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 <errno.h>
42 #include <fcntl.h>
43 #include <net/if.h>
44 #include <netdb.h>
45 #include <netinet/in.h>
46 #include <stdbool.h>
47 #include <stddef.h>
48 #include <stdlib.h>
49 #include <string.h>
50 #include <sys/param.h>
51 #include <sys/socket.h>
52 #include <sys/stat.h>
53 #include <sys/un.h>
54 #include <unistd.h>
55
56 #include <chrono>
57 #include <future>
58
59 #include <android-base/logging.h>
60
61 #include "Experiments.h"
62 #include "netd_resolv/resolv.h"
63 #include "res_comp.h"
64 #include "res_debug.h"
65 #include "res_init.h"
66 #include "resolv_cache.h"
67 #include "resolv_private.h"
68 #include "util.h"
69
70 #define ANY 0
71
72 using android::net::NetworkDnsEventReported;
73
74 const char in_addrany[] = {0, 0, 0, 0};
75 const char in_loopback[] = {127, 0, 0, 1};
76 const char in6_addrany[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
77 const char in6_loopback[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1};
78
79 const struct afd {
80 int a_af;
81 int a_addrlen;
82 int a_socklen;
83 int a_off;
84 const char* a_addrany;
85 const char* a_loopback;
86 int a_scoped;
87 } afdl[] = {
88 {PF_INET6, sizeof(struct in6_addr), sizeof(struct sockaddr_in6),
89 offsetof(struct sockaddr_in6, sin6_addr), in6_addrany, in6_loopback, 1},
90 {PF_INET, sizeof(struct in_addr), sizeof(struct sockaddr_in),
91 offsetof(struct sockaddr_in, sin_addr), in_addrany, in_loopback, 0},
92 {0, 0, 0, 0, NULL, NULL, 0},
93 };
94
95 struct Explore {
96 int e_af;
97 int e_socktype;
98 int e_protocol;
99 int e_wild;
100 #define WILD_AF(ex) ((ex).e_wild & 0x01)
101 #define WILD_SOCKTYPE(ex) ((ex).e_wild & 0x02)
102 #define WILD_PROTOCOL(ex) ((ex).e_wild & 0x04)
103 };
104
105 const Explore explore_options[] = {
106 {PF_INET6, SOCK_DGRAM, IPPROTO_UDP, 0x07},
107 {PF_INET6, SOCK_STREAM, IPPROTO_TCP, 0x07},
108 {PF_INET6, SOCK_RAW, ANY, 0x05},
109 {PF_INET, SOCK_DGRAM, IPPROTO_UDP, 0x07},
110 {PF_INET, SOCK_STREAM, IPPROTO_TCP, 0x07},
111 {PF_INET, SOCK_RAW, ANY, 0x05},
112 {PF_UNSPEC, SOCK_DGRAM, IPPROTO_UDP, 0x07},
113 {PF_UNSPEC, SOCK_STREAM, IPPROTO_TCP, 0x07},
114 {PF_UNSPEC, SOCK_RAW, ANY, 0x05},
115 };
116
117 #define PTON_MAX 16
118
119 struct res_target {
120 struct res_target* next;
121 const char* name; // domain name
122 int qclass, qtype; // class and type of query
123 std::vector<uint8_t> answer = std::vector<uint8_t>(MAXPACKET, 0); // buffer to put answer
124 int n = 0; // result length
125 };
126
127 static int str2number(const char*);
128 static int explore_fqdn(const struct addrinfo*, const char*, const char*, struct addrinfo**,
129 const struct android_net_context*, NetworkDnsEventReported* event);
130 static int explore_null(const struct addrinfo*, const char*, struct addrinfo**);
131 static int explore_numeric(const struct addrinfo*, const char*, const char*, struct addrinfo**,
132 const char*);
133 static int explore_numeric_scope(const struct addrinfo*, const char*, const char*,
134 struct addrinfo**);
135 static int get_canonname(const struct addrinfo*, struct addrinfo*, const char*);
136 static struct addrinfo* get_ai(const struct addrinfo*, const struct afd*, const char*);
137 static int get_portmatch(const struct addrinfo*, const char*);
138 static int get_port(const struct addrinfo*, const char*, int);
139 static const struct afd* find_afd(int);
140 static int ip6_str2scopeid(const char*, struct sockaddr_in6*, uint32_t*);
141
142 static struct addrinfo* getanswer(const std::vector<uint8_t>&, int, const char*, int,
143 const struct addrinfo*, int* herrno);
144 static int dns_getaddrinfo(const char* name, const addrinfo* pai,
145 const android_net_context* netcontext, addrinfo** rv,
146 NetworkDnsEventReported* event);
147 static void _sethtent(FILE**);
148 static void _endhtent(FILE**);
149 static struct addrinfo* _gethtent(FILE**, const char*, const struct addrinfo*);
150 static struct addrinfo* getCustomHosts(const size_t netid, const char*, const struct addrinfo*);
151 static bool files_getaddrinfo(const size_t netid, const char* name, const addrinfo* pai,
152 addrinfo** res);
153 static int _find_src_addr(const struct sockaddr*, struct sockaddr*, unsigned, uid_t);
154
155 static int res_queryN(const char* name, res_target* target, res_state res, int* herrno);
156 static int res_searchN(const char* name, res_target* target, res_state res, int* herrno);
157 static int res_querydomainN(const char* name, const char* domain, res_target* target, res_state res,
158 int* herrno);
159
160 const char* const ai_errlist[] = {
161 "Success",
162 "Address family for hostname not supported", /* EAI_ADDRFAMILY */
163 "Temporary failure in name resolution", /* EAI_AGAIN */
164 "Invalid value for ai_flags", /* EAI_BADFLAGS */
165 "Non-recoverable failure in name resolution", /* EAI_FAIL */
166 "ai_family not supported", /* EAI_FAMILY */
167 "Memory allocation failure", /* EAI_MEMORY */
168 "No address associated with hostname", /* EAI_NODATA */
169 "hostname nor servname provided, or not known", /* EAI_NONAME */
170 "servname not supported for ai_socktype", /* EAI_SERVICE */
171 "ai_socktype not supported", /* EAI_SOCKTYPE */
172 "System error returned in errno", /* EAI_SYSTEM */
173 "Invalid value for hints", /* EAI_BADHINTS */
174 "Resolved protocol is unknown", /* EAI_PROTOCOL */
175 "Argument buffer overflow", /* EAI_OVERFLOW */
176 "Unknown error", /* EAI_MAX */
177 };
178
179 /* XXX macros that make external reference is BAD. */
180
181 #define GET_AI(ai, afd, addr) \
182 do { \
183 /* external reference: pai, error, and label free */ \
184 (ai) = get_ai(pai, (afd), (addr)); \
185 if ((ai) == NULL) { \
186 error = EAI_MEMORY; \
187 goto free; \
188 } \
189 } while (0)
190
191 #define GET_PORT(ai, serv) \
192 do { \
193 /* external reference: error and label free */ \
194 error = get_port((ai), (serv), 0); \
195 if (error != 0) goto free; \
196 } while (0)
197
198 #define MATCH_FAMILY(x, y, w) \
199 ((x) == (y) || ((w) && ((x) == PF_UNSPEC || (y) == PF_UNSPEC)))
200 #define MATCH(x, y, w) ((x) == (y) || ((w) && ((x) == ANY || (y) == ANY)))
201
gai_strerror(int ecode)202 const char* gai_strerror(int ecode) {
203 if (ecode < 0 || ecode > EAI_MAX) ecode = EAI_MAX;
204 return ai_errlist[ecode];
205 }
206
freeaddrinfo(struct addrinfo * ai)207 void freeaddrinfo(struct addrinfo* ai) {
208 while (ai) {
209 struct addrinfo* next = ai->ai_next;
210 if (ai->ai_canonname) free(ai->ai_canonname);
211 // Also frees ai->ai_addr which points to extra space beyond addrinfo
212 free(ai);
213 ai = next;
214 }
215 }
216
str2number(const char * p)217 static int str2number(const char* p) {
218 char* ep;
219 unsigned long v;
220
221 assert(p != NULL);
222
223 if (*p == '\0') return -1;
224 ep = NULL;
225 errno = 0;
226 v = strtoul(p, &ep, 10);
227 if (errno == 0 && ep && *ep == '\0' && v <= UINT_MAX)
228 return v;
229 else
230 return -1;
231 }
232
233 /*
234 * The following functions determine whether IPv4 or IPv6 connectivity is
235 * available in order to implement AI_ADDRCONFIG.
236 *
237 * Strictly speaking, AI_ADDRCONFIG should not look at whether connectivity is
238 * available, but whether addresses of the specified family are "configured
239 * on the local system". However, bionic doesn't currently support getifaddrs,
240 * so checking for connectivity is the next best thing.
241 */
have_ipv6(unsigned mark,uid_t uid)242 static int have_ipv6(unsigned mark, uid_t uid) {
243 static const struct sockaddr_in6 sin6_test = {
244 .sin6_family = AF_INET6,
245 .sin6_addr.s6_addr = {// 2000::
246 0x20, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}};
247 sockaddr_union addr = {.sin6 = sin6_test};
248 return _find_src_addr(&addr.sa, NULL, mark, uid) == 1;
249 }
250
have_ipv4(unsigned mark,uid_t uid)251 static int have_ipv4(unsigned mark, uid_t uid) {
252 static const struct sockaddr_in sin_test = {
253 .sin_family = AF_INET,
254 .sin_addr.s_addr = __constant_htonl(0x08080808L) // 8.8.8.8
255 };
256 sockaddr_union addr = {.sin = sin_test};
257 return _find_src_addr(&addr.sa, NULL, mark, uid) == 1;
258 }
259
260 // Internal version of getaddrinfo(), but limited to AI_NUMERICHOST.
