xref: /kernel/linux/linux-6.6/fs/afs/vl_list.c (revision 62306a36) 
1// SPDX-License-Identifier: GPL-2.0-or-later
2/* AFS vlserver list management.
3 *
4 * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8#include <linux/kernel.h>
9#include <linux/slab.h>
10#include "internal.h"
11
12struct afs_vlserver *afs_alloc_vlserver(const char *name, size_t name_len,
13					unsigned short port)
14{
15	struct afs_vlserver *vlserver;
16
17	vlserver = kzalloc(struct_size(vlserver, name, name_len + 1),
18			   GFP_KERNEL);
19	if (vlserver) {
20		refcount_set(&vlserver->ref, 1);
21		rwlock_init(&vlserver->lock);
22		init_waitqueue_head(&vlserver->probe_wq);
23		spin_lock_init(&vlserver->probe_lock);
24		vlserver->rtt = UINT_MAX;
25		vlserver->name_len = name_len;
26		vlserver->port = port;
27		memcpy(vlserver->name, name, name_len);
28	}
29	return vlserver;
30}
31
32static void afs_vlserver_rcu(struct rcu_head *rcu)
33{
34	struct afs_vlserver *vlserver = container_of(rcu, struct afs_vlserver, rcu);
35
36	afs_put_addrlist(rcu_access_pointer(vlserver->addresses));
37	kfree_rcu(vlserver, rcu);
38}
39
40void afs_put_vlserver(struct afs_net *net, struct afs_vlserver *vlserver)
41{
42	if (vlserver &&
43	    refcount_dec_and_test(&vlserver->ref))
44		call_rcu(&vlserver->rcu, afs_vlserver_rcu);
45}
46
47struct afs_vlserver_list *afs_alloc_vlserver_list(unsigned int nr_servers)
48{
49	struct afs_vlserver_list *vllist;
50
51	vllist = kzalloc(struct_size(vllist, servers, nr_servers), GFP_KERNEL);
52	if (vllist) {
53		refcount_set(&vllist->ref, 1);
54		rwlock_init(&vllist->lock);
55	}
56
57	return vllist;
58}
59
60void afs_put_vlserverlist(struct afs_net *net, struct afs_vlserver_list *vllist)
61{
62	if (vllist) {
63		if (refcount_dec_and_test(&vllist->ref)) {
64			int i;
65
66			for (i = 0; i < vllist->nr_servers; i++) {
67				afs_put_vlserver(net, vllist->servers[i].server);
68			}
69			kfree_rcu(vllist, rcu);
70		}
71	}
72}
73
74static u16 afs_extract_le16(const u8 **_b)
75{
76	u16 val;
77
78	val  = (u16)*(*_b)++ << 0;
79	val |= (u16)*(*_b)++ << 8;
80	return val;
81}
82
83/*
84 * Build a VL server address list from a DNS queried server list.
85 */
86static struct afs_addr_list *afs_extract_vl_addrs(const u8 **_b, const u8 *end,
87						  u8 nr_addrs, u16 port)
88{
89	struct afs_addr_list *alist;
90	const u8 *b = *_b;
91	int ret = -EINVAL;
92
93	alist = afs_alloc_addrlist(nr_addrs, VL_SERVICE, port);
94	if (!alist)
95		return ERR_PTR(-ENOMEM);
96	if (nr_addrs == 0)
97		return alist;
98
99	for (; nr_addrs > 0 && end - b >= nr_addrs; nr_addrs--) {
100		struct dns_server_list_v1_address hdr;
101		__be32 x[4];
102
103		hdr.address_type = *b++;
104
105		switch (hdr.address_type) {
106		case DNS_ADDRESS_IS_IPV4:
107			if (end - b < 4) {
108				_leave(" = -EINVAL [short inet]");
109				goto error;
110			}
111			memcpy(x, b, 4);
112			afs_merge_fs_addr4(alist, x[0], port);
113			b += 4;
114			break;
115
116		case DNS_ADDRESS_IS_IPV6:
117			if (end - b < 16) {
118				_leave(" = -EINVAL [short inet6]");
119				goto error;
120			}
121			memcpy(x, b, 16);
122			afs_merge_fs_addr6(alist, x, port);
123			b += 16;
124			break;
125
126		default:
127			_leave(" = -EADDRNOTAVAIL [unknown af %u]",
128			       hdr.address_type);
129			ret = -EADDRNOTAVAIL;
130			goto error;
131		}
132	}
133
134	/* Start with IPv6 if available. */
135	if (alist->nr_ipv4 < alist->nr_addrs)
136		alist->preferred = alist->nr_ipv4;
137
138	*_b = b;
139	return alist;
140
141error:
142	*_b = b;
143	afs_put_addrlist(alist);
144	return ERR_PTR(ret);
145}
146
147/*
148 * Build a VL server list from a DNS queried server list.
