1 /* $NetBSD: evdns.c,v 1.7 2021/04/10 19:18:45 rillig Exp $ */
2
3 /* Copyright 2006-2007 Niels Provos
4 * Copyright 2007-2012 Nick Mathewson and Niels Provos
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 3. The name of the author may not be used to endorse or promote products
15 * derived from this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 /* Based on software by Adam Langly. Adam's original message:
30 *
31 * Async DNS Library
32 * Adam Langley <agl@imperialviolet.org>
33 * http://www.imperialviolet.org/eventdns.html
34 * Public Domain code
35 *
36 * This software is Public Domain. To view a copy of the public domain dedication,
37 * visit http://creativecommons.org/licenses/publicdomain/ or send a letter to
38 * Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.
39 *
40 * I ask and expect, but do not require, that all derivative works contain an
41 * attribution similar to:
42 * Parts developed by Adam Langley <agl@imperialviolet.org>
43 *
44 * You may wish to replace the word "Parts" with something else depending on
45 * the amount of original code.
46 *
47 * (Derivative works does not include programs which link against, run or include
48 * the source verbatim in their source distributions)
49 *
50 * Version: 0.1b
51 */
52
53 #include "event2/event-config.h"
54 #include <sys/cdefs.h>
55 __RCSID("$NetBSD: evdns.c,v 1.7 2021/04/10 19:18:45 rillig Exp $");
56 #include "evconfig-private.h"
57
58 #include <sys/types.h>
59
60 #ifndef _FORTIFY_SOURCE
61 #define _FORTIFY_SOURCE 3
62 #endif
63
64 #include <string.h>
65 #include <fcntl.h>
66 #ifdef EVENT__HAVE_SYS_TIME_H
67 #include <sys/time.h>
68 #endif
69 #ifdef EVENT__HAVE_STDINT_H
70 #include <stdint.h>
71 #endif
72 #include <stdlib.h>
73 #include <string.h>
74 #include <errno.h>
75 #ifdef EVENT__HAVE_UNISTD_H
76 #include <unistd.h>
77 #endif
78 #include <limits.h>
79 #include <sys/stat.h>
80 #include <stdio.h>
81 #include <stdarg.h>
82 #ifdef _WIN32
83 #include <winsock2.h>
84 #include <winerror.h>
85 #include <ws2tcpip.h>
86 #ifndef _WIN32_IE
87 #define _WIN32_IE 0x400
88 #endif
89 #include <shlobj.h>
90 #endif
91
92 #include "event2/dns.h"
93 #include "event2/dns_struct.h"
94 #include "event2/dns_compat.h"
95 #include "event2/util.h"
96 #include "event2/event.h"
97 #include "event2/event_struct.h"
98 #include "event2/thread.h"
99
100 #include "defer-internal.h"
101 #include "log-internal.h"
102 #include "mm-internal.h"
103 #include "strlcpy-internal.h"
104 #include "ipv6-internal.h"
105 #include "util-internal.h"
106 #include "evthread-internal.h"
107 #ifdef _WIN32
108 #include <ctype.h>
109 #include <winsock2.h>
110 #include <windows.h>
111 #include <iphlpapi.h>
112 #include <io.h>
113 #else
114 #include <sys/socket.h>
115 #include <netinet/in.h>
116 #include <arpa/inet.h>
117 #endif
118
119 #ifdef EVENT__HAVE_NETINET_IN6_H
120 #include <netinet/in6.h>
121 #endif
122
123 #define EVDNS_LOG_DEBUG EVENT_LOG_DEBUG
124 #define EVDNS_LOG_WARN EVENT_LOG_WARN
125 #define EVDNS_LOG_MSG EVENT_LOG_MSG
126
127 #ifndef HOST_NAME_MAX
128 #define HOST_NAME_MAX 255
129 #endif
130
131 #include <stdio.h>
132
133 #undef MIN
134 #define MIN(a,b) ((a)<(b)?(a):(b))
135
136 #define ASSERT_VALID_REQUEST(req) \
137 EVUTIL_ASSERT((req)->handle && (req)->handle->current_req == (req))
138
139 #define u64 ev_uint64_t
140 #define u32 ev_uint32_t
141 #define u16 ev_uint16_t
142 #define u8 ev_uint8_t
143
144 /* maximum number of addresses from a single packet */
145 /* that we bother recording */
146 #define MAX_V4_ADDRS 32
147 #define MAX_V6_ADDRS 32
148
149
150 #define TYPE_A EVDNS_TYPE_A
151 #define TYPE_CNAME 5
152 #define TYPE_PTR EVDNS_TYPE_PTR
153 #define TYPE_SOA EVDNS_TYPE_SOA
154 #define TYPE_AAAA EVDNS_TYPE_AAAA
155
156 #define CLASS_INET EVDNS_CLASS_INET
157
158 /* Persistent handle. We keep this separate from 'struct request' since we
159 * need some object to last for as long as an evdns_request is outstanding so
160 * that it can be canceled, whereas a search request can lead to multiple
161 * 'struct request' instances being created over its lifetime. */
162 struct evdns_request {
163 struct request *current_req;
164 struct evdns_base *base;
165
166 int pending_cb; /* Waiting for its callback to be invoked; not
167 * owned by event base any more. */
168
169 /* elements used by the searching code */
170 int search_index;
171 struct search_state *search_state;
172 char *search_origname; /* needs to be free()ed */
173 int search_flags;
174 };
175
176 struct request {
177 u8 *request; /* the dns packet data */
178 u8 request_type; /* TYPE_PTR or TYPE_A or TYPE_AAAA */
179 unsigned int request_len;
180 int reissue_count;
181 int tx_count; /* the number of times that this packet has been sent */
182 void *user_pointer; /* the pointer given to us for this request */
183 evdns_callback_type user_callback;
184 struct nameserver *ns; /* the server which we last sent it */
185
186 /* these objects are kept in a circular list */
187 /* XXX We could turn this into a CIRCLEQ. */
188 struct request *next, *prev;
189
190 struct event timeout_event;
191
192 u16 trans_id; /* the transaction id */
193 unsigned request_appended :1; /* true if the request pointer is data which follows this struct */
194 unsigned transmit_me :1; /* needs to be transmitted */
195
196 /* XXXX This is a horrible hack. */
197 char **put_cname_in_ptr; /* store the cname here if we get one. */
198
199 struct evdns_base *base;
200
201 struct evdns_request *handle;
202 };
203
204 struct reply {
205 unsigned int type;
206 unsigned int have_answer : 1;
207 union {
208 struct {
209 u32 addrcount;
210 u32 addresses[MAX_V4_ADDRS];
211 } a;
212 struct {
213 u32 addrcount;
214 struct in6_addr addresses[MAX_V6_ADDRS];
215 } aaaa;
216 struct {
217 char name[HOST_NAME_MAX];
218 } ptr;
219 } data;
220 };
221
222 struct nameserver {
223 evutil_socket_t socket; /* a connected UDP socket */
224 struct sockaddr_storage address;
225 ev_socklen_t addrlen;
226 int failed_times; /* number of times which we have given this server a chance */
227 int timedout; /* number of times in a row a request has timed out */
228 struct event event;
229 /* these objects are kept in a circular list */
230 struct nameserver *next, *prev;
231 struct event timeout_event; /* used to keep the timeout for */
232 /* when we next probe this server. */
233 /* Valid if state == 0 */
234 /* Outstanding probe request for this nameserver, if any */
235 struct evdns_request *probe_request;
236 char state; /* zero if we think that this server is down */
237 char choked; /* true if we have an EAGAIN from this server's socket */
238 char write_waiting; /* true if we are waiting for EV_WRITE events */
239 struct evdns_base *base;
240
241 /* Number of currently inflight requests: used
242 * to track when we should add/del the event. */
243 int requests_inflight;
244 };
245
246
247 /* Represents a local port where we're listening for DNS requests. Right now, */
248 /* only UDP is supported. */
249 struct evdns_server_port {
250 evutil_socket_t socket; /* socket we use to read queries and write replies. */
251 int refcnt; /* reference count. */
252 char choked; /* Are we currently blocked from writing? */
253 char closing; /* Are we trying to close this port, pending writes? */
254 evdns_request_callback_fn_type user_callback; /* Fn to handle requests */
255 void *user_data; /* Opaque pointer passed to user_callback */
256 struct event event; /* Read/write event */
257 /* circular list of replies that we want to write. */
258 struct server_request *pending_replies;
259 struct event_base *event_base;
260
261 #ifndef EVENT__DISABLE_THREAD_SUPPORT
262 void *lock;
263 #endif
264 };
265
266 /* Represents part of a reply being built. (That is, a single RR.) */
267 struct server_reply_item {
268 struct server_reply_item *next; /* next item in sequence. */
269 char *name; /* name part of the RR */
270 u16 type; /* The RR type */
271 u16 class; /* The RR class (usually CLASS_INET) */
272 u32 ttl; /* The RR TTL */
273 char is_name; /* True iff data is a label */
274 u16 datalen; /* Length of data; -1 if data is a label */
275 void *data; /* The contents of the RR */
276 };
277
278 /* Represents a request that we've received as a DNS server, and holds */
279 /* the components of the reply as we're constructing it. */
280 struct server_request {
281 /* Pointers to the next and previous entries on the list of replies */
282 /* that we're waiting to write. Only set if we have tried to respond */
283 /* and gotten EAGAIN. */
284 struct server_request *next_pending;
285 struct server_request *prev_pending;
286
287 u16 trans_id; /* Transaction id. */
288 struct evdns_server_port *port; /* Which port received this request on? */
289 struct sockaddr_storage addr; /* Where to send the response */
290 ev_socklen_t addrlen; /* length of addr */
291
292 int n_answer; /* how many answer RRs have been set? */
293 int n_authority; /* how many authority RRs have been set? */
294 int n_additional; /* how many additional RRs have been set? */
295
296 struct server_reply_item *answer; /* linked list of answer RRs */
297 struct server_reply_item *authority; /* linked list of authority RRs */
298 struct server_reply_item *additional; /* linked list of additional RRs */
299
300 /* Constructed response. Only set once we're ready to send a reply. */
301 /* Once this is set, the RR fields are cleared, and no more should be set. */
302 char *response;
303 size_t response_len;
304
305 /* Caller-visible fields: flags, questions. */
306 struct evdns_server_request base;
307 };
308
309 struct evdns_base {
310 /* An array of n_req_heads circular lists for inflight requests.
311 * Each inflight request req is in req_heads[req->trans_id % n_req_heads].
312 */
313 struct request **req_heads;
314 /* A circular list of requests that we're waiting to send, but haven't
315 * sent yet because there are too many requests inflight */
316 struct request *req_waiting_head;
317 /* A circular list of nameservers. */
318 struct nameserver *server_head;
319 int n_req_heads;
320
321 struct event_base *event_base;
322
323 /* The number of good nameservers that we have */
324 int global_good_nameservers;
325
326 /* inflight requests are contained in the req_head list */
327 /* and are actually going out across the network */
328 int global_requests_inflight;
329 /* requests which aren't inflight are in the waiting list */
330 /* and are counted here */
331 int global_requests_waiting;
332
333 int global_max_requests_inflight;
334
335 struct timeval global_timeout; /* 5 seconds by default */
336 int global_max_reissues; /* a reissue occurs when we get some errors from the server */
337 int global_max_retransmits; /* number of times we'll retransmit a request which timed out */
338 /* number of timeouts in a row before we consider this server to be down */
339 int global_max_nameserver_timeout;
340 /* true iff we will use the 0x20 hack to prevent poisoning attacks. */
341 int global_randomize_case;
342
343 /* The first time that a nameserver fails, how long do we wait before
344 * probing to see if it has returned? */
345 struct timeval global_nameserver_probe_initial_timeout;
346
347 /** Port to bind to for outgoing DNS packets. */
348 struct sockaddr_storage global_outgoing_address;
349 /** ev_socklen_t for global_outgoing_address. 0 if it isn't set. */
350 ev_socklen_t global_outgoing_addrlen;
351
352 struct timeval global_getaddrinfo_allow_skew;
353
354 int so_rcvbuf;
355 int so_sndbuf;
356
357 int getaddrinfo_ipv4_timeouts;
358 int getaddrinfo_ipv6_timeouts;
359 int getaddrinfo_ipv4_answered;
360 int getaddrinfo_ipv6_answered;
361
362 struct search_state *global_search_state;
363
364 TAILQ_HEAD(hosts_list, hosts_entry) hostsdb;
365
366 #ifndef EVENT__DISABLE_THREAD_SUPPORT
367 void *lock;
368 #endif
369
370 int disable_when_inactive;
371 };
372
373 struct hosts_entry {
374 TAILQ_ENTRY(hosts_entry) next;
375 union {
376 struct sockaddr sa;
377 struct sockaddr_in sin;
378 struct sockaddr_in6 sin6;
379 } addr;
380 int addrlen;
381 char hostname[1];
382 };
383
384 static struct evdns_base *current_base = NULL;
385
386 struct evdns_base *
evdns_get_global_base(void)387 evdns_get_global_base(void)
388 {
389 return current_base;
390 }
391
392 /* Given a pointer to an evdns_server_request, get the corresponding */
393 /* server_request. */
394 #define TO_SERVER_REQUEST(base_ptr) \
395 ((struct server_request*) \
396 (((char*)(base_ptr) - evutil_offsetof(struct server_request, base))))
397
398 #define REQ_HEAD(base, id) ((base)->req_heads[id % (base)->n_req_heads])
399
400 static struct nameserver *nameserver_pick(struct evdns_base *base);
401 static void evdns_request_insert(struct request *req, struct request **head);
402 static void evdns_request_remove(struct request *req, struct request **head);
403 static void nameserver_ready_callback(evutil_socket_t fd, short events, void *arg);
404 static int evdns_transmit(struct evdns_base *base);
405 static int evdns_request_transmit(struct request *req);
406 static void nameserver_send_probe(struct nameserver *const ns);
407 static void search_request_finished(struct evdns_request *const);
408 static int search_try_next(struct evdns_request *const req);
409 static struct request *search_request_new(struct evdns_base *base, struct evdns_request *handle, int type, const char *const name, int flags, evdns_callback_type user_callback, void *user_arg);
410 static void evdns_requests_pump_waiting_queue(struct evdns_base *base);
411 static u16 transaction_id_pick(struct evdns_base *base);
412 static struct request *request_new(struct evdns_base *base, struct evdns_request *handle, int type, const char *name, int flags, evdns_callback_type callback, void *ptr);
413 static void request_submit(struct request *const req);
414
415 static int server_request_free(struct server_request *req);
416 static void server_request_free_answers(struct server_request *req);
417 static void server_port_free(struct evdns_server_port *port);
418 static void server_port_ready_callback(evutil_socket_t fd, short events, void *arg);
419 static int evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char *const filename);
420 static int evdns_base_set_option_impl(struct evdns_base *base,
421 const char *option, const char *val, int flags);
422 static void evdns_base_free_and_unlock(struct evdns_base *base, int fail_requests);
423 static void evdns_request_timeout_callback(evutil_socket_t fd, short events, void *arg);
424
425 static int strtoint(const char *const str);
426
427 #ifdef EVENT__DISABLE_THREAD_SUPPORT
428 #define EVDNS_LOCK(base) EVUTIL_NIL_STMT_
429 #define EVDNS_UNLOCK(base) EVUTIL_NIL_STMT_
430 #define ASSERT_LOCKED(base) EVUTIL_NIL_STMT_
431 #else
432 #define EVDNS_LOCK(base) \
433 EVLOCK_LOCK((base)->lock, 0)
434 #define EVDNS_UNLOCK(base) \
435 EVLOCK_UNLOCK((base)->lock, 0)
436 #define ASSERT_LOCKED(base) \
437 EVLOCK_ASSERT_LOCKED((base)->lock)
438 #endif
439
440 static evdns_debug_log_fn_type evdns_log_fn = NULL;
441
442 void
evdns_set_log_fn(evdns_debug_log_fn_type fn)443 evdns_set_log_fn(evdns_debug_log_fn_type fn)
444 {
445 evdns_log_fn = fn;
446 }
447
448 #ifdef __GNUC__
449 #define EVDNS_LOG_CHECK __attribute__ ((format(printf, 2, 3)))
450 #else
451 #define EVDNS_LOG_CHECK
452 #endif
453
454 static void evdns_log_(int severity, const char *fmt, ...) EVDNS_LOG_CHECK;
455 static void
evdns_log_(int severity,const char * fmt,...)456 evdns_log_(int severity, const char *fmt, ...)
