fs/nfs/dns_resolve.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * linux/fs/nfs/dns_resolve.c
   4  *
   5  * Copyright (c) 2009 Trond Myklebust <Trond.Myklebust@netapp.com>
   6  *
   7  * Resolves DNS hostnames into valid ip addresses
   8  */
   9
  10 #ifdef CONFIG_NFS_USE_KERNEL_DNS
  11
  12 #include <linux/module.h>
  13 #include <linux/sunrpc/clnt.h>
  14 #include <linux/sunrpc/addr.h>
  15 #include <linux/dns_resolver.h>
  16 #include "dns_resolve.h"
  17
  18 ssize_t nfs_dns_resolve_name(struct net *net, char *name, size_t namelen,
  19                 struct sockaddr *sa, size_t salen)
  20 {
  21         ssize_t ret;
  22         char *ip_addr = NULL;
  23         int ip_len;
  24
  25         ip_len = dns_query(NULL, name, namelen, NULL, &ip_addr, NULL);
  26         if (ip_len > 0)
  27                 ret = rpc_pton(net, ip_addr, ip_len, sa, salen);
  28         else
  29                 ret = -ESRCH;
  30         kfree(ip_addr);
  31         return ret;
  32 }
  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 #include <linux/nfs_fs.h>
  51
  52 #include "nfs4_fs.h"
  53 #include "dns_resolve.h"
  54 #include "cache_lib.h"
  55 #include "netns.h"
  56
  57 #define NFS_DNS_HASHBITS 4
  58 #define NFS_DNS_HASHTBL_SIZE (1 << NFS_DNS_HASHBITS)
  59
  60 struct nfs_dns_ent {
  61         struct cache_head h;
  62
  63         char *hostname;
  64         size_t namelen;
  65
  66         struct sockaddr_storage addr;
  67         size_t addrlen;
  68 };
  69
  70
  71 static void nfs_dns_ent_update(struct cache_head *cnew,
  72                 struct cache_head *ckey)
  73 {
  74         struct nfs_dns_ent *new;
  75         struct nfs_dns_ent *key;
  76
  77         new = container_of(cnew, struct nfs_dns_ent, h);
  78         key = container_of(ckey, struct nfs_dns_ent, h);
  79
  80         memcpy(&new->addr, &key->addr, key->addrlen);
  81         new->addrlen = key->addrlen;
  82 }
  83
  84 static void nfs_dns_ent_init(struct cache_head *cnew,
  85                 struct cache_head *ckey)
  86 {
  87         struct nfs_dns_ent *new;
  88         struct nfs_dns_ent *key;
  89
  90         new = container_of(cnew, struct nfs_dns_ent, h);
  91         key = container_of(ckey, struct nfs_dns_ent, h);
  92
  93         kfree(new->hostname);
  94         new->hostname = kstrndup(key->hostname, key->namelen, GFP_KERNEL);
  95         if (new->hostname) {
  96                 new->namelen = key->namelen;
  97                 nfs_dns_ent_update(cnew, ckey);
  98         } else {
  99                 new->namelen = 0;
 100                 new->addrlen = 0;
 101         }
 102 }
 103
 104 static void nfs_dns_ent_put(struct kref *ref)
 105 {
 106         struct nfs_dns_ent *item;
 107
 108         item = container_of(ref, struct nfs_dns_ent, h.ref);
 109         kfree(item->hostname);
 110         kfree(item);
 111 }
 112
 113 static struct cache_head *nfs_dns_ent_alloc(void)
 114 {
 115         struct nfs_dns_ent *item = kmalloc(sizeof(*item), GFP_KERNEL);
 116
 117         if (item != NULL) {
 118                 item->hostname = NULL;
 119                 item->namelen = 0;
 120                 item->addrlen = 0;
 121                 return &item->h;
 122         }
 123         return NULL;
 124 };
 125
 126 static unsigned int nfs_dns_hash(const struct nfs_dns_ent *key)
 127 {
 128         return hash_str(key->hostname, NFS_DNS_HASHBITS);
 129 }
 130
 131 static void nfs_dns_request(struct cache_detail *cd,
 132                 struct cache_head *ch,
 133                 char **bpp, int *blen)
 134 {
 135         struct nfs_dns_ent *key = container_of(ch, struct nfs_dns_ent, h);
 136
 137         qword_add(bpp, blen, key->hostname);
