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
nfs_dns_resolve_name(struct net * net,char * name,size_t namelen,struct sockaddr * sa,size_t salen)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
nfs_dns_ent_update(struct cache_head * cnew,struct cache_head * ckey)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
nfs_dns_ent_init(struct cache_head * cnew,struct cache_head * ckey)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
nfs_dns_ent_free_rcu(struct rcu_head * head)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
nfs_dns_ent_put(struct kref * ref)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
nfs_dns_ent_alloc(void)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
nfs_dns_hash(const struct nfs_dns_ent * key)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
nfs_dns_request(struct cache_detail * cd,struct cache_head * ch,char ** bpp,int * blen)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
nfs_dns_upcall(struct cache_detail * cd,struct cache_head * ch)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
nfs_dns_match(struct cache_head * ca,struct cache_head * cb)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
nfs_dns_show(struct seq_file * m,struct cache_detail * cd,struct cache_head * h)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
nfs_dns_lookup(struct cache_detail * cd,struct nfs_dns_ent * key)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
nfs_dns_update(struct cache_detail * cd,struct nfs_dns_ent * new,struct nfs_dns_ent * key)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
nfs_dns_parse(struct cache_detail * cd,char * buf,int buflen)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
do_cache_lookup(struct cache_detail * cd,struct nfs_dns_ent * key,struct nfs_dns_ent ** item,struct nfs_cache_defer_req * dreq)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
do_cache_lookup_nowait(struct cache_detail * cd,struct nfs_dns_ent * key,struct nfs_dns_ent ** item)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
do_cache_lookup_wait(struct cache_detail * cd,struct nfs_dns_ent * key,struct nfs_dns_ent ** item)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
nfs_dns_resolve_name(struct net * net,char * name,size_t namelen,struct sockaddr * sa,size_t salen)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
nfs_dns_resolver_cache_init(struct net * net)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
nfs_dns_resolver_cache_destroy(struct net * net)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
nfs4_dns_net_init(struct net * net)410 static int nfs4_dns_net_init(struct net *net)
411 {
412 return nfs_dns_resolver_cache_init(net);
413 }
414
nfs4_dns_net_exit(struct net * net)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
rpc_pipefs_event(struct notifier_block * nb,unsigned long event,void * ptr)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
nfs_dns_resolver_init(void)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
nfs_dns_resolver_destroy(void)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