1 /* $NetBSD: getaddrinfo.c,v 1.82 2006/03/25 12:09:40 rpaulo Exp $ */
2 /* $KAME: getaddrinfo.c,v 1.29 2000/08/31 17:26:57 itojun Exp $ */
3
4 /*
5 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the project nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33 #define LOG_TAG "resolv"
34
35 #include "getaddrinfo.h"
36
37 #include <arpa/inet.h>
38 #include <arpa/nameser.h>
39 #include <assert.h>
40 #include <ctype.h>
41 #include <fcntl.h>
42 #include <net/if.h>
43 #include <netdb.h>
44 #include <netinet/in.h>
45 #include <stdbool.h>
46 #include <stddef.h>
47 #include <stdlib.h>
48 #include <string.h>
49 #include <sys/param.h>
50 #include <sys/socket.h>
51 #include <sys/stat.h>
52 #include <sys/un.h>
53 #include <unistd.h>
54
55 #include <chrono>
56 #include <future>
57
58 #include <android-base/logging.h>
59 #include <android-base/parseint.h>
60
61 #include "Experiments.h"
62 #include "netd_resolv/resolv.h"
63 #include "res_comp.h"
64 #include "res_debug.h"
65 #include "resolv_cache.h"
66 #include "resolv_private.h"
67
68 #define ANY 0
69
70 using android::net::Experiments;
71 using android::net::NetworkDnsEventReported;
72
73 const char in_addrany[] = {0, 0, 0, 0};
74 const char in_loopback[] = {127, 0, 0, 1};
75 const char in6_addrany[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
76 const char in6_loopback[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1};
77
78 const struct afd {
79 int a_af;
80 int a_addrlen;
81 int a_socklen;
82 int a_off;
83 const char* a_addrany;
84 const char* a_loopback;
85 int a_scoped;
86 } afdl[] = {
87 {PF_INET6, sizeof(struct in6_addr), sizeof(struct sockaddr_in6),
88 offsetof(struct sockaddr_in6, sin6_addr), in6_addrany, in6_loopback, 1},
89 {PF_INET, sizeof(struct in_addr), sizeof(struct sockaddr_in),
90 offsetof(struct sockaddr_in, sin_addr), in_addrany, in_loopback, 0},
91 {0, 0, 0, 0, NULL, NULL, 0},
92 };
93
94 struct Explore {
95 int e_af;
96 int e_socktype;
97 int e_protocol;
98 int e_wild;
99 #define WILD_AF(ex) ((ex).e_wild & 0x01)
100 #define WILD_SOCKTYPE(ex) ((ex).e_wild & 0x02)
101 #define WILD_PROTOCOL(ex) ((ex).e_wild & 0x04)
102 };
103
104 const Explore explore_options[] = {
105 {PF_INET6, SOCK_DGRAM, IPPROTO_UDP, 0x07},
106 {PF_INET6, SOCK_STREAM, IPPROTO_TCP, 0x07},
107 {PF_INET6, SOCK_RAW, ANY, 0x05},
108 {PF_INET, SOCK_DGRAM, IPPROTO_UDP, 0x07},
109 {PF_INET, SOCK_STREAM, IPPROTO_TCP, 0x07},
110 {PF_INET, SOCK_RAW, ANY, 0x05},
111 {PF_UNSPEC, SOCK_DGRAM, IPPROTO_UDP, 0x07},
112 {PF_UNSPEC, SOCK_STREAM, IPPROTO_TCP, 0x07},
113 {PF_UNSPEC, SOCK_RAW, ANY, 0x05},
114 };
115
116 #define PTON_MAX 16
117
118 struct res_target {
119 struct res_target* next;
120 const char* name; // domain name
121 int qclass, qtype; // class and type of query
122 std::vector<uint8_t> answer = std::vector<uint8_t>(MAXPACKET, 0); // buffer to put answer
123 int n = 0; // result length
124 };
125
126 static int explore_fqdn(const struct addrinfo*, const char*, const char*, struct addrinfo**,
127 const struct android_net_context*, NetworkDnsEventReported* event);
128 static int explore_null(const struct addrinfo*, const char*, struct addrinfo**);
129 static int explore_numeric(const struct addrinfo*, const char*, const char*, struct addrinfo**,
130 const char*);
131 static int explore_numeric_scope(const struct addrinfo*, const char*, const char*,
132 struct addrinfo**);
133 static int get_canonname(const struct addrinfo*, struct addrinfo*, const char*);
134 static struct addrinfo* get_ai(const struct addrinfo*, const struct afd*, const char*);
135 static int get_portmatch(const struct addrinfo*, const char*);
136 static int get_port(const struct addrinfo*, const char*, int);
137 static const struct afd* find_afd(int);
138 static int ip6_str2scopeid(const char*, struct sockaddr_in6*, uint32_t*);
139
140 static struct addrinfo* getanswer(const std::vector<uint8_t>&, int, const char*, int,
141 const struct addrinfo*, int* herrno);
142 static int dns_getaddrinfo(const char* name, const addrinfo* pai,
143 const android_net_context* netcontext, addrinfo** rv,
144 NetworkDnsEventReported* event);
145 static void _sethtent(FILE**);
146 static void _endhtent(FILE**);
147 static struct addrinfo* _gethtent(FILE**, const char*, const struct addrinfo*);
148 static struct addrinfo* getCustomHosts(const size_t netid, const char*, const struct addrinfo*);
149 static bool files_getaddrinfo(const size_t netid, const char* name, const addrinfo* pai,
150 addrinfo** res);
151 static int _find_src_addr(const struct sockaddr*, struct sockaddr*, unsigned, uid_t,
152 bool allow_v6_linklocal);
153
154 static int res_searchN(const char* name, res_target* target, ResState* res, int* herrno);
155 static int res_querydomainN(const char* name, const char* domain, res_target* target, ResState* res,
156 int* herrno);
157
158 const char* const ai_errlist[] = {
159 "Success",
160 "Address family for hostname not supported", /* EAI_ADDRFAMILY */
161 "Temporary failure in name resolution", /* EAI_AGAIN */
162 "Invalid value for ai_flags", /* EAI_BADFLAGS */
163 "Non-recoverable failure in name resolution", /* EAI_FAIL */
164 "ai_family not supported", /* EAI_FAMILY */
165 "Memory allocation failure", /* EAI_MEMORY */
166 "No address associated with hostname", /* EAI_NODATA */
167 "hostname nor servname provided, or not known", /* EAI_NONAME */
168 "servname not supported for ai_socktype", /* EAI_SERVICE */
169 "ai_socktype not supported", /* EAI_SOCKTYPE */
170 "System error returned in errno", /* EAI_SYSTEM */
171 "Invalid value for hints", /* EAI_BADHINTS */
172 "Resolved protocol is unknown", /* EAI_PROTOCOL */
173 "Argument buffer overflow", /* EAI_OVERFLOW */
174 "Unknown error", /* EAI_MAX */
175 };
176
177 /* XXX macros that make external reference is BAD. */
178
179 #define GET_AI(ai, afd, addr) \
180 do { \
181 /* external reference: pai, error, and label free */ \
182 (ai) = get_ai(pai, (afd), (addr)); \
183 if ((ai) == NULL) { \
184 error = EAI_MEMORY; \
185 goto free; \
186 } \
187 } while (0)
188
189 #define GET_PORT(ai, serv) \
190 do { \
191 /* external reference: error and label free */ \
192 error = get_port((ai), (serv), 0); \
193 if (error != 0) goto free; \
194 } while (0)
195
196 #define MATCH_FAMILY(x, y, w) \
197 ((x) == (y) || ((w) && ((x) == PF_UNSPEC || (y) == PF_UNSPEC)))
198 #define MATCH(x, y, w) ((x) == (y) || ((w) && ((x) == ANY || (y) == ANY)))
199
gai_strerror(int ecode)200 const char* gai_strerror(int ecode) {
201 if (ecode < 0 || ecode > EAI_MAX) ecode = EAI_MAX;
202 return ai_errlist[ecode];
203 }
204
freeaddrinfo(struct addrinfo * ai)205 void freeaddrinfo(struct addrinfo* ai) {
206 while (ai) {
207 struct addrinfo* next = ai->ai_next;
208 if (ai->ai_canonname) free(ai->ai_canonname);
209 // Also frees ai->ai_addr which points to extra space beyond addrinfo
210 free(ai);
211 ai = next;
212 }
213 }
214
215 /*
216 * The following functions determine whether IPv4 or IPv6 connectivity is
217 * available in order to implement AI_ADDRCONFIG.
218 *
219 * Strictly speaking, AI_ADDRCONFIG should not look at whether connectivity is
220 * available, but whether addresses of the specified family are "configured
221 * on the local system". However, bionic doesn't currently support getifaddrs,
222 * so checking for connectivity is the next best thing.
