xref: /freebsd/contrib/libevent/evdns.c (revision a03411e84728e9b267056fd31c7d1d9d1dc1b01e)
1 /* Copyright 2006-2007 Niels Provos
2  * Copyright 2007-2012 Nick Mathewson and Niels Provos
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  * 1. Redistributions of source code must retain the above copyright
8  *    notice, this list of conditions and the following disclaimer.
9  * 2. Redistributions in binary form must reproduce the above copyright
10  *    notice, this list of conditions and the following disclaimer in the
11  *    documentation and/or other materials provided with the distribution.
12  * 3. The name of the author may not be used to endorse or promote products
13  *    derived from this software without specific prior written permission.
14  *
15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25  */
26 
27 /* Based on software by Adam Langly. Adam's original message:
28  *
29  * Async DNS Library
30  * Adam Langley <agl@imperialviolet.org>
31  * http://www.imperialviolet.org/eventdns.html
32  * Public Domain code
33  *
34  * This software is Public Domain. To view a copy of the public domain dedication,
35  * visit http://creativecommons.org/licenses/publicdomain/ or send a letter to
36  * Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.
37  *
38  * I ask and expect, but do not require, that all derivative works contain an
39  * attribution similar to:
40  *	Parts developed by Adam Langley <agl@imperialviolet.org>
41  *
42  * You may wish to replace the word "Parts" with something else depending on
43  * the amount of original code.
44  *
45  * (Derivative works does not include programs which link against, run or include
46  * the source verbatim in their source distributions)
47  *
48  * Version: 0.1b
49  */
50 
51 #include "event2/event-config.h"
52 #include "evconfig-private.h"
53 
54 #include <sys/types.h>
55 
56 #ifndef _FORTIFY_SOURCE
57 #define _FORTIFY_SOURCE 3
58 #endif
59 
60 #include <string.h>
61 #include <fcntl.h>
62 #ifdef EVENT__HAVE_SYS_TIME_H
63 #include <sys/time.h>
64 #endif
65 #ifdef EVENT__HAVE_STDINT_H
66 #include <stdint.h>
67 #endif
68 #include <stdlib.h>
69 #include <string.h>
70 #include <errno.h>
71 #ifdef EVENT__HAVE_UNISTD_H
72 #include <unistd.h>
73 #endif
74 #include <limits.h>
75 #include <sys/stat.h>
76 #include <stdio.h>
77 #include <stdarg.h>
78 #ifdef _WIN32
79 #include <winsock2.h>
80 #include <winerror.h>
81 #include <ws2tcpip.h>
82 #ifndef _WIN32_IE
83 #define _WIN32_IE 0x400
84 #endif
85 #include <shlobj.h>
86 #endif
87 
88 #include "event2/dns.h"
89 #include "event2/dns_struct.h"
90 #include "event2/dns_compat.h"
91 #include "event2/util.h"
92 #include "event2/event.h"
93 #include "event2/event_struct.h"
94 #include "event2/thread.h"
95 
96 #include "defer-internal.h"
97 #include "log-internal.h"
98 #include "mm-internal.h"
99 #include "strlcpy-internal.h"
100 #include "ipv6-internal.h"
101 #include "util-internal.h"
102 #include "evthread-internal.h"
103 #ifdef _WIN32
104 #include <ctype.h>
105 #include <winsock2.h>
106 #include <windows.h>
107 #include <iphlpapi.h>
108 #include <io.h>
109 #else
110 #include <sys/socket.h>
111 #include <netinet/in.h>
112 #include <arpa/inet.h>
113 #endif
114 
115 #ifdef EVENT__HAVE_NETINET_IN6_H
116 #include <netinet/in6.h>
117 #endif
118 
119 #define EVDNS_LOG_DEBUG EVENT_LOG_DEBUG
120 #define EVDNS_LOG_WARN EVENT_LOG_WARN
121 #define EVDNS_LOG_MSG EVENT_LOG_MSG
122 
123 #ifndef HOST_NAME_MAX
124 #define HOST_NAME_MAX 255
125 #endif
126 
127 #include <stdio.h>
128 
129 #undef MIN
130 #define MIN(a,b) ((a)<(b)?(a):(b))
131 
132 #define ASSERT_VALID_REQUEST(req) \
133 	EVUTIL_ASSERT((req)->handle && (req)->handle->current_req == (req))
134 
135 #define u64 ev_uint64_t
136 #define u32 ev_uint32_t
137 #define u16 ev_uint16_t
138 #define u8  ev_uint8_t
139 
140 /* maximum number of addresses from a single packet */
141 /* that we bother recording */
142 #define MAX_V4_ADDRS 32
143 #define MAX_V6_ADDRS 32
144 
145 
146 #define TYPE_A	       EVDNS_TYPE_A
147 #define TYPE_CNAME     5
148 #define TYPE_PTR       EVDNS_TYPE_PTR
149 #define TYPE_SOA       EVDNS_TYPE_SOA
150 #define TYPE_AAAA      EVDNS_TYPE_AAAA
151 
152 #define CLASS_INET     EVDNS_CLASS_INET
153 
154 /* Persistent handle.  We keep this separate from 'struct request' since we
155  * need some object to last for as long as an evdns_request is outstanding so
156  * that it can be canceled, whereas a search request can lead to multiple
157  * 'struct request' instances being created over its lifetime. */
158 struct evdns_request {
159 	struct request *current_req;
160 	struct evdns_base *base;
161 
162 	int pending_cb; /* Waiting for its callback to be invoked; not
163 			 * owned by event base any more. */
164 
165 	/* elements used by the searching code */
166 	int search_index;
167 	struct search_state *search_state;
168 	char *search_origname;	/* needs to be free()ed */
169 	int search_flags;
170 };
171 
172 struct request {
173 	u8 *request;  /* the dns packet data */
174 	u8 request_type; /* TYPE_PTR or TYPE_A or TYPE_AAAA */
175 	unsigned int request_len;
176 	int reissue_count;
177 	int tx_count;  /* the number of times that this packet has been sent */
178 	void *user_pointer;  /* the pointer given to us for this request */
179 	evdns_callback_type user_callback;
180 	struct nameserver *ns;	/* the server which we last sent it */
181 
182 	/* these objects are kept in a circular list */
183 	/* XXX We could turn this into a CIRCLEQ. */
184 	struct request *next, *prev;
185 
186 	struct event timeout_event;
187 
188 	u16 trans_id;  /* the transaction id */
189 	unsigned request_appended :1;	/* true if the request pointer is data which follows this struct */
190 	unsigned transmit_me :1;  /* needs to be transmitted */
191 
192 	/* XXXX This is a horrible hack. */
193 	char **put_cname_in_ptr; /* store the cname here if we get one. */
194 
195 	struct evdns_base *base;
196 
197 	struct evdns_request *handle;
198 };
199 
200 struct reply {
201 	unsigned int type;
202 	unsigned int have_answer : 1;
203 	union {
204 		struct {
205 			u32 addrcount;
206 			u32 addresses[MAX_V4_ADDRS];
207 		} a;
208 		struct {
209 			u32 addrcount;
210 			struct in6_addr addresses[MAX_V6_ADDRS];
211 		} aaaa;
212 		struct {
213 			char name[HOST_NAME_MAX];
214 		} ptr;
215 	} data;
216 };
217 
218 struct nameserver {
219 	evutil_socket_t socket;	 /* a connected UDP socket */
220 	struct sockaddr_storage address;
221 	ev_socklen_t addrlen;
222 	int failed_times;  /* number of times which we have given this server a chance */
223 	int timedout;  /* number of times in a row a request has timed out */
224 	struct event event;
225 	/* these objects are kept in a circular list */
226 	struct nameserver *next, *prev;
227 	struct event timeout_event;  /* used to keep the timeout for */
228 				     /* when we next probe this server. */
229 				     /* Valid if state == 0 */
230 	/* Outstanding probe request for this nameserver, if any */
231 	struct evdns_request *probe_request;
232 	char state;  /* zero if we think that this server is down */
233 	char choked;  /* true if we have an EAGAIN from this server's socket */
234 	char write_waiting;  /* true if we are waiting for EV_WRITE events */
235 	struct evdns_base *base;
236 
237 	/* Number of currently inflight requests: used
238 	 * to track when we should add/del the event. */
239 	int requests_inflight;
240 };
241 
242 
243 /* Represents a local port where we're listening for DNS requests. Right now, */
244 /* only UDP is supported. */
245 struct evdns_server_port {
246 	evutil_socket_t socket; /* socket we use to read queries and write replies. */
247 	int refcnt; /* reference count. */
248 	char choked; /* Are we currently blocked from writing? */
249 	char closing; /* Are we trying to close this port, pending writes? */
250 	evdns_request_callback_fn_type user_callback; /* Fn to handle requests */
251 	void *user_data; /* Opaque pointer passed to user_callback */
252 	struct event event; /* Read/write event */
253 	/* circular list of replies that we want to write. */
254 	struct server_request *pending_replies;
255 	struct event_base *event_base;
256 
257 #ifndef EVENT__DISABLE_THREAD_SUPPORT
258 	void *lock;
259 #endif
260 };
261 
262 /* Represents part of a reply being built.	(That is, a single RR.) */
263 struct server_reply_item {
264 	struct server_reply_item *next; /* next item in sequence. */
265 	char *name; /* name part of the RR */
266 	u16 type; /* The RR type */
267 	u16 class; /* The RR class (usually CLASS_INET) */
268 	u32 ttl; /* The RR TTL */
269 	char is_name; /* True iff data is a label */
270 	u16 datalen; /* Length of data; -1 if data is a label */
271 	void *data; /* The contents of the RR */
272 };
273 
274 /* Represents a request that we've received as a DNS server, and holds */
275 /* the components of the reply as we're constructing it. */
276 struct server_request {
277 	/* Pointers to the next and previous entries on the list of replies */
278 	/* that we're waiting to write.	 Only set if we have tried to respond */
279 	/* and gotten EAGAIN. */
280 	struct server_request *next_pending;
281 	struct server_request *prev_pending;
282 
283 	u16 trans_id; /* Transaction id. */
284 	struct evdns_server_port *port; /* Which port received this request on? */
285 	struct sockaddr_storage addr; /* Where to send the response */
286 	ev_socklen_t addrlen; /* length of addr */
287 
288 	int n_answer; /* how many answer RRs have been set? */
289 	int n_authority; /* how many authority RRs have been set? */
290 	int n_additional; /* how many additional RRs have been set? */
291 
292 	struct server_reply_item *answer; /* linked list of answer RRs */
293 	struct server_reply_item *authority; /* linked list of authority RRs */
294 	struct server_reply_item *additional; /* linked list of additional RRs */
295 
296 	/* Constructed response.  Only set once we're ready to send a reply. */
297 	/* Once this is set, the RR fields are cleared, and no more should be set. */
298 	char *response;
299 	size_t response_len;
300 
301 	/* Caller-visible fields: flags, questions. */
302 	struct evdns_server_request base;
303 };
304 
305 struct evdns_base {
306 	/* An array of n_req_heads circular lists for inflight requests.
307 	 * Each inflight request req is in req_heads[req->trans_id % n_req_heads].
308 	 */
309 	struct request **req_heads;
310 	/* A circular list of requests that we're waiting to send, but haven't
311 	 * sent yet because there are too many requests inflight */
312 	struct request *req_waiting_head;
313 	/* A circular list of nameservers. */
314 	struct nameserver *server_head;
315 	int n_req_heads;
316 
317 	struct event_base *event_base;
318 
319 	/* The number of good nameservers that we have */
320 	int global_good_nameservers;
321 
322 	/* inflight requests are contained in the req_head list */
323 	/* and are actually going out across the network */
324 	int global_requests_inflight;
325 	/* requests which aren't inflight are in the waiting list */
326 	/* and are counted here */
327 	int global_requests_waiting;
328 
329 	int global_max_requests_inflight;
330 
331 	struct timeval global_timeout;	/* 5 seconds by default */
332 	int global_max_reissues;  /* a reissue occurs when we get some errors from the server */
333 	int global_max_retransmits;  /* number of times we'll retransmit a request which timed out */
334 	/* number of timeouts in a row before we consider this server to be down */
335 	int global_max_nameserver_timeout;
336 	/* true iff we will use the 0x20 hack to prevent poisoning attacks. */
337 	int global_randomize_case;
338 
339 	/* The first time that a nameserver fails, how long do we wait before
340 	 * probing to see if it has returned?  */
341 	struct timeval global_nameserver_probe_initial_timeout;
342 
343 	/** Port to bind to for outgoing DNS packets. */
344 	struct sockaddr_storage global_outgoing_address;
345 	/** ev_socklen_t for global_outgoing_address. 0 if it isn't set. */
346 	ev_socklen_t global_outgoing_addrlen;
347 
348 	struct timeval global_getaddrinfo_allow_skew;
349 
350 	int so_rcvbuf;
351 	int so_sndbuf;
352 
353 	int getaddrinfo_ipv4_timeouts;
354 	int getaddrinfo_ipv6_timeouts;
355 	int getaddrinfo_ipv4_answered;
356 	int getaddrinfo_ipv6_answered;
357 
358 	struct search_state *global_search_state;
359 
360 	TAILQ_HEAD(hosts_list, hosts_entry) hostsdb;
361 
362 #ifndef EVENT__DISABLE_THREAD_SUPPORT
363 	void *lock;
364 #endif
365 
366 	int disable_when_inactive;
367 };
368 
369 struct hosts_entry {
370 	TAILQ_ENTRY(hosts_entry) next;
371 	union {
372 		struct sockaddr sa;
373 		struct sockaddr_in sin;
374 		struct sockaddr_in6 sin6;
375 	} addr;
376 	int addrlen;
377 	char hostname[1];
378 };
379 
380 static struct evdns_base *current_base = NULL;
381 
382 struct evdns_base *
383 evdns_get_global_base(void)
384 {
385 	return current_base;
386 }
387 
388 /* Given a pointer to an evdns_server_request, get the corresponding */
389 /* server_request. */
390 #define TO_SERVER_REQUEST(base_ptr)					\
391 	((struct server_request*)					\
392 	  (((char*)(base_ptr) - evutil_offsetof(struct server_request, base))))
393 
394 #define REQ_HEAD(base, id) ((base)->req_heads[id % (base)->n_req_heads])
395 
396 static struct nameserver *nameserver_pick(struct evdns_base *base);
397 static void evdns_request_insert(struct request *req, struct request **head);
398 static void evdns_request_remove(struct request *req, struct request **head);
399 static void nameserver_ready_callback(evutil_socket_t fd, short events, void *arg);
400 static int evdns_transmit(struct evdns_base *base);
401 static int evdns_request_transmit(struct request *req);
402 static void nameserver_send_probe(struct nameserver *const ns);
403 static void search_request_finished(struct evdns_request *const);
404 static int search_try_next(struct evdns_request *const req);
405 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);
406 static void evdns_requests_pump_waiting_queue(struct evdns_base *base);
407 static u16 transaction_id_pick(struct evdns_base *base);
408 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);
409 static void request_submit(struct request *const req);
410 
411 static int server_request_free(struct server_request *req);
412 static void server_request_free_answers(struct server_request *req);
413 static void server_port_free(struct evdns_server_port *port);
414 static void server_port_ready_callback(evutil_socket_t fd, short events, void *arg);
415 static int evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char *const filename);
416 static int evdns_base_set_option_impl(struct evdns_base *base,
417     const char *option, const char *val, int flags);
418 static void evdns_base_free_and_unlock(struct evdns_base *base, int fail_requests);
419 static void evdns_request_timeout_callback(evutil_socket_t fd, short events, void *arg);
420 
421 static int strtoint(const char *const str);
422 
423 #ifdef EVENT__DISABLE_THREAD_SUPPORT
424 #define EVDNS_LOCK(base)  EVUTIL_NIL_STMT_
425 #define EVDNS_UNLOCK(base) EVUTIL_NIL_STMT_
426 #define ASSERT_LOCKED(base) EVUTIL_NIL_STMT_
427 #else
428 #define EVDNS_LOCK(base)			\
429 	EVLOCK_LOCK((base)->lock, 0)
430 #define EVDNS_UNLOCK(base)			\
431 	EVLOCK_UNLOCK((base)->lock, 0)
432 #define ASSERT_LOCKED(base)			\
433 	EVLOCK_ASSERT_LOCKED((base)->lock)
434 #endif
435 
436 static evdns_debug_log_fn_type evdns_log_fn = NULL;
437 
438 void
439 evdns_set_log_fn(evdns_debug_log_fn_type fn)
440 {
441 	evdns_log_fn = fn;
442 }
443 
444 #ifdef __GNUC__
445 #define EVDNS_LOG_CHECK	 __attribute__ ((format(printf, 2, 3)))
446 #else
447 #define EVDNS_LOG_CHECK
448 #endif
449 
450 static void evdns_log_(int severity, const char *fmt, ...) EVDNS_LOG_CHECK;
451 static void
452 evdns_log_(int severity, const char *fmt, ...)
