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Linux/fs/nfs/dns_resolve.c

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  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(net, NULL, name, namelen, NULL, &ip_addr, NULL,
 26                            false);
 27         if (ip_len > 0)
 28                 ret = rpc_pton(net, ip_addr, ip_len, sa, salen);
 29         else
 30                 ret = -ESRCH;
 31         kfree(ip_addr);
 32         return ret;
 33 }
 34 
 35 #else
 36 
 37 #include <linux/module.h>
 38 #include <linux/hash.h>
 39 #include <linux/string.h>
 40 #include <linux/kmod.h>
 41 #include <linux/slab.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         struct rcu_head rcu_head;
 69 };
 70 
 71 
 72 static void nfs_dns_ent_update(struct cache_head *cnew,
 73                 struct cache_head *ckey)
 74 {
 75         struct nfs_dns_ent *new;
 76         struct nfs_dns_ent *key;
 77 
 78         new = container_of(cnew, struct nfs_dns_ent, h);
 79         key = container_of(ckey, struct nfs_dns_ent, h);
 80 
 81         memcpy(&new->addr, &key->addr, key->addrlen);
 82         new->addrlen = key->addrlen;
 83 }
 84 
 85 static void nfs_dns_ent_init(struct cache_head *cnew,
 86                 struct cache_head *ckey)
 87 {
 88         struct nfs_dns_ent *new;
 89         struct nfs_dns_ent *key;
 90 
 91         new = container_of(cnew, struct nfs_dns_ent, h);
 92         key = container_of(ckey, struct nfs_dns_ent, h);
 93 
 94         kfree(new->hostname);
 95         new->hostname = kmemdup_nul(key->hostname, key->namelen, GFP_KERNEL);
 96         if (new->hostname) {
 97                 new->namelen = key->namelen;
 98                 nfs_dns_ent_update(cnew, ckey);
 99         } else {
100                 new->namelen = 0;
101                 new->addrlen = 0;
102         }
103 }
104 
105 static void nfs_dns_ent_free_rcu(struct rcu_head *head)
106 {
107         struct nfs_dns_ent *item;
108 
109         item = container_of(head, struct nfs_dns_ent, rcu_head);
110         kfree(item->hostname);
111         kfree(item);
112 }
113 
114 static void nfs_dns_ent_put(struct kref *ref)
115 {
116         struct nfs_dns_ent *item;
117 
118         item = container_of(ref, struct nfs_dns_ent, h.ref);
119         call_rcu(&item->rcu_head, nfs_dns_ent_free_rcu);
120 }
121 
122 static struct cache_head *nfs_dns_ent_alloc(void)
123 {
124         struct nfs_dns_ent *item = kmalloc(sizeof(*item), GFP_KERNEL);
125 
126         if (item != NULL) {
127                 item->hostname = NULL;
128                 item->namelen = 0;
129                 item->addrlen = 0;
130                 return &item->h;
131         }
132         return NULL;
133 };
134 
135 static unsigned int nfs_dns_hash(const struct nfs_dns_ent *key)
136 {
137         return hash_str(key->hostname, NFS_DNS_HASHBITS);
138 }
139 
140 static void nfs_dns_request(struct cache_detail *cd,
141                 struct cache_head *ch,
142                 char **bpp, int *blen)
143 {
144         struct nfs_dns_ent *key = container_of(ch, struct nfs_dns_ent, h);
145 
146         qword_add(bpp, blen, key->hostname);
147         (*bpp)[-1] = '\n';
148 }
149 
150 static int nfs_dns_upcall(struct cache_detail *cd,
151                 struct cache_head *ch)
152 {
153         struct nfs_dns_ent *key = container_of(ch, struct nfs_dns_ent, h);
154 
155         if (test_and_set_bit(CACHE_PENDING, &ch->flags))
156                 return 0;
157         if (!nfs_cache_upcall(cd, key->hostname))
158                 return 0;
159         clear_bit(CACHE_PENDING, &ch->flags);
160         return sunrpc_cache_pipe_upcall_timeout(cd, ch);
161 }
162 
163 static int nfs_dns_match(struct cache_head *ca,
164                 struct cache_head *cb)
165 {
166         struct nfs_dns_ent *a;
167         struct nfs_dns_ent *b;
168 
169         a = container_of(ca, struct nfs_dns_ent, h);
170         b = container_of(cb, struct nfs_dns_ent, h);
171 
172         if (a->namelen == 0 || a->namelen != b->namelen)
173                 return 0;
174         return memcmp(a->hostname, b->hostname, a->namelen) == 0;
175 }
176 
177 static int nfs_dns_show(struct seq_file *m, struct cache_detail *cd,
178                 struct cache_head *h)
179 {
180         struct nfs_dns_ent *item;
181         long ttl;
182 
183         if (h == NULL) {
184                 seq_puts(m, "# ip address      hostname        ttl\n");
185                 return 0;
186         }
187         item = container_of(h, struct nfs_dns_ent, h);
188         ttl = item->h.expiry_time - seconds_since_boot();
189         if (ttl < 0)
190                 ttl = 0;