261 // NOTE: also called by resolv_set_nameservers().
getaddrinfo_numeric(const char * hostname,const char * servname,addrinfo hints,addrinfo ** result)262 int getaddrinfo_numeric(const char* hostname, const char* servname, addrinfo hints,
263 addrinfo** result) {
264 hints.ai_flags = AI_NUMERICHOST;
265 const android_net_context netcontext = {
266 .app_netid = NETID_UNSET,
267 .app_mark = MARK_UNSET,
268 .dns_netid = NETID_UNSET,
269 .dns_mark = MARK_UNSET,
270 .uid = NET_CONTEXT_INVALID_UID,
271 .pid = NET_CONTEXT_INVALID_PID,
272 };
273 NetworkDnsEventReported event;
274 return android_getaddrinfofornetcontext(hostname, servname, &hints, &netcontext, result,
275 &event);
276 }
277
278 namespace {
279
validateHints(const addrinfo * _Nonnull hints)280 int validateHints(const addrinfo* _Nonnull hints) {
281 if (!hints) return EAI_BADHINTS;
282
283 // error check for hints
284 if (hints->ai_addrlen || hints->ai_canonname || hints->ai_addr || hints->ai_next) {
285 return EAI_BADHINTS;
286 }
287 if (hints->ai_flags & ~AI_MASK) {
288 return EAI_BADFLAGS;
289 }
290 if (!(hints->ai_family == PF_UNSPEC || hints->ai_family == PF_INET ||
291 hints->ai_family == PF_INET6)) {
292 return EAI_FAMILY;
293 }
294
295 // Socket types which are not in explore_options.
296 switch (hints->ai_socktype) {
297 case SOCK_RAW:
298 case SOCK_DGRAM:
299 case SOCK_STREAM:
300 case ANY:
301 break;
302 default:
303 return EAI_SOCKTYPE;
304 }
305
306 if (hints->ai_socktype == ANY || hints->ai_protocol == ANY) return 0;
307
308 // if both socktype/protocol are specified, check if they are meaningful combination.
309 for (const Explore& ex : explore_options) {
310 if (hints->ai_family != ex.e_af) continue;
311 if (ex.e_socktype == ANY) continue;
312 if (ex.e_protocol == ANY) continue;
313 if (hints->ai_socktype == ex.e_socktype && hints->ai_protocol != ex.e_protocol) {
314 return EAI_BADHINTS;
315 }
316 }
317
318 return 0;
319 }
320
321 } // namespace
322
android_getaddrinfofornetcontext(const char * hostname,const char * servname,const addrinfo * hints,const android_net_context * netcontext,addrinfo ** res,NetworkDnsEventReported * event)323 int android_getaddrinfofornetcontext(const char* hostname, const char* servname,
324 const addrinfo* hints, const android_net_context* netcontext,
325 addrinfo** res, NetworkDnsEventReported* event) {
326 // hostname is allowed to be nullptr
327 // servname is allowed to be nullptr
328 // hints is allowed to be nullptr
329 assert(res != nullptr);
330 assert(netcontext != nullptr);
331 assert(event != nullptr);
332
333 addrinfo sentinel = {};
334 addrinfo* cur = &sentinel;
335 int error = 0;
336
337 do {
338 if (hostname == nullptr && servname == nullptr) {
339 error = EAI_NONAME;
340 break;
341 }
342
343 if (hints && (error = validateHints(hints))) break;
344 addrinfo ai = hints ? *hints : addrinfo{};
345
346 // Check for special cases:
347 // (1) numeric servname is disallowed if socktype/protocol are left unspecified.
348 // (2) servname is disallowed for raw and other inet{,6} sockets.
349 if (MATCH_FAMILY(ai.ai_family, PF_INET, 1) || MATCH_FAMILY(ai.ai_family, PF_INET6, 1)) {
350 addrinfo tmp = ai;
351 if (tmp.ai_family == PF_UNSPEC) {
352 tmp.ai_family = PF_INET6;
353 }
354 error = get_portmatch(&tmp, servname);
355 if (error) break;
356 }
357
358 // NULL hostname, or numeric hostname
359 for (const Explore& ex : explore_options) {
360 /* PF_UNSPEC entries are prepared for DNS queries only */
361 if (ex.e_af == PF_UNSPEC) continue;
362
363 if (!MATCH_FAMILY(ai.ai_family, ex.e_af, WILD_AF(ex))) continue;
364 if (!MATCH(ai.ai_socktype, ex.e_socktype, WILD_SOCKTYPE(ex))) continue;
365 if (!MATCH(ai.ai_protocol, ex.e_protocol, WILD_PROTOCOL(ex))) continue;
366
367 addrinfo tmp = ai;
368 if (tmp.ai_family == PF_UNSPEC) tmp.ai_family = ex.e_af;
369 if (tmp.ai_socktype == ANY && ex.e_socktype != ANY) tmp.ai_socktype = ex.e_socktype;
370 if (tmp.ai_protocol == ANY && ex.e_protocol != ANY) tmp.ai_protocol = ex.e_protocol;
371
372 LOG(DEBUG) << __func__ << ": explore_numeric: ai_family=" << tmp.ai_family
373 << " ai_socktype=" << tmp.ai_socktype << " ai_protocol=" << tmp.ai_protocol;
374 if (hostname == nullptr)
375 error = explore_null(&tmp, servname, &cur->ai_next);
376 else
377 error = explore_numeric_scope(&tmp, hostname, servname, &cur->ai_next);
378
379 if (error) break;
380
381 while (cur->ai_next) cur = cur->ai_next;
382 }
383 if (error) break;
384
385 // If numeric representation of AF1 can be interpreted as FQDN
386 // representation of AF2, we need to think again about the code below.
387 if (sentinel.ai_next) break;
388
389 if (hostname == nullptr) {
390 error = EAI_NODATA;
391 break;
392 }
393 if (ai.ai_flags & AI_NUMERICHOST) {
394 error = EAI_NONAME;
395 break;
396 }
397
398 return resolv_getaddrinfo(hostname, servname, hints, netcontext, res, event);
399 } while (0);
400
401 if (error) {
402 freeaddrinfo(sentinel.ai_next);
403 *res = nullptr;
404 } else {
405 *res = sentinel.ai_next;
406 }
407 return error;
408 }
409
resolv_getaddrinfo(const char * _Nonnull hostname,const char * servname,const addrinfo * hints,const android_net_context * _Nonnull netcontext,addrinfo ** _Nonnull res,NetworkDnsEventReported * _Nonnull event)410 int resolv_getaddrinfo(const char* _Nonnull hostname, const char* servname, const addrinfo* hints,
411 const android_net_context* _Nonnull netcontext, addrinfo** _Nonnull res,
412 NetworkDnsEventReported* _Nonnull event) {
413 if (hostname == nullptr && servname == nullptr) return EAI_NONAME;
414 if (hostname == nullptr) return EAI_NODATA;
415
416 // servname is allowed to be nullptr
417 // hints is allowed to be nullptr
418 assert(res != nullptr);
419 assert(netcontext != nullptr);
420 assert(event != nullptr);
421
422 int error = EAI_FAIL;
423 if (hints && (error = validateHints(hints))) {
424 *res = nullptr;
425 return error;
426 }
427
428 addrinfo ai = hints ? *hints : addrinfo{};
429 addrinfo sentinel = {};
430 addrinfo* cur = &sentinel;
431 // hostname as alphanumeric name.
432 // We would like to prefer AF_INET6 over AF_INET, so we'll make a outer loop by AFs.
433 for (const Explore& ex : explore_options) {
434 // Require exact match for family field
435 if (ai.ai_family != ex.e_af) continue;
436
437 if (!MATCH(ai.ai_socktype, ex.e_socktype, WILD_SOCKTYPE(ex))) continue;
438
439 if (!MATCH(ai.ai_protocol, ex.e_protocol, WILD_PROTOCOL(ex))) continue;
440
441 addrinfo tmp = ai;
442 if (tmp.ai_socktype == ANY && ex.e_socktype != ANY) tmp.ai_socktype = ex.e_socktype;
443 if (tmp.ai_protocol == ANY && ex.e_protocol != ANY) tmp.ai_protocol = ex.e_protocol;
444
445 LOG(DEBUG) << __func__ << ": explore_fqdn(): ai_family=" << tmp.ai_family
446 << " ai_socktype=" << tmp.ai_socktype << " ai_protocol=" << tmp.ai_protocol;
447 error = explore_fqdn(&tmp, hostname, servname, &cur->ai_next, netcontext, event);
448
449 while (cur->ai_next) cur = cur->ai_next;
450 }
451
452 // Propagate the last error from explore_fqdn(), but only when *all* attempts failed.
453 if ((*res = sentinel.ai_next)) return 0;
454
455 // TODO: consider removing freeaddrinfo.
456 freeaddrinfo(sentinel.ai_next);
457 *res = nullptr;
458 return (error == 0) ? EAI_FAIL : error;
459 }
460
461 // FQDN hostname, DNS lookup
explore_fqdn(const addrinfo * pai,const char * hostname,const char * servname,addrinfo ** res,const android_net_context * netcontext,NetworkDnsEventReported * event)462 static int explore_fqdn(const addrinfo* pai, const char* hostname, const char* servname,
463 addrinfo** res, const android_net_context* netcontext,
464 NetworkDnsEventReported* event) {
465 assert(pai != nullptr);
466 // hostname may be nullptr
467 // servname may be nullptr
468 assert(res != nullptr);
469
470 addrinfo* result = nullptr;
471 int error = 0;
472
473 // If the servname does not match socktype/protocol, return error code.
