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#include <linux/module.h>
11#include <linux/sunrpc/clnt.h>
12#include <linux/sunrpc/addr.h>
13
14#include "dns_resolve.h"
15
16#ifdef CONFIG_NFS_USE_KERNEL_DNS
17
18#include <linux/dns_resolver.h>
19
20ssize_t nfs_dns_resolve_name(struct net *net, char *name, size_t namelen,
21 struct sockaddr_storage *ss, size_t salen)
22{
23 struct sockaddr *sa = (struct sockaddr *)ss;
24 ssize_t ret;
25 char *ip_addr = NULL;
26 int ip_len;
27
28 ip_len = dns_query(net, NULL, name, namelen, NULL, result: &ip_addr, NULL,
29 invalidate: false);
30 if (ip_len > 0)
31 ret = rpc_pton(net, ip_addr, ip_len, sa, salen);
32 else
33 ret = -ESRCH;
34 kfree(objp: ip_addr);
35 return ret;
36}
37
38#else
39
40#include <linux/hash.h>
41#include <linux/string.h>
42#include <linux/kmod.h>
43#include <linux/slab.h>
44#include <linux/socket.h>
45#include <linux/seq_file.h>
46#include <linux/inet.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 "cache_lib.h"
54#include "netns.h"
55
56#define NFS_DNS_HASHBITS 4
57#define NFS_DNS_HASHTBL_SIZE (1 << NFS_DNS_HASHBITS)
58
59struct nfs_dns_ent {
60 struct cache_head h;
61
62 char *hostname;
63 size_t namelen;
64
65 struct sockaddr_storage addr;
66 size_t addrlen;
67 struct rcu_head rcu_head;
68};
69
70
71static 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
84static 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 = kmemdup_nul(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
104static void nfs_dns_ent_free_rcu(struct rcu_head *head)
105{
106 struct nfs_dns_ent *item;
107
108 item = container_of(head, struct nfs_dns_ent, rcu_head);
109 kfree(item->hostname);
110 kfree(item);
111}
112
113static void nfs_dns_ent_put(struct kref *ref)
114{
115 struct nfs_dns_ent *item;
116
117 item = container_of(ref, struct nfs_dns_ent, h.ref);
118 call_rcu(&item->rcu_head, nfs_dns_ent_free_rcu);
119}
120
121static struct cache_head *nfs_dns_ent_alloc(void)
122{
123 struct nfs_dns_ent *item = kmalloc(sizeof(*item), GFP_KERNEL);
124
125 if (item != NULL) {
126 item->hostname = NULL;
127 item->namelen = 0;
128 item->addrlen = 0;
129 return &item->h;
130 }
131 return NULL;
132};
133
134static unsigned int nfs_dns_hash(const struct nfs_dns_ent *key)
135{
136 return hash_str(key->hostname, NFS_DNS_HASHBITS);
137}
138
139static void nfs_dns_request(struct cache_detail *cd,
140 struct cache_head *ch,
141 char **bpp, int *blen)
142{
143 struct nfs_dns_ent *key = container_of(ch, struct nfs_dns_ent, h);
144
145 qword_add(bpp, blen, key->hostname);
146 (*bpp)[-1] = '\n';
147}
148
149static int nfs_dns_upcall(struct cache_detail *cd,
150 struct cache_head *ch)
151{
152 struct nfs_dns_ent *key = container_of(ch, struct nfs_dns_ent, h);
153
154 if (test_and_set_bit(CACHE_PENDING, &ch->flags))
155 return 0;
156 if (!nfs_cache_upcall(cd, key->hostname))
157 return 0;
158 clear_bit(CACHE_PENDING, &ch->flags);
159 return sunrpc_cache_pipe_upcall_timeout(cd, ch);
160}
161
162static 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
176static 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
202static 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
215static 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
229static 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);
276out:
277 return ret;
278}
279
280static 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
296static 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;
314out_put:
315 cache_put(&(*item)->h, cd);
316out_err:
317 *item = NULL;
318 return ret;
319}
320
321static 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);
338out:
339 return ret;
340}
341
342ssize_t nfs_dns_resolve_name(struct net *net, char *name,
343 size_t namelen, struct sockaddr_storage *ss, 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(ss, &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
366static 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
382int 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
396err_reg:
397 cache_destroy_net(nn->nfs_dns_resolve, net);
398 return err;
399}
400
401void 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
409static int nfs4_dns_net_init(struct net *net)
410{
411 return nfs_dns_resolver_cache_init(net);
412}
413
414static void nfs4_dns_net_exit(struct net *net)
415{
416 nfs_dns_resolver_cache_destroy(net);
417}
418
419static struct pernet_operations nfs4_dns_resolver_ops = {
420 .init = nfs4_dns_net_init,
421 .exit = nfs4_dns_net_exit,
422};
423
424static 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
454static struct notifier_block nfs_dns_resolver_block = {
455 .notifier_call = rpc_pipefs_event,
456};
457
458int 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;
469out1:
470 unregister_pernet_subsys(&nfs4_dns_resolver_ops);
471out:
472 return err;
473}
474
475void 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