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_storage sa;
231 return _find_src_addr(&addr.sa, (struct sockaddr*)&sa, mark, uid,
232 /*allow_v6_linklocal=*/mdns) == 1;
233 }
234
have_ipv4(unsigned mark,uid_t uid)235 static int have_ipv4(unsigned mark, uid_t uid) {
236 static const struct sockaddr_in sin_test = {
237 .sin_family = AF_INET,
238 .sin_addr.s_addr = __constant_htonl(0x08080808L) // 8.8.8.8
239 };
240 sockaddr_union addr = {.sin = sin_test};
241 sockaddr_storage sa;
242 return _find_src_addr(&addr.sa, (struct sockaddr*)&sa, mark, uid,
243 /*(don't care) allow_v6_linklocal=*/false) == 1;
244 }
245
246 // Internal version of getaddrinfo(), but limited to AI_NUMERICHOST.
247 // NOTE: also called by resolv_set_nameservers().
getaddrinfo_numeric(const char * hostname,const char * servname,addrinfo hints,addrinfo ** result)248 int getaddrinfo_numeric(const char* hostname, const char* servname, addrinfo hints,
249 addrinfo** result) {
250 hints.ai_flags = AI_NUMERICHOST;
251 const android_net_context netcontext = {
252 .app_netid = NETID_UNSET,
253 .app_mark = MARK_UNSET,
254 .dns_netid = NETID_UNSET,
255 .dns_mark = MARK_UNSET,
256 .uid = NET_CONTEXT_INVALID_UID,
257 .pid = NET_CONTEXT_INVALID_PID,
258 };
259 NetworkDnsEventReported event;
260 return android_getaddrinfofornetcontext(hostname, servname, &hints, &netcontext, result,
261 &event);
262 }
263
264 namespace {
265
validateHints(const addrinfo * _Nonnull hints)266 int validateHints(const addrinfo* _Nonnull hints) {
267 if (!hints) return EAI_BADHINTS;
268
269 // error check for hints
270 if (hints->ai_addrlen || hints->ai_canonname || hints->ai_addr || hints->ai_next) {
271 return EAI_BADHINTS;
272 }
273 if (hints->ai_flags & ~AI_MASK) {
274 return EAI_BADFLAGS;
275 }
276 if (!(hints->ai_family == PF_UNSPEC || hints->ai_family == PF_INET ||
277 hints->ai_family == PF_INET6)) {
278 return EAI_FAMILY;
279 }
280
281 // Socket types which are not in explore_options.
282 switch (hints->ai_socktype) {
283 case SOCK_RAW:
284 case SOCK_DGRAM:
285 case SOCK_STREAM:
286 case ANY:
287 break;
288 default:
289 return EAI_SOCKTYPE;
290 }
291
292 if (hints->ai_socktype == ANY || hints->ai_protocol == ANY) return 0;
293
294 // if both socktype/protocol are specified, check if they are meaningful combination.
295 for (const Explore& ex : explore_options) {
296 if (hints->ai_family != ex.e_af) continue;
297 if (ex.e_socktype == ANY) continue;
298 if (ex.e_protocol == ANY) continue;
299 if (hints->ai_socktype == ex.e_socktype && hints->ai_protocol != ex.e_protocol) {
300 return EAI_BADHINTS;
301 }
302 }
303
304 return 0;
305 }
306
307 } // namespace
308
android_getaddrinfofornetcontext(const char * hostname,const char * servname,const addrinfo * hints,const android_net_context * netcontext,addrinfo ** res,NetworkDnsEventReported * event)309 int android_getaddrinfofornetcontext(const char* hostname, const char* servname,
310 const addrinfo* hints, const android_net_context* netcontext,
311 addrinfo** res, NetworkDnsEventReported* event) {
312 // hostname is allowed to be nullptr
313 // servname is allowed to be nullptr
314 // hints is allowed to be nullptr
315 assert(res != nullptr);
316 assert(netcontext != nullptr);
317 assert(event != nullptr);
318
319 addrinfo sentinel = {};
320 addrinfo* cur = &sentinel;
321 int error = 0;
322
323 do {
324 if (hostname == nullptr && servname == nullptr) {
325 error = EAI_NONAME;
326 break;
327 }
328
329 if (hints && (error = validateHints(hints))) break;
330 addrinfo ai = hints ? *hints : addrinfo{};
331
332 // Check for special cases:
333 // (1) numeric servname is disallowed if socktype/protocol are left unspecified.
334 // (2) servname is disallowed for raw and other inet{,6} sockets.
335 if (MATCH_FAMILY(ai.ai_family, PF_INET, 1) || MATCH_FAMILY(ai.ai_family, PF_INET6, 1)) {
336 addrinfo tmp = ai;
337 if (tmp.ai_family == PF_UNSPEC) {
338 tmp.ai_family = PF_INET6;
339 }
340 error = get_portmatch(&tmp, servname);
341 if (error) break;
342 }
343
344 // NULL hostname, or numeric hostname
345 for (const Explore& ex : explore_options) {
346 /* PF_UNSPEC entries are prepared for DNS queries only */
347 if (ex.e_af == PF_UNSPEC) continue;
348
349 if (!MATCH_FAMILY(ai.ai_family, ex.e_af, WILD_AF(ex))) continue;
350 if (!MATCH(ai.ai_socktype, ex.e_socktype, WILD_SOCKTYPE(ex))) continue;
351 if (!MATCH(ai.ai_protocol, ex.e_protocol, WILD_PROTOCOL(ex))) continue;
352
353 addrinfo tmp = ai;
354 if (tmp.ai_family == PF_UNSPEC) tmp.ai_family = ex.e_af;
355 if (tmp.ai_socktype == ANY && ex.e_socktype != ANY) tmp.ai_socktype = ex.e_socktype;
356 if (tmp.ai_protocol == ANY && ex.e_protocol != ANY) tmp.ai_protocol = ex.e_protocol;
357
358 LOG(DEBUG) << __func__ << ": explore_numeric: ai_family=" << tmp.ai_family
359 << " ai_socktype=" << tmp.ai_socktype << " ai_protocol=" << tmp.ai_protocol;
360 if (hostname == nullptr)
361 error = explore_null(&tmp, servname, &cur->ai_next);
362 else
363 error = explore_numeric_scope(&tmp, hostname, servname, &cur->ai_next);
364
365 if (error) break;
366
367 while (cur->ai_next) cur = cur->ai_next;
368 }
369 if (error) break;
370
371 // If numeric representation of AF1 can be interpreted as FQDN
372 // representation of AF2, we need to think again about the code below.
373 if (sentinel.ai_next) break;
374
375 if (hostname == nullptr) {
376 error = EAI_NODATA;
377 break;
378 }
379 if (ai.ai_flags & AI_NUMERICHOST) {
380 error = EAI_NONAME;
381 break;
382 }
383
384 return resolv_getaddrinfo(hostname, servname, hints, netcontext, res, event);
385 } while (0);
386
387 if (error) {
388 freeaddrinfo(sentinel.ai_next);
389 *res = nullptr;
390 } else {
391 *res = sentinel.ai_next;
392 }
393 return error;
394 }
395
resolv_getaddrinfo(const char * _Nonnull hostname,const char * servname,const addrinfo * hints,const android_net_context * _Nonnull netcontext,addrinfo ** _Nonnull res,NetworkDnsEventReported * _Nonnull event)396 int resolv_getaddrinfo(const char* _Nonnull hostname, const char* servname, const addrinfo* hints,
397 const android_net_context* _Nonnull netcontext, addrinfo** _Nonnull res,
398 NetworkDnsEventReported* _Nonnull event) {
399 if (hostname == nullptr && servname == nullptr) return EAI_NONAME;
400 if (hostname == nullptr) return EAI_NODATA;
401
402 // servname is allowed to be nullptr
403 // hints is allowed to be nullptr
404 assert(res != nullptr);
405 assert(netcontext != nullptr);
406 assert(event != nullptr);
407
408 int error = EAI_FAIL;
409 if (hints && (error = validateHints(hints))) {
410 *res = nullptr;
411 return error;
412 }
413
414 addrinfo ai = hints ? *hints : addrinfo{};
415 addrinfo sentinel = {};
416 addrinfo* cur = &sentinel;
417 // hostname as alphanumeric name.