474 if ((error = get_portmatch(pai, servname))) return error;
475
476 if (!files_getaddrinfo(netcontext->dns_netid, hostname, pai, &result)) {
477 error = dns_getaddrinfo(hostname, pai, netcontext, &result, event);
478 }
479 if (error) {
480 freeaddrinfo(result);
481 return error;
482 }
483
484 for (addrinfo* cur = result; cur; cur = cur->ai_next) {
485 // canonname should be filled already
486 if ((error = get_port(cur, servname, 0))) {
487 freeaddrinfo(result);
488 return error;
489 }
490 }
491 *res = result;
492 return 0;
493 }
494
495 /*
496 * hostname == NULL.
497 * passive socket -> anyaddr (0.0.0.0 or ::)
498 * non-passive socket -> localhost (127.0.0.1 or ::1)
499 */
explore_null(const struct addrinfo * pai,const char * servname,struct addrinfo ** res)500 static int explore_null(const struct addrinfo* pai, const char* servname, struct addrinfo** res) {
501 int s;
502 const struct afd* afd;
503 struct addrinfo* cur;
504 struct addrinfo sentinel;
505 int error;
506
507 LOG(DEBUG) << __func__;
508
509 assert(pai != NULL);
510 /* servname may be NULL */
511 assert(res != NULL);
512
513 *res = NULL;
514 sentinel.ai_next = NULL;
515 cur = &sentinel;
516
517 /*
518 * filter out AFs that are not supported by the kernel
519 * XXX errno?
520 */
521 s = socket(pai->ai_family, SOCK_DGRAM | SOCK_CLOEXEC, 0);
522 if (s < 0) {
523 if (errno != EMFILE) return 0;
524 } else
525 close(s);
526
527 /*
528 * if the servname does not match socktype/protocol, ignore it.
529 */
530 if (get_portmatch(pai, servname) != 0) return 0;
531
532 afd = find_afd(pai->ai_family);
533 if (afd == NULL) return 0;
534
535 if (pai->ai_flags & AI_PASSIVE) {
536 GET_AI(cur->ai_next, afd, afd->a_addrany);
537 GET_PORT(cur->ai_next, servname);
538 } else {
539 GET_AI(cur->ai_next, afd, afd->a_loopback);
540 GET_PORT(cur->ai_next, servname);
541 }
542 cur = cur->ai_next;
543
544 *res = sentinel.ai_next;
545 return 0;
546
547 free:
548 freeaddrinfo(sentinel.ai_next);
549 return error;
550 }
551
552 /*
553 * numeric hostname
554 */
explore_numeric(const struct addrinfo * pai,const char * hostname,const char * servname,struct addrinfo ** res,const char * canonname)555 static int explore_numeric(const struct addrinfo* pai, const char* hostname, const char* servname,
556 struct addrinfo** res, const char* canonname) {
557 const struct afd* afd;
558 struct addrinfo* cur;
559 struct addrinfo sentinel;
560 int error;
561 char pton[PTON_MAX];
562
563 assert(pai != NULL);
564 /* hostname may be NULL */
565 /* servname may be NULL */
566 assert(res != NULL);
567
568 *res = NULL;
569 sentinel.ai_next = NULL;
570 cur = &sentinel;
571
572 /*
573 * if the servname does not match socktype/protocol, ignore it.
574 */
575 if (get_portmatch(pai, servname) != 0) return 0;
576
577 afd = find_afd(pai->ai_family);
578 if (afd == NULL) return 0;
579
580 if (inet_pton(afd->a_af, hostname, pton) == 1) {
581 if (pai->ai_family == afd->a_af || pai->ai_family == PF_UNSPEC /*?*/) {
582 GET_AI(cur->ai_next, afd, pton);
583 GET_PORT(cur->ai_next, servname);
584 if ((pai->ai_flags & AI_CANONNAME)) {
585 /*
586 * Set the numeric address itself as
587 * the canonical name, based on a
588 * clarification in rfc2553bis-03.
589 */
590 error = get_canonname(pai, cur->ai_next, canonname);
591 if (error != 0) {
592 freeaddrinfo(sentinel.ai_next);
593 return error;
594 }
595 }
596 while (cur->ai_next) cur = cur->ai_next;
597 } else
598 return EAI_FAMILY;
599 }
600
601 *res = sentinel.ai_next;
602 return 0;
603
604 free:
605 freeaddrinfo(sentinel.ai_next);
606 return error;
607 }
608
609 /*
610 * numeric hostname with scope
611 */
explore_numeric_scope(const struct addrinfo * pai,const char * hostname,const char * servname,struct addrinfo ** res)612 static int explore_numeric_scope(const struct addrinfo* pai, const char* hostname,
613 const char* servname, struct addrinfo** res) {
614 const struct afd* afd;
615 struct addrinfo* cur;
616 int error;
617 const char *cp, *scope, *addr;
618 struct sockaddr_in6* sin6;
619
620 LOG(DEBUG) << __func__;
621
622 assert(pai != NULL);
623 /* hostname may be NULL */
624 /* servname may be NULL */
625 assert(res != NULL);
626
627 /*
628 * if the servname does not match socktype/protocol, ignore it.
629 */
630 if (get_portmatch(pai, servname) != 0) return 0;
631
632 afd = find_afd(pai->ai_family);
633 if (afd == NULL) return 0;
634
635 if (!afd->a_scoped) return explore_numeric(pai, hostname, servname, res, hostname);
636
637 cp = strchr(hostname, SCOPE_DELIMITER);
638 if (cp == NULL) return explore_numeric(pai, hostname, servname, res, hostname);
639
640 /*
641 * Handle special case of <scoped_address><delimiter><scope id>
642 */
643 char* hostname2 = strdup(hostname);
644 if (hostname2 == NULL) return EAI_MEMORY;
645 /* terminate at the delimiter */
646 hostname2[cp - hostname] = '\0';
647 addr = hostname2;
648 scope = cp + 1;
649
650 error = explore_numeric(pai, addr, servname, res, hostname);
651 if (error == 0) {
652 uint32_t scopeid;
653
654 for (cur = *res; cur; cur = cur->ai_next) {
655 if (cur->ai_family != AF_INET6) continue;
656 sin6 = (struct sockaddr_in6*) (void*) cur->ai_addr;
657 if (ip6_str2scopeid(scope, sin6, &scopeid) == -1) {
658 free(hostname2);
659 return (EAI_NODATA); /* XXX: is return OK? */
660 }
661 sin6->sin6_scope_id = scopeid;
662 }
663 }
664
665 free(hostname2);
666
667 return error;
668 }
669
get_canonname(const struct addrinfo * pai,struct addrinfo * ai,const char * str)670 static int get_canonname(const struct addrinfo* pai, struct addrinfo* ai, const char* str) {
671 assert(pai != NULL);
672 assert(ai != NULL);
673 assert(str != NULL);
674
675 if ((pai->ai_flags & AI_CANONNAME) != 0) {
676 ai->ai_canonname = strdup(str);
677 if (ai->ai_canonname == NULL) return EAI_MEMORY;
678 }
679 return 0;
680 }
681
get_ai(const struct addrinfo * pai,const struct afd * afd,const char * addr)682 static struct addrinfo* get_ai(const struct addrinfo* pai, const struct afd* afd,
683 const char* addr) {
684 char* p;
685 struct addrinfo* ai;
686
687 assert(pai != NULL);
688 assert(afd != NULL);
689 assert(addr != NULL);
690
691 ai = (struct addrinfo*) malloc(sizeof(struct addrinfo) + sizeof(sockaddr_union));
692 if (ai == NULL) return NULL;
693
694 memcpy(ai, pai, sizeof(struct addrinfo));
695 ai->ai_addr = (struct sockaddr*) (void*) (ai + 1);
696 memset(ai->ai_addr, 0, sizeof(sockaddr_union));
697
698 ai->ai_addrlen = afd->a_socklen;
699 ai->ai_addr->sa_family = ai->ai_family = afd->a_af;
700 p = (char*) (void*) (ai->ai_addr);
701 memcpy(p + afd->a_off, addr, (size_t) afd->a_addrlen);
702 return ai;
703 }
704
get_portmatch(const struct addrinfo * ai,const char * servname)705 static int get_portmatch(const struct addrinfo* ai, const char* servname) {
706 assert(ai != NULL);
707 /* servname may be NULL */
708
709 return get_port(ai, servname, 1);
710 }
711
get_port(const struct addrinfo * ai,const char * servname,int matchonly)712 static int get_port(const struct addrinfo* ai, const char* servname, int matchonly) {
713 const char* proto;
714 struct servent* sp;
715 int port;
716 int allownumeric;
717
718 assert(ai != NULL);
719 /* servname may be NULL */
720
721 if (servname == NULL) return 0;
722 switch (ai->ai_family) {
723 case AF_INET:
724 case AF_INET6:
725 break;
726 default:
727 return 0;
728 }
729
730 switch (ai->ai_socktype) {
731 case SOCK_RAW:
732 return EAI_SERVICE;
733 case SOCK_DGRAM:
734 case SOCK_STREAM:
735 case ANY:
736 allownumeric = 1;
737 break;
738 default:
739 return EAI_SOCKTYPE;
740 }
741
742 port = str2number(servname);
743 if (port >= 0) {
744 if (!allownumeric) return EAI_SERVICE;
745 if (port < 0 || port > 65535) return EAI_SERVICE;
746 port = htons(port);
747 } else {
748 if (ai->ai_flags & AI_NUMERICSERV) return EAI_NONAME;
749
750 switch (ai->ai_socktype) {
751 case SOCK_DGRAM:
752 proto = "udp";
753 break;
754 case SOCK_STREAM:
755 proto = "tcp";
756 break;
757 default:
758 proto = NULL;
759 break;
760 }
761
762 if ((sp = getservbyname(servname, proto)) == NULL) return EAI_SERVICE;
763 port = sp->s_port;
764 }
765
766 if (!matchonly) {
767 switch (ai->ai_family) {
768 case AF_INET:
769 ((struct sockaddr_in*) (void*) ai->ai_addr)->sin_port = port;
770 break;
771 case AF_INET6:
772 ((struct sockaddr_in6*) (void*) ai->ai_addr)->sin6_port = port;
773 break;
774 }
775 }
776
777 return 0;
778 }
779
find_afd(int af)780 static const struct afd* find_afd(int af) {
781 const struct afd* afd;
782
783 if (af == PF_UNSPEC) return NULL;
784 for (afd = afdl; afd->a_af; afd++) {
785 if (afd->a_af == af) return afd;
786 }
787 return NULL;
788 }
789
790 // Convert a string to a scope identifier.