453 {
454 	va_list args;
455 	va_start(args,fmt);
456 	if (evdns_log_fn) {
457 		char buf[512];
458 		int is_warn = (severity == EVDNS_LOG_WARN);
459 		evutil_vsnprintf(buf, sizeof(buf), fmt, args);
460 		evdns_log_fn(is_warn, buf);
461 	} else {
462 		event_logv_(severity, NULL, fmt, args);
463 	}
464 	va_end(args);
465 }
466 
467 #define log evdns_log_
468 
469 /* This walks the list of inflight requests to find the */
470 /* one with a matching transaction id. Returns NULL on */
471 /* failure */
472 static struct request *
473 request_find_from_trans_id(struct evdns_base *base, u16 trans_id) {
474 	struct request *req = REQ_HEAD(base, trans_id);
475 	struct request *const started_at = req;
476 
477 	ASSERT_LOCKED(base);
478 
479 	if (req) {
480 		do {
481 			if (req->trans_id == trans_id) return req;
482 			req = req->next;
483 		} while (req != started_at);
484 	}
485 
486 	return NULL;
487 }
488 
489 /* a libevent callback function which is called when a nameserver */
490 /* has gone down and we want to test if it has came back to life yet */
491 static void
492 nameserver_prod_callback(evutil_socket_t fd, short events, void *arg) {
493 	struct nameserver *const ns = (struct nameserver *) arg;
494 	(void)fd;
495 	(void)events;
496 
497 	EVDNS_LOCK(ns->base);
498 	nameserver_send_probe(ns);
499 	EVDNS_UNLOCK(ns->base);
500 }
501 
502 /* a libevent callback which is called when a nameserver probe (to see if */
503 /* it has come back to life) times out. We increment the count of failed_times */
504 /* and wait longer to send the next probe packet. */
505 static void
506 nameserver_probe_failed(struct nameserver *const ns) {
507 	struct timeval timeout;
508 	int i;
509 
510 	ASSERT_LOCKED(ns->base);
511 	(void) evtimer_del(&ns->timeout_event);
512 	if (ns->state == 1) {
513 		/* This can happen if the nameserver acts in a way which makes us mark */
514 		/* it as bad and then starts sending good replies. */
515 		return;
516 	}
517 
518 #define MAX_PROBE_TIMEOUT 3600
519 #define TIMEOUT_BACKOFF_FACTOR 3
520 
521 	memcpy(&timeout, &ns->base->global_nameserver_probe_initial_timeout,
522 	    sizeof(struct timeval));
523 	for (i=ns->failed_times; i > 0 && timeout.tv_sec < MAX_PROBE_TIMEOUT; --i) {
524 		timeout.tv_sec *= TIMEOUT_BACKOFF_FACTOR;
525 		timeout.tv_usec *= TIMEOUT_BACKOFF_FACTOR;
526 		if (timeout.tv_usec > 1000000) {
527 			timeout.tv_sec += timeout.tv_usec / 1000000;
528 			timeout.tv_usec %= 1000000;
529 		}
530 	}
531 	if (timeout.tv_sec > MAX_PROBE_TIMEOUT) {
532 		timeout.tv_sec = MAX_PROBE_TIMEOUT;
533 		timeout.tv_usec = 0;
534 	}
535 
536 	ns->failed_times++;
537 
538 	if (evtimer_add(&ns->timeout_event, &timeout) < 0) {
539 		char addrbuf[128];
540 		log(EVDNS_LOG_WARN,
541 		    "Error from libevent when adding timer event for %s",
542 		    evutil_format_sockaddr_port_(
543 			    (struct sockaddr *)&ns->address,
544 			    addrbuf, sizeof(addrbuf)));
545 	}
546 }
547 
548 static void
549 request_swap_ns(struct request *req, struct nameserver *ns) {
550 	if (ns && req->ns != ns) {
551 		EVUTIL_ASSERT(req->ns->requests_inflight > 0);
552 		req->ns->requests_inflight--;
553 		ns->requests_inflight++;
554 
555 		req->ns = ns;
556 	}
557 }
558 
559 /* called when a nameserver has been deemed to have failed. For example, too */
560 /* many packets have timed out etc */
561 static void
562 nameserver_failed(struct nameserver *const ns, const char *msg) {
563 	struct request *req, *started_at;
564 	struct evdns_base *base = ns->base;
565 	int i;
566 	char addrbuf[128];
567 
568 	ASSERT_LOCKED(base);
569 	/* if this nameserver has already been marked as failed */
570 	/* then don't do anything */
571 	if (!ns->state) return;
572 
573 	log(EVDNS_LOG_MSG, "Nameserver %s has failed: %s",
574 	    evutil_format_sockaddr_port_(
575 		    (struct sockaddr *)&ns->address,
576 		    addrbuf, sizeof(addrbuf)),
577 	    msg);
578 
579 	base->global_good_nameservers--;
580 	EVUTIL_ASSERT(base->global_good_nameservers >= 0);
581 	if (base->global_good_nameservers == 0) {
582 		log(EVDNS_LOG_MSG, "All nameservers have failed");
583 	}
584 
585 	ns->state = 0;
586 	ns->failed_times = 1;
587 
588 	if (evtimer_add(&ns->timeout_event,
589 		&base->global_nameserver_probe_initial_timeout) < 0) {
590 		log(EVDNS_LOG_WARN,
591 		    "Error from libevent when adding timer event for %s",
592 		    evutil_format_sockaddr_port_(
593 			    (struct sockaddr *)&ns->address,
594 			    addrbuf, sizeof(addrbuf)));
595 		/* ???? Do more? */
596 	}
597 
598 	/* walk the list of inflight requests to see if any can be reassigned to */
599 	/* a different server. Requests in the waiting queue don't have a */
600 	/* nameserver assigned yet */
601 
602 	/* if we don't have *any* good nameservers then there's no point */
603 	/* trying to reassign requests to one */
604 	if (!base->global_good_nameservers) return;
605 
606 	for (i = 0; i < base->n_req_heads; ++i) {
607 		req = started_at = base->req_heads[i];
608 		if (req) {
609 			do {
610 				if (req->tx_count == 0 && req->ns == ns) {
611 					/* still waiting to go out, can be moved */
612 					/* to another server */
613 					request_swap_ns(req, nameserver_pick(base));
614 				}
615 				req = req->next;
616 			} while (req != started_at);
617 		}
618 	}
619 }
620 
621 static void
622 nameserver_up(struct nameserver *const ns)
623 {
624 	char addrbuf[128];
625 	ASSERT_LOCKED(ns->base);
626 	if (ns->state) return;
627 	log(EVDNS_LOG_MSG, "Nameserver %s is back up",
628 	    evutil_format_sockaddr_port_(
629 		    (struct sockaddr *)&ns->address,
630 		    addrbuf, sizeof(addrbuf)));
631 	evtimer_del(&ns->timeout_event);
632 	if (ns->probe_request) {
633 		evdns_cancel_request(ns->base, ns->probe_request);
634 		ns->probe_request = NULL;
635 	}
636 	ns->state = 1;
637 	ns->failed_times = 0;
638 	ns->timedout = 0;
639 	ns->base->global_good_nameservers++;
640 }
641 
642 static void
643 request_trans_id_set(struct request *const req, const u16 trans_id) {
644 	req->trans_id = trans_id;
645 	*((u16 *) req->request) = htons(trans_id);
646 }
647 
648 /* Called to remove a request from a list and dealloc it. */
649 /* head is a pointer to the head of the list it should be */
650 /* removed from or NULL if the request isn't in a list. */
651 /* when free_handle is one, free the handle as well. */
652 static void
653 request_finished(struct request *const req, struct request **head, int free_handle) {
654 	struct evdns_base *base = req->base;
655 	int was_inflight = (head != &base->req_waiting_head);
656 	EVDNS_LOCK(base);
657 	ASSERT_VALID_REQUEST(req);
658 
659 	if (head)
660 		evdns_request_remove(req, head);
661 
662 	log(EVDNS_LOG_DEBUG, "Removing timeout for request %p", req);
663 	if (was_inflight) {
664 		evtimer_del(&req->timeout_event);
665 		base->global_requests_inflight--;
666 		req->ns->requests_inflight--;
667 	} else {
668 		base->global_requests_waiting--;
669 	}
670 	/* it was initialized during request_new / evtimer_assign */
671 	event_debug_unassign(&req->timeout_event);
672 
673 	if (req->ns &&
674 	    req->ns->requests_inflight == 0 &&
675 	    req->base->disable_when_inactive) {
676 		event_del(&req->ns->event);
677 		evtimer_del(&req->ns->timeout_event);
678 	}
679 
680 	if (!req->request_appended) {
681 		/* need to free the request data on it's own */
682 		mm_free(req->request);
683 	} else {
684 		/* the request data is appended onto the header */
685 		/* so everything gets free()ed when we: */
686 	}
687 
688 	if (req->handle) {
689 		EVUTIL_ASSERT(req->handle->current_req == req);
690 
691 		if (free_handle) {
692 			search_request_finished(req->handle);
693 			req->handle->current_req = NULL;
694 			if (! req->handle->pending_cb) {
695 				/* If we're planning to run the callback,
696 				 * don't free the handle until later. */
697 				mm_free(req->handle);
698 			}
699 			req->handle = NULL; /* If we have a bug, let's crash
700 					     * early */
701 		} else {
702 			req->handle->current_req = NULL;
703 		}
704 	}
705 
706 	mm_free(req);
707 
708 	evdns_requests_pump_waiting_queue(base);
709 	EVDNS_UNLOCK(base);
710 }
711 
712 /* This is called when a server returns a funny error code. */
713 /* We try the request again with another server. */
714 /* */
715 /* return: */
716 /*   0 ok */
717 /*   1 failed/reissue is pointless */
718 static int
719 request_reissue(struct request *req) {
720 	const struct nameserver *const last_ns = req->ns;
721 	ASSERT_LOCKED(req->base);
722 	ASSERT_VALID_REQUEST(req);
723 	/* the last nameserver should have been marked as failing */
724 	/* by the caller of this function, therefore pick will try */
725 	/* not to return it */
726 	request_swap_ns(req, nameserver_pick(req->base));
727 	if (req->ns == last_ns) {
728 		/* ... but pick did return it */
729 		/* not a lot of point in trying again with the */
730 		/* same server */
731 		return 1;
732 	}
733 
734 	req->reissue_count++;
735 	req->tx_count = 0;
736 	req->transmit_me = 1;
737 
738 	return 0;
739 }
740 
741 /* this function looks for space on the inflight queue and promotes */
742 /* requests from the waiting queue if it can. */
743 /* */
744 /* TODO: */
745 /* add return code, see at nameserver_pick() and other functions. */
746 static void
747 evdns_requests_pump_waiting_queue(struct evdns_base *base) {
748 	ASSERT_LOCKED(base);
749 	while (base->global_requests_inflight < base->global_max_requests_inflight &&
750 		   base->global_requests_waiting) {
751 		struct request *req;
752 
753 		EVUTIL_ASSERT(base->req_waiting_head);
754 		req = base->req_waiting_head;
755 
756 		req->ns = nameserver_pick(base);
757 		if (!req->ns)
758 			return;
759 
760 		/* move a request from the waiting queue to the inflight queue */
761 		req->ns->requests_inflight++;
762 
763 		evdns_request_remove(req, &base->req_waiting_head);
764 
765 		base->global_requests_waiting--;
766 		base->global_requests_inflight++;
767 
768 		request_trans_id_set(req, transaction_id_pick(base));
769 
770 		evdns_request_insert(req, &REQ_HEAD(base, req->trans_id));
771 		evdns_request_transmit(req);
772 		evdns_transmit(base);
773 	}
774 }
775 
776 /* TODO(nickm) document */
777 struct deferred_reply_callback {
778 	struct event_callback deferred;
779 	struct evdns_request *handle;
780 	u8 request_type;
781 	u8 have_reply;
782 	u32 ttl;
783 	u32 err;
784 	evdns_callback_type user_callback;
785 	struct reply reply;
786 };
787 
788 static void
789 reply_run_callback(struct event_callback *d, void *user_pointer)
790 {
791 	struct deferred_reply_callback *cb =
792 	    EVUTIL_UPCAST(d, struct deferred_reply_callback, deferred);
793 
794 	switch (cb->request_type) {
795 	case TYPE_A:
796 		if (cb->have_reply)
797 			cb->user_callback(DNS_ERR_NONE, DNS_IPv4_A,
798 			    cb->reply.data.a.addrcount, cb->ttl,
799 			    cb->reply.data.a.addresses,
800 			    user_pointer);
801 		else
802 			cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer);
803 		break;
804 	case TYPE_PTR:
805 		if (cb->have_reply) {
806 			char *name = cb->reply.data.ptr.name;
807 			cb->user_callback(DNS_ERR_NONE, DNS_PTR, 1, cb->ttl,
808 			    &name, user_pointer);
809 		} else {
810 			cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer);
811 		}
812 		break;
813 	case TYPE_AAAA:
814 		if (cb->have_reply)
815 			cb->user_callback(DNS_ERR_NONE, DNS_IPv6_AAAA,
816 			    cb->reply.data.aaaa.addrcount, cb->ttl,
817 			    cb->reply.data.aaaa.addresses,
818 			    user_pointer);
819 		else
820 			cb->user_callback(cb->err, 0, 0, cb->ttl, NULL, user_pointer);
821 		break;
822 	default:
823 		EVUTIL_ASSERT(0);
824 	}
825 
826 	if (cb->handle && cb->handle->pending_cb) {
827 		mm_free(cb->handle);
828 	}
829 
830 	mm_free(cb);
831 }
832 
833 static void
834 reply_schedule_callback(struct request *const req, u32 ttl, u32 err, struct reply *reply)
835 {
836 	struct deferred_reply_callback *d = mm_calloc(1, sizeof(*d));
837 
838 	if (!d) {
839 		event_warn("%s: Couldn't allocate space for deferred callback.",
840 		    __func__);
841 		return;
842 	}
843 
844 	ASSERT_LOCKED(req->base);
845 
846 	d->request_type = req->request_type;
847 	d->user_callback = req->user_callback;
848 	d->ttl = ttl;
849 	d->err = err;
850 	if (reply) {
851 		d->have_reply = 1;
852 		memcpy(&d->reply, reply, sizeof(struct reply));
853 	}
854 
855 	if (req->handle) {
856 		req->handle->pending_cb = 1;
857 		d->handle = req->handle;
858 	}
859 
860 	event_deferred_cb_init_(
861 	    &d->deferred,
862 	    event_get_priority(&req->timeout_event),
863 	    reply_run_callback,
864 	    req->user_pointer);
865 	event_deferred_cb_schedule_(
866 		req->base->event_base,
867 		&d->deferred);
868 }
869 
870 
871 #define _QR_MASK    0x8000U
872 #define _OP_MASK    0x7800U
873 #define _AA_MASK    0x0400U
874 #define _TC_MASK    0x0200U
875 #define _RD_MASK    0x0100U
876 #define _RA_MASK    0x0080U
877 #define _Z_MASK     0x0040U
878 #define _AD_MASK    0x0020U
879 #define _CD_MASK    0x0010U
880 #define _RCODE_MASK 0x000fU
881 #define _Z_MASK_DEPRECATED 0x0070U
882 
883 /* this processes a parsed reply packet */
884 static void
885 reply_handle(struct request *const req, u16 flags, u32 ttl, struct reply *reply) {
886 	int error;
887 	char addrbuf[128];
888 	static const int error_codes[] = {
889 		DNS_ERR_FORMAT, DNS_ERR_SERVERFAILED, DNS_ERR_NOTEXIST,
890 		DNS_ERR_NOTIMPL, DNS_ERR_REFUSED
891 	};
892 
893 	ASSERT_LOCKED(req->base);
894 	ASSERT_VALID_REQUEST(req);
895 
896 	if (flags & (_RCODE_MASK | _TC_MASK) || !reply || !reply->have_answer) {
897 		/* there was an error */
898 		if (flags & _TC_MASK) {
899 			error = DNS_ERR_TRUNCATED;
900 		} else if (flags & _RCODE_MASK) {
901 			u16 error_code = (flags & _RCODE_MASK) - 1;
902 			if (error_code > 4) {
903 				error = DNS_ERR_UNKNOWN;
904 			} else {
905 				error = error_codes[error_code];
906 			}
907 		} else if (reply && !reply->have_answer) {
908 			error = DNS_ERR_NODATA;
909 		} else {
910 			error = DNS_ERR_UNKNOWN;
911 		}
912 
913 		switch (error) {
914 		case DNS_ERR_NOTIMPL:
915 		case DNS_ERR_REFUSED:
916 			/* we regard these errors as marking a bad nameserver */
917 			if (req->reissue_count < req->base->global_max_reissues) {
918 				char msg[64];
919 				evutil_snprintf(msg, sizeof(msg), "Bad response %d (%s)",
920 					 error, evdns_err_to_string(error));
921 				nameserver_failed(req->ns, msg);
922 				if (!request_reissue(req)) return;
923 			}
924 			break;
925 		case DNS_ERR_SERVERFAILED:
926 			/* rcode 2 (servfailed) sometimes means "we
927 			 * are broken" and sometimes (with some binds)
928 			 * means "that request was very confusing."
929 			 * Treat this as a timeout, not a failure.