223 */
have_ipv6(unsigned mark,uid_t uid,bool mdns)224 static int have_ipv6(unsigned mark, uid_t uid, bool mdns) {
225 static const struct sockaddr_in6 sin6_test = {
226 .sin6_family = AF_INET6,
227 .sin6_addr.s6_addr = {// 2000::
228 0x20, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}};
229 sockaddr_union addr = {.sin6 = sin6_test};
230 sockaddr sa;
231 return _find_src_addr(&addr.sa, &sa, mark, uid, /*allow_v6_linklocal=*/mdns) == 1;
232 }
233
have_ipv4(unsigned mark,uid_t uid)234 static int have_ipv4(unsigned mark, uid_t uid) {
235 static const struct sockaddr_in sin_test = {
236 .sin_family = AF_INET,
237 .sin_addr.s_addr = __constant_htonl(0x08080808L) // 8.8.8.8
238 };
239 sockaddr_union addr = {.sin = sin_test};
240 sockaddr sa;
241 return _find_src_addr(&addr.sa, &sa, mark, uid, /*(don't care) allow_v6_linklocal=*/false) == 1;
242 }
243
244 // Internal version of getaddrinfo(), but limited to AI_NUMERICHOST.
245 // NOTE: also called by resolv_set_nameservers().
getaddrinfo_numeric(const char * hostname,const char * servname,addrinfo hints,addrinfo ** result)246 int getaddrinfo_numeric(const char* hostname, const char* servname, addrinfo hints,
247 addrinfo** result) {
248 hints.ai_flags = AI_NUMERICHOST;
249 const android_net_context netcontext = {
250 .app_netid = NETID_UNSET,
251 .app_mark = MARK_UNSET,
252 .dns_netid = NETID_UNSET,
253 .dns_mark = MARK_UNSET,
254 .uid = NET_CONTEXT_INVALID_UID,
255 .pid = NET_CONTEXT_INVALID_PID,
256 };
257 NetworkDnsEventReported event;
258 return android_getaddrinfofornetcontext(hostname, servname, &hints, &netcontext, result,
259 &event);
260 }
261
262 namespace {
263
validateHints(const addrinfo * _Nonnull hints)264 int validateHints(const addrinfo* _Nonnull hints) {
265 if (!hints) return EAI_BADHINTS;
266
267 // error check for hints
268 if (hints->ai_addrlen || hints->ai_canonname || hints->ai_addr || hints->ai_next) {
269 return EAI_BADHINTS;
270 }
271 if (hints->ai_flags & ~AI_MASK) {
272 return EAI_BADFLAGS;
273 }
274 if (!(hints->ai_family == PF_UNSPEC || hints->ai_family == PF_INET ||
275 hints->ai_family == PF_INET6)) {
276 return EAI_FAMILY;
277 }
278
279 // Socket types which are not in explore_options.
280 switch (hints->ai_socktype) {
281 case SOCK_RAW:
282 case SOCK_DGRAM:
283 case SOCK_STREAM:
284 case ANY:
285 break;
286 default:
287 return EAI_SOCKTYPE;
288 }
289
290 if (hints->ai_socktype == ANY || hints->ai_protocol == ANY) return 0;
291
292 // if both socktype/protocol are specified, check if they are meaningful combination.
293 for (const Explore& ex : explore_options) {
294 if (hints->ai_family != ex.e_af) continue;
295 if (ex.e_socktype == ANY) continue;
296 if (ex.e_protocol == ANY) continue;
297 if (hints->ai_socktype == ex.e_socktype && hints->ai_protocol != ex.e_protocol) {
298 return EAI_BADHINTS;
299 }
300 }
301
302 return 0;
303 }
304
305 } // namespace
306
android_getaddrinfofornetcontext(const char * hostname,const char * servname,const addrinfo * hints,const android_net_context * netcontext,addrinfo ** res,NetworkDnsEventReported * event)307 int android_getaddrinfofornetcontext(const char* hostname, const char* servname,
308 const addrinfo* hints, const android_net_context* netcontext,
309 addrinfo** res, NetworkDnsEventReported* event) {
310 // hostname is allowed to be nullptr
311 // servname is allowed to be nullptr
312 // hints is allowed to be nullptr
313 assert(res != nullptr);
314 assert(netcontext != nullptr);
315 assert(event != nullptr);
316
317 addrinfo sentinel = {};
318 addrinfo* cur = &sentinel;
319 int error = 0;
320
321 do {
322 if (hostname == nullptr && servname == nullptr) {
323 error = EAI_NONAME;
324 break;
325 }
326
327 if (hints && (error = validateHints(hints))) break;
328 addrinfo ai = hints ? *hints : addrinfo{};
329
330 // Check for special cases:
331 // (1) numeric servname is disallowed if socktype/protocol are left unspecified.
332 // (2) servname is disallowed for raw and other inet{,6} sockets.
333 if (MATCH_FAMILY(ai.ai_family, PF_INET, 1) || MATCH_FAMILY(ai.ai_family, PF_INET6, 1)) {
334 addrinfo tmp = ai;
335 if (tmp.ai_family == PF_UNSPEC) {
336 tmp.ai_family = PF_INET6;
337 }
338 error = get_portmatch(&tmp, servname);
339 if (error) break;
340 }
341
342 // NULL hostname, or numeric hostname
343 for (const Explore& ex : explore_options) {
344 /* PF_UNSPEC entries are prepared for DNS queries only */
345 if (ex.e_af == PF_UNSPEC) continue;
346
347 if (!MATCH_FAMILY(ai.ai_family, ex.e_af, WILD_AF(ex))) continue;
348 if (!MATCH(ai.ai_socktype, ex.e_socktype, WILD_SOCKTYPE(ex))) continue;
349 if (!MATCH(ai.ai_protocol, ex.e_protocol, WILD_PROTOCOL(ex))) continue;
350
351 addrinfo tmp = ai;
352 if (tmp.ai_family == PF_UNSPEC) tmp.ai_family = ex.e_af;
353 if (tmp.ai_socktype == ANY && ex.e_socktype != ANY) tmp.ai_socktype = ex.e_socktype;
354 if (tmp.ai_protocol == ANY && ex.e_protocol != ANY) tmp.ai_protocol = ex.e_protocol;
355
356 LOG(DEBUG) << __func__ << ": explore_numeric: ai_family=" << tmp.ai_family
357 << " ai_socktype=" << tmp.ai_socktype << " ai_protocol=" << tmp.ai_protocol;
358 if (hostname == nullptr)
359 error = explore_null(&tmp, servname, &cur->ai_next);
360 else
361 error = explore_numeric_scope(&tmp, hostname, servname, &cur->ai_next);
362
363 if (error) break;
364
365 while (cur->ai_next) cur = cur->ai_next;
366 }
367 if (error) break;
368
369 // If numeric representation of AF1 can be interpreted as FQDN
370 // representation of AF2, we need to think again about the code below.
371 if (sentinel.ai_next) break;
372
373 if (hostname == nullptr) {
374 error = EAI_NODATA;
375 break;
376 }
377 if (ai.ai_flags & AI_NUMERICHOST) {
378 error = EAI_NONAME;
379 break;
380 }
381
382 return resolv_getaddrinfo(hostname, servname, hints, netcontext, res, event);
383 } while (0);
384
385 if (error) {
386 freeaddrinfo(sentinel.ai_next);
387 *res = nullptr;
388 } else {
389 *res = sentinel.ai_next;
390 }
391 return error;
392 }
393
resolv_getaddrinfo(const char * _Nonnull hostname,const char * servname,const addrinfo * hints,const android_net_context * _Nonnull netcontext,addrinfo ** _Nonnull res,NetworkDnsEventReported * _Nonnull event)394 int resolv_getaddrinfo(const char* _Nonnull hostname, const char* servname, const addrinfo* hints,
395 const android_net_context* _Nonnull netcontext, addrinfo** _Nonnull res,
396 NetworkDnsEventReported* _Nonnull event) {
397 if (hostname == nullptr && servname == nullptr) return EAI_NONAME;
398 if (hostname == nullptr) return EAI_NODATA;
399
400 // servname is allowed to be nullptr
401 // hints is allowed to be nullptr
402 assert(res != nullptr);
403 assert(netcontext != nullptr);
404 assert(event != nullptr);
405
406 int error = EAI_FAIL;
407 if (hints && (error = validateHints(hints))) {
408 *res = nullptr;
409 return error;
410 }
411
412 addrinfo ai = hints ? *hints : addrinfo{};
413 addrinfo sentinel = {};
414 addrinfo* cur = &sentinel;
415 // hostname as alphanumeric name.
416 // We would like to prefer AF_INET6 over AF_INET, so we'll make a outer loop by AFs.
417 for (const Explore& ex : explore_options) {
418 // Require exact match for family field
419 if (ai.ai_family != ex.e_af) continue;
420
421 if (!MATCH(ai.ai_socktype, ex.e_socktype, WILD_SOCKTYPE(ex))) continue;
422
423 if (!MATCH(ai.ai_protocol, ex.e_protocol, WILD_PROTOCOL(ex))) continue;
424
425 addrinfo tmp = ai;
426 if (tmp.ai_socktype == ANY && ex.e_socktype != ANY) tmp.ai_socktype = ex.e_socktype;
427 if (tmp.ai_protocol == ANY && ex.e_protocol != ANY) tmp.ai_protocol = ex.e_protocol;
428
429 LOG(DEBUG) << __func__ << ": explore_fqdn(): ai_family=" << tmp.ai_family
430 << " ai_socktype=" << tmp.ai_socktype << " ai_protocol=" << tmp.ai_protocol;
431 error = explore_fqdn(&tmp, hostname, servname, &cur->ai_next, netcontext, event);
432
433 while (cur->ai_next) cur = cur->ai_next;
434 }
435
436 // Propagate the last error from explore_fqdn(), but only when *all* attempts failed.