ip6_str2scopeid(const char * scope,struct sockaddr_in6 * sin6,uint32_t * scopeid)791 static int ip6_str2scopeid(const char* scope, struct sockaddr_in6* sin6, uint32_t* scopeid) {
792 uint64_t lscopeid;
793 struct in6_addr* a6;
794 char* ep;
795
796 assert(scope != NULL);
797 assert(sin6 != NULL);
798 assert(scopeid != NULL);
799
800 a6 = &sin6->sin6_addr;
801
802 /* empty scopeid portion is invalid */
803 if (*scope == '\0') return -1;
804
805 if (IN6_IS_ADDR_LINKLOCAL(a6) || IN6_IS_ADDR_MC_LINKLOCAL(a6)) {
806 /*
807 * We currently assume a one-to-one mapping between links
808 * and interfaces, so we simply use interface indices for
809 * like-local scopes.
810 */
811 *scopeid = if_nametoindex(scope);
812 if (*scopeid != 0) return 0;
813 }
814
815 // try to convert to a numeric id as a last resort
816 errno = 0;
817 lscopeid = strtoul(scope, &ep, 10);
818 *scopeid = (uint32_t)(lscopeid & 0xffffffffUL);
819 if (errno == 0 && ep && *ep == '\0' && *scopeid == lscopeid)
820 return 0;
821 else
822 return -1;
823 }
824
825 /* code duplicate with gethnamaddr.c */
826
827 #define BOUNDED_INCR(x) \
828 do { \
829 BOUNDS_CHECK(cp, x); \
830 cp += (x); \
831 } while (0)
832
833 #define BOUNDS_CHECK(ptr, count) \
834 do { \
835 if (eom - (ptr) < (count)) { \
836 *herrno = NO_RECOVERY; \
837 return NULL; \
838 } \
839 } while (0)
840
getanswer(const std::vector<uint8_t> & answer,int anslen,const char * qname,int qtype,const struct addrinfo * pai,int * herrno)841 static struct addrinfo* getanswer(const std::vector<uint8_t>& answer, int anslen, const char* qname,
842 int qtype, const struct addrinfo* pai, int* herrno) {
843 struct addrinfo sentinel = {};
844 struct addrinfo *cur;
845 struct addrinfo ai;
846 const struct afd* afd;
847 char* canonname;
848 const HEADER* hp;
849 const uint8_t* cp;
850 int n;
851 const uint8_t* eom;
852 char *bp, *ep;
853 int type, ancount, qdcount;
854 int haveanswer, had_error;
855 char tbuf[MAXDNAME];
856 char hostbuf[8 * 1024];
857
858 assert(qname != NULL);
859 assert(pai != NULL);
860
861 cur = &sentinel;
862
863 canonname = NULL;
864 eom = answer.data() + anslen;
865
866 bool (*name_ok)(const char* dn);
867 switch (qtype) {
868 case T_A:
869 case T_AAAA:
870 case T_ANY: /*use T_ANY only for T_A/T_AAAA lookup*/
871 name_ok = res_hnok;
872 break;
873 default:
874 return NULL; /* XXX should be abort(); */
875 }
876 /*
877 * find first satisfactory answer
878 */
879 hp = reinterpret_cast<const HEADER*>(answer.data());
880 ancount = ntohs(hp->ancount);
881 qdcount = ntohs(hp->qdcount);
882 bp = hostbuf;
883 ep = hostbuf + sizeof hostbuf;
884 cp = answer.data();
885 BOUNDED_INCR(HFIXEDSZ);
886 if (qdcount != 1) {
887 *herrno = NO_RECOVERY;
888 return (NULL);
889 }
890 n = dn_expand(answer.data(), eom, cp, bp, ep - bp);
891 if ((n < 0) || !(*name_ok)(bp)) {
892 *herrno = NO_RECOVERY;
893 return (NULL);
894 }
895 BOUNDED_INCR(n + QFIXEDSZ);
896 if (qtype == T_A || qtype == T_AAAA || qtype == T_ANY) {
897 /* res_send() has already verified that the query name is the
898 * same as the one we sent; this just gets the expanded name
899 * (i.e., with the succeeding search-domain tacked on).
900 */
901 n = strlen(bp) + 1; /* for the \0 */
902 if (n >= MAXHOSTNAMELEN) {
903 *herrno = NO_RECOVERY;
904 return (NULL);
905 }
906 canonname = bp;
907 bp += n;
908 /* The qname can be abbreviated, but h_name is now absolute. */
909 qname = canonname;
910 }
911 haveanswer = 0;
912 had_error = 0;
913 while (ancount-- > 0 && cp < eom && !had_error) {
914 n = dn_expand(answer.data(), eom, cp, bp, ep - bp);
915 if ((n < 0) || !(*name_ok)(bp)) {
916 had_error++;
917 continue;
918 }
919 cp += n; /* name */
920 BOUNDS_CHECK(cp, 3 * INT16SZ + INT32SZ);
921 type = ntohs(*reinterpret_cast<const uint16_t*>(cp));
922 cp += INT16SZ; /* type */
923 int cl = ntohs(*reinterpret_cast<const uint16_t*>(cp));
924 cp += INT16SZ + INT32SZ; /* class, TTL */
925 n = ntohs(*reinterpret_cast<const uint16_t*>(cp));
926 cp += INT16SZ; /* len */
927 BOUNDS_CHECK(cp, n);
928 if (cl != C_IN) {
929 /* XXX - debug? syslog? */
930 cp += n;
931 continue; /* XXX - had_error++ ? */
932 }
933 if ((qtype == T_A || qtype == T_AAAA || qtype == T_ANY) && type == T_CNAME) {
934 n = dn_expand(answer.data(), eom, cp, tbuf, sizeof tbuf);
935 if ((n < 0) || !(*name_ok)(tbuf)) {
936 had_error++;
937 continue;
938 }
939 cp += n;
940 /* Get canonical name. */
941 n = strlen(tbuf) + 1; /* for the \0 */
942 if (n > ep - bp || n >= MAXHOSTNAMELEN) {
943 had_error++;
944 continue;
945 }
946 strlcpy(bp, tbuf, (size_t)(ep - bp));
947 canonname = bp;
948 bp += n;
949 continue;
950 }
951 if (qtype == T_ANY) {
952 if (!(type == T_A || type == T_AAAA)) {
953 cp += n;
954 continue;
955 }
956 } else if (type != qtype) {
957 if (type != T_KEY && type != T_SIG)
958 LOG(DEBUG) << __func__ << ": asked for \"" << qname << " " << p_class(C_IN) << " "
959 << p_type(qtype) << "\", got type \"" << p_type(type) << "\"";
960 cp += n;
961 continue; /* XXX - had_error++ ? */
962 }
963 switch (type) {
964 case T_A:
965 case T_AAAA:
966 if (strcasecmp(canonname, bp) != 0) {
967 LOG(DEBUG) << __func__ << ": asked for \"" << canonname << "\", got \"" << bp
968 << "\"";
969 cp += n;
970 continue; /* XXX - had_error++ ? */
971 }
972 if (type == T_A && n != INADDRSZ) {
973 cp += n;
974 continue;
975 }
976 if (type == T_AAAA && n != IN6ADDRSZ) {
977 cp += n;
978 continue;
979 }
980 if (type == T_AAAA) {
981 struct in6_addr in6;
982 memcpy(&in6, cp, IN6ADDRSZ);
983 if (IN6_IS_ADDR_V4MAPPED(&in6)) {
984 cp += n;
985 continue;
986 }
987 }
988 if (!haveanswer) {
989 int nn;
990
991 canonname = bp;
992 nn = strlen(bp) + 1; /* for the \0 */
993 bp += nn;
994 }
995
996 /* don't overwrite pai */
997 ai = *pai;
998 ai.ai_family = (type == T_A) ? AF_INET : AF_INET6;
999 afd = find_afd(ai.ai_family);
1000 if (afd == NULL) {
1001 cp += n;
1002 continue;
1003 }
1004 cur->ai_next = get_ai(&ai, afd, (const char*) cp);
1005 if (cur->ai_next == NULL) had_error++;
1006 while (cur && cur->ai_next) cur = cur->ai_next;
1007 cp += n;
1008 break;
1009 default:
1010 abort();
1011 }
1012 if (!had_error) haveanswer++;
1013 }
1014 if (haveanswer) {
1015 if (!canonname)
1016 (void) get_canonname(pai, sentinel.ai_next, qname);
1017 else
1018 (void) get_canonname(pai, sentinel.ai_next, canonname);
1019 *herrno = NETDB_SUCCESS;
1020 return sentinel.ai_next;
1021 }
1022
1023 *herrno = NO_RECOVERY;
1024 return NULL;
1025 }
1026
1027 struct addrinfo_sort_elem {
1028 struct addrinfo* ai;
1029 int has_src_addr;
1030 sockaddr_union src_addr;
1031 int original_order;
1032 };
1033
_get_scope(const struct sockaddr * addr)1034 static int _get_scope(const struct sockaddr* addr) {
1035 if (addr->sa_family == AF_INET6) {
1036 const struct sockaddr_in6* addr6 = (const struct sockaddr_in6*) addr;
1037 if (IN6_IS_ADDR_MULTICAST(&addr6->sin6_addr)) {
1038 return IPV6_ADDR_MC_SCOPE(&addr6->sin6_addr);
1039 } else if (IN6_IS_ADDR_LOOPBACK(&addr6->sin6_addr) ||
1040 IN6_IS_ADDR_LINKLOCAL(&addr6->sin6_addr)) {
1041 /*
1042 * RFC 4291 section 2.5.3 says loopback is to be treated as having
1043 * link-local scope.