457 {
458 va_list args;
459 va_start(args,fmt);
460 if (evdns_log_fn) {
461 char buf[512];
462 int is_warn = (severity == EVDNS_LOG_WARN);
463 evutil_vsnprintf(buf, sizeof(buf), fmt, args);
464 evdns_log_fn(is_warn, buf);
465 } else {
466 event_logv_(severity, NULL, fmt, args);
467 }
468 va_end(args);
469 }
470
471 #define log evdns_log_
472
473 /* This walks the list of inflight requests to find the */
474 /* one with a matching transaction id. Returns NULL on */
475 /* failure */
476 static struct request *
request_find_from_trans_id(struct evdns_base * base,u16 trans_id)477 request_find_from_trans_id(struct evdns_base *base, u16 trans_id) {
478 struct request *req = REQ_HEAD(base, trans_id);
479 struct request *const started_at = req;
480
481 ASSERT_LOCKED(base);
482
483 if (req) {
484 do {
485 if (req->trans_id == trans_id) return req;
486 req = req->next;
487 } while (req != started_at);
488 }
489
490 return NULL;
491 }
492
493 /* a libevent callback function which is called when a nameserver */
494 /* has gone down and we want to test if it has came back to life yet */
495 static void
nameserver_prod_callback(evutil_socket_t fd,short events,void * arg)496 nameserver_prod_callback(evutil_socket_t fd, short events, void *arg) {
497 struct nameserver *const ns = (struct nameserver *) arg;
498 (void)fd;
499 (void)events;
500
501 EVDNS_LOCK(ns->base);
502 nameserver_send_probe(ns);
503 EVDNS_UNLOCK(ns->base);
504 }
505
506 /* a libevent callback which is called when a nameserver probe (to see if */
507 /* it has come back to life) times out. We increment the count of failed_times */
508 /* and wait longer to send the next probe packet. */
509 static void
nameserver_probe_failed(struct nameserver * const ns)510 nameserver_probe_failed(struct nameserver *const ns) {
511 struct timeval timeout;
512 int i;
513
514 ASSERT_LOCKED(ns->base);
515 (void) evtimer_del(&ns->timeout_event);
516 if (ns->state == 1) {
517 /* This can happen if the nameserver acts in a way which makes us mark */
518 /* it as bad and then starts sending good replies. */
519 return;
520 }
521
522 #define MAX_PROBE_TIMEOUT 3600
523 #define TIMEOUT_BACKOFF_FACTOR 3
524
525 memcpy(&timeout, &ns->base->global_nameserver_probe_initial_timeout,
526 sizeof(struct timeval));
527 for (i=ns->failed_times; i > 0 && timeout.tv_sec < MAX_PROBE_TIMEOUT; --i) {
528 timeout.tv_sec *= TIMEOUT_BACKOFF_FACTOR;
529 timeout.tv_usec *= TIMEOUT_BACKOFF_FACTOR;
530 if (timeout.tv_usec > 1000000) {
531 timeout.tv_sec += timeout.tv_usec / 1000000;
532 timeout.tv_usec %= 1000000;
533 }
534 }
535 if (timeout.tv_sec > MAX_PROBE_TIMEOUT) {
536 timeout.tv_sec = MAX_PROBE_TIMEOUT;
537 timeout.tv_usec = 0;
538 }
539
540 ns->failed_times++;
541
542 if (evtimer_add(&ns->timeout_event, &timeout) < 0) {
543 char addrbuf[128];
544 log(EVDNS_LOG_WARN,
545 "Error from libevent when adding timer event for %s",
546 evutil_format_sockaddr_port_(
547 (struct sockaddr *)&ns->address,
548 addrbuf, sizeof(addrbuf)));
549 }
550 }
551
552 static void
request_swap_ns(struct request * req,struct nameserver * ns)553 request_swap_ns(struct request *req, struct nameserver *ns) {
554 if (ns && req->ns != ns) {
555 EVUTIL_ASSERT(req->ns->requests_inflight > 0);
556 req->ns->requests_inflight--;
557 ns->requests_inflight++;
558
559 req->ns = ns;
560 }
561 }
562
563 /* called when a nameserver has been deemed to have failed. For example, too */
564 /* many packets have timed out etc */
565 static void
nameserver_failed(struct nameserver * const ns,const char * msg)566 nameserver_failed(struct nameserver *const ns, const char *msg) {
567 struct request *req, *started_at;
568 struct evdns_base *base = ns->base;
569 int i;
570 char addrbuf[128];
571
572 ASSERT_LOCKED(base);
573 /* if this nameserver has already been marked as failed */
574 /* then don't do anything */
575 if (!ns->state) return;
576
577 log(EVDNS_LOG_MSG, "Nameserver %s has failed: %s",
578 evutil_format_sockaddr_port_(
579 (struct sockaddr *)&ns->address,
580 addrbuf, sizeof(addrbuf)),
581 msg);
582
583 base->global_good_nameservers--;
584 EVUTIL_ASSERT(base->global_good_nameservers >= 0);
585 if (base->global_good_nameservers == 0) {
586 log(EVDNS_LOG_MSG, "All nameservers have failed");
587 }
588
589 ns->state = 0;
590 ns->failed_times = 1;
591
592 if (evtimer_add(&ns->timeout_event,
593 &base->global_nameserver_probe_initial_timeout) < 0) {
594 log(EVDNS_LOG_WARN,
595 "Error from libevent when adding timer event for %s",
596 evutil_format_sockaddr_port_(
597 (struct sockaddr *)&ns->address,
598 addrbuf, sizeof(addrbuf)));
599 /* ???? Do more? */
600 }
601
602 /* walk the list of inflight requests to see if any can be reassigned to */
603 /* a different server. Requests in the waiting queue don't have a */
604 /* nameserver assigned yet */
605
606 /* if we don't have *any* good nameservers then there's no point */
607 /* trying to reassign requests to one */
608 if (!base->global_good_nameservers) return;
609
610 for (i = 0; i < base->n_req_heads; ++i) {
611 req = started_at = base->req_heads[i];
612 if (req) {
613 do {
614 if (req->tx_count == 0 && req->ns == ns) {
615 /* still waiting to go out, can be moved */
616 /* to another server */
617 request_swap_ns(req, nameserver_pick(base));
618 }
619 req = req->next;
620 } while (req != started_at);
621 }
622 }
623 }
624
625 static void
nameserver_up(struct nameserver * const ns)626 nameserver_up(struct nameserver *const ns)
627 {
628 char addrbuf[128];
629 ASSERT_LOCKED(ns->base);
630 if (ns->state) return;
631 log(EVDNS_LOG_MSG, "Nameserver %s is back up",
632 evutil_format_sockaddr_port_(
633 (struct sockaddr *)&ns->address,
634 addrbuf, sizeof(addrbuf)));
635 evtimer_del(&ns->timeout_event);
636 if (ns->probe_request) {
637 evdns_cancel_request(ns->base, ns->probe_request);
638 ns->probe_request = NULL;
639 }
640 ns->state = 1;
641 ns->failed_times = 0;
642 ns->timedout = 0;
643 ns->base->global_good_nameservers++;
644 }
645
646 static void
request_trans_id_set(struct request * const req,const u16 trans_id)647 request_trans_id_set(struct request *const req, const u16 trans_id) {
648 req->trans_id = trans_id;
649 *((u16 *) req->request) = htons(trans_id);
650 }
651
652 /* Called to remove a request from a list and dealloc it. */
653 /* head is a pointer to the head of the list it should be */
654 /* removed from or NULL if the request isn't in a list. */
655 /* when free_handle is one, free the handle as well. */
656 static void
request_finished(struct request * const req,struct request ** head,int free_handle)657 request_finished(struct request *const req, struct request **head, int free_handle) {
658 struct evdns_base *base = req->base;
659 int was_inflight = (head != &base->req_waiting_head);
660 EVDNS_LOCK(base);
661 ASSERT_VALID_REQUEST(req);
662
663 if (head)
664 evdns_request_remove(req, head);
665
666 log(EVDNS_LOG_DEBUG, "Removing timeout for request %p", req);
667 if (was_inflight) {
668 evtimer_del(&req->timeout_event);
669 base->global_requests_inflight--;
670 req->ns->requests_inflight--;
671 } else {
672 base->global_requests_waiting--;
673 }
674 /* it was initialized during request_new / evtimer_assign */
675 event_debug_unassign(&req->timeout_event);
676
677 if (req->ns &&
678 req->ns->requests_inflight == 0 &&
679 req->base->disable_when_inactive) {
680 event_del(&req->ns->event);
681 evtimer_del(&req->ns->timeout_event);
682 }
683
684 if (!req->request_appended) {
685 /* need to free the request data on it's own */
686 mm_free(req->request);
687 } else {
688 /* the request data is appended onto the header */
689 /* so everything gets free()ed when we: */
690 }
691
692 if (req->handle) {
693 EVUTIL_ASSERT(req->handle->current_req == req);
694
695 if (free_handle) {
696 search_request_finished(req->handle);
697 req->handle->current_req = NULL;
698 if (! req->handle->pending_cb) {
699 /* If we're planning to run the callback,
700 * don't free the handle until later. */
701 mm_free(req->handle);
702 }
703 req->handle = NULL; /* If we have a bug, let's crash
704 * early */
705 } else {
706 req->handle->current_req = NULL;
707 }
708 }
709
710 mm_free(req);
711
712 evdns_requests_pump_waiting_queue(base);
713 EVDNS_UNLOCK(base);
714 }
715
716 /* This is called when a server returns a funny error code. */
717 /* We try the request again with another server. */
718 /* */
719 /* return: */
720 /* 0 ok */
721 /* 1 failed/reissue is pointless */
722 static int
request_reissue(struct request * req)723 request_reissue(struct request *req) {
724 const struct nameserver *const last_ns = req->ns;
725 ASSERT_LOCKED(req->base);
726 ASSERT_VALID_REQUEST(req);
727 /* the last nameserver should have been marked as failing */
728 /* by the caller of this function, therefore pick will try */
729 /* not to return it */
730 request_swap_ns(req, nameserver_pick(req->base));
731 if (req->ns == last_ns) {
732 /* ... but pick did return it */
733 /* not a lot of point in trying again with the */
734 /* same server */
735 return 1;
736 }
737
738 req->reissue_count++;
739 req->tx_count = 0;
740 req->transmit_me = 1;
741
742 return 0;
743 }
744
745 /* this function looks for space on the inflight queue and promotes */
746 /* requests from the waiting queue if it can. */
747 /* */
748 /* TODO: */
749 /* add return code, see at nameserver_pick() and other functions. */
750 static void
evdns_requests_pump_waiting_queue(struct evdns_base * base)751 evdns_requests_pump_waiting_queue(struct evdns_base *base) {
752 ASSERT_LOCKED(base);
753 while (base->global_requests_inflight < base->global_max_requests_inflight &&
754 base->global_requests_waiting) {
755 struct request *req;
756
757 EVUTIL_ASSERT(base->req_waiting_head);
758 req = base->req_waiting_head;
759
760 req->ns = nameserver_pick(base);
761 if (!req->ns)
762 return;
763
764 /* move a request from the waiting queue to the inflight queue */
765 req->ns->requests_inflight++;
766
767 evdns_request_remove(req, &base->req_waiting_head);
768
769 base->global_requests_waiting--;
770 base->global_requests_inflight++;
771
772 request_trans_id_set(req, transaction_id_pick(base));
773
774 evdns_request_insert(req, &REQ_HEAD(base, req->trans_id));
775 evdns_request_transmit(req);
776 evdns_transmit(base);
777 }
778 }
779
780 /* TODO(nickm) document */
781 struct deferred_reply_callback {
782 struct event_callback deferred;
783 struct evdns_request *handle;
784 u8 request_type;
785 u8 have_reply;
786 u32 ttl;
787 u32 err;
788 evdns_callback_type user_callback;
789 struct reply reply;
790 };
791
792 static void
reply_run_callback(struct event_callback * d,void * user_pointer)793 reply_run_callback(struct event_callback *d, void *user_pointer)
794 {
795 struct deferred_reply_callback *cb =
796 EVUTIL_UPCAST(d, struct deferred_reply_callback, deferred);
797
798 switch (cb->request_type) {
799 case TYPE_A:
800 if (cb->have_reply)
801 cb->user_callback(DNS_ERR_NONE, DNS_IPv4_A,
802 cb->reply.data.a.addrcount, cb->ttl,
803 cb->reply.data.a.addresses,
804 user_pointer);
805 else
806 cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer);
807 break;
808 case TYPE_PTR:
809 if (cb->have_reply) {
810 char *name = cb->reply.data.ptr.name;
811 cb->user_callback(DNS_ERR_NONE, DNS_PTR, 1, cb->ttl,
812 &name, user_pointer);
813 } else {
814 cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer);
815 }
816 break;
817 case TYPE_AAAA:
818 if (cb->have_reply)
819 cb->user_callback(DNS_ERR_NONE, DNS_IPv6_AAAA,
820 cb->reply.data.aaaa.addrcount, cb->ttl,
821 cb->reply.data.aaaa.addresses,
822 user_pointer);
823 else
824 cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer);
825 break;
826 default:
827 EVUTIL_ASSERT(0);
828 }
829
830 if (cb->handle && cb->handle->pending_cb) {
831 mm_free(cb->handle);
832 }
833
834 mm_free(cb);
835 }
836
837 static void
reply_schedule_callback(struct request * const req,u32 ttl,u32 err,struct reply * reply)838 reply_schedule_callback(struct request *const req, u32 ttl, u32 err, struct reply *reply)
839 {
840 struct deferred_reply_callback *d = mm_calloc(1, sizeof(*d));
841
842 if (!d) {
843 event_warn("%s: Couldn't allocate space for deferred callback.",
844 __func__);
845 return;
846 }
847
848 ASSERT_LOCKED(req->base);
849
850 d->request_type = req->request_type;
851 d->user_callback = req->user_callback;
852 d->ttl = ttl;
853 d->err = err;
854 if (reply) {
855 d->have_reply = 1;
856 memcpy(&d->reply, reply, sizeof(struct reply));
857 }
858
859 if (req->handle) {
860 req->handle->pending_cb = 1;
861 d->handle = req->handle;
862 }
863
864 event_deferred_cb_init_(
865 &d->deferred,
866 event_get_priority(&req->timeout_event),
867 reply_run_callback,
868 req->user_pointer);
869 event_deferred_cb_schedule_(
870 req->base->event_base,
871 &d->deferred);
872 }
873
874
875 #define _QR_MASK 0x8000U
876 #define _OP_MASK 0x7800U
877 #define _AA_MASK 0x0400U
878 #define _TC_MASK 0x0200U
879 #define _RD_MASK 0x0100U
880 #define _RA_MASK 0x0080U
881 #define _Z_MASK 0x0040U
882 #define _AD_MASK 0x0020U
883 #define _CD_MASK 0x0010U
884 #define _RCODE_MASK 0x000fU
885 #define _Z_MASK_DEPRECATED 0x0070U
886
887 /* this processes a parsed reply packet */
888 static void
reply_handle(struct request * const req,u16 flags,u32 ttl,struct reply * reply)889 reply_handle(struct request *const req, u16 flags, u32 ttl, struct reply *reply) {
890 int error;
891 char addrbuf[128];
892 static const int error_codes[] = {
893 DNS_ERR_FORMAT, DNS_ERR_SERVERFAILED, DNS_ERR_NOTEXIST,
894 DNS_ERR_NOTIMPL, DNS_ERR_REFUSED
895 };
896
897 ASSERT_LOCKED(req->base);
898 ASSERT_VALID_REQUEST(req);
899
900 if (flags & (_RCODE_MASK | _TC_MASK) || !reply || !reply->have_answer) {
901 /* there was an error */
902 if (flags & _TC_MASK) {
903 error = DNS_ERR_TRUNCATED;
904 } else if (flags & _RCODE_MASK) {
905 u16 error_code = (flags & _RCODE_MASK) - 1;
906 if (error_code > 4) {
907 error = DNS_ERR_UNKNOWN;
908 } else {
909 error = error_codes[error_code];
910 }
911 } else if (reply && !reply->have_answer) {
912 error = DNS_ERR_NODATA;
913 } else {
914 error = DNS_ERR_UNKNOWN;
915 }
916
917 switch (error) {
918 case DNS_ERR_NOTIMPL:
919 case DNS_ERR_REFUSED:
920 /* we regard these errors as marking a bad nameserver */
921 if (req->reissue_count < req->base->global_max_reissues) {
922 char msg[64];
923 evutil_snprintf(msg, sizeof(msg), "Bad response %d (%s)",
924 error, evdns_err_to_string(error));
925 nameserver_failed(req->ns, msg);
926 if (!request_reissue(req)) return;
927 }
928 break;
929 case DNS_ERR_SERVERFAILED:
930 /* rcode 2 (servfailed) sometimes means "we
931 * are broken" and sometimes (with some binds)
932 * means "that request was very confusing."
933 * Treat this as a timeout, not a failure.
934 */
935 log(EVDNS_LOG_DEBUG, "Got a SERVERFAILED from nameserver"
936 "at %s; will allow the request to time out.",
937 evutil_format_sockaddr_port_(
938 (struct sockaddr *)&req->ns->address,
939 addrbuf, sizeof(addrbuf)));
940 /* Call the timeout function */
941 evdns_request_timeout_callback(0, 0, req);
942 return;
943 default:
944 /* we got a good reply from the nameserver: it is up. */
945 if (req->handle == req->ns->probe_request) {
946 /* Avoid double-free */
947 req->ns->probe_request = NULL;
948 }
949
950 nameserver_up(req->ns);
951 }
952
953 if (req->handle->search_state &&
954 req->request_type != TYPE_PTR) {
955 /* if we have a list of domains to search in,
956 * try the next one */
957 if (!search_try_next(req->handle)) {
958 /* a new request was issued so this
959 * request is finished and */
960 /* the user callback will be made when
961 * that request (or a */
962 /* child of it) finishes. */
963 return;
964 }
965 }
966
967 /* all else failed. Pass the failure up */
968 reply_schedule_callback(req, ttl, error, NULL);
969 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1);
970 } else {
971 /* all ok, tell the user */
972 reply_schedule_callback(req, ttl, 0, reply);
973 if (req->handle == req->ns->probe_request)
974 req->ns->probe_request = NULL; /* Avoid double-free */
975 nameserver_up(req->ns);
976 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1);
977 }
978 }
979
980 static int
name_parse(u8 * packet,int length,int * idx,char * name_out,int name_out_len)981 name_parse(u8 *packet, int length, int *idx, char *name_out, int name_out_len) {
982 int name_end = -1;
983 int j = *idx;
984 int ptr_count = 0;
985 #define GET32(x) do { if (j + 4 > length) goto err; memcpy(&t32_, packet + j, 4); j += 4; x = ntohl(t32_); } while (0)
986 #define GET16(x) do { if (j + 2 > length) goto err; memcpy(&t_, packet + j, 2); j += 2; x = ntohs(t_); } while (0)
987 #define GET8(x) do { if (j >= length) goto err; x = packet[j++]; } while (0)
988
989 char *cp = name_out;
990 const char *const end = name_out + name_out_len;
991
992 /* Normally, names are a series of length prefixed strings terminated */
993 /* with a length of 0 (the lengths are u8's < 63). */
994 /* However, the length can start with a pair of 1 bits and that */
995 /* means that the next 14 bits are a pointer within the current */
996 /* packet. */
997
998 for (;;) {
999 u8 label_len;
1000 GET8(label_len);
1001 if (!label_len) break;
1002 if (label_len & 0xc0) {
1003 u8 ptr_low;
1004 GET8(ptr_low);
1005 if (name_end < 0) name_end = j;
1006 j = (((int)label_len & 0x3f) << 8) + ptr_low;
1007 /* Make sure that the target offset is in-bounds. */
1008 if (j < 0 || j >= length) return -1;
1009 /* If we've jumped more times than there are characters in the
1010 * message, we must have a loop. */
1011 if (++ptr_count > length) return -1;
1012 continue;
1013 }
1014 if (label_len > 63) return -1;
1015 if (cp != name_out) {
1016 if (cp + 1 >= end) return -1;
1017 *cp++ = '.';
1018 }
1019 if (cp + label_len >= end) return -1;
1020 if (j + label_len > length) return -1;
1021 memcpy(cp, packet + j, label_len);
1022 cp += label_len;
1023 j += label_len;
1024 }
1025 if (cp >= end) return -1;
1026 *cp = '\0';
1027 if (name_end < 0)
1028 *idx = j;
1029 else
1030 *idx = name_end;
1031 return 0;
1032 err:
1033 return -1;
1034 }
1035
1036 /* parses a raw request from a nameserver */
1037 static int
reply_parse(struct evdns_base * base,u8 * packet,int length)1038 reply_parse(struct evdns_base *base, u8 *packet, int length) {
1039 int j = 0, k = 0; /* index into packet */
1040 u16 t_; /* used by the macros */
1041 u32 t32_; /* used by the macros */
1042 char tmp_name[256], cmp_name[256]; /* used by the macros */
1043 int name_matches = 0;
1044
1045 u16 trans_id, questions, answers, authority, additional, datalength;
1046 u16 flags = 0;
1047 u32 ttl, ttl_r = 0xffffffff;
1048 struct reply reply;
1049 struct request *req = NULL;
1050 unsigned int i;
1051
1052 ASSERT_LOCKED(base);
1053
1054 GET16(trans_id);
1055 GET16(flags);
1056 GET16(questions);
1057 GET16(answers);
1058 GET16(authority);
1059 GET16(additional);
1060 (void) authority; /* suppress "unused variable" warnings. */
1061 (void) additional; /* suppress "unused variable" warnings. */
1062
1063 req = request_find_from_trans_id(base, trans_id);
1064 if (!req) return -1;
1065 EVUTIL_ASSERT(req->base == base);
1066
1067 memset(&reply, 0, sizeof(reply));
1068
1069 /* If it's not an answer, it doesn't correspond to any request. */
1070 if (!(flags & _QR_MASK)) return -1; /* must be an answer */
1071 if ((flags & (_RCODE_MASK|_TC_MASK)) && (flags & (_RCODE_MASK|_TC_MASK)) != DNS_ERR_NOTEXIST) {
1072 /* there was an error and it's not NXDOMAIN */
1073 goto err;
1074 }
1075 /* if (!answers) return; */ /* must have an answer of some form */
1076
1077 /* This macro skips a name in the DNS reply. */
1078 #define SKIP_NAME \
1079 do { tmp_name[0] = '\0'; \
1080 if (name_parse(packet, length, &j, tmp_name, \
1081 sizeof(tmp_name))<0) \
1082 goto err; \
1083 } while (0)
1084
1085 reply.type = req->request_type;
1086
1087 /* skip over each question in the reply */
1088 for (i = 0; i < questions; ++i) {
1089 /* the question looks like
1090 * <label:name><u16:type><u16:class>
1091 */
1092 tmp_name[0] = '\0';
1093 cmp_name[0] = '\0';
1094 k = j;
1095 if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name)) < 0)
1096 goto err;
1097 if (name_parse(req->request, req->request_len, &k,
1098 cmp_name, sizeof(cmp_name))<0)
1099 goto err;
1100 if (!base->global_randomize_case) {
1101 if (strcmp(tmp_name, cmp_name) == 0)
1102 name_matches = 1;
1103 } else {
1104 if (evutil_ascii_strcasecmp(tmp_name, cmp_name) == 0)
1105 name_matches = 1;
1106 }
1107