 138         (*bpp)[-1] = '\n';
 139 }
 140
 141 static int nfs_dns_upcall(struct cache_detail *cd,
 142                 struct cache_head *ch)
 143 {
 144         struct nfs_dns_ent *key = container_of(ch, struct nfs_dns_ent, h);
 145         int ret;
 146
 147         ret = nfs_cache_upcall(cd, key->hostname);
 148         if (ret)
 149                 ret = sunrpc_cache_pipe_upcall(cd, ch);
 150         return ret;
 151 }
 152
 153 static int nfs_dns_match(struct cache_head *ca,
 154                 struct cache_head *cb)
 155 {
 156         struct nfs_dns_ent *a;
 157         struct nfs_dns_ent *b;
 158
 159         a = container_of(ca, struct nfs_dns_ent, h);
 160         b = container_of(cb, struct nfs_dns_ent, h);
 161
 162         if (a->namelen == 0 || a->namelen != b->namelen)
 163                 return 0;
 164         return memcmp(a->hostname, b->hostname, a->namelen) == 0;
 165 }
 166
 167 static int nfs_dns_show(struct seq_file *m, struct cache_detail *cd,
 168                 struct cache_head *h)
 169 {
 170         struct nfs_dns_ent *item;
 171         long ttl;
 172
 173         if (h == NULL) {
 174                 seq_puts(m, "# ip address      hostname        ttl\n");
 175                 return 0;
 176         }
 177         item = container_of(h, struct nfs_dns_ent, h);
 178         ttl = item->h.expiry_time - seconds_since_boot();
 179         if (ttl < 0)
 180                 ttl = 0;
 181
 182         if (!test_bit(CACHE_NEGATIVE, &h->flags)) {
 183                 char buf[INET6_ADDRSTRLEN+IPV6_SCOPE_ID_LEN+1];
 184
 185                 rpc_ntop((struct sockaddr *)&item->addr, buf, sizeof(buf));
 186                 seq_printf(m, "%15s ", buf);
 187         } else
 188                 seq_puts(m, "<none>          ");
 189         seq_printf(m, "%15s %ld\n", item->hostname, ttl);
 190         return 0;
 191 }
 192
 193 static struct nfs_dns_ent *nfs_dns_lookup(struct cache_detail *cd,
 194                 struct nfs_dns_ent *key)
 195 {
 196         struct cache_head *ch;
 197
 198         ch = sunrpc_cache_lookup(cd,
 199                         &key->h,
 200                         nfs_dns_hash(key));
 201         if (!ch)
 202                 return NULL;
 203         return container_of(ch, struct nfs_dns_ent, h);
 204 }
 205
 206 static struct nfs_dns_ent *nfs_dns_update(struct cache_detail *cd,
 207                 struct nfs_dns_ent *new,
 208                 struct nfs_dns_ent *key)
 209 {
 210         struct cache_head *ch;
 211
 212         ch = sunrpc_cache_update(cd,
 213                         &new->h, &key->h,
 214                         nfs_dns_hash(key));
 215         if (!ch)
 216                 return NULL;
 217         return container_of(ch, struct nfs_dns_ent, h);
 218 }
 219
 220 static int nfs_dns_parse(struct cache_detail *cd, char *buf, int buflen)
 221 {
 222         char buf1[NFS_DNS_HOSTNAME_MAXLEN+1];
 223         struct nfs_dns_ent key, *item;
 224         unsigned int ttl;
 225         ssize_t len;
 226         int ret = -EINVAL;
 227
 228         if (buf[buflen-1] != '\n')
 229                 goto out;
 230         buf[buflen-1] = '\0';
 231
 232         len = qword_get(&buf, buf1, sizeof(buf1));
 233         if (len <= 0)
 234                 goto out;
 235         key.addrlen = rpc_pton(cd->net, buf1, len,
 236                         (struct sockaddr *)&key.addr,
 237                         sizeof(key.addr));
 238
 239         len = qword_get(&buf, buf1, sizeof(buf1));
 240         if (len <= 0)
 241                 goto out;
 242
 243         key.hostname = buf1;
 244         key.namelen = len;
 245         memset(&key.h, 0, sizeof(key.h));
