1 /* Server address list management
2 *
3 * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11
12 #include <linux/slab.h>
13 #include <linux/ctype.h>
14 #include <linux/dns_resolver.h>
15 #include <linux/inet.h>
16 #include <keys/rxrpc-type.h>
17 #include "internal.h"
18 #include "afs_fs.h"
19
20 //#define AFS_MAX_ADDRESSES
21 // ((unsigned int)((PAGE_SIZE - sizeof(struct afs_addr_list)) /
22 // sizeof(struct sockaddr_rxrpc)))
23 #define AFS_MAX_ADDRESSES ((unsigned int)(sizeof(unsigned long) * 8))
24
25 /*
26 * Release an address list.
27 */
afs_put_addrlist(struct afs_addr_list * alist)28 void afs_put_addrlist(struct afs_addr_list *alist)
29 {
30 if (alist && refcount_dec_and_test(&alist->usage))
31 call_rcu(&alist->rcu, (rcu_callback_t)kfree);
32 }
33
34 /*
35 * Allocate an address list.
36 */
afs_alloc_addrlist(unsigned int nr,unsigned short service,unsigned short port)37 struct afs_addr_list *afs_alloc_addrlist(unsigned int nr,
38 unsigned short service,
39 unsigned short port)
40 {
41 struct afs_addr_list *alist;
42 unsigned int i;
43
44 _enter("%u,%u,%u", nr, service, port);
45
46 alist = kzalloc(struct_size(alist, addrs, nr), GFP_KERNEL);
47 if (!alist)
48 return NULL;
49
50 refcount_set(&alist->usage, 1);
51
52 for (i = 0; i < nr; i++) {
53 struct sockaddr_rxrpc *srx = &alist->addrs[i];
54 srx->srx_family = AF_RXRPC;
55 srx->srx_service = service;
56 srx->transport_type = SOCK_DGRAM;
57 srx->transport_len = sizeof(srx->transport.sin6);
58 srx->transport.sin6.sin6_family = AF_INET6;
59 srx->transport.sin6.sin6_port = htons(port);
60 }
61
62 return alist;
63 }
64
65 /*
66 * Parse a text string consisting of delimited addresses.
67 */
afs_parse_text_addrs(const char * text,size_t len,char delim,unsigned short service,unsigned short port)68 struct afs_addr_list *afs_parse_text_addrs(const char *text, size_t len,
69 char delim,
70 unsigned short service,
71 unsigned short port)
72 {
73 struct afs_addr_list *alist;
74 const char *p, *end = text + len;
75 unsigned int nr = 0;
76
77 _enter("%*.*s,%c", (int)len, (int)len, text, delim);
78
79 if (!len)
80 return ERR_PTR(-EDESTADDRREQ);
81
82 if (delim == ':' && (memchr(text, ',', len) || !memchr(text, '.', len)))
83 delim = ',';
84
85 /* Count the addresses */
86 p = text;
87 do {
88 if (!*p)
89 return ERR_PTR(-EINVAL);
90 if (*p == delim)
91 continue;
92 nr++;
93 if (*p == '[') {
94 p++;
95 if (p == end)
96 return ERR_PTR(-EINVAL);
97 p = memchr(p, ']', end - p);
98 if (!p)
99 return ERR_PTR(-EINVAL);
100 p++;
101 if (p >= end)
102 break;
103 }
104
105 p = memchr(p, delim, end - p);
106 if (!p)
107 break;
108 p++;
109 } while (p < end);
110
111 _debug("%u/%u addresses", nr, AFS_MAX_ADDRESSES);
112 if (nr > AFS_MAX_ADDRESSES)
113 nr = AFS_MAX_ADDRESSES;
114
115 alist = afs_alloc_addrlist(nr, service, port);
116 if (!alist)
117 return ERR_PTR(-ENOMEM);
118
119 /* Extract the addresses */
120 p = text;
121 do {
122 struct sockaddr_rxrpc *srx = &alist->addrs[alist->nr_addrs];
123 const char *q, *stop;
124
125 if (*p == delim) {
126 p++;
127 continue;
128 }
129
130 if (*p == '[') {
131 p++;
132 q = memchr(p, ']', end - p);
133 } else {
134 for (q = p; q < end; q++)
135 if (*q == '+' || *q == delim)
136 break;
137 }
138
139 if (in4_pton(p, q - p,
140 (u8 *)&srx->transport.sin6.sin6_addr.s6_addr32[3],
141 -1, &stop)) {
142 srx->transport.sin6.sin6_addr.s6_addr32[0] = 0;
