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