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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(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         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 = kstrndup(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         int ret;
155 
156         ret = nfs_cache_upcall(cd, key->hostname);
157         if (ret)
158                 ret = sunrpc_cache_pipe_upcall(cd, ch);
159         return ret;
160 }
161 
162 static int nfs_dns_match(struct cache_head *ca,
163                 struct cache_head *cb)
164 {
165         struct nfs_dns_ent *a;
166         struct nfs_dns_ent *b;
167 
168         a = container_of(ca, struct nfs_dns_ent, h);
169         b = container_of(cb, struct nfs_dns_ent, h);
170 
171         if (a->namelen == 0 || a->namelen != b->namelen)
172                 return 0;
173         return memcmp(a->hostname, b->hostname, a->namelen) == 0;
174 }
175 
176 static int nfs_dns_show(struct seq_file *m, struct cache_detail *cd,
177                 struct cache_head *h)
178 {
179         struct nfs_dns_ent *item;
180         long ttl;
181 
182         if (h == NULL) {
183                 seq_puts(m, "# ip address      hostname        ttl\n");
184                 return 0;
185         }
186         item = container_of(h, struct nfs_dns_ent, h);
187         ttl = item->h.expiry_time - seconds_since_boot();
188         if (ttl < 0)
189                 ttl = 0;
190 
191         if (!test_bit(CACHE_NEGATIVE, &h->flags)) {
192                 char buf[INET6_ADDRSTRLEN+IPV6_SCOPE_ID_LEN+1];
193 
194                 rpc_ntop((struct sockaddr *)&item->addr, buf, sizeof(buf));
195                 seq_printf(m, "%15s ", buf);
196         } else
197                 seq_puts(m, "<none>          ");
198         seq_printf(m, "%15s %ld\n", item->hostname, ttl);
199         return 0;
200 }
201 
202 static struct nfs_dns_ent *nfs_dns_lookup(struct cache_detail *cd,
203                 struct nfs_dns_ent *key)
204 {
205         struct cache_head *ch;
206 
207         ch = sunrpc_cache_lookup_rcu(cd,
208                         &key->h,
209                         nfs_dns_hash(key));
210         if (!ch)
211                 return NULL;
212         return container_of(ch, struct nfs_dns_ent, h);
213 }
214 
215 static struct nfs_dns_ent *nfs_dns_update(struct cache_detail *cd,
216                 struct nfs_dns_ent *new,
217                 struct nfs_dns_ent *key)
218 {
219         struct cache_head *ch;
220 
221         ch = sunrpc_cache_update(cd,
222                         &new->h, &key->h,
223                         nfs_dns_hash(key));
224         if (!ch)
225                 return NULL;
226         return container_of(ch, struct nfs_dns_ent, h);
227 }
228 
229 static int nfs_dns_parse(struct cache_detail *cd, char *buf, int buflen)
230 {
231         char buf1[NFS_DNS_HOSTNAME_MAXLEN+1];
232         struct nfs_dns_ent key, *item;
233         unsigned int ttl;
234         ssize_t len;
235         int ret = -EINVAL;
236 
237         if (buf[buflen-1] != '\n')
238                 goto out;
239         buf[buflen-1] = '\0';
240 
241         len = qword_get(&buf, buf1, sizeof(buf1));
242         if (len <= 0)
243                 goto out;
244         key.addrlen = rpc_pton(cd->net, buf1, len,
245                         (struct sockaddr *)&key.addr,
246                         sizeof(key.addr));
247 
248         len = qword_get(&buf, buf1, sizeof(buf1));
249         if (len <= 0)
250                 goto out;
251 
252         key.hostname = buf1;
253         key.namelen = len;
254         memset(&key.h, 0, sizeof(key.h));
255 
256         if (get_uint(&buf, &ttl) < 0)
257                 goto out;
258         if (ttl == 0)
259                 goto out;
260         key.h.expiry_time = ttl + seconds_since_boot();
261 
262         ret = -ENOMEM;
263         item = nfs_dns_lookup(cd, &key);
264         if (item == NULL)
265                 goto out;
266 
267         if (key.addrlen == 0)
268                 set_bit(CACHE_NEGATIVE, &key.h.flags);
269 
270         item = nfs_dns_update(cd, &key, item);
271         if (item == NULL)
272                 goto out;
273 
274         ret = 0;
275         cache_put(&item->h, cd);
276 out:
277         return ret;
278 }
279 
280 static int do_cache_lookup(struct cache_detail *cd,
281                 struct nfs_dns_ent *key,
282                 struct nfs_dns_ent **item,
283                 struct nfs_cache_defer_req *dreq)
284 {
285         int ret = -ENOMEM;
286 
287         *item = nfs_dns_lookup(cd, key);
288         if (*item) {
289                 ret = cache_check(cd, &(*item)->h, &dreq->req);
290                 if (ret)
291                         *item = NULL;
292         }
293         return ret;
294 }
295 
296 static int do_cache_lookup_nowait(struct cache_detail *cd,
297                 struct nfs_dns_ent *key,
298                 struct nfs_dns_ent **item)
299 {
300         int ret = -ENOMEM;
301 
302         *item = nfs_dns_lookup(cd, key);
303         if (!*item)
304                 goto out_err;
305         ret = -ETIMEDOUT;
306         if (!test_bit(CACHE_VALID, &(*item)->h.flags)
307                         || (*item)->h.expiry_time < seconds_since_boot()
308                         || cd->flush_time > (*item)->h.last_refresh)
309                 goto out_put;
310         ret = -ENOENT;