930 			 */
931 			log(EVDNS_LOG_DEBUG, "Got a SERVERFAILED from nameserver"
932 				"at %s; will allow the request to time out.",
933 			    evutil_format_sockaddr_port_(
934 				    (struct sockaddr *)&req->ns->address,
935 				    addrbuf, sizeof(addrbuf)));
936 			/* Call the timeout function */
937 			evdns_request_timeout_callback(0, 0, req);
938 			return;
939 		default:
940 			/* we got a good reply from the nameserver: it is up. */
941 			if (req->handle == req->ns->probe_request) {
942 				/* Avoid double-free */
943 				req->ns->probe_request = NULL;
944 			}
945 
946 			nameserver_up(req->ns);
947 		}
948 
949 		if (req->handle->search_state &&
950 		    req->request_type != TYPE_PTR) {
951 			/* if we have a list of domains to search in,
952 			 * try the next one */
953 			if (!search_try_next(req->handle)) {
954 				/* a new request was issued so this
955 				 * request is finished and */
956 				/* the user callback will be made when
957 				 * that request (or a */
958 				/* child of it) finishes. */
959 				return;
960 			}
961 		}
962 
963 		/* all else failed. Pass the failure up */
964 		reply_schedule_callback(req, ttl, error, NULL);
965 		request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1);
966 	} else {
967 		/* all ok, tell the user */
968 		reply_schedule_callback(req, ttl, 0, reply);
969 		if (req->handle == req->ns->probe_request)
970 			req->ns->probe_request = NULL; /* Avoid double-free */
971 		nameserver_up(req->ns);
972 		request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1);
973 	}
974 }
975 
976 static int
977 name_parse(u8 *packet, int length, int *idx, char *name_out, int name_out_len) {
978 	int name_end = -1;
979 	int j = *idx;
980 	int ptr_count = 0;
981 #define GET32(x) do { if (j + 4 > length) goto err; memcpy(&t32_, packet + j, 4); j += 4; x = ntohl(t32_); } while (0)
982 #define GET16(x) do { if (j + 2 > length) goto err; memcpy(&t_, packet + j, 2); j += 2; x = ntohs(t_); } while (0)
983 #define GET8(x) do { if (j >= length) goto err; x = packet[j++]; } while (0)
984 
985 	char *cp = name_out;
986 	const char *const end = name_out + name_out_len;
987 
988 	/* Normally, names are a series of length prefixed strings terminated */
989 	/* with a length of 0 (the lengths are u8's < 63). */
990 	/* However, the length can start with a pair of 1 bits and that */
991 	/* means that the next 14 bits are a pointer within the current */
992 	/* packet. */
993 
994 	for (;;) {
995 		u8 label_len;
996 		GET8(label_len);
997 		if (!label_len) break;
998 		if (label_len & 0xc0) {
999 			u8 ptr_low;
1000 			GET8(ptr_low);
1001 			if (name_end < 0) name_end = j;
1002 			j = (((int)label_len & 0x3f) << 8) + ptr_low;
1003 			/* Make sure that the target offset is in-bounds. */
1004 			if (j < 0 || j >= length) return -1;
1005 			/* If we've jumped more times than there are characters in the
1006 			 * message, we must have a loop. */
1007 			if (++ptr_count > length) return -1;
1008 			continue;
1009 		}
1010 		if (label_len > 63) return -1;
1011 		if (cp != name_out) {
1012 			if (cp + 1 >= end) return -1;
1013 			*cp++ = '.';
1014 		}
1015 		if (cp + label_len >= end) return -1;
1016 		if (j + label_len > length) return -1;
1017 		memcpy(cp, packet + j, label_len);
1018 		cp += label_len;
1019 		j += label_len;
1020 	}
1021 	if (cp >= end) return -1;
1022 	*cp = '\0';
1023 	if (name_end < 0)
1024 		*idx = j;
1025 	else
1026 		*idx = name_end;
1027 	return 0;
1028  err:
1029 	return -1;
1030 }
1031 
1032 /* parses a raw request from a nameserver */
1033 static int
1034 reply_parse(struct evdns_base *base, u8 *packet, int length) {
1035 	int j = 0, k = 0;  /* index into packet */
1036 	u16 t_;	 /* used by the macros */
1037 	u32 t32_;  /* used by the macros */
1038 	char tmp_name[256], cmp_name[256]; /* used by the macros */
1039 	int name_matches = 0;
1040 
1041 	u16 trans_id, questions, answers, authority, additional, datalength;
1042 	u16 flags = 0;
1043 	u32 ttl, ttl_r = 0xffffffff;
1044 	struct reply reply;
1045 	struct request *req = NULL;
1046 	unsigned int i;
1047 
1048 	ASSERT_LOCKED(base);
1049 
1050 	GET16(trans_id);
1051 	GET16(flags);
1052 	GET16(questions);
1053 	GET16(answers);
1054 	GET16(authority);
1055 	GET16(additional);
1056 	(void) authority; /* suppress "unused variable" warnings. */
1057 	(void) additional; /* suppress "unused variable" warnings. */
1058 
1059 	req = request_find_from_trans_id(base, trans_id);
1060 	if (!req) return -1;
1061 	EVUTIL_ASSERT(req->base == base);
1062 
1063 	memset(&reply, 0, sizeof(reply));
1064 
1065 	/* If it's not an answer, it doesn't correspond to any request. */
1066 	if (!(flags & _QR_MASK)) return -1;  /* must be an answer */
1067 	if ((flags & (_RCODE_MASK|_TC_MASK)) && (flags & (_RCODE_MASK|_TC_MASK)) != DNS_ERR_NOTEXIST) {
1068 		/* there was an error and it's not NXDOMAIN */
1069 		goto err;
1070 	}
1071 	/* if (!answers) return; */  /* must have an answer of some form */
1072 
1073 	/* This macro skips a name in the DNS reply. */
1074 #define SKIP_NAME						\
1075 	do { tmp_name[0] = '\0';				\
1076 		if (name_parse(packet, length, &j, tmp_name,	\
1077 			sizeof(tmp_name))<0)			\
1078 			goto err;				\
1079 	} while (0)
1080 
1081 	reply.type = req->request_type;
1082 
1083 	/* skip over each question in the reply */
1084 	for (i = 0; i < questions; ++i) {
1085 		/* the question looks like
1086 		 *   <label:name><u16:type><u16:class>
1087 		 */
1088 		tmp_name[0] = '\0';
1089 		cmp_name[0] = '\0';
1090 		k = j;
1091 		if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name)) < 0)
1092 			goto err;
1093 		if (name_parse(req->request, req->request_len, &k,
1094 			cmp_name, sizeof(cmp_name))<0)
1095 			goto err;
1096 		if (!base->global_randomize_case) {
1097 			if (strcmp(tmp_name, cmp_name) == 0)
1098 				name_matches = 1;
1099 		} else {
1100 			if (evutil_ascii_strcasecmp(tmp_name, cmp_name) == 0)
1101 				name_matches = 1;
1102 		}
1103 
1104 		j += 4;
1105 		if (j > length)
1106 			goto err;
1107 	}
1108 
1109 	if (!name_matches)
1110 		goto err;
1111 
1112 	/* now we have the answer section which looks like
1113 	 * <label:name><u16:type><u16:class><u32:ttl><u16:len><data...>
1114 	 */
1115 
1116 	for (i = 0; i < answers; ++i) {
1117 		u16 type, class;
1118 
1119 		SKIP_NAME;
1120 		GET16(type);
1121 		GET16(class);
1122 		GET32(ttl);
1123 		GET16(datalength);
1124 
1125 		if (type == TYPE_A && class == CLASS_INET) {
1126 			int addrcount, addrtocopy;
1127 			if (req->request_type != TYPE_A) {
1128 				j += datalength; continue;
1129 			}
1130 			if ((datalength & 3) != 0) /* not an even number of As. */
1131 			    goto err;
1132 			addrcount = datalength >> 2;
1133 			addrtocopy = MIN(MAX_V4_ADDRS - reply.data.a.addrcount, (unsigned)addrcount);
1134 
1135 			ttl_r = MIN(ttl_r, ttl);
1136 			/* we only bother with the first four addresses. */
1137 			if (j + 4*addrtocopy > length) goto err;
1138 			memcpy(&reply.data.a.addresses[reply.data.a.addrcount],
1139 				   packet + j, 4*addrtocopy);
1140 			j += 4*addrtocopy;
1141 			reply.data.a.addrcount += addrtocopy;
1142 			reply.have_answer = 1;
1143 			if (reply.data.a.addrcount == MAX_V4_ADDRS) break;
1144 		} else if (type == TYPE_PTR && class == CLASS_INET) {
1145 			if (req->request_type != TYPE_PTR) {
1146 				j += datalength; continue;
1147 			}
1148 			if (name_parse(packet, length, &j, reply.data.ptr.name,
1149 						   sizeof(reply.data.ptr.name))<0)
1150 				goto err;
1151 			ttl_r = MIN(ttl_r, ttl);
1152 			reply.have_answer = 1;
1153 			break;
1154 		} else if (type == TYPE_CNAME) {
1155 			char cname[HOST_NAME_MAX];
1156 			if (!req->put_cname_in_ptr || *req->put_cname_in_ptr) {
1157 				j += datalength; continue;
1158 			}
1159 			if (name_parse(packet, length, &j, cname,
1160 				sizeof(cname))<0)
1161 				goto err;
1162 			*req->put_cname_in_ptr = mm_strdup(cname);
1163 		} else if (type == TYPE_AAAA && class == CLASS_INET) {
1164 			int addrcount, addrtocopy;
1165 			if (req->request_type != TYPE_AAAA) {
1166 				j += datalength; continue;
1167 			}
1168 			if ((datalength & 15) != 0) /* not an even number of AAAAs. */
1169 				goto err;
1170 			addrcount = datalength >> 4;  /* each address is 16 bytes long */
1171 			addrtocopy = MIN(MAX_V6_ADDRS - reply.data.aaaa.addrcount, (unsigned)addrcount);
1172 			ttl_r = MIN(ttl_r, ttl);
1173 
1174 			/* we only bother with the first four addresses. */
1175 			if (j + 16*addrtocopy > length) goto err;
1176 			memcpy(&reply.data.aaaa.addresses[reply.data.aaaa.addrcount],
1177 				   packet + j, 16*addrtocopy);
1178 			reply.data.aaaa.addrcount += addrtocopy;
1179 			j += 16*addrtocopy;
1180 			reply.have_answer = 1;
1181 			if (reply.data.aaaa.addrcount == MAX_V6_ADDRS) break;
1182 		} else {
1183 			/* skip over any other type of resource */
1184 			j += datalength;
1185 		}
1186 	}
1187 
1188 	if (!reply.have_answer) {
1189 		for (i = 0; i < authority; ++i) {
1190 			u16 type, class;
1191 			SKIP_NAME;
1192 			GET16(type);
1193 			GET16(class);
1194 			GET32(ttl);
1195 			GET16(datalength);
1196 			if (type == TYPE_SOA && class == CLASS_INET) {
1197 				u32 serial, refresh, retry, expire, minimum;
1198 				SKIP_NAME;
1199 				SKIP_NAME;
1200 				GET32(serial);
1201 				GET32(refresh);
1202 				GET32(retry);
1203 				GET32(expire);
1204 				GET32(minimum);
1205 				(void)expire;
1206 				(void)retry;
1207 				(void)refresh;
1208 				(void)serial;
1209 				ttl_r = MIN(ttl_r, ttl);
1210 				ttl_r = MIN(ttl_r, minimum);
1211 			} else {
1212 				/* skip over any other type of resource */
1213 				j += datalength;
1214 			}
1215 		}
1216 	}
1217 
1218 	if (ttl_r == 0xffffffff)
1219 		ttl_r = 0;
1220 
1221 	reply_handle(req, flags, ttl_r, &reply);
1222 	return 0;
1223  err:
1224 	if (req)
1225 		reply_handle(req, flags, 0, NULL);
1226 	return -1;
1227 }
1228 
1229 /* Parse a raw request (packet,length) sent to a nameserver port (port) from */
1230 /* a DNS client (addr,addrlen), and if it's well-formed, call the corresponding */
1231 /* callback. */
1232 static int
1233 request_parse(u8 *packet, int length, struct evdns_server_port *port, struct sockaddr *addr, ev_socklen_t addrlen)
1234 {
1235 	int j = 0;	/* index into packet */
1236 	u16 t_;	 /* used by the macros */
1237 	char tmp_name[256]; /* used by the macros */
1238 
1239 	int i;
1240 	u16 trans_id, flags, questions, answers, authority, additional;
1241 	struct server_request *server_req = NULL;
1242 
1243 	ASSERT_LOCKED(port);
1244 
1245 	/* Get the header fields */
1246 	GET16(trans_id);
1247 	GET16(flags);
1248 	GET16(questions);
1249 	GET16(answers);
1250 	GET16(authority);
1251 	GET16(additional);
1252 	(void)answers;
1253 	(void)additional;
1254 	(void)authority;
1255 
1256 	if (flags & _QR_MASK) return -1; /* Must not be an answer. */
1257 	flags &= (_RD_MASK|_CD_MASK); /* Only RD and CD get preserved. */
1258 
1259 	server_req = mm_malloc(sizeof(struct server_request));
1260 	if (server_req == NULL) return -1;
1261 	memset(server_req, 0, sizeof(struct server_request));
1262 
1263 	server_req->trans_id = trans_id;
1264 	memcpy(&server_req->addr, addr, addrlen);
1265 	server_req->addrlen = addrlen;
1266 
1267 	server_req->base.flags = flags;
1268 	server_req->base.nquestions = 0;
1269 	server_req->base.questions = mm_calloc(sizeof(struct evdns_server_question *), questions);
1270 	if (server_req->base.questions == NULL)
1271 		goto err;
1272 
1273 	for (i = 0; i < questions; ++i) {
1274 		u16 type, class;
1275 		struct evdns_server_question *q;
1276 		int namelen;
1277 		if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name))<0)
1278 			goto err;
1279 		GET16(type);
1280 		GET16(class);
1281 		namelen = (int)strlen(tmp_name);
1282 		q = mm_malloc(sizeof(struct evdns_server_question) + namelen);
1283 		if (!q)
1284 			goto err;
1285 		q->type = type;
1286 		q->dns_question_class = class;
1287 		memcpy(q->name, tmp_name, namelen+1);
1288 		server_req->base.questions[server_req->base.nquestions++] = q;
1289 	}
1290 
1291 	/* Ignore answers, authority, and additional. */
1292 
1293 	server_req->port = port;
1294 	port->refcnt++;
1295 
1296 	/* Only standard queries are supported. */
1297 	if (flags & _OP_MASK) {
1298 		evdns_server_request_respond(&(server_req->base), DNS_ERR_NOTIMPL);
1299 		return -1;
1300 	}
1301 
1302 	port->user_callback(&(server_req->base), port->user_data);
1303 
1304 	return 0;
1305 err:
1306 	if (server_req->base.questions) {
1307 		for (i = 0; i < server_req->base.nquestions; ++i)
1308 			mm_free(server_req->base.questions[i]);
1309 		mm_free(server_req->base.questions);
1310 	}
1311 	mm_free(server_req);
1312 	return -1;
1313 
1314 #undef SKIP_NAME
1315 #undef GET32
1316 #undef GET16
1317 #undef GET8
1318 }
1319 
1320 
1321 void
1322 evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void))
1323 {
1324 }
1325 
1326 void
1327 evdns_set_random_bytes_fn(void (*fn)(char *, size_t))
1328 {
1329 }
1330 
1331 /* Try to choose a strong transaction id which isn't already in flight */
1332 static u16
1333 transaction_id_pick(struct evdns_base *base) {
1334 	ASSERT_LOCKED(base);
1335 	for (;;) {
1336 		u16 trans_id;
1337 		evutil_secure_rng_get_bytes(&trans_id, sizeof(trans_id));
1338 
1339 		if (trans_id == 0xffff) continue;
1340 		/* now check to see if that id is already inflight */
1341 		if (request_find_from_trans_id(base, trans_id) == NULL)
1342 			return trans_id;
1343 	}
1344 }
1345 
1346 /* choose a namesever to use. This function will try to ignore */
1347 /* nameservers which we think are down and load balance across the rest */
1348 /* by updating the server_head global each time. */
1349 static struct nameserver *
1350 nameserver_pick(struct evdns_base *base) {
1351 	struct nameserver *started_at = base->server_head, *picked;
1352 	ASSERT_LOCKED(base);
1353 	if (!base->server_head) return NULL;
1354 
1355 	/* if we don't have any good nameservers then there's no */
1356 	/* point in trying to find one. */
1357 	if (!base->global_good_nameservers) {
1358 		base->server_head = base->server_head->next;
1359 		return base->server_head;
1360 	}
1361 
1362 	/* remember that nameservers are in a circular list */
1363 	for (;;) {
1364 		if (base->server_head->state) {
1365 			/* we think this server is currently good */
1366 			picked = base->server_head;
1367 			base->server_head = base->server_head->next;
1368 			return picked;
1369 		}
1370 
1371 		base->server_head = base->server_head->next;
1372 		if (base->server_head == started_at) {
1373 			/* all the nameservers seem to be down */
1374 			/* so we just return this one and hope for the */
1375 			/* best */
1376 			EVUTIL_ASSERT(base->global_good_nameservers == 0);
1377 			picked = base->server_head;
1378 			base->server_head = base->server_head->next;
1379 			return picked;
1380 		}
1381 	}
1382 }
1383 
1384 /* this is called when a namesever socket is ready for reading */
1385 static void
1386 nameserver_read(struct nameserver *ns) {
1387 	struct sockaddr_storage ss;
1388 	ev_socklen_t addrlen = sizeof(ss);
1389 	u8 packet[1500];
1390 	char addrbuf[128];
1391 	ASSERT_LOCKED(ns->base);
1392 
1393 	for (;;) {
1394 		const int r = recvfrom(ns->socket, (void*)packet,
1395 		    sizeof(packet), 0,
1396 		    (struct sockaddr*)&ss, &addrlen);
1397 		if (r < 0) {
1398 			int err = evutil_socket_geterror(ns->socket);
1399 			if (EVUTIL_ERR_RW_RETRIABLE(err))
1400 				return;
1401 			nameserver_failed(ns,
1402 			    evutil_socket_error_to_string(err));
1403 			return;
1404 		}
1405 		if (evutil_sockaddr_cmp((struct sockaddr*)&ss,
1406 			(struct sockaddr*)&ns->address, 0)) {
1407 			log(EVDNS_LOG_WARN, "Address mismatch on received "
1408 			    "DNS packet.  Apparent source was %s",
1409 			    evutil_format_sockaddr_port_(
1410 				    (struct sockaddr *)&ss,
1411 				    addrbuf, sizeof(addrbuf)));
1412 			return;
1413 		}
1414 
1415 		ns->timedout = 0;
1416 		reply_parse(ns->base, packet, r);
1417 	}
1418 }
1419 
1420 /* Read a packet from a DNS client on a server port s, parse it, and */
1421 /* act accordingly. */
1422 static void
1423 server_port_read(struct evdns_server_port *s) {
1424 	u8 packet[1500];
1425 	struct sockaddr_storage addr;
1426 	ev_socklen_t addrlen;
1427 	int r;
1428 	ASSERT_LOCKED(s);
1429 
1430 	for (;;) {
1431 		addrlen = sizeof(struct sockaddr_storage);
1432 		r = recvfrom(s->socket, (void*)packet, sizeof(packet), 0,
1433 					 (struct sockaddr*) &addr, &addrlen);
1434 		if (r < 0) {
1435 			int err = evutil_socket_geterror(s->socket);
1436 			if (EVUTIL_ERR_RW_RETRIABLE(err))
1437 				return;
1438 			log(EVDNS_LOG_WARN,
1439 			    "Error %s (%d) while reading request.",
1440 			    evutil_socket_error_to_string(err), err);
1441 			return;
1442 		}
1443 		request_parse(packet, r, s, (struct sockaddr*) &addr, addrlen);
1444 	}
1445 }
1446 
1447 /* Try to write all pending replies on a given DNS server port. */
1448 static void
1449 server_port_flush(struct evdns_server_port *port)
1450 {
1451 	struct server_request *req = port->pending_replies;
1452 	ASSERT_LOCKED(port);
1453 	while (req) {
1454 		int r = sendto(port->socket, req->response, (int)req->response_len, 0,
1455 			   (struct sockaddr*) &req->addr, (ev_socklen_t)req->addrlen);
1456 		if (r < 0) {