437 if ((*res = sentinel.ai_next)) return 0;
438
439 // TODO: consider removing freeaddrinfo.
440 freeaddrinfo(sentinel.ai_next);
441 *res = nullptr;
442 return (error == 0) ? EAI_FAIL : error;
443 }
444
445 // FQDN hostname, DNS lookup
explore_fqdn(const addrinfo * pai,const char * hostname,const char * servname,addrinfo ** res,const android_net_context * netcontext,NetworkDnsEventReported * event)446 static int explore_fqdn(const addrinfo* pai, const char* hostname, const char* servname,
447 addrinfo** res, const android_net_context* netcontext,
448 NetworkDnsEventReported* event) {
449 assert(pai != nullptr);
450 // hostname may be nullptr
451 // servname may be nullptr
452 assert(res != nullptr);
453
454 addrinfo* result = nullptr;
455 int error = 0;
456
457 // If the servname does not match socktype/protocol, return error code.
458 if ((error = get_portmatch(pai, servname))) return error;
459
460 if (!files_getaddrinfo(netcontext->dns_netid, hostname, pai, &result)) {
461 error = dns_getaddrinfo(hostname, pai, netcontext, &result, event);
462 }
463 if (error) {
464 freeaddrinfo(result);
465 return error;
466 }
467
468 for (addrinfo* cur = result; cur; cur = cur->ai_next) {
469 // canonname should be filled already
470 if ((error = get_port(cur, servname, 0))) {
471 freeaddrinfo(result);
472 return error;
473 }
474 }
475 *res = result;
476 return 0;
477 }
478
479 /*
480 * hostname == NULL.
481 * passive socket -> anyaddr (0.0.0.0 or ::)
482 * non-passive socket -> localhost (127.0.0.1 or ::1)
483 */
explore_null(const struct addrinfo * pai,const char * servname,struct addrinfo ** res)484 static int explore_null(const struct addrinfo* pai, const char* servname, struct addrinfo** res) {
485 int s;
486 const struct afd* afd;
487 struct addrinfo* cur;
488 struct addrinfo sentinel;
489 int error;
490
491 LOG(DEBUG) << __func__;
492
493 assert(pai != NULL);
494 /* servname may be NULL */
495 assert(res != NULL);
496
497 *res = NULL;
498 sentinel.ai_next = NULL;
499 cur = &sentinel;
500
501 /*
502 * filter out AFs that are not supported by the kernel
503 * XXX errno?
504 */
505 s = socket(pai->ai_family, SOCK_DGRAM | SOCK_CLOEXEC, 0);
506 if (s < 0) {
507 if (errno != EMFILE) return 0;
508 } else
509 close(s);
510
511 /*
512 * if the servname does not match socktype/protocol, ignore it.
513 */
514 if (get_portmatch(pai, servname) != 0) return 0;
515
516 afd = find_afd(pai->ai_family);
517 if (afd == NULL) return 0;
518
519 if (pai->ai_flags & AI_PASSIVE) {
520 GET_AI(cur->ai_next, afd, afd->a_addrany);
521 GET_PORT(cur->ai_next, servname);
522 } else {
523 GET_AI(cur->ai_next, afd, afd->a_loopback);
524 GET_PORT(cur->ai_next, servname);
525 }
526 cur = cur->ai_next;
527
528 *res = sentinel.ai_next;
529 return 0;
530
531 free:
532 freeaddrinfo(sentinel.ai_next);
533 return error;
534 }
535
536 /*
537 * numeric hostname
538 */
explore_numeric(const struct addrinfo * pai,const char * hostname,const char * servname,struct addrinfo ** res,const char * canonname)539 static int explore_numeric(const struct addrinfo* pai, const char* hostname, const char* servname,
540 struct addrinfo** res, const char* canonname) {
541 const struct afd* afd;
542 struct addrinfo* cur;
543 struct addrinfo sentinel;
544 int error;
545 char pton[PTON_MAX];
546
547 assert(pai != NULL);
548 /* hostname may be NULL */
549 /* servname may be NULL */
550 assert(res != NULL);
551
552 *res = NULL;
553 sentinel.ai_next = NULL;
554 cur = &sentinel;
555
556 /*
557 * if the servname does not match socktype/protocol, ignore it.
558 */
559 if (get_portmatch(pai, servname) != 0) return 0;
560
561 afd = find_afd(pai->ai_family);
562 if (afd == NULL) return 0;
563
564 if (inet_pton(afd->a_af, hostname, pton) == 1) {
565 if (pai->ai_family == afd->a_af || pai->ai_family == PF_UNSPEC /*?*/) {
566 GET_AI(cur->ai_next, afd, pton);
567 GET_PORT(cur->ai_next, servname);
568 if ((pai->ai_flags & AI_CANONNAME)) {
569 /*
570 * Set the numeric address itself as
571 * the canonical name, based on a
572 * clarification in rfc2553bis-03.
573 */
574 error = get_canonname(pai, cur->ai_next, canonname);
575 if (error != 0) {
576 freeaddrinfo(sentinel.ai_next);
577 return error;
578 }
579 }
580 while (cur->ai_next) cur = cur->ai_next;
581 } else
582 return EAI_FAMILY;
583 }
584
585 *res = sentinel.ai_next;
586 return 0;
587
588 free:
589 freeaddrinfo(sentinel.ai_next);
590 return error;
591 }
592
593 /*
594 * numeric hostname with scope
595 */
explore_numeric_scope(const struct addrinfo * pai,const char * hostname,const char * servname,struct addrinfo ** res)596 static int explore_numeric_scope(const struct addrinfo* pai, const char* hostname,
597 const char* servname, struct addrinfo** res) {
598 const struct afd* afd;
599 struct addrinfo* cur;
600 int error;
601 const char *cp, *scope, *addr;
602 struct sockaddr_in6* sin6;
603
604 LOG(DEBUG) << __func__;
605
606 assert(pai != NULL);
607 /* hostname may be NULL */
608 /* servname may be NULL */
609 assert(res != NULL);
610
611 /*
612 * if the servname does not match socktype/protocol, ignore it.
613 */
614 if (get_portmatch(pai, servname) != 0) return 0;
615
616 afd = find_afd(pai->ai_family);
617 if (afd == NULL) return 0;
618
619 if (!afd->a_scoped) return explore_numeric(pai, hostname, servname, res, hostname);
620
621 cp = strchr(hostname, SCOPE_DELIMITER);
622 if (cp == NULL) return explore_numeric(pai, hostname, servname, res, hostname);
623
624 /*
625 * Handle special case of <scoped_address><delimiter><scope id>
626 */
627 char* hostname2 = strdup(hostname);
628 if (hostname2 == NULL) return EAI_MEMORY;
629 /* terminate at the delimiter */
630 hostname2[cp - hostname] = '\0';
631 addr = hostname2;
632 scope = cp + 1;
633
634 error = explore_numeric(pai, addr, servname, res, hostname);
635 if (error == 0) {
636 uint32_t scopeid;
637
638 for (cur = *res; cur; cur = cur->ai_next) {
639 if (cur->ai_family != AF_INET6) continue;
640 sin6 = (struct sockaddr_in6*) (void*) cur->ai_addr;
641 if (ip6_str2scopeid(scope, sin6, &scopeid) == -1) {
642 free(hostname2);
643 return (EAI_NODATA); /* XXX: is return OK? */
644 }
645 sin6->sin6_scope_id = scopeid;
646 }
647 }
648
649 free(hostname2);
650
651 return error;
652 }
653
get_canonname(const struct addrinfo * pai,struct addrinfo * ai,const char * str)654 static int get_canonname(const struct addrinfo* pai, struct addrinfo* ai, const char* str) {
655 assert(pai != NULL);
656 assert(ai != NULL);
657 assert(str != NULL);
658
659 if ((pai->ai_flags & AI_CANONNAME) != 0) {
660 ai->ai_canonname = strdup(str);
661 if (ai->ai_canonname == NULL) return EAI_MEMORY;
662 }
663 return 0;
664 }
665
get_ai(const struct addrinfo * pai,const struct afd * afd,const char * addr)666 static struct addrinfo* get_ai(const struct addrinfo* pai, const struct afd* afd,
667 const char* addr) {
668 char* p;
669 struct addrinfo* ai;
670
671 assert(pai != NULL);
672 assert(afd != NULL);
673 assert(addr != NULL);
674
675 ai = (struct addrinfo*) calloc(1, sizeof(struct addrinfo) + sizeof(sockaddr_union));
676 if (ai == NULL) return NULL;
677
678 memcpy(ai, pai, sizeof(struct addrinfo));
679 ai->ai_addr = (struct sockaddr*) (void*) (ai + 1);
680 ai->ai_addrlen = afd->a_socklen;
681 ai->ai_addr->sa_family = ai->ai_family = afd->a_af;
682 p = (char*) (void*) (ai->ai_addr);
683 memcpy(p + afd->a_off, addr, (size_t) afd->a_addrlen);
684 return ai;
685 }
686
get_portmatch(const struct addrinfo * ai,const char * servname)687 static int get_portmatch(const struct addrinfo* ai, const char* servname) {
688 assert(ai != NULL);
689 /* servname may be NULL */
690
691 return get_port(ai, servname, 1);
692 }
693
get_port(const struct addrinfo * ai,const char * servname,int matchonly)694 static int get_port(const struct addrinfo* ai, const char* servname, int matchonly) {
695 const char* proto;
696 struct servent* sp;
697 uint port;
698 int allownumeric;
699
700 assert(ai != NULL);
701 /* servname may be NULL */
702
703 if (servname == NULL) return 0;
704 switch (ai->ai_family) {
705 case AF_INET:
706 case AF_INET6:
707 break;
708 default:
709 return 0;
710 }
711
712 switch (ai->ai_socktype) {
713 case SOCK_RAW:
714 return EAI_SERVICE;
715 case SOCK_DGRAM:
716 case SOCK_STREAM:
717 case ANY:
718 allownumeric = 1;
719 break;
720 default:
721 return EAI_SOCKTYPE;
722 }
723
724 if (android::base::ParseUint(servname, &port)) {
725 if (!allownumeric) return EAI_SERVICE;
726 if (port > 65535) return EAI_SERVICE;
727 port = htons(port);
728 } else {
729 if (ai->ai_flags & AI_NUMERICSERV) return EAI_NONAME;
730
731 switch (ai->ai_socktype) {
732 case SOCK_DGRAM:
733 proto = "udp";
734 break;
735 case SOCK_STREAM:
736 proto = "tcp";
737 break;
738 default:
739 proto = NULL;
740 break;
741 }
742
743 if ((sp = getservbyname(servname, proto)) == NULL) return EAI_SERVICE;
744 port = sp->s_port;
745 }
746
747 if (!matchonly) {
748 switch (ai->ai_family) {
749 case AF_INET:
750 ((struct sockaddr_in*) (void*) ai->ai_addr)->sin_port = port;
751 break;
752 case AF_INET6:
753 ((struct sockaddr_in6*) (void*) ai->ai_addr)->sin6_port = port;
754 break;
755 }
756 }
757
758 return 0;
759 }
760
find_afd(int af)761 static const struct afd* find_afd(int af) {
762 const struct afd* afd;
763
764 if (af == PF_UNSPEC) return NULL;
765 for (afd = afdl; afd->a_af; afd++) {
766 if (afd->a_af == af) return afd;
767 }
768 return NULL;
769 }
770
771 // Convert a string to a scope identifier.