1044 */
1045 return IPV6_ADDR_SCOPE_LINKLOCAL;
1046 } else if (IN6_IS_ADDR_SITELOCAL(&addr6->sin6_addr)) {
1047 return IPV6_ADDR_SCOPE_SITELOCAL;
1048 } else {
1049 return IPV6_ADDR_SCOPE_GLOBAL;
1050 }
1051 } else if (addr->sa_family == AF_INET) {
1052 const struct sockaddr_in* addr4 = (const struct sockaddr_in*) addr;
1053 unsigned long int na = ntohl(addr4->sin_addr.s_addr);
1054
1055 if (IN_LOOPBACK(na) || /* 127.0.0.0/8 */
1056 (na & 0xffff0000) == 0xa9fe0000) { /* 169.254.0.0/16 */
1057 return IPV6_ADDR_SCOPE_LINKLOCAL;
1058 } else {
1059 /*
1060 * RFC 6724 section 3.2. Other IPv4 addresses, including private addresses
1061 * and shared addresses (100.64.0.0/10), are assigned global scope.
1062 */
1063 return IPV6_ADDR_SCOPE_GLOBAL;
1064 }
1065 } else {
1066 /*
1067 * This should never happen.
1068 * Return a scope with low priority as a last resort.
1069 */
1070 return IPV6_ADDR_SCOPE_NODELOCAL;
1071 }
1072 }
1073
1074 /* These macros are modelled after the ones in <netinet/in6.h>. */
1075
1076 /* RFC 4380, section 2.6 */
1077 #define IN6_IS_ADDR_TEREDO(a) \
1078 ((*(const uint32_t*) (const void*) (&(a)->s6_addr[0]) == ntohl(0x20010000)))
1079
1080 /* RFC 3056, section 2. */
1081 #define IN6_IS_ADDR_6TO4(a) (((a)->s6_addr[0] == 0x20) && ((a)->s6_addr[1] == 0x02))
1082
1083 /* 6bone testing address area (3ffe::/16), deprecated in RFC 3701. */
1084 #define IN6_IS_ADDR_6BONE(a) (((a)->s6_addr[0] == 0x3f) && ((a)->s6_addr[1] == 0xfe))
1085
1086 /*
1087 * Get the label for a given IPv4/IPv6 address.
1088 * RFC 6724, section 2.1.
1089 */
1090
_get_label(const struct sockaddr * addr)1091 static int _get_label(const struct sockaddr* addr) {
1092 if (addr->sa_family == AF_INET) {
1093 return 4;
1094 } else if (addr->sa_family == AF_INET6) {
1095 const struct sockaddr_in6* addr6 = (const struct sockaddr_in6*) addr;
1096 if (IN6_IS_ADDR_LOOPBACK(&addr6->sin6_addr)) {
1097 return 0;
1098 } else if (IN6_IS_ADDR_V4MAPPED(&addr6->sin6_addr)) {
1099 return 4;
1100 } else if (IN6_IS_ADDR_6TO4(&addr6->sin6_addr)) {
1101 return 2;
1102 } else if (IN6_IS_ADDR_TEREDO(&addr6->sin6_addr)) {
1103 return 5;
1104 } else if (IN6_IS_ADDR_ULA(&addr6->sin6_addr)) {
1105 return 13;
1106 } else if (IN6_IS_ADDR_V4COMPAT(&addr6->sin6_addr)) {
1107 return 3;
1108 } else if (IN6_IS_ADDR_SITELOCAL(&addr6->sin6_addr)) {
1109 return 11;
1110 } else if (IN6_IS_ADDR_6BONE(&addr6->sin6_addr)) {
1111 return 12;
1112 } else {
1113 /* All other IPv6 addresses, including global unicast addresses. */
1114 return 1;
1115 }
1116 } else {
1117 /*
1118 * This should never happen.
1119 * Return a semi-random label as a last resort.
1120 */
1121 return 1;
1122 }
1123 }
1124
1125 /*
1126 * Get the precedence for a given IPv4/IPv6 address.
1127 * RFC 6724, section 2.1.
1128 */
1129
_get_precedence(const struct sockaddr * addr)1130 static int _get_precedence(const struct sockaddr* addr) {
1131 if (addr->sa_family == AF_INET) {
1132 return 35;
1133 } else if (addr->sa_family == AF_INET6) {
1134 const struct sockaddr_in6* addr6 = (const struct sockaddr_in6*) addr;
1135 if (IN6_IS_ADDR_LOOPBACK(&addr6->sin6_addr)) {
1136 return 50;
1137 } else if (IN6_IS_ADDR_V4MAPPED(&addr6->sin6_addr)) {
1138 return 35;
1139 } else if (IN6_IS_ADDR_6TO4(&addr6->sin6_addr)) {
1140 return 30;
1141 } else if (IN6_IS_ADDR_TEREDO(&addr6->sin6_addr)) {
1142 return 5;
1143 } else if (IN6_IS_ADDR_ULA(&addr6->sin6_addr)) {
1144 return 3;
1145 } else if (IN6_IS_ADDR_V4COMPAT(&addr6->sin6_addr) ||
1146 IN6_IS_ADDR_SITELOCAL(&addr6->sin6_addr) ||
1147 IN6_IS_ADDR_6BONE(&addr6->sin6_addr)) {
1148 return 1;
1149 } else {
1150 /* All other IPv6 addresses, including global unicast addresses. */
1151 return 40;
1152 }
1153 } else {
1154 return 1;
1155 }
1156 }
1157
1158 /*
1159 * Find number of matching initial bits between the two addresses a1 and a2.
1160 */
1161
_common_prefix_len(const struct in6_addr * a1,const struct in6_addr * a2)1162 static int _common_prefix_len(const struct in6_addr* a1, const struct in6_addr* a2) {
1163 const char* p1 = (const char*) a1;
1164 const char* p2 = (const char*) a2;
1165 unsigned i;
1166
1167 for (i = 0; i < sizeof(*a1); ++i) {
1168 int x, j;
1169
1170 if (p1[i] == p2[i]) {
1171 continue;
1172 }
1173 x = p1[i] ^ p2[i];
1174 for (j = 0; j < CHAR_BIT; ++j) {
1175 if (x & (1 << (CHAR_BIT - 1))) {
1176 return i * CHAR_BIT + j;
1177 }
1178 x <<= 1;
1179 }
1180 }
1181 return sizeof(*a1) * CHAR_BIT;
1182 }
1183
1184 /*
1185 * Compare two source/destination address pairs.
1186 * RFC 6724, section 6.
1187 */
1188
_rfc6724_compare(const void * ptr1,const void * ptr2)1189 static int _rfc6724_compare(const void* ptr1, const void* ptr2) {
1190 const struct addrinfo_sort_elem* a1 = (const struct addrinfo_sort_elem*) ptr1;
1191 const struct addrinfo_sort_elem* a2 = (const struct addrinfo_sort_elem*) ptr2;
1192 int scope_src1, scope_dst1, scope_match1;
1193 int scope_src2, scope_dst2, scope_match2;
1194 int label_src1, label_dst1, label_match1;
1195 int label_src2, label_dst2, label_match2;
1196 int precedence1, precedence2;
1197 int prefixlen1, prefixlen2;
1198
1199 /* Rule 1: Avoid unusable destinations. */
1200 if (a1->has_src_addr != a2->has_src_addr) {
1201 return a2->has_src_addr - a1->has_src_addr;
1202 }
1203
1204 /* Rule 2: Prefer matching scope. */
1205 scope_src1 = _get_scope(&a1->src_addr.sa);
1206 scope_dst1 = _get_scope(a1->ai->ai_addr);
1207 scope_match1 = (scope_src1 == scope_dst1);
1208
1209 scope_src2 = _get_scope(&a2->src_addr.sa);
1210 scope_dst2 = _get_scope(a2->ai->ai_addr);
1211 scope_match2 = (scope_src2 == scope_dst2);
1212
1213 if (scope_match1 != scope_match2) {
1214 return scope_match2 - scope_match1;
1215 }
1216
1217 /*
1218 * Rule 3: Avoid deprecated addresses.
1219 * TODO(sesse): We don't currently have a good way of finding this.
1220 */
1221
1222 /*
1223 * Rule 4: Prefer home addresses.
1224 * TODO(sesse): We don't currently have a good way of finding this.