1108 j += 4;
1109 if (j > length)
1110 goto err;
1111 }
1112
1113 if (!name_matches)
1114 goto err;
1115
1116 /* now we have the answer section which looks like
1117 * <label:name><u16:type><u16:class><u32:ttl><u16:len><data...>
1118 */
1119
1120 for (i = 0; i < answers; ++i) {
1121 u16 type, class;
1122
1123 SKIP_NAME;
1124 GET16(type);
1125 GET16(class);
1126 GET32(ttl);
1127 GET16(datalength);
1128
1129 if (type == TYPE_A && class == CLASS_INET) {
1130 int addrcount, addrtocopy;
1131 if (req->request_type != TYPE_A) {
1132 j += datalength; continue;
1133 }
1134 if ((datalength & 3) != 0) /* not an even number of As. */
1135 goto err;
1136 addrcount = datalength >> 2;
1137 addrtocopy = MIN(MAX_V4_ADDRS - reply.data.a.addrcount, (unsigned)addrcount);
1138
1139 ttl_r = MIN(ttl_r, ttl);
1140 /* we only bother with the first four addresses. */
1141 if (j + 4*addrtocopy > length) goto err;
1142 memcpy(&reply.data.a.addresses[reply.data.a.addrcount],
1143 packet + j, 4*addrtocopy);
1144 j += 4*addrtocopy;
1145 reply.data.a.addrcount += addrtocopy;
1146 reply.have_answer = 1;
1147 if (reply.data.a.addrcount == MAX_V4_ADDRS) break;
1148 } else if (type == TYPE_PTR && class == CLASS_INET) {
1149 if (req->request_type != TYPE_PTR) {
1150 j += datalength; continue;
1151 }
1152 if (name_parse(packet, length, &j, reply.data.ptr.name,
1153 sizeof(reply.data.ptr.name))<0)
1154 goto err;
1155 ttl_r = MIN(ttl_r, ttl);
1156 reply.have_answer = 1;
1157 break;
1158 } else if (type == TYPE_CNAME) {
1159 char cname[HOST_NAME_MAX];
1160 if (!req->put_cname_in_ptr || *req->put_cname_in_ptr) {
1161 j += datalength; continue;
1162 }
1163 if (name_parse(packet, length, &j, cname,
1164 sizeof(cname))<0)
1165 goto err;
1166 *req->put_cname_in_ptr = mm_strdup(cname);
1167 } else if (type == TYPE_AAAA && class == CLASS_INET) {
1168 int addrcount, addrtocopy;
1169 if (req->request_type != TYPE_AAAA) {
1170 j += datalength; continue;
1171 }
1172 if ((datalength & 15) != 0) /* not an even number of AAAAs. */
1173 goto err;
1174 addrcount = datalength >> 4; /* each address is 16 bytes long */
1175 addrtocopy = MIN(MAX_V6_ADDRS - reply.data.aaaa.addrcount, (unsigned)addrcount);
1176 ttl_r = MIN(ttl_r, ttl);
1177
1178 /* we only bother with the first four addresses. */
1179 if (j + 16*addrtocopy > length) goto err;
1180 memcpy(&reply.data.aaaa.addresses[reply.data.aaaa.addrcount],
1181 packet + j, 16*addrtocopy);
1182 reply.data.aaaa.addrcount += addrtocopy;
1183 j += 16*addrtocopy;
1184 reply.have_answer = 1;
1185 if (reply.data.aaaa.addrcount == MAX_V6_ADDRS) break;
1186 } else {
1187 /* skip over any other type of resource */
1188 j += datalength;
1189 }
1190 }
1191
1192 if (!reply.have_answer) {
1193 for (i = 0; i < authority; ++i) {
1194 u16 type, class;
1195 SKIP_NAME;
1196 GET16(type);
1197 GET16(class);
1198 GET32(ttl);
1199 GET16(datalength);
1200 if (type == TYPE_SOA && class == CLASS_INET) {
1201 u32 serial, refresh, retry, expire, minimum;
1202 SKIP_NAME;
1203 SKIP_NAME;
1204 GET32(serial);
1205 GET32(refresh);
1206 GET32(retry);
1207 GET32(expire);
1208 GET32(minimum);
1209 (void)expire;
1210 (void)retry;
1211 (void)refresh;
1212 (void)serial;
1213 ttl_r = MIN(ttl_r, ttl);
1214 ttl_r = MIN(ttl_r, minimum);
1215 } else {
1216 /* skip over any other type of resource */
1217 j += datalength;
1218 }
1219 }
1220 }
1221
1222 if (ttl_r == 0xffffffff)
1223 ttl_r = 0;
1224
1225 reply_handle(req, flags, ttl_r, &reply);
1226 return 0;
1227 err:
1228 if (req)
1229 reply_handle(req, flags, 0, NULL);
1230 return -1;
1231 }
1232
1233 /* Parse a raw request (packet,length) sent to a nameserver port (port) from */
1234 /* a DNS client (addr,addrlen), and if it's well-formed, call the corresponding */
1235 /* callback. */
1236 static int
request_parse(u8 * packet,int length,struct evdns_server_port * port,struct sockaddr * addr,ev_socklen_t addrlen)1237 request_parse(u8 *packet, int length, struct evdns_server_port *port, struct sockaddr *addr, ev_socklen_t addrlen)
1238 {
1239 int j = 0; /* index into packet */
1240 u16 t_; /* used by the macros */
1241 char tmp_name[256]; /* used by the macros */
1242
1243 int i;
1244 u16 trans_id, flags, questions, answers, authority, additional;
1245 struct server_request *server_req = NULL;
1246
1247 ASSERT_LOCKED(port);
1248
1249 /* Get the header fields */
1250 GET16(trans_id);
1251 GET16(flags);
1252 GET16(questions);
1253 GET16(answers);
1254 GET16(authority);
1255 GET16(additional);
1256 (void)answers;
1257 (void)additional;
1258 (void)authority;
1259
1260 if (flags & _QR_MASK) return -1; /* Must not be an answer. */
1261 flags &= (_RD_MASK|_CD_MASK); /* Only RD and CD get preserved. */
1262
1263 server_req = mm_malloc(sizeof(struct server_request));
1264 if (server_req == NULL) return -1;
1265 memset(server_req, 0, sizeof(struct server_request));
1266
1267 server_req->trans_id = trans_id;
1268 memcpy(&server_req->addr, addr, addrlen);
1269 server_req->addrlen = addrlen;
1270
1271 server_req->base.flags = flags;
1272 server_req->base.nquestions = 0;
1273 server_req->base.questions = mm_calloc(sizeof(struct evdns_server_question *), questions);
1274 if (server_req->base.questions == NULL)
1275 goto err;
1276
1277 for (i = 0; i < questions; ++i) {
1278 u16 type, class;
1279 struct evdns_server_question *q;
1280 int namelen;
1281 if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name))<0)
1282 goto err;
1283 GET16(type);
1284 GET16(class);
1285 namelen = (int)strlen(tmp_name);
1286 q = mm_malloc(sizeof(struct evdns_server_question) + namelen);
1287 if (!q)
1288 goto err;
1289 q->type = type;
1290 q->dns_question_class = class;
1291 memcpy(q->name, tmp_name, namelen+1);
1292 server_req->base.questions[server_req->base.nquestions++] = q;
1293 }
1294
1295 /* Ignore answers, authority, and additional. */
1296
1297 server_req->port = port;
1298 port->refcnt++;
1299
1300 /* Only standard queries are supported. */
1301 if (flags & _OP_MASK) {
1302 evdns_server_request_respond(&(server_req->base), DNS_ERR_NOTIMPL);
1303 return -1;
1304 }
1305
1306 port->user_callback(&(server_req->base), port->user_data);
1307
1308 return 0;
1309 err:
1310 if (server_req->base.questions) {
1311 for (i = 0; i < server_req->base.nquestions; ++i)
1312 mm_free(server_req->base.questions[i]);
1313 mm_free(server_req->base.questions);
1314 }
1315 mm_free(server_req);
1316 return -1;
1317
1318 #undef SKIP_NAME
1319 #undef GET32
1320 #undef GET16
1321 #undef GET8
1322 }
1323
1324
1325 void
evdns_set_transaction_id_fn(ev_uint16_t (* fn)(void))1326 evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void))
1327 {
1328 }
1329
1330 void
evdns_set_random_bytes_fn(void (* fn)(char *,size_t))1331 evdns_set_random_bytes_fn(void (*fn)(char *, size_t))
1332 {
1333 }
1334
1335 /* Try to choose a strong transaction id which isn't already in flight */
1336 static u16
transaction_id_pick(struct evdns_base * base)1337 transaction_id_pick(struct evdns_base *base) {
1338 ASSERT_LOCKED(base);
1339 for (;;) {
1340 u16 trans_id;
1341 evutil_secure_rng_get_bytes(&trans_id, sizeof(trans_id));
1342
1343 if (trans_id == 0xffff) continue;
1344 /* now check to see if that id is already inflight */
1345 if (request_find_from_trans_id(base, trans_id) == NULL)
1346 return trans_id;
1347 }
1348 }
1349
1350 /* choose a namesever to use. This function will try to ignore */
1351 /* nameservers which we think are down and load balance across the rest */
1352 /* by updating the server_head global each time. */
1353 static struct nameserver *
nameserver_pick(struct evdns_base * base)1354 nameserver_pick(struct evdns_base *base) {
1355 struct nameserver *started_at = base->server_head, *picked;
1356 ASSERT_LOCKED(base);
1357 if (!base->server_head) return NULL;
1358
1359 /* if we don't have any good nameservers then there's no */
1360 /* point in trying to find one. */
1361 if (!base->global_good_nameservers) {
1362 base->server_head = base->server_head->next;
1363 return base->server_head;
1364 }
1365
1366 /* remember that nameservers are in a circular list */
1367 for (;;) {
1368 if (base->server_head->state) {
1369 /* we think this server is currently good */
1370 picked = base->server_head;
1371 base->server_head = base->server_head->next;
1372 return picked;
1373 }
1374
1375 base->server_head = base->server_head->next;
1376 if (base->server_head == started_at) {
1377 /* all the nameservers seem to be down */
1378 /* so we just return this one and hope for the */
1379 /* best */
1380 EVUTIL_ASSERT(base->global_good_nameservers == 0);
1381 picked = base->server_head;
1382 base->server_head = base->server_head->next;
1383 return picked;
1384 }
1385 }
1386 }
1387
1388 /* this is called when a namesever socket is ready for reading */
1389 static void
nameserver_read(struct nameserver * ns)1390 nameserver_read(struct nameserver *ns) {
1391 struct sockaddr_storage ss;
1392 ev_socklen_t addrlen = sizeof(ss);
1393 u8 packet[1500];
1394 char addrbuf[128];
1395 ASSERT_LOCKED(ns->base);
1396
1397 for (;;) {
1398 const int r = recvfrom(ns->socket, (void*)packet,
1399 sizeof(packet), 0,
1400 (struct sockaddr*)&ss, &addrlen);
1401 if (r < 0) {
1402 int err = evutil_socket_geterror(ns->socket);
1403 if (EVUTIL_ERR_RW_RETRIABLE(err))
1404 return;
1405 nameserver_failed(ns,
1406 evutil_socket_error_to_string(err));
1407 return;
1408 }
1409 if (evutil_sockaddr_cmp((struct sockaddr*)&ss,
1410 (struct sockaddr*)&ns->address, 0)) {
1411 log(EVDNS_LOG_WARN, "Address mismatch on received "
1412 "DNS packet. Apparent source was %s",
1413 evutil_format_sockaddr_port_(
1414 (struct sockaddr *)&ss,
1415 addrbuf, sizeof(addrbuf)));
1416 return;
1417 }
1418
1419 ns->timedout = 0;
1420 reply_parse(ns->base, packet, r);
1421 }
1422 }
1423
1424 /* Read a packet from a DNS client on a server port s, parse it, and */
1425 /* act accordingly. */
1426 static void
server_port_read(struct evdns_server_port * s)1427 server_port_read(struct evdns_server_port *s) {
1428 u8 packet[1500];
1429 struct sockaddr_storage addr;
1430 ev_socklen_t addrlen;
1431 int r;
1432 ASSERT_LOCKED(s);
1433
1434 for (;;) {
1435 addrlen = sizeof(struct sockaddr_storage);
1436 r = recvfrom(s->socket, (void*)packet, sizeof(packet), 0,
1437 (struct sockaddr*) &addr, &addrlen);
1438 if (r < 0) {
1439 int err = evutil_socket_geterror(s->socket);
1440 if (EVUTIL_ERR_RW_RETRIABLE(err))
1441 return;
1442 log(EVDNS_LOG_WARN,
1443 "Error %s (%d) while reading request.",
1444 evutil_socket_error_to_string(err), err);
1445 return;
1446 }
1447 request_parse(packet, r, s, (struct sockaddr*) &addr, addrlen);
1448 }
1449 }
1450
1451 /* Try to write all pending replies on a given DNS server port. */
1452 static void
server_port_flush(struct evdns_server_port * port)1453 server_port_flush(struct evdns_server_port *port)
1454 {
1455 struct server_request *req = port->pending_replies;
1456 ASSERT_LOCKED(port);
1457 while (req) {
1458 int r = sendto(port->socket, req->response, (int)req->response_len, 0,
1459 (struct sockaddr*) &req->addr, (ev_socklen_t)req->addrlen);
1460 if (r < 0) {
1461 int err = evutil_socket_geterror(port->socket);
1462 if (EVUTIL_ERR_RW_RETRIABLE(err))
1463 return;
1464 log(EVDNS_LOG_WARN, "Error %s (%d) while writing response to port; dropping", evutil_socket_error_to_string(err), err);
1465 }
1466 if (server_request_free(req)) {
1467 /* we released the last reference to req->port. */
1468 return;
1469 } else {
1470 EVUTIL_ASSERT(req != port->pending_replies);
1471 req = port->pending_replies;
1472 }
1473 }
1474
1475 /* We have no more pending requests; stop listening for 'writeable' events. */
1476 (void) event_del(&port->event);
1477 event_assign(&port->event, port->event_base,
1478 port->socket, EV_READ | EV_PERSIST,
1479 server_port_ready_callback, port);
1480
1481 if (event_add(&port->event, NULL) < 0) {
1482 log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server.");
1483 /* ???? Do more? */
1484 }
1485 }
1486
1487 /* set if we are waiting for the ability to write to this server. */
1488 /* if waiting is true then we ask libevent for EV_WRITE events, otherwise */
1489 /* we stop these events. */
1490 static void
nameserver_write_waiting(struct nameserver * ns,char waiting)1491 nameserver_write_waiting(struct nameserver *ns, char waiting) {
1492 ASSERT_LOCKED(ns->base);
1493 if (ns->write_waiting == waiting) return;
1494
1495 ns->write_waiting = waiting;
1496 (void) event_del(&ns->event);
1497 event_assign(&ns->event, ns->base->event_base,
1498 ns->socket, EV_READ | (waiting ? EV_WRITE : 0) | EV_PERSIST,
1499 nameserver_ready_callback, ns);
1500 if (event_add(&ns->event, NULL) < 0) {
1501 char addrbuf[128];
1502 log(EVDNS_LOG_WARN, "Error from libevent when adding event for %s",
1503 evutil_format_sockaddr_port_(
1504 (struct sockaddr *)&ns->address,
1505 addrbuf, sizeof(addrbuf)));
1506 /* ???? Do more? */
1507 }
1508 }
1509
1510 /* a callback function. Called by libevent when the kernel says that */
1511 /* a nameserver socket is ready for writing or reading */
1512 static void
nameserver_ready_callback(evutil_socket_t fd,short events,void * arg)1513 nameserver_ready_callback(evutil_socket_t fd, short events, void *arg) {
1514 struct nameserver *ns = (struct nameserver *) arg;
1515 (void)fd;
1516
1517 EVDNS_LOCK(ns->base);
1518 if (events & EV_WRITE) {
1519 ns->choked = 0;
1520 if (!evdns_transmit(ns->base)) {
1521 nameserver_write_waiting(ns, 0);
1522 }
1523 }
1524 if (events & EV_READ) {
1525 nameserver_read(ns);
1526 }
1527 EVDNS_UNLOCK(ns->base);
1528 }
1529
1530 /* a callback function. Called by libevent when the kernel says that */
1531 /* a server socket is ready for writing or reading. */
1532 static void
server_port_ready_callback(evutil_socket_t fd,short events,void * arg)1533 server_port_ready_callback(evutil_socket_t fd, short events, void *arg) {
1534 struct evdns_server_port *port = (struct evdns_server_port *) arg;
1535 (void) fd;
1536
1537 EVDNS_LOCK(port);
1538 if (events & EV_WRITE) {
1539 port->choked = 0;
1540 server_port_flush(port);
1541 }
1542 if (events & EV_READ) {
1543 server_port_read(port);
1544 }
1545 EVDNS_UNLOCK(port);
1546 }
1547
1548 /* This is an inefficient representation; only use it via the dnslabel_table_*
1549 * functions, so that is can be safely replaced with something smarter later. */
1550 #define MAX_LABELS 128
1551 /* Structures used to implement name compression */
1552 struct dnslabel_entry { char *v; off_t pos; };
1553 struct dnslabel_table {
1554 int n_labels; /* number of current entries */
1555 /* map from name to position in message */
1556 struct dnslabel_entry labels[MAX_LABELS];
1557 };
1558
1559 /* Initialize dnslabel_table. */
1560 static void
dnslabel_table_init(struct dnslabel_table * table)1561 dnslabel_table_init(struct dnslabel_table *table)
1562 {
1563 table->n_labels = 0;
1564 }
1565
1566 /* Free all storage held by table, but not the table itself. */
1567 static void
dnslabel_clear(struct dnslabel_table * table)1568 dnslabel_clear(struct dnslabel_table *table)
1569 {
1570 int i;
1571 for (i = 0; i < table->n_labels; ++i)
1572 mm_free(table->labels[i].v);
1573 table->n_labels = 0;
1574 }
1575
1576 /* return the position of the label in the current message, or -1 if the label */
1577 /* hasn't been used yet. */
1578 static int
dnslabel_table_get_pos(const struct dnslabel_table * table,const char * label)1579 dnslabel_table_get_pos(const struct dnslabel_table *table, const char *label)
1580 {
1581 int i;
1582 for (i = 0; i < table->n_labels; ++i) {
1583 if (!strcmp(label, table->labels[i].v))
1584 return table->labels[i].pos;
1585 }
1586 return -1;
1587 }
1588
1589 /* remember that we've used the label at position pos */
1590 static int
dnslabel_table_add(struct dnslabel_table * table,const char * label,off_t pos)1591 dnslabel_table_add(struct dnslabel_table *table, const char *label, off_t pos)
1592 {
1593 char *v;
1594 int p;
1595 if (table->n_labels == MAX_LABELS)
1596 return (-1);
1597 v = mm_strdup(label);
1598 if (v == NULL)
1599 return (-1);
1600 p = table->n_labels++;
1601 table->labels[p].v = v;
1602 table->labels[p].pos = pos;
1603
1604 return (0);
1605 }
1606
1607 /* Converts a string to a length-prefixed set of DNS labels, starting */
1608 /* at buf[j]. name and buf must not overlap. name_len should be the length */
1609 /* of name. table is optional, and is used for compression. */
1610 /* */
1611 /* Input: abc.def */
1612 /* Output: <3>abc<3>def<0> */
1613 /* */
1614 /* Returns the first index after the encoded name, or negative on error. */
1615 /* -1 label was > 63 bytes */
1616 /* -2 name too long to fit in buffer. */
1617 /* */
1618 static off_t
dnsname_to_labels(u8 * const buf,size_t buf_len,off_t j,const char * name,const size_t name_len,struct dnslabel_table * table)1619 dnsname_to_labels(u8 *const buf, size_t buf_len, off_t j,
1620 const char *name, const size_t name_len,
1621 struct dnslabel_table *table) {
1622 const char *end = name + name_len;
1623 int ref = 0;
1624 u16 t_;
1625
1626 #define APPEND16(x) do { \
1627 if (j + 2 > (off_t)buf_len) \
1628 goto overflow; \
1629 t_ = htons(x); \
1630 memcpy(buf + j, &t_, 2); \
1631 j += 2; \
1632 } while (0)
1633 #define APPEND32(x) do { \
1634 if (j + 4 > (off_t)buf_len) \
1635 goto overflow; \
1636 t32_ = htonl(x); \
1637 memcpy(buf + j, &t32_, 4); \
1638 j += 4; \
1639 } while (0)
1640
1641 if (name_len > 255) return -2;
1642
1643 for (;;) {
1644 const char *const start = name;
1645 if (table && (ref = dnslabel_table_get_pos(table, name)) >= 0) {
1646 APPEND16(ref | 0xc000);
1647 return j;
1648 }
1649 name = strchr(name, '.');
1650 if (!name) {
1651 const size_t label_len = end - start;
1652 if (label_len > 63) return -1;
1653 if ((size_t)(j+label_len+1) > buf_len) return -2;
1654 if (table) dnslabel_table_add(table, start, j);
1655 buf[j++] = (ev_uint8_t)label_len;
1656
1657 memcpy(buf + j, start, label_len);
1658 j += (int) label_len;
1659 break;
1660 } else {
1661 /* append length of the label. */
1662 const size_t label_len = name - start;
1663 if (label_len > 63) return -1;
1664 if ((size_t)(j+label_len+1) > buf_len) return -2;
1665 if (table) dnslabel_table_add(table, start, j);
1666 buf[j++] = (ev_uint8_t)label_len;
1667
1668 memcpy(buf + j, start, label_len);
1669 j += (int) label_len;
1670 /* hop over the '.' */
1671 name++;
1672 }
1673 }
1674
1675 /* the labels must be terminated by a 0. */
1676 /* It's possible that the name ended in a . */
1677 /* in which case the zero is already there */
1678 if (!j || buf[j-1]) buf[j++] = 0;
1679 return j;
1680 overflow:
1681 return (-2);
1682 }
1683
1684 /* Finds the length of a dns request for a DNS name of the given */
1685 /* length. The actual request may be smaller than the value returned */
1686 /* here */
1687 static size_t
evdns_request_len(const size_t name_len)1688 evdns_request_len(const size_t name_len) {
1689 return 96 + /* length of the DNS standard header */
1690 name_len + 2 +
1691 4; /* space for the resource type */
1692 }
1693
1694 /* build a dns request packet into buf. buf should be at least as long */
1695 /* as evdns_request_len told you it should be. */
1696 /* */
1697 /* Returns the amount of space used. Negative on error. */
1698 static int
evdns_request_data_build(const char * const name,const size_t name_len,const u16 trans_id,const u16 type,const u16 class,u8 * const buf,size_t buf_len)1699 evdns_request_data_build(const char *const name, const size_t name_len,
1700 const u16 trans_id, const u16 type, const u16 class,
1701 u8 *const buf, size_t buf_len) {
1702 off_t j = 0; /* current offset into buf */
1703 u16 t_; /* used by the macros */
1704
1705 APPEND16(trans_id);
1706 APPEND16(0x0100); /* standard query, recusion needed */
1707 APPEND16(1); /* one question */
1708 APPEND16(0); /* no answers */
1709 APPEND16(0); /* no authority */
1710 APPEND16(0); /* no additional */
1711
1712 j = dnsname_to_labels(buf, buf_len, j, name, name_len, NULL);
1713 if (j < 0) {
1714 return (int)j;
1715 }
1716
1717 APPEND16(type);
1718 APPEND16(class);
1719
1720 return (int)j;
1721 overflow:
1722 return (-1);
1723 }
1724
1725 /* exported function */
1726 struct evdns_server_port *
evdns_add_server_port_with_base(struct event_base * base,evutil_socket_t socket,int flags,evdns_request_callback_fn_type cb,void * user_data)1727 evdns_add_server_port_with_base(struct event_base *base, evutil_socket_t socket, int flags, evdns_request_callback_fn_type cb, void *user_data)
1728 {