149 */
150struct afs_vlserver_list *afs_extract_vlserver_list(struct afs_cell *cell,
151						    const void *buffer,
152						    size_t buffer_size)
153{
154	const struct dns_server_list_v1_header *hdr = buffer;
155	struct dns_server_list_v1_server bs;
156	struct afs_vlserver_list *vllist, *previous;
157	struct afs_addr_list *addrs;
158	struct afs_vlserver *server;
159	const u8 *b = buffer, *end = buffer + buffer_size;
160	int ret = -ENOMEM, nr_servers, i, j;
161
162	_enter("");
163
164	/* Check that it's a server list, v1 */
165	if (end - b < sizeof(*hdr) ||
166	    hdr->hdr.content != DNS_PAYLOAD_IS_SERVER_LIST ||
167	    hdr->hdr.version != 1) {
168		pr_notice("kAFS: Got DNS record [%u,%u] len %zu\n",
169			  hdr->hdr.content, hdr->hdr.version, end - b);
170		ret = -EDESTADDRREQ;
171		goto dump;
172	}
173
174	nr_servers = hdr->nr_servers;
175
176	vllist = afs_alloc_vlserver_list(nr_servers);
177	if (!vllist)
178		return ERR_PTR(-ENOMEM);
179
180	vllist->source = (hdr->source < NR__dns_record_source) ?
181		hdr->source : NR__dns_record_source;
182	vllist->status = (hdr->status < NR__dns_lookup_status) ?
183		hdr->status : NR__dns_lookup_status;
184
185	read_lock(&cell->vl_servers_lock);
186	previous = afs_get_vlserverlist(
187		rcu_dereference_protected(cell->vl_servers,
188					  lockdep_is_held(&cell->vl_servers_lock)));
189	read_unlock(&cell->vl_servers_lock);
190
191	b += sizeof(*hdr);
192	while (end - b >= sizeof(bs)) {
193		bs.name_len	= afs_extract_le16(&b);
194		bs.priority	= afs_extract_le16(&b);
195		bs.weight	= afs_extract_le16(&b);
196		bs.port		= afs_extract_le16(&b);
197		bs.source	= *b++;
198		bs.status	= *b++;
199		bs.protocol	= *b++;
200		bs.nr_addrs	= *b++;
201
202		_debug("extract %u %u %u %u %u %u %*.*s",
203		       bs.name_len, bs.priority, bs.weight,
204		       bs.port, bs.protocol, bs.nr_addrs,
205		       bs.name_len, bs.name_len, b);
206
207		if (end - b < bs.name_len)
208			break;
209
210		ret = -EPROTONOSUPPORT;
211		if (bs.protocol == DNS_SERVER_PROTOCOL_UNSPECIFIED) {
212			bs.protocol = DNS_SERVER_PROTOCOL_UDP;
213		} else if (bs.protocol != DNS_SERVER_PROTOCOL_UDP) {
214			_leave(" = [proto %u]", bs.protocol);
215			goto error;
216		}
217
218		if (bs.port == 0)
219			bs.port = AFS_VL_PORT;
220		if (bs.source > NR__dns_record_source)
221			bs.source = NR__dns_record_source;
222		if (bs.status > NR__dns_lookup_status)
223			bs.status = NR__dns_lookup_status;
224
225		/* See if we can update an old server record */
226		server = NULL;
227		for (i = 0; i < previous->nr_servers; i++) {
228			struct afs_vlserver *p = previous->servers[i].server;
229
230			if (p->name_len == bs.name_len &&
231			    p->port == bs.port &&
232			    strncasecmp(b, p->name, bs.name_len) == 0) {
233				server = afs_get_vlserver(p);
234				break;
235			}
236		}
237
238		if (!server) {
239			ret = -ENOMEM;
240			server = afs_alloc_vlserver(b, bs.name_len, bs.port);
241			if (!server)
242				goto error;
243		}
244
245		b += bs.name_len;
246
247		/* Extract the addresses - note that we can't skip this as we
248		 * have to advance the payload pointer.