418 // We would like to prefer AF_INET6 over AF_INET, so we'll make a outer loop by AFs.
419 for (const Explore& ex : explore_options) {
420 // Require exact match for family field
421 if (ai.ai_family != ex.e_af) continue;
422
423 if (!MATCH(ai.ai_socktype, ex.e_socktype, WILD_SOCKTYPE(ex))) continue;
424
425 if (!MATCH(ai.ai_protocol, ex.e_protocol, WILD_PROTOCOL(ex))) continue;
426
427 addrinfo tmp = ai;
428 if (tmp.ai_socktype == ANY && ex.e_socktype != ANY) tmp.ai_socktype = ex.e_socktype;
429 if (tmp.ai_protocol == ANY && ex.e_protocol != ANY) tmp.ai_protocol = ex.e_protocol;
430
431 LOG(DEBUG) << __func__ << ": explore_fqdn(): ai_family=" << tmp.ai_family
432 << " ai_socktype=" << tmp.ai_socktype << " ai_protocol=" << tmp.ai_protocol;
433 error = explore_fqdn(&tmp, hostname, servname, &cur->ai_next, netcontext, event);
434
435 while (cur->ai_next) cur = cur->ai_next;
436 }
437
438 // Propagate the last error from explore_fqdn(), but only when *all* attempts failed.
439 if ((*res = sentinel.ai_next)) return 0;
440
441 // TODO: consider removing freeaddrinfo.
442 freeaddrinfo(sentinel.ai_next);
443 *res = nullptr;
444 return (error == 0) ? EAI_FAIL : error;
445 }
446
447 // FQDN hostname, DNS lookup
explore_fqdn(const addrinfo * pai,const char * hostname,const char * servname,addrinfo ** res,const android_net_context * netcontext,NetworkDnsEventReported * event)448 static int explore_fqdn(const addrinfo* pai, const char* hostname, const char* servname,
449 addrinfo** res, const android_net_context* netcontext,
450 NetworkDnsEventReported* event) {
451 assert(pai != nullptr);
452 // hostname may be nullptr
453 // servname may be nullptr
454 assert(res != nullptr);
455
456 addrinfo* result = nullptr;
457 int error = 0;
458
459 // If the servname does not match socktype/protocol, return error code.
460 if ((error = get_portmatch(pai, servname))) return error;
461
462 if (!files_getaddrinfo(netcontext->dns_netid, hostname, pai, &result)) {
463 error = dns_getaddrinfo(hostname, pai, netcontext, &result, event);
464 }
465 if (error) {
466 freeaddrinfo(result);
467 return error;
468 }
469
470 for (addrinfo* cur = result; cur; cur = cur->ai_next) {
471 // canonname should be filled already
472 if ((error = get_port(cur, servname, 0))) {
473 freeaddrinfo(result);
474 return error;
475 }
476 }
477 *res = result;
478 return 0;
479 }
480
481 /*
482 * hostname == NULL.
483 * passive socket -> anyaddr (0.0.0.0 or ::)
484 * non-passive socket -> localhost (127.0.0.1 or ::1)
485 */
explore_null(const struct addrinfo * pai,const char * servname,struct addrinfo ** res)486 static int explore_null(const struct addrinfo* pai, const char* servname, struct addrinfo** res) {
487 int s;
488 const struct afd* afd;
489 struct addrinfo* cur;
490 struct addrinfo sentinel;
491 int error;
492
493 LOG(DEBUG) << __func__;
494
495 assert(pai != NULL);
496 /* servname may be NULL */
497 assert(res != NULL);
498
499 *res = NULL;
500 sentinel.ai_next = NULL;
501 cur = &sentinel;
502
503 /*
504 * filter out AFs that are not supported by the kernel
505 * XXX errno?
506 */
507 s = socket(pai->ai_family, SOCK_DGRAM | SOCK_CLOEXEC, 0);
508 if (s < 0) {
509 if (errno != EMFILE) return 0;
510 } else
511 close(s);
512
513 /*
514 * if the servname does not match socktype/protocol, ignore it.
515 */
516 if (get_portmatch(pai, servname) != 0) return 0;
517
518 afd = find_afd(pai->ai_family);
519 if (afd == NULL) return 0;
520
521 if (pai->ai_flags & AI_PASSIVE) {
522 GET_AI(cur->ai_next, afd, afd->a_addrany);
523 GET_PORT(cur->ai_next, servname);
524 } else {
525 GET_AI(cur->ai_next, afd, afd->a_loopback);
526 GET_PORT(cur->ai_next, servname);
527 }
528 cur = cur->ai_next;
529
530 *res = sentinel.ai_next;
531 return 0;
532
533 free:
534 freeaddrinfo(sentinel.ai_next);
535 return error;
536 }
537
538 /*
539 * numeric hostname
540 */
explore_numeric(const struct addrinfo * pai,const char * hostname,const char * servname,struct addrinfo ** res,const char * canonname)541 static int explore_numeric(const struct addrinfo* pai, const char* hostname, const char* servname,
542 struct addrinfo** res, const char* canonname) {
543 const struct afd* afd;
544 struct addrinfo* cur;
545 struct addrinfo sentinel;
546 int error;
547 char pton[PTON_MAX];
548
549 assert(pai != NULL);
550 /* hostname may be NULL */
551 /* servname may be NULL */
552 assert(res != NULL);
553
554 *res = NULL;
555 sentinel.ai_next = NULL;
556 cur = &sentinel;
557
558 /*
559 * if the servname does not match socktype/protocol, ignore it.
560 */
561 if (get_portmatch(pai, servname) != 0) return 0;
562
563 afd = find_afd(pai->ai_family);
564 if (afd == NULL) return 0;
565
566 if (inet_pton(afd->a_af, hostname, pton) == 1) {
567 if (pai->ai_family == afd->a_af || pai->ai_family == PF_UNSPEC /*?*/) {
568 GET_AI(cur->ai_next, afd, pton);
569 GET_PORT(cur->ai_next, servname);
570 if ((pai->ai_flags & AI_CANONNAME)) {
571 /*
572 * Set the numeric address itself as
573 * the canonical name, based on a
574 * clarification in rfc2553bis-03.
575 */
576 error = get_canonname(pai, cur->ai_next, canonname);
577 if (error != 0) {
578 freeaddrinfo(sentinel.ai_next);
579 return error;
580 }
581 }
582 while (cur->ai_next) cur = cur->ai_next;
583 } else
584 return EAI_FAMILY;
585 }
586
587 *res = sentinel.ai_next;
588 return 0;
589
590 free:
591 freeaddrinfo(sentinel.ai_next);
592 return error;
593 }
594
595 /*
596 * numeric hostname with scope
597 */
explore_numeric_scope(const struct addrinfo * pai,const char * hostname,const char * servname,struct addrinfo ** res)598 static int explore_numeric_scope(const struct addrinfo* pai, const char* hostname,
599 const char* servname, struct addrinfo** res) {
600 const struct afd* afd;
601 struct addrinfo* cur;
602 int error;
603 const char *cp, *scope, *addr;
604 struct sockaddr_in6* sin6;
605
606 LOG(DEBUG) << __func__;
607
608 assert(pai != NULL);
609 /* hostname may be NULL */
610 /* servname may be NULL */
611 assert(res != NULL);
612
613 /*
614 * if the servname does not match socktype/protocol, ignore it.