1457 			int err = evutil_socket_geterror(port->socket);
1458 			if (EVUTIL_ERR_RW_RETRIABLE(err))
1459 				return;
1460 			log(EVDNS_LOG_WARN, "Error %s (%d) while writing response to port; dropping", evutil_socket_error_to_string(err), err);
1461 		}
1462 		if (server_request_free(req)) {
1463 			/* we released the last reference to req->port. */
1464 			return;
1465 		} else {
1466 			EVUTIL_ASSERT(req != port->pending_replies);
1467 			req = port->pending_replies;
1468 		}
1469 	}
1470 
1471 	/* We have no more pending requests; stop listening for 'writeable' events. */
1472 	(void) event_del(&port->event);
1473 	event_assign(&port->event, port->event_base,
1474 				 port->socket, EV_READ | EV_PERSIST,
1475 				 server_port_ready_callback, port);
1476 
1477 	if (event_add(&port->event, NULL) < 0) {
1478 		log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server.");
1479 		/* ???? Do more? */
1480 	}
1481 }
1482 
1483 /* set if we are waiting for the ability to write to this server. */
1484 /* if waiting is true then we ask libevent for EV_WRITE events, otherwise */
1485 /* we stop these events. */
1486 static void
1487 nameserver_write_waiting(struct nameserver *ns, char waiting) {
1488 	ASSERT_LOCKED(ns->base);
1489 	if (ns->write_waiting == waiting) return;
1490 
1491 	ns->write_waiting = waiting;
1492 	(void) event_del(&ns->event);
1493 	event_assign(&ns->event, ns->base->event_base,
1494 	    ns->socket, EV_READ | (waiting ? EV_WRITE : 0) | EV_PERSIST,
1495 	    nameserver_ready_callback, ns);
1496 	if (event_add(&ns->event, NULL) < 0) {
1497 		char addrbuf[128];
1498 		log(EVDNS_LOG_WARN, "Error from libevent when adding event for %s",
1499 		    evutil_format_sockaddr_port_(
1500 			    (struct sockaddr *)&ns->address,
1501 			    addrbuf, sizeof(addrbuf)));
1502 		/* ???? Do more? */
1503 	}
1504 }
1505 
1506 /* a callback function. Called by libevent when the kernel says that */
1507 /* a nameserver socket is ready for writing or reading */
1508 static void
1509 nameserver_ready_callback(evutil_socket_t fd, short events, void *arg) {
1510 	struct nameserver *ns = (struct nameserver *) arg;
1511 	(void)fd;
1512 
1513 	EVDNS_LOCK(ns->base);
1514 	if (events & EV_WRITE) {
1515 		ns->choked = 0;
1516 		if (!evdns_transmit(ns->base)) {
1517 			nameserver_write_waiting(ns, 0);
1518 		}
1519 	}
1520 	if (events & EV_READ) {
1521 		nameserver_read(ns);
1522 	}
1523 	EVDNS_UNLOCK(ns->base);
1524 }
1525 
1526 /* a callback function. Called by libevent when the kernel says that */
1527 /* a server socket is ready for writing or reading. */
1528 static void
1529 server_port_ready_callback(evutil_socket_t fd, short events, void *arg) {
1530 	struct evdns_server_port *port = (struct evdns_server_port *) arg;
1531 	(void) fd;
1532 
1533 	EVDNS_LOCK(port);
1534 	if (events & EV_WRITE) {
1535 		port->choked = 0;
1536 		server_port_flush(port);
1537 	}
1538 	if (events & EV_READ) {
1539 		server_port_read(port);
1540 	}
1541 	EVDNS_UNLOCK(port);
1542 }
1543 
1544 /* This is an inefficient representation; only use it via the dnslabel_table_*
1545  * functions, so that is can be safely replaced with something smarter later. */
1546 #define MAX_LABELS 128
1547 /* Structures used to implement name compression */
1548 struct dnslabel_entry { char *v; off_t pos; };
1549 struct dnslabel_table {
1550 	int n_labels; /* number of current entries */
1551 	/* map from name to position in message */
1552 	struct dnslabel_entry labels[MAX_LABELS];
1553 };
1554 
1555 /* Initialize dnslabel_table. */
1556 static void
1557 dnslabel_table_init(struct dnslabel_table *table)
1558 {
1559 	table->n_labels = 0;
1560 }
1561 
1562 /* Free all storage held by table, but not the table itself. */
1563 static void
1564 dnslabel_clear(struct dnslabel_table *table)
1565 {
1566 	int i;
1567 	for (i = 0; i < table->n_labels; ++i)
1568 		mm_free(table->labels[i].v);
1569 	table->n_labels = 0;
1570 }
1571 
1572 /* return the position of the label in the current message, or -1 if the label */
1573 /* hasn't been used yet. */
1574 static int
1575 dnslabel_table_get_pos(const struct dnslabel_table *table, const char *label)
1576 {
1577 	int i;
1578 	for (i = 0; i < table->n_labels; ++i) {
1579 		if (!strcmp(label, table->labels[i].v))
1580 			return table->labels[i].pos;
1581 	}
1582 	return -1;
1583 }
1584 
1585 /* remember that we've used the label at position pos */
1586 static int
1587 dnslabel_table_add(struct dnslabel_table *table, const char *label, off_t pos)
1588 {
1589 	char *v;
1590 	int p;
1591 	if (table->n_labels == MAX_LABELS)
1592 		return (-1);
1593 	v = mm_strdup(label);
1594 	if (v == NULL)
1595 		return (-1);
1596 	p = table->n_labels++;
1597 	table->labels[p].v = v;
1598 	table->labels[p].pos = pos;
1599 
1600 	return (0);
1601 }
1602 
1603 /* Converts a string to a length-prefixed set of DNS labels, starting */
1604 /* at buf[j]. name and buf must not overlap. name_len should be the length */
1605 /* of name.	 table is optional, and is used for compression. */
1606 /* */
1607 /* Input: abc.def */
1608 /* Output: <3>abc<3>def<0> */
1609 /* */
1610 /* Returns the first index after the encoded name, or negative on error. */
1611 /*	 -1	 label was > 63 bytes */
1612 /*	 -2	 name too long to fit in buffer. */
1613 /* */
1614 static off_t
1615 dnsname_to_labels(u8 *const buf, size_t buf_len, off_t j,
1616 				  const char *name, const size_t name_len,
1617 				  struct dnslabel_table *table) {
1618 	const char *end = name + name_len;
1619 	int ref = 0;
1620 	u16 t_;
1621 
1622 #define APPEND16(x) do {						\
1623 		if (j + 2 > (off_t)buf_len)				\
1624 			goto overflow;					\
1625 		t_ = htons(x);						\
1626 		memcpy(buf + j, &t_, 2);				\
1627 		j += 2;							\
1628 	} while (0)
1629 #define APPEND32(x) do {						\
1630 		if (j + 4 > (off_t)buf_len)				\
1631 			goto overflow;					\
1632 		t32_ = htonl(x);					\
1633 		memcpy(buf + j, &t32_, 4);				\
1634 		j += 4;							\
1635 	} while (0)
1636 
1637 	if (name_len > 255) return -2;
1638 
1639 	for (;;) {
1640 		const char *const start = name;
1641 		if (table && (ref = dnslabel_table_get_pos(table, name)) >= 0) {
1642 			APPEND16(ref | 0xc000);
1643 			return j;
1644 		}
1645 		name = strchr(name, '.');
1646 		if (!name) {
1647 			const size_t label_len = end - start;
1648 			if (label_len > 63) return -1;
1649 			if ((size_t)(j+label_len+1) > buf_len) return -2;
1650 			if (table) dnslabel_table_add(table, start, j);
1651 			buf[j++] = (ev_uint8_t)label_len;
1652 
1653 			memcpy(buf + j, start, label_len);
1654 			j += (int) label_len;
1655 			break;
1656 		} else {
1657 			/* append length of the label. */
1658 			const size_t label_len = name - start;
1659 			if (label_len > 63) return -1;
1660 			if ((size_t)(j+label_len+1) > buf_len) return -2;
1661 			if (table) dnslabel_table_add(table, start, j);
1662 			buf[j++] = (ev_uint8_t)label_len;
1663 
1664 			memcpy(buf + j, start, label_len);
1665 			j += (int) label_len;
1666 			/* hop over the '.' */
1667 			name++;
1668 		}
1669 	}
1670 
1671 	/* the labels must be terminated by a 0. */
1672 	/* It's possible that the name ended in a . */
1673 	/* in which case the zero is already there */
1674 	if (!j || buf[j-1]) buf[j++] = 0;
1675 	return j;
1676  overflow:
1677 	return (-2);
1678 }
1679 
1680 /* Finds the length of a dns request for a DNS name of the given */
1681 /* length. The actual request may be smaller than the value returned */
1682 /* here */
1683 static size_t
1684 evdns_request_len(const size_t name_len) {
1685 	return 96 + /* length of the DNS standard header */
1686 		name_len + 2 +
1687 		4;  /* space for the resource type */
1688 }
1689 
1690 /* build a dns request packet into buf. buf should be at least as long */
1691 /* as evdns_request_len told you it should be. */
1692 /* */
1693 /* Returns the amount of space used. Negative on error. */
1694 static int
1695 evdns_request_data_build(const char *const name, const size_t name_len,
1696     const u16 trans_id, const u16 type, const u16 class,
1697     u8 *const buf, size_t buf_len) {
1698 	off_t j = 0;  /* current offset into buf */
1699 	u16 t_;	 /* used by the macros */
1700 
1701 	APPEND16(trans_id);
1702 	APPEND16(0x0100);  /* standard query, recusion needed */
1703 	APPEND16(1);  /* one question */
1704 	APPEND16(0);  /* no answers */
1705 	APPEND16(0);  /* no authority */
1706 	APPEND16(0);  /* no additional */
1707 
1708 	j = dnsname_to_labels(buf, buf_len, j, name, name_len, NULL);
1709 	if (j < 0) {
1710 		return (int)j;
1711 	}
1712 
1713 	APPEND16(type);
1714 	APPEND16(class);
1715 
1716 	return (int)j;
1717  overflow:
1718 	return (-1);
1719 }
1720 
1721 /* exported function */
1722 struct evdns_server_port *
1723 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)
1724 {
1725 	struct evdns_server_port *port;
1726 	if (flags)
1727 		return NULL; /* flags not yet implemented */
1728 	if (!(port = mm_malloc(sizeof(struct evdns_server_port))))
1729 		return NULL;
1730 	memset(port, 0, sizeof(struct evdns_server_port));
1731 
1732 
1733 	port->socket = socket;
1734 	port->refcnt = 1;
1735 	port->choked = 0;
1736 	port->closing = 0;
1737 	port->user_callback = cb;
1738 	port->user_data = user_data;
1739 	port->pending_replies = NULL;
1740 	port->event_base = base;
1741 
1742 	event_assign(&port->event, port->event_base,
1743 				 port->socket, EV_READ | EV_PERSIST,
1744 				 server_port_ready_callback, port);
1745 	if (event_add(&port->event, NULL) < 0) {
1746 		mm_free(port);
1747 		return NULL;
1748 	}
1749 	EVTHREAD_ALLOC_LOCK(port->lock, EVTHREAD_LOCKTYPE_RECURSIVE);
1750 	return port;
1751 }
1752 
1753 struct evdns_server_port *
1754 evdns_add_server_port(evutil_socket_t socket, int flags, evdns_request_callback_fn_type cb, void *user_data)
1755 {
1756 	return evdns_add_server_port_with_base(NULL, socket, flags, cb, user_data);
1757 }
1758 
1759 /* exported function */
1760 void
1761 evdns_close_server_port(struct evdns_server_port *port)
1762 {
1763 	EVDNS_LOCK(port);
1764 	if (--port->refcnt == 0) {
1765 		EVDNS_UNLOCK(port);
1766 		server_port_free(port);
1767 	} else {
1768 		port->closing = 1;
1769 		EVDNS_UNLOCK(port);
1770 	}
1771 }
1772 
1773 /* exported function */
1774 int
1775 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)
1776 {
1777 	struct server_request *req = TO_SERVER_REQUEST(req_);
1778 	struct server_reply_item **itemp, *item;
1779 	int *countp;
1780 	int result = -1;
1781 
1782 	EVDNS_LOCK(req->port);
1783 	if (req->response) /* have we already answered? */
1784 		goto done;
1785 
1786 	switch (section) {
1787 	case EVDNS_ANSWER_SECTION:
1788 		itemp = &req->answer;
1789 		countp = &req->n_answer;
1790 		break;
1791 	case EVDNS_AUTHORITY_SECTION:
1792 		itemp = &req->authority;
1793 		countp = &req->n_authority;
1794 		break;
1795 	case EVDNS_ADDITIONAL_SECTION:
1796 		itemp = &req->additional;
1797 		countp = &req->n_additional;
1798 		break;
1799 	default:
1800 		goto done;
1801 	}
1802 	while (*itemp) {
1803 		itemp = &((*itemp)->next);
1804 	}
1805 	item = mm_malloc(sizeof(struct server_reply_item));
1806 	if (!item)
1807 		goto done;
1808 	item->next = NULL;
1809 	if (!(item->name = mm_strdup(name))) {
1810 		mm_free(item);
1811 		goto done;
1812 	}
1813 	item->type = type;
1814 	item->dns_question_class = class;
1815 	item->ttl = ttl;
1816 	item->is_name = is_name != 0;
1817 	item->datalen = 0;
1818 	item->data = NULL;
1819 	if (data) {
1820 		if (item->is_name) {
1821 			if (!(item->data = mm_strdup(data))) {
1822 				mm_free(item->name);
1823 				mm_free(item);
1824 				goto done;
1825 			}
1826 			item->datalen = (u16)-1;
1827 		} else {
1828 			if (!(item->data = mm_malloc(datalen))) {
1829 				mm_free(item->name);
1830 				mm_free(item);
1831 				goto done;
1832 			}
1833 			item->datalen = datalen;
1834 			memcpy(item->data, data, datalen);
1835 		}
1836 	}
1837 
1838 	*itemp = item;
1839 	++(*countp);
1840 	result = 0;
1841 done:
1842 	EVDNS_UNLOCK(req->port);
1843 	return result;
1844 }
1845 
1846 /* exported function */
1847 int
1848 evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl)
1849 {
1850 	return evdns_server_request_add_reply(
1851 		  req, EVDNS_ANSWER_SECTION, name, TYPE_A, CLASS_INET,
1852 		  ttl, n*4, 0, addrs);
1853 }
1854 
1855 /* exported function */
1856 int
1857 evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, const void *addrs, int ttl)
1858 {
1859 	return evdns_server_request_add_reply(
1860 		  req, EVDNS_ANSWER_SECTION, name, TYPE_AAAA, CLASS_INET,
1861 		  ttl, n*16, 0, addrs);
1862 }
1863 
1864 /* exported function */
1865 int
1866 evdns_server_request_add_ptr_reply(struct evdns_server_request *req, struct in_addr *in, const char *inaddr_name, const char *hostname, int ttl)
1867 {
1868 	u32 a;
1869 	char buf[32];
1870 	if (in && inaddr_name)
1871 		return -1;
1872 	else if (!in && !inaddr_name)
1873 		return -1;
1874 	if (in) {
1875 		a = ntohl(in->s_addr);
1876 		evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa",
1877 				(int)(u8)((a	)&0xff),
1878 				(int)(u8)((a>>8 )&0xff),
1879 				(int)(u8)((a>>16)&0xff),
1880 				(int)(u8)((a>>24)&0xff));
1881 		inaddr_name = buf;
1882 	}
1883 	return evdns_server_request_add_reply(
1884 		  req, EVDNS_ANSWER_SECTION, inaddr_name, TYPE_PTR, CLASS_INET,
1885 		  ttl, -1, 1, hostname);
1886 }
1887 
1888 /* exported function */
1889 int
1890 evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl)
1891 {
1892 	return evdns_server_request_add_reply(
1893 		  req, EVDNS_ANSWER_SECTION, name, TYPE_CNAME, CLASS_INET,
1894 		  ttl, -1, 1, cname);
1895 }
1896 
1897 /* exported function */
1898 void
1899 evdns_server_request_set_flags(struct evdns_server_request *exreq, int flags)
1900 {
1901 	struct server_request *req = TO_SERVER_REQUEST(exreq);
1902 	req->base.flags &= ~(EVDNS_FLAGS_AA|EVDNS_FLAGS_RD);
1903 	req->base.flags |= flags;
1904 }
1905 
1906 static int
1907 evdns_server_request_format_response(struct server_request *req, int err)
1908 {
1909 	unsigned char buf[1500];
1910 	size_t buf_len = sizeof(buf);
1911 	off_t j = 0, r;
1912 	u16 t_;
1913 	u32 t32_;
1914 	int i;
1915 	u16 flags;
1916 	struct dnslabel_table table;
1917 
1918 	if (err < 0 || err > 15) return -1;
1919 
1920 	/* Set response bit and error code; copy OPCODE and RD fields from
1921 	 * question; copy RA and AA if set by caller. */
1922 	flags = req->base.flags;
1923 	flags |= (_QR_MASK | err);
1924 
1925 	dnslabel_table_init(&table);
1926 	APPEND16(req->trans_id);
1927 	APPEND16(flags);
1928 	APPEND16(req->base.nquestions);
1929 	APPEND16(req->n_answer);
1930 	APPEND16(req->n_authority);
1931 	APPEND16(req->n_additional);
1932 
1933 	/* Add questions. */
1934 	for (i=0; i < req->base.nquestions; ++i) {
1935 		const char *s = req->base.questions[i]->name;
1936 		j = dnsname_to_labels(buf, buf_len, j, s, strlen(s), &table);
1937 		if (j < 0) {
1938 			dnslabel_clear(&table);
1939 			return (int) j;
1940 		}
1941 		APPEND16(req->base.questions[i]->type);
1942 		APPEND16(req->base.questions[i]->dns_question_class);
1943 	}
1944 
1945 	/* Add answer, authority, and additional sections. */
1946 	for (i=0; i<3; ++i) {
1947 		struct server_reply_item *item;
1948 		if (i==0)
1949 			item = req->answer;
1950 		else if (i==1)
1951 			item = req->authority;
1952 		else
1953 			item = req->additional;
1954 		while (item) {
1955 			r = dnsname_to_labels(buf, buf_len, j, item->name, strlen(item->name), &table);
1956 			if (r < 0)
1957 				goto overflow;
1958 			j = r;
1959 
1960 			APPEND16(item->type);
1961 			APPEND16(item->dns_question_class);
1962 			APPEND32(item->ttl);
1963 			if (item->is_name) {
1964 				off_t len_idx = j, name_start;
1965 				j += 2;
1966 				name_start = j;
1967 				r = dnsname_to_labels(buf, buf_len, j, item->data, strlen(item->data), &table);
1968 				if (r < 0)
1969 					goto overflow;
1970 				j = r;
1971 				t_ = htons( (short) (j-name_start) );
1972 				memcpy(buf+len_idx, &t_, 2);
1973 			} else {
1974 				APPEND16(item->datalen);
1975 				if (j+item->datalen > (off_t)buf_len)
1976 					goto overflow;
1977 				memcpy(buf+j, item->data, item->datalen);
1978 				j += item->datalen;
1979 			}
1980 			item = item->next;
1981 		}
1982 	}
1983 
1984 	if (j > 512) {
1985 overflow:
1986 		j = 512;
1987 		buf[2] |= 0x02; /* set the truncated bit. */
1988 	}
1989 
1990 	req->response_len = j;
1991 
1992 	if (!(req->response = mm_malloc(req->response_len))) {
1993 		server_request_free_answers(req);
1994 		dnslabel_clear(&table);
1995 		return (-1);
1996 	}
1997 	memcpy(req->response, buf, req->response_len);
1998 	server_request_free_answers(req);
1999 	dnslabel_clear(&table);
2000 	return (0);
2001 }
2002 
2003 /* exported function */
2004 int
2005 evdns_server_request_respond(struct evdns_server_request *req_, int err)
2006 {
2007 	struct server_request *req = TO_SERVER_REQUEST(req_);
2008 	struct evdns_server_port *port = req->port;
2009 	int r = -1;
2010 
2011 	EVDNS_LOCK(port);
2012 	if (!req->response) {
2013 		if ((r = evdns_server_request_format_response(req, err))<0)
2014 			goto done;
2015 	}
2016 
2017 	r = sendto(port->socket, req->response, (int)req->response_len, 0,
2018 			   (struct sockaddr*) &req->addr, (ev_socklen_t)req->addrlen);
2019 	if (r<0) {