ip6_str2scopeid(const char * scope,struct sockaddr_in6 * sin6,uint32_t * scopeid)772 static int ip6_str2scopeid(const char* scope, struct sockaddr_in6* sin6, uint32_t* scopeid) {
773 struct in6_addr* a6;
774
775 assert(scope != NULL);
776 assert(sin6 != NULL);
777 assert(scopeid != NULL);
778
779 a6 = &sin6->sin6_addr;
780
781 /* empty scopeid portion is invalid */
782 if (*scope == '\0') return -1;
783
784 if (IN6_IS_ADDR_LINKLOCAL(a6) || IN6_IS_ADDR_MC_LINKLOCAL(a6)) {
785 /*
786 * We currently assume a one-to-one mapping between links
787 * and interfaces, so we simply use interface indices for
788 * like-local scopes.
789 */
790 *scopeid = if_nametoindex(scope);
791 if (*scopeid != 0) return 0;
792 }
793
794 /* try to convert to a numeric id as a last resort*/
795 if (!android::base::ParseUint(scope, scopeid)) return -1;
796
797 return 0;
798 }
799
800 /* code duplicate with gethnamaddr.c */
801
802 #define BOUNDED_INCR(x) \
803 do { \
804 BOUNDS_CHECK(cp, x); \
805 cp += (x); \
806 } while (0)
807
808 #define BOUNDS_CHECK(ptr, count) \
809 do { \
810 if (eom - (ptr) < (count)) { \
811 *herrno = NO_RECOVERY; \
812 return NULL; \
813 } \
814 } while (0)
815
getanswer(const std::vector<uint8_t> & answer,int anslen,const char * qname,int qtype,const struct addrinfo * pai,int * herrno)816 static struct addrinfo* getanswer(const std::vector<uint8_t>& answer, int anslen, const char* qname,
817 int qtype, const struct addrinfo* pai, int* herrno) {
818 struct addrinfo sentinel = {};
819 struct addrinfo *cur;
820 struct addrinfo ai;
821 const struct afd* afd;
822 char* canonname;
823 const HEADER* hp;
824 const uint8_t* cp;
825 int n;
826 const uint8_t* eom;
827 char *bp, *ep;
828 int type, ancount, qdcount;
829 int haveanswer, had_error;
830 char tbuf[MAXDNAME];
831 char hostbuf[8 * 1024];
832
833 assert(qname != NULL);
834 assert(pai != NULL);
835
836 cur = &sentinel;
837
838 canonname = NULL;
839 eom = answer.data() + anslen;
840
841 bool (*name_ok)(const char* dn);
842 switch (qtype) {
843 case T_A:
844 case T_AAAA:
845 case T_ANY: /*use T_ANY only for T_A/T_AAAA lookup*/
846 name_ok = res_hnok;
847 break;
848 default:
849 return NULL; /* XXX should be abort(); */
850 }
851 /*
852 * find first satisfactory answer
853 */
854 hp = reinterpret_cast<const HEADER*>(answer.data());
855 ancount = ntohs(hp->ancount);
856 qdcount = ntohs(hp->qdcount);
857 bp = hostbuf;
858 ep = hostbuf + sizeof hostbuf;
859 cp = answer.data();
860 BOUNDED_INCR(HFIXEDSZ);
861 if (qdcount != 1) {
862 *herrno = NO_RECOVERY;
863 return (NULL);
864 }
865 n = dn_expand(answer.data(), eom, cp, bp, ep - bp);
866 if ((n < 0) || !(*name_ok)(bp)) {
867 *herrno = NO_RECOVERY;
868 return (NULL);
869 }
870 BOUNDED_INCR(n + QFIXEDSZ);
871 if (qtype == T_A || qtype == T_AAAA || qtype == T_ANY) {
872 /* res_send() has already verified that the query name is the
873 * same as the one we sent; this just gets the expanded name
874 * (i.e., with the succeeding search-domain tacked on).
875 */
876 n = strlen(bp) + 1; /* for the \0 */
877 if (n >= MAXHOSTNAMELEN) {
878 *herrno = NO_RECOVERY;
879 return (NULL);
880 }
881 canonname = bp;
882 bp += n;
883 /* The qname can be abbreviated, but h_name is now absolute. */
884 qname = canonname;
885 }
886 haveanswer = 0;
887 had_error = 0;
888 while (ancount-- > 0 && cp < eom && !had_error) {
889 n = dn_expand(answer.data(), eom, cp, bp, ep - bp);
890 if ((n < 0) || !(*name_ok)(bp)) {
891 had_error++;
892 continue;
893 }
894 cp += n; /* name */
895 BOUNDS_CHECK(cp, 3 * INT16SZ + INT32SZ);
896 type = ntohs(*reinterpret_cast<const uint16_t*>(cp));
897 cp += INT16SZ; /* type */
898 int cl = ntohs(*reinterpret_cast<const uint16_t*>(cp));
899 cp += INT16SZ + INT32SZ; /* class, TTL */
900 n = ntohs(*reinterpret_cast<const uint16_t*>(cp));
901 cp += INT16SZ; /* len */
902 BOUNDS_CHECK(cp, n);
903 if (cl != C_IN) {
904 /* XXX - debug? syslog? */
905 cp += n;
906 continue; /* XXX - had_error++ ? */
907 }
908 if ((qtype == T_A || qtype == T_AAAA || qtype == T_ANY) && type == T_CNAME) {
909 n = dn_expand(answer.data(), eom, cp, tbuf, sizeof tbuf);
910 if ((n < 0) || !(*name_ok)(tbuf)) {
911 had_error++;
912 continue;
913 }
914 cp += n;
915 /* Get canonical name. */
916 n = strlen(tbuf) + 1; /* for the \0 */
917 if (n > ep - bp || n >= MAXHOSTNAMELEN) {
918 had_error++;
919 continue;
920 }
921 strlcpy(bp, tbuf, (size_t)(ep - bp));
922 canonname = bp;
923 bp += n;
924 continue;
925 }
926 if (qtype == T_ANY) {
927 if (!(type == T_A || type == T_AAAA)) {
928 cp += n;
929 continue;
930 }
931 } else if (type != qtype) {
932 if (type != T_KEY && type != T_SIG)
933 LOG(DEBUG) << __func__ << ": asked for \"" << qname << " " << p_class(C_IN) << " "
934 << p_type(qtype) << "\", got type \"" << p_type(type) << "\"";
935 cp += n;
936 continue; /* XXX - had_error++ ? */
937 }
938 switch (type) {
939 case T_A:
940 case T_AAAA:
941 if (strcasecmp(canonname, bp) != 0) {
942 LOG(DEBUG) << __func__ << ": asked for \"" << canonname << "\", got \"" << bp
943 << "\"";
944 cp += n;
945 continue; /* XXX - had_error++ ? */
946 }
947 if (type == T_A && n != INADDRSZ) {
948 cp += n;
949 continue;
950 }
951 if (type == T_AAAA && n != IN6ADDRSZ) {
952 cp += n;
953 continue;
954 }
955 if (type == T_AAAA) {
956 struct in6_addr in6;
957 memcpy(&in6, cp, IN6ADDRSZ);
958 if (IN6_IS_ADDR_V4MAPPED(&in6)) {
959 cp += n;
960 continue;
961 }
962 }
963 if (!haveanswer) {
964 int nn;
965
966 canonname = bp;
967 nn = strlen(bp) + 1; /* for the \0 */
968 bp += nn;
969 }
970
971 /* don't overwrite pai */
972 ai = *pai;
973 ai.ai_family = (type == T_A) ? AF_INET : AF_INET6;
974 afd = find_afd(ai.ai_family);
975 if (afd == NULL) {
976 cp += n;
977 continue;
978 }
979 cur->ai_next = get_ai(&ai, afd, (const char*) cp);
980 if (cur->ai_next == NULL) had_error++;
981 while (cur && cur->ai_next) cur = cur->ai_next;
982 cp += n;
983 break;
984 default:
985 abort();
986 }
987 if (!had_error) haveanswer++;
988 }
989 if (haveanswer) {
990 if (!canonname)
991 (void) get_canonname(pai, sentinel.ai_next, qname);
992 else
993 (void) get_canonname(pai, sentinel.ai_next, canonname);
994 *herrno = NETDB_SUCCESS;
995 return sentinel.ai_next;
996 }
997
998 *herrno = NO_RECOVERY;
999 return NULL;
1000 }
1001
1002 struct addrinfo_sort_elem {
1003 struct addrinfo* ai;
1004 int has_src_addr;
1005 sockaddr_union src_addr;
1006 int original_order;
1007 };
1008
_get_scope(const struct sockaddr * addr)1009 static int _get_scope(const struct sockaddr* addr) {
1010 if (addr->sa_family == AF_INET6) {
1011 const struct sockaddr_in6* addr6 = (const struct sockaddr_in6*) addr;
1012 if (IN6_IS_ADDR_MULTICAST(&addr6->sin6_addr)) {
1013 return IPV6_ADDR_MC_SCOPE(&addr6->sin6_addr);
1014 } else if (IN6_IS_ADDR_LOOPBACK(&addr6->sin6_addr) ||
1015 IN6_IS_ADDR_LINKLOCAL(&addr6->sin6_addr)) {
1016 /*
1017 * RFC 4291 section 2.5.3 says loopback is to be treated as having
1018 * link-local scope.