615 */
616 if (get_portmatch(pai, servname) != 0) return 0;
617
618 afd = find_afd(pai->ai_family);
619 if (afd == NULL) return 0;
620
621 if (!afd->a_scoped) return explore_numeric(pai, hostname, servname, res, hostname);
622
623 cp = strchr(hostname, SCOPE_DELIMITER);
624 if (cp == NULL) return explore_numeric(pai, hostname, servname, res, hostname);
625
626 /*
627 * Handle special case of <scoped_address><delimiter><scope id>
628 */
629 char* hostname2 = strdup(hostname);
630 if (hostname2 == NULL) return EAI_MEMORY;
631 /* terminate at the delimiter */
632 hostname2[cp - hostname] = '\0';
633 addr = hostname2;
634 scope = cp + 1;
635
636 error = explore_numeric(pai, addr, servname, res, hostname);
637 if (error == 0) {
638 uint32_t scopeid;
639
640 for (cur = *res; cur; cur = cur->ai_next) {
641 if (cur->ai_family != AF_INET6) continue;
642 sin6 = (struct sockaddr_in6*) (void*) cur->ai_addr;
643 if (ip6_str2scopeid(scope, sin6, &scopeid) == -1) {
644 free(hostname2);
645 return (EAI_NODATA); /* XXX: is return OK? */
646 }
647 sin6->sin6_scope_id = scopeid;
648 }
649 }
650
651 free(hostname2);
652
653 return error;
654 }
655
get_canonname(const struct addrinfo * pai,struct addrinfo * ai,const char * str)656 static int get_canonname(const struct addrinfo* pai, struct addrinfo* ai, const char* str) {
657 assert(pai != NULL);
658 assert(ai != NULL);
659 assert(str != NULL);
660
661 if ((pai->ai_flags & AI_CANONNAME) != 0) {
662 ai->ai_canonname = strdup(str);
663 if (ai->ai_canonname == NULL) return EAI_MEMORY;
664 }
665 return 0;
666 }
667
get_ai(const struct addrinfo * pai,const struct afd * afd,const char * addr)668 static struct addrinfo* get_ai(const struct addrinfo* pai, const struct afd* afd,
669 const char* addr) {
670 char* p;
671 struct addrinfo* ai;
672
673 assert(pai != NULL);
674 assert(afd != NULL);
675 assert(addr != NULL);
676
677 ai = (struct addrinfo*) calloc(1, sizeof(struct addrinfo) + sizeof(sockaddr_union));
678 if (ai == NULL) return NULL;
679
680 memcpy(ai, pai, sizeof(struct addrinfo));
681 ai->ai_addr = (struct sockaddr*) (void*) (ai + 1);
682 ai->ai_addrlen = afd->a_socklen;
683 ai->ai_addr->sa_family = ai->ai_family = afd->a_af;
684 p = (char*) (void*) (ai->ai_addr);
685 memcpy(p + afd->a_off, addr, (size_t) afd->a_addrlen);
686 return ai;
687 }
688
get_portmatch(const struct addrinfo * ai,const char * servname)689 static int get_portmatch(const struct addrinfo* ai, const char* servname) {
690 assert(ai != NULL);
691 /* servname may be NULL */
692
693 return get_port(ai, servname, 1);
694 }
695
get_port(const struct addrinfo * ai,const char * servname,int matchonly)696 static int get_port(const struct addrinfo* ai, const char* servname, int matchonly) {
697 const char* proto;
698 struct servent* sp;
699 uint port;
700 int allownumeric;
701
702 assert(ai != NULL);
703 /* servname may be NULL */
704
705 if (servname == NULL) return 0;
706 switch (ai->ai_family) {
707 case AF_INET:
708 case AF_INET6:
709 break;
710 default:
711 return 0;
712 }
713
714 switch (ai->ai_socktype) {
715 case SOCK_RAW:
716 return EAI_SERVICE;
717 case SOCK_DGRAM:
718 case SOCK_STREAM:
719 case ANY:
720 allownumeric = 1;
721 break;
722 default:
723 return EAI_SOCKTYPE;
724 }
725
726 if (android::base::ParseUint(servname, &port)) {
727 if (!allownumeric) return EAI_SERVICE;
728 if (port > 65535) return EAI_SERVICE;
729 port = htons(port);
730 } else {
731 if (ai->ai_flags & AI_NUMERICSERV) return EAI_NONAME;
732
733 switch (ai->ai_socktype) {
734 case SOCK_DGRAM:
735 proto = "udp";
736 break;
737 case SOCK_STREAM:
738 proto = "tcp";
739 break;
740 default:
741 proto = NULL;
742 break;
743 }
744
745 if ((sp = getservbyname(servname, proto)) == NULL) return EAI_SERVICE;
746 port = sp->s_port;
747 }
748
749 if (!matchonly) {
750 switch (ai->ai_family) {
751 case AF_INET:
752 ((struct sockaddr_in*) (void*) ai->ai_addr)->sin_port = port;
753 break;
754 case AF_INET6:
755 ((struct sockaddr_in6*) (void*) ai->ai_addr)->sin6_port = port;
756 break;
757 }
758 }
759
760 return 0;
761 }
762
find_afd(int af)763 static const struct afd* find_afd(int af) {
764 const struct afd* afd;
765
766 if (af == PF_UNSPEC) return NULL;
767 for (afd = afdl; afd->a_af; afd++) {
768 if (afd->a_af == af) return afd;
769 }
770 return NULL;
771 }
772
773 // Convert a string to a scope identifier.
ip6_str2scopeid(const char * scope,struct sockaddr_in6 * sin6,uint32_t * scopeid)774 static int ip6_str2scopeid(const char* scope, struct sockaddr_in6* sin6, uint32_t* scopeid) {
775 struct in6_addr* a6;
776
777 assert(scope != NULL);
778 assert(sin6 != NULL);
779 assert(scopeid != NULL);
780
781 a6 = &sin6->sin6_addr;
782
783 /* empty scopeid portion is invalid */
784 if (*scope == '\0') return -1;
785
786 if (IN6_IS_ADDR_LINKLOCAL(a6) || IN6_IS_ADDR_MC_LINKLOCAL(a6)) {
787 /*
788 * We currently assume a one-to-one mapping between links
789 * and interfaces, so we simply use interface indices for
790 * like-local scopes.
791 */
792 *scopeid = if_nametoindex(scope);
793 if (*scopeid != 0) return 0;
794 }
795
796 /* try to convert to a numeric id as a last resort*/
797 if (!android::base::ParseUint(scope, scopeid)) return -1;
798
799 return 0;
800 }
801
802 /* code duplicate with gethnamaddr.c */
803
804 #define BOUNDED_INCR(x) \
805 do { \
806 BOUNDS_CHECK(cp, x); \
807 cp += (x); \
808 } while (0)
809
810 #define BOUNDS_CHECK(ptr, count) \
811 do { \
812 if (eom - (ptr) < (count)) { \
813 *herrno = NO_RECOVERY; \
814 return NULL; \
815 } \
816 } while (0)
817
getanswer(const std::vector<uint8_t> & answer,int anslen,const char * qname,int qtype,const struct addrinfo * pai,int * herrno)818 static struct addrinfo* getanswer(const std::vector<uint8_t>& answer, int anslen, const char* qname,
819 int qtype, const struct addrinfo* pai, int* herrno) {
820 struct addrinfo sentinel = {};
821 struct addrinfo *cur;
822 struct addrinfo ai;
823 const struct afd* afd;
824 char* canonname;
825 const HEADER* hp;
826 const uint8_t* cp;
827 int n;
828 const uint8_t* eom;
829 char *bp, *ep;
830 int type, ancount, qdcount;
831 int haveanswer, had_error;
832 char tbuf[MAXDNAME];
833 char hostbuf[8 * 1024];
834
835 assert(qname != NULL);
836 assert(pai != NULL);
837
838 cur = &sentinel;
839
840 canonname = NULL;
841 eom = answer.data() + anslen;
842
843 bool (*name_ok)(const char* dn);
844 switch (qtype) {
845 case T_A:
846 case T_AAAA:
847 case T_ANY: /*use T_ANY only for T_A/T_AAAA lookup*/
848 name_ok = res_hnok;
849 break;
850 default:
851 return NULL; /* XXX should be abort(); */
852 }
853 /*
854 * find first satisfactory answer
855 */
856 hp = reinterpret_cast<const HEADER*>(answer.data());
857 ancount = ntohs(hp->ancount);
858 qdcount = ntohs(hp->qdcount);
859 bp = hostbuf;
860 ep = hostbuf + sizeof hostbuf;
861 cp = answer.data();
862 BOUNDED_INCR(HFIXEDSZ);
863 if (qdcount != 1) {
864 *herrno = NO_RECOVERY;
865 return (NULL);
866 }
867 n = dn_expand(answer.data(), eom, cp, bp, ep - bp);
868 if ((n < 0) || !(*name_ok)(bp)) {
869 *herrno = NO_RECOVERY;
870 return (NULL);
871 }
872 BOUNDED_INCR(n + QFIXEDSZ);
873 if (qtype == T_A || qtype == T_AAAA || qtype == T_ANY) {
874 /* res_send() has already verified that the query name is the
875 * same as the one we sent; this just gets the expanded name
876 * (i.e., with the succeeding search-domain tacked on).