2020 		int sock_err = evutil_socket_geterror(port->socket);
2021 		if (EVUTIL_ERR_RW_RETRIABLE(sock_err))
2022 			goto done;
2023 
2024 		if (port->pending_replies) {
2025 			req->prev_pending = port->pending_replies->prev_pending;
2026 			req->next_pending = port->pending_replies;
2027 			req->prev_pending->next_pending =
2028 				req->next_pending->prev_pending = req;
2029 		} else {
2030 			req->prev_pending = req->next_pending = req;
2031 			port->pending_replies = req;
2032 			port->choked = 1;
2033 
2034 			(void) event_del(&port->event);
2035 			event_assign(&port->event, port->event_base, port->socket, (port->closing?0:EV_READ) | EV_WRITE | EV_PERSIST, server_port_ready_callback, port);
2036 
2037 			if (event_add(&port->event, NULL) < 0) {
2038 				log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server");
2039 			}
2040 
2041 		}
2042 
2043 		r = 1;
2044 		goto done;
2045 	}
2046 	if (server_request_free(req)) {
2047 		r = 0;
2048 		goto done;
2049 	}
2050 
2051 	if (port->pending_replies)
2052 		server_port_flush(port);
2053 
2054 	r = 0;
2055 done:
2056 	EVDNS_UNLOCK(port);
2057 	return r;
2058 }
2059 
2060 /* Free all storage held by RRs in req. */
2061 static void
2062 server_request_free_answers(struct server_request *req)
2063 {
2064 	struct server_reply_item *victim, *next, **list;
2065 	int i;
2066 	for (i = 0; i < 3; ++i) {
2067 		if (i==0)
2068 			list = &req->answer;
2069 		else if (i==1)
2070 			list = &req->authority;
2071 		else
2072 			list = &req->additional;
2073 
2074 		victim = *list;
2075 		while (victim) {
2076 			next = victim->next;
2077 			mm_free(victim->name);
2078 			if (victim->data)
2079 				mm_free(victim->data);
2080 			mm_free(victim);
2081 			victim = next;
2082 		}
2083 		*list = NULL;
2084 	}
2085 }
2086 
2087 /* Free all storage held by req, and remove links to it. */
2088 /* return true iff we just wound up freeing the server_port. */
2089 static int
2090 server_request_free(struct server_request *req)
2091 {
2092 	int i, rc=1, lock=0;
2093 	if (req->base.questions) {
2094 		for (i = 0; i < req->base.nquestions; ++i)
2095 			mm_free(req->base.questions[i]);
2096 		mm_free(req->base.questions);
2097 	}
2098 
2099 	if (req->port) {
2100 		EVDNS_LOCK(req->port);
2101 		lock=1;
2102 		if (req->port->pending_replies == req) {
2103 			if (req->next_pending && req->next_pending != req)
2104 				req->port->pending_replies = req->next_pending;
2105 			else
2106 				req->port->pending_replies = NULL;
2107 		}
2108 		rc = --req->port->refcnt;
2109 	}
2110 
2111 	if (req->response) {
2112 		mm_free(req->response);
2113 	}
2114 
2115 	server_request_free_answers(req);
2116 
2117 	if (req->next_pending && req->next_pending != req) {
2118 		req->next_pending->prev_pending = req->prev_pending;
2119 		req->prev_pending->next_pending = req->next_pending;
2120 	}
2121 
2122 	if (rc == 0) {
2123 		EVDNS_UNLOCK(req->port); /* ????? nickm */
2124 		server_port_free(req->port);
2125 		mm_free(req);
2126 		return (1);
2127 	}
2128 	if (lock)
2129 		EVDNS_UNLOCK(req->port);
2130 	mm_free(req);
2131 	return (0);
2132 }
2133 
2134 /* Free all storage held by an evdns_server_port.  Only called when  */
2135 static void
2136 server_port_free(struct evdns_server_port *port)
2137 {
2138 	EVUTIL_ASSERT(port);
2139 	EVUTIL_ASSERT(!port->refcnt);
2140 	EVUTIL_ASSERT(!port->pending_replies);
2141 	if (port->socket > 0) {
2142 		evutil_closesocket(port->socket);
2143 		port->socket = -1;
2144 	}
2145 	(void) event_del(&port->event);
2146 	event_debug_unassign(&port->event);
2147 	EVTHREAD_FREE_LOCK(port->lock, EVTHREAD_LOCKTYPE_RECURSIVE);
2148 	mm_free(port);
2149 }
2150 
2151 /* exported function */
2152 int
2153 evdns_server_request_drop(struct evdns_server_request *req_)
2154 {
2155 	struct server_request *req = TO_SERVER_REQUEST(req_);
2156 	server_request_free(req);
2157 	return 0;
2158 }
2159 
2160 /* exported function */
2161 int
2162 evdns_server_request_get_requesting_addr(struct evdns_server_request *req_, struct sockaddr *sa, int addr_len)
2163 {
2164 	struct server_request *req = TO_SERVER_REQUEST(req_);
2165 	if (addr_len < (int)req->addrlen)
2166 		return -1;
2167 	memcpy(sa, &(req->addr), req->addrlen);
2168 	return req->addrlen;
2169 }
2170 
2171 #undef APPEND16
2172 #undef APPEND32
2173 
2174 /* this is a libevent callback function which is called when a request */
2175 /* has timed out. */
2176 static void
2177 evdns_request_timeout_callback(evutil_socket_t fd, short events, void *arg) {
2178 	struct request *const req = (struct request *) arg;
2179 	struct evdns_base *base = req->base;
2180 
2181 	(void) fd;
2182 	(void) events;
2183 
2184 	log(EVDNS_LOG_DEBUG, "Request %p timed out", arg);
2185 	EVDNS_LOCK(base);
2186 
2187 	if (req->tx_count >= req->base->global_max_retransmits) {
2188 		struct nameserver *ns = req->ns;
2189 		/* this request has failed */
2190 		log(EVDNS_LOG_DEBUG, "Giving up on request %p; tx_count==%d",
2191 		    arg, req->tx_count);
2192 		reply_schedule_callback(req, 0, DNS_ERR_TIMEOUT, NULL);
2193 
2194 		request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1);
2195 		nameserver_failed(ns, "request timed out.");
2196 	} else {
2197 		/* retransmit it */
2198 		log(EVDNS_LOG_DEBUG, "Retransmitting request %p; tx_count==%d",
2199 		    arg, req->tx_count);
2200 		(void) evtimer_del(&req->timeout_event);
2201 		request_swap_ns(req, nameserver_pick(base));
2202 		evdns_request_transmit(req);
2203 
2204 		req->ns->timedout++;
2205 		if (req->ns->timedout > req->base->global_max_nameserver_timeout) {
2206 			req->ns->timedout = 0;
2207 			nameserver_failed(req->ns, "request timed out.");
2208 		}
2209 	}
2210 
2211 	EVDNS_UNLOCK(base);
2212 }
2213 
2214 /* try to send a request to a given server. */
2215 /* */
2216 /* return: */
2217 /*   0 ok */
2218 /*   1 temporary failure */
2219 /*   2 other failure */
2220 static int
2221 evdns_request_transmit_to(struct request *req, struct nameserver *server) {
2222 	int r;
2223 	ASSERT_LOCKED(req->base);
2224 	ASSERT_VALID_REQUEST(req);
2225 
2226 	if (server->requests_inflight == 1 &&
2227 		req->base->disable_when_inactive &&
2228 		event_add(&server->event, NULL) < 0) {
2229 		return 1;
2230 	}
2231 
2232 	r = sendto(server->socket, (void*)req->request, req->request_len, 0,
2233 	    (struct sockaddr *)&server->address, server->addrlen);
2234 	if (r < 0) {
2235 		int err = evutil_socket_geterror(server->socket);
2236 		if (EVUTIL_ERR_RW_RETRIABLE(err))
2237 			return 1;
2238 		nameserver_failed(req->ns, evutil_socket_error_to_string(err));
2239 		return 2;
2240 	} else if (r != (int)req->request_len) {
2241 		return 1;  /* short write */
2242 	} else {
2243 		return 0;
2244 	}
2245 }
2246 
2247 /* try to send a request, updating the fields of the request */
2248 /* as needed */
2249 /* */
2250 /* return: */
2251 /*   0 ok */
2252 /*   1 failed */
2253 static int
2254 evdns_request_transmit(struct request *req) {
2255 	int retcode = 0, r;
2256 
2257 	ASSERT_LOCKED(req->base);
2258 	ASSERT_VALID_REQUEST(req);
2259 	/* if we fail to send this packet then this flag marks it */
2260 	/* for evdns_transmit */
2261 	req->transmit_me = 1;
2262 	EVUTIL_ASSERT(req->trans_id != 0xffff);
2263 
2264 	if (!req->ns)
2265 	{
2266 		/* unable to transmit request if no nameservers */
2267 		return 1;
2268 	}
2269 
2270 	if (req->ns->choked) {
2271 		/* don't bother trying to write to a socket */
2272 		/* which we have had EAGAIN from */
2273 		return 1;
2274 	}
2275 
2276 	r = evdns_request_transmit_to(req, req->ns);
2277 	switch (r) {
2278 	case 1:
2279 		/* temp failure */
2280 		req->ns->choked = 1;
2281 		nameserver_write_waiting(req->ns, 1);
2282 		return 1;
2283 	case 2:
2284 		/* failed to transmit the request entirely. we can fallthrough since
2285 		 * we'll set a timeout, which will time out, and make us retransmit the
2286 		 * request anyway. */
2287 		retcode = 1;
2288 		EVUTIL_FALLTHROUGH;
2289 	default:
2290 		/* all ok */
2291 		log(EVDNS_LOG_DEBUG,
2292 		    "Setting timeout for request %p, sent to nameserver %p", req, req->ns);
2293 		if (evtimer_add(&req->timeout_event, &req->base->global_timeout) < 0) {
2294 			log(EVDNS_LOG_WARN,
2295 		      "Error from libevent when adding timer for request %p",
2296 			    req);
2297 			/* ???? Do more? */
2298 		}
2299 		req->tx_count++;
2300 		req->transmit_me = 0;
2301 		return retcode;
2302 	}
2303 }
2304 
2305 static void
2306 nameserver_probe_callback(int result, char type, int count, int ttl, void *addresses, void *arg) {
2307 	struct nameserver *const ns = (struct nameserver *) arg;
2308 	(void) type;
2309 	(void) count;
2310 	(void) ttl;
2311 	(void) addresses;
2312 
2313 	if (result == DNS_ERR_CANCEL) {
2314 		/* We canceled this request because the nameserver came up
2315 		 * for some other reason.  Do not change our opinion about
2316 		 * the nameserver. */
2317 		return;
2318 	}
2319 
2320 	EVDNS_LOCK(ns->base);
2321 	ns->probe_request = NULL;
2322 	if (result == DNS_ERR_NONE || result == DNS_ERR_NOTEXIST) {
2323 		/* this is a good reply */
2324 		nameserver_up(ns);
2325 	} else {
2326 		nameserver_probe_failed(ns);
2327 	}
2328 	EVDNS_UNLOCK(ns->base);
2329 }
2330 
2331 static void
2332 nameserver_send_probe(struct nameserver *const ns) {
2333 	struct evdns_request *handle;
2334 	struct request *req;
2335 	char addrbuf[128];
2336 	/* here we need to send a probe to a given nameserver */
2337 	/* in the hope that it is up now. */
2338 
2339 	ASSERT_LOCKED(ns->base);
2340 	log(EVDNS_LOG_DEBUG, "Sending probe to %s",
2341 	    evutil_format_sockaddr_port_(
2342 		    (struct sockaddr *)&ns->address,
2343 		    addrbuf, sizeof(addrbuf)));
2344 	handle = mm_calloc(1, sizeof(*handle));
2345 	if (!handle) return;
2346 	req = request_new(ns->base, handle, TYPE_A, "google.com", DNS_QUERY_NO_SEARCH, nameserver_probe_callback, ns);
2347 	if (!req) {
2348 		mm_free(handle);
2349 		return;
2350 	}
2351 	ns->probe_request = handle;
2352 	/* we force this into the inflight queue no matter what */
2353 	request_trans_id_set(req, transaction_id_pick(ns->base));
2354 	req->ns = ns;
2355 	request_submit(req);
2356 }
2357 
2358 /* returns: */
2359 /*   0 didn't try to transmit anything */
2360 /*   1 tried to transmit something */
2361 static int
2362 evdns_transmit(struct evdns_base *base) {
2363 	char did_try_to_transmit = 0;
2364 	int i;
2365 
2366 	ASSERT_LOCKED(base);
2367 	for (i = 0; i < base->n_req_heads; ++i) {
2368 		if (base->req_heads[i]) {
2369 			struct request *const started_at = base->req_heads[i], *req = started_at;
2370 			/* first transmit all the requests which are currently waiting */
2371 			do {
2372 				if (req->transmit_me) {
2373 					did_try_to_transmit = 1;
2374 					evdns_request_transmit(req);
2375 				}
2376 
2377 				req = req->next;
2378 			} while (req != started_at);
2379 		}
2380 	}
2381 
2382 	return did_try_to_transmit;
2383 }
2384 
2385 /* exported function */
2386 int
2387 evdns_base_count_nameservers(struct evdns_base *base)
2388 {
2389 	const struct nameserver *server;
2390 	int n = 0;
2391 
2392 	EVDNS_LOCK(base);
2393 	server = base->server_head;
2394 	if (!server)
2395 		goto done;
2396 	do {
2397 		++n;
2398 		server = server->next;
2399 	} while (server != base->server_head);
2400 done:
2401 	EVDNS_UNLOCK(base);
2402 	return n;
2403 }
2404 
2405 int
2406 evdns_count_nameservers(void)
2407 {
2408 	return evdns_base_count_nameservers(current_base);
2409 }
2410 
2411 /* exported function */
2412 int
2413 evdns_base_clear_nameservers_and_suspend(struct evdns_base *base)
2414 {
2415 	struct nameserver *server, *started_at;
2416 	int i;
2417 
2418 	EVDNS_LOCK(base);
2419 	server = base->server_head;
2420 	started_at = base->server_head;
2421 	if (!server) {
2422 		EVDNS_UNLOCK(base);
2423 		return 0;
2424 	}
2425 	while (1) {
2426 		struct nameserver *next = server->next;
2427 		(void) event_del(&server->event);
2428 		if (evtimer_initialized(&server->timeout_event))
2429 			(void) evtimer_del(&server->timeout_event);
2430 		if (server->probe_request) {
2431 			evdns_cancel_request(server->base, server->probe_request);
2432 			server->probe_request = NULL;
2433 		}
2434 		if (server->socket >= 0)
2435 			evutil_closesocket(server->socket);
2436 		mm_free(server);
2437 		if (next == started_at)
2438 			break;
2439 		server = next;
2440 	}
2441 	base->server_head = NULL;
2442 	base->global_good_nameservers = 0;
2443 
2444 	for (i = 0; i < base->n_req_heads; ++i) {
2445 		struct request *req, *req_started_at;
2446 		req = req_started_at = base->req_heads[i];
2447 		while (req) {
2448 			struct request *next = req->next;
2449 			req->tx_count = req->reissue_count = 0;
2450 			req->ns = NULL;
2451 			/* ???? What to do about searches? */
2452 			(void) evtimer_del(&req->timeout_event);
2453 			req->trans_id = 0;
2454 			req->transmit_me = 0;
2455 
2456 			base->global_requests_waiting++;
2457 			evdns_request_insert(req, &base->req_waiting_head);
2458 			/* We want to insert these suspended elements at the front of
2459 			 * the waiting queue, since they were pending before any of
2460 			 * the waiting entries were added.  This is a circular list,
2461 			 * so we can just shift the start back by one.*/
2462 			base->req_waiting_head = base->req_waiting_head->prev;
2463 
2464 			if (next == req_started_at)
2465 				break;
2466 			req = next;
2467 		}
2468 		base->req_heads[i] = NULL;
2469 	}
2470 
2471 	base->global_requests_inflight = 0;
2472 
2473 	EVDNS_UNLOCK(base);
2474 	return 0;
2475 }
2476 
2477 int
2478 evdns_clear_nameservers_and_suspend(void)
2479 {
2480 	return evdns_base_clear_nameservers_and_suspend(current_base);
2481 }
2482 
2483 
2484 /* exported function */
2485 int
2486 evdns_base_resume(struct evdns_base *base)
2487 {
2488 	EVDNS_LOCK(base);
2489 	evdns_requests_pump_waiting_queue(base);
2490 	EVDNS_UNLOCK(base);
2491 
2492 	return 0;
2493 }
2494 
2495 int
2496 evdns_resume(void)
2497 {
2498 	return evdns_base_resume(current_base);
2499 }
2500 
2501 static int
2502 evdns_nameserver_add_impl_(struct evdns_base *base, const struct sockaddr *address, int addrlen) {
2503 	/* first check to see if we already have this nameserver */
2504 
2505 	const struct nameserver *server = base->server_head, *const started_at = base->server_head;
2506 	struct nameserver *ns;
2507 	int err = 0;
2508 	char addrbuf[128];
2509 
2510 	ASSERT_LOCKED(base);
2511 	if (server) {
2512 		do {
2513 			if (!evutil_sockaddr_cmp((struct sockaddr*)&server->address, address, 1)) return 3;
2514 			server = server->next;
2515 		} while (server != started_at);
2516 	}
2517 	if (addrlen > (int)sizeof(ns->address)) {
2518 		log(EVDNS_LOG_DEBUG, "Addrlen %d too long.", (int)addrlen);
2519 		return 2;
2520 	}
2521 
2522 	ns = (struct nameserver *) mm_malloc(sizeof(struct nameserver));
2523 	if (!ns) return -1;
2524 
2525 	memset(ns, 0, sizeof(struct nameserver));
2526 	ns->base = base;
2527 
2528 	evtimer_assign(&ns->timeout_event, ns->base->event_base, nameserver_prod_callback, ns);
2529 
2530 	ns->socket = evutil_socket_(address->sa_family,
2531 	    SOCK_DGRAM|EVUTIL_SOCK_NONBLOCK|EVUTIL_SOCK_CLOEXEC, 0);
2532 	if (ns->socket < 0) { err = 1; goto out1; }
2533 
2534 	if (base->global_outgoing_addrlen &&
2535 	    !evutil_sockaddr_is_loopback_(address)) {
2536 		if (bind(ns->socket,
2537 			(struct sockaddr*)&base->global_outgoing_address,
2538 			base->global_outgoing_addrlen) < 0) {
2539 			log(EVDNS_LOG_WARN,"Couldn't bind to outgoing address");
2540 			err = 2;
2541 			goto out2;
2542 		}
2543 	}
2544 
2545 	if (base->so_rcvbuf) {
2546 		if (setsockopt(ns->socket, SOL_SOCKET, SO_RCVBUF,
2547 		    (void *)&base->so_rcvbuf, sizeof(base->so_rcvbuf))) {
2548 			log(EVDNS_LOG_WARN, "Couldn't set SO_RCVBUF to %i", base->so_rcvbuf);
2549 			err = -SO_RCVBUF;
2550 			goto out2;
2551 		}
2552 	}
2553 	if (base->so_sndbuf) {
2554 		if (setsockopt(ns->socket, SOL_SOCKET, SO_SNDBUF,
2555 		    (void *)&base->so_sndbuf, sizeof(base->so_sndbuf))) {
2556 			log(EVDNS_LOG_WARN, "Couldn't set SO_SNDBUF to %i", base->so_sndbuf);
2557 			err = -SO_SNDBUF;
2558 			goto out2;
2559 		}
2560 	}
2561 
2562 	memcpy(&ns->address, address, addrlen);
2563 	ns->addrlen = addrlen;
2564 	ns->state = 1;
2565 	event_assign(&ns->event, ns->base->event_base, ns->socket,
2566 				 EV_READ | EV_PERSIST, nameserver_ready_callback, ns);
2567 	if (!base->disable_when_inactive && event_add(&ns->event, NULL) < 0) {
2568 		err = 2;
2569 		goto out2;
2570 	}
2571 
2572 	log(EVDNS_LOG_DEBUG, "Added nameserver %s as %p",
2573 	    evutil_format_sockaddr_port_(address, addrbuf, sizeof(addrbuf)), ns);
2574 
2575 	/* insert this nameserver into the list of them */
2576 	if (!base->server_head) {
2577 		ns->next = ns->prev = ns;
2578 		base->server_head = ns;
2579 	} else {
2580 		ns->next = base->server_head->next;
2581 		ns->prev = base->server_head;
2582 		base->server_head->next = ns;
2583 		ns->next->prev = ns;
2584 	}
2585 
2586 	base->global_good_nameservers++;
2587 
2588 	return 0;
2589 
2590 out2:
2591 	evutil_closesocket(ns->socket);
2592 out1:
2593 	event_debug_unassign(&ns->event);
2594 	mm_free(ns);
2595 	log(EVDNS_LOG_WARN, "Unable to add nameserver %s: error %d",
2596 	    evutil_format_sockaddr_port_(address, addrbuf, sizeof(addrbuf)), err);