1225 */
1226
1227 /* Rule 5: Prefer matching label. */
1228 label_src1 = _get_label(&a1->src_addr.sa);
1229 label_dst1 = _get_label(a1->ai->ai_addr);
1230 label_match1 = (label_src1 == label_dst1);
1231
1232 label_src2 = _get_label(&a2->src_addr.sa);
1233 label_dst2 = _get_label(a2->ai->ai_addr);
1234 label_match2 = (label_src2 == label_dst2);
1235
1236 if (label_match1 != label_match2) {
1237 return label_match2 - label_match1;
1238 }
1239
1240 /* Rule 6: Prefer higher precedence. */
1241 precedence1 = _get_precedence(a1->ai->ai_addr);
1242 precedence2 = _get_precedence(a2->ai->ai_addr);
1243 if (precedence1 != precedence2) {
1244 return precedence2 - precedence1;
1245 }
1246
1247 /*
1248 * Rule 7: Prefer native transport.
1249 * TODO(sesse): We don't currently have a good way of finding this.
1250 */
1251
1252 /* Rule 8: Prefer smaller scope. */
1253 if (scope_dst1 != scope_dst2) {
1254 return scope_dst1 - scope_dst2;
1255 }
1256
1257 /*
1258 * Rule 9: Use longest matching prefix.
1259 * We implement this for IPv6 only, as the rules in RFC 6724 don't seem
1260 * to work very well directly applied to IPv4. (glibc uses information from
1261 * the routing table for a custom IPv4 implementation here.)
1262 */
1263 if (a1->has_src_addr && a1->ai->ai_addr->sa_family == AF_INET6 && a2->has_src_addr &&
1264 a2->ai->ai_addr->sa_family == AF_INET6) {
1265 const struct sockaddr_in6* a1_src = &a1->src_addr.sin6;
1266 const struct sockaddr_in6* a1_dst = (const struct sockaddr_in6*) a1->ai->ai_addr;
1267 const struct sockaddr_in6* a2_src = &a2->src_addr.sin6;
1268 const struct sockaddr_in6* a2_dst = (const struct sockaddr_in6*) a2->ai->ai_addr;
1269 prefixlen1 = _common_prefix_len(&a1_src->sin6_addr, &a1_dst->sin6_addr);
1270 prefixlen2 = _common_prefix_len(&a2_src->sin6_addr, &a2_dst->sin6_addr);
1271 if (prefixlen1 != prefixlen2) {
1272 return prefixlen2 - prefixlen1;
1273 }
1274 }
1275
1276 /*
1277 * Rule 10: Leave the order unchanged.
1278 * We need this since qsort() is not necessarily stable.
1279 */
1280 return a1->original_order - a2->original_order;
1281 }
1282
1283 /*
1284 * Find the source address that will be used if trying to connect to the given
1285 * address. src_addr must be large enough to hold a struct sockaddr_in6.
1286 *
1287 * Returns 1 if a source address was found, 0 if the address is unreachable,
1288 * and -1 if a fatal error occurred. If 0 or -1, the contents of src_addr are
1289 * undefined.
1290 */
1291
_find_src_addr(const struct sockaddr * addr,struct sockaddr * src_addr,unsigned mark,uid_t uid)1292 static int _find_src_addr(const struct sockaddr* addr, struct sockaddr* src_addr, unsigned mark,
1293 uid_t uid) {
1294 int sock;
1295 int ret;
1296 socklen_t len;
1297
1298 switch (addr->sa_family) {
1299 case AF_INET:
1300 len = sizeof(struct sockaddr_in);
1301 break;
1302 case AF_INET6:
1303 len = sizeof(struct sockaddr_in6);
1304 break;
1305 default:
1306 /* No known usable source address for non-INET families. */
1307 return 0;
1308 }
1309
1310 sock = socket(addr->sa_family, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
1311 if (sock == -1) {
1312 if (errno == EAFNOSUPPORT) {
1313 return 0;
1314 } else {
1315 return -1;
1316 }
1317 }
1318 if (mark != MARK_UNSET && setsockopt(sock, SOL_SOCKET, SO_MARK, &mark, sizeof(mark)) < 0) {
1319 close(sock);
1320 return 0;
1321 }
1322 if (uid > 0 && uid != NET_CONTEXT_INVALID_UID && fchown(sock, uid, (gid_t) -1) < 0) {
1323 close(sock);
1324 return 0;
1325 }
1326 do {
1327 ret = connect(sock, addr, len);
1328 } while (ret == -1 && errno == EINTR);
1329
1330 if (ret == -1) {
1331 close(sock);
1332 return 0;
1333 }
1334
1335 if (src_addr && getsockname(sock, src_addr, &len) == -1) {
1336 close(sock);
1337 return -1;
1338 }
1339 close(sock);
1340 return 1;
1341 }
1342
1343 /*
1344 * Sort the linked list starting at sentinel->ai_next in RFC6724 order.
1345 * Will leave the list unchanged if an error occurs.
1346 */
1347
_rfc6724_sort(struct addrinfo * list_sentinel,unsigned mark,uid_t uid)1348 static void _rfc6724_sort(struct addrinfo* list_sentinel, unsigned mark, uid_t uid) {
1349 struct addrinfo* cur;
1350 int nelem = 0, i;
1351 struct addrinfo_sort_elem* elems;
1352
1353 cur = list_sentinel->ai_next;
1354 while (cur) {
1355 ++nelem;
1356 cur = cur->ai_next;
1357 }
1358
1359 elems = (struct addrinfo_sort_elem*) malloc(nelem * sizeof(struct addrinfo_sort_elem));
1360 if (elems == NULL) {
1361 goto error;
1362 }
1363
1364 /*
1365 * Convert the linked list to an array that also contains the candidate
1366 * source address for each destination address.
1367 */
1368 for (i = 0, cur = list_sentinel->ai_next; i < nelem; ++i, cur = cur->ai_next) {
1369 int has_src_addr;
1370 assert(cur != NULL);
1371 elems[i].ai = cur;
1372 elems[i].original_order = i;
1373
1374 has_src_addr = _find_src_addr(cur->ai_addr, &elems[i].src_addr.sa, mark, uid);
1375 if (has_src_addr == -1) {
1376 goto error;
1377 }
1378 elems[i].has_src_addr = has_src_addr;
1379 }
1380
1381 /* Sort the addresses, and rearrange the linked list so it matches the sorted order. */
1382 qsort((void*) elems, nelem, sizeof(struct addrinfo_sort_elem), _rfc6724_compare);
1383
1384 list_sentinel->ai_next = elems[0].ai;
1385 for (i = 0; i < nelem - 1; ++i) {
1386 elems[i].ai->ai_next = elems[i + 1].ai;
1387 }
1388 elems[nelem - 1].ai->ai_next = NULL;
1389
1390 error:
1391 free(elems);
1392 }
1393
dns_getaddrinfo(const char * name,const addrinfo * pai,const android_net_context * netcontext,addrinfo ** rv,NetworkDnsEventReported * event)1394 static int dns_getaddrinfo(const char* name, const addrinfo* pai,
1395 const android_net_context* netcontext, addrinfo** rv,
1396 NetworkDnsEventReported* event) {
1397 res_target q = {};
1398 res_target q2 = {};
1399
1400 switch (pai->ai_family) {
1401 case AF_UNSPEC: {
1402 /* prefer IPv6 */
1403 q.name = name;
1404 q.qclass = C_IN;
1405 int query_ipv6 = 1, query_ipv4 = 1;
1406 if (pai->ai_flags & AI_ADDRCONFIG) {
1407 query_ipv6 = have_ipv6(netcontext->app_mark, netcontext->uid);
1408 query_ipv4 = have_ipv4(netcontext->app_mark, netcontext->uid);
1409 }
1410 if (query_ipv6) {
1411 q.qtype = T_AAAA;
1412 if (query_ipv4) {
1413 q.next = &q2;
1414 q2.name = name;
1415 q2.qclass = C_IN;
1416 q2.qtype = T_A;
1417 }
1418 } else if (query_ipv4) {
1419 q.qtype = T_A;
1420 } else {
1421 return EAI_NODATA;
1422 }
1423 break;
1424 }
1425 case AF_INET:
1426 q.name = name;
1427 q.qclass = C_IN;
1428 q.qtype = T_A;
1429 break;
1430 case AF_INET6:
1431 q.name = name;
1432 q.qclass = C_IN;
1433 q.qtype = T_AAAA;
1434 break;
1435 default:
1436 return EAI_FAMILY;
1437 }
1438
1439 ResState res;
1440 res_init(&res, netcontext, event);
1441
1442 int he;
1443 if (res_searchN(name, &q, &res, &he) < 0) {
1444 // Return h_errno (he) to catch more detailed errors rather than EAI_NODATA.
1445 // Note that res_searchN() doesn't set the pair NETDB_INTERNAL and errno.
1446 // See also herrnoToAiErrno().
1447 return herrnoToAiErrno(he);
1448 }
1449
1450 addrinfo sentinel = {};
1451 addrinfo* cur = &sentinel;
1452 addrinfo* ai = getanswer(q.answer, q.n, q.name, q.qtype, pai, &he);
1453 if (ai) {
1454 cur->ai_next = ai;
1455 while (cur && cur->ai_next) cur = cur->ai_next;
1456 }
1457 if (q.next) {
1458 ai = getanswer(q2.answer, q2.n, q2.name, q2.qtype, pai, &he);
1459 if (ai) cur->ai_next = ai;
1460 }
1461 if (sentinel.ai_next == NULL) {
1462 // Note that getanswer() doesn't set the pair NETDB_INTERNAL and errno.
1463 // See also herrnoToAiErrno().