1729 struct evdns_server_port *port;
1730 if (flags)
1731 return NULL; /* flags not yet implemented */
1732 if (!(port = mm_malloc(sizeof(struct evdns_server_port))))
1733 return NULL;
1734 memset(port, 0, sizeof(struct evdns_server_port));
1735
1736
1737 port->socket = socket;
1738 port->refcnt = 1;
1739 port->choked = 0;
1740 port->closing = 0;
1741 port->user_callback = cb;
1742 port->user_data = user_data;
1743 port->pending_replies = NULL;
1744 port->event_base = base;
1745
1746 event_assign(&port->event, port->event_base,
1747 port->socket, EV_READ | EV_PERSIST,
1748 server_port_ready_callback, port);
1749 if (event_add(&port->event, NULL) < 0) {
1750 mm_free(port);
1751 return NULL;
1752 }
1753 EVTHREAD_ALLOC_LOCK(port->lock, EVTHREAD_LOCKTYPE_RECURSIVE);
1754 return port;
1755 }
1756
1757 struct evdns_server_port *
evdns_add_server_port(evutil_socket_t socket,int flags,evdns_request_callback_fn_type cb,void * user_data)1758 evdns_add_server_port(evutil_socket_t socket, int flags, evdns_request_callback_fn_type cb, void *user_data)
1759 {
1760 return evdns_add_server_port_with_base(NULL, socket, flags, cb, user_data);
1761 }
1762
1763 /* exported function */
1764 void
evdns_close_server_port(struct evdns_server_port * port)1765 evdns_close_server_port(struct evdns_server_port *port)
1766 {
1767 EVDNS_LOCK(port);
1768 if (--port->refcnt == 0) {
1769 EVDNS_UNLOCK(port);
1770 server_port_free(port);
1771 } else {
1772 port->closing = 1;
1773 EVDNS_UNLOCK(port);
1774 }
1775 }
1776
1777 /* exported function */
1778 int
evdns_server_request_add_reply(struct evdns_server_request * req_,int section,const char * name,int type,int class,int ttl,int datalen,int is_name,const char * data)1779 evdns_server_request_add_reply(struct evdns_server_request *req_, int section, const char *name, int type, int class, int ttl, int datalen, int is_name, const char *data)
1780 {
1781 struct server_request *req = TO_SERVER_REQUEST(req_);
1782 struct server_reply_item **itemp, *item;
1783 int *countp;
1784 int result = -1;
1785
1786 EVDNS_LOCK(req->port);
1787 if (req->response) /* have we already answered? */
1788 goto done;
1789
1790 switch (section) {
1791 case EVDNS_ANSWER_SECTION:
1792 itemp = &req->answer;
1793 countp = &req->n_answer;
1794 break;
1795 case EVDNS_AUTHORITY_SECTION:
1796 itemp = &req->authority;
1797 countp = &req->n_authority;
1798 break;
1799 case EVDNS_ADDITIONAL_SECTION:
1800 itemp = &req->additional;
1801 countp = &req->n_additional;
1802 break;
1803 default:
1804 goto done;
1805 }
1806 while (*itemp) {
1807 itemp = &((*itemp)->next);
1808 }
1809 item = mm_malloc(sizeof(struct server_reply_item));
1810 if (!item)
1811 goto done;
1812 item->next = NULL;
1813 if (!(item->name = mm_strdup(name))) {
1814 mm_free(item);
1815 goto done;
1816 }
1817 item->type = type;
1818 item->dns_question_class = class;
1819 item->ttl = ttl;
1820 item->is_name = is_name != 0;
1821 item->datalen = 0;
1822 item->data = NULL;
1823 if (data) {
1824 if (item->is_name) {
1825 if (!(item->data = mm_strdup(data))) {
1826 mm_free(item->name);
1827 mm_free(item);
1828 goto done;
1829 }
1830 item->datalen = (u16)-1;
1831 } else {
1832 if (!(item->data = mm_malloc(datalen))) {
1833 mm_free(item->name);
1834 mm_free(item);
1835 goto done;
1836 }
1837 item->datalen = datalen;
1838 memcpy(item->data, data, datalen);
1839 }
1840 }
1841
1842 *itemp = item;
1843 ++(*countp);
1844 result = 0;
1845 done:
1846 EVDNS_UNLOCK(req->port);
1847 return result;
1848 }
1849
1850 /* exported function */
1851 int
evdns_server_request_add_a_reply(struct evdns_server_request * req,const char * name,int n,const void * addrs,int ttl)1852 evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl)
1853 {
1854 return evdns_server_request_add_reply(
1855 req, EVDNS_ANSWER_SECTION, name, TYPE_A, CLASS_INET,
1856 ttl, n*4, 0, addrs);
1857 }
1858
1859 /* exported function */
1860 int
evdns_server_request_add_aaaa_reply(struct evdns_server_request * req,const char * name,int n,const void * addrs,int ttl)1861 evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl)
1862 {
1863 return evdns_server_request_add_reply(
1864 req, EVDNS_ANSWER_SECTION, name, TYPE_AAAA, CLASS_INET,
1865 ttl, n*16, 0, addrs);
1866 }
1867
1868 /* exported function */
1869 int
evdns_server_request_add_ptr_reply(struct evdns_server_request * req,struct in_addr * in,const char * inaddr_name,const char * hostname,int ttl)1870 evdns_server_request_add_ptr_reply(struct evdns_server_request *req, struct in_addr *in, const char *inaddr_name, const char *hostname, int ttl)
1871 {
1872 u32 a;
1873 char buf[32];
1874 if (in && inaddr_name)
1875 return -1;
1876 else if (!in && !inaddr_name)
1877 return -1;
1878 if (in) {
1879 a = ntohl(in->s_addr);
1880 evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa",
1881 (int)(u8)((a )&0xff),
1882 (int)(u8)((a>>8 )&0xff),
1883 (int)(u8)((a>>16)&0xff),
1884 (int)(u8)((a>>24)&0xff));
1885 inaddr_name = buf;
1886 }
1887 return evdns_server_request_add_reply(
1888 req, EVDNS_ANSWER_SECTION, inaddr_name, TYPE_PTR, CLASS_INET,
1889 ttl, -1, 1, hostname);
1890 }
1891
1892 /* exported function */
1893 int
evdns_server_request_add_cname_reply(struct evdns_server_request * req,const char * name,const char * cname,int ttl)1894 evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl)
1895 {
1896 return evdns_server_request_add_reply(
1897 req, EVDNS_ANSWER_SECTION, name, TYPE_CNAME, CLASS_INET,
1898 ttl, -1, 1, cname);
1899 }
1900
1901 /* exported function */
1902 void
evdns_server_request_set_flags(struct evdns_server_request * exreq,int flags)1903 evdns_server_request_set_flags(struct evdns_server_request *exreq, int flags)
1904 {
1905 struct server_request *req = TO_SERVER_REQUEST(exreq);
1906 req->base.flags &= ~(EVDNS_FLAGS_AA|EVDNS_FLAGS_RD);
1907 req->base.flags |= flags;
1908 }
1909
1910 static int
evdns_server_request_format_response(struct server_request * req,int err)1911 evdns_server_request_format_response(struct server_request *req, int err)
1912 {
1913 unsigned char buf[1500];
1914 size_t buf_len = sizeof(buf);
1915 off_t j = 0, r;
1916 u16 t_;
1917 u32 t32_;
1918 int i;
1919 u16 flags;
1920 struct dnslabel_table table;
1921
1922 if (err < 0 || err > 15) return -1;
1923
1924 /* Set response bit and error code; copy OPCODE and RD fields from
1925 * question; copy RA and AA if set by caller. */
1926 flags = req->base.flags;
1927 flags |= (_QR_MASK | err);
1928
1929 dnslabel_table_init(&table);
1930 APPEND16(req->trans_id);
1931 APPEND16(flags);
1932 APPEND16(req->base.nquestions);
1933 APPEND16(req->n_answer);
1934 APPEND16(req->n_authority);
1935 APPEND16(req->n_additional);
1936
1937 /* Add questions. */
1938 for (i=0; i < req->base.nquestions; ++i) {
1939 const char *s = req->base.questions[i]->name;
1940 j = dnsname_to_labels(buf, buf_len, j, s, strlen(s), &table);
1941 if (j < 0) {
1942 dnslabel_clear(&table);
1943 return (int) j;
1944 }
1945 APPEND16(req->base.questions[i]->type);
1946 APPEND16(req->base.questions[i]->dns_question_class);
1947 }
1948
1949 /* Add answer, authority, and additional sections. */
1950 for (i=0; i<3; ++i) {
1951 struct server_reply_item *item;
1952 if (i==0)
1953 item = req->answer;
1954 else if (i==1)
1955 item = req->authority;
1956 else
1957 item = req->additional;
1958 while (item) {
1959 r = dnsname_to_labels(buf, buf_len, j, item->name, strlen(item->name), &table);
1960 if (r < 0)
1961 goto overflow;
1962 j = r;
1963
1964 APPEND16(item->type);
1965 APPEND16(item->dns_question_class);
1966 APPEND32(item->ttl);
1967 if (item->is_name) {
1968 off_t len_idx = j, name_start;
1969 j += 2;
1970 name_start = j;
1971 r = dnsname_to_labels(buf, buf_len, j, item->data, strlen(item->data), &table);
1972 if (r < 0)
1973 goto overflow;
1974 j = r;
1975 t_ = htons( (short) (j-name_start) );
1976 memcpy(buf+len_idx, &t_, 2);
1977 } else {
1978 APPEND16(item->datalen);
1979 if (j+item->datalen > (off_t)buf_len)
1980 goto overflow;
1981 memcpy(buf+j, item->data, item->datalen);
1982 j += item->datalen;
1983 }
1984 item = item->next;
1985 }
1986 }
1987
1988 if (j > 512) {
1989 overflow:
1990 j = 512;
1991 buf[2] |= 0x02; /* set the truncated bit. */
1992 }
1993
1994 req->response_len = j;
1995
1996 if (!(req->response = mm_malloc(req->response_len))) {
1997 server_request_free_answers(req);
1998 dnslabel_clear(&table);
1999 return (-1);
2000 }
2001 memcpy(req->response, buf, req->response_len);
2002 server_request_free_answers(req);
2003 dnslabel_clear(&table);
2004 return (0);
2005 }
2006
2007 /* exported function */
2008 int
evdns_server_request_respond(struct evdns_server_request * req_,int err)2009 evdns_server_request_respond(struct evdns_server_request *req_, int err)
2010 {
2011 struct server_request *req = TO_SERVER_REQUEST(req_);
2012 struct evdns_server_port *port = req->port;
2013 int r = -1;
2014
2015 EVDNS_LOCK(port);
2016 if (!req->response) {
2017 if ((r = evdns_server_request_format_response(req, err))<0)
2018 goto done;
2019 }
2020
2021 r = sendto(port->socket, req->response, (int)req->response_len, 0,
2022 (struct sockaddr*) &req->addr, (ev_socklen_t)req->addrlen);
2023 if (r<0) {
2024 int sock_err = evutil_socket_geterror(port->socket);
2025 if (EVUTIL_ERR_RW_RETRIABLE(sock_err))
2026 goto done;
2027
2028 if (port->pending_replies) {
2029 req->prev_pending = port->pending_replies->prev_pending;
2030 req->next_pending = port->pending_replies;
2031 req->prev_pending->next_pending =
2032 req->next_pending->prev_pending = req;
2033 } else {
2034 req->prev_pending = req->next_pending = req;
2035 port->pending_replies = req;
2036 port->choked = 1;
2037
2038 (void) event_del(&port->event);
2039 event_assign(&port->event, port->event_base, port->socket, (port->closing?0:EV_READ) | EV_WRITE | EV_PERSIST, server_port_ready_callback, port);
2040
2041 if (event_add(&port->event, NULL) < 0) {
2042 log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server");
2043 }
2044
2045 }
2046
2047 r = 1;
2048 goto done;
2049 }
2050 if (server_request_free(req)) {
2051 r = 0;
2052 goto done;
2053 }
2054
2055 if (port->pending_replies)
2056 server_port_flush(port);
2057
2058 r = 0;
2059 done:
2060 EVDNS_UNLOCK(port);
2061 return r;
2062 }
2063
2064 /* Free all storage held by RRs in req. */
2065 static void
server_request_free_answers(struct server_request * req)2066 server_request_free_answers(struct server_request *req)
2067 {
2068 struct server_reply_item *victim, *next, **list;
2069 int i;
2070 for (i = 0; i < 3; ++i) {
2071 if (i==0)
2072 list = &req->answer;
2073 else if (i==1)
2074 list = &req->authority;
2075 else
2076 list = &req->additional;
2077
2078 victim = *list;
2079 while (victim) {
2080 next = victim->next;
2081 mm_free(victim->name);
2082 if (victim->data)
2083 mm_free(victim->data);
2084 mm_free(victim);
2085 victim = next;
2086 }
2087 *list = NULL;
2088 }
2089 }
2090
2091 /* Free all storage held by req, and remove links to it. */
2092 /* return true iff we just wound up freeing the server_port. */
2093 static int
server_request_free(struct server_request * req)2094 server_request_free(struct server_request *req)
2095 {
2096 int i, rc=1, lock=0;
2097 if (req->base.questions) {
2098 for (i = 0; i < req->base.nquestions; ++i)
2099 mm_free(req->base.questions[i]);
2100 mm_free(req->base.questions);
2101 }
2102
2103 if (req->port) {
2104 EVDNS_LOCK(req->port);
2105 lock=1;
2106 if (req->port->pending_replies == req) {
2107 if (req->next_pending && req->next_pending != req)
2108 req->port->pending_replies = req->next_pending;
2109 else
2110 req->port->pending_replies = NULL;
2111 }
2112 rc = --req->port->refcnt;
2113 }
2114
2115 if (req->response) {
2116 mm_free(req->response);
2117 }
2118
2119 server_request_free_answers(req);
2120
2121 if (req->next_pending && req->next_pending != req) {
2122 req->next_pending->prev_pending = req->prev_pending;
2123 req->prev_pending->next_pending = req->next_pending;
2124 }
2125
2126 if (rc == 0) {
2127 EVDNS_UNLOCK(req->port); /* ????? nickm */
2128 server_port_free(req->port);
2129 mm_free(req);
2130 return (1);
2131 }
2132 if (lock)
2133 EVDNS_UNLOCK(req->port);
2134 mm_free(req);
2135 return (0);
2136 }
2137
2138 /* Free all storage held by an evdns_server_port. Only called when */
2139 static void
server_port_free(struct evdns_server_port * port)2140 server_port_free(struct evdns_server_port *port)
2141 {
2142 EVUTIL_ASSERT(port);
2143 EVUTIL_ASSERT(!port->refcnt);
2144 EVUTIL_ASSERT(!port->pending_replies);
2145 if (port->socket > 0) {
2146 evutil_closesocket(port->socket);
2147 port->socket = -1;
2148 }
2149 (void) event_del(&port->event);
2150 event_debug_unassign(&port->event);
2151 EVTHREAD_FREE_LOCK(port->lock, EVTHREAD_LOCKTYPE_RECURSIVE);
2152 mm_free(port);
2153 }
2154
2155 /* exported function */
2156 int
evdns_server_request_drop(struct evdns_server_request * req_)2157 evdns_server_request_drop(struct evdns_server_request *req_)
2158 {
2159 struct server_request *req = TO_SERVER_REQUEST(req_);
2160 server_request_free(req);
2161 return 0;
2162 }
2163
2164 /* exported function */
2165 int
evdns_server_request_get_requesting_addr(struct evdns_server_request * req_,struct sockaddr * sa,int addr_len)2166 evdns_server_request_get_requesting_addr(struct evdns_server_request *req_, struct sockaddr *sa, int addr_len)
2167 {
2168 struct server_request *req = TO_SERVER_REQUEST(req_);
2169 if (addr_len < (int)req->addrlen)
2170 return -1;
2171 memcpy(sa, &(req->addr), req->addrlen);
2172 return req->addrlen;
2173 }
2174
2175 #undef APPEND16
2176 #undef APPEND32
2177
2178 /* this is a libevent callback function which is called when a request */
2179 /* has timed out. */
2180 static void
evdns_request_timeout_callback(evutil_socket_t fd,short events,void * arg)2181 evdns_request_timeout_callback(evutil_socket_t fd, short events, void *arg) {
2182 struct request *const req = (struct request *) arg;
2183 struct evdns_base *base = req->base;
2184
2185 (void) fd;
2186 (void) events;
2187
2188 log(EVDNS_LOG_DEBUG, "Request %p timed out", arg);
2189 EVDNS_LOCK(base);
2190
2191 if (req->tx_count >= req->base->global_max_retransmits) {
2192 struct nameserver *ns = req->ns;
2193 /* this request has failed */
2194 log(EVDNS_LOG_DEBUG, "Giving up on request %p; tx_count==%d",
2195 arg, req->tx_count);
2196 reply_schedule_callback(req, 0, DNS_ERR_TIMEOUT, NULL);
2197
2198 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1);
2199 nameserver_failed(ns, "request timed out.");
2200 } else {
2201 /* retransmit it */
2202 log(EVDNS_LOG_DEBUG, "Retransmitting request %p; tx_count==%d",
2203 arg, req->tx_count);
2204 (void) evtimer_del(&req->timeout_event);
2205 request_swap_ns(req, nameserver_pick(base));
2206 evdns_request_transmit(req);
2207
2208 req->ns->timedout++;
2209 if (req->ns->timedout > req->base->global_max_nameserver_timeout) {
2210 req->ns->timedout = 0;
2211 nameserver_failed(req->ns, "request timed out.");
2212 }
2213 }
2214
2215 EVDNS_UNLOCK(base);
2216 }
2217
2218 /* try to send a request to a given server. */
2219 /* */
2220 /* return: */
2221 /* 0 ok */
2222 /* 1 temporary failure */
2223 /* 2 other failure */
2224 static int
evdns_request_transmit_to(struct request * req,struct nameserver * server)2225 evdns_request_transmit_to(struct request *req, struct nameserver *server) {
2226 int r;
2227 ASSERT_LOCKED(req->base);
2228 ASSERT_VALID_REQUEST(req);
2229
2230 if (server->requests_inflight == 1 &&
2231 req->base->disable_when_inactive &&
2232 event_add(&server->event, NULL) < 0) {
2233 return 1;
2234 }
2235
2236 r = sendto(server->socket, (void*)req->request, req->request_len, 0,
2237 (struct sockaddr *)&server->address, server->addrlen);
2238 if (r < 0) {
2239 int err = evutil_socket_geterror(server->socket);
2240 if (EVUTIL_ERR_RW_RETRIABLE(err))
2241 return 1;
2242 nameserver_failed(req->ns, evutil_socket_error_to_string(err));
2243 return 2;
2244 } else if (r != (int)req->request_len) {
2245 return 1; /* short write */
2246 } else {
2247 return 0;
2248 }
2249 }
2250
2251 /* try to send a request, updating the fields of the request */
2252 /* as needed */
2253 /* */
2254 /* return: */
2255 /* 0 ok */
2256 /* 1 failed */
2257 static int
evdns_request_transmit(struct request * req)2258 evdns_request_transmit(struct request *req) {
2259 int retcode = 0, r;
2260
2261 ASSERT_LOCKED(req->base);
2262 ASSERT_VALID_REQUEST(req);
2263 /* if we fail to send this packet then this flag marks it */
2264 /* for evdns_transmit */
2265 req->transmit_me = 1;
2266 EVUTIL_ASSERT(req->trans_id != 0xffff);
2267
2268 if (!req->ns)
2269 {
2270 /* unable to transmit request if no nameservers */
2271 return 1;
2272 }
2273
2274 if (req->ns->choked) {
2275 /* don't bother trying to write to a socket */
2276 /* which we have had EAGAIN from */
2277 return 1;
2278 }
2279
2280 r = evdns_request_transmit_to(req, req->ns);
2281 switch (r) {
2282 case 1:
2283 /* temp failure */
2284 req->ns->choked = 1;
2285 nameserver_write_waiting(req->ns, 1);
2286 return 1;
2287 case 2:
2288 /* failed to transmit the request entirely. we can fallthrough since
2289 * we'll set a timeout, which will time out, and make us retransmit the
2290 * request anyway. */
2291 retcode = 1;
2292 EVUTIL_FALLTHROUGH;
2293 default:
2294 /* all ok */
2295 log(EVDNS_LOG_DEBUG,
2296 "Setting timeout for request %p, sent to nameserver %p", req, req->ns);
2297 if (evtimer_add(&req->timeout_event, &req->base->global_timeout) < 0) {
2298 log(EVDNS_LOG_WARN,
2299 "Error from libevent when adding timer for request %p",
2300 req);
2301 /* ???? Do more? */
2302 }
2303 req->tx_count++;
2304 req->transmit_me = 0;
2305 return retcode;
2306 }
2307 }
2308
2309 static void
nameserver_probe_callback(int result,char type,int count,int ttl,void * addresses,void * arg)2310 nameserver_probe_callback(int result, char type, int count, int ttl, void *addresses, void *arg) {
2311 struct nameserver *const ns = (struct nameserver *) arg;
2312 (void) type;
2313 (void) count;
2314 (void) ttl;
2315 (void) addresses;
2316
2317 if (result == DNS_ERR_CANCEL) {
2318 /* We canceled this request because the nameserver came up
2319 * for some other reason. Do not change our opinion about
2320 * the nameserver. */
2321 return;
2322 }
2323
2324 EVDNS_LOCK(ns->base);
2325 ns->probe_request = NULL;
2326 if (result == DNS_ERR_NONE || result == DNS_ERR_NOTEXIST) {
2327 /* this is a good reply */
2328 nameserver_up(ns);
2329 } else {
2330 nameserver_probe_failed(ns);
2331 }
2332 EVDNS_UNLOCK(ns->base);
2333 }
2334
2335 static void
nameserver_send_probe(struct nameserver * const ns)2336 nameserver_send_probe(struct nameserver *const ns) {
2337 struct evdns_request *handle;
2338 struct request *req;
2339 char addrbuf[128];
2340 /* here we need to send a probe to a given nameserver */
2341 /* in the hope that it is up now. */
2342
2343 ASSERT_LOCKED(ns->base);
2344 log(EVDNS_LOG_DEBUG, "Sending probe to %s",
2345 evutil_format_sockaddr_port_(
2346 (struct sockaddr *)&ns->address,
2347 addrbuf, sizeof(addrbuf)));
2348 handle = mm_calloc(1, sizeof(*handle));
2349 if (!handle) return;
2350 req = request_new(ns->base, handle, TYPE_A, "google.com", DNS_QUERY_NO_SEARCH, nameserver_probe_callback, ns);
2351 if (!req) {
2352 mm_free(handle);
2353 return;
2354 }
2355 ns->probe_request = handle;
2356 /* we force this into the inflight queue no matter what */
2357 request_trans_id_set(req, transaction_id_pick(ns->base));
2358 req->ns = ns;
2359 request_submit(req);
2360 }
2361
2362 /* returns: */
2363 /* 0 didn't try to transmit anything */
2364 /* 1 tried to transmit something */
2365 static int
evdns_transmit(struct evdns_base * base)2366 evdns_transmit(struct evdns_base *base) {
2367 char did_try_to_transmit = 0;
2368 int i;
2369
2370 ASSERT_LOCKED(base);
2371 for (i = 0; i < base->n_req_heads; ++i) {
2372 if (base->req_heads[i]) {
2373 struct request *const started_at = base->req_heads[i], *req = started_at;
2374 /* first transmit all the requests which are currently waiting */
2375 do {
2376 if (req->transmit_me) {
2377 did_try_to_transmit = 1;
2378 evdns_request_transmit(req);
2379 }
2380
2381 req = req->next;
2382 } while (req != started_at);
2383 }
2384 }
2385
2386 return did_try_to_transmit;
2387 }
2388
2389 /* exported function */
2390 int
evdns_base_count_nameservers(struct evdns_base * base)2391 evdns_base_count_nameservers(struct evdns_base *base)
2392 {
2393 const struct nameserver *server;
2394 int n = 0;
2395
2396 EVDNS_LOCK(base);