1019 */
1020 return IPV6_ADDR_SCOPE_LINKLOCAL;
1021 } else if (IN6_IS_ADDR_SITELOCAL(&addr6->sin6_addr)) {
1022 return IPV6_ADDR_SCOPE_SITELOCAL;
1023 } else {
1024 return IPV6_ADDR_SCOPE_GLOBAL;
1025 }
1026 } else if (addr->sa_family == AF_INET) {
1027 const struct sockaddr_in* addr4 = (const struct sockaddr_in*) addr;
1028 unsigned long int na = ntohl(addr4->sin_addr.s_addr);
1029
1030 if (IN_LOOPBACK(na) || /* 127.0.0.0/8 */
1031 (na & 0xffff0000) == 0xa9fe0000) { /* 169.254.0.0/16 */
1032 return IPV6_ADDR_SCOPE_LINKLOCAL;
1033 } else {
1034 /*
1035 * RFC 6724 section 3.2. Other IPv4 addresses, including private addresses
1036 * and shared addresses (100.64.0.0/10), are assigned global scope.
1037 */
1038 return IPV6_ADDR_SCOPE_GLOBAL;
1039 }
1040 } else {
1041 /*
1042 * This should never happen.
1043 * Return a scope with low priority as a last resort.
1044 */
1045 return IPV6_ADDR_SCOPE_NODELOCAL;
1046 }
1047 }
1048
1049 /* These macros are modelled after the ones in <netinet/in6.h>. */
1050
1051 /* RFC 4380, section 2.6 */
1052 #define IN6_IS_ADDR_TEREDO(a) \
1053 ((*(const uint32_t*) (const void*) (&(a)->s6_addr[0]) == ntohl(0x20010000)))
1054
1055 /* RFC 3056, section 2. */
1056 #define IN6_IS_ADDR_6TO4(a) (((a)->s6_addr[0] == 0x20) && ((a)->s6_addr[1] == 0x02))
1057
1058 /* 6bone testing address area (3ffe::/16), deprecated in RFC 3701. */
1059 #define IN6_IS_ADDR_6BONE(a) (((a)->s6_addr[0] == 0x3f) && ((a)->s6_addr[1] == 0xfe))
1060
1061 /*
1062 * Get the label for a given IPv4/IPv6 address.
1063 * RFC 6724, section 2.1.
1064 */
1065
_get_label(const struct sockaddr * addr)1066 static int _get_label(const struct sockaddr* addr) {
1067 if (addr->sa_family == AF_INET) {
1068 return 4;
1069 } else if (addr->sa_family == AF_INET6) {
1070 const struct sockaddr_in6* addr6 = (const struct sockaddr_in6*) addr;
1071 if (IN6_IS_ADDR_LOOPBACK(&addr6->sin6_addr)) {
1072 return 0;
1073 } else if (IN6_IS_ADDR_V4MAPPED(&addr6->sin6_addr)) {
1074 return 4;
1075 } else if (IN6_IS_ADDR_6TO4(&addr6->sin6_addr)) {
1076 return 2;
1077 } else if (IN6_IS_ADDR_TEREDO(&addr6->sin6_addr)) {
1078 return 5;
1079 } else if (IN6_IS_ADDR_ULA(&addr6->sin6_addr)) {
1080 return 13;
1081 } else if (IN6_IS_ADDR_V4COMPAT(&addr6->sin6_addr)) {
1082 return 3;
1083 } else if (IN6_IS_ADDR_SITELOCAL(&addr6->sin6_addr)) {
1084 return 11;
1085 } else if (IN6_IS_ADDR_6BONE(&addr6->sin6_addr)) {
1086 return 12;
1087 } else {
1088 /* All other IPv6 addresses, including global unicast addresses. */
1089 return 1;
1090 }
1091 } else {
1092 /*
1093 * This should never happen.
1094 * Return a semi-random label as a last resort.
1095 */
1096 return 1;
1097 }
1098 }
1099
1100 /*
1101 * Get the precedence for a given IPv4/IPv6 address.
1102 * RFC 6724, section 2.1.
1103 */
1104
_get_precedence(const struct sockaddr * addr)1105 static int _get_precedence(const struct sockaddr* addr) {
1106 if (addr->sa_family == AF_INET) {
1107 return 35;
1108 } else if (addr->sa_family == AF_INET6) {
1109 const struct sockaddr_in6* addr6 = (const struct sockaddr_in6*) addr;
1110 if (IN6_IS_ADDR_LOOPBACK(&addr6->sin6_addr)) {
1111 return 50;
1112 } else if (IN6_IS_ADDR_V4MAPPED(&addr6->sin6_addr)) {
1113 return 35;
1114 } else if (IN6_IS_ADDR_6TO4(&addr6->sin6_addr)) {
1115 return 30;
1116 } else if (IN6_IS_ADDR_TEREDO(&addr6->sin6_addr)) {
1117 return 5;
1118 } else if (IN6_IS_ADDR_ULA(&addr6->sin6_addr)) {
1119 return 3;
1120 } else if (IN6_IS_ADDR_V4COMPAT(&addr6->sin6_addr) ||
1121 IN6_IS_ADDR_SITELOCAL(&addr6->sin6_addr) ||
1122 IN6_IS_ADDR_6BONE(&addr6->sin6_addr)) {
1123 return 1;
1124 } else {
1125 /* All other IPv6 addresses, including global unicast addresses. */
1126 return 40;
1127 }
1128 } else {
1129 return 1;
1130 }
1131 }
1132
1133 /*
1134 * Find number of matching initial bits between the two addresses a1 and a2.
1135 */
1136
_common_prefix_len(const struct in6_addr * a1,const struct in6_addr * a2)1137 static int _common_prefix_len(const struct in6_addr* a1, const struct in6_addr* a2) {
1138 const char* p1 = (const char*) a1;
1139 const char* p2 = (const char*) a2;
1140 unsigned i;
1141
1142 for (i = 0; i < sizeof(*a1); ++i) {
1143 int x, j;
1144
1145 if (p1[i] == p2[i]) {
1146 continue;
1147 }
1148 x = p1[i] ^ p2[i];
1149 for (j = 0; j < CHAR_BIT; ++j) {
1150 if (x & (1 << (CHAR_BIT - 1))) {
1151 return i * CHAR_BIT + j;
1152 }
1153 x <<= 1;
1154 }
1155 }
1156 return sizeof(*a1) * CHAR_BIT;
1157 }
1158
1159 /*
1160 * Compare two source/destination address pairs.
1161 * RFC 6724, section 6.