877 */
878 n = strlen(bp) + 1; /* for the \0 */
879 if (n >= MAXHOSTNAMELEN) {
880 *herrno = NO_RECOVERY;
881 return (NULL);
882 }
883 canonname = bp;
884 bp += n;
885 /* The qname can be abbreviated, but h_name is now absolute. */
886 qname = canonname;
887 }
888 haveanswer = 0;
889 had_error = 0;
890 while (ancount-- > 0 && cp < eom && !had_error) {
891 n = dn_expand(answer.data(), eom, cp, bp, ep - bp);
892 if ((n < 0) || !(*name_ok)(bp)) {
893 had_error++;
894 continue;
895 }
896 cp += n; /* name */
897 BOUNDS_CHECK(cp, 3 * INT16SZ + INT32SZ);
898 type = ntohs(*reinterpret_cast<const uint16_t*>(cp));
899 cp += INT16SZ; /* type */
900 int cl = ntohs(*reinterpret_cast<const uint16_t*>(cp));
901 cp += INT16SZ + INT32SZ; /* class, TTL */
902 n = ntohs(*reinterpret_cast<const uint16_t*>(cp));
903 cp += INT16SZ; /* len */
904 BOUNDS_CHECK(cp, n);
905 if (cl != C_IN) {
906 /* XXX - debug? syslog? */
907 cp += n;
908 continue; /* XXX - had_error++ ? */
909 }
910 if ((qtype == T_A || qtype == T_AAAA || qtype == T_ANY) && type == T_CNAME) {
911 n = dn_expand(answer.data(), eom, cp, tbuf, sizeof tbuf);
912 if ((n < 0) || !(*name_ok)(tbuf)) {
913 had_error++;
914 continue;
915 }
916 cp += n;
917 /* Get canonical name. */
918 n = strlen(tbuf) + 1; /* for the \0 */
919 if (n > ep - bp || n >= MAXHOSTNAMELEN) {
920 had_error++;
921 continue;
922 }
923 strlcpy(bp, tbuf, (size_t)(ep - bp));
924 canonname = bp;
925 bp += n;
926 continue;
927 }
928 if (qtype == T_ANY) {
929 if (!(type == T_A || type == T_AAAA)) {
930 cp += n;
931 continue;
932 }
933 } else if (type != qtype) {
934 if (type != T_KEY && type != T_SIG)
935 LOG(DEBUG) << __func__ << ": asked for \"" << qname << " " << p_class(C_IN) << " "
936 << p_type(qtype) << "\", got type \"" << p_type(type) << "\"";
937 cp += n;
938 continue; /* XXX - had_error++ ? */
939 }
940 switch (type) {
941 case T_A:
942 case T_AAAA:
943 if (strcasecmp(canonname, bp) != 0) {
944 LOG(DEBUG) << __func__ << ": asked for \"" << canonname << "\", got \"" << bp
945 << "\"";
946 cp += n;
947 continue; /* XXX - had_error++ ? */
948 }
949 if (type == T_A && n != INADDRSZ) {
950 cp += n;
951 continue;
952 }
953 if (type == T_AAAA && n != IN6ADDRSZ) {
954 cp += n;
955 continue;
956 }
957 if (type == T_AAAA) {
958 struct in6_addr in6;
959 memcpy(&in6, cp, IN6ADDRSZ);
960 if (IN6_IS_ADDR_V4MAPPED(&in6)) {
961 cp += n;
962 continue;
963 }
964 }
965 if (!haveanswer) {
966 int nn;
967
968 canonname = bp;
969 nn = strlen(bp) + 1; /* for the \0 */
970 bp += nn;
971 }
972
973 /* don't overwrite pai */
974 ai = *pai;
975 ai.ai_family = (type == T_A) ? AF_INET : AF_INET6;
976 afd = find_afd(ai.ai_family);
977 if (afd == NULL) {
978 cp += n;
979 continue;
980 }
981 cur->ai_next = get_ai(&ai, afd, (const char*) cp);
982 if (cur->ai_next == NULL) had_error++;
983 while (cur && cur->ai_next) cur = cur->ai_next;
984 cp += n;
985 break;
986 default:
987 abort();
988 }
989 if (!had_error) haveanswer++;
990 }
991 if (haveanswer) {
992 if (!canonname)
993 (void) get_canonname(pai, sentinel.ai_next, qname);
994 else
995 (void) get_canonname(pai, sentinel.ai_next, canonname);
996 *herrno = NETDB_SUCCESS;
997 return sentinel.ai_next;
998 }
999
1000 *herrno = NO_RECOVERY;
1001 return NULL;
1002 }
1003
1004 struct addrinfo_sort_elem {
1005 struct addrinfo* ai;
1006 int has_src_addr;
1007 sockaddr_union src_addr;
1008 int original_order;
1009 };
1010
_get_scope(const struct sockaddr * addr)1011 static int _get_scope(const struct sockaddr* addr) {
1012 if (addr->sa_family == AF_INET6) {
1013 const struct sockaddr_in6* addr6 = (const struct sockaddr_in6*) addr;
1014 if (IN6_IS_ADDR_MULTICAST(&addr6->sin6_addr)) {
1015 return IPV6_ADDR_MC_SCOPE(&addr6->sin6_addr);
1016 } else if (IN6_IS_ADDR_LOOPBACK(&addr6->sin6_addr) ||
1017 IN6_IS_ADDR_LINKLOCAL(&addr6->sin6_addr)) {
1018 /*
1019 * RFC 4291 section 2.5.3 says loopback is to be treated as having
1020 * link-local scope.
1021 */
1022 return IPV6_ADDR_SCOPE_LINKLOCAL;
1023 } else if (IN6_IS_ADDR_SITELOCAL(&addr6->sin6_addr)) {
1024 return IPV6_ADDR_SCOPE_SITELOCAL;
1025 } else {
1026 return IPV6_ADDR_SCOPE_GLOBAL;
1027 }
1028 } else if (addr->sa_family == AF_INET) {
1029 const struct sockaddr_in* addr4 = (const struct sockaddr_in*) addr;
1030 unsigned long int na = ntohl(addr4->sin_addr.s_addr);
1031
1032 if (IN_LOOPBACK(na) || /* 127.0.0.0/8 */
1033 (na & 0xffff0000) == 0xa9fe0000) { /* 169.254.0.0/16 */
1034 return IPV6_ADDR_SCOPE_LINKLOCAL;
1035 } else {
1036 /*
1037 * RFC 6724 section 3.2. Other IPv4 addresses, including private addresses
1038 * and shared addresses (100.64.0.0/10), are assigned global scope.
1039 */
1040 return IPV6_ADDR_SCOPE_GLOBAL;
1041 }
1042 } else {
1043 /*
1044 * This should never happen.
1045 * Return a scope with low priority as a last resort.
1046 */
1047 return IPV6_ADDR_SCOPE_NODELOCAL;
1048 }
1049 }
1050
1051 /* These macros are modelled after the ones in <netinet/in6.h>. */
1052
1053 /* RFC 4380, section 2.6 */
1054 #define IN6_IS_ADDR_TEREDO(a) \
1055 ((*(const uint32_t*) (const void*) (&(a)->s6_addr[0]) == ntohl(0x20010000)))
1056
1057 /* RFC 3056, section 2. */
1058 #define IN6_IS_ADDR_6TO4(a) (((a)->s6_addr[0] == 0x20) && ((a)->s6_addr[1] == 0x02))
1059
1060 /* 6bone testing address area (3ffe::/16), deprecated in RFC 3701. */
1061 #define IN6_IS_ADDR_6BONE(a) (((a)->s6_addr[0] == 0x3f) && ((a)->s6_addr[1] == 0xfe))
1062
1063 /*
1064 * Get the label for a given IPv4/IPv6 address.