2397 server = base->server_head;
2398 if (!server)
2399 goto done;
2400 do {
2401 ++n;
2402 server = server->next;
2403 } while (server != base->server_head);
2404 done:
2405 EVDNS_UNLOCK(base);
2406 return n;
2407 }
2408
2409 int
evdns_count_nameservers(void)2410 evdns_count_nameservers(void)
2411 {
2412 return evdns_base_count_nameservers(current_base);
2413 }
2414
2415 /* exported function */
2416 int
evdns_base_clear_nameservers_and_suspend(struct evdns_base * base)2417 evdns_base_clear_nameservers_and_suspend(struct evdns_base *base)
2418 {
2419 struct nameserver *server, *started_at;
2420 int i;
2421
2422 EVDNS_LOCK(base);
2423 server = base->server_head;
2424 started_at = base->server_head;
2425 if (!server) {
2426 EVDNS_UNLOCK(base);
2427 return 0;
2428 }
2429 while (1) {
2430 struct nameserver *next = server->next;
2431 (void) event_del(&server->event);
2432 if (evtimer_initialized(&server->timeout_event))
2433 (void) evtimer_del(&server->timeout_event);
2434 if (server->probe_request) {
2435 evdns_cancel_request(server->base, server->probe_request);
2436 server->probe_request = NULL;
2437 }
2438 if (server->socket >= 0)
2439 evutil_closesocket(server->socket);
2440 mm_free(server);
2441 if (next == started_at)
2442 break;
2443 server = next;
2444 }
2445 base->server_head = NULL;
2446 base->global_good_nameservers = 0;
2447
2448 for (i = 0; i < base->n_req_heads; ++i) {
2449 struct request *req, *req_started_at;
2450 req = req_started_at = base->req_heads[i];
2451 while (req) {
2452 struct request *next = req->next;
2453 req->tx_count = req->reissue_count = 0;
2454 req->ns = NULL;
2455 /* ???? What to do about searches? */
2456 (void) evtimer_del(&req->timeout_event);
2457 req->trans_id = 0;
2458 req->transmit_me = 0;
2459
2460 base->global_requests_waiting++;
2461 evdns_request_insert(req, &base->req_waiting_head);
2462 /* We want to insert these suspended elements at the front of
2463 * the waiting queue, since they were pending before any of
2464 * the waiting entries were added. This is a circular list,
2465 * so we can just shift the start back by one.*/
2466 base->req_waiting_head = base->req_waiting_head->prev;
2467
2468 if (next == req_started_at)
2469 break;
2470 req = next;
2471 }
2472 base->req_heads[i] = NULL;
2473 }
2474
2475 base->global_requests_inflight = 0;
2476
2477 EVDNS_UNLOCK(base);
2478 return 0;
2479 }
2480
2481 int
evdns_clear_nameservers_and_suspend(void)2482 evdns_clear_nameservers_and_suspend(void)
2483 {
2484 return evdns_base_clear_nameservers_and_suspend(current_base);
2485 }
2486
2487
2488 /* exported function */
2489 int
evdns_base_resume(struct evdns_base * base)2490 evdns_base_resume(struct evdns_base *base)
2491 {
2492 EVDNS_LOCK(base);
2493 evdns_requests_pump_waiting_queue(base);
2494 EVDNS_UNLOCK(base);
2495
2496 return 0;
2497 }
2498
2499 int
evdns_resume(void)2500 evdns_resume(void)
2501 {
2502 return evdns_base_resume(current_base);
2503 }
2504
2505 static int
evdns_nameserver_add_impl_(struct evdns_base * base,const struct sockaddr * address,int addrlen)2506 evdns_nameserver_add_impl_(struct evdns_base *base, const struct sockaddr *address, int addrlen) {
2507 /* first check to see if we already have this nameserver */
2508
2509 const struct nameserver *server = base->server_head, *const started_at = base->server_head;
2510 struct nameserver *ns;
2511 int err = 0;
2512 char addrbuf[128];
2513
2514 ASSERT_LOCKED(base);
2515 if (server) {
2516 do {
2517 if (!evutil_sockaddr_cmp((const struct sockaddr*)&server->address, address, 1)) return 3;
2518 server = server->next;
2519 } while (server != started_at);
2520 }
2521 if (addrlen > (int)sizeof(ns->address)) {
2522 log(EVDNS_LOG_DEBUG, "Addrlen %d too long.", (int)addrlen);
2523 return 2;
2524 }
2525
2526 ns = (struct nameserver *) mm_malloc(sizeof(struct nameserver));
2527 if (!ns) return -1;
2528
2529 memset(ns, 0, sizeof(struct nameserver));
2530 ns->base = base;
2531
2532 evtimer_assign(&ns->timeout_event, ns->base->event_base, nameserver_prod_callback, ns);
2533
2534 ns->socket = evutil_socket_(address->sa_family,
2535 SOCK_DGRAM|EVUTIL_SOCK_NONBLOCK|EVUTIL_SOCK_CLOEXEC, 0);
2536 if (ns->socket < 0) { err = 1; goto out1; }
2537
2538 if (base->global_outgoing_addrlen &&
2539 !evutil_sockaddr_is_loopback_(address)) {
2540 if (bind(ns->socket,
2541 (struct sockaddr*)&base->global_outgoing_address,
2542 base->global_outgoing_addrlen) < 0) {
2543 log(EVDNS_LOG_WARN,"Couldn't bind to outgoing address");
2544 err = 2;
2545 goto out2;
2546 }
2547 }
2548
2549 if (base->so_rcvbuf) {
2550 if (setsockopt(ns->socket, SOL_SOCKET, SO_RCVBUF,
2551 (void *)&base->so_rcvbuf, sizeof(base->so_rcvbuf))) {
2552 log(EVDNS_LOG_WARN, "Couldn't set SO_RCVBUF to %i", base->so_rcvbuf);
2553 err = -SO_RCVBUF;
2554 goto out2;
2555 }
2556 }
2557 if (base->so_sndbuf) {
2558 if (setsockopt(ns->socket, SOL_SOCKET, SO_SNDBUF,
2559 (void *)&base->so_sndbuf, sizeof(base->so_sndbuf))) {
2560 log(EVDNS_LOG_WARN, "Couldn't set SO_SNDBUF to %i", base->so_sndbuf);
2561 err = -SO_SNDBUF;
2562 goto out2;
2563 }
2564 }
2565
2566 memcpy(&ns->address, address, addrlen);
2567 ns->addrlen = addrlen;
2568 ns->state = 1;
2569 event_assign(&ns->event, ns->base->event_base, ns->socket,
2570 EV_READ | EV_PERSIST, nameserver_ready_callback, ns);
2571 if (!base->disable_when_inactive && event_add(&ns->event, NULL) < 0) {
2572 err = 2;
2573 goto out2;
2574 }
2575
2576 log(EVDNS_LOG_DEBUG, "Added nameserver %s as %p",
2577 evutil_format_sockaddr_port_(address, addrbuf, sizeof(addrbuf)), ns);
2578
2579 /* insert this nameserver into the list of them */
2580 if (!base->server_head) {
2581 ns->next = ns->prev = ns;
2582 base->server_head = ns;
2583 } else {
2584 ns->next = base->server_head->next;
2585 ns->prev = base->server_head;
2586 base->server_head->next = ns;
2587 ns->next->prev = ns;
2588 }
2589
2590 base->global_good_nameservers++;
2591
2592 return 0;
2593
2594 out2:
2595 evutil_closesocket(ns->socket);
2596 out1:
2597 event_debug_unassign(&ns->event);
2598 mm_free(ns);
2599 log(EVDNS_LOG_WARN, "Unable to add nameserver %s: error %d",
2600 evutil_format_sockaddr_port_(address, addrbuf, sizeof(addrbuf)), err);
2601 return err;
2602 }
2603
2604 /* exported function */
2605 int
evdns_base_nameserver_add(struct evdns_base * base,unsigned long int address)2606 evdns_base_nameserver_add(struct evdns_base *base, unsigned long int address)
2607 {
2608 struct sockaddr_in sin;
2609 int res;
2610 memset(&sin, 0, sizeof(sin));
2611 sin.sin_addr.s_addr = address;
2612 sin.sin_port = htons(53);
2613 sin.sin_family = AF_INET;
2614 EVDNS_LOCK(base);
2615 res = evdns_nameserver_add_impl_(base, (struct sockaddr*)&sin, sizeof(sin));
2616 EVDNS_UNLOCK(base);
2617 return res;
2618 }
2619
2620 int
evdns_nameserver_add(unsigned long int address)2621 evdns_nameserver_add(unsigned long int address) {
2622 if (!current_base)
2623 current_base = evdns_base_new(NULL, 0);
2624 return evdns_base_nameserver_add(current_base, address);
2625 }
2626
2627 static void
sockaddr_setport(struct sockaddr * sa,ev_uint16_t port)2628 sockaddr_setport(struct sockaddr *sa, ev_uint16_t port)
2629 {
2630 if (sa->sa_family == AF_INET) {
2631 ((struct sockaddr_in *)sa)->sin_port = htons(port);
2632 } else if (sa->sa_family == AF_INET6) {
2633 ((struct sockaddr_in6 *)sa)->sin6_port = htons(port);
2634 }
2635 }
2636
2637 static ev_uint16_t
sockaddr_getport(struct sockaddr * sa)2638 sockaddr_getport(struct sockaddr *sa)
2639 {
2640 if (sa->sa_family == AF_INET) {
2641 return ntohs(((struct sockaddr_in *)sa)->sin_port);
2642 } else if (sa->sa_family == AF_INET6) {
2643 return ntohs(((struct sockaddr_in6 *)sa)->sin6_port);
2644 } else {
2645 return 0;
2646 }
2647 }
2648
2649 /* exported function */
2650 int
evdns_base_nameserver_ip_add(struct evdns_base * base,const char * ip_as_string)2651 evdns_base_nameserver_ip_add(struct evdns_base *base, const char *ip_as_string) {
2652 struct sockaddr_storage ss;
2653 struct sockaddr *sa;
2654 int len = sizeof(ss);
2655 int res;
2656 if (evutil_parse_sockaddr_port(ip_as_string, (struct sockaddr *)&ss,
2657 &len)) {
2658 log(EVDNS_LOG_WARN, "Unable to parse nameserver address %s",
2659 ip_as_string);
2660 return 4;
2661 }
2662 sa = (struct sockaddr *) &ss;
2663 if (sockaddr_getport(sa) == 0)
2664 sockaddr_setport(sa, 53);
2665
2666 EVDNS_LOCK(base);
2667 res = evdns_nameserver_add_impl_(base, sa, len);
2668 EVDNS_UNLOCK(base);
2669 return res;
2670 }
2671
2672 int
evdns_nameserver_ip_add(const char * ip_as_string)2673 evdns_nameserver_ip_add(const char *ip_as_string) {
2674 if (!current_base)
2675 current_base = evdns_base_new(NULL, 0);
2676 return evdns_base_nameserver_ip_add(current_base, ip_as_string);
2677 }
2678
2679 int
evdns_base_nameserver_sockaddr_add(struct evdns_base * base,const struct sockaddr * sa,ev_socklen_t len,unsigned flags)2680 evdns_base_nameserver_sockaddr_add(struct evdns_base *base,
2681 const struct sockaddr *sa, ev_socklen_t len, unsigned flags)
2682 {
2683 int res;
2684 EVUTIL_ASSERT(base);
2685 EVDNS_LOCK(base);
2686 res = evdns_nameserver_add_impl_(base, sa, len);
2687 EVDNS_UNLOCK(base);
2688 return res;
2689 }
2690
2691 int
evdns_base_get_nameserver_addr(struct evdns_base * base,int idx,struct sockaddr * sa,ev_socklen_t len)2692 evdns_base_get_nameserver_addr(struct evdns_base *base, int idx,
2693 struct sockaddr *sa, ev_socklen_t len)
2694 {
2695 int result = -1;
2696 int i;
2697 struct nameserver *server;
2698 EVDNS_LOCK(base);
2699 server = base->server_head;
2700 for (i = 0; i < idx && server; ++i, server = server->next) {
2701 if (server->next == base->server_head)
2702 goto done;
2703 }
2704 if (! server)
2705 goto done;
2706
2707 if (server->addrlen > len) {
2708 result = (int) server->addrlen;
2709 goto done;
2710 }
2711
2712 memcpy(sa, &server->address, server->addrlen);
2713 result = (int) server->addrlen;
2714 done:
2715 EVDNS_UNLOCK(base);
2716 return result;
2717 }
2718
2719 /* remove from the queue */
2720 static void
evdns_request_remove(struct request * req,struct request ** head)2721 evdns_request_remove(struct request *req, struct request **head)
2722 {
2723 ASSERT_LOCKED(req->base);
2724 ASSERT_VALID_REQUEST(req);
2725
2726 #if 0
2727 {
2728 struct request *ptr;
2729 int found = 0;
2730 EVUTIL_ASSERT(*head != NULL);
2731
2732 ptr = *head;
2733 do {
2734 if (ptr == req) {
2735 found = 1;
2736 break;
2737 }
2738 ptr = ptr->next;
2739 } while (ptr != *head);
2740 EVUTIL_ASSERT(found);
2741
2742 EVUTIL_ASSERT(req->next);
2743 }
2744 #endif
2745
2746 if (req->next == req) {
2747 /* only item in the list */
2748 *head = NULL;
2749 } else {
2750 req->next->prev = req->prev;
2751 req->prev->next = req->next;
2752 if (*head == req) *head = req->next;
2753 }
2754 req->next = req->prev = NULL;
2755 }
2756
2757 /* insert into the tail of the queue */
2758 static void
evdns_request_insert(struct request * req,struct request ** head)2759 evdns_request_insert(struct request *req, struct request **head) {
2760 ASSERT_LOCKED(req->base);
2761 ASSERT_VALID_REQUEST(req);
2762 if (!*head) {
2763 *head = req;
2764 req->next = req->prev = req;
2765 return;
2766 }
2767
2768 req->prev = (*head)->prev;
2769 req->prev->next = req;
2770 req->next = *head;
2771 (*head)->prev = req;
2772 }
2773
2774 static int
string_num_dots(const char * s)2775 string_num_dots(const char *s) {
2776 int count = 0;
2777 while ((s = strchr(s, '.'))) {
2778 s++;
2779 count++;
2780 }
2781 return count;
2782 }
2783
2784 static struct request *
request_new(struct evdns_base * base,struct evdns_request * handle,int type,const char * name,int flags,evdns_callback_type callback,void * user_ptr)2785 request_new(struct evdns_base *base, struct evdns_request *handle, int type,
2786 const char *name, int flags, evdns_callback_type callback,
2787 void *user_ptr) {
2788
2789 const char issuing_now =
2790 (base->global_requests_inflight < base->global_max_requests_inflight) ? 1 : 0;
2791
2792 const size_t name_len = strlen(name);
2793 const size_t request_max_len = evdns_request_len(name_len);
2794 const u16 trans_id = issuing_now ? transaction_id_pick(base) : 0xffff;
2795 /* the request data is alloced in a single block with the header */
2796 struct request *const req =
2797 mm_malloc(sizeof(struct request) + request_max_len);
2798 int rlen;
2799 char namebuf[256];
2800 (void) flags;
2801
2802 ASSERT_LOCKED(base);
2803
2804 if (!req) return NULL;
2805
2806 if (name_len >= sizeof(namebuf)) {
2807 mm_free(req);
2808 return NULL;
2809 }
2810
2811 memset(req, 0, sizeof(struct request));
2812 req->base = base;
2813
2814 evtimer_assign(&req->timeout_event, req->base->event_base, evdns_request_timeout_callback, req);
2815
2816 if (base->global_randomize_case) {
2817 unsigned i;
2818 char randbits[(sizeof(namebuf)+7)/8];
2819 strlcpy(namebuf, name, sizeof(namebuf));
2820 evutil_secure_rng_get_bytes(randbits, (name_len+7)/8);
2821 for (i = 0; i < name_len; ++i) {
2822 if (EVUTIL_ISALPHA_(namebuf[i])) {
2823 if ((randbits[i >> 3] & (1<<(i & 7))))
2824 namebuf[i] |= 0x20;
2825 else
2826 namebuf[i] &= ~0x20;
2827 }
2828 }
2829 name = namebuf;
2830 }
2831
2832 /* request data lives just after the header */
2833 req->request = ((u8 *) req) + sizeof(struct request);
2834 /* denotes that the request data shouldn't be free()ed */
2835 req->request_appended = 1;
2836 rlen = evdns_request_data_build(name, name_len, trans_id,
2837 type, CLASS_INET, req->request, request_max_len);
2838 if (rlen < 0)
2839 goto err1;
2840
2841 req->request_len = rlen;
2842 req->trans_id = trans_id;
2843 req->tx_count = 0;
2844 req->request_type = type;
2845 req->user_pointer = user_ptr;
2846 req->user_callback = callback;
2847 req->ns = issuing_now ? nameserver_pick(base) : NULL;
2848 req->next = req->prev = NULL;
2849 req->handle = handle;
2850 if (handle) {
2851 handle->current_req = req;
2852 handle->base = base;
2853 }
2854
2855 return req;
2856 err1:
2857 mm_free(req);
2858 return NULL;
2859 }
2860
2861 static void
request_submit(struct request * const req)2862 request_submit(struct request *const req) {
2863 struct evdns_base *base = req->base;
2864 ASSERT_LOCKED(base);
2865 ASSERT_VALID_REQUEST(req);
2866 if (req->ns) {
2867 /* if it has a nameserver assigned then this is going */
2868 /* straight into the inflight queue */
2869 evdns_request_insert(req, &REQ_HEAD(base, req->trans_id));
2870
2871 base->global_requests_inflight++;
2872 req->ns->requests_inflight++;
2873
2874 evdns_request_transmit(req);
2875 } else {
2876 evdns_request_insert(req, &base->req_waiting_head);
2877 base->global_requests_waiting++;
2878 }
2879 }
2880
2881 /* exported function */
2882 void
evdns_cancel_request(struct evdns_base * base,struct evdns_request * handle)2883 evdns_cancel_request(struct evdns_base *base, struct evdns_request *handle)
2884 {
2885 struct request *req;
2886
2887 if (!handle->current_req)
2888 return;
2889
2890 if (!base) {
2891 /* This redundancy is silly; can we fix it? (Not for 2.0) XXXX */
2892 base = handle->base;
2893 if (!base)
2894 base = handle->current_req->base;
2895 }
2896
2897 EVDNS_LOCK(base);
2898 if (handle->pending_cb) {
2899 EVDNS_UNLOCK(base);
2900 return;
2901 }
2902
2903 req = handle->current_req;
2904 ASSERT_VALID_REQUEST(req);
2905
2906 reply_schedule_callback(req, 0, DNS_ERR_CANCEL, NULL);
2907 if (req->ns) {
2908 /* remove from inflight queue */
2909 request_finished(req, &REQ_HEAD(base, req->trans_id), 1);
2910 } else {
2911 /* remove from global_waiting head */
2912 request_finished(req, &base->req_waiting_head, 1);
2913 }
2914 EVDNS_UNLOCK(base);
2915 }
2916
2917 /* exported function */
2918 struct evdns_request *
evdns_base_resolve_ipv4(struct evdns_base * base,const char * name,int flags,evdns_callback_type callback,void * ptr)2919 evdns_base_resolve_ipv4(struct evdns_base *base, const char *name, int flags,
2920 evdns_callback_type callback, void *ptr) {
2921 struct evdns_request *handle;
2922 struct request *req;
2923 log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name);
2924 handle = mm_calloc(1, sizeof(*handle));
2925 if (handle == NULL)
2926 return NULL;
2927 EVDNS_LOCK(base);
2928 if (flags & DNS_QUERY_NO_SEARCH) {
2929 req =
2930 request_new(base, handle, TYPE_A, name, flags,
2931 callback, ptr);
2932 if (req)
2933 request_submit(req);
2934 } else {
2935 search_request_new(base, handle, TYPE_A, name, flags,
2936 callback, ptr);
2937 }
2938 if (handle->current_req == NULL) {
2939 mm_free(handle);
2940 handle = NULL;
2941 }
2942 EVDNS_UNLOCK(base);
2943 return handle;
2944 }
2945
evdns_resolve_ipv4(const char * name,int flags,evdns_callback_type callback,void * ptr)2946 int evdns_resolve_ipv4(const char *name, int flags,
2947 evdns_callback_type callback, void *ptr)
2948 {
2949 return evdns_base_resolve_ipv4(current_base, name, flags, callback, ptr)
2950 ? 0 : -1;
2951 }
2952
2953
2954 /* exported function */
2955 struct evdns_request *
evdns_base_resolve_ipv6(struct evdns_base * base,const char * name,int flags,evdns_callback_type callback,void * ptr)2956 evdns_base_resolve_ipv6(struct evdns_base *base,
2957 const char *name, int flags,
2958 evdns_callback_type callback, void *ptr)
2959 {
2960 struct evdns_request *handle;
2961 struct request *req;
2962 log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name);
2963 handle = mm_calloc(1, sizeof(*handle));
2964 if (handle == NULL)
2965 return NULL;
2966 EVDNS_LOCK(base);
2967 if (flags & DNS_QUERY_NO_SEARCH) {
2968 req = request_new(base, handle, TYPE_AAAA, name, flags,
2969 callback, ptr);
2970 if (req)
2971 request_submit(req);
2972 } else {
2973 search_request_new(base, handle, TYPE_AAAA, name, flags,
2974 callback, ptr);
2975 }
2976 if (handle->current_req == NULL) {
2977 mm_free(handle);
2978 handle = NULL;
2979 }
2980 EVDNS_UNLOCK(base);
2981 return handle;
2982 }
2983
evdns_resolve_ipv6(const char * name,int flags,evdns_callback_type callback,void * ptr)2984 int evdns_resolve_ipv6(const char *name, int flags,
2985 evdns_callback_type callback, void *ptr) {
2986 return evdns_base_resolve_ipv6(current_base, name, flags, callback, ptr)
2987 ? 0 : -1;
2988 }
2989
2990 struct evdns_request *
evdns_base_resolve_reverse(struct evdns_base * base,const struct in_addr * in,int flags,evdns_callback_type callback,void * ptr)2991 evdns_base_resolve_reverse(struct evdns_base *base, const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) {
2992 char buf[32];
2993 struct evdns_request *handle;
2994 struct request *req;
2995 u32 a;
2996 EVUTIL_ASSERT(in);
2997 a = ntohl(in->s_addr);
2998 evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa",
2999 (int)(u8)((a )&0xff),
3000 (int)(u8)((a>>8 )&0xff),
3001 (int)(u8)((a>>16)&0xff),
3002 (int)(u8)((a>>24)&0xff));
3003 handle = mm_calloc(1, sizeof(*handle));
3004 if (handle == NULL)
3005 return NULL;
3006 log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf);
3007 EVDNS_LOCK(base);
3008 req = request_new(base, handle, TYPE_PTR, buf, flags, callback, ptr);
3009 if (req)
3010 request_submit(req);
3011 if (handle->current_req == NULL) {
3012 mm_free(handle);
3013 handle = NULL;
3014 }
3015 EVDNS_UNLOCK(base);
3016 return (handle);
3017 }
3018
evdns_resolve_reverse(const struct in_addr * in,int flags,evdns_callback_type callback,void * ptr)3019 int evdns_resolve_reverse(const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) {
3020 return evdns_base_resolve_reverse(current_base, in, flags, callback, ptr)
3021 ? 0 : -1;
3022 }
3023
3024 struct evdns_request *
evdns_base_resolve_reverse_ipv6(struct evdns_base * base,const struct in6_addr * in,int flags,evdns_callback_type callback,void * ptr)3025 evdns_base_resolve_reverse_ipv6(struct evdns_base *base, const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) {
3026 /* 32 nybbles, 32 periods, "ip6.arpa", NUL. */
3027 char buf[73];
3028 char *cp;
3029 struct evdns_request *handle;
3030 struct request *req;
3031 int i;
3032 EVUTIL_ASSERT(in);
3033 cp = buf;
3034 for (i=15; i >= 0; --i) {
3035 u8 byte = in->s6_addr[i];
3036 *cp++ = "0123456789abcdef"[byte & 0x0f];
3037 *cp++ = '.';
3038 *cp++ = "0123456789abcdef"[byte >> 4];
3039 *cp++ = '.';
3040 }
3041 EVUTIL_ASSERT(cp + strlen("ip6.arpa") < buf+sizeof(buf));
3042 memcpy(cp, "ip6.arpa", strlen("ip6.arpa")+1);
3043 handle = mm_calloc(1, sizeof(*handle));
3044 if (handle == NULL)
3045 return NULL;
3046 log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf);
3047 EVDNS_LOCK(base);
3048 req = request_new(base, handle, TYPE_PTR, buf, flags, callback, ptr);