1162 */
1163
_rfc6724_compare(const void * ptr1,const void * ptr2)1164 static int _rfc6724_compare(const void* ptr1, const void* ptr2) {
1165 const struct addrinfo_sort_elem* a1 = (const struct addrinfo_sort_elem*) ptr1;
1166 const struct addrinfo_sort_elem* a2 = (const struct addrinfo_sort_elem*) ptr2;
1167 int scope_src1, scope_dst1, scope_match1;
1168 int scope_src2, scope_dst2, scope_match2;
1169 int label_src1, label_dst1, label_match1;
1170 int label_src2, label_dst2, label_match2;
1171 int precedence1, precedence2;
1172 int prefixlen1, prefixlen2;
1173
1174 /* Rule 1: Avoid unusable destinations. */
1175 if (a1->has_src_addr != a2->has_src_addr) {
1176 return a2->has_src_addr - a1->has_src_addr;
1177 }
1178
1179 /* Rule 2: Prefer matching scope. */
1180 scope_src1 = _get_scope(&a1->src_addr.sa);
1181 scope_dst1 = _get_scope(a1->ai->ai_addr);
1182 scope_match1 = (scope_src1 == scope_dst1);
1183
1184 scope_src2 = _get_scope(&a2->src_addr.sa);
1185 scope_dst2 = _get_scope(a2->ai->ai_addr);
1186 scope_match2 = (scope_src2 == scope_dst2);
1187
1188 if (scope_match1 != scope_match2) {
1189 return scope_match2 - scope_match1;
1190 }
1191
1192 /*
1193 * Rule 3: Avoid deprecated addresses.
1194 * TODO(sesse): We don't currently have a good way of finding this.
1195 */
1196
1197 /*
1198 * Rule 4: Prefer home addresses.
1199 * TODO(sesse): We don't currently have a good way of finding this.
1200 */
1201
1202 /* Rule 5: Prefer matching label. */
1203 label_src1 = _get_label(&a1->src_addr.sa);
1204 label_dst1 = _get_label(a1->ai->ai_addr);
1205 label_match1 = (label_src1 == label_dst1);
1206
1207 label_src2 = _get_label(&a2->src_addr.sa);
1208 label_dst2 = _get_label(a2->ai->ai_addr);
1209 label_match2 = (label_src2 == label_dst2);
1210
1211 if (label_match1 != label_match2) {
1212 return label_match2 - label_match1;
1213 }
1214
1215 /* Rule 6: Prefer higher precedence. */
1216 precedence1 = _get_precedence(a1->ai->ai_addr);
1217 precedence2 = _get_precedence(a2->ai->ai_addr);
1218 if (precedence1 != precedence2) {
1219 return precedence2 - precedence1;
1220 }
1221
1222 /*
1223 * Rule 7: Prefer native transport.
1224 * TODO(sesse): We don't currently have a good way of finding this.
1225 */
1226
1227 /* Rule 8: Prefer smaller scope. */
1228 if (scope_dst1 != scope_dst2) {
1229 return scope_dst1 - scope_dst2;
1230 }
1231
1232 /*
1233 * Rule 9: Use longest matching prefix.
1234 * We implement this for IPv6 only, as the rules in RFC 6724 don't seem
1235 * to work very well directly applied to IPv4. (glibc uses information from
1236 * the routing table for a custom IPv4 implementation here.)
1237 */
1238 if (a1->has_src_addr && a1->ai->ai_addr->sa_family == AF_INET6 && a2->has_src_addr &&
1239 a2->ai->ai_addr->sa_family == AF_INET6) {
1240 const struct sockaddr_in6* a1_src = &a1->src_addr.sin6;
1241 const struct sockaddr_in6* a1_dst = (const struct sockaddr_in6*) a1->ai->ai_addr;
1242 const struct sockaddr_in6* a2_src = &a2->src_addr.sin6;
1243 const struct sockaddr_in6* a2_dst = (const struct sockaddr_in6*) a2->ai->ai_addr;
1244 prefixlen1 = _common_prefix_len(&a1_src->sin6_addr, &a1_dst->sin6_addr);
1245 prefixlen2 = _common_prefix_len(&a2_src->sin6_addr, &a2_dst->sin6_addr);
1246 if (prefixlen1 != prefixlen2) {
1247 return prefixlen2 - prefixlen1;
1248 }
1249 }
1250
1251 /*
1252 * Rule 10: Leave the order unchanged.
1253 * We need this since qsort() is not necessarily stable.
1254 */
1255 return a1->original_order - a2->original_order;
1256 }
1257
1258 /*
1259 * Find the source address that will be used if trying to connect to the given
1260 * address. src_addr must be assigned and large enough to hold a struct sockaddr_in6.
1261 * allow_v6_linklocal controls whether to accept link-local source addresses.
1262 *
1263 * Returns 1 if a source address was found, 0 if the address is unreachable,
1264 * and -1 if a fatal error occurred. If 0 or -1, the contents of src_addr are
1265 * undefined.
1266 */
1267
_find_src_addr(const struct sockaddr * addr,struct sockaddr * src_addr,unsigned mark,uid_t uid,bool allow_v6_linklocal)1268 static int _find_src_addr(const struct sockaddr* addr, struct sockaddr* src_addr, unsigned mark,
1269 uid_t uid, bool allow_v6_linklocal) {
1270 if (src_addr == nullptr) return -1;
1271
1272 int ret;
1273 socklen_t len;
1274
1275 switch (addr->sa_family) {
1276 case AF_INET:
1277 len = sizeof(struct sockaddr_in);
1278 break;
1279 case AF_INET6:
1280 len = sizeof(struct sockaddr_in6);
1281 break;
1282 default:
1283 /* No known usable source address for non-INET families. */
1284 return 0;
1285 }
1286
1287 android::base::unique_fd sock(socket(addr->sa_family, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP));
1288 if (sock.get() == -1) {
1289 if (errno == EAFNOSUPPORT) {
1290 return 0;
1291 } else {
1292 return -1;
1293 }
1294 }
1295 if (mark != MARK_UNSET && setsockopt(sock, SOL_SOCKET, SO_MARK, &mark, sizeof(mark)) < 0) {
1296 return 0;
1297 }
1298 if (uid > 0 && uid != NET_CONTEXT_INVALID_UID && fchown(sock, uid, (gid_t) -1) < 0) {
1299 return 0;
1300 }
1301 do {
1302 ret = connect(sock, addr, len);
1303 } while (ret == -1 && errno == EINTR);
1304
1305 if (ret == -1) {
1306 return 0;
1307 }
1308
1309 if (getsockname(sock, src_addr, &len) == -1) {
1310 return -1;
1311 }
1312
1313 if (src_addr->sa_family == AF_INET6) {
1314 sockaddr_in6* sin6 = reinterpret_cast<sockaddr_in6*>(src_addr);
1315 if (!allow_v6_linklocal && IN6_IS_ADDR_LINKLOCAL(&sin6->sin6_addr)) {
1316 // There is no point in sending an AAAA query because the device does not have a global
1317 // IP address. The only thing that can be affected is the hostname "localhost". Devices
1318 // with this setting will not be able to get the localhost v6 IP address ::1 via DNS
1319 // lookups, which is accessible by host local. But it is expected that a DNS server that
1320 // replies to "localhost" in AAAA should also reply in A. So it shouldn't cause issues.
1321 // Also, the current behavior will not be changed because hostname “localhost” only gets
1322 // 127.0.0.1 per etc/hosts configs.
1323 return 0;
1324 }
1325 }
1326
1327 return 1;
1328 }
1329
1330 /*
1331 * Sort the linked list starting at sentinel->ai_next in RFC6724 order.
1332 * Will leave the list unchanged if an error occurs.
1333 */
1334
resolv_rfc6724_sort(struct addrinfo * list_sentinel,unsigned mark,uid_t uid)1335 void resolv_rfc6724_sort(struct addrinfo* list_sentinel, unsigned mark, uid_t uid) {
1336 if (list_sentinel == nullptr) return;
1337
1338 struct addrinfo* cur;
1339 int nelem = 0, i;
1340 struct addrinfo_sort_elem* elems;
1341
1342 cur = list_sentinel->ai_next;
1343 while (cur) {
1344 ++nelem;
1345 cur = cur->ai_next;
1346 }
1347
1348 elems = (struct addrinfo_sort_elem*) calloc(nelem, sizeof(struct addrinfo_sort_elem));
1349 if (elems == NULL) {
1350 goto error;
1351 }
1352
1353 /*
1354 * Convert the linked list to an array that also contains the candidate
1355 * source address for each destination address.