1065 * RFC 6724, section 2.1.
1066 */
1067
_get_label(const struct sockaddr * addr)1068 static int _get_label(const struct sockaddr* addr) {
1069 if (addr->sa_family == AF_INET) {
1070 return 4;
1071 } else if (addr->sa_family == AF_INET6) {
1072 const struct sockaddr_in6* addr6 = (const struct sockaddr_in6*) addr;
1073 if (IN6_IS_ADDR_LOOPBACK(&addr6->sin6_addr)) {
1074 return 0;
1075 } else if (IN6_IS_ADDR_V4MAPPED(&addr6->sin6_addr)) {
1076 return 4;
1077 } else if (IN6_IS_ADDR_6TO4(&addr6->sin6_addr)) {
1078 return 2;
1079 } else if (IN6_IS_ADDR_TEREDO(&addr6->sin6_addr)) {
1080 return 5;
1081 } else if (IN6_IS_ADDR_ULA(&addr6->sin6_addr)) {
1082 return 13;
1083 } else if (IN6_IS_ADDR_V4COMPAT(&addr6->sin6_addr)) {
1084 return 3;
1085 } else if (IN6_IS_ADDR_SITELOCAL(&addr6->sin6_addr)) {
1086 return 11;
1087 } else if (IN6_IS_ADDR_6BONE(&addr6->sin6_addr)) {
1088 return 12;
1089 } else {
1090 /* All other IPv6 addresses, including global unicast addresses. */
1091 return 1;
1092 }
1093 } else {
1094 /*
1095 * This should never happen.
1096 * Return a semi-random label as a last resort.
1097 */
1098 return 1;
1099 }
1100 }
1101
1102 /*
1103 * Get the precedence for a given IPv4/IPv6 address.
1104 * RFC 6724, section 2.1.
1105 */
1106
_get_precedence(const struct sockaddr * addr)1107 static int _get_precedence(const struct sockaddr* addr) {
1108 if (addr->sa_family == AF_INET) {
1109 return 35;
1110 } else if (addr->sa_family == AF_INET6) {
1111 const struct sockaddr_in6* addr6 = (const struct sockaddr_in6*) addr;
1112 if (IN6_IS_ADDR_LOOPBACK(&addr6->sin6_addr)) {
1113 return 50;
1114 } else if (IN6_IS_ADDR_V4MAPPED(&addr6->sin6_addr)) {
1115 return 35;
1116 } else if (IN6_IS_ADDR_6TO4(&addr6->sin6_addr)) {
1117 return 30;
1118 } else if (IN6_IS_ADDR_TEREDO(&addr6->sin6_addr)) {
1119 return 5;
1120 } else if (IN6_IS_ADDR_ULA(&addr6->sin6_addr)) {
1121 return 3;
1122 } else if (IN6_IS_ADDR_V4COMPAT(&addr6->sin6_addr) ||
1123 IN6_IS_ADDR_SITELOCAL(&addr6->sin6_addr) ||
1124 IN6_IS_ADDR_6BONE(&addr6->sin6_addr)) {
1125 return 1;
1126 } else {
1127 /* All other IPv6 addresses, including global unicast addresses. */
1128 return 40;
1129 }
1130 } else {
1131 return 1;
1132 }
1133 }
1134
1135 /*
1136 * Find number of matching initial bits between the two addresses a1 and a2.
1137 */
1138
_common_prefix_len(const struct in6_addr * a1,const struct in6_addr * a2)1139 static int _common_prefix_len(const struct in6_addr* a1, const struct in6_addr* a2) {
1140 const char* p1 = (const char*) a1;
1141 const char* p2 = (const char*) a2;
1142 unsigned i;
1143
1144 for (i = 0; i < sizeof(*a1); ++i) {
1145 int x, j;
1146
1147 if (p1[i] == p2[i]) {
1148 continue;
1149 }
1150 x = p1[i] ^ p2[i];
1151 for (j = 0; j < CHAR_BIT; ++j) {
1152 if (x & (1 << (CHAR_BIT - 1))) {
1153 return i * CHAR_BIT + j;
1154 }
1155 x <<= 1;
1156 }
1157 }
1158 return sizeof(*a1) * CHAR_BIT;
1159 }
1160
1161 /*
1162 * Compare two source/destination address pairs.
1163 * RFC 6724, section 6.
1164 */
1165
_rfc6724_compare(const void * ptr1,const void * ptr2)1166 static int _rfc6724_compare(const void* ptr1, const void* ptr2) {
1167 const struct addrinfo_sort_elem* a1 = (const struct addrinfo_sort_elem*) ptr1;
1168 const struct addrinfo_sort_elem* a2 = (const struct addrinfo_sort_elem*) ptr2;
1169 int scope_src1, scope_dst1, scope_match1;
1170 int scope_src2, scope_dst2, scope_match2;
1171 int label_src1, label_dst1, label_match1;
1172 int label_src2, label_dst2, label_match2;
1173 int precedence1, precedence2;
1174 int prefixlen1, prefixlen2;
1175
1176 /* Rule 1: Avoid unusable destinations. */
1177 if (a1->has_src_addr != a2->has_src_addr) {
1178 return a2->has_src_addr - a1->has_src_addr;
1179 }
1180
1181 /* Rule 2: Prefer matching scope. */
1182 scope_src1 = _get_scope(&a1->src_addr.sa);
1183 scope_dst1 = _get_scope(a1->ai->ai_addr);
1184 scope_match1 = (scope_src1 == scope_dst1);
1185
1186 scope_src2 = _get_scope(&a2->src_addr.sa);
1187 scope_dst2 = _get_scope(a2->ai->ai_addr);
1188 scope_match2 = (scope_src2 == scope_dst2);
1189
1190 if (scope_match1 != scope_match2) {
1191 return scope_match2 - scope_match1;
1192 }
1193
1194 /*
1195 * Rule 3: Avoid deprecated addresses.
1196 * TODO(sesse): We don't currently have a good way of finding this.
1197 */
1198
1199 /*
1200 * Rule 4: Prefer home addresses.
1201 * TODO(sesse): We don't currently have a good way of finding this.
1202 */
1203
1204 /* Rule 5: Prefer matching label. */
1205 label_src1 = _get_label(&a1->src_addr.sa);
1206 label_dst1 = _get_label(a1->ai->ai_addr);
1207 label_match1 = (label_src1 == label_dst1);
1208
1209 label_src2 = _get_label(&a2->src_addr.sa);
1210 label_dst2 = _get_label(a2->ai->ai_addr);
1211 label_match2 = (label_src2 == label_dst2);
1212
1213 if (label_match1 != label_match2) {
1214 return label_match2 - label_match1;
1215 }
1216
1217 /* Rule 6: Prefer higher precedence. */
1218 precedence1 = _get_precedence(a1->ai->ai_addr);
1219 precedence2 = _get_precedence(a2->ai->ai_addr);
1220 if (precedence1 != precedence2) {
1221 return precedence2 - precedence1;
1222 }
1223
1224 /*
1225 * Rule 7: Prefer native transport.
1226 * TODO(sesse): We don't currently have a good way of finding this.
1227 */
1228
1229 /* Rule 8: Prefer smaller scope. */
1230 if (scope_dst1 != scope_dst2) {
1231 return scope_dst1 - scope_dst2;
1232 }
1233
1234 /*
1235 * Rule 9: Use longest matching prefix.
1236 * We implement this for IPv6 only, as the rules in RFC 6724 don't seem
1237 * to work very well directly applied to IPv4. (glibc uses information from
1238 * the routing table for a custom IPv4 implementation here.)