 246
 247         if (get_uint(&buf, &ttl) < 0)
 248                 goto out;
 249         if (ttl == 0)
 250                 goto out;
 251         key.h.expiry_time = ttl + seconds_since_boot();
 252
 253         ret = -ENOMEM;
 254         item = nfs_dns_lookup(cd, &key);
 255         if (item == NULL)
 256                 goto out;
 257
 258         if (key.addrlen == 0)
 259                 set_bit(CACHE_NEGATIVE, &key.h.flags);
 260
 261         item = nfs_dns_update(cd, &key, item);
 262         if (item == NULL)
 263                 goto out;
 264
 265         ret = 0;
 266         cache_put(&item->h, cd);
 267 out:
 268         return ret;
 269 }
 270
 271 static int do_cache_lookup(struct cache_detail *cd,
 272                 struct nfs_dns_ent *key,
 273                 struct nfs_dns_ent **item,
 274                 struct nfs_cache_defer_req *dreq)
 275 {
 276         int ret = -ENOMEM;
 277
 278         *item = nfs_dns_lookup(cd, key);
 279         if (*item) {
 280                 ret = cache_check(cd, &(*item)->h, &dreq->req);
 281                 if (ret)
 282                         *item = NULL;
 283         }
 284         return ret;
 285 }
 286
 287 static int do_cache_lookup_nowait(struct cache_detail *cd,
 288                 struct nfs_dns_ent *key,
 289                 struct nfs_dns_ent **item)
 290 {
 291         int ret = -ENOMEM;
 292
 293         *item = nfs_dns_lookup(cd, key);
 294         if (!*item)
 295                 goto out_err;
 296         ret = -ETIMEDOUT;
 297         if (!test_bit(CACHE_VALID, &(*item)->h.flags)
 298                         || (*item)->h.expiry_time < seconds_since_boot()
 299                         || cd->flush_time > (*item)->h.last_refresh)
 300                 goto out_put;
 301         ret = -ENOENT;
 302         if (test_bit(CACHE_NEGATIVE, &(*item)->h.flags))
 303                 goto out_put;
 304         return 0;
 305 out_put:
 306         cache_put(&(*item)->h, cd);
 307 out_err:
 308         *item = NULL;
 309         return ret;
 310 }
 311
 312 static int do_cache_lookup_wait(struct cache_detail *cd,
 313                 struct nfs_dns_ent *key,
 314                 struct nfs_dns_ent **item)
 315 {
 316         struct nfs_cache_defer_req *dreq;
 317         int ret = -ENOMEM;
 318
 319         dreq = nfs_cache_defer_req_alloc();
 320         if (!dreq)
 321                 goto out;
 322         ret = do_cache_lookup(cd, key, item, dreq);
 323         if (ret == -EAGAIN) {
 324                 ret = nfs_cache_wait_for_upcall(dreq);
 325                 if (!ret)
 326                         ret = do_cache_lookup_nowait(cd, key, item);
 327         }
 328         nfs_cache_defer_req_put(dreq);
 329 out:
 330         return ret;
 331 }
 332
 333 ssize_t nfs_dns_resolve_name(struct net *net, char *name,
 334                 size_t namelen, struct sockaddr *sa, size_t salen)
 335 {
 336         struct nfs_dns_ent key = {
 337                 .hostname = name,
 338                 .namelen = namelen,
 339         };
 340         struct nfs_dns_ent *item = NULL;
 341         ssize_t ret;
 342         struct nfs_net *nn = net_generic(net, nfs_net_id);
 343
 344         ret = do_cache_lookup_wait(nn->nfs_dns_resolve, &key, &item);
 345         if (ret == 0) {
 346                 if (salen >= item->addrlen) {
 347                         memcpy(sa, &item->addr, item->addrlen);
 348                         ret = item->addrlen;
 349                 } else
 350                         ret = -EOVERFLOW;
 351                 cache_put(&item->h, nn->nfs_dns_resolve);
 352         } else if (ret == -ENOENT)
 353                 ret = -ESRCH;
 354         return ret;