1356 */
1357 for (i = 0, cur = list_sentinel->ai_next; i < nelem; ++i, cur = cur->ai_next) {
1358 int has_src_addr;
1359 assert(cur != NULL);
1360 elems[i].ai = cur;
1361 elems[i].original_order = i;
1362
1363 has_src_addr = _find_src_addr(cur->ai_addr, &elems[i].src_addr.sa, mark, uid,
1364 /*allow_v6_linklocal=*/true);
1365 if (has_src_addr == -1) {
1366 goto error;
1367 }
1368 elems[i].has_src_addr = has_src_addr;
1369 }
1370
1371 /* Sort the addresses, and rearrange the linked list so it matches the sorted order. */
1372 qsort((void*) elems, nelem, sizeof(struct addrinfo_sort_elem), _rfc6724_compare);
1373
1374 list_sentinel->ai_next = elems[0].ai;
1375 for (i = 0; i < nelem - 1; ++i) {
1376 elems[i].ai->ai_next = elems[i + 1].ai;
1377 }
1378 elems[nelem - 1].ai->ai_next = NULL;
1379
1380 error:
1381 free(elems);
1382 }
1383
dns_getaddrinfo(const char * name,const addrinfo * pai,const android_net_context * netcontext,addrinfo ** rv,NetworkDnsEventReported * event)1384 static int dns_getaddrinfo(const char* name, const addrinfo* pai,
1385 const android_net_context* netcontext, addrinfo** rv,
1386 NetworkDnsEventReported* event) {
1387 res_target q = {};
1388 res_target q2 = {};
1389 ResState res(netcontext, event);
1390 setMdnsFlag(name, res.netid, &(res.flags));
1391
1392 switch (pai->ai_family) {
1393 case AF_UNSPEC: {
1394 /* prefer IPv6 */
1395 q.name = name;
1396 q.qclass = C_IN;
1397 int query_ipv6 = 1, query_ipv4 = 1;
1398 if (pai->ai_flags & AI_ADDRCONFIG) {
1399 query_ipv6 = have_ipv6(netcontext->app_mark, netcontext->uid,
1400 isMdnsResolution(res.flags));
1401 query_ipv4 = have_ipv4(netcontext->app_mark, netcontext->uid);
1402 }
1403 if (query_ipv6) {
1404 q.qtype = T_AAAA;
1405 if (query_ipv4) {
1406 q.next = &q2;
1407 q2.name = name;
1408 q2.qclass = C_IN;
1409 q2.qtype = T_A;
1410 }
1411 } else if (query_ipv4) {
1412 q.qtype = T_A;
1413 } else {
1414 return EAI_NODATA;
1415 }
1416 break;
1417 }
1418 case AF_INET:
1419 q.name = name;
1420 q.qclass = C_IN;
1421 q.qtype = T_A;
1422 break;
1423 case AF_INET6:
1424 q.name = name;
1425 q.qclass = C_IN;
1426 q.qtype = T_AAAA;
1427 break;
1428 default:
1429 return EAI_FAMILY;
1430 }
1431
1432 int he;
1433 if (res_searchN(name, &q, &res, &he) < 0) {
1434 // Return h_errno (he) to catch more detailed errors rather than EAI_NODATA.
1435 // Note that res_searchN() doesn't set the pair NETDB_INTERNAL and errno.
1436 // See also herrnoToAiErrno().
1437 return herrnoToAiErrno(he);
1438 }
1439
1440 addrinfo sentinel = {};
1441 addrinfo* cur = &sentinel;
1442 addrinfo* ai = getanswer(q.answer, q.n, q.name, q.qtype, pai, &he);
1443 if (ai) {
1444 cur->ai_next = ai;
1445 while (cur && cur->ai_next) cur = cur->ai_next;
1446 }
1447 if (q.next) {
1448 ai = getanswer(q2.answer, q2.n, q2.name, q2.qtype, pai, &he);
1449 if (ai) cur->ai_next = ai;
1450 }
1451 if (sentinel.ai_next == NULL) {
1452 // Note that getanswer() doesn't set the pair NETDB_INTERNAL and errno.
1453 // See also herrnoToAiErrno().
1454 return herrnoToAiErrno(he);
1455 }
1456
1457 resolv_rfc6724_sort(&sentinel, netcontext->app_mark, netcontext->uid);
1458
1459 *rv = sentinel.ai_next;
1460 return 0;
1461 }
1462
_sethtent(FILE ** hostf)1463 static void _sethtent(FILE** hostf) {
1464 if (!*hostf)
1465 *hostf = fopen(_PATH_HOSTS, "re");
1466 else
1467 rewind(*hostf);
1468 }
1469
_endhtent(FILE ** hostf)1470 static void _endhtent(FILE** hostf) {
1471 if (*hostf) {
1472 (void) fclose(*hostf);
1473 *hostf = NULL;
1474 }
1475 }
1476
_gethtent(FILE ** hostf,const char * name,const struct addrinfo * pai)1477 static struct addrinfo* _gethtent(FILE** hostf, const char* name, const struct addrinfo* pai) {
1478 char* p;
1479 char *cp, *tname, *cname;
1480 struct addrinfo *res0, *res;
1481 int error;
1482 const char* addr;
1483 char hostbuf[8 * 1024];
1484
1485 assert(name != NULL);
1486 assert(pai != NULL);
1487
1488 if (!*hostf && !(*hostf = fopen(_PATH_HOSTS, "re"))) return (NULL);
1489 again:
1490 if (!(p = fgets(hostbuf, sizeof hostbuf, *hostf))) return (NULL);
1491 if (*p == '#') goto again;
1492 if (!(cp = strpbrk(p, "#\n"))) goto again;
1493 *cp = '\0';
1494 if (!(cp = strpbrk(p, " \t"))) goto again;
1495 *cp++ = '\0';
1496 addr = p;
1497 /* if this is not something we're looking for, skip it. */
1498 cname = NULL;
1499 while (cp && *cp) {
1500 if (*cp == ' ' || *cp == '\t') {
1501 cp++;
1502 continue;
1503 }
1504 if (!cname) cname = cp;
1505 tname = cp;
1506 if ((cp = strpbrk(cp, " \t")) != NULL) *cp++ = '\0';
1507 if (strcasecmp(name, tname) == 0) goto found;
1508 }
1509 goto again;
1510
1511 found:
1512 error = getaddrinfo_numeric(addr, nullptr, *pai, &res0);
1513 if (error) goto again;
1514 for (res = res0; res; res = res->ai_next) {
1515 /* cover it up */
1516 res->ai_flags = pai->ai_flags;
1517
1518 if (pai->ai_flags & AI_CANONNAME) {
1519 if (get_canonname(pai, res, cname) != 0) {
1520 freeaddrinfo(res0);
1521 goto again;
1522 }
1523 }
1524 }
1525 return res0;
1526 }
1527
getCustomHosts(const size_t netid,const char * _Nonnull name,const struct addrinfo * _Nonnull pai)1528 static struct addrinfo* getCustomHosts(const size_t netid, const char* _Nonnull name,
1529 const struct addrinfo* _Nonnull pai) {
1530 struct addrinfo sentinel = {};
1531 struct addrinfo *res0, *res;
1532 res = &sentinel;
1533 std::vector<std::string> hosts = getCustomizedTableByName(netid, name);
1534 for (const std::string& host : hosts) {
1535 int error = getaddrinfo_numeric(host.c_str(), nullptr, *pai, &res0);
1536 if (!error && res0 != nullptr) {
1537 res->ai_next = res0;
1538 res = res0;
1539 res0 = nullptr;
1540 }
1541 }
1542 return sentinel.ai_next;
1543 }
1544
files_getaddrinfo(const size_t netid,const char * name,const addrinfo * pai,addrinfo ** res)1545 static bool files_getaddrinfo(const size_t netid, const char* name, const addrinfo* pai,
1546 addrinfo** res) {
1547 struct addrinfo sentinel = {};
1548 struct addrinfo *p, *cur;
1549 FILE* hostf = nullptr;
1550
1551 cur = &sentinel;
1552 _sethtent(&hostf);
1553 while ((p = _gethtent(&hostf, name, pai)) != nullptr) {
1554 cur->ai_next = p;
1555 while (cur && cur->ai_next) cur = cur->ai_next;
1556 }
1557 _endhtent(&hostf);
1558
1559 if ((p = getCustomHosts(netid, name, pai)) != nullptr) {
1560 cur->ai_next = p;
1561 }
1562
1563 *res = sentinel.ai_next;
1564 return sentinel.ai_next != nullptr;
1565 }
1566
1567 /* resolver logic */
1568
1569 namespace {
1570
1571 constexpr int SLEEP_TIME_MS = 2;
1572
getHerrnoFromRcode(int rcode)1573 int getHerrnoFromRcode(int rcode) {
1574 switch (rcode) {
1575 // Not defined in RFC.
1576 case RCODE_TIMEOUT:
1577 // DNS metrics monitors DNS query timeout.
1578 return NETD_RESOLV_H_ERRNO_EXT_TIMEOUT; // extended h_errno.
1579 // Defined in RFC 1035 section 4.1.1.
1580 case NXDOMAIN:
1581 return HOST_NOT_FOUND;
1582 case SERVFAIL:
1583 return TRY_AGAIN;
1584 case NOERROR:
1585 return NO_DATA;
1586 case FORMERR:
1587 case NOTIMP:
1588 case REFUSED:
1589 default:
1590 return NO_RECOVERY;
1591 }
1592 }
1593
1594 struct QueryResult {
1595 int ancount;
1596 int rcode;
1597 int herrno;
1598 int qerrno;
1599 NetworkDnsEventReported event;
1600 };
1601
1602 // Formulate a normal query, send, and await answer.
