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, &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
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