xref: /linux/fs/nfs/dns_resolve.c (revision a1c613ae4c322ddd58d5a8539dbfba2a0380a8c0)
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 
nfs_dns_resolve_name(struct net * net,char * name,size_t namelen,struct sockaddr_storage * ss,size_t salen)20 ssize_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, &ip_addr, NULL,
29 			   false);
30 	if (ip_len > 0)
31 		ret = rpc_pton(net, ip_addr, ip_len, sa, salen);
32 	else
33 		ret = -ESRCH;
34 	kfree(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 
59 struct 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 
nfs_dns_ent_update(struct cache_head * cnew,struct cache_head * ckey)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 
nfs_dns_ent_init(struct cache_head * cnew,struct cache_head * ckey)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 = 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 
nfs_dns_ent_free_rcu(struct rcu_head * head)104 static 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 
nfs_dns_ent_put(struct kref * ref)113 static 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 
nfs_dns_ent_alloc(void)121 static 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 
nfs_dns_hash(const struct nfs_dns_ent * key)134 static unsigned int nfs_dns_hash(const struct nfs_dns_ent *key)
135 {
136 	return hash_str(key->hostname, NFS_DNS_HASHBITS);
137 }
138 
nfs_dns_request(struct cache_detail * cd,struct cache_head * ch,char ** bpp,int * blen)139 static 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 
nfs_dns_upcall(struct cache_detail * cd,struct cache_head * ch)149 static 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 
nfs_dns_match(struct cache_head * ca,struct cache_head * cb)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 
nfs_dns_show(struct seq_file * m,struct cache_detail * cd,struct cache_head * h)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 
nfs_dns_lookup(struct cache_detail * cd,struct nfs_dns_ent * key)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 
nfs_dns_update(struct cache_detail * cd,struct nfs_dns_ent * new,struct nfs_dns_ent * key)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 
nfs_dns_parse(struct cache_detail * cd,char * buf,int buflen)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 
do_cache_lookup(struct cache_detail * cd,struct nfs_dns_ent * key,struct nfs_dns_ent ** item,struct nfs_cache_defer_req * dreq)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 
do_cache_lookup_nowait(struct cache_detail * cd,struct nfs_dns_ent * key,struct nfs_dns_ent ** item)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 
do_cache_lookup_wait(struct cache_detail * cd,struct nfs_dns_ent * key,struct nfs_dns_ent ** item)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 
nfs_dns_resolve_name(struct net * net,char * name,size_t namelen,struct sockaddr_storage * ss,size_t salen)342 ssize_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 
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 
nfs_dns_resolver_cache_init(struct net * net)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 
nfs_dns_resolver_cache_destroy(struct net * net)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 
nfs4_dns_net_init(struct net * net)409 static int nfs4_dns_net_init(struct net *net)
410 {
411 	return nfs_dns_resolver_cache_init(net);
412 }
413 
nfs4_dns_net_exit(struct net * net)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 
rpc_pipefs_event(struct notifier_block * nb,unsigned long event,void * ptr)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 
nfs_dns_resolver_init(void)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 
nfs_dns_resolver_destroy(void)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