1239 */
1240 if (a1->has_src_addr && a1->ai->ai_addr->sa_family == AF_INET6 && a2->has_src_addr &&
1241 a2->ai->ai_addr->sa_family == AF_INET6) {
1242 const struct sockaddr_in6* a1_src = &a1->src_addr.sin6;
1243 const struct sockaddr_in6* a1_dst = (const struct sockaddr_in6*) a1->ai->ai_addr;
1244 const struct sockaddr_in6* a2_src = &a2->src_addr.sin6;
1245 const struct sockaddr_in6* a2_dst = (const struct sockaddr_in6*) a2->ai->ai_addr;
1246 prefixlen1 = _common_prefix_len(&a1_src->sin6_addr, &a1_dst->sin6_addr);
1247 prefixlen2 = _common_prefix_len(&a2_src->sin6_addr, &a2_dst->sin6_addr);
1248 if (prefixlen1 != prefixlen2) {
1249 return prefixlen2 - prefixlen1;
1250 }
1251 }
1252
1253 /*
1254 * Rule 10: Leave the order unchanged.
1255 * We need this since qsort() is not necessarily stable.
1256 */
1257 return a1->original_order - a2->original_order;
1258 }
1259
1260 /*
1261 * Find the source address that will be used if trying to connect to the given
1262 * address. src_addr must be assigned and large enough to hold a struct sockaddr_in6.
1263 * allow_v6_linklocal controls whether to accept link-local source addresses.
1264 *
1265 * Returns 1 if a source address was found, 0 if the address is unreachable,
1266 * and -1 if a fatal error occurred. If 0 or -1, the contents of src_addr are
1267 * undefined.
1268 */
1269
_find_src_addr(const struct sockaddr * addr,struct sockaddr * src_addr,unsigned mark,uid_t uid,bool allow_v6_linklocal)1270 static int _find_src_addr(const struct sockaddr* addr, struct sockaddr* src_addr, unsigned mark,
1271 uid_t uid, bool allow_v6_linklocal) {
1272 if (src_addr == nullptr) return -1;
1273
1274 int ret;
1275 socklen_t len;
1276
1277 switch (addr->sa_family) {
1278 case AF_INET:
1279 len = sizeof(struct sockaddr_in);
1280 break;
1281 case AF_INET6:
1282 len = sizeof(struct sockaddr_in6);
1283 break;
1284 default:
1285 /* No known usable source address for non-INET families. */
1286 return 0;
1287 }
1288
1289 android::base::unique_fd sock(socket(addr->sa_family, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP));
1290 if (sock.get() == -1) {
1291 if (errno == EAFNOSUPPORT) {
1292 return 0;
1293 } else {
1294 return -1;
1295 }
1296 }
1297 if (mark != MARK_UNSET && setsockopt(sock, SOL_SOCKET, SO_MARK, &mark, sizeof(mark)) < 0) {
1298 return 0;
1299 }
1300 if (uid > 0 && uid != NET_CONTEXT_INVALID_UID && fchown(sock, uid, (gid_t) -1) < 0) {
1301 return 0;
1302 }
1303 do {
1304 ret = connect(sock, addr, len);
1305 } while (ret == -1 && errno == EINTR);
1306
1307 if (ret == -1) {
1308 return 0;
1309 }
1310
1311 if (getsockname(sock, src_addr, &len) == -1) {
1312 return -1;
1313 }
1314
1315 if (src_addr->sa_family == AF_INET6) {
1316 sockaddr_in6* sin6 = reinterpret_cast<sockaddr_in6*>(src_addr);
1317 if (!allow_v6_linklocal && IN6_IS_ADDR_LINKLOCAL(&sin6->sin6_addr)) {
1318 // There is no point in sending an AAAA query because the device does not have a global
1319 // IP address. The only thing that can be affected is the hostname "localhost". Devices
1320 // with this setting will not be able to get the localhost v6 IP address ::1 via DNS
1321 // lookups, which is accessible by host local. But it is expected that a DNS server that
1322 // replies to "localhost" in AAAA should also reply in A. So it shouldn't cause issues.
1323 // Also, the current behavior will not be changed because hostname “localhost” only gets
1324 // 127.0.0.1 per etc/hosts configs.
1325 return 0;
1326 }
1327 }
1328
1329 return 1;
1330 }
1331
1332 /*
1333 * Sort the linked list starting at sentinel->ai_next in RFC6724 order.
1334 * Will leave the list unchanged if an error occurs.
1335 */
1336
resolv_rfc6724_sort(struct addrinfo * list_sentinel,unsigned mark,uid_t uid)1337 void resolv_rfc6724_sort(struct addrinfo* list_sentinel, unsigned mark, uid_t uid) {
1338 if (list_sentinel == nullptr) return;
1339
1340 struct addrinfo* cur;
1341 int nelem = 0, i;
1342 struct addrinfo_sort_elem* elems;
1343
1344 cur = list_sentinel->ai_next;
1345 while (cur) {
1346 ++nelem;
1347 cur = cur->ai_next;
1348 }
1349
1350 elems = (struct addrinfo_sort_elem*) calloc(nelem, sizeof(struct addrinfo_sort_elem));
1351 if (elems == NULL) {
1352 goto error;
1353 }
1354
1355 /*
1356 * Convert the linked list to an array that also contains the candidate
1357 * source address for each destination address.
1358 */
1359 for (i = 0, cur = list_sentinel->ai_next; i < nelem; ++i, cur = cur->ai_next) {
1360 int has_src_addr;
1361 assert(cur != NULL);
1362 elems[i].ai = cur;
1363 elems[i].original_order = i;
1364
1365 has_src_addr = _find_src_addr(cur->ai_addr, &elems[i].src_addr.sa, mark, uid,
1366 /*allow_v6_linklocal=*/true);
1367 if (has_src_addr == -1) {
1368 goto error;
1369 }
1370 elems[i].has_src_addr = has_src_addr;
1371 }
1372
1373 /* Sort the addresses, and rearrange the linked list so it matches the sorted order. */
1374 qsort((void*) elems, nelem, sizeof(struct addrinfo_sort_elem), _rfc6724_compare);
1375
1376 list_sentinel->ai_next = elems[0].ai;
1377 for (i = 0; i < nelem - 1; ++i) {
1378 elems[i].ai->ai_next = elems[i + 1].ai;
1379 }
1380 elems[nelem - 1].ai->ai_next = NULL;
1381
1382 error:
1383 free(elems);
1384 }
1385
dns_getaddrinfo(const char * name,const addrinfo * pai,const android_net_context * netcontext,addrinfo ** rv,NetworkDnsEventReported * event)1386 static int dns_getaddrinfo(const char* name, const addrinfo* pai,
1387 const android_net_context* netcontext, addrinfo** rv,
1388 NetworkDnsEventReported* event) {
1389 res_target q = {};
1390 res_target q2 = {};
1391 ResState res(netcontext, event);
1392 setMdnsFlag(name, res.netid, &(res.flags));
1393
1394 switch (pai->ai_family) {
1395 case AF_UNSPEC: {
1396 /* prefer IPv6 */
1397 q.name = name;
1398 q.qclass = C_IN;
1399 int query_ipv6 = 1, query_ipv4 = 1;
1400 if (pai->ai_flags & AI_ADDRCONFIG) {
1401 query_ipv6 = have_ipv6(netcontext->app_mark, netcontext->uid,
1402 isMdnsResolution(res.flags));
1403 query_ipv4 = have_ipv4(netcontext->app_mark, netcontext->uid);
1404 }
1405 if (query_ipv6) {
1406 q.qtype = T_AAAA;
1407 if (query_ipv4) {
1408 q.next = &q2;
1409 q2.name = name;
1410 q2.qclass = C_IN;
1411 q2.qtype = T_A;
1412 }
1413 } else if (query_ipv4) {
1414 q.qtype = T_A;
1415 } else {
1416 return EAI_NODATA;
1417 }
1418 break;
1419 }
1420 case AF_INET:
1421 q.name = name;
1422 q.qclass = C_IN;
1423 q.qtype = T_A;
1424 break;
1425 case AF_INET6:
1426 q.name = name;
1427 q.qclass = C_IN;
1428 q.qtype = T_AAAA;
1429 break;
1430 default:
1431 return EAI_FAMILY;
1432 }
1433
1434 int he;
1435 if (res_searchN(name, &q, &res, &he) < 0) {
1436 // Return h_errno (he) to catch more detailed errors rather than EAI_NODATA.
1437 // Note that res_searchN() doesn't set the pair NETDB_INTERNAL and errno.
1438 // See also herrnoToAiErrno().