1464 return herrnoToAiErrno(he);
1465 }
1466
1467 _rfc6724_sort(&sentinel, netcontext->app_mark, netcontext->uid);
1468
1469 *rv = sentinel.ai_next;
1470 return 0;
1471 }
1472
_sethtent(FILE ** hostf)1473 static void _sethtent(FILE** hostf) {
1474 if (!*hostf)
1475 *hostf = fopen(_PATH_HOSTS, "re");
1476 else
1477 rewind(*hostf);
1478 }
1479
_endhtent(FILE ** hostf)1480 static void _endhtent(FILE** hostf) {
1481 if (*hostf) {
1482 (void) fclose(*hostf);
1483 *hostf = NULL;
1484 }
1485 }
1486
_gethtent(FILE ** hostf,const char * name,const struct addrinfo * pai)1487 static struct addrinfo* _gethtent(FILE** hostf, const char* name, const struct addrinfo* pai) {
1488 char* p;
1489 char *cp, *tname, *cname;
1490 struct addrinfo *res0, *res;
1491 int error;
1492 const char* addr;
1493 char hostbuf[8 * 1024];
1494
1495 assert(name != NULL);
1496 assert(pai != NULL);
1497
1498 if (!*hostf && !(*hostf = fopen(_PATH_HOSTS, "re"))) return (NULL);
1499 again:
1500 if (!(p = fgets(hostbuf, sizeof hostbuf, *hostf))) return (NULL);
1501 if (*p == '#') goto again;
1502 if (!(cp = strpbrk(p, "#\n"))) goto again;
1503 *cp = '\0';
1504 if (!(cp = strpbrk(p, " \t"))) goto again;
1505 *cp++ = '\0';
1506 addr = p;
1507 /* if this is not something we're looking for, skip it. */
1508 cname = NULL;
1509 while (cp && *cp) {
1510 if (*cp == ' ' || *cp == '\t') {
1511 cp++;
1512 continue;
1513 }
1514 if (!cname) cname = cp;
1515 tname = cp;
1516 if ((cp = strpbrk(cp, " \t")) != NULL) *cp++ = '\0';
1517 if (strcasecmp(name, tname) == 0) goto found;
1518 }
1519 goto again;
1520
1521 found:
1522 error = getaddrinfo_numeric(addr, nullptr, *pai, &res0);
1523 if (error) goto again;
1524 for (res = res0; res; res = res->ai_next) {
1525 /* cover it up */
1526 res->ai_flags = pai->ai_flags;
1527
1528 if (pai->ai_flags & AI_CANONNAME) {
1529 if (get_canonname(pai, res, cname) != 0) {
1530 freeaddrinfo(res0);
1531 goto again;
1532 }
1533 }
1534 }
1535 return res0;
1536 }
1537
getCustomHosts(const size_t netid,const char * _Nonnull name,const struct addrinfo * _Nonnull pai)1538 static struct addrinfo* getCustomHosts(const size_t netid, const char* _Nonnull name,
1539 const struct addrinfo* _Nonnull pai) {
1540 struct addrinfo sentinel = {};
1541 struct addrinfo *res0, *res;
1542 res = &sentinel;
1543 std::vector<std::string> hosts = getCustomizedTableByName(netid, name);
1544 for (const std::string& host : hosts) {
1545 int error = getaddrinfo_numeric(host.c_str(), nullptr, *pai, &res0);
1546 if (!error && res0 != nullptr) {
1547 res->ai_next = res0;
1548 res = res0;
1549 res0 = nullptr;
1550 }
1551 }
1552 return sentinel.ai_next;
1553 }
1554
files_getaddrinfo(const size_t netid,const char * name,const addrinfo * pai,addrinfo ** res)1555 static bool files_getaddrinfo(const size_t netid, const char* name, const addrinfo* pai,
1556 addrinfo** res) {
1557 struct addrinfo sentinel = {};
1558 struct addrinfo *p, *cur;
1559 FILE* hostf = nullptr;
1560
1561 cur = &sentinel;
1562 _sethtent(&hostf);
1563 while ((p = _gethtent(&hostf, name, pai)) != nullptr) {
1564 cur->ai_next = p;
1565 while (cur && cur->ai_next) cur = cur->ai_next;
1566 }
1567 _endhtent(&hostf);
1568
1569 if ((p = getCustomHosts(netid, name, pai)) != nullptr) {
1570 cur->ai_next = p;
1571 }
1572
1573 *res = sentinel.ai_next;
1574 return sentinel.ai_next != nullptr;
1575 }
1576
1577 /* resolver logic */
1578
1579 namespace {
1580
1581 constexpr int SLEEP_TIME_MS = 2;
1582
getHerrnoFromRcode(int rcode)1583 int getHerrnoFromRcode(int rcode) {
1584 switch (rcode) {
1585 // Not defined in RFC.
1586 case RCODE_TIMEOUT:
1587 // DNS metrics monitors DNS query timeout.
1588 return NETD_RESOLV_H_ERRNO_EXT_TIMEOUT; // extended h_errno.
1589 // Defined in RFC 1035 section 4.1.1.
1590 case NXDOMAIN:
1591 return HOST_NOT_FOUND;
1592 case SERVFAIL:
1593 return TRY_AGAIN;
1594 case NOERROR:
1595 return NO_DATA;
1596 case FORMERR:
1597 case NOTIMP:
1598 case REFUSED:
1599 default:
1600 return NO_RECOVERY;
1601 }
1602 }
1603
1604 struct QueryResult {
1605 int ancount;
1606 int rcode;
1607 int herrno;
1608 NetworkDnsEventReported event;
1609 };
1610
doQuery(const char * name,res_target * t,res_state res,std::chrono::milliseconds sleepTimeMs)1611 QueryResult doQuery(const char* name, res_target* t, res_state res,
1612 std::chrono::milliseconds sleepTimeMs) {
1613 HEADER* hp = (HEADER*)(void*)t->answer.data();
1614
1615 hp->rcode = NOERROR; // default
1616
1617 const int cl = t->qclass;
1618 const int type = t->qtype;
1619 const int anslen = t->answer.size();
1620
1621 LOG(DEBUG) << __func__ << ": (" << cl << ", " << type << ")";
1622
1623 uint8_t buf[MAXPACKET];
1624
1625 int n = res_nmkquery(QUERY, name, cl, type, /*data=*/nullptr, /*datalen=*/0, buf, sizeof(buf),
1626 res->netcontext_flags);
1627
1628 if (n > 0 &&
1629 (res->netcontext_flags & (NET_CONTEXT_FLAG_USE_DNS_OVER_TLS | NET_CONTEXT_FLAG_USE_EDNS))) {
1630 n = res_nopt(res, n, buf, sizeof(buf), anslen);
1631 }
1632
1633 NetworkDnsEventReported event;
1634 if (n <= 0) {
1635 LOG(ERROR) << __func__ << ": res_nmkquery failed";
1636 return {0, -1, NO_RECOVERY, event};
1637 return {
1638 .ancount = 0,
1639 .rcode = -1,
1640 .herrno = NO_RECOVERY,
1641 .event = event,
1642 };
1643 }
1644
1645 ResState res_temp = fromResState(*res, &event);
1646
1647 int rcode = NOERROR;
1648 n = res_nsend(&res_temp, buf, n, t->answer.data(), anslen, &rcode, 0, sleepTimeMs);
1649 if (n < 0 || hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
1650 // if the query choked with EDNS0, retry without EDNS0
1651 if ((res_temp.netcontext_flags &
1652 (NET_CONTEXT_FLAG_USE_DNS_OVER_TLS | NET_CONTEXT_FLAG_USE_EDNS)) &&
1653 (res_temp._flags & RES_F_EDNS0ERR)) {
1654 LOG(DEBUG) << __func__ << ": retry without EDNS0";
1655 n = res_nmkquery(QUERY, name, cl, type, /*data=*/nullptr, /*datalen=*/0, buf,
1656 sizeof(buf), res->netcontext_flags);
1657 n = res_nsend(&res_temp, buf, n, t->answer.data(), anslen, &rcode, 0);
1658 }
1659 }
1660
1661 LOG(DEBUG) << __func__ << ": rcode=" << hp->rcode << ", ancount=" << ntohs(hp->ancount);
1662
1663 t->n = n;
1664 return {
1665 .ancount = ntohs(hp->ancount),
1666 .rcode = rcode,
1667 .event = event,
1668 };
1669 }
1670
1671 } // namespace
1672
res_queryN_parallel(const char * name,res_target * target,res_state res,int * herrno)1673 static int res_queryN_parallel(const char* name, res_target* target, res_state res, int* herrno) {
1674 std::vector<std::future<QueryResult>> results;
1675 results.reserve(2);
1676 std::chrono::milliseconds sleepTimeMs{};
1677 for (res_target* t = target; t; t = t->next) {
1678 results.emplace_back(std::async(std::launch::async, doQuery, name, t, res, sleepTimeMs));
1679 // Avoiding gateways drop packets if queries are sent too close together
1680 // Only needed if we have multiple queries in a row.
1681 if (t->next) {
1682 int sleepFlag = android::net::Experiments::getInstance()->getFlag(
1683 "parallel_lookup_sleep_time", SLEEP_TIME_MS);
1684 if (sleepFlag > 1000) sleepFlag = 1000;
1685 sleepTimeMs = std::chrono::milliseconds(sleepFlag);
1686 }
1687 }
1688
1689 int ancount = 0;
1690 int rcode = 0;
1691
1692 for (auto& f : results) {
1693 const QueryResult& r = f.get();
1694 if (r.herrno == NO_RECOVERY) {
1695 *herrno = r.herrno;
1696 return -1;
1697 }
1698 res->event->MergeFrom(r.event);
1699 ancount += r.ancount;
1700 rcode = r.rcode;
1701 }
1702
1703 if (ancount == 0) {
1704 *herrno = getHerrnoFromRcode(rcode);
1705 return -1;
1706 }
1707
1708 return ancount;
1709 }
1710
res_queryN_wrapper(const char * name,res_target * target,res_state res,int * herrno)1711 static int res_queryN_wrapper(const char* name, res_target* target, res_state res, int* herrno) {
1712 const bool parallel_lookup =
1713 android::net::Experiments::getInstance()->getFlag("parallel_lookup", 0);
1714 if (parallel_lookup) return res_queryN_parallel(name, target, res, herrno);
1715
1716 return res_queryN(name, target, res, herrno);
1717 }
1718
1719 /*
1720 * Formulate a normal query, send, and await answer.