191 
192         if (!test_bit(CACHE_NEGATIVE, &h->flags)) {
193                 char buf[INET6_ADDRSTRLEN+IPV6_SCOPE_ID_LEN+1];
194 
195                 rpc_ntop((struct sockaddr *)&item->addr, buf, sizeof(buf));
196                 seq_printf(m, "%15s ", buf);
197         } else
198                 seq_puts(m, "<none>          ");
199         seq_printf(m, "%15s %ld\n", item->hostname, ttl);
200         return 0;
201 }
202 
203 static struct nfs_dns_ent *nfs_dns_lookup(struct cache_detail *cd,
204                 struct nfs_dns_ent *key)
205 {
206         struct cache_head *ch;
207 
208         ch = sunrpc_cache_lookup_rcu(cd,
209                         &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 struct nfs_dns_ent *nfs_dns_update(struct cache_detail *cd,
217                 struct nfs_dns_ent *new,
218                 struct nfs_dns_ent *key)
219 {
220         struct cache_head *ch;
221 
222         ch = sunrpc_cache_update(cd,
223                         &new->h, &key->h,
224                         nfs_dns_hash(key));
225         if (!ch)
226                 return NULL;
227         return container_of(ch, struct nfs_dns_ent, h);
228 }
229 
230 static int nfs_dns_parse(struct cache_detail *cd, char *buf, int buflen)
231 {
232         char buf1[NFS_DNS_HOSTNAME_MAXLEN+1];
233         struct nfs_dns_ent key, *item;
234         unsigned int ttl;
235         ssize_t len;
236         int ret = -EINVAL;
237 
238         if (buf[buflen-1] != '\n')
239                 goto out;
240         buf[buflen-1] = '\0';
241 
242         len = qword_get(&buf, buf1, sizeof(buf1));
243         if (len <= 0)
244                 goto out;
245         key.addrlen = rpc_pton(cd->net, buf1, len,
246                         (struct sockaddr *)&key.addr,
247                         sizeof(key.addr));
248 
249         len = qword_get(&buf, buf1, sizeof(buf1));
250         if (len <= 0)
251                 goto out;
252 
253         key.hostname = buf1;
254         key.namelen = len;
255         memset(&key.h, 0, sizeof(key.h));
256 
257         if (get_uint(&buf, &ttl) < 0)
258                 goto out;
259         if (ttl == 0)
260                 goto out;
261         key.h.expiry_time = ttl + seconds_since_boot();
262 
263         ret = -ENOMEM;
264         item = nfs_dns_lookup(cd, &key);
265         if (item == NULL)
266                 goto out;
267 
268         if (key.addrlen == 0)
269                 set_bit(CACHE_NEGATIVE, &key.h.flags);
270 
271         item = nfs_dns_update(cd, &key, item);
272         if (item == NULL)
273                 goto out;
274 
275         ret = 0;
276         cache_put(&item->h, cd);
277 out:
278         return ret;
279 }
280 
281 static int do_cache_lookup(struct cache_detail *cd,
282                 struct nfs_dns_ent *key,
283                 struct nfs_dns_ent **item,
284                 struct nfs_cache_defer_req *dreq)
285 {
286         int ret = -ENOMEM;
287 
288         *item = nfs_dns_lookup(cd, key);
289         if (*item) {
290                 ret = cache_check(cd, &(*item)->h, &dreq->req);
291                 if (ret)
292                         *item = NULL;
293         }
294         return ret;
295 }
296 
297 static int do_cache_lookup_nowait(struct cache_detail *cd,
298                 struct nfs_dns_ent *key,
299                 struct nfs_dns_ent **item)
300 {
301         int ret = -ENOMEM;
302 
303         *item = nfs_dns_lookup(cd, key);
304         if (!*item)
305                 goto out_err;
306         ret = -ETIMEDOUT;
307         if (!test_bit(CACHE_VALID, &(*item)->h.flags)
308                         || (*item)->h.expiry_time < seconds_since_boot()
309                         || cd->flush_time > (*item)->h.last_refresh)
310                 goto out_put;
311         ret = -ENOENT;
312         if (test_bit(CACHE_NEGATIVE, &(*item)->h.flags))
313                 goto out_put;
314         return 0;
315 out_put:
316         cache_put(&(*item)->h, cd);
317 out_err:
318         *item = NULL;
319         return ret;
320 }
321 
322 static int do_cache_lookup_wait(struct cache_detail *cd,
323                 struct nfs_dns_ent *key,
324                 struct nfs_dns_ent **item)
325 {
326         struct nfs_cache_defer_req *dreq;
327         int ret = -ENOMEM;
328 
329         dreq = nfs_cache_defer_req_alloc();
330         if (!dreq)
331                 goto out;
332         ret = do_cache_lookup(cd, key, item, dreq);
333         if (ret == -EAGAIN) {
334                 ret = nfs_cache_wait_for_upcall(dreq);
335                 if (!ret)
336                         ret = do_cache_lookup_nowait(cd, key, item);
337         }