3049 if (req)
3050 request_submit(req);
3051 if (handle->current_req == NULL) {
3052 mm_free(handle);
3053 handle = NULL;
3054 }
3055 EVDNS_UNLOCK(base);
3056 return (handle);
3057 }
3058
evdns_resolve_reverse_ipv6(const struct in6_addr * in,int flags,evdns_callback_type callback,void * ptr)3059 int evdns_resolve_reverse_ipv6(const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) {
3060 return evdns_base_resolve_reverse_ipv6(current_base, in, flags, callback, ptr)
3061 ? 0 : -1;
3062 }
3063
3064 /* ================================================================= */
3065 /* Search support */
3066 /* */
3067 /* the libc resolver has support for searching a number of domains */
3068 /* to find a name. If nothing else then it takes the single domain */
3069 /* from the gethostname() call. */
3070 /* */
3071 /* It can also be configured via the domain and search options in a */
3072 /* resolv.conf. */
3073 /* */
3074 /* The ndots option controls how many dots it takes for the resolver */
3075 /* to decide that a name is non-local and so try a raw lookup first. */
3076
3077 struct search_domain {
3078 int len;
3079 struct search_domain *next;
3080 /* the text string is appended to this structure */
3081 };
3082
3083 struct search_state {
3084 int refcount;
3085 int ndots;
3086 int num_domains;
3087 struct search_domain *head;
3088 };
3089
3090 static void
search_state_decref(struct search_state * const state)3091 search_state_decref(struct search_state *const state) {
3092 if (!state) return;
3093 state->refcount--;
3094 if (!state->refcount) {
3095 struct search_domain *next, *dom;
3096 for (dom = state->head; dom; dom = next) {
3097 next = dom->next;
3098 mm_free(dom);
3099 }
3100 mm_free(state);
3101 }
3102 }
3103
3104 static struct search_state *
search_state_new(void)3105 search_state_new(void) {
3106 struct search_state *state = (struct search_state *) mm_malloc(sizeof(struct search_state));
3107 if (!state) return NULL;
3108 memset(state, 0, sizeof(struct search_state));
3109 state->refcount = 1;
3110 state->ndots = 1;
3111
3112 return state;
3113 }
3114
3115 static void
search_postfix_clear(struct evdns_base * base)3116 search_postfix_clear(struct evdns_base *base) {
3117 search_state_decref(base->global_search_state);
3118
3119 base->global_search_state = search_state_new();
3120 }
3121
3122 /* exported function */
3123 void
evdns_base_search_clear(struct evdns_base * base)3124 evdns_base_search_clear(struct evdns_base *base)
3125 {
3126 EVDNS_LOCK(base);
3127 search_postfix_clear(base);
3128 EVDNS_UNLOCK(base);
3129 }
3130
3131 void
evdns_search_clear(void)3132 evdns_search_clear(void) {
3133 evdns_base_search_clear(current_base);
3134 }
3135
3136 static void
search_postfix_add(struct evdns_base * base,const char * domain)3137 search_postfix_add(struct evdns_base *base, const char *domain) {
3138 size_t domain_len;
3139 struct search_domain *sdomain;
3140 while (domain[0] == '.') domain++;
3141 domain_len = strlen(domain);
3142
3143 ASSERT_LOCKED(base);
3144 if (!base->global_search_state) base->global_search_state = search_state_new();
3145 if (!base->global_search_state) return;
3146 base->global_search_state->num_domains++;
3147
3148 sdomain = (struct search_domain *) mm_malloc(sizeof(struct search_domain) + domain_len);
3149 if (!sdomain) return;
3150 memcpy( ((u8 *) sdomain) + sizeof(struct search_domain), domain, domain_len);
3151 sdomain->next = base->global_search_state->head;
3152 sdomain->len = (int) domain_len;
3153
3154 base->global_search_state->head = sdomain;
3155 }
3156
3157 /* reverse the order of members in the postfix list. This is needed because, */
3158 /* when parsing resolv.conf we push elements in the wrong order */
3159 static void
search_reverse(struct evdns_base * base)3160 search_reverse(struct evdns_base *base) {
3161 struct search_domain *cur, *prev = NULL, *next;
3162 ASSERT_LOCKED(base);
3163 cur = base->global_search_state->head;
3164 while (cur) {
3165 next = cur->next;
3166 cur->next = prev;
3167 prev = cur;
3168 cur = next;
3169 }
3170
3171 base->global_search_state->head = prev;
3172 }
3173
3174 /* exported function */
3175 void
evdns_base_search_add(struct evdns_base * base,const char * domain)3176 evdns_base_search_add(struct evdns_base *base, const char *domain) {
3177 EVDNS_LOCK(base);
3178 search_postfix_add(base, domain);
3179 EVDNS_UNLOCK(base);
3180 }
3181 void
evdns_search_add(const char * domain)3182 evdns_search_add(const char *domain) {
3183 evdns_base_search_add(current_base, domain);
3184 }
3185
3186 /* exported function */
3187 void
evdns_base_search_ndots_set(struct evdns_base * base,const int ndots)3188 evdns_base_search_ndots_set(struct evdns_base *base, const int ndots) {
3189 EVDNS_LOCK(base);
3190 if (!base->global_search_state) base->global_search_state = search_state_new();
3191 if (base->global_search_state)
3192 base->global_search_state->ndots = ndots;
3193 EVDNS_UNLOCK(base);
3194 }
3195 void
evdns_search_ndots_set(const int ndots)3196 evdns_search_ndots_set(const int ndots) {
3197 evdns_base_search_ndots_set(current_base, ndots);
3198 }
3199
3200 static void
search_set_from_hostname(struct evdns_base * base)3201 search_set_from_hostname(struct evdns_base *base) {
3202 char hostname[HOST_NAME_MAX + 1], *domainname;
3203
3204 ASSERT_LOCKED(base);
3205 search_postfix_clear(base);
3206 if (gethostname(hostname, sizeof(hostname))) return;
3207 domainname = strchr(hostname, '.');
3208 if (!domainname) return;
3209 search_postfix_add(base, domainname);
3210 }
3211
3212 /* warning: returns malloced string */
3213 static char *
search_make_new(const struct search_state * const state,int n,const char * const base_name)3214 search_make_new(const struct search_state *const state, int n, const char *const base_name) {
3215 const size_t base_len = strlen(base_name);
3216 char need_to_append_dot;
3217 struct search_domain *dom;
3218
3219 if (!base_len) return NULL;
3220 need_to_append_dot = base_name[base_len - 1] == '.' ? 0 : 1;
3221
3222 for (dom = state->head; dom; dom = dom->next) {
3223 if (!n--) {
3224 /* this is the postfix we want */
3225 /* the actual postfix string is kept at the end of the structure */
3226 const u8 *const postfix = ((u8 *) dom) + sizeof(struct search_domain);
3227 const int postfix_len = dom->len;
3228 char *const newname = (char *) mm_malloc(base_len + need_to_append_dot + postfix_len + 1);
3229 if (!newname) return NULL;
3230 memcpy(newname, base_name, base_len);
3231 if (need_to_append_dot) newname[base_len] = '.';
3232 memcpy(newname + base_len + need_to_append_dot, postfix, postfix_len);
3233 newname[base_len + need_to_append_dot + postfix_len] = 0;
3234 return newname;
3235 }
3236 }
3237
3238 /* we ran off the end of the list and still didn't find the requested string */
3239 EVUTIL_ASSERT(0);
3240 return NULL; /* unreachable; stops warnings in some compilers. */
3241 }
3242
3243 static struct request *
search_request_new(struct evdns_base * base,struct evdns_request * handle,int type,const char * const name,int flags,evdns_callback_type user_callback,void * user_arg)3244 search_request_new(struct evdns_base *base, struct evdns_request *handle,
3245 int type, const char *const name, int flags,
3246 evdns_callback_type user_callback, void *user_arg) {
3247 ASSERT_LOCKED(base);
3248 EVUTIL_ASSERT(type == TYPE_A || type == TYPE_AAAA);
3249 EVUTIL_ASSERT(handle->current_req == NULL);
3250 if ( ((flags & DNS_QUERY_NO_SEARCH) == 0) &&
3251 base->global_search_state &&
3252 base->global_search_state->num_domains) {
3253 /* we have some domains to search */
3254 struct request *req;
3255 if (string_num_dots(name) >= base->global_search_state->ndots) {
3256 req = request_new(base, handle, type, name, flags, user_callback, user_arg);
3257 if (!req) return NULL;
3258 handle->search_index = -1;
3259 } else {
3260 char *const new_name = search_make_new(base->global_search_state, 0, name);
3261 if (!new_name) return NULL;
3262 req = request_new(base, handle, type, new_name, flags, user_callback, user_arg);
3263 mm_free(new_name);
3264 if (!req) return NULL;
3265 handle->search_index = 0;
3266 }
3267 EVUTIL_ASSERT(handle->search_origname == NULL);
3268 handle->search_origname = mm_strdup(name);
3269 if (handle->search_origname == NULL) {
3270 /* XXX Should we dealloc req? If yes, how? */
3271 if (req)
3272 mm_free(req);
3273 return NULL;
3274 }
3275 handle->search_state = base->global_search_state;
3276 handle->search_flags = flags;
3277 base->global_search_state->refcount++;
3278 request_submit(req);
3279 return req;
3280 } else {
3281 struct request *const req = request_new(base, handle, type, name, flags, user_callback, user_arg);
3282 if (!req) return NULL;
3283 request_submit(req);
3284 return req;
3285 }
3286 }
3287
3288 /* this is called when a request has failed to find a name. We need to check */
3289 /* if it is part of a search and, if so, try the next name in the list */
3290 /* returns: */
3291 /* 0 another request has been submitted */
3292 /* 1 no more requests needed */
3293 static int
search_try_next(struct evdns_request * const handle)3294 search_try_next(struct evdns_request *const handle) {
3295 struct request *req = handle->current_req;
3296 struct evdns_base *base = req->base;
3297 struct request *newreq;
3298 ASSERT_LOCKED(base);
3299 if (handle->search_state) {
3300 /* it is part of a search */
3301 char *new_name;
3302 handle->search_index++;
3303 if (handle->search_index >= handle->search_state->num_domains) {
3304 /* no more postfixes to try, however we may need to try */
3305 /* this name without a postfix */
3306 if (string_num_dots(handle->search_origname) < handle->search_state->ndots) {
3307 /* yep, we need to try it raw */
3308 newreq = request_new(base, NULL, req->request_type, handle->search_origname, handle->search_flags, req->user_callback, req->user_pointer);
3309 log(EVDNS_LOG_DEBUG, "Search: trying raw query %s", handle->search_origname);
3310 if (newreq) {
3311 search_request_finished(handle);
3312 goto submit_next;
3313 }
3314 }
3315 return 1;
3316 }
3317
3318 new_name = search_make_new(handle->search_state, handle->search_index, handle->search_origname);
3319 if (!new_name) return 1;
3320 log(EVDNS_LOG_DEBUG, "Search: now trying %s (%d)", new_name, handle->search_index);
3321 newreq = request_new(base, NULL, req->request_type, new_name, handle->search_flags, req->user_callback, req->user_pointer);
3322 mm_free(new_name);
3323 if (!newreq) return 1;
3324 goto submit_next;
3325 }
3326 return 1;
3327
3328 submit_next:
3329 request_finished(req, &REQ_HEAD(req->base, req->trans_id), 0);
3330 handle->current_req = newreq;
3331 newreq->handle = handle;
3332 request_submit(newreq);
3333 return 0;
3334 }
3335
3336 static void
search_request_finished(struct evdns_request * const handle)3337 search_request_finished(struct evdns_request *const handle) {
3338 ASSERT_LOCKED(handle->current_req->base);
3339 if (handle->search_state) {
3340 search_state_decref(handle->search_state);
3341 handle->search_state = NULL;
3342 }
3343 if (handle->search_origname) {
3344 mm_free(handle->search_origname);
3345 handle->search_origname = NULL;
3346 }
3347 }
3348
3349 /* ================================================================= */
3350 /* Parsing resolv.conf files */
3351
3352 static void
evdns_resolv_set_defaults(struct evdns_base * base,int flags)3353 evdns_resolv_set_defaults(struct evdns_base *base, int flags) {
3354 int add_default = flags & DNS_OPTION_NAMESERVERS;
3355 if (flags & DNS_OPTION_NAMESERVERS_NO_DEFAULT)
3356 add_default = 0;
3357
3358 /* if the file isn't found then we assume a local resolver */
3359 ASSERT_LOCKED(base);
3360 if (flags & DNS_OPTION_SEARCH)
3361 search_set_from_hostname(base);
3362 if (add_default)
3363 evdns_base_nameserver_ip_add(base, "127.0.0.1");
3364 }
3365
3366 #ifndef EVENT__HAVE_STRTOK_R
3367 static char *
strtok_r(char * s,const char * delim,char ** state)3368 strtok_r(char *s, const char *delim, char **state) {
3369 char *cp, *start;
3370 start = cp = s ? s : *state;
3371 if (!cp)
3372 return NULL;
3373 while (*cp && !strchr(delim, *cp))
3374 ++cp;
3375 if (!*cp) {
3376 if (cp == start)
3377 return NULL;
3378 *state = NULL;
3379 return start;
3380 } else {
3381 *cp++ = '\0';
3382 *state = cp;
3383 return start;
3384 }
3385 }
3386 #endif
3387
3388 /* helper version of atoi which returns -1 on error */
3389 static int
strtoint(const char * const str)3390 strtoint(const char *const str)
3391 {
3392 char *endptr;
3393 const int r = strtol(str, &endptr, 10);
3394 if (*endptr) return -1;
3395 return r;
3396 }
3397
3398 /* Parse a number of seconds into a timeval; return -1 on error. */
3399 static int
evdns_strtotimeval(const char * const str,struct timeval * out)3400 evdns_strtotimeval(const char *const str, struct timeval *out)
3401 {
3402 double d;
3403 char *endptr;
3404 d = strtod(str, &endptr);
3405 if (*endptr) return -1;
3406 if (d < 0) return -1;
3407 out->tv_sec = (int) d;
3408 out->tv_usec = (int) ((d - (int) d)*1000000);
3409 if (out->tv_sec == 0 && out->tv_usec < 1000) /* less than 1 msec */
3410 return -1;
3411 return 0;
3412 }
3413
3414 /* helper version of atoi that returns -1 on error and clips to bounds. */
3415 static int
strtoint_clipped(const char * const str,int min,int max)3416 strtoint_clipped(const char *const str, int min, int max)
3417 {
3418 int r = strtoint(str);
3419 if (r == -1)
3420 return r;
3421 else if (r<min)
3422 return min;
3423 else if (r>max)
3424 return max;
3425 else
3426 return r;
3427 }
3428
3429 static int
evdns_base_set_max_requests_inflight(struct evdns_base * base,int maxinflight)3430 evdns_base_set_max_requests_inflight(struct evdns_base *base, int maxinflight)
3431 {
3432 int old_n_heads = base->n_req_heads, n_heads;
3433 struct request **old_heads = base->req_heads, **new_heads, *req;
3434 int i;
3435
3436 ASSERT_LOCKED(base);
3437 if (maxinflight < 1)
3438 maxinflight = 1;
3439 n_heads = (maxinflight+4) / 5;
3440 EVUTIL_ASSERT(n_heads > 0);
3441 new_heads = mm_calloc(n_heads, sizeof(struct request*));
3442 if (!new_heads)
3443 return (-1);
3444 if (old_heads) {
3445 for (i = 0; i < old_n_heads; ++i) {
3446 while (old_heads[i]) {
3447 req = old_heads[i];
3448 evdns_request_remove(req, &old_heads[i]);
3449 evdns_request_insert(req, &new_heads[req->trans_id % n_heads]);
3450 }
3451 }
3452 mm_free(old_heads);
3453 }
3454 base->req_heads = new_heads;
3455 base->n_req_heads = n_heads;
3456 base->global_max_requests_inflight = maxinflight;
3457 return (0);
3458 }
3459
3460 /* exported function */
3461 int
evdns_base_set_option(struct evdns_base * base,const char * option,const char * val)3462 evdns_base_set_option(struct evdns_base *base,
3463 const char *option, const char *val)
3464 {
3465 int res;
3466 EVDNS_LOCK(base);
3467 res = evdns_base_set_option_impl(base, option, val, DNS_OPTIONS_ALL);
3468 EVDNS_UNLOCK(base);
3469 return res;
3470 }
3471
3472 static inline int
str_matches_option(const char * s1,const char * optionname)3473 str_matches_option(const char *s1, const char *optionname)
3474 {
3475 /* Option names are given as "option:" We accept either 'option' in
3476 * s1, or 'option:randomjunk'. The latter form is to implement the
3477 * resolv.conf parser. */
3478 size_t optlen = strlen(optionname);
3479 size_t slen = strlen(s1);
3480 if (slen == optlen || slen == optlen - 1)
3481 return !strncmp(s1, optionname, slen);
3482 else if (slen > optlen)
3483 return !strncmp(s1, optionname, optlen);
3484 else
3485 return 0;
3486 }
3487
3488 static int
evdns_base_set_option_impl(struct evdns_base * base,const char * option,const char * val,int flags)3489 evdns_base_set_option_impl(struct evdns_base *base,
3490 const char *option, const char *val, int flags)
3491 {
3492 ASSERT_LOCKED(base);
3493 if (str_matches_option(option, "ndots:")) {
3494 const int ndots = strtoint(val);
3495 if (ndots == -1) return -1;
3496 if (!(flags & DNS_OPTION_SEARCH)) return 0;
3497 log(EVDNS_LOG_DEBUG, "Setting ndots to %d", ndots);
3498 if (!base->global_search_state) base->global_search_state = search_state_new();
3499 if (!base->global_search_state) return -1;
3500 base->global_search_state->ndots = ndots;
3501 } else if (str_matches_option(option, "timeout:")) {
3502 struct timeval tv;
3503 if (evdns_strtotimeval(val, &tv) == -1) return -1;
3504 if (!(flags & DNS_OPTION_MISC)) return 0;
3505 log(EVDNS_LOG_DEBUG, "Setting timeout to %s", val);
3506 memcpy(&base->global_timeout, &tv, sizeof(struct timeval));
3507 } else if (str_matches_option(option, "getaddrinfo-allow-skew:")) {
3508 struct timeval tv;
3509 if (evdns_strtotimeval(val, &tv) == -1) return -1;
3510 if (!(flags & DNS_OPTION_MISC)) return 0;
3511 log(EVDNS_LOG_DEBUG, "Setting getaddrinfo-allow-skew to %s",
3512 val);
3513 memcpy(&base->global_getaddrinfo_allow_skew, &tv,
3514 sizeof(struct timeval));
3515 } else if (str_matches_option(option, "max-timeouts:")) {
3516 const int maxtimeout = strtoint_clipped(val, 1, 255);
3517 if (maxtimeout == -1) return -1;
3518 if (!(flags & DNS_OPTION_MISC)) return 0;
3519 log(EVDNS_LOG_DEBUG, "Setting maximum allowed timeouts to %d",
3520 maxtimeout);
3521 base->global_max_nameserver_timeout = maxtimeout;
3522 } else if (str_matches_option(option, "max-inflight:")) {
3523 const int maxinflight = strtoint_clipped(val, 1, 65000);
3524 if (maxinflight == -1) return -1;
3525 if (!(flags & DNS_OPTION_MISC)) return 0;
3526 log(EVDNS_LOG_DEBUG, "Setting maximum inflight requests to %d",
3527 maxinflight);
3528 evdns_base_set_max_requests_inflight(base, maxinflight);
3529 } else if (str_matches_option(option, "attempts:")) {
3530 int retries = strtoint(val);
3531 if (retries == -1) return -1;
3532 if (retries > 255) retries = 255;
3533 if (!(flags & DNS_OPTION_MISC)) return 0;
3534 log(EVDNS_LOG_DEBUG, "Setting retries to %d", retries);
3535 base->global_max_retransmits = retries;
3536 } else if (str_matches_option(option, "randomize-case:")) {
3537 int randcase = strtoint(val);
3538 if (randcase == -1) return -1;
3539 if (!(flags & DNS_OPTION_MISC)) return 0;
3540 base->global_randomize_case = randcase;
3541 } else if (str_matches_option(option, "bind-to:")) {
3542 /* XXX This only applies to successive nameservers, not
3543 * to already-configured ones. We might want to fix that. */
3544 int len = sizeof(base->global_outgoing_address);
3545 if (!(flags & DNS_OPTION_NAMESERVERS)) return 0;
3546 if (evutil_parse_sockaddr_port(val,
3547 (struct sockaddr*)&base->global_outgoing_address, &len))
3548 return -1;
3549 base->global_outgoing_addrlen = len;
3550 } else if (str_matches_option(option, "initial-probe-timeout:")) {
3551 struct timeval tv;
3552 if (evdns_strtotimeval(val, &tv) == -1) return -1;
3553 if (tv.tv_sec > 3600)
3554 tv.tv_sec = 3600;
3555 if (!(flags & DNS_OPTION_MISC)) return 0;
3556 log(EVDNS_LOG_DEBUG, "Setting initial probe timeout to %s",
3557 val);
3558 memcpy(&base->global_nameserver_probe_initial_timeout, &tv,
3559 sizeof(tv));
3560 } else if (str_matches_option(option, "so-rcvbuf:")) {
3561 int buf = strtoint(val);
3562 if (buf == -1) return -1;
3563 if (!(flags & DNS_OPTION_MISC)) return 0;
3564 log(EVDNS_LOG_DEBUG, "Setting SO_RCVBUF to %s", val);
3565 base->so_rcvbuf = buf;
3566 } else if (str_matches_option(option, "so-sndbuf:")) {
3567 int buf = strtoint(val);
3568 if (buf == -1) return -1;
3569 if (!(flags & DNS_OPTION_MISC)) return 0;
3570 log(EVDNS_LOG_DEBUG, "Setting SO_SNDBUF to %s", val);
3571 base->so_sndbuf = buf;
3572 }
3573 return 0;
3574 }
3575
3576 int
evdns_set_option(const char * option,const char * val,int flags)3577 evdns_set_option(const char *option, const char *val, int flags)
3578 {
3579 if (!current_base)
3580 current_base = evdns_base_new(NULL, 0);
3581 return evdns_base_set_option(current_base, option, val);
3582 }
3583
3584 static void
resolv_conf_parse_line(struct evdns_base * base,char * const start,int flags)3585 resolv_conf_parse_line(struct evdns_base *base, char *const start, int flags) {
3586 char *strtok_state;
3587 static const char *const delims = " \t";
3588 #define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state)
3589
3590
3591 char *const first_token = strtok_r(start, delims, &strtok_state);
3592 ASSERT_LOCKED(base);
3593 if (!first_token) return;
3594
3595 if (!strcmp(first_token, "nameserver") && (flags & DNS_OPTION_NAMESERVERS)) {
3596 const char *const nameserver = NEXT_TOKEN;
3597
3598 if (nameserver)