1439 return herrnoToAiErrno(he);
1440 }
1441
1442 addrinfo sentinel = {};
1443 addrinfo* cur = &sentinel;
1444 addrinfo* ai = getanswer(q.answer, q.n, q.name, q.qtype, pai, &he);
1445 if (ai) {
1446 cur->ai_next = ai;
1447 while (cur && cur->ai_next) cur = cur->ai_next;
1448 }
1449 if (q.next) {
1450 ai = getanswer(q2.answer, q2.n, q2.name, q2.qtype, pai, &he);
1451 if (ai) cur->ai_next = ai;
1452 }
1453 if (sentinel.ai_next == NULL) {
1454 // Note that getanswer() doesn't set the pair NETDB_INTERNAL and errno.
1455 // See also herrnoToAiErrno().
1456 return herrnoToAiErrno(he);
1457 }
1458
1459 resolv_rfc6724_sort(&sentinel, netcontext->app_mark, netcontext->uid);
1460
1461 *rv = sentinel.ai_next;
1462 return 0;
1463 }
1464
_sethtent(FILE ** hostf)1465 static void _sethtent(FILE** hostf) {
1466 if (!*hostf)
1467 *hostf = fopen(_PATH_HOSTS, "re");
1468 else
1469 rewind(*hostf);
1470 }
1471
_endhtent(FILE ** hostf)1472 static void _endhtent(FILE** hostf) {
1473 if (*hostf) {
1474 (void) fclose(*hostf);
1475 *hostf = NULL;
1476 }
1477 }
1478
_gethtent(FILE ** hostf,const char * name,const struct addrinfo * pai)1479 static struct addrinfo* _gethtent(FILE** hostf, const char* name, const struct addrinfo* pai) {
1480 char* p;
1481 char *cp, *tname, *cname;
1482 struct addrinfo *res0, *res;
1483 int error;
1484 const char* addr;
1485 char hostbuf[8 * 1024];
1486
1487 assert(name != NULL);
1488 assert(pai != NULL);
1489
1490 if (!*hostf && !(*hostf = fopen(_PATH_HOSTS, "re"))) return (NULL);
1491 again:
1492 if (!(p = fgets(hostbuf, sizeof hostbuf, *hostf))) return (NULL);
1493 if (*p == '#') goto again;
1494 if (!(cp = strpbrk(p, "#\n"))) goto again;
1495 *cp = '\0';
1496 if (!(cp = strpbrk(p, " \t"))) goto again;
1497 *cp++ = '\0';
1498 addr = p;
1499 /* if this is not something we're looking for, skip it. */
1500 cname = NULL;
1501 while (cp && *cp) {
1502 if (*cp == ' ' || *cp == '\t') {
1503 cp++;
1504 continue;
1505 }
1506 if (!cname) cname = cp;
1507 tname = cp;
1508 if ((cp = strpbrk(cp, " \t")) != NULL) *cp++ = '\0';
1509 if (strcasecmp(name, tname) == 0) goto found;
1510 }
1511 goto again;
1512
1513 found:
1514 error = getaddrinfo_numeric(addr, nullptr, *pai, &res0);
1515 if (error) goto again;
1516 for (res = res0; res; res = res->ai_next) {
1517 /* cover it up */
1518 res->ai_flags = pai->ai_flags;
1519
1520 if (pai->ai_flags & AI_CANONNAME) {
1521 if (get_canonname(pai, res, cname) != 0) {
1522 freeaddrinfo(res0);
1523 goto again;
1524 }
1525 }
1526 }
1527 return res0;
1528 }
1529
getCustomHosts(const size_t netid,const char * _Nonnull name,const struct addrinfo * _Nonnull pai)1530 static struct addrinfo* getCustomHosts(const size_t netid, const char* _Nonnull name,
1531 const struct addrinfo* _Nonnull pai) {
1532 struct addrinfo sentinel = {};
1533 struct addrinfo *res0, *res;
1534 res = &sentinel;
1535 std::vector<std::string> hosts = getCustomizedTableByName(netid, name);
1536 for (const std::string& host : hosts) {
1537 int error = getaddrinfo_numeric(host.c_str(), nullptr, *pai, &res0);
1538 if (!error && res0 != nullptr) {
1539 res->ai_next = res0;
1540 res = res0;
1541 res0 = nullptr;
1542 }
1543 }
1544 return sentinel.ai_next;
1545 }
1546
files_getaddrinfo(const size_t netid,const char * name,const addrinfo * pai,addrinfo ** res)1547 static bool files_getaddrinfo(const size_t netid, const char* name, const addrinfo* pai,
1548 addrinfo** res) {
1549 struct addrinfo sentinel = {};
1550 struct addrinfo *p, *cur;
1551 FILE* hostf = nullptr;
1552
1553 cur = &sentinel;
1554 _sethtent(&hostf);
1555 while ((p = _gethtent(&hostf, name, pai)) != nullptr) {
1556 cur->ai_next = p;
1557 while (cur && cur->ai_next) cur = cur->ai_next;
1558 }
1559 _endhtent(&hostf);
1560
1561 if ((p = getCustomHosts(netid, name, pai)) != nullptr) {
1562 cur->ai_next = p;
1563 }
1564
1565 *res = sentinel.ai_next;
1566 return sentinel.ai_next != nullptr;
1567 }
1568
1569 /* resolver logic */
1570
1571 namespace {
1572
1573 constexpr int SLEEP_TIME_MS = 2;
1574
getHerrnoFromRcode(int rcode)1575 int getHerrnoFromRcode(int rcode) {
1576 switch (rcode) {
1577 // Not defined in RFC.
1578 case RCODE_TIMEOUT:
1579 // DNS metrics monitors DNS query timeout.
1580 return NETD_RESOLV_H_ERRNO_EXT_TIMEOUT; // extended h_errno.
1581 // Defined in RFC 1035 section 4.1.1.
1582 case NXDOMAIN:
1583 return HOST_NOT_FOUND;
1584 case SERVFAIL:
1585 return TRY_AGAIN;
1586 case NOERROR:
1587 return NO_DATA;
1588 case FORMERR:
1589 case NOTIMP:
1590 case REFUSED:
1591 default:
1592 return NO_RECOVERY;
1593 }
1594 }
1595
1596 struct QueryResult {
1597 int ancount;
1598 int rcode;
1599 int herrno;
1600 int qerrno;
1601 NetworkDnsEventReported event;
1602 };
1603
1604 // Formulate a normal query, send, and await answer.
1605 // Caller must parse answer and determine whether it answers the question.
doQuery(const char * name,res_target * t,ResState * res,std::chrono::milliseconds sleepTimeMs)1606 QueryResult doQuery(const char* name, res_target* t, ResState* res,
1607 std::chrono::milliseconds sleepTimeMs) {
1608 HEADER* hp = (HEADER*)(void*)t->answer.data();
1609
1610 hp->rcode = NOERROR; // default
1611
1612 const int cl = t->qclass;
1613 const int type = t->qtype;
1614 const int anslen = t->answer.size();
1615
1616 LOG(DEBUG) << __func__ << ": (" << cl << ", " << type << ")";
1617
1618 uint8_t buf[MAXPACKET];
1619 int n = res_nmkquery(QUERY, name, cl, type, {}, buf, res->netcontext_flags);
1620
1621 if (n > 0 &&
1622 (res->netcontext_flags & (NET_CONTEXT_FLAG_USE_DNS_OVER_TLS | NET_CONTEXT_FLAG_USE_EDNS))) {
1623 n = res_nopt(res, n, buf, anslen);
1624 }
1625
1626 NetworkDnsEventReported event;
1627 if (n <= 0) {
1628 LOG(ERROR) << __func__ << ": res_nmkquery failed";
1629 return {
1630 .ancount = 0,
1631 .rcode = -1,
1632 .herrno = NO_RECOVERY,
1633 .qerrno = errno,
1634 .event = event,
1635 };
1636 }
1637
1638 ResState res_temp = res->clone(&event);
1639
1640 int rcode = NOERROR;
1641 n = res_nsend(&res_temp, std::span(buf, n), std::span(t->answer.data(), anslen), &rcode, 0,
1642 sleepTimeMs);
1643 if (n < 0 || hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
1644 if (rcode != RCODE_TIMEOUT) rcode = hp->rcode;
1645 // if the query choked with EDNS0, retry without EDNS0
1646 if ((res_temp.netcontext_flags &
1647 (NET_CONTEXT_FLAG_USE_DNS_OVER_TLS | NET_CONTEXT_FLAG_USE_EDNS)) &&
1648 (res_temp.flags & RES_F_EDNS0ERR)) {
1649 LOG(INFO) << __func__ << ": retry without EDNS0";
1650 n = res_nmkquery(QUERY, name, cl, type, {}, buf, res_temp.netcontext_flags);
1651 n = res_nsend(&res_temp, std::span(buf, n), std::span(t->answer.data(), anslen), &rcode,
1652 0);
1653 }
1654 }
1655
1656 LOG(INFO) << __func__ << ": rcode=" << rcode << ", ancount=" << ntohs(hp->ancount)
1657 << ", return value=" << n;
1658
1659 t->n = n;
1660 return {
1661 .ancount = ntohs(hp->ancount),
1662 .rcode = rcode,
1663 .qerrno = errno,
1664 .event = event,
1665 };
1666 }
1667
1668 } // namespace
1669
1670 // This function runs doQuery() for each res_target in parallel.
