 358         int err = -ENOMEM;
 359         struct nfs_net *nn = net_generic(net, nfs_net_id);
 360         struct cache_detail *cd;
 361         struct cache_head **tbl;
 362
 363         cd = kzalloc(sizeof(struct cache_detail), GFP_KERNEL);
 364         if (cd == NULL)
 365                 goto err_cd;
 366
 367         tbl = kzalloc(NFS_DNS_HASHTBL_SIZE * sizeof(struct cache_head *),
 368                         GFP_KERNEL);
 369         if (tbl == NULL)
 370                 goto err_tbl;
 371
 372         cd->owner = THIS_MODULE,
 373         cd->hash_size = NFS_DNS_HASHTBL_SIZE,
 374         cd->hash_table = tbl,
 375         cd->name = "dns_resolve",
 376         cd->cache_put = nfs_dns_ent_put,
 377         cd->cache_upcall = nfs_dns_upcall,
 378         cd->cache_parse = nfs_dns_parse,
 379         cd->cache_show = nfs_dns_show,
 380         cd->match = nfs_dns_match,
 381         cd->init = nfs_dns_ent_init,
 382         cd->update = nfs_dns_ent_update,
 383         cd->alloc = nfs_dns_ent_alloc,
 384
 385         nfs_cache_init(cd);
 386         err = nfs_cache_register_net(net, cd);
 387         if (err)
 388                 goto err_reg;
 389         nn->nfs_dns_resolve = cd;
 390         return 0;
 391
 392 err_reg:
 393         nfs_cache_destroy(cd);
 394         kfree(cd->hash_table);
 395 err_tbl:
 396         kfree(cd);
 397 err_cd:
 398         return err;
 399 }
 400
 401 void nfs_dns_resolver_cache_destroy(struct net *net)
 402 {
 403         struct nfs_net *nn = net_generic(net, nfs_net_id);
 404         struct cache_detail *cd = nn->nfs_dns_resolve;
 405
 406         nfs_cache_unregister_net(net, cd);
 407         nfs_cache_destroy(cd);
 408         kfree(cd->hash_table);
 409         kfree(cd);
 410 }
 411
 412 static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event,
 413                            void *ptr)
 414 {
 415         struct super_block *sb = ptr;
 416         struct net *net = sb->s_fs_info;
 417         struct nfs_net *nn = net_generic(net, nfs_net_id);
 418         struct cache_detail *cd = nn->nfs_dns_resolve;
 419         int ret = 0;
 420
 421         if (cd == NULL)
 422                 return 0;
 423
 424         if (!try_module_get(THIS_MODULE))
 425                 return 0;
 426
 427         switch (event) {
 428         case RPC_PIPEFS_MOUNT:
 429                 ret = nfs_cache_register_sb(sb, cd);
 430                 break;
 431         case RPC_PIPEFS_UMOUNT:
 432                 nfs_cache_unregister_sb(sb, cd);
 433                 break;
 434         default:
 435                 ret = -ENOTSUPP;
 436                 break;
 437         }
 438         module_put(THIS_MODULE);
 439         return ret;
 440 }
 441
 442 static struct notifier_block nfs_dns_resolver_block = {
 443         .notifier_call  = rpc_pipefs_event,
 444 };
 445
 446 int nfs_dns_resolver_init(void)
 447 {
 448         return rpc_pipefs_notifier_register(&nfs_dns_resolver_block);
 449 }
 450
 451 void nfs_dns_resolver_destroy(void)
 452 {
 453         rpc_pipefs_notifier_unregister(&nfs_dns_resolver_block);
 454 }
 455 #endif