2597 	return err;
2598 }
2599 
2600 /* exported function */
2601 int
2602 evdns_base_nameserver_add(struct evdns_base *base, unsigned long int address)
2603 {
2604 	struct sockaddr_in sin;
2605 	int res;
2606 	memset(&sin, 0, sizeof(sin));
2607 	sin.sin_addr.s_addr = address;
2608 	sin.sin_port = htons(53);
2609 	sin.sin_family = AF_INET;
2610 	EVDNS_LOCK(base);
2611 	res = evdns_nameserver_add_impl_(base, (struct sockaddr*)&sin, sizeof(sin));
2612 	EVDNS_UNLOCK(base);
2613 	return res;
2614 }
2615 
2616 int
2617 evdns_nameserver_add(unsigned long int address) {
2618 	if (!current_base)
2619 		current_base = evdns_base_new(NULL, 0);
2620 	return evdns_base_nameserver_add(current_base, address);
2621 }
2622 
2623 static void
2624 sockaddr_setport(struct sockaddr *sa, ev_uint16_t port)
2625 {
2626 	if (sa->sa_family == AF_INET) {
2627 		((struct sockaddr_in *)sa)->sin_port = htons(port);
2628 	} else if (sa->sa_family == AF_INET6) {
2629 		((struct sockaddr_in6 *)sa)->sin6_port = htons(port);
2630 	}
2631 }
2632 
2633 static ev_uint16_t
2634 sockaddr_getport(struct sockaddr *sa)
2635 {
2636 	if (sa->sa_family == AF_INET) {
2637 		return ntohs(((struct sockaddr_in *)sa)->sin_port);
2638 	} else if (sa->sa_family == AF_INET6) {
2639 		return ntohs(((struct sockaddr_in6 *)sa)->sin6_port);
2640 	} else {
2641 		return 0;
2642 	}
2643 }
2644 
2645 /* exported function */
2646 int
2647 evdns_base_nameserver_ip_add(struct evdns_base *base, const char *ip_as_string) {
2648 	struct sockaddr_storage ss;
2649 	struct sockaddr *sa;
2650 	int len = sizeof(ss);
2651 	int res;
2652 	if (evutil_parse_sockaddr_port(ip_as_string, (struct sockaddr *)&ss,
2653 		&len)) {
2654 		log(EVDNS_LOG_WARN, "Unable to parse nameserver address %s",
2655 			ip_as_string);
2656 		return 4;
2657 	}
2658 	sa = (struct sockaddr *) &ss;
2659 	if (sockaddr_getport(sa) == 0)
2660 		sockaddr_setport(sa, 53);
2661 
2662 	EVDNS_LOCK(base);
2663 	res = evdns_nameserver_add_impl_(base, sa, len);
2664 	EVDNS_UNLOCK(base);
2665 	return res;
2666 }
2667 
2668 int
2669 evdns_nameserver_ip_add(const char *ip_as_string) {
2670 	if (!current_base)
2671 		current_base = evdns_base_new(NULL, 0);
2672 	return evdns_base_nameserver_ip_add(current_base, ip_as_string);
2673 }
2674 
2675 int
2676 evdns_base_nameserver_sockaddr_add(struct evdns_base *base,
2677     const struct sockaddr *sa, ev_socklen_t len, unsigned flags)
2678 {
2679 	int res;
2680 	EVUTIL_ASSERT(base);
2681 	EVDNS_LOCK(base);
2682 	res = evdns_nameserver_add_impl_(base, sa, len);
2683 	EVDNS_UNLOCK(base);
2684 	return res;
2685 }
2686 
2687 int
2688 evdns_base_get_nameserver_addr(struct evdns_base *base, int idx,
2689     struct sockaddr *sa, ev_socklen_t len)
2690 {
2691 	int result = -1;
2692 	int i;
2693 	struct nameserver *server;
2694 	EVDNS_LOCK(base);
2695 	server = base->server_head;
2696 	for (i = 0; i < idx && server; ++i, server = server->next) {
2697 		if (server->next == base->server_head)
2698 			goto done;
2699 	}
2700 	if (! server)
2701 		goto done;
2702 
2703 	if (server->addrlen > len) {
2704 		result = (int) server->addrlen;
2705 		goto done;
2706 	}
2707 
2708 	memcpy(sa, &server->address, server->addrlen);
2709 	result = (int) server->addrlen;
2710 done:
2711 	EVDNS_UNLOCK(base);
2712 	return result;
2713 }
2714 
2715 /* remove from the queue */
2716 static void
2717 evdns_request_remove(struct request *req, struct request **head)
2718 {
2719 	ASSERT_LOCKED(req->base);
2720 	ASSERT_VALID_REQUEST(req);
2721 
2722 #if 0
2723 	{
2724 		struct request *ptr;
2725 		int found = 0;
2726 		EVUTIL_ASSERT(*head != NULL);
2727 
2728 		ptr = *head;
2729 		do {
2730 			if (ptr == req) {
2731 				found = 1;
2732 				break;
2733 			}
2734 			ptr = ptr->next;
2735 		} while (ptr != *head);
2736 		EVUTIL_ASSERT(found);
2737 
2738 		EVUTIL_ASSERT(req->next);
2739 	}
2740 #endif
2741 
2742 	if (req->next == req) {
2743 		/* only item in the list */
2744 		*head = NULL;
2745 	} else {
2746 		req->next->prev = req->prev;
2747 		req->prev->next = req->next;
2748 		if (*head == req) *head = req->next;
2749 	}
2750 	req->next = req->prev = NULL;
2751 }
2752 
2753 /* insert into the tail of the queue */
2754 static void
2755 evdns_request_insert(struct request *req, struct request **head) {
2756 	ASSERT_LOCKED(req->base);
2757 	ASSERT_VALID_REQUEST(req);
2758 	if (!*head) {
2759 		*head = req;
2760 		req->next = req->prev = req;
2761 		return;
2762 	}
2763 
2764 	req->prev = (*head)->prev;
2765 	req->prev->next = req;
2766 	req->next = *head;
2767 	(*head)->prev = req;
2768 }
2769 
2770 static int
2771 string_num_dots(const char *s) {
2772 	int count = 0;
2773 	while ((s = strchr(s, '.'))) {
2774 		s++;
2775 		count++;
2776 	}
2777 	return count;
2778 }
2779 
2780 static struct request *
2781 request_new(struct evdns_base *base, struct evdns_request *handle, int type,
2782 	    const char *name, int flags, evdns_callback_type callback,
2783 	    void *user_ptr) {
2784 
2785 	const char issuing_now =
2786 	    (base->global_requests_inflight < base->global_max_requests_inflight) ? 1 : 0;
2787 
2788 	const size_t name_len = strlen(name);
2789 	const size_t request_max_len = evdns_request_len(name_len);
2790 	const u16 trans_id = issuing_now ? transaction_id_pick(base) : 0xffff;
2791 	/* the request data is alloced in a single block with the header */
2792 	struct request *const req =
2793 	    mm_malloc(sizeof(struct request) + request_max_len);
2794 	int rlen;
2795 	char namebuf[256];
2796 	(void) flags;
2797 
2798 	ASSERT_LOCKED(base);
2799 
2800 	if (!req) return NULL;
2801 
2802 	if (name_len >= sizeof(namebuf)) {
2803 		mm_free(req);
2804 		return NULL;
2805 	}
2806 
2807 	memset(req, 0, sizeof(struct request));
2808 	req->base = base;
2809 
2810 	evtimer_assign(&req->timeout_event, req->base->event_base, evdns_request_timeout_callback, req);
2811 
2812 	if (base->global_randomize_case) {
2813 		unsigned i;
2814 		char randbits[(sizeof(namebuf)+7)/8];
2815 		strlcpy(namebuf, name, sizeof(namebuf));
2816 		evutil_secure_rng_get_bytes(randbits, (name_len+7)/8);
2817 		for (i = 0; i < name_len; ++i) {
2818 			if (EVUTIL_ISALPHA_(namebuf[i])) {
2819 				if ((randbits[i >> 3] & (1<<(i & 7))))
2820 					namebuf[i] |= 0x20;
2821 				else
2822 					namebuf[i] &= ~0x20;
2823 			}
2824 		}
2825 		name = namebuf;
2826 	}
2827 
2828 	/* request data lives just after the header */
2829 	req->request = ((u8 *) req) + sizeof(struct request);
2830 	/* denotes that the request data shouldn't be free()ed */
2831 	req->request_appended = 1;
2832 	rlen = evdns_request_data_build(name, name_len, trans_id,
2833 	    type, CLASS_INET, req->request, request_max_len);
2834 	if (rlen < 0)
2835 		goto err1;
2836 
2837 	req->request_len = rlen;
2838 	req->trans_id = trans_id;
2839 	req->tx_count = 0;
2840 	req->request_type = type;
2841 	req->user_pointer = user_ptr;
2842 	req->user_callback = callback;
2843 	req->ns = issuing_now ? nameserver_pick(base) : NULL;
2844 	req->next = req->prev = NULL;
2845 	req->handle = handle;
2846 	if (handle) {
2847 		handle->current_req = req;
2848 		handle->base = base;
2849 	}
2850 
2851 	return req;
2852 err1:
2853 	mm_free(req);
2854 	return NULL;
2855 }
2856 
2857 static void
2858 request_submit(struct request *const req) {
2859 	struct evdns_base *base = req->base;
2860 	ASSERT_LOCKED(base);
2861 	ASSERT_VALID_REQUEST(req);
2862 	if (req->ns) {
2863 		/* if it has a nameserver assigned then this is going */
2864 		/* straight into the inflight queue */
2865 		evdns_request_insert(req, &REQ_HEAD(base, req->trans_id));
2866 
2867 		base->global_requests_inflight++;
2868 		req->ns->requests_inflight++;
2869 
2870 		evdns_request_transmit(req);
2871 	} else {
2872 		evdns_request_insert(req, &base->req_waiting_head);
2873 		base->global_requests_waiting++;
2874 	}
2875 }
2876 
2877 /* exported function */
2878 void
2879 evdns_cancel_request(struct evdns_base *base, struct evdns_request *handle)
2880 {
2881 	struct request *req;
2882 
2883 	if (!handle->current_req)
2884 		return;
2885 
2886 	if (!base) {
2887 		/* This redundancy is silly; can we fix it? (Not for 2.0) XXXX */
2888 		base = handle->base;
2889 		if (!base)
2890 			base = handle->current_req->base;
2891 	}
2892 
2893 	EVDNS_LOCK(base);
2894 	if (handle->pending_cb) {
2895 		EVDNS_UNLOCK(base);
2896 		return;
2897 	}
2898 
2899 	req = handle->current_req;
2900 	ASSERT_VALID_REQUEST(req);
2901 
2902 	reply_schedule_callback(req, 0, DNS_ERR_CANCEL, NULL);
2903 	if (req->ns) {
2904 		/* remove from inflight queue */
2905 		request_finished(req, &REQ_HEAD(base, req->trans_id), 1);
2906 	} else {
2907 		/* remove from global_waiting head */
2908 		request_finished(req, &base->req_waiting_head, 1);
2909 	}
2910 	EVDNS_UNLOCK(base);
2911 }
2912 
2913 /* exported function */
2914 struct evdns_request *
2915 evdns_base_resolve_ipv4(struct evdns_base *base, const char *name, int flags,
2916     evdns_callback_type callback, void *ptr) {
2917 	struct evdns_request *handle;
2918 	struct request *req;
2919 	log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name);
2920 	handle = mm_calloc(1, sizeof(*handle));
2921 	if (handle == NULL)
2922 		return NULL;
2923 	EVDNS_LOCK(base);
2924 	if (flags & DNS_QUERY_NO_SEARCH) {
2925 		req =
2926 			request_new(base, handle, TYPE_A, name, flags,
2927 				    callback, ptr);
2928 		if (req)
2929 			request_submit(req);
2930 	} else {
2931 		search_request_new(base, handle, TYPE_A, name, flags,
2932 		    callback, ptr);
2933 	}
2934 	if (handle->current_req == NULL) {
2935 		mm_free(handle);
2936 		handle = NULL;
2937 	}
2938 	EVDNS_UNLOCK(base);
2939 	return handle;
2940 }
2941 
2942 int evdns_resolve_ipv4(const char *name, int flags,
2943 					   evdns_callback_type callback, void *ptr)
2944 {
2945 	return evdns_base_resolve_ipv4(current_base, name, flags, callback, ptr)
2946 		? 0 : -1;
2947 }
2948 
2949 
2950 /* exported function */
2951 struct evdns_request *
2952 evdns_base_resolve_ipv6(struct evdns_base *base,
2953     const char *name, int flags,
2954     evdns_callback_type callback, void *ptr)
2955 {
2956 	struct evdns_request *handle;
2957 	struct request *req;
2958 	log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name);
2959 	handle = mm_calloc(1, sizeof(*handle));
2960 	if (handle == NULL)
2961 		return NULL;
2962 	EVDNS_LOCK(base);
2963 	if (flags & DNS_QUERY_NO_SEARCH) {
2964 		req = request_new(base, handle, TYPE_AAAA, name, flags,
2965 				  callback, ptr);
2966 		if (req)
2967 			request_submit(req);
2968 	} else {
2969 		search_request_new(base, handle, TYPE_AAAA, name, flags,
2970 		    callback, ptr);
2971 	}
2972 	if (handle->current_req == NULL) {
2973 		mm_free(handle);
2974 		handle = NULL;
2975 	}
2976 	EVDNS_UNLOCK(base);
2977 	return handle;
2978 }
2979 
2980 int evdns_resolve_ipv6(const char *name, int flags,
2981     evdns_callback_type callback, void *ptr) {
2982 	return evdns_base_resolve_ipv6(current_base, name, flags, callback, ptr)
2983 		? 0 : -1;
2984 }
2985 
2986 struct evdns_request *
2987 evdns_base_resolve_reverse(struct evdns_base *base, const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) {
2988 	char buf[32];
2989 	struct evdns_request *handle;
2990 	struct request *req;
2991 	u32 a;
2992 	EVUTIL_ASSERT(in);
2993 	a = ntohl(in->s_addr);
2994 	evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa",
2995 			(int)(u8)((a	)&0xff),
2996 			(int)(u8)((a>>8 )&0xff),
2997 			(int)(u8)((a>>16)&0xff),
2998 			(int)(u8)((a>>24)&0xff));
2999 	handle = mm_calloc(1, sizeof(*handle));
3000 	if (handle == NULL)
3001 		return NULL;
3002 	log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf);
3003 	EVDNS_LOCK(base);
3004 	req = request_new(base, handle, TYPE_PTR, buf, flags, callback, ptr);
3005 	if (req)
3006 		request_submit(req);
3007 	if (handle->current_req == NULL) {
3008 		mm_free(handle);
3009 		handle = NULL;
3010 	}
3011 	EVDNS_UNLOCK(base);
3012 	return (handle);
3013 }
3014 
3015 int evdns_resolve_reverse(const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) {
3016 	return evdns_base_resolve_reverse(current_base, in, flags, callback, ptr)
3017 		? 0 : -1;
3018 }
3019 
3020 struct evdns_request *
3021 evdns_base_resolve_reverse_ipv6(struct evdns_base *base, const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) {
3022 	/* 32 nybbles, 32 periods, "ip6.arpa", NUL. */
3023 	char buf[73];
3024 	char *cp;
3025 	struct evdns_request *handle;
3026 	struct request *req;
3027 	int i;
3028 	EVUTIL_ASSERT(in);
3029 	cp = buf;
3030 	for (i=15; i >= 0; --i) {
3031 		u8 byte = in->s6_addr[i];
3032 		*cp++ = "0123456789abcdef"[byte & 0x0f];
3033 		*cp++ = '.';
3034 		*cp++ = "0123456789abcdef"[byte >> 4];
3035 		*cp++ = '.';
3036 	}
3037 	EVUTIL_ASSERT(cp + strlen("ip6.arpa") < buf+sizeof(buf));
3038 	memcpy(cp, "ip6.arpa", strlen("ip6.arpa")+1);
3039 	handle = mm_calloc(1, sizeof(*handle));
3040 	if (handle == NULL)
3041 		return NULL;
3042 	log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf);
3043 	EVDNS_LOCK(base);
3044 	req = request_new(base, handle, TYPE_PTR, buf, flags, callback, ptr);
3045 	if (req)
3046 		request_submit(req);
3047 	if (handle->current_req == NULL) {
3048 		mm_free(handle);
3049 		handle = NULL;
3050 	}
3051 	EVDNS_UNLOCK(base);
3052 	return (handle);
3053 }
3054 
3055 int evdns_resolve_reverse_ipv6(const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) {
3056 	return evdns_base_resolve_reverse_ipv6(current_base, in, flags, callback, ptr)
3057 		? 0 : -1;
3058 }
3059 
3060 /* ================================================================= */
3061 /* Search support */
3062 /* */
3063 /* the libc resolver has support for searching a number of domains */
3064 /* to find a name. If nothing else then it takes the single domain */
3065 /* from the gethostname() call. */
3066 /* */
3067 /* It can also be configured via the domain and search options in a */
3068 /* resolv.conf. */
3069 /* */
3070 /* The ndots option controls how many dots it takes for the resolver */
3071 /* to decide that a name is non-local and so try a raw lookup first. */
3072 
3073 struct search_domain {
3074 	int len;
3075 	struct search_domain *next;
3076 	/* the text string is appended to this structure */
3077 };
3078 
3079 struct search_state {
3080 	int refcount;
3081 	int ndots;
3082 	int num_domains;
3083 	struct search_domain *head;
3084 };
3085 
3086 static void
3087 search_state_decref(struct search_state *const state) {
3088 	if (!state) return;
3089 	state->refcount--;
3090 	if (!state->refcount) {
3091 		struct search_domain *next, *dom;
3092 		for (dom = state->head; dom; dom = next) {
3093 			next = dom->next;
3094 			mm_free(dom);
3095 		}
3096 		mm_free(state);
3097 	}
3098 }
3099 
3100 static struct search_state *
3101 search_state_new(void) {
3102 	struct search_state *state = (struct search_state *) mm_malloc(sizeof(struct search_state));
3103 	if (!state) return NULL;
3104 	memset(state, 0, sizeof(struct search_state));
3105 	state->refcount = 1;
3106 	state->ndots = 1;
3107 
3108 	return state;
3109 }
3110 
3111 static void
3112 search_postfix_clear(struct evdns_base *base) {
3113 	search_state_decref(base->global_search_state);
3114 
3115 	base->global_search_state = search_state_new();
3116 }
3117 
3118 /* exported function */
3119 void
3120 evdns_base_search_clear(struct evdns_base *base)
3121 {
3122 	EVDNS_LOCK(base);
3123 	search_postfix_clear(base);
3124 	EVDNS_UNLOCK(base);
3125 }
3126 
3127 void
3128 evdns_search_clear(void) {
3129 	evdns_base_search_clear(current_base);
3130 }
3131 
3132 static void
3133 search_postfix_add(struct evdns_base *base, const char *domain) {
3134 	size_t domain_len;
3135 	struct search_domain *sdomain;
3136 	while (domain[0] == '.') domain++;
3137 	domain_len = strlen(domain);
3138 
3139 	ASSERT_LOCKED(base);
3140 	if (!base->global_search_state) base->global_search_state = search_state_new();
3141 	if (!base->global_search_state) return;
3142 	base->global_search_state->num_domains++;
3143 
3144 	sdomain = (struct search_domain *) mm_malloc(sizeof(struct search_domain) + domain_len);
3145 	if (!sdomain) return;
3146 	memcpy( ((u8 *) sdomain) + sizeof(struct search_domain), domain, domain_len);
3147 	sdomain->next = base->global_search_state->head;
3148 	sdomain->len = (int) domain_len;
3149 
3150 	base->global_search_state->head = sdomain;
3151 }
3152 
3153 /* reverse the order of members in the postfix list. This is needed because, */
3154 /* when parsing resolv.conf we push elements in the wrong order */
3155 static void
3156 search_reverse(struct evdns_base *base) {
3157 	struct search_domain *cur, *prev = NULL, *next;
3158 	ASSERT_LOCKED(base);
3159 	cur = base->global_search_state->head;
3160 	while (cur) {
3161 		next = cur->next;
3162 		cur->next = prev;
3163 		prev = cur;
3164 		cur = next;
3165 	}
3166 
3167 	base->global_search_state->head = prev;
3168 }
3169 
3170 /* exported function */
3171 void
3172 evdns_base_search_add(struct evdns_base *base, const char *domain) {
3173 	EVDNS_LOCK(base);
3174 	search_postfix_add(base, domain);
3175 	EVDNS_UNLOCK(base);
3176 }
3177 void
3178 evdns_search_add(const char *domain) {
3179 	evdns_base_search_add(current_base, domain);
3180 }
3181 
3182 /* exported function */