1671 // 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)1672 static int res_queryN_parallel(const char* name, res_target* target, ResState* res, int* herrno) {
1673 std::vector<std::future<QueryResult>> results;
1674 results.reserve(2);
1675 std::chrono::milliseconds sleepTimeMs{};
1676 for (res_target* t = target; t; t = t->next) {
1677 results.emplace_back(std::async(std::launch::async, doQuery, name, t, res, sleepTimeMs));
1678 // Avoiding gateways drop packets if queries are sent too close together
1679 // Only needed if we have multiple queries in a row.
1680 if (t->next) {
1681 int sleepFlag = Experiments::getInstance()->getFlag("parallel_lookup_sleep_time",
1682 SLEEP_TIME_MS);
1683 if (sleepFlag > 1000) sleepFlag = 1000;
1684 sleepTimeMs = std::chrono::milliseconds(sleepFlag);
1685 }
1686 }
1687
1688 int ancount = 0;
1689 int rcode = 0;
1690
1691 for (auto& f : results) {
1692 const QueryResult& r = f.get();
1693 if (r.herrno == NO_RECOVERY) {
1694 *herrno = r.herrno;
1695 return -1;
1696 }
1697 res->event->MergeFrom(r.event);
1698 ancount += r.ancount;
1699 rcode = r.rcode;
1700 errno = r.qerrno;
1701 }
1702
1703 if (ancount == 0) {
1704 *herrno = getHerrnoFromRcode(rcode);
1705 return -1;
1706 }
1707
1708 return ancount;
1709 }
1710
1711 /*
1712 * Formulate a normal query, send, and retrieve answer in supplied buffer.
1713 * Return the size of the response on success, -1 on error.
1714 * If enabled, implement search rules until answer or unrecoverable failure
1715 * is detected. Error code, if any, is left in *herrno.
1716 */
res_searchN(const char * name,res_target * target,ResState * res,int * herrno)1717 static int res_searchN(const char* name, res_target* target, ResState* res, int* herrno) {
1718 const char* cp;
1719 HEADER* hp;
1720 uint32_t dots;
1721 int ret, saved_herrno;
1722 int got_nodata = 0, got_servfail = 0, tried_as_is = 0;
1723
1724 assert(name != NULL);
1725 assert(target != NULL);
1726
1727 hp = (HEADER*)(void*)target->answer.data();
1728
1729 errno = 0;
1730 *herrno = HOST_NOT_FOUND; /* default, if we never query */
1731 dots = 0;
1732 for (cp = name; *cp; cp++) dots += (*cp == '.');
1733 const bool trailing_dot = (cp > name && *--cp == '.') ? true : false;
1734
1735 /*
1736 * If there are dots in the name already, let's just give it a try
1737 * 'as is'. The threshold can be set with the "ndots" option.
1738 */
1739 saved_herrno = -1;
1740 if (dots >= res->ndots) {
1741 ret = res_querydomainN(name, NULL, target, res, herrno);
1742 if (ret > 0) return (ret);
1743 saved_herrno = *herrno;
1744 tried_as_is++;
1745 }
1746
1747 /*
1748 * We do at least one level of search if
1749 * - there is no dot, or
1750 * - there is at least one dot and there is no trailing dot.
1751 * - this is not a .local mDNS lookup.
1752 */
1753 if ((!dots || (dots && !trailing_dot)) && !isMdnsResolution(res->flags)) {
1754 /* Unfortunately we need to set stuff up before
1755 * the domain stuff is tried. Will have a better
1756 * fix after thread pools are used.
1757 */
1758 resolv_populate_res_for_net(res);
1759
1760 for (const auto& domain : res->search_domains) {
1761 ret = res_querydomainN(name, domain.c_str(), target, res, herrno);
1762 if (ret > 0) return ret;
1763
1764 /*
1765 * If no server present, give up.
1766 * If name isn't found in this domain,
1767 * keep trying higher domains in the search list
1768 * (if that's enabled).
1769 * On a NO_DATA error, keep trying, otherwise
1770 * a wildcard entry of another type could keep us
1771 * from finding this entry higher in the domain.
1772 * If we get some other error (negative answer or
1773 * server failure), then stop searching up,
1774 * but try the input name below in case it's
1775 * fully-qualified.
1776 */
1777 if (errno == ECONNREFUSED) {
1778 *herrno = TRY_AGAIN;
1779 return -1;
1780 }
1781
1782 switch (*herrno) {
1783 case NO_DATA:
1784 got_nodata++;
1785 [[fallthrough]];
1786 case HOST_NOT_FOUND:
1787 /* keep trying */
1788 break;
1789 case TRY_AGAIN:
1790 if (hp->rcode == SERVFAIL) {
1791 /* try next search element, if any */
1792 got_servfail++;
1793 }
1794 break;
1795 }
1796 }
1797 }
1798
1799 /*
1800 * if we have not already tried the name "as is", do that now.
1801 * note that we do this regardless of how many dots were in the
1802 * name or whether it ends with a dot.
1803 */
1804 if (!tried_as_is) {
1805 ret = res_querydomainN(name, NULL, target, res, herrno);
1806 if (ret > 0) return ret;
1807 }
1808
1809 /*
1810 * if we got here, we didn't satisfy the search.
1811 * if we did an initial full query, return that query's h_errno
1812 * (note that we wouldn't be here if that query had succeeded).
1813 * else if we ever got a nodata, send that back as the reason.
1814 * else send back meaningless h_errno, that being the one from
1815 * the last DNSRCH we did.
1816 */
1817 if (saved_herrno != -1)
1818 *herrno = saved_herrno;
1819 else if (got_nodata)
1820 *herrno = NO_DATA;
1821 else if (got_servfail)
1822 *herrno = TRY_AGAIN;
1823 return -1;
1824 }
1825
1826 // Perform a call on res_query on the concatenation of name and domain,
1827 // 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)1828 static int res_querydomainN(const char* name, const char* domain, res_target* target, ResState* res,
1829 int* herrno) {
1830 char nbuf[MAXDNAME];
1831 const char* longname = nbuf;
1832 size_t n, d;
1833
1834 assert(name != NULL);
1835
1836 if (domain == NULL) {
1837 // Check for trailing '.'; copy without '.' if present.
1838 n = strlen(name);
1839 if (n + 1 > sizeof(nbuf)) {
1840 *herrno = NO_RECOVERY;
1841 return -1;
1842 }
1843 if (n > 0 && name[--n] == '.') {
1844 strncpy(nbuf, name, n);
1845 nbuf[n] = '\0';
1846 } else
1847 longname = name;
1848 } else {
1849 n = strlen(name);
1850 d = strlen(domain);
1851 if (n + 1 + d + 1 > sizeof(nbuf)) {
1852 *herrno = NO_RECOVERY;
1853 return -1;
1854 }
1855 snprintf(nbuf, sizeof(nbuf), "%s.%s", name, domain);
1856 }
1857 return res_queryN_parallel(longname, target, res, herrno);
1858 }
1859