3599 evdns_base_nameserver_ip_add(base, nameserver);
3600 } else if (!strcmp(first_token, "domain") && (flags & DNS_OPTION_SEARCH)) {
3601 const char *const domain = NEXT_TOKEN;
3602 if (domain) {
3603 search_postfix_clear(base);
3604 search_postfix_add(base, domain);
3605 }
3606 } else if (!strcmp(first_token, "search") && (flags & DNS_OPTION_SEARCH)) {
3607 const char *domain;
3608 search_postfix_clear(base);
3609
3610 while ((domain = NEXT_TOKEN)) {
3611 search_postfix_add(base, domain);
3612 }
3613 search_reverse(base);
3614 } else if (!strcmp(first_token, "options")) {
3615 const char *option;
3616 while ((option = NEXT_TOKEN)) {
3617 const char *val = strchr(option, ':');
3618 evdns_base_set_option_impl(base, option, val ? val+1 : "", flags);
3619 }
3620 }
3621 #undef NEXT_TOKEN
3622 }
3623
3624 /* exported function */
3625 /* returns: */
3626 /* 0 no errors */
3627 /* 1 failed to open file */
3628 /* 2 failed to stat file */
3629 /* 3 file too large */
3630 /* 4 out of memory */
3631 /* 5 short read from file */
3632 int
evdns_base_resolv_conf_parse(struct evdns_base * base,int flags,const char * const filename)3633 evdns_base_resolv_conf_parse(struct evdns_base *base, int flags, const char *const filename) {
3634 int res;
3635 EVDNS_LOCK(base);
3636 res = evdns_base_resolv_conf_parse_impl(base, flags, filename);
3637 EVDNS_UNLOCK(base);
3638 return res;
3639 }
3640
3641 static char *
evdns_get_default_hosts_filename(void)3642 evdns_get_default_hosts_filename(void)
3643 {
3644 #ifdef _WIN32
3645 /* Windows is a little coy about where it puts its configuration
3646 * files. Sure, they're _usually_ in C:\windows\system32, but
3647 * there's no reason in principle they couldn't be in
3648 * W:\hoboken chicken emergency\
3649 */
3650 char path[MAX_PATH+1];
3651 static const char hostfile[] = "\\drivers\\etc\\hosts";
3652 char *path_out;
3653 size_t len_out;
3654
3655 if (! SHGetSpecialFolderPathA(NULL, path, CSIDL_SYSTEM, 0))
3656 return NULL;
3657 len_out = strlen(path)+strlen(hostfile)+1;
3658 path_out = mm_malloc(len_out);
3659 evutil_snprintf(path_out, len_out, "%s%s", path, hostfile);
3660 return path_out;
3661 #else
3662 return mm_strdup("/etc/hosts");
3663 #endif
3664 }
3665
3666 static int
evdns_base_resolv_conf_parse_impl(struct evdns_base * base,int flags,const char * const filename)3667 evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char *const filename) {
3668 size_t n;
3669 char *resolv;
3670 char *start;
3671 int err = 0;
3672 int add_default;
3673
3674 log(EVDNS_LOG_DEBUG, "Parsing resolv.conf file %s", filename);
3675
3676 add_default = flags & DNS_OPTION_NAMESERVERS;
3677 if (flags & DNS_OPTION_NAMESERVERS_NO_DEFAULT)
3678 add_default = 0;
3679
3680 if (flags & DNS_OPTION_HOSTSFILE) {
3681 char *fname = evdns_get_default_hosts_filename();
3682 evdns_base_load_hosts(base, fname);
3683 if (fname)
3684 mm_free(fname);
3685 }
3686
3687 if (!filename) {
3688 evdns_resolv_set_defaults(base, flags);
3689 return 1;
3690 }
3691
3692 if ((err = evutil_read_file_(filename, &resolv, &n, 0)) < 0) {
3693 if (err == -1) {
3694 /* No file. */
3695 evdns_resolv_set_defaults(base, flags);
3696 return 1;
3697 } else {
3698 return 2;
3699 }
3700 }
3701
3702 start = resolv;
3703 for (;;) {
3704 char *const newline = strchr(start, '\n');
3705 if (!newline) {
3706 resolv_conf_parse_line(base, start, flags);
3707 break;
3708 } else {
3709 *newline = 0;
3710 resolv_conf_parse_line(base, start, flags);
3711 start = newline + 1;
3712 }
3713 }
3714
3715 if (!base->server_head && add_default) {
3716 /* no nameservers were configured. */
3717 evdns_base_nameserver_ip_add(base, "127.0.0.1");
3718 err = 6;
3719 }
3720 if (flags & DNS_OPTION_SEARCH && (!base->global_search_state || base->global_search_state->num_domains == 0)) {
3721 search_set_from_hostname(base);
3722 }
3723
3724 mm_free(resolv);
3725 return err;
3726 }
3727
3728 int
evdns_resolv_conf_parse(int flags,const char * const filename)3729 evdns_resolv_conf_parse(int flags, const char *const filename) {
3730 if (!current_base)
3731 current_base = evdns_base_new(NULL, 0);
3732 return evdns_base_resolv_conf_parse(current_base, flags, filename);
3733 }
3734
3735
3736 #ifdef _WIN32
3737 /* Add multiple nameservers from a space-or-comma-separated list. */
3738 static int
evdns_nameserver_ip_add_line(struct evdns_base * base,const char * ips)3739 evdns_nameserver_ip_add_line(struct evdns_base *base, const char *ips) {
3740 const char *addr;
3741 char *buf;
3742 int r;
3743 ASSERT_LOCKED(base);
3744 while (*ips) {
3745 while (isspace(*ips) || *ips == ',' || *ips == '\t')
3746 ++ips;
3747 addr = ips;
3748 while (isdigit(*ips) || *ips == '.' || *ips == ':' ||
3749 *ips=='[' || *ips==']')
3750 ++ips;
3751 buf = mm_malloc(ips-addr+1);
3752 if (!buf) return 4;
3753 memcpy(buf, addr, ips-addr);
3754 buf[ips-addr] = '\0';
3755 r = evdns_base_nameserver_ip_add(base, buf);
3756 mm_free(buf);
3757 if (r) return r;
3758 }
3759 return 0;
3760 }
3761
3762 typedef DWORD(WINAPI *GetNetworkParams_fn_t)(FIXED_INFO *, DWORD*);
3763
3764 /* Use the windows GetNetworkParams interface in iphlpapi.dll to */
3765 /* figure out what our nameservers are. */
3766 static int
load_nameservers_with_getnetworkparams(struct evdns_base * base)3767 load_nameservers_with_getnetworkparams(struct evdns_base *base)
3768 {
3769 /* Based on MSDN examples and inspection of c-ares code. */
3770 FIXED_INFO *fixed;
3771 HMODULE handle = 0;
3772 ULONG size = sizeof(FIXED_INFO);
3773 void *buf = NULL;
3774 int status = 0, r, added_any;
3775 IP_ADDR_STRING *ns;
3776 GetNetworkParams_fn_t fn;
3777
3778 ASSERT_LOCKED(base);
3779 if (!(handle = evutil_load_windows_system_library_(
3780 TEXT("iphlpapi.dll")))) {
3781 log(EVDNS_LOG_WARN, "Could not open iphlpapi.dll");
3782 status = -1;
3783 goto done;
3784 }
3785 if (!(fn = (GetNetworkParams_fn_t) GetProcAddress(handle, "GetNetworkParams"))) {
3786 log(EVDNS_LOG_WARN, "Could not get address of function.");
3787 status = -1;
3788 goto done;
3789 }
3790
3791 buf = mm_malloc(size);
3792 if (!buf) { status = 4; goto done; }
3793 fixed = buf;
3794 r = fn(fixed, &size);
3795 if (r != ERROR_SUCCESS && r != ERROR_BUFFER_OVERFLOW) {
3796 status = -1;
3797 goto done;
3798 }
3799 if (r != ERROR_SUCCESS) {
3800 mm_free(buf);
3801 buf = mm_malloc(size);
3802 if (!buf) { status = 4; goto done; }
3803 fixed = buf;
3804 r = fn(fixed, &size);
3805 if (r != ERROR_SUCCESS) {
3806 log(EVDNS_LOG_DEBUG, "fn() failed.");
3807 status = -1;
3808 goto done;
3809 }
3810 }
3811
3812 EVUTIL_ASSERT(fixed);
3813 added_any = 0;
3814 ns = &(fixed->DnsServerList);
3815 while (ns) {
3816 r = evdns_nameserver_ip_add_line(base, ns->IpAddress.String);
3817 if (r) {
3818 log(EVDNS_LOG_DEBUG,"Could not add nameserver %s to list,error: %d",
3819 (ns->IpAddress.String),(int)GetLastError());
3820 status = r;
3821 } else {
3822 ++added_any;
3823 log(EVDNS_LOG_DEBUG,"Successfully added %s as nameserver",ns->IpAddress.String);
3824 }
3825
3826 ns = ns->Next;
3827 }
3828
3829 if (!added_any) {
3830 log(EVDNS_LOG_DEBUG, "No nameservers added.");
3831 if (status == 0)
3832 status = -1;
3833 } else {
3834 status = 0;
3835 }
3836
3837 done:
3838 if (buf)
3839 mm_free(buf);
3840 if (handle)
3841 FreeLibrary(handle);
3842 return status;
3843 }
3844
3845 static int
config_nameserver_from_reg_key(struct evdns_base * base,HKEY key,const TCHAR * subkey)3846 config_nameserver_from_reg_key(struct evdns_base *base, HKEY key, const TCHAR *subkey)
3847 {
3848 char *buf;
3849 DWORD bufsz = 0, type = 0;
3850 int status = 0;
3851
3852 ASSERT_LOCKED(base);
3853 if (RegQueryValueEx(key, subkey, 0, &type, NULL, &bufsz)
3854 != ERROR_MORE_DATA)
3855 return -1;
3856 if (!(buf = mm_malloc(bufsz)))
3857 return -1;
3858
3859 if (RegQueryValueEx(key, subkey, 0, &type, (LPBYTE)buf, &bufsz)
3860 == ERROR_SUCCESS && bufsz > 1) {
3861 status = evdns_nameserver_ip_add_line(base,buf);
3862 }
3863
3864 mm_free(buf);
3865 return status;
3866 }
3867
3868 #define SERVICES_KEY TEXT("System\\CurrentControlSet\\Services\\")
3869 #define WIN_NS_9X_KEY SERVICES_KEY TEXT("VxD\\MSTCP")
3870 #define WIN_NS_NT_KEY SERVICES_KEY TEXT("Tcpip\\Parameters")
3871
3872 static int
load_nameservers_from_registry(struct evdns_base * base)3873 load_nameservers_from_registry(struct evdns_base *base)
3874 {
3875 int found = 0;
3876 int r;
3877 #define TRY(k, name) \
3878 if (!found && config_nameserver_from_reg_key(base,k,TEXT(name)) == 0) { \
3879 log(EVDNS_LOG_DEBUG,"Found nameservers in %s/%s",#k,name); \
3880 found = 1; \
3881 } else if (!found) { \
3882 log(EVDNS_LOG_DEBUG,"Didn't find nameservers in %s/%s", \
3883 #k,#name); \
3884 }
3885
3886 ASSERT_LOCKED(base);
3887
3888 if (((int)GetVersion()) > 0) { /* NT */
3889 HKEY nt_key = 0, interfaces_key = 0;
3890
3891 if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0,
3892 KEY_READ, &nt_key) != ERROR_SUCCESS) {
3893 log(EVDNS_LOG_DEBUG,"Couldn't open nt key, %d",(int)GetLastError());
3894 return -1;
3895 }
3896 r = RegOpenKeyEx(nt_key, TEXT("Interfaces"), 0,
3897 KEY_QUERY_VALUE|KEY_ENUMERATE_SUB_KEYS,
3898 &interfaces_key);
3899 if (r != ERROR_SUCCESS) {
3900 log(EVDNS_LOG_DEBUG,"Couldn't open interfaces key, %d",(int)GetLastError());
3901 return -1;
3902 }
3903 TRY(nt_key, "NameServer");
3904 TRY(nt_key, "DhcpNameServer");
3905 TRY(interfaces_key, "NameServer");
3906 TRY(interfaces_key, "DhcpNameServer");
3907 RegCloseKey(interfaces_key);
3908 RegCloseKey(nt_key);
3909 } else {
3910 HKEY win_key = 0;
3911 if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_9X_KEY, 0,
3912 KEY_READ, &win_key) != ERROR_SUCCESS) {
3913 log(EVDNS_LOG_DEBUG, "Couldn't open registry key, %d", (int)GetLastError());
3914 return -1;
3915 }
3916 TRY(win_key, "NameServer");
3917 RegCloseKey(win_key);
3918 }
3919
3920 if (found == 0) {
3921 log(EVDNS_LOG_WARN,"Didn't find any nameservers.");
3922 }
3923
3924 return found ? 0 : -1;
3925 #undef TRY
3926 }
3927
3928 int
evdns_base_config_windows_nameservers(struct evdns_base * base)3929 evdns_base_config_windows_nameservers(struct evdns_base *base)
3930 {
3931 int r;
3932 char *fname;
3933 if (base == NULL)
3934 base = current_base;
3935 if (base == NULL)
3936 return -1;
3937 EVDNS_LOCK(base);
3938 fname = evdns_get_default_hosts_filename();
3939 log(EVDNS_LOG_DEBUG, "Loading hosts entries from %s", fname);
3940 evdns_base_load_hosts(base, fname);
3941 if (fname)
3942 mm_free(fname);
3943
3944 if (load_nameservers_with_getnetworkparams(base) == 0) {
3945 EVDNS_UNLOCK(base);
3946 return 0;
3947 }
3948 r = load_nameservers_from_registry(base);
3949
3950 EVDNS_UNLOCK(base);
3951 return r;
3952 }
3953
3954 int
evdns_config_windows_nameservers(void)3955 evdns_config_windows_nameservers(void)
3956 {
3957 if (!current_base) {
3958 current_base = evdns_base_new(NULL, 1);
3959 return current_base == NULL ? -1 : 0;
3960 } else {
3961 return evdns_base_config_windows_nameservers(current_base);
3962 }
3963 }
3964 #endif
3965
3966 struct evdns_base *
evdns_base_new(struct event_base * event_base,int flags)3967 evdns_base_new(struct event_base *event_base, int flags)
3968 {
3969 struct evdns_base *base;
3970
3971 if (evutil_secure_rng_init() < 0) {
3972 log(EVDNS_LOG_WARN, "Unable to seed random number generator; "
3973 "DNS can't run.");
3974 return NULL;
3975 }
3976
3977 /* Give the evutil library a hook into its evdns-enabled
3978 * functionality. We can't just call evdns_getaddrinfo directly or
3979 * else libevent-core will depend on libevent-extras. */
3980 evutil_set_evdns_getaddrinfo_fn_(evdns_getaddrinfo);
3981 evutil_set_evdns_getaddrinfo_cancel_fn_(evdns_getaddrinfo_cancel);
3982
3983 base = mm_malloc(sizeof(struct evdns_base));
3984 if (base == NULL)
3985 return (NULL);
3986 memset(base, 0, sizeof(struct evdns_base));
3987 base->req_waiting_head = NULL;
3988
3989 EVTHREAD_ALLOC_LOCK(base->lock, EVTHREAD_LOCKTYPE_RECURSIVE);
3990 EVDNS_LOCK(base);
3991
3992 /* Set max requests inflight and allocate req_heads. */
3993 base->req_heads = NULL;
3994
3995 evdns_base_set_max_requests_inflight(base, 64);
3996
3997 base->server_head = NULL;
3998 base->event_base = event_base;
3999 base->global_good_nameservers = base->global_requests_inflight =
4000 base->global_requests_waiting = 0;
4001
4002 base->global_timeout.tv_sec = 5;
4003 base->global_timeout.tv_usec = 0;
4004 base->global_max_reissues = 1;
4005 base->global_max_retransmits = 3;
4006 base->global_max_nameserver_timeout = 3;
4007 base->global_search_state = NULL;
4008 base->global_randomize_case = 1;
4009 base->global_getaddrinfo_allow_skew.tv_sec = 3;
4010 base->global_getaddrinfo_allow_skew.tv_usec = 0;
4011 base->global_nameserver_probe_initial_timeout.tv_sec = 10;
4012 base->global_nameserver_probe_initial_timeout.tv_usec = 0;
4013
4014 TAILQ_INIT(&base->hostsdb);
4015
4016 #define EVDNS_BASE_ALL_FLAGS ( \
4017 EVDNS_BASE_INITIALIZE_NAMESERVERS | \
4018 EVDNS_BASE_DISABLE_WHEN_INACTIVE | \
4019 EVDNS_BASE_NAMESERVERS_NO_DEFAULT | \
4020 0)
4021
4022 if (flags & ~EVDNS_BASE_ALL_FLAGS) {
4023 flags = EVDNS_BASE_INITIALIZE_NAMESERVERS;
4024 log(EVDNS_LOG_WARN,
4025 "Unrecognized flag passed to evdns_base_new(). Assuming "
4026 "you meant EVDNS_BASE_INITIALIZE_NAMESERVERS.");
4027 }
4028 #undef EVDNS_BASE_ALL_FLAGS
4029
4030 if (flags & EVDNS_BASE_INITIALIZE_NAMESERVERS) {
4031 int r;
4032 int opts = DNS_OPTIONS_ALL;
4033 if (flags & EVDNS_BASE_NAMESERVERS_NO_DEFAULT) {
4034 opts |= DNS_OPTION_NAMESERVERS_NO_DEFAULT;
4035 }
4036
4037 #ifdef _WIN32
4038 r = evdns_base_config_windows_nameservers(base);
4039 #else
4040 r = evdns_base_resolv_conf_parse(base, opts, "/etc/resolv.conf");
4041 #endif
4042 if (r) {
4043 evdns_base_free_and_unlock(base, 0);
4044 return NULL;
4045 }
4046 }
4047 if (flags & EVDNS_BASE_DISABLE_WHEN_INACTIVE) {
4048 base->disable_when_inactive = 1;
4049 }
4050
4051 EVDNS_UNLOCK(base);
4052 return base;
4053 }
4054
4055 int
evdns_init(void)4056 evdns_init(void)
4057 {
4058 struct evdns_base *base = evdns_base_new(NULL, 1);
4059 if (base) {
4060 current_base = base;
4061 return 0;
4062 } else {
4063 return -1;
4064 }
4065 }
4066
4067 const char *
evdns_err_to_string(int err)4068 evdns_err_to_string(int err)
4069 {
4070 switch (err) {
4071 case DNS_ERR_NONE: return "no error";
4072 case DNS_ERR_FORMAT: return "misformatted query";
4073 case DNS_ERR_SERVERFAILED: return "server failed";
4074 case DNS_ERR_NOTEXIST: return "name does not exist";
4075 case DNS_ERR_NOTIMPL: return "query not implemented";
4076 case DNS_ERR_REFUSED: return "refused";
4077
4078 case DNS_ERR_TRUNCATED: return "reply truncated or ill-formed";
4079 case DNS_ERR_UNKNOWN: return "unknown";
4080 case DNS_ERR_TIMEOUT: return "request timed out";
4081 case DNS_ERR_SHUTDOWN: return "dns subsystem shut down";
4082 case DNS_ERR_CANCEL: return "dns request canceled";
4083 case DNS_ERR_NODATA: return "no records in the reply";
4084 default: return "[Unknown error code]";
4085 }
4086 }
4087
4088 static void
evdns_nameserver_free(struct nameserver * server)4089 evdns_nameserver_free(struct nameserver *server)
4090 {
4091 if (server->socket >= 0)
4092 evutil_closesocket(server->socket);
4093 (void) event_del(&server->event);
4094 event_debug_unassign(&server->event);
4095 if (server->state == 0)
4096 (void) event_del(&server->timeout_event);
4097 if (server->probe_request) {
4098 evdns_cancel_request(server->base, server->probe_request);
4099 server->probe_request = NULL;
4100 }
4101 event_debug_unassign(&server->timeout_event);
4102 mm_free(server);
4103 }
4104
4105 static void
evdns_base_free_and_unlock(struct evdns_base * base,int fail_requests)4106 evdns_base_free_and_unlock(struct evdns_base *base, int fail_requests)
4107 {
4108 struct nameserver *server, *server_next;
4109 struct search_domain *dom, *dom_next;
4110 int i;
4111
4112 /* Requires that we hold the lock. */
4113
4114 /* TODO(nickm) we might need to refcount here. */
4115
4116 while (base->req_waiting_head) {
4117 if (fail_requests)
4118 reply_schedule_callback(base->req_waiting_head, 0, DNS_ERR_SHUTDOWN, NULL);
4119 request_finished(base->req_waiting_head, &base->req_waiting_head, 1);
4120 }
4121 for (i = 0; i < base->n_req_heads; ++i) {
4122 while (base->req_heads[i]) {
4123 if (fail_requests)
4124 reply_schedule_callback(base->req_heads[i], 0, DNS_ERR_SHUTDOWN, NULL);
4125 request_finished(base->req_heads[i], &REQ_HEAD(base, base->req_heads[i]->trans_id), 1);
4126 }
4127 }
4128 base->global_requests_inflight = base->global_requests_waiting = 0;
4129
4130 for (server = base->server_head; server; server = server_next) {
4131 server_next = server->next;
4132 /** already done something before */
4133 server->probe_request = NULL;
4134 evdns_nameserver_free(server);
4135 if (server_next == base->server_head)
4136 break;
4137 }
4138 base->server_head = NULL;
4139 base->global_good_nameservers = 0;
4140
4141 if (base->global_search_state) {
4142 for (dom = base->global_search_state->head; dom; dom = dom_next) {
4143 dom_next = dom->next;
4144 mm_free(dom);
4145 }
4146 mm_free(base->global_search_state);
4147 base->global_search_state = NULL;
4148 }
4149
4150 {
4151 struct hosts_entry *victim;
4152 while ((victim = TAILQ_FIRST(&base->hostsdb))) {
4153 TAILQ_REMOVE(&base->hostsdb, victim, next);
4154 mm_free(victim);
4155 }
4156 }
4157
4158 mm_free(base->req_heads);
4159
4160 EVDNS_UNLOCK(base);
4161 EVTHREAD_FREE_LOCK(base->lock, EVTHREAD_LOCKTYPE_RECURSIVE);
4162
4163 mm_free(base);
4164 }
4165
4166 void
evdns_base_free(struct evdns_base * base,int fail_requests)4167 evdns_base_free(struct evdns_base *base, int fail_requests)
4168 {
4169 EVDNS_LOCK(base);
4170 evdns_base_free_and_unlock(base, fail_requests);
4171 }
4172
4173 void
evdns_base_clear_host_addresses(struct evdns_base * base)4174 evdns_base_clear_host_addresses(struct evdns_base *base)
4175 {
4176 struct hosts_entry *victim;
4177 EVDNS_LOCK(base);
4178 while ((victim = TAILQ_FIRST(&base->hostsdb))) {
4179 TAILQ_REMOVE(&base->hostsdb, victim, next);
4180 mm_free(victim);
4181 }
4182 EVDNS_UNLOCK(base);
4183 }
4184
4185 void
evdns_shutdown(int fail_requests)4186 evdns_shutdown(int fail_requests)
4187 {
4188 if (current_base) {
4189 struct evdns_base *b = current_base;
4190 current_base = NULL;
4191 evdns_base_free(b, fail_requests);
4192 }
4193 evdns_log_fn = NULL;
4194 }
4195
4196 static int
evdns_base_parse_hosts_line(struct evdns_base * base,char * line)4197 evdns_base_parse_hosts_line(struct evdns_base *base, char *line)
4198 {
4199 char *strtok_state;
4200 static const char *const delims = " \t";
4201 char *const addr = strtok_r(line, delims, &strtok_state);
4202 char *hostname, *hash;
4203 struct sockaddr_storage ss;
4204 int socklen = sizeof(ss);
4205 ASSERT_LOCKED(base);
4206
4207 #define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state)
4208
4209 if (!addr || *addr == '#')
4210 return 0;
4211
4212 memset(&ss, 0, sizeof(ss));
4213 if (evutil_parse_sockaddr_port(addr, (struct sockaddr*)&ss, &socklen)<0)
4214 return -1;
4215 if (socklen > (int)sizeof(struct sockaddr_in6))
4216 return -1;
4217
4218 if (sockaddr_getport((struct sockaddr*)&ss))
4219 return -1;
4220
4221 while ((hostname = NEXT_TOKEN)) {
4222 struct hosts_entry *he;
4223 size_t namelen;
4224 if ((hash = strchr(hostname, '#'))) {
4225 if (hash == hostname)
4226 return 0;
4227 *hash = '\0';
4228 }
4229
4230 namelen = strlen(hostname);
4231
4232 he = mm_calloc(1, sizeof(struct hosts_entry)+namelen);
4233 if (!he)
4234 return -1;
4235 EVUTIL_ASSERT(socklen <= (int)sizeof(he->addr));
4236 memcpy(&he->addr, &ss, socklen);
4237 memcpy(he->hostname, hostname, namelen+1);
4238 he->addrlen = socklen;
4239
4240 TAILQ_INSERT_TAIL(&base->hostsdb, he, next);
4241
4242 if (hash)
4243 return 0;
4244 }
4245
4246 return 0;
4247 #undef NEXT_TOKEN
4248 }
4249
4250 static int
evdns_base_load_hosts_impl(struct evdns_base * base,const char * hosts_fname)4251 evdns_base_load_hosts_impl(struct evdns_base *base, const char *hosts_fname)
4252 {
4253 char *str=NULL, *cp, *eol;
4254 size_t len;
4255 int err=0;
4256
4257 ASSERT_LOCKED(base);
4258
4259 if (hosts_fname == NULL ||
4260 (err = evutil_read_file_(hosts_fname, &str, &len, 0)) < 0) {
4261 char tmp[64];
4262 strlcpy(tmp, "127.0.0.1 localhost", sizeof(tmp));
4263 evdns_base_parse_hosts_line(base, tmp);
4264 strlcpy(tmp, "::1 localhost", sizeof(tmp));
4265 evdns_base_parse_hosts_line(base, tmp);
4266 return err ? -1 : 0;
4267 }
4268
4269 /* This will break early if there is a NUL in the hosts file.