1721 * Returned answer is placed in supplied buffer "answer".
1722 * Perform preliminary check of answer, returning success only
1723 * if no error is indicated and the answer count is nonzero.
1724 * Return the size of the response on success, -1 on error.
1725 * Error number is left in *herrno.
1726 *
1727 * Caller must parse answer and determine whether it answers the question.
1728 */
res_queryN(const char * name,res_target * target,res_state res,int * herrno)1729 static int res_queryN(const char* name, res_target* target, res_state res, int* herrno) {
1730 uint8_t buf[MAXPACKET];
1731 int n;
1732 struct res_target* t;
1733 int rcode;
1734 int ancount;
1735
1736 assert(name != NULL);
1737 /* XXX: target may be NULL??? */
1738
1739 rcode = NOERROR;
1740 ancount = 0;
1741
1742 for (t = target; t; t = t->next) {
1743 HEADER* hp = (HEADER*)(void*)t->answer.data();
1744 bool retried = false;
1745 again:
1746 hp->rcode = NOERROR; /* default */
1747
1748 /* make it easier... */
1749 int cl = t->qclass;
1750 int type = t->qtype;
1751 const int anslen = t->answer.size();
1752
1753 LOG(DEBUG) << __func__ << ": (" << cl << ", " << type << ")";
1754
1755 n = res_nmkquery(QUERY, name, cl, type, /*data=*/nullptr, /*datalen=*/0, buf, sizeof(buf),
1756 res->netcontext_flags);
1757 if (n > 0 &&
1758 (res->netcontext_flags &
1759 (NET_CONTEXT_FLAG_USE_DNS_OVER_TLS | NET_CONTEXT_FLAG_USE_EDNS)) &&
1760 !retried) // TODO: remove the retry flag and provide a sufficient test coverage.
1761 n = res_nopt(res, n, buf, sizeof(buf), anslen);
1762 if (n <= 0) {
1763 LOG(ERROR) << __func__ << ": res_nmkquery failed";
1764 *herrno = NO_RECOVERY;
1765 return n;
1766 }
1767
1768 n = res_nsend(res, buf, n, t->answer.data(), anslen, &rcode, 0);
1769 if (n < 0 || hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
1770 // Record rcode from DNS response header only if no timeout.
1771 // Keep rcode timeout for reporting later if any.
1772 if (rcode != RCODE_TIMEOUT) rcode = hp->rcode; // record most recent error
1773 // if the query choked with EDNS0, retry without EDNS0 that when the server
1774 // has no response, resovler won't retry and do nothing. Even fallback to UDP,
1775 // we also has the same symptom if EDNS is enabled.
1776 if ((res->netcontext_flags &
1777 (NET_CONTEXT_FLAG_USE_DNS_OVER_TLS | NET_CONTEXT_FLAG_USE_EDNS)) &&
1778 (res->_flags & RES_F_EDNS0ERR) && !retried) {
1779 LOG(DEBUG) << __func__ << ": retry without EDNS0";
1780 retried = true;
1781 goto again;
1782 }
1783 LOG(DEBUG) << __func__ << ": rcode=" << hp->rcode << ", ancount=" << ntohs(hp->ancount);
1784 continue;
1785 }
1786
1787 ancount += ntohs(hp->ancount);
1788
1789 t->n = n;
1790 }
1791
1792 if (ancount == 0) {
1793 *herrno = getHerrnoFromRcode(rcode);
1794 return -1;
1795 }
1796 return ancount;
1797 }
1798
1799 /*
1800 * Formulate a normal query, send, and retrieve answer in supplied buffer.
1801 * Return the size of the response on success, -1 on error.
1802 * If enabled, implement search rules until answer or unrecoverable failure
1803 * is detected. Error code, if any, is left in *herrno.
1804 */
res_searchN(const char * name,res_target * target,res_state res,int * herrno)1805 static int res_searchN(const char* name, res_target* target, res_state res, int* herrno) {
1806 const char* cp;
1807 HEADER* hp;
1808 uint32_t dots;
1809 int ret, saved_herrno;
1810 int got_nodata = 0, got_servfail = 0, tried_as_is = 0;
1811
1812 assert(name != NULL);
1813 assert(target != NULL);
1814
1815 hp = (HEADER*)(void*)target->answer.data();
1816
1817 errno = 0;
1818 *herrno = HOST_NOT_FOUND; /* default, if we never query */
1819 dots = 0;
1820 for (cp = name; *cp; cp++) dots += (*cp == '.');
1821 const bool trailing_dot = (cp > name && *--cp == '.') ? true : false;
1822
1823 /*
1824 * If there are dots in the name already, let's just give it a try
1825 * 'as is'. The threshold can be set with the "ndots" option.
1826 */
1827 saved_herrno = -1;
1828 if (dots >= res->ndots) {
1829 ret = res_querydomainN(name, NULL, target, res, herrno);
1830 if (ret > 0) return (ret);
1831 saved_herrno = *herrno;
1832 tried_as_is++;
1833 }
1834
1835 /*
1836 * We do at least one level of search if
1837 * - there is no dot, or
1838 * - there is at least one dot and there is no trailing dot.
1839 */
1840 if ((!dots) || (dots && !trailing_dot)) {
1841 int done = 0;
1842
1843 /* Unfortunately we need to set stuff up before
1844 * the domain stuff is tried. Will have a better
1845 * fix after thread pools are used.
1846 */
1847 resolv_populate_res_for_net(res);
1848
1849 for (const auto& domain : res->search_domains) {
1850 ret = res_querydomainN(name, domain.c_str(), target, res, herrno);
1851 if (ret > 0) return ret;
1852
1853 /*
1854 * If no server present, give up.
1855 * If name isn't found in this domain,
1856 * keep trying higher domains in the search list
1857 * (if that's enabled).
1858 * On a NO_DATA error, keep trying, otherwise
1859 * a wildcard entry of another type could keep us
1860 * from finding this entry higher in the domain.
1861 * If we get some other error (negative answer or
1862 * server failure), then stop searching up,
1863 * but try the input name below in case it's
1864 * fully-qualified.
1865 */
1866 if (errno == ECONNREFUSED) {
1867 *herrno = TRY_AGAIN;
1868 return -1;
1869 }
1870
1871 switch (*herrno) {
1872 case NO_DATA:
1873 got_nodata++;
1874 [[fallthrough]];
1875 case HOST_NOT_FOUND:
1876 /* keep trying */
1877 break;
1878 case TRY_AGAIN:
1879 if (hp->rcode == SERVFAIL) {
1880 /* try next search element, if any */
1881 got_servfail++;
1882 break;
1883 }
1884 [[fallthrough]];
1885 default:
1886 /* anything else implies that we're done */
1887 done++;
1888 }
1889 }
1890 }
1891
1892 /*
1893 * if we have not already tried the name "as is", do that now.
1894 * note that we do this regardless of how many dots were in the
1895 * name or whether it ends with a dot.
1896 */
1897 if (!tried_as_is) {
1898 ret = res_querydomainN(name, NULL, target, res, herrno);
1899 if (ret > 0) return ret;
1900 }
1901
1902 /*
1903 * if we got here, we didn't satisfy the search.
1904 * if we did an initial full query, return that query's h_errno
1905 * (note that we wouldn't be here if that query had succeeded).
1906 * else if we ever got a nodata, send that back as the reason.
1907 * else send back meaningless h_errno, that being the one from
1908 * the last DNSRCH we did.
1909 */
1910 if (saved_herrno != -1)
1911 *herrno = saved_herrno;
1912 else if (got_nodata)
1913 *herrno = NO_DATA;
1914 else if (got_servfail)
1915 *herrno = TRY_AGAIN;
1916 return -1;
1917 }
1918
1919 // Perform a call on res_query on the concatenation of name and domain,
1920 // removing a trailing dot from name if domain is NULL.
res_querydomainN(const char * name,const char * domain,res_target * target,res_state res,int * herrno)1921 static int res_querydomainN(const char* name, const char* domain, res_target* target, res_state res,
1922 int* herrno) {
1923 char nbuf[MAXDNAME];
1924 const char* longname = nbuf;
1925 size_t n, d;
1926
1927 assert(name != NULL);
1928
1929 if (domain == NULL) {
1930 // Check for trailing '.'; copy without '.' if present.
1931 n = strlen(name);
1932 if (n + 1 > sizeof(nbuf)) {
1933 *herrno = NO_RECOVERY;
1934 return -1;
1935 }
1936 if (n > 0 && name[--n] == '.') {
1937 strncpy(nbuf, name, n);
1938 nbuf[n] = '\0';
1939 } else
1940 longname = name;
1941 } else {
1942 n = strlen(name);
1943 d = strlen(domain);
1944 if (n + 1 + d + 1 > sizeof(nbuf)) {
1945 *herrno = NO_RECOVERY;
1946 return -1;
1947 }
1948 snprintf(nbuf, sizeof(nbuf), "%s.%s", name, domain);
1949 }
1950 return res_queryN_wrapper(longname, target, res, herrno);
1951 }
1952