3183 void
3184 evdns_base_search_ndots_set(struct evdns_base *base, const int ndots) {
3185 	EVDNS_LOCK(base);
3186 	if (!base->global_search_state) base->global_search_state = search_state_new();
3187 	if (base->global_search_state)
3188 		base->global_search_state->ndots = ndots;
3189 	EVDNS_UNLOCK(base);
3190 }
3191 void
3192 evdns_search_ndots_set(const int ndots) {
3193 	evdns_base_search_ndots_set(current_base, ndots);
3194 }
3195 
3196 static void
3197 search_set_from_hostname(struct evdns_base *base) {
3198 	char hostname[HOST_NAME_MAX + 1], *domainname;
3199 
3200 	ASSERT_LOCKED(base);
3201 	search_postfix_clear(base);
3202 	if (gethostname(hostname, sizeof(hostname))) return;
3203 	domainname = strchr(hostname, '.');
3204 	if (!domainname) return;
3205 	search_postfix_add(base, domainname);
3206 }
3207 
3208 /* warning: returns malloced string */
3209 static char *
3210 search_make_new(const struct search_state *const state, int n, const char *const base_name) {
3211 	const size_t base_len = strlen(base_name);
3212 	char need_to_append_dot;
3213 	struct search_domain *dom;
3214 
3215 	if (!base_len) return NULL;
3216 	need_to_append_dot = base_name[base_len - 1] == '.' ? 0 : 1;
3217 
3218 	for (dom = state->head; dom; dom = dom->next) {
3219 		if (!n--) {
3220 			/* this is the postfix we want */
3221 			/* the actual postfix string is kept at the end of the structure */
3222 			const u8 *const postfix = ((u8 *) dom) + sizeof(struct search_domain);
3223 			const int postfix_len = dom->len;
3224 			char *const newname = (char *) mm_malloc(base_len + need_to_append_dot + postfix_len + 1);
3225 			if (!newname) return NULL;
3226 			memcpy(newname, base_name, base_len);
3227 			if (need_to_append_dot) newname[base_len] = '.';
3228 			memcpy(newname + base_len + need_to_append_dot, postfix, postfix_len);
3229 			newname[base_len + need_to_append_dot + postfix_len] = 0;
3230 			return newname;
3231 		}
3232 	}
3233 
3234 	/* we ran off the end of the list and still didn't find the requested string */
3235 	EVUTIL_ASSERT(0);
3236 	return NULL; /* unreachable; stops warnings in some compilers. */
3237 }
3238 
3239 static struct request *
3240 search_request_new(struct evdns_base *base, struct evdns_request *handle,
3241 		   int type, const char *const name, int flags,
3242 		   evdns_callback_type user_callback, void *user_arg) {
3243 	ASSERT_LOCKED(base);
3244 	EVUTIL_ASSERT(type == TYPE_A || type == TYPE_AAAA);
3245 	EVUTIL_ASSERT(handle->current_req == NULL);
3246 	if ( ((flags & DNS_QUERY_NO_SEARCH) == 0) &&
3247 	     base->global_search_state &&
3248 		 base->global_search_state->num_domains) {
3249 		/* we have some domains to search */
3250 		struct request *req;
3251 		if (string_num_dots(name) >= base->global_search_state->ndots) {
3252 			req = request_new(base, handle, type, name, flags, user_callback, user_arg);
3253 			if (!req) return NULL;
3254 			handle->search_index = -1;
3255 		} else {
3256 			char *const new_name = search_make_new(base->global_search_state, 0, name);
3257 			if (!new_name) return NULL;
3258 			req = request_new(base, handle, type, new_name, flags, user_callback, user_arg);
3259 			mm_free(new_name);
3260 			if (!req) return NULL;
3261 			handle->search_index = 0;
3262 		}
3263 		EVUTIL_ASSERT(handle->search_origname == NULL);
3264 		handle->search_origname = mm_strdup(name);
3265 		if (handle->search_origname == NULL) {
3266 			/* XXX Should we dealloc req? If yes, how? */
3267 			if (req)
3268 				mm_free(req);
3269 			return NULL;
3270 		}
3271 		handle->search_state = base->global_search_state;
3272 		handle->search_flags = flags;
3273 		base->global_search_state->refcount++;
3274 		request_submit(req);
3275 		return req;
3276 	} else {
3277 		struct request *const req = request_new(base, handle, type, name, flags, user_callback, user_arg);
3278 		if (!req) return NULL;
3279 		request_submit(req);
3280 		return req;
3281 	}
3282 }
3283 
3284 /* this is called when a request has failed to find a name. We need to check */
3285 /* if it is part of a search and, if so, try the next name in the list */
3286 /* returns: */
3287 /*   0 another request has been submitted */
3288 /*   1 no more requests needed */
3289 static int
3290 search_try_next(struct evdns_request *const handle) {
3291 	struct request *req = handle->current_req;
3292 	struct evdns_base *base = req->base;
3293 	struct request *newreq;
3294 	ASSERT_LOCKED(base);
3295 	if (handle->search_state) {
3296 		/* it is part of a search */
3297 		char *new_name;
3298 		handle->search_index++;
3299 		if (handle->search_index >= handle->search_state->num_domains) {
3300 			/* no more postfixes to try, however we may need to try */
3301 			/* this name without a postfix */
3302 			if (string_num_dots(handle->search_origname) < handle->search_state->ndots) {
3303 				/* yep, we need to try it raw */
3304 				newreq = request_new(base, NULL, req->request_type, handle->search_origname, handle->search_flags, req->user_callback, req->user_pointer);
3305 				log(EVDNS_LOG_DEBUG, "Search: trying raw query %s", handle->search_origname);
3306 				if (newreq) {
3307 					search_request_finished(handle);
3308 					goto submit_next;
3309 				}
3310 			}
3311 			return 1;
3312 		}
3313 
3314 		new_name = search_make_new(handle->search_state, handle->search_index, handle->search_origname);
3315 		if (!new_name) return 1;
3316 		log(EVDNS_LOG_DEBUG, "Search: now trying %s (%d)", new_name, handle->search_index);
3317 		newreq = request_new(base, NULL, req->request_type, new_name, handle->search_flags, req->user_callback, req->user_pointer);
3318 		mm_free(new_name);
3319 		if (!newreq) return 1;
3320 		goto submit_next;
3321 	}
3322 	return 1;
3323 
3324 submit_next:
3325 	request_finished(req, &REQ_HEAD(req->base, req->trans_id), 0);
3326 	handle->current_req = newreq;
3327 	newreq->handle = handle;
3328 	request_submit(newreq);
3329 	return 0;
3330 }
3331 
3332 static void
3333 search_request_finished(struct evdns_request *const handle) {
3334 	ASSERT_LOCKED(handle->current_req->base);
3335 	if (handle->search_state) {
3336 		search_state_decref(handle->search_state);
3337 		handle->search_state = NULL;
3338 	}
3339 	if (handle->search_origname) {
3340 		mm_free(handle->search_origname);
3341 		handle->search_origname = NULL;
3342 	}
3343 }
3344 
3345 /* ================================================================= */
3346 /* Parsing resolv.conf files */
3347 
3348 static void
3349 evdns_resolv_set_defaults(struct evdns_base *base, int flags) {
3350 	int add_default = flags & DNS_OPTION_NAMESERVERS;
3351 	if (flags & DNS_OPTION_NAMESERVERS_NO_DEFAULT)
3352 		add_default = 0;
3353 
3354 	/* if the file isn't found then we assume a local resolver */
3355 	ASSERT_LOCKED(base);
3356 	if (flags & DNS_OPTION_SEARCH)
3357 		search_set_from_hostname(base);
3358 	if (add_default)
3359 		evdns_base_nameserver_ip_add(base, "127.0.0.1");
3360 }
3361 
3362 #ifndef EVENT__HAVE_STRTOK_R
3363 static char *
3364 strtok_r(char *s, const char *delim, char **state) {
3365 	char *cp, *start;
3366 	start = cp = s ? s : *state;
3367 	if (!cp)
3368 		return NULL;
3369 	while (*cp && !strchr(delim, *cp))
3370 		++cp;
3371 	if (!*cp) {
3372 		if (cp == start)
3373 			return NULL;
3374 		*state = NULL;
3375 		return start;
3376 	} else {
3377 		*cp++ = '\0';
3378 		*state = cp;
3379 		return start;
3380 	}
3381 }
3382 #endif
3383 
3384 /* helper version of atoi which returns -1 on error */
3385 static int
3386 strtoint(const char *const str)
3387 {
3388 	char *endptr;
3389 	const int r = strtol(str, &endptr, 10);
3390 	if (*endptr) return -1;
3391 	return r;
3392 }
3393 
3394 /* Parse a number of seconds into a timeval; return -1 on error. */
3395 static int
3396 evdns_strtotimeval(const char *const str, struct timeval *out)
3397 {
3398 	double d;
3399 	char *endptr;
3400 	d = strtod(str, &endptr);
3401 	if (*endptr) return -1;
3402 	if (d < 0) return -1;
3403 	out->tv_sec = (int) d;
3404 	out->tv_usec = (int) ((d - (int) d)*1000000);
3405 	if (out->tv_sec == 0 && out->tv_usec < 1000) /* less than 1 msec */
3406 		return -1;
3407 	return 0;
3408 }
3409 
3410 /* helper version of atoi that returns -1 on error and clips to bounds. */
3411 static int
3412 strtoint_clipped(const char *const str, int min, int max)
3413 {
3414 	int r = strtoint(str);
3415 	if (r == -1)
3416 		return r;
3417 	else if (r<min)
3418 		return min;
3419 	else if (r>max)
3420 		return max;
3421 	else
3422 		return r;
3423 }
3424 
3425 static int
3426 evdns_base_set_max_requests_inflight(struct evdns_base *base, int maxinflight)
3427 {
3428 	int old_n_heads = base->n_req_heads, n_heads;
3429 	struct request **old_heads = base->req_heads, **new_heads, *req;
3430 	int i;
3431 
3432 	ASSERT_LOCKED(base);
3433 	if (maxinflight < 1)
3434 		maxinflight = 1;
3435 	n_heads = (maxinflight+4) / 5;
3436 	EVUTIL_ASSERT(n_heads > 0);
3437 	new_heads = mm_calloc(n_heads, sizeof(struct request*));
3438 	if (!new_heads)
3439 		return (-1);
3440 	if (old_heads) {
3441 		for (i = 0; i < old_n_heads; ++i) {
3442 			while (old_heads[i]) {
3443 				req = old_heads[i];
3444 				evdns_request_remove(req, &old_heads[i]);
3445 				evdns_request_insert(req, &new_heads[req->trans_id % n_heads]);
3446 			}
3447 		}
3448 		mm_free(old_heads);
3449 	}
3450 	base->req_heads = new_heads;
3451 	base->n_req_heads = n_heads;
3452 	base->global_max_requests_inflight = maxinflight;
3453 	return (0);
3454 }
3455 
3456 /* exported function */
3457 int
3458 evdns_base_set_option(struct evdns_base *base,
3459     const char *option, const char *val)
3460 {
3461 	int res;
3462 	EVDNS_LOCK(base);
3463 	res = evdns_base_set_option_impl(base, option, val, DNS_OPTIONS_ALL);
3464 	EVDNS_UNLOCK(base);
3465 	return res;
3466 }
3467 
3468 static inline int
3469 str_matches_option(const char *s1, const char *optionname)
3470 {
3471 	/* Option names are given as "option:" We accept either 'option' in
3472 	 * s1, or 'option:randomjunk'.  The latter form is to implement the
3473 	 * resolv.conf parser. */
3474 	size_t optlen = strlen(optionname);
3475 	size_t slen = strlen(s1);
3476 	if (slen == optlen || slen == optlen - 1)
3477 		return !strncmp(s1, optionname, slen);
3478 	else if (slen > optlen)
3479 		return !strncmp(s1, optionname, optlen);
3480 	else
3481 		return 0;
3482 }
3483 
3484 static int
3485 evdns_base_set_option_impl(struct evdns_base *base,
3486     const char *option, const char *val, int flags)
3487 {
3488 	ASSERT_LOCKED(base);
3489 	if (str_matches_option(option, "ndots:")) {
3490 		const int ndots = strtoint(val);
3491 		if (ndots == -1) return -1;
3492 		if (!(flags & DNS_OPTION_SEARCH)) return 0;
3493 		log(EVDNS_LOG_DEBUG, "Setting ndots to %d", ndots);
3494 		if (!base->global_search_state) base->global_search_state = search_state_new();
3495 		if (!base->global_search_state) return -1;
3496 		base->global_search_state->ndots = ndots;
3497 	} else if (str_matches_option(option, "timeout:")) {
3498 		struct timeval tv;
3499 		if (evdns_strtotimeval(val, &tv) == -1) return -1;
3500 		if (!(flags & DNS_OPTION_MISC)) return 0;
3501 		log(EVDNS_LOG_DEBUG, "Setting timeout to %s", val);
3502 		memcpy(&base->global_timeout, &tv, sizeof(struct timeval));
3503 	} else if (str_matches_option(option, "getaddrinfo-allow-skew:")) {
3504 		struct timeval tv;
3505 		if (evdns_strtotimeval(val, &tv) == -1) return -1;
3506 		if (!(flags & DNS_OPTION_MISC)) return 0;
3507 		log(EVDNS_LOG_DEBUG, "Setting getaddrinfo-allow-skew to %s",
3508 		    val);
3509 		memcpy(&base->global_getaddrinfo_allow_skew, &tv,
3510 		    sizeof(struct timeval));
3511 	} else if (str_matches_option(option, "max-timeouts:")) {
3512 		const int maxtimeout = strtoint_clipped(val, 1, 255);
3513 		if (maxtimeout == -1) return -1;
3514 		if (!(flags & DNS_OPTION_MISC)) return 0;
3515 		log(EVDNS_LOG_DEBUG, "Setting maximum allowed timeouts to %d",
3516 			maxtimeout);
3517 		base->global_max_nameserver_timeout = maxtimeout;
3518 	} else if (str_matches_option(option, "max-inflight:")) {
3519 		const int maxinflight = strtoint_clipped(val, 1, 65000);
3520 		if (maxinflight == -1) return -1;
3521 		if (!(flags & DNS_OPTION_MISC)) return 0;
3522 		log(EVDNS_LOG_DEBUG, "Setting maximum inflight requests to %d",
3523 			maxinflight);
3524 		evdns_base_set_max_requests_inflight(base, maxinflight);
3525 	} else if (str_matches_option(option, "attempts:")) {
3526 		int retries = strtoint(val);
3527 		if (retries == -1) return -1;
3528 		if (retries > 255) retries = 255;
3529 		if (!(flags & DNS_OPTION_MISC)) return 0;
3530 		log(EVDNS_LOG_DEBUG, "Setting retries to %d", retries);
3531 		base->global_max_retransmits = retries;
3532 	} else if (str_matches_option(option, "randomize-case:")) {
3533 		int randcase = strtoint(val);
3534 		if (randcase == -1) return -1;
3535 		if (!(flags & DNS_OPTION_MISC)) return 0;
3536 		base->global_randomize_case = randcase;
3537 	} else if (str_matches_option(option, "bind-to:")) {
3538 		/* XXX This only applies to successive nameservers, not
3539 		 * to already-configured ones.	We might want to fix that. */
3540 		int len = sizeof(base->global_outgoing_address);
3541 		if (!(flags & DNS_OPTION_NAMESERVERS)) return 0;
3542 		if (evutil_parse_sockaddr_port(val,
3543 			(struct sockaddr*)&base->global_outgoing_address, &len))
3544 			return -1;
3545 		base->global_outgoing_addrlen = len;
3546 	} else if (str_matches_option(option, "initial-probe-timeout:")) {
3547 		struct timeval tv;
3548 		if (evdns_strtotimeval(val, &tv) == -1) return -1;
3549 		if (tv.tv_sec > 3600)
3550 			tv.tv_sec = 3600;
3551 		if (!(flags & DNS_OPTION_MISC)) return 0;
3552 		log(EVDNS_LOG_DEBUG, "Setting initial probe timeout to %s",
3553 		    val);
3554 		memcpy(&base->global_nameserver_probe_initial_timeout, &tv,
3555 		    sizeof(tv));
3556 	} else if (str_matches_option(option, "so-rcvbuf:")) {
3557 		int buf = strtoint(val);
3558 		if (buf == -1) return -1;
3559 		if (!(flags & DNS_OPTION_MISC)) return 0;
3560 		log(EVDNS_LOG_DEBUG, "Setting SO_RCVBUF to %s", val);
3561 		base->so_rcvbuf = buf;
3562 	} else if (str_matches_option(option, "so-sndbuf:")) {
3563 		int buf = strtoint(val);
3564 		if (buf == -1) return -1;
3565 		if (!(flags & DNS_OPTION_MISC)) return 0;
3566 		log(EVDNS_LOG_DEBUG, "Setting SO_SNDBUF to %s", val);
3567 		base->so_sndbuf = buf;
3568 	}
3569 	return 0;
3570 }
3571 
3572 int
3573 evdns_set_option(const char *option, const char *val, int flags)
3574 {
3575 	if (!current_base)
3576 		current_base = evdns_base_new(NULL, 0);
3577 	return evdns_base_set_option(current_base, option, val);
3578 }
3579 
3580 static void
3581 resolv_conf_parse_line(struct evdns_base *base, char *const start, int flags) {
3582 	char *strtok_state;
3583 	static const char *const delims = " \t";
3584 #define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state)
3585 
3586 
3587 	char *const first_token = strtok_r(start, delims, &strtok_state);
3588 	ASSERT_LOCKED(base);
3589 	if (!first_token) return;
3590 
3591 	if (!strcmp(first_token, "nameserver") && (flags & DNS_OPTION_NAMESERVERS)) {
3592 		const char *const nameserver = NEXT_TOKEN;
3593 
3594 		if (nameserver)
3595 			evdns_base_nameserver_ip_add(base, nameserver);
3596 	} else if (!strcmp(first_token, "domain") && (flags & DNS_OPTION_SEARCH)) {
3597 		const char *const domain = NEXT_TOKEN;
3598 		if (domain) {
3599 			search_postfix_clear(base);
3600 			search_postfix_add(base, domain);
3601 		}
3602 	} else if (!strcmp(first_token, "search") && (flags & DNS_OPTION_SEARCH)) {
3603 		const char *domain;
3604 		search_postfix_clear(base);
3605 
3606 		while ((domain = NEXT_TOKEN)) {
3607 			search_postfix_add(base, domain);
3608 		}
3609 		search_reverse(base);
3610 	} else if (!strcmp(first_token, "options")) {
3611 		const char *option;
3612 		while ((option = NEXT_TOKEN)) {
3613 			const char *val = strchr(option, ':');
3614 			evdns_base_set_option_impl(base, option, val ? val+1 : "", flags);
3615 		}
3616 	}
3617 #undef NEXT_TOKEN
3618 }
3619 
3620 /* exported function */
3621 /* returns: */
3622 /*   0 no errors */
3623 /*   1 failed to open file */
3624 /*   2 failed to stat file */
3625 /*   3 file too large */
3626 /*   4 out of memory */
3627 /*   5 short read from file */
3628 int
3629 evdns_base_resolv_conf_parse(struct evdns_base *base, int flags, const char *const filename) {
3630 	int res;
3631 	EVDNS_LOCK(base);
3632 	res = evdns_base_resolv_conf_parse_impl(base, flags, filename);
3633 	EVDNS_UNLOCK(base);
3634 	return res;
3635 }
3636 
3637 static char *
3638 evdns_get_default_hosts_filename(void)
3639 {
3640 #ifdef _WIN32
3641 	/* Windows is a little coy about where it puts its configuration
3642 	 * files.  Sure, they're _usually_ in C:\windows\system32, but
3643 	 * there's no reason in principle they couldn't be in
3644 	 * W:\hoboken chicken emergency\
3645 	 */
3646 	char path[MAX_PATH+1];
3647 	static const char hostfile[] = "\\drivers\\etc\\hosts";
3648 	char *path_out;
3649 	size_t len_out;
3650 
3651 	if (! SHGetSpecialFolderPathA(NULL, path, CSIDL_SYSTEM, 0))
3652 		return NULL;
3653 	len_out = strlen(path)+strlen(hostfile)+1;
3654 	path_out = mm_malloc(len_out);
3655 	evutil_snprintf(path_out, len_out, "%s%s", path, hostfile);