4270 * Probably not a problem.*/
4271 cp = str;
4272 for (;;) {
4273 eol = strchr(cp, '\n');
4274
4275 if (eol) {
4276 *eol = '\0';
4277 evdns_base_parse_hosts_line(base, cp);
4278 cp = eol+1;
4279 } else {
4280 evdns_base_parse_hosts_line(base, cp);
4281 break;
4282 }
4283 }
4284
4285 mm_free(str);
4286 return 0;
4287 }
4288
4289 int
evdns_base_load_hosts(struct evdns_base * base,const char * hosts_fname)4290 evdns_base_load_hosts(struct evdns_base *base, const char *hosts_fname)
4291 {
4292 int res;
4293 if (!base)
4294 base = current_base;
4295 EVDNS_LOCK(base);
4296 res = evdns_base_load_hosts_impl(base, hosts_fname);
4297 EVDNS_UNLOCK(base);
4298 return res;
4299 }
4300
4301 /* A single request for a getaddrinfo, either v4 or v6. */
4302 struct getaddrinfo_subrequest {
4303 struct evdns_request *r;
4304 ev_uint32_t type;
4305 };
4306
4307 /* State data used to implement an in-progress getaddrinfo. */
4308 struct evdns_getaddrinfo_request {
4309 struct evdns_base *evdns_base;
4310 /* Copy of the modified 'hints' data that we'll use to build
4311 * answers. */
4312 struct evutil_addrinfo hints;
4313 /* The callback to invoke when we're done */
4314 evdns_getaddrinfo_cb user_cb;
4315 /* User-supplied data to give to the callback. */
4316 void *user_data;
4317 /* The port to use when building sockaddrs. */
4318 ev_uint16_t port;
4319 /* The sub_request for an A record (if any) */
4320 struct getaddrinfo_subrequest ipv4_request;
4321 /* The sub_request for an AAAA record (if any) */
4322 struct getaddrinfo_subrequest ipv6_request;
4323
4324 /* The cname result that we were told (if any) */
4325 char *cname_result;
4326
4327 /* If we have one request answered and one request still inflight,
4328 * then this field holds the answer from the first request... */
4329 struct evutil_addrinfo *pending_result;
4330 /* And this event is a timeout that will tell us to cancel the second
4331 * request if it's taking a long time. */
4332 struct event timeout;
4333
4334 /* And this field holds the error code from the first request... */
4335 int pending_error;
4336 /* If this is set, the user canceled this request. */
4337 unsigned user_canceled : 1;
4338 /* If this is set, the user can no longer cancel this request; we're
4339 * just waiting for the free. */
4340 unsigned request_done : 1;
4341 };
4342
4343 /* Convert an evdns errors to the equivalent getaddrinfo error. */
4344 static int
evdns_err_to_getaddrinfo_err(int e1)4345 evdns_err_to_getaddrinfo_err(int e1)
4346 {
4347 /* XXX Do this better! */
4348 if (e1 == DNS_ERR_NONE)
4349 return 0;
4350 else if (e1 == DNS_ERR_NOTEXIST)
4351 return EVUTIL_EAI_NONAME;
4352 else
4353 return EVUTIL_EAI_FAIL;
4354 }
4355
4356 /* Return the more informative of two getaddrinfo errors. */
4357 static int
getaddrinfo_merge_err(int e1,int e2)4358 getaddrinfo_merge_err(int e1, int e2)
4359 {
4360 /* XXXX be cleverer here. */
4361 if (e1 == 0)
4362 return e2;
4363 else
4364 return e1;
4365 }
4366
4367 static void
free_getaddrinfo_request(struct evdns_getaddrinfo_request * data)4368 free_getaddrinfo_request(struct evdns_getaddrinfo_request *data)
4369 {
4370 /* DO NOT CALL this if either of the requests is pending. Only once
4371 * both callbacks have been invoked is it safe to free the request */
4372 if (data->pending_result)
4373 evutil_freeaddrinfo(data->pending_result);
4374 if (data->cname_result)
4375 mm_free(data->cname_result);
4376 event_del(&data->timeout);
4377 mm_free(data);
4378 return;
4379 }
4380
4381 static void
add_cname_to_reply(struct evdns_getaddrinfo_request * data,struct evutil_addrinfo * ai)4382 add_cname_to_reply(struct evdns_getaddrinfo_request *data,
4383 struct evutil_addrinfo *ai)
4384 {
4385 if (data->cname_result && ai) {
4386 ai->ai_canonname = data->cname_result;
4387 data->cname_result = NULL;
4388 }
4389 }
4390
4391 /* Callback: invoked when one request in a mixed-format A/AAAA getaddrinfo
4392 * request has finished, but the other one took too long to answer. Pass
4393 * along the answer we got, and cancel the other request.
4394 */
4395 static void
evdns_getaddrinfo_timeout_cb(evutil_socket_t fd,short what,void * ptr)4396 evdns_getaddrinfo_timeout_cb(evutil_socket_t fd, short what, void *ptr)
4397 {
4398 int v4_timedout = 0, v6_timedout = 0;
4399 struct evdns_getaddrinfo_request *data = ptr;
4400
4401 /* Cancel any pending requests, and note which one */
4402 if (data->ipv4_request.r) {
4403 /* XXXX This does nothing if the request's callback is already
4404 * running (pending_cb is set). */
4405 evdns_cancel_request(NULL, data->ipv4_request.r);
4406 v4_timedout = 1;
4407 EVDNS_LOCK(data->evdns_base);
4408 ++data->evdns_base->getaddrinfo_ipv4_timeouts;
4409 EVDNS_UNLOCK(data->evdns_base);
4410 }
4411 if (data->ipv6_request.r) {
4412 /* XXXX This does nothing if the request's callback is already
4413 * running (pending_cb is set). */
4414 evdns_cancel_request(NULL, data->ipv6_request.r);
4415 v6_timedout = 1;
4416 EVDNS_LOCK(data->evdns_base);
4417 ++data->evdns_base->getaddrinfo_ipv6_timeouts;
4418 EVDNS_UNLOCK(data->evdns_base);
4419 }
4420
4421 /* We only use this timeout callback when we have an answer for
4422 * one address. */
4423 EVUTIL_ASSERT(!v4_timedout || !v6_timedout);
4424
4425 /* Report the outcome of the other request that didn't time out. */
4426 if (data->pending_result) {
4427 add_cname_to_reply(data, data->pending_result);
4428 data->user_cb(0, data->pending_result, data->user_data);
4429 data->pending_result = NULL;
4430 } else {
4431 int e = data->pending_error;
4432 if (!e)
4433 e = EVUTIL_EAI_AGAIN;
4434 data->user_cb(e, NULL, data->user_data);
4435 }
4436
4437 data->user_cb = NULL; /* prevent double-call if evdns callbacks are
4438 * in-progress. XXXX It would be better if this
4439 * weren't necessary. */
4440
4441 if (!v4_timedout && !v6_timedout) {
4442 /* should be impossible? XXXX */
4443 free_getaddrinfo_request(data);
4444 }
4445 }
4446
4447 static int
evdns_getaddrinfo_set_timeout(struct evdns_base * evdns_base,struct evdns_getaddrinfo_request * data)4448 evdns_getaddrinfo_set_timeout(struct evdns_base *evdns_base,
4449 struct evdns_getaddrinfo_request *data)
4450 {
4451 return event_add(&data->timeout, &evdns_base->global_getaddrinfo_allow_skew);
4452 }
4453
4454 static inline int
evdns_result_is_answer(int result)4455 evdns_result_is_answer(int result)
4456 {
4457 return (result != DNS_ERR_NOTIMPL && result != DNS_ERR_REFUSED &&
4458 result != DNS_ERR_SERVERFAILED && result != DNS_ERR_CANCEL);
4459 }
4460
4461 static void
evdns_getaddrinfo_gotresolve(int result,char type,int count,int ttl,void * addresses,void * arg)4462 evdns_getaddrinfo_gotresolve(int result, char type, int count,
4463 int ttl, void *addresses, void *arg)
4464 {
4465 int i;
4466 struct getaddrinfo_subrequest *req = arg;
4467 struct getaddrinfo_subrequest *other_req;
4468 struct evdns_getaddrinfo_request *data;
4469
4470 struct evutil_addrinfo *res;
4471
4472 struct sockaddr_in sin;
4473 struct sockaddr_in6 sin6;
4474 struct sockaddr *sa;
4475 int socklen, addrlen;
4476 void *addrp;
4477 int err;
4478 int user_canceled;
4479
4480 EVUTIL_ASSERT(req->type == DNS_IPv4_A || req->type == DNS_IPv6_AAAA);
4481 if (req->type == DNS_IPv4_A) {
4482 data = EVUTIL_UPCAST(req, struct evdns_getaddrinfo_request, ipv4_request);
4483 other_req = &data->ipv6_request;
4484 } else {
4485 data = EVUTIL_UPCAST(req, struct evdns_getaddrinfo_request, ipv6_request);
4486 other_req = &data->ipv4_request;
4487 }
4488
4489 /** Called from evdns_base_free() with @fail_requests == 1 */
4490 if (result != DNS_ERR_SHUTDOWN) {
4491 EVDNS_LOCK(data->evdns_base);
4492 if (evdns_result_is_answer(result)) {
4493 if (req->type == DNS_IPv4_A)
4494 ++data->evdns_base->getaddrinfo_ipv4_answered;
4495 else
4496 ++data->evdns_base->getaddrinfo_ipv6_answered;
4497 }
4498 user_canceled = data->user_canceled;
4499 if (other_req->r == NULL)
4500 data->request_done = 1;
4501 EVDNS_UNLOCK(data->evdns_base);
4502 } else {
4503 data->evdns_base = NULL;
4504 user_canceled = data->user_canceled;
4505 }
4506
4507 req->r = NULL;
4508
4509 if (result == DNS_ERR_CANCEL && ! user_canceled) {
4510 /* Internal cancel request from timeout or internal error.
4511 * we already answered the user. */
4512 if (other_req->r == NULL)
4513 free_getaddrinfo_request(data);
4514 return;
4515 }
4516
4517 if (data->user_cb == NULL) {
4518 /* We already answered. XXXX This shouldn't be needed; see
4519 * comments in evdns_getaddrinfo_timeout_cb */
4520 free_getaddrinfo_request(data);
4521 return;
4522 }
4523
4524 if (result == DNS_ERR_NONE) {
4525 if (count == 0)
4526 err = EVUTIL_EAI_NODATA;
4527 else
4528 err = 0;
4529 } else {
4530 err = evdns_err_to_getaddrinfo_err(result);
4531 }
4532
4533 if (err) {
4534 /* Looks like we got an error. */
4535 if (other_req->r) {
4536 /* The other request is still working; maybe it will
4537 * succeed. */
4538 /* XXXX handle failure from set_timeout */
4539 if (result != DNS_ERR_SHUTDOWN) {
4540 evdns_getaddrinfo_set_timeout(data->evdns_base, data);
4541 }
4542 data->pending_error = err;
4543 return;
4544 }
4545
4546 if (user_canceled) {
4547 data->user_cb(EVUTIL_EAI_CANCEL, NULL, data->user_data);
4548 } else if (data->pending_result) {
4549 /* If we have an answer waiting, and we weren't
4550 * canceled, ignore this error. */
4551 add_cname_to_reply(data, data->pending_result);
4552 data->user_cb(0, data->pending_result, data->user_data);
4553 data->pending_result = NULL;
4554 } else {
4555 if (data->pending_error)
4556 err = getaddrinfo_merge_err(err,
4557 data->pending_error);
4558 data->user_cb(err, NULL, data->user_data);
4559 }
4560 free_getaddrinfo_request(data);
4561 return;
4562 } else if (user_canceled) {
4563 if (other_req->r) {
4564 /* The other request is still working; let it hit this
4565 * callback with EVUTIL_EAI_CANCEL callback and report
4566 * the failure. */
4567 return;
4568 }
4569 data->user_cb(EVUTIL_EAI_CANCEL, NULL, data->user_data);
4570 free_getaddrinfo_request(data);
4571 return;
4572 }
4573
4574 /* Looks like we got some answers. We should turn them into addrinfos
4575 * and then either queue those or return them all. */
4576 EVUTIL_ASSERT(type == DNS_IPv4_A || type == DNS_IPv6_AAAA);
4577
4578 if (type == DNS_IPv4_A) {
4579 memset(&sin, 0, sizeof(sin));
4580 sin.sin_family = AF_INET;
4581 sin.sin_port = htons(data->port);
4582
4583 sa = (struct sockaddr *)&sin;
4584 socklen = sizeof(sin);
4585 addrlen = 4;
4586 addrp = &sin.sin_addr.s_addr;
4587 } else {
4588 memset(&sin6, 0, sizeof(sin6));
4589 sin6.sin6_family = AF_INET6;
4590 sin6.sin6_port = htons(data->port);
4591
4592 sa = (struct sockaddr *)&sin6;
4593 socklen = sizeof(sin6);
4594 addrlen = 16;
4595 addrp = &sin6.sin6_addr.s6_addr;
4596 }
4597
4598 res = NULL;
4599 for (i=0; i < count; ++i) {
4600 struct evutil_addrinfo *ai;
4601 memcpy(addrp, ((char*)addresses)+i*addrlen, addrlen);
4602 ai = evutil_new_addrinfo_(sa, socklen, &data->hints);
4603 if (!ai) {
4604 if (other_req->r) {
4605 evdns_cancel_request(NULL, other_req->r);
4606 }
4607 data->user_cb(EVUTIL_EAI_MEMORY, NULL, data->user_data);
4608 if (res)
4609 evutil_freeaddrinfo(res);
4610
4611 if (other_req->r == NULL)
4612 free_getaddrinfo_request(data);
4613 return;
4614 }
4615 res = evutil_addrinfo_append_(res, ai);
4616 }
4617
4618 if (other_req->r) {
4619 /* The other request is still in progress; wait for it */
4620 /* XXXX handle failure from set_timeout */
4621 evdns_getaddrinfo_set_timeout(data->evdns_base, data);
4622 data->pending_result = res;
4623 return;
4624 } else {
4625 /* The other request is done or never started; append its
4626 * results (if any) and return them. */
4627 if (data->pending_result) {
4628 if (req->type == DNS_IPv4_A)
4629 res = evutil_addrinfo_append_(res,
4630 data->pending_result);
4631 else
4632 res = evutil_addrinfo_append_(
4633 data->pending_result, res);
4634 data->pending_result = NULL;
4635 }
4636
4637 /* Call the user callback. */
4638 add_cname_to_reply(data, res);
4639 data->user_cb(0, res, data->user_data);
4640
4641 /* Free data. */
4642 free_getaddrinfo_request(data);
4643 }
4644 }
4645
4646 static struct hosts_entry *
find_hosts_entry(struct evdns_base * base,const char * hostname,struct hosts_entry * find_after)4647 find_hosts_entry(struct evdns_base *base, const char *hostname,
4648 struct hosts_entry *find_after)
4649 {
4650 struct hosts_entry *e;
4651
4652 if (find_after)
4653 e = TAILQ_NEXT(find_after, next);
4654 else
4655 e = TAILQ_FIRST(&base->hostsdb);
4656
4657 for (; e; e = TAILQ_NEXT(e, next)) {
4658 if (!evutil_ascii_strcasecmp(e->hostname, hostname))
4659 return e;
4660 }
4661 return NULL;
4662 }
4663
4664 static int
evdns_getaddrinfo_fromhosts(struct evdns_base * base,const char * nodename,struct evutil_addrinfo * hints,ev_uint16_t port,struct evutil_addrinfo ** res)4665 evdns_getaddrinfo_fromhosts(struct evdns_base *base,
4666 const char *nodename, struct evutil_addrinfo *hints, ev_uint16_t port,
4667 struct evutil_addrinfo **res)
4668 {
4669 int n_found = 0;
4670 struct hosts_entry *e;
4671 struct evutil_addrinfo *ai=NULL;
4672 int f = hints->ai_family;
4673
4674 EVDNS_LOCK(base);
4675 for (e = find_hosts_entry(base, nodename, NULL); e;
4676 e = find_hosts_entry(base, nodename, e)) {
4677 struct evutil_addrinfo *ai_new;
4678 ++n_found;
4679 if ((e->addr.sa.sa_family == AF_INET && f == PF_INET6) ||
4680 (e->addr.sa.sa_family == AF_INET6 && f == PF_INET))
4681 continue;
4682 ai_new = evutil_new_addrinfo_(&e->addr.sa, e->addrlen, hints);
4683 if (!ai_new) {
4684 n_found = 0;
4685 goto out;
4686 }
4687 sockaddr_setport(ai_new->ai_addr, port);
4688 ai = evutil_addrinfo_append_(ai, ai_new);
4689 }
4690 EVDNS_UNLOCK(base);
4691 out:
4692 if (n_found) {
4693 /* Note that we return an empty answer if we found entries for
4694 * this hostname but none were of the right address type. */
4695 *res = ai;
4696 return 0;
4697 } else {
4698 if (ai)
4699 evutil_freeaddrinfo(ai);
4700 return -1;
4701 }
4702 }
4703
4704 struct evdns_getaddrinfo_request *
evdns_getaddrinfo(struct evdns_base * dns_base,const char * nodename,const char * servname,const struct evutil_addrinfo * hints_in,evdns_getaddrinfo_cb cb,void * arg)4705 evdns_getaddrinfo(struct evdns_base *dns_base,
4706 const char *nodename, const char *servname,
4707 const struct evutil_addrinfo *hints_in,
4708 evdns_getaddrinfo_cb cb, void *arg)
4709 {
4710 struct evdns_getaddrinfo_request *data;
4711 struct evutil_addrinfo hints;
4712 struct evutil_addrinfo *res = NULL;
4713 int err;
4714 int port = 0;
4715 int want_cname = 0;
4716 int started = 0;
4717
4718 if (!dns_base) {
4719 dns_base = current_base;
4720 if (!dns_base) {
4721 log(EVDNS_LOG_WARN,
4722 "Call to getaddrinfo_async with no "
4723 "evdns_base configured.");
4724 cb(EVUTIL_EAI_FAIL, NULL, arg); /* ??? better error? */
4725 return NULL;
4726 }
4727 }
4728
4729 /* If we _must_ answer this immediately, do so. */
4730 if ((hints_in && (hints_in->ai_flags & EVUTIL_AI_NUMERICHOST))) {
4731 res = NULL;
4732 err = evutil_getaddrinfo(nodename, servname, hints_in, &res);
4733 cb(err, res, arg);
4734 return NULL;
4735 }
4736
4737 if (hints_in) {
4738 memcpy(&hints, hints_in, sizeof(hints));
4739 } else {
4740 memset(&hints, 0, sizeof(hints));
4741 hints.ai_family = PF_UNSPEC;
4742 }
4743
4744 evutil_adjust_hints_for_addrconfig_(&hints);
4745
4746 /* Now try to see if we _can_ answer immediately. */
4747 /* (It would be nice to do this by calling getaddrinfo directly, with
4748 * AI_NUMERICHOST, on plaforms that have it, but we can't: there isn't
4749 * a reliable way to distinguish the "that wasn't a numeric host!" case
4750 * from any other EAI_NONAME cases.) */
4751 err = evutil_getaddrinfo_common_(nodename, servname, &hints, &res, &port);
4752 if (err != EVUTIL_EAI_NEED_RESOLVE) {
4753 cb(err, res, arg);
4754 return NULL;
4755 }
4756
4757 /* If there is an entry in the hosts file, we should give it now. */
4758 if (!evdns_getaddrinfo_fromhosts(dns_base, nodename, &hints, port, &res)) {
4759 cb(0, res, arg);
4760 return NULL;
4761 }
4762
4763 /* Okay, things are serious now. We're going to need to actually
4764 * launch a request.
4765 */
4766 data = mm_calloc(1,sizeof(struct evdns_getaddrinfo_request));
4767 if (!data) {
4768 cb(EVUTIL_EAI_MEMORY, NULL, arg);
4769 return NULL;
4770 }
4771
4772 memcpy(&data->hints, &hints, sizeof(data->hints));
4773 data->port = (ev_uint16_t)port;
4774 data->ipv4_request.type = DNS_IPv4_A;
4775 data->ipv6_request.type = DNS_IPv6_AAAA;
4776 data->user_cb = cb;
4777 data->user_data = arg;
4778 data->evdns_base = dns_base;
4779
4780 want_cname = (hints.ai_flags & EVUTIL_AI_CANONNAME);
4781
4782 /* If we are asked for a PF_UNSPEC address, we launch two requests in
4783 * parallel: one for an A address and one for an AAAA address. We
4784 * can't send just one request, since many servers only answer one
4785 * question per DNS request.
4786 *
4787 * Once we have the answer to one request, we allow for a short
4788 * timeout before we report it, to see if the other one arrives. If
4789 * they both show up in time, then we report both the answers.
4790 *
4791 * If too many addresses of one type time out or fail, we should stop
4792 * launching those requests. (XXX we don't do that yet.)
4793 */
4794
4795 EVDNS_LOCK(dns_base);
4796
4797 if (hints.ai_family != PF_INET6) {
4798 log(EVDNS_LOG_DEBUG, "Sending request for %s on ipv4 as %p",
4799 nodename, &data->ipv4_request);
4800
4801 data->ipv4_request.r = evdns_base_resolve_ipv4(dns_base,
4802 nodename, 0, evdns_getaddrinfo_gotresolve,
4803 &data->ipv4_request);
4804 if (want_cname && data->ipv4_request.r)
4805 data->ipv4_request.r->current_req->put_cname_in_ptr =
4806 &data->cname_result;
4807 }
4808 if (hints.ai_family != PF_INET) {
4809 log(EVDNS_LOG_DEBUG, "Sending request for %s on ipv6 as %p",
4810 nodename, &data->ipv6_request);
4811
4812 data->ipv6_request.r = evdns_base_resolve_ipv6(dns_base,
4813 nodename, 0, evdns_getaddrinfo_gotresolve,
4814 &data->ipv6_request);
4815 if (want_cname && data->ipv6_request.r)
4816 data->ipv6_request.r->current_req->put_cname_in_ptr =
4817 &data->cname_result;
4818 }
4819
4820 evtimer_assign(&data->timeout, dns_base->event_base,
4821 evdns_getaddrinfo_timeout_cb, data);
4822
4823 started = (data->ipv4_request.r || data->ipv6_request.r);
4824
4825 EVDNS_UNLOCK(dns_base);
4826
4827 if (started) {
4828 return data;
4829 } else {
4830 mm_free(data);
4831 cb(EVUTIL_EAI_FAIL, NULL, arg);
4832 return NULL;
4833 }
4834 }
4835
4836 void
evdns_getaddrinfo_cancel(struct evdns_getaddrinfo_request * data)4837 evdns_getaddrinfo_cancel(struct evdns_getaddrinfo_request *data)
4838 {
4839 EVDNS_LOCK(data->evdns_base);
4840 if (data->request_done) {
4841 EVDNS_UNLOCK(data->evdns_base);
4842 return;
4843 }
4844 event_del(&data->timeout);
4845 data->user_canceled = 1;
4846 if (data->ipv4_request.r)
4847 evdns_cancel_request(data->evdns_base, data->ipv4_request.r);
4848 if (data->ipv6_request.r)
4849 evdns_cancel_request(data->evdns_base, data->ipv6_request.r);
4850 EVDNS_UNLOCK(data->evdns_base);
4851 }
4852