 355 }
 356
 357 static struct cache_detail nfs_dns_resolve_template = {
 358         .owner          = THIS_MODULE,
 359         .hash_size      = NFS_DNS_HASHTBL_SIZE,
 360         .name           = "dns_resolve",
 361         .cache_put      = nfs_dns_ent_put,
 362         .cache_upcall   = nfs_dns_upcall,
 363         .cache_request  = nfs_dns_request,
 364         .cache_parse    = nfs_dns_parse,
 365         .cache_show     = nfs_dns_show,
 366         .match          = nfs_dns_match,
 367         .init           = nfs_dns_ent_init,
 368         .update         = nfs_dns_ent_update,
 369         .alloc          = nfs_dns_ent_alloc,
 370 };
 371
 372
 373 int nfs_dns_resolver_cache_init(struct net *net)
 374 {
 375         int err;
 376         struct nfs_net *nn = net_generic(net, nfs_net_id);
 377
 378         nn->nfs_dns_resolve = cache_create_net(&nfs_dns_resolve_template, net);
 379         if (IS_ERR(nn->nfs_dns_resolve))
 380                 return PTR_ERR(nn->nfs_dns_resolve);
 381
 382         err = nfs_cache_register_net(net, nn->nfs_dns_resolve);
 383         if (err)
 384                 goto err_reg;
 385         return 0;
 386
 387 err_reg:
 388         cache_destroy_net(nn->nfs_dns_resolve, net);
 389         return err;
 390 }
 391
 392 void nfs_dns_resolver_cache_destroy(struct net *net)
 393 {
 394         struct nfs_net *nn = net_generic(net, nfs_net_id);
 395
 396         nfs_cache_unregister_net(net, nn->nfs_dns_resolve);
 397         cache_destroy_net(nn->nfs_dns_resolve, net);
 398 }
 399
 400 static int nfs4_dns_net_init(struct net *net)
 401 {
 402         return nfs_dns_resolver_cache_init(net);
 403 }
 404
 405 static void nfs4_dns_net_exit(struct net *net)
 406 {
 407         nfs_dns_resolver_cache_destroy(net);
 408 }
 409
 410 static struct pernet_operations nfs4_dns_resolver_ops = {
 411         .init = nfs4_dns_net_init,
 412         .exit = nfs4_dns_net_exit,
 413 };
 414
 415 static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event,
 416                            void *ptr)
 417 {
 418         struct super_block *sb = ptr;
 419         struct net *net = sb->s_fs_info;
 420         struct nfs_net *nn = net_generic(net, nfs_net_id);
 421         struct cache_detail *cd = nn->nfs_dns_resolve;
 422         int ret = 0;
 423
 424         if (cd == NULL)
 425                 return 0;
 426
 427         if (!try_module_get(THIS_MODULE))
 428                 return 0;
 429
 430         switch (event) {
 431         case RPC_PIPEFS_MOUNT:
 432                 ret = nfs_cache_register_sb(sb, cd);
 433                 break;
 434         case RPC_PIPEFS_UMOUNT:
 435                 nfs_cache_unregister_sb(sb, cd);
 436                 break;
 437         default:
 438                 ret = -ENOTSUPP;
 439                 break;
 440         }
 441         module_put(THIS_MODULE);
 442         return ret;
 443 }
 444
 445 static struct notifier_block nfs_dns_resolver_block = {
 446         .notifier_call  = rpc_pipefs_event,
 447 };
 448
 449 int nfs_dns_resolver_init(void)
 450 {
 451         int err;
 452
 453         err = register_pernet_subsys(&nfs4_dns_resolver_ops);
 454         if (err < 0)
 455                 goto out;
 456         err = rpc_pipefs_notifier_register(&nfs_dns_resolver_block);
 457         if (err < 0)
 458                 goto out1;
 459         return 0;
 460 out1:
 461         unregister_pernet_subsys(&nfs4_dns_resolver_ops);
 462 out:
 463         return err;
 464 }
 465
 466 void nfs_dns_resolver_destroy(void)
 467 {
 468         rpc_pipefs_notifier_unregister(&nfs_dns_resolver_block);
 469         unregister_pernet_subsys(&nfs4_dns_resolver_ops);
 470 }
 471 #endif