249		 */
250		addrs = afs_extract_vl_addrs(&b, end, bs.nr_addrs, bs.port);
251		if (IS_ERR(addrs)) {
252			ret = PTR_ERR(addrs);
253			goto error_2;
254		}
255
256		if (vllist->nr_servers >= nr_servers) {
257			_debug("skip %u >= %u", vllist->nr_servers, nr_servers);
258			afs_put_addrlist(addrs);
259			afs_put_vlserver(cell->net, server);
260			continue;
261		}
262
263		addrs->source = bs.source;
264		addrs->status = bs.status;
265
266		if (addrs->nr_addrs == 0) {
267			afs_put_addrlist(addrs);
268			if (!rcu_access_pointer(server->addresses)) {
269				afs_put_vlserver(cell->net, server);
270				continue;
271			}
272		} else {
273			struct afs_addr_list *old = addrs;
274
275			write_lock(&server->lock);
276			old = rcu_replace_pointer(server->addresses, old,
277						  lockdep_is_held(&server->lock));
278			write_unlock(&server->lock);
279			afs_put_addrlist(old);
280		}
281
282
283		/* TODO: Might want to check for duplicates */
284
285		/* Insertion-sort by priority and weight */
286		for (j = 0; j < vllist->nr_servers; j++) {
287			if (bs.priority < vllist->servers[j].priority)
288				break; /* Lower preferable */
289			if (bs.priority == vllist->servers[j].priority &&
290			    bs.weight > vllist->servers[j].weight)
291				break; /* Higher preferable */
292		}
293
294		if (j < vllist->nr_servers) {
295			memmove(vllist->servers + j + 1,
296				vllist->servers + j,
297				(vllist->nr_servers - j) * sizeof(struct afs_vlserver_entry));
298		}
299
300		clear_bit(AFS_VLSERVER_FL_PROBED, &server->flags);
301
302		vllist->servers[j].priority = bs.priority;
303		vllist->servers[j].weight = bs.weight;
304		vllist->servers[j].server = server;
305		vllist->nr_servers++;
306	}
307
308	if (b != end) {
309		_debug("parse error %zd", b - end);
310		goto error;
311	}
312
313	afs_put_vlserverlist(cell->net, previous);
314	_leave(" = ok [%u]", vllist->nr_servers);
315	return vllist;
316
317error_2:
318	afs_put_vlserver(cell->net, server);
319error:
320	afs_put_vlserverlist(cell->net, vllist);
321	afs_put_vlserverlist(cell->net, previous);
322dump:
323	if (ret != -ENOMEM) {
324		printk(KERN_DEBUG "DNS: at %zu\n", (const void *)b - buffer);
325		print_hex_dump_bytes("DNS: ", DUMP_PREFIX_NONE, buffer, buffer_size);
326	}
327	return ERR_PTR(ret);
328}
329