143 srx->transport.sin6.sin6_addr.s6_addr32[1] = 0;
144 srx->transport.sin6.sin6_addr.s6_addr32[2] = htonl(0xffff);
145 } else if (in6_pton(p, q - p,
146 srx->transport.sin6.sin6_addr.s6_addr,
147 -1, &stop)) {
148 /* Nothing to do */
149 } else {
150 goto bad_address;
151 }
152
153 if (stop != q)
154 goto bad_address;
155
156 p = q;
157 if (q < end && *q == ']')
158 p++;
159
160 if (p < end) {
161 if (*p == '+') {
162 /* Port number specification "+1234" */
163 unsigned int xport = 0;
164 p++;
165 if (p >= end || !isdigit(*p))
166 goto bad_address;
167 do {
168 xport *= 10;
169 xport += *p - '0';
170 if (xport > 65535)
171 goto bad_address;
172 p++;
173 } while (p < end && isdigit(*p));
174 srx->transport.sin6.sin6_port = htons(xport);
175 } else if (*p == delim) {
176 p++;
177 } else {
178 goto bad_address;
179 }
180 }
181
182 alist->nr_addrs++;
183 } while (p < end && alist->nr_addrs < AFS_MAX_ADDRESSES);
184
185 _leave(" = [nr %u]", alist->nr_addrs);
186 return alist;
187
188 bad_address:
189 kfree(alist);
190 return ERR_PTR(-EINVAL);
191 }
192
193 /*
194 * Compare old and new address lists to see if there's been any change.
195 * - How to do this in better than O(Nlog(N)) time?
196 * - We don't really want to sort the address list, but would rather take the
197 * list as we got it so as not to undo record rotation by the DNS server.
198 */
199 #if 0
200 static int afs_cmp_addr_list(const struct afs_addr_list *a1,
201 const struct afs_addr_list *a2)
202 {
203 }
204 #endif
205
206 /*
207 * Perform a DNS query for VL servers and build a up an address list.
208 */
afs_dns_query(struct afs_cell * cell,time64_t * _expiry)209 struct afs_addr_list *afs_dns_query(struct afs_cell *cell, time64_t *_expiry)
210 {
211 struct afs_addr_list *alist;
212 char *vllist = NULL;
213 int ret;
214
215 _enter("%s", cell->name);
216
217 ret = dns_query("afsdb", cell->name, cell->name_len,
218 "", &vllist, _expiry);
219 if (ret < 0)
220 return ERR_PTR(ret);
221
222 alist = afs_parse_text_addrs(vllist, strlen(vllist), ',',
223 VL_SERVICE, AFS_VL_PORT);
224 if (IS_ERR(alist)) {
225 kfree(vllist);
226 if (alist != ERR_PTR(-ENOMEM))
227 pr_err("Failed to parse DNS data\n");
228 return alist;
229 }
230
231 kfree(vllist);
232 return alist;
233 }
234
235 /*
236 * Merge an IPv4 entry into a fileserver address list.
237 */
afs_merge_fs_addr4(struct afs_addr_list * alist,__be32 xdr,u16 port)238 void afs_merge_fs_addr4(struct afs_addr_list *alist, __be32 xdr, u16 port)
239 {
240 struct sockaddr_in6 *a;
241 __be16 xport = htons(port);
242 int i;
243
244 for (i = 0; i < alist->nr_ipv4; i++) {
245 a = &alist->addrs[i].transport.sin6;
246 if (xdr == a->sin6_addr.s6_addr32[3] &&
247 xport == a->sin6_port)
248 return;
249 if (xdr == a->sin6_addr.s6_addr32[3] &&
250 (u16 __force)xport < (u16 __force)a->sin6_port)
251 break;
252 if ((u32 __force)xdr < (u32 __force)a->sin6_addr.s6_addr32[3])
253 break;
254 }
255
256 if (i < alist->nr_addrs)
257 memmove(alist->addrs + i + 1,
258 alist->addrs + i,
259 sizeof(alist->addrs[0]) * (alist->nr_addrs - i));
260
261 a = &alist->addrs[i].transport.sin6;
262 a->sin6_port = xport;
263 a->sin6_addr.s6_addr32[0] = 0;
264 a->sin6_addr.s6_addr32[1] = 0;
265 a->sin6_addr.s6_addr32[2] = htonl(0xffff);
266 a->sin6_addr.s6_addr32[3] = xdr;
267 alist->nr_ipv4++;
268 alist->nr_addrs++;
269 }
270
271 /*
272 * Merge an IPv6 entry into a fileserver address list.