338         nfs_cache_defer_req_put(dreq);
339 out:
340         return ret;
341 }
342 
343 ssize_t nfs_dns_resolve_name(struct net *net, char *name,
344                 size_t namelen, struct sockaddr *sa, size_t salen)
345 {
346         struct nfs_dns_ent key = {
347                 .hostname = name,
348                 .namelen = namelen,
349         };
350         struct nfs_dns_ent *item = NULL;
351         ssize_t ret;
352         struct nfs_net *nn = net_generic(net, nfs_net_id);
353 
354         ret = do_cache_lookup_wait(nn->nfs_dns_resolve, &key, &item);
355         if (ret == 0) {
356                 if (salen >= item->addrlen) {
357                         memcpy(sa, &item->addr, item->addrlen);
358                         ret = item->addrlen;
359                 } else
360                         ret = -EOVERFLOW;
361                 cache_put(&item->h, nn->nfs_dns_resolve);
362         } else if (ret == -ENOENT)
363                 ret = -ESRCH;
364         return ret;
365 }
366 
367 static struct cache_detail nfs_dns_resolve_template = {
368         .owner          = THIS_MODULE,
369         .hash_size      = NFS_DNS_HASHTBL_SIZE,
370         .name           = "dns_resolve",
371         .cache_put      = nfs_dns_ent_put,
372         .cache_upcall   = nfs_dns_upcall,
373         .cache_request  = nfs_dns_request,
374         .cache_parse    = nfs_dns_parse,
375         .cache_show     = nfs_dns_show,
376         .match          = nfs_dns_match,
377         .init           = nfs_dns_ent_init,
378         .update         = nfs_dns_ent_update,
379         .alloc          = nfs_dns_ent_alloc,
380 };
381 
382 
383 int nfs_dns_resolver_cache_init(struct net *net)
384 {
385         int err;
386         struct nfs_net *nn = net_generic(net, nfs_net_id);
387 
388         nn->nfs_dns_resolve = cache_create_net(&nfs_dns_resolve_template, net);
389         if (IS_ERR(nn->nfs_dns_resolve))
390                 return PTR_ERR(nn->nfs_dns_resolve);
391 
392         err = nfs_cache_register_net(net, nn->nfs_dns_resolve);
393         if (err)
394                 goto err_reg;
395         return 0;
396 
397 err_reg:
398         cache_destroy_net(nn->nfs_dns_resolve, net);
399         return err;
400 }
401 
402 void nfs_dns_resolver_cache_destroy(struct net *net)
403 {
404         struct nfs_net *nn = net_generic(net, nfs_net_id);
405 
406         nfs_cache_unregister_net(net, nn->nfs_dns_resolve);
407         cache_destroy_net(nn->nfs_dns_resolve, net);
408 }
409 
410 static int nfs4_dns_net_init(struct net *net)
411 {
412         return nfs_dns_resolver_cache_init(net);
413 }
414 
415 static void nfs4_dns_net_exit(struct net *net)
416 {
417         nfs_dns_resolver_cache_destroy(net);
418 }
419 
420 static struct pernet_operations nfs4_dns_resolver_ops = {
421         .init = nfs4_dns_net_init,
422         .exit = nfs4_dns_net_exit,
423 };
424 
425 static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event,
426                            void *ptr)
427 {
428         struct super_block *sb = ptr;
429         struct net *net = sb->s_fs_info;
430         struct nfs_net *nn = net_generic(net, nfs_net_id);
431         struct cache_detail *cd = nn->nfs_dns_resolve;
432         int ret = 0;
433 
434         if (cd == NULL)
435                 return 0;
436 
437         if (!try_module_get(THIS_MODULE))
438                 return 0;
439 
440         switch (event) {
441         case RPC_PIPEFS_MOUNT:
442                 ret = nfs_cache_register_sb(sb, cd);
443                 break;
444         case RPC_PIPEFS_UMOUNT:
445                 nfs_cache_unregister_sb(sb, cd);
446                 break;
447         default:
448                 ret = -ENOTSUPP;
449                 break;
450         }
451         module_put(THIS_MODULE);
452         return ret;
453 }
454 
455 static struct notifier_block nfs_dns_resolver_block = {
456         .notifier_call  = rpc_pipefs_event,
457 };
458 
459 int nfs_dns_resolver_init(void)
460 {
461         int err;
462 
463         err = register_pernet_subsys(&nfs4_dns_resolver_ops);
464         if (err < 0)
465                 goto out;
466         err = rpc_pipefs_notifier_register(&nfs_dns_resolver_block);
467         if (err < 0)
468                 goto out1;
469         return 0;
470 out1:
471         unregister_pernet_subsys(&nfs4_dns_resolver_ops);
472 out:
473         return err;
474 }
475 
476 void nfs_dns_resolver_destroy(void)
477 {
478         rpc_pipefs_notifier_unregister(&nfs_dns_resolver_block);
479         unregister_pernet_subsys(&nfs4_dns_resolver_ops);
480 }
481 #endif
482 

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