311         if (test_bit(CACHE_NEGATIVE, &(*item)->h.flags))
312                 goto out_put;
313         return 0;
314 out_put:
315         cache_put(&(*item)->h, cd);
316 out_err:
317         *item = NULL;
318         return ret;
319 }
320 
321 static int do_cache_lookup_wait(struct cache_detail *cd,
322                 struct nfs_dns_ent *key,
323                 struct nfs_dns_ent **item)
324 {
325         struct nfs_cache_defer_req *dreq;
326         int ret = -ENOMEM;
327 
328         dreq = nfs_cache_defer_req_alloc();
329         if (!dreq)
330                 goto out;
331         ret = do_cache_lookup(cd, key, item, dreq);
332         if (ret == -EAGAIN) {
333                 ret = nfs_cache_wait_for_upcall(dreq);
334                 if (!ret)
335                         ret = do_cache_lookup_nowait(cd, key, item);
336         }
337         nfs_cache_defer_req_put(dreq);
338 out:
339         return ret;
340 }
341 
342 ssize_t nfs_dns_resolve_name(struct net *net, char *name,
343                 size_t namelen, struct sockaddr *sa, size_t salen)
344 {
345         struct nfs_dns_ent key = {
346                 .hostname = name,
347                 .namelen = namelen,
348         };
349         struct nfs_dns_ent *item = NULL;
350         ssize_t ret;
351         struct nfs_net *nn = net_generic(net, nfs_net_id);
352 
353         ret = do_cache_lookup_wait(nn->nfs_dns_resolve, &key, &item);
354         if (ret == 0) {
355                 if (salen >= item->addrlen) {
356                         memcpy(sa, &item->addr, item->addrlen);
357                         ret = item->addrlen;
358                 } else
359                         ret = -EOVERFLOW;
360                 cache_put(&item->h, nn->nfs_dns_resolve);
361         } else if (ret == -ENOENT)
362                 ret = -ESRCH;
363         return ret;
364 }
365 
366 static struct cache_detail nfs_dns_resolve_template = {
367         .owner          = THIS_MODULE,
368         .hash_size      = NFS_DNS_HASHTBL_SIZE,
369         .name           = "dns_resolve",
370         .cache_put      = nfs_dns_ent_put,
371         .cache_upcall   = nfs_dns_upcall,
372         .cache_request  = nfs_dns_request,
373         .cache_parse    = nfs_dns_parse,
374         .cache_show     = nfs_dns_show,
375         .match          = nfs_dns_match,
376         .init           = nfs_dns_ent_init,
377         .update         = nfs_dns_ent_update,
378         .alloc          = nfs_dns_ent_alloc,
379 };
380 
381 
382 int nfs_dns_resolver_cache_init(struct net *net)
383 {
384         int err;
385         struct nfs_net *nn = net_generic(net, nfs_net_id);
386 
387         nn->nfs_dns_resolve = cache_create_net(&nfs_dns_resolve_template, net);
388         if (IS_ERR(nn->nfs_dns_resolve))
389                 return PTR_ERR(nn->nfs_dns_resolve);
390 
391         err = nfs_cache_register_net(net, nn->nfs_dns_resolve);
392         if (err)
393                 goto err_reg;
394         return 0;
395 
396 err_reg:
397         cache_destroy_net(nn->nfs_dns_resolve, net);
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 
405         nfs_cache_unregister_net(net, nn->nfs_dns_resolve);
406         cache_destroy_net(nn->nfs_dns_resolve, net);
407 }
408 
409 static int nfs4_dns_net_init(struct net *net)
410 {
411         return nfs_dns_resolver_cache_init(net);
412 }
413 
414 static void nfs4_dns_net_exit(struct net *net)
415 {
416         nfs_dns_resolver_cache_destroy(net);
417 }
418 
419 static struct pernet_operations nfs4_dns_resolver_ops = {
420         .init = nfs4_dns_net_init,
421         .exit = nfs4_dns_net_exit,
422 };
423 
424 static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event,
425                            void *ptr)
426 {
427         struct super_block *sb = ptr;
428         struct net *net = sb->s_fs_info;
429         struct nfs_net *nn = net_generic(net, nfs_net_id);
430         struct cache_detail *cd = nn->nfs_dns_resolve;
431         int ret = 0;
432 
433         if (cd == NULL)
434                 return 0;
435 
436         if (!try_module_get(THIS_MODULE))
437                 return 0;
438 
439         switch (event) {
440         case RPC_PIPEFS_MOUNT:
441                 ret = nfs_cache_register_sb(sb, cd);
442                 break;
443         case RPC_PIPEFS_UMOUNT:
444                 nfs_cache_unregister_sb(sb, cd);
445                 break;
446         default:
447                 ret = -ENOTSUPP;
448                 break;
449         }
450         module_put(THIS_MODULE);
451         return ret;
452 }
453 
454 static struct notifier_block nfs_dns_resolver_block = {
455         .notifier_call  = rpc_pipefs_event,
456 };
457 
458 int nfs_dns_resolver_init(void)
459 {
460         int err;
461 
462         err = register_pernet_subsys(&nfs4_dns_resolver_ops);
463         if (err < 0)
464                 goto out;
465         err = rpc_pipefs_notifier_register(&nfs_dns_resolver_block);
466         if (err < 0)
467                 goto out1;
468         return 0;
469 out1:
470         unregister_pernet_subsys(&nfs4_dns_resolver_ops);
471 out:
472         return err;
473 }
474 
475 void nfs_dns_resolver_destroy(void)
476 {
477         rpc_pipefs_notifier_unregister(&nfs_dns_resolver_block);
478         unregister_pernet_subsys(&nfs4_dns_resolver_ops);
479 }
480 #endif
481 

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