1603 // Caller must parse answer and determine whether it answers the question.
doQuery(const char * name,res_target * t,ResState * res,std::chrono::milliseconds sleepTimeMs)1604 QueryResult doQuery(const char* name, res_target* t, ResState* res,
1605 std::chrono::milliseconds sleepTimeMs) {
1606 HEADER* hp = (HEADER*)(void*)t->answer.data();
1607
1608 hp->rcode = NOERROR; // default
1609
1610 const int cl = t->qclass;
1611 const int type = t->qtype;
1612 const int anslen = t->answer.size();
1613
1614 LOG(DEBUG) << __func__ << ": (" << cl << ", " << type << ")";
1615
1616 uint8_t buf[MAXPACKET];
1617 int n = res_nmkquery(QUERY, name, cl, type, {}, buf, res->netcontext_flags);
1618
1619 if (n > 0 &&
1620 (res->netcontext_flags & (NET_CONTEXT_FLAG_USE_DNS_OVER_TLS | NET_CONTEXT_FLAG_USE_EDNS))) {
1621 n = res_nopt(res, n, buf, anslen);
1622 }
1623
1624 NetworkDnsEventReported event;
1625 if (n <= 0) {
1626 LOG(ERROR) << __func__ << ": res_nmkquery failed";
1627 return {
1628 .ancount = 0,
1629 .rcode = -1,
1630 .herrno = NO_RECOVERY,
1631 .qerrno = errno,
1632 .event = event,
1633 };
1634 }
1635
1636 ResState res_temp = res->clone(&event);
1637
1638 int rcode = NOERROR;
1639 n = res_nsend(&res_temp, std::span(buf, n), std::span(t->answer.data(), anslen), &rcode, 0,
1640 sleepTimeMs);
1641 if (n < 0 || hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
1642 if (rcode != RCODE_TIMEOUT) rcode = hp->rcode;
1643 // if the query choked with EDNS0, retry without EDNS0
1644 if ((res_temp.netcontext_flags &
1645 (NET_CONTEXT_FLAG_USE_DNS_OVER_TLS | NET_CONTEXT_FLAG_USE_EDNS)) &&
1646 (res_temp.flags & RES_F_EDNS0ERR)) {
1647 LOG(INFO) << __func__ << ": retry without EDNS0";
1648 n = res_nmkquery(QUERY, name, cl, type, {}, buf, res_temp.netcontext_flags);
1649 n = res_nsend(&res_temp, std::span(buf, n), std::span(t->answer.data(), anslen), &rcode,
1650 0);
1651 }
1652 }
1653
1654 LOG(INFO) << __func__ << ": rcode=" << rcode << ", ancount=" << ntohs(hp->ancount)
1655 << ", return value=" << n;
1656
1657 t->n = n;
1658 return {
1659 .ancount = ntohs(hp->ancount),
1660 .rcode = rcode,
1661 .qerrno = errno,
1662 .event = event,
1663 };
1664 }
1665
1666 } // namespace
1667
1668 // This function runs doQuery() for each res_target in parallel.
1669 // The `target`, which is set in dns_getaddrinfo(), contains at most two res_target.
res_queryN_parallel(const char * name,res_target * target,ResState * res,int * herrno)1670 static int res_queryN_parallel(const char* name, res_target* target, ResState* res, int* herrno) {
1671 std::vector<std::future<QueryResult>> results;
1672 results.reserve(2);
1673 std::chrono::milliseconds sleepTimeMs{};
1674 for (res_target* t = target; t; t = t->next) {
1675 results.emplace_back(std::async(std::launch::async, doQuery, name, t, res, sleepTimeMs));
1676 // Avoiding gateways drop packets if queries are sent too close together
1677 // Only needed if we have multiple queries in a row.
1678 if (t->next) {
1679 int sleepFlag = Experiments::getInstance()->getFlag("parallel_lookup_sleep_time",
1680 SLEEP_TIME_MS);
1681 if (sleepFlag > 1000) sleepFlag = 1000;
1682 sleepTimeMs = std::chrono::milliseconds(sleepFlag);
1683 }
1684 }
1685
1686 int ancount = 0;
1687 int rcode = 0;
1688
1689 for (auto& f : results) {
1690 const QueryResult& r = f.get();
1691 if (r.herrno == NO_RECOVERY) {
1692 *herrno = r.herrno;
1693 return -1;
1694 }
1695 res->event->MergeFrom(r.event);
1696 ancount += r.ancount;
1697 rcode = r.rcode;
1698 errno = r.qerrno;
1699 }
1700
1701 if (ancount == 0) {
1702 *herrno = getHerrnoFromRcode(rcode);
1703 return -1;
1704 }
1705
1706 return ancount;
1707 }
1708
1709 /*
1710 * Formulate a normal query, send, and retrieve answer in supplied buffer.
1711 * Return the size of the response on success, -1 on error.
1712 * If enabled, implement search rules until answer or unrecoverable failure
1713 * is detected. Error code, if any, is left in *herrno.
1714 */
res_searchN(const char * name,res_target * target,ResState * res,int * herrno)1715 static int res_searchN(const char* name, res_target* target, ResState* res, int* herrno) {
1716 const char* cp;
1717 HEADER* hp;
1718 uint32_t dots;
1719 int ret, saved_herrno;
1720 int got_nodata = 0, got_servfail = 0, tried_as_is = 0;
1721
1722 assert(name != NULL);
1723 assert(target != NULL);
1724
1725 hp = (HEADER*)(void*)target->answer.data();
1726
1727 errno = 0;
1728 *herrno = HOST_NOT_FOUND; /* default, if we never query */
1729 dots = 0;
1730 for (cp = name; *cp; cp++) dots += (*cp == '.');
1731 const bool trailing_dot = (cp > name && *--cp == '.') ? true : false;
1732
1733 /*
1734 * If there are dots in the name already, let's just give it a try
1735 * 'as is'. The threshold can be set with the "ndots" option.
1736 */
1737 saved_herrno = -1;
1738 if (dots >= res->ndots) {
1739 ret = res_querydomainN(name, NULL, target, res, herrno);
1740 if (ret > 0) return (ret);
1741 saved_herrno = *herrno;
1742 tried_as_is++;
1743 }
1744
1745 /*
1746 * We do at least one level of search if
1747 * - there is no dot, or
1748 * - there is at least one dot and there is no trailing dot.
1749 * - this is not a .local mDNS lookup.
1750 */
1751 if ((!dots || (dots && !trailing_dot)) && !isMdnsResolution(res->flags)) {
1752 /* Unfortunately we need to set stuff up before
1753 * the domain stuff is tried. Will have a better
1754 * fix after thread pools are used.
1755 */
1756 resolv_populate_res_for_net(res);
1757
1758 for (const auto& domain : res->search_domains) {
1759 ret = res_querydomainN(name, domain.c_str(), target, res, herrno);
1760 if (ret > 0) return ret;
1761
1762 /*
1763 * If no server present, give up.
1764 * If name isn't found in this domain,
1765 * keep trying higher domains in the search list
1766 * (if that's enabled).
1767 * On a NO_DATA error, keep trying, otherwise
1768 * a wildcard entry of another type could keep us
1769 * from finding this entry higher in the domain.
1770 * If we get some other error (negative answer or
1771 * server failure), then stop searching up,
1772 * but try the input name below in case it's
1773 * fully-qualified.
1774 */
1775 if (errno == ECONNREFUSED) {
1776 *herrno = TRY_AGAIN;
1777 return -1;
1778 }
1779
1780 switch (*herrno) {
1781 case NO_DATA:
1782 got_nodata++;
1783 [[fallthrough]];
1784 case HOST_NOT_FOUND:
1785 /* keep trying */
1786 break;
1787 case TRY_AGAIN:
1788 if (hp->rcode == SERVFAIL) {
1789 /* try next search element, if any */
1790 got_servfail++;
1791 }
1792 break;
1793 }
1794 }
1795 }
1796
1797 /*
1798 * if we have not already tried the name "as is", do that now.
1799 * note that we do this regardless of how many dots were in the
1800 * name or whether it ends with a dot.
1801 */
1802 if (!tried_as_is) {
1803 ret = res_querydomainN(name, NULL, target, res, herrno);
1804 if (ret > 0) return ret;
1805 }
1806
1807 /*
1808 * if we got here, we didn't satisfy the search.
1809 * if we did an initial full query, return that query's h_errno
1810 * (note that we wouldn't be here if that query had succeeded).
1811 * else if we ever got a nodata, send that back as the reason.
1812 * else send back meaningless h_errno, that being the one from
1813 * the last DNSRCH we did.
1814 */
1815 if (saved_herrno != -1)
1816 *herrno = saved_herrno;
1817 else if (got_nodata)
1818 *herrno = NO_DATA;
1819 else if (got_servfail)
1820 *herrno = TRY_AGAIN;
1821 return -1;
1822 }
1823
1824 // Perform a call on res_query on the concatenation of name and domain,
1825 // removing a trailing dot from name if domain is NULL.
res_querydomainN(const char * name,const char * domain,res_target * target,ResState * res,int * herrno)1826 static int res_querydomainN(const char* name, const char* domain, res_target* target, ResState* res,
1827 int* herrno) {
1828 char nbuf[MAXDNAME];
1829 const char* longname = nbuf;
1830 size_t n, d;
1831
1832 assert(name != NULL);
1833
1834 if (domain == NULL) {
1835 // Check for trailing '.'; copy without '.' if present.
1836 n = strlen(name);
1837 if (n + 1 > sizeof(nbuf)) {
1838 *herrno = NO_RECOVERY;
1839 return -1;
1840 }
1841 if (n > 0 && name[--n] == '.') {
1842 strncpy(nbuf, name, n);
1843 nbuf[n] = '\0';
1844 } else
1845 longname = name;
1846 } else {
1847 n = strlen(name);
1848 d = strlen(domain);
1849 if (n + 1 + d + 1 > sizeof(nbuf)) {
1850 *herrno = NO_RECOVERY;
1851 return -1;
1852 }
1853 snprintf(nbuf, sizeof(nbuf), "%s.%s", name, domain);
1854 }
1855 return res_queryN_parallel(longname, target, res, herrno);
1856 }
1857