273 */
afs_merge_fs_addr6(struct afs_addr_list * alist,__be32 * xdr,u16 port)274 void afs_merge_fs_addr6(struct afs_addr_list *alist, __be32 *xdr, u16 port)
275 {
276 struct sockaddr_in6 *a;
277 __be16 xport = htons(port);
278 int i, diff;
279
280 for (i = alist->nr_ipv4; i < alist->nr_addrs; i++) {
281 a = &alist->addrs[i].transport.sin6;
282 diff = memcmp(xdr, &a->sin6_addr, 16);
283 if (diff == 0 &&
284 xport == a->sin6_port)
285 return;
286 if (diff == 0 &&
287 (u16 __force)xport < (u16 __force)a->sin6_port)
288 break;
289 if (diff < 0)
290 break;
291 }
292
293 if (i < alist->nr_addrs)
294 memmove(alist->addrs + i + 1,
295 alist->addrs + i,
296 sizeof(alist->addrs[0]) * (alist->nr_addrs - i));
297
298 a = &alist->addrs[i].transport.sin6;
299 a->sin6_port = xport;
300 a->sin6_addr.s6_addr32[0] = xdr[0];
301 a->sin6_addr.s6_addr32[1] = xdr[1];
302 a->sin6_addr.s6_addr32[2] = xdr[2];
303 a->sin6_addr.s6_addr32[3] = xdr[3];
304 alist->nr_addrs++;
305 }
306
307 /*
308 * Get an address to try.
309 */
afs_iterate_addresses(struct afs_addr_cursor * ac)310 bool afs_iterate_addresses(struct afs_addr_cursor *ac)
311 {
312 _enter("%hu+%hd", ac->start, (short)ac->index);
313
314 if (!ac->alist)
315 return false;
316
317 if (ac->begun) {
318 ac->index++;
319 if (ac->index == ac->alist->nr_addrs)
320 ac->index = 0;
321
322 if (ac->index == ac->start) {
323 ac->error = -EDESTADDRREQ;
324 return false;
325 }
326 }
327
328 ac->begun = true;
329 ac->responded = false;
330 ac->addr = &ac->alist->addrs[ac->index];
331 return true;
332 }
333
334 /*
335 * Release an address list cursor.
336 */
afs_end_cursor(struct afs_addr_cursor * ac)337 int afs_end_cursor(struct afs_addr_cursor *ac)
338 {
339 struct afs_addr_list *alist;
340
341 alist = ac->alist;
342 if (alist) {
343 if (ac->responded && ac->index != ac->start)
344 WRITE_ONCE(alist->index, ac->index);
345 afs_put_addrlist(alist);
346 }
347
348 ac->addr = NULL;
349 ac->alist = NULL;
350 ac->begun = false;
351 return ac->error;
352 }
353
354 /*
355 * Set the address cursor for iterating over VL servers.
356 */
afs_set_vl_cursor(struct afs_addr_cursor * ac,struct afs_cell * cell)357 int afs_set_vl_cursor(struct afs_addr_cursor *ac, struct afs_cell *cell)
358 {
359 struct afs_addr_list *alist;
360 int ret;
361
362 if (!rcu_access_pointer(cell->vl_addrs)) {
363 ret = wait_on_bit(&cell->flags, AFS_CELL_FL_NO_LOOKUP_YET,
364 TASK_INTERRUPTIBLE);
365 if (ret < 0)
366 return ret;
367
368 if (!rcu_access_pointer(cell->vl_addrs) &&
369 ktime_get_real_seconds() < cell->dns_expiry)
370 return cell->error;
371 }
372
373 read_lock(&cell->vl_addrs_lock);
374 alist = rcu_dereference_protected(cell->vl_addrs,
375 lockdep_is_held(&cell->vl_addrs_lock));
376 if (alist->nr_addrs > 0)
377 afs_get_addrlist(alist);
378 else
379 alist = NULL;
380 read_unlock(&cell->vl_addrs_lock);
381
382 if (!alist)
383 return -EDESTADDRREQ;
384
385 ac->alist = alist;
386 ac->addr = NULL;
387 ac->start = READ_ONCE(alist->index);
388 ac->index = ac->start;
389 ac->error = 0;
390 ac->begun = false;
391 return 0;
392 }
393