3656 	return path_out;
3657 #else
3658 	return mm_strdup("/etc/hosts");
3659 #endif
3660 }
3661 
3662 static int
3663 evdns_base_resolv_conf_parse_impl(struct evdns_base *base, int flags, const char *const filename) {
3664 	size_t n;
3665 	char *resolv;
3666 	char *start;
3667 	int err = 0;
3668 	int add_default;
3669 
3670 	log(EVDNS_LOG_DEBUG, "Parsing resolv.conf file %s", filename);
3671 
3672 	add_default = flags & DNS_OPTION_NAMESERVERS;
3673 	if (flags & DNS_OPTION_NAMESERVERS_NO_DEFAULT)
3674 		add_default = 0;
3675 
3676 	if (flags & DNS_OPTION_HOSTSFILE) {
3677 		char *fname = evdns_get_default_hosts_filename();
3678 		evdns_base_load_hosts(base, fname);
3679 		if (fname)
3680 			mm_free(fname);
3681 	}
3682 
3683 	if (!filename) {
3684 		evdns_resolv_set_defaults(base, flags);
3685 		return 1;
3686 	}
3687 
3688 	if ((err = evutil_read_file_(filename, &resolv, &n, 0)) < 0) {
3689 		if (err == -1) {
3690 			/* No file. */
3691 			evdns_resolv_set_defaults(base, flags);
3692 			return 1;
3693 		} else {
3694 			return 2;
3695 		}
3696 	}
3697 
3698 	start = resolv;
3699 	for (;;) {
3700 		char *const newline = strchr(start, '\n');
3701 		if (!newline) {
3702 			resolv_conf_parse_line(base, start, flags);
3703 			break;
3704 		} else {
3705 			*newline = 0;
3706 			resolv_conf_parse_line(base, start, flags);
3707 			start = newline + 1;
3708 		}
3709 	}
3710 
3711 	if (!base->server_head && add_default) {
3712 		/* no nameservers were configured. */
3713 		evdns_base_nameserver_ip_add(base, "127.0.0.1");
3714 		err = 6;
3715 	}
3716 	if (flags & DNS_OPTION_SEARCH && (!base->global_search_state || base->global_search_state->num_domains == 0)) {
3717 		search_set_from_hostname(base);
3718 	}
3719 
3720 	mm_free(resolv);
3721 	return err;
3722 }
3723 
3724 int
3725 evdns_resolv_conf_parse(int flags, const char *const filename) {
3726 	if (!current_base)
3727 		current_base = evdns_base_new(NULL, 0);
3728 	return evdns_base_resolv_conf_parse(current_base, flags, filename);
3729 }
3730 
3731 
3732 #ifdef _WIN32
3733 /* Add multiple nameservers from a space-or-comma-separated list. */
3734 static int
3735 evdns_nameserver_ip_add_line(struct evdns_base *base, const char *ips) {
3736 	const char *addr;
3737 	char *buf;
3738 	int r;
3739 	ASSERT_LOCKED(base);
3740 	while (*ips) {
3741 		while (isspace(*ips) || *ips == ',' || *ips == '\t')
3742 			++ips;
3743 		addr = ips;
3744 		while (isdigit(*ips) || *ips == '.' || *ips == ':' ||
3745 		    *ips=='[' || *ips==']')
3746 			++ips;
3747 		buf = mm_malloc(ips-addr+1);
3748 		if (!buf) return 4;
3749 		memcpy(buf, addr, ips-addr);
3750 		buf[ips-addr] = '\0';
3751 		r = evdns_base_nameserver_ip_add(base, buf);
3752 		mm_free(buf);
3753 		if (r) return r;
3754 	}
3755 	return 0;
3756 }
3757 
3758 typedef DWORD(WINAPI *GetNetworkParams_fn_t)(FIXED_INFO *, DWORD*);
3759 
3760 /* Use the windows GetNetworkParams interface in iphlpapi.dll to */
3761 /* figure out what our nameservers are. */
3762 static int
3763 load_nameservers_with_getnetworkparams(struct evdns_base *base)
3764 {
3765 	/* Based on MSDN examples and inspection of  c-ares code. */
3766 	FIXED_INFO *fixed;
3767 	HMODULE handle = 0;
3768 	ULONG size = sizeof(FIXED_INFO);
3769 	void *buf = NULL;
3770 	int status = 0, r, added_any;
3771 	IP_ADDR_STRING *ns;
3772 	GetNetworkParams_fn_t fn;
3773 
3774 	ASSERT_LOCKED(base);
3775 	if (!(handle = evutil_load_windows_system_library_(
3776 			TEXT("iphlpapi.dll")))) {
3777 		log(EVDNS_LOG_WARN, "Could not open iphlpapi.dll");
3778 		status = -1;
3779 		goto done;
3780 	}
3781 	if (!(fn = (GetNetworkParams_fn_t) GetProcAddress(handle, "GetNetworkParams"))) {
3782 		log(EVDNS_LOG_WARN, "Could not get address of function.");
3783 		status = -1;
3784 		goto done;
3785 	}
3786 
3787 	buf = mm_malloc(size);
3788 	if (!buf) { status = 4; goto done; }
3789 	fixed = buf;
3790 	r = fn(fixed, &size);
3791 	if (r != ERROR_SUCCESS && r != ERROR_BUFFER_OVERFLOW) {
3792 		status = -1;
3793 		goto done;
3794 	}
3795 	if (r != ERROR_SUCCESS) {
3796 		mm_free(buf);
3797 		buf = mm_malloc(size);
3798 		if (!buf) { status = 4; goto done; }
3799 		fixed = buf;
3800 		r = fn(fixed, &size);
3801 		if (r != ERROR_SUCCESS) {
3802 			log(EVDNS_LOG_DEBUG, "fn() failed.");
3803 			status = -1;
3804 			goto done;
3805 		}
3806 	}
3807 
3808 	EVUTIL_ASSERT(fixed);
3809 	added_any = 0;
3810 	ns = &(fixed->DnsServerList);
3811 	while (ns) {
3812 		r = evdns_nameserver_ip_add_line(base, ns->IpAddress.String);
3813 		if (r) {
3814 			log(EVDNS_LOG_DEBUG,"Could not add nameserver %s to list,error: %d",
3815 				(ns->IpAddress.String),(int)GetLastError());
3816 			status = r;
3817 		} else {
3818 			++added_any;
3819 			log(EVDNS_LOG_DEBUG,"Successfully added %s as nameserver",ns->IpAddress.String);
3820 		}
3821 
3822 		ns = ns->Next;
3823 	}
3824 
3825 	if (!added_any) {
3826 		log(EVDNS_LOG_DEBUG, "No nameservers added.");
3827 		if (status == 0)
3828 			status = -1;
3829 	} else {
3830 		status = 0;
3831 	}
3832 
3833  done:
3834 	if (buf)
3835 		mm_free(buf);
3836 	if (handle)
3837 		FreeLibrary(handle);
3838 	return status;
3839 }
3840 
3841 static int
3842 config_nameserver_from_reg_key(struct evdns_base *base, HKEY key, const TCHAR *subkey)
3843 {
3844 	char *buf;
3845 	DWORD bufsz = 0, type = 0;
3846 	int status = 0;
3847 
3848 	ASSERT_LOCKED(base);
3849 	if (RegQueryValueEx(key, subkey, 0, &type, NULL, &bufsz)
3850 	    != ERROR_MORE_DATA)
3851 		return -1;
3852 	if (!(buf = mm_malloc(bufsz)))
3853 		return -1;
3854 
3855 	if (RegQueryValueEx(key, subkey, 0, &type, (LPBYTE)buf, &bufsz)
3856 	    == ERROR_SUCCESS && bufsz > 1) {
3857 		status = evdns_nameserver_ip_add_line(base,buf);
3858 	}
3859 
3860 	mm_free(buf);
3861 	return status;
3862 }
3863 
3864 #define SERVICES_KEY TEXT("System\\CurrentControlSet\\Services\\")
3865 #define WIN_NS_9X_KEY  SERVICES_KEY TEXT("VxD\\MSTCP")
3866 #define WIN_NS_NT_KEY  SERVICES_KEY TEXT("Tcpip\\Parameters")
3867 
3868 static int
3869 load_nameservers_from_registry(struct evdns_base *base)
3870 {
3871 	int found = 0;
3872 	int r;
3873 #define TRY(k, name) \
3874 	if (!found && config_nameserver_from_reg_key(base,k,TEXT(name)) == 0) { \
3875 		log(EVDNS_LOG_DEBUG,"Found nameservers in %s/%s",#k,name); \
3876 		found = 1;						\
3877 	} else if (!found) {						\
3878 		log(EVDNS_LOG_DEBUG,"Didn't find nameservers in %s/%s", \
3879 		    #k,#name);						\
3880 	}
3881 
3882 	ASSERT_LOCKED(base);
3883 
3884 	if (((int)GetVersion()) > 0) { /* NT */
3885 		HKEY nt_key = 0, interfaces_key = 0;
3886 
3887 		if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0,
3888 				 KEY_READ, &nt_key) != ERROR_SUCCESS) {
3889 			log(EVDNS_LOG_DEBUG,"Couldn't open nt key, %d",(int)GetLastError());
3890 			return -1;
3891 		}
3892 		r = RegOpenKeyEx(nt_key, TEXT("Interfaces"), 0,
3893 			     KEY_QUERY_VALUE|KEY_ENUMERATE_SUB_KEYS,
3894 			     &interfaces_key);
3895 		if (r != ERROR_SUCCESS) {
3896 			log(EVDNS_LOG_DEBUG,"Couldn't open interfaces key, %d",(int)GetLastError());
3897 			return -1;
3898 		}
3899 		TRY(nt_key, "NameServer");
3900 		TRY(nt_key, "DhcpNameServer");
3901 		TRY(interfaces_key, "NameServer");
3902 		TRY(interfaces_key, "DhcpNameServer");
3903 		RegCloseKey(interfaces_key);
3904 		RegCloseKey(nt_key);
3905 	} else {
3906 		HKEY win_key = 0;
3907 		if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_9X_KEY, 0,
3908 				 KEY_READ, &win_key) != ERROR_SUCCESS) {
3909 			log(EVDNS_LOG_DEBUG, "Couldn't open registry key, %d", (int)GetLastError());
3910 			return -1;
3911 		}
3912 		TRY(win_key, "NameServer");
3913 		RegCloseKey(win_key);
3914 	}
3915 
3916 	if (found == 0) {
3917 		log(EVDNS_LOG_WARN,"Didn't find any nameservers.");
3918 	}
3919 
3920 	return found ? 0 : -1;
3921 #undef TRY
3922 }
3923 
3924 int
3925 evdns_base_config_windows_nameservers(struct evdns_base *base)
3926 {
3927 	int r;
3928 	char *fname;
3929 	if (base == NULL)
3930 		base = current_base;
3931 	if (base == NULL)
3932 		return -1;
3933 	EVDNS_LOCK(base);
3934 	fname = evdns_get_default_hosts_filename();
3935 	log(EVDNS_LOG_DEBUG, "Loading hosts entries from %s", fname);
3936 	evdns_base_load_hosts(base, fname);
3937 	if (fname)
3938 		mm_free(fname);
3939 
3940 	if (load_nameservers_with_getnetworkparams(base) == 0) {
3941 		EVDNS_UNLOCK(base);
3942 		return 0;
3943 	}
3944 	r = load_nameservers_from_registry(base);
3945 
3946 	EVDNS_UNLOCK(base);
3947 	return r;
3948 }
3949 
3950 int
3951 evdns_config_windows_nameservers(void)
3952 {
3953 	if (!current_base) {
3954 		current_base = evdns_base_new(NULL, 1);
3955 		return current_base == NULL ? -1 : 0;
3956 	} else {
3957 		return evdns_base_config_windows_nameservers(current_base);
3958 	}
3959 }
3960 #endif
3961 
3962 struct evdns_base *
3963 evdns_base_new(struct event_base *event_base, int flags)
3964 {
3965 	struct evdns_base *base;
3966 
3967 	if (evutil_secure_rng_init() < 0) {
3968 		log(EVDNS_LOG_WARN, "Unable to seed random number generator; "
3969 		    "DNS can't run.");
3970 		return NULL;
3971 	}
3972 
3973 	/* Give the evutil library a hook into its evdns-enabled
3974 	 * functionality.  We can't just call evdns_getaddrinfo directly or
3975 	 * else libevent-core will depend on libevent-extras. */
3976 	evutil_set_evdns_getaddrinfo_fn_(evdns_getaddrinfo);
3977 	evutil_set_evdns_getaddrinfo_cancel_fn_(evdns_getaddrinfo_cancel);
3978 
3979 	base = mm_malloc(sizeof(struct evdns_base));
3980 	if (base == NULL)
3981 		return (NULL);
3982 	memset(base, 0, sizeof(struct evdns_base));
3983 	base->req_waiting_head = NULL;
3984 
3985 	EVTHREAD_ALLOC_LOCK(base->lock, EVTHREAD_LOCKTYPE_RECURSIVE);
3986 	EVDNS_LOCK(base);
3987 
3988 	/* Set max requests inflight and allocate req_heads. */
3989 	base->req_heads = NULL;
3990 
3991 	evdns_base_set_max_requests_inflight(base, 64);
3992 
3993 	base->server_head = NULL;
3994 	base->event_base = event_base;
3995 	base->global_good_nameservers = base->global_requests_inflight =
3996 		base->global_requests_waiting = 0;
3997 
3998 	base->global_timeout.tv_sec = 5;
3999 	base->global_timeout.tv_usec = 0;
4000 	base->global_max_reissues = 1;
4001 	base->global_max_retransmits = 3;
4002 	base->global_max_nameserver_timeout = 3;
4003 	base->global_search_state = NULL;
4004 	base->global_randomize_case = 1;
4005 	base->global_getaddrinfo_allow_skew.tv_sec = 3;
4006 	base->global_getaddrinfo_allow_skew.tv_usec = 0;
4007 	base->global_nameserver_probe_initial_timeout.tv_sec = 10;
4008 	base->global_nameserver_probe_initial_timeout.tv_usec = 0;
4009 
4010 	TAILQ_INIT(&base->hostsdb);
4011 
4012 #define EVDNS_BASE_ALL_FLAGS ( \
4013 	EVDNS_BASE_INITIALIZE_NAMESERVERS | \
4014 	EVDNS_BASE_DISABLE_WHEN_INACTIVE  | \
4015 	EVDNS_BASE_NAMESERVERS_NO_DEFAULT | \
4016 	0)
4017 
4018 	if (flags & ~EVDNS_BASE_ALL_FLAGS) {
4019 		flags = EVDNS_BASE_INITIALIZE_NAMESERVERS;
4020 		log(EVDNS_LOG_WARN,
4021 		    "Unrecognized flag passed to evdns_base_new(). Assuming "
4022 		    "you meant EVDNS_BASE_INITIALIZE_NAMESERVERS.");
4023 	}
4024 #undef EVDNS_BASE_ALL_FLAGS
4025 
4026 	if (flags & EVDNS_BASE_INITIALIZE_NAMESERVERS) {
4027 		int r;
4028 		int opts = DNS_OPTIONS_ALL;
4029 		if (flags & EVDNS_BASE_NAMESERVERS_NO_DEFAULT) {
4030 			opts |= DNS_OPTION_NAMESERVERS_NO_DEFAULT;
4031 		}
4032 
4033 #ifdef _WIN32
4034 		r = evdns_base_config_windows_nameservers(base);
4035 #else
4036 		r = evdns_base_resolv_conf_parse(base, opts, "/etc/resolv.conf");
4037 #endif
4038 		if (r) {
4039 			evdns_base_free_and_unlock(base, 0);
4040 			return NULL;
4041 		}
4042 	}
4043 	if (flags & EVDNS_BASE_DISABLE_WHEN_INACTIVE) {
4044 		base->disable_when_inactive = 1;
4045 	}
4046 
4047 	EVDNS_UNLOCK(base);
4048 	return base;
4049 }
4050 
4051 int
4052 evdns_init(void)
4053 {
4054 	struct evdns_base *base = evdns_base_new(NULL, 1);
4055 	if (base) {
4056 		current_base = base;
4057 		return 0;
4058 	} else {
4059 		return -1;
4060 	}
4061 }
4062 
4063 const char *
4064 evdns_err_to_string(int err)
4065 {
4066     switch (err) {
4067 	case DNS_ERR_NONE: return "no error";
4068 	case DNS_ERR_FORMAT: return "misformatted query";
4069 	case DNS_ERR_SERVERFAILED: return "server failed";
4070 	case DNS_ERR_NOTEXIST: return "name does not exist";
4071 	case DNS_ERR_NOTIMPL: return "query not implemented";
4072 	case DNS_ERR_REFUSED: return "refused";
4073 
4074 	case DNS_ERR_TRUNCATED: return "reply truncated or ill-formed";
4075 	case DNS_ERR_UNKNOWN: return "unknown";
4076 	case DNS_ERR_TIMEOUT: return "request timed out";
4077 	case DNS_ERR_SHUTDOWN: return "dns subsystem shut down";
4078 	case DNS_ERR_CANCEL: return "dns request canceled";
4079 	case DNS_ERR_NODATA: return "no records in the reply";
4080 	default: return "[Unknown error code]";
4081     }
4082 }
4083 
4084 static void
4085 evdns_nameserver_free(struct nameserver *server)
4086 {
4087 	if (server->socket >= 0)
4088 		evutil_closesocket(server->socket);
4089 	(void) event_del(&server->event);
4090 	event_debug_unassign(&server->event);
4091 	if (server->state == 0)
4092 		(void) event_del(&server->timeout_event);
4093 	if (server->probe_request) {
4094 		evdns_cancel_request(server->base, server->probe_request);
4095 		server->probe_request = NULL;
4096 	}
4097 	event_debug_unassign(&server->timeout_event);
4098 	mm_free(server);
4099 }
4100 
4101 static void
4102 evdns_base_free_and_unlock(struct evdns_base *base, int fail_requests)
4103 {
4104 	struct nameserver *server, *server_next;
4105 	struct search_domain *dom, *dom_next;
4106 	int i;
4107 
4108 	/* Requires that we hold the lock. */
4109 
4110 	/* TODO(nickm) we might need to refcount here. */
4111 
4112 	while (base->req_waiting_head) {
4113 		if (fail_requests)
4114 			reply_schedule_callback(base->req_waiting_head, 0, DNS_ERR_SHUTDOWN, NULL);
4115 		request_finished(base->req_waiting_head, &base->req_waiting_head, 1);
4116 	}
4117 	for (i = 0; i < base->n_req_heads; ++i) {
4118 		while (base->req_heads[i]) {
4119 			if (fail_requests)
4120 				reply_schedule_callback(base->req_heads[i], 0, DNS_ERR_SHUTDOWN, NULL);
4121 			request_finished(base->req_heads[i], &REQ_HEAD(base, base->req_heads[i]->trans_id), 1);
4122 		}
4123 	}
4124 	base->global_requests_inflight = base->global_requests_waiting = 0;
4125 
4126 	for (server = base->server_head; server; server = server_next) {
4127 		server_next = server->next;
4128 		/** already done something before */
4129 		server->probe_request = NULL;
4130 		evdns_nameserver_free(server);
4131 		if (server_next == base->server_head)
4132 			break;
4133 	}
4134 	base->server_head = NULL;
4135 	base->global_good_nameservers = 0;
4136 
4137 	if (base->global_search_state) {
4138 		for (dom = base->global_search_state->head; dom; dom = dom_next) {
4139 			dom_next = dom->next;
4140 			mm_free(dom);
4141 		}
4142 		mm_free(base->global_search_state);
4143 		base->global_search_state = NULL;
4144 	}
4145 
4146 	{
4147 		struct hosts_entry *victim;
4148 		while ((victim = TAILQ_FIRST(&base->hostsdb))) {
4149 			TAILQ_REMOVE(&base->hostsdb, victim, next);
4150 			mm_free(victim);
4151 		}
4152 	}
4153 
4154 	mm_free(base->req_heads);
4155 
4156 	EVDNS_UNLOCK(base);
4157 	EVTHREAD_FREE_LOCK(base->lock, EVTHREAD_LOCKTYPE_RECURSIVE);
4158 
4159 	mm_free(base);
4160 }
4161 
4162 void
4163 evdns_base_free(struct evdns_base *base, int fail_requests)
4164 {
4165 	EVDNS_LOCK(base);
4166 	evdns_base_free_and_unlock(base, fail_requests);
4167 }
4168 
4169 void
4170 evdns_base_clear_host_addresses(struct evdns_base *base)
4171 {
4172 	struct hosts_entry *victim;
4173 	EVDNS_LOCK(base);
4174 	while ((victim = TAILQ_FIRST(&base->hostsdb))) {
4175 		TAILQ_REMOVE(&base->hostsdb, victim, next);
4176 		mm_free(victim);
4177 	}
4178 	EVDNS_UNLOCK(base);
4179 }
4180 
4181 void
4182 evdns_shutdown(int fail_requests)
4183 {
4184 	if (current_base) {
4185 		struct evdns_base *b = current_base;
4186 		current_base = NULL;
4187 		evdns_base_free(b, fail_requests);
4188 	}
4189 	evdns_log_fn = NULL;
4190 }
4191 
4192 static int
4193 evdns_base_parse_hosts_line(struct evdns_base *base, char *line)
4194 {
4195 	char *strtok_state;
4196 	static const char *const delims = " \t";
4197 	char *const addr = strtok_r(line, delims, &strtok_state);
4198 	char *hostname, *hash;
4199 	struct sockaddr_storage ss;
4200 	int socklen = sizeof(ss);
4201 	ASSERT_LOCKED(base);
4202 
4203 #define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state)
4204 
4205 	if (!addr || *addr == '#')
4206 		return 0;
4207 
4208 	memset(&ss, 0, sizeof(ss));
4209 	if (evutil_parse_sockaddr_port(addr, (struct sockaddr*)&ss, &socklen)<0)
4210 		return -1;
4211 	if (socklen > (int)sizeof(struct sockaddr_in6))
4212 		return -1;
4213 
4214 	if (sockaddr_getport((struct sockaddr*)&ss))
4215 		return -1;
4216 
4217 	while ((hostname = NEXT_TOKEN)) {
4218 		struct hosts_entry *he;
4219 		size_t namelen;
4220 		if ((hash = strchr(hostname, '#'))) {
4221 			if (hash == hostname)
4222 				return 0;
4223 			*hash = '\0';
4224 		}
4225 
4226 		namelen = strlen(hostname);
4227 
4228 		he = mm_calloc(1, sizeof(struct hosts_entry)+namelen);
4229 		if (!he)
4230 			return -1;
4231 		EVUTIL_ASSERT(socklen <= (int)sizeof(he->addr));
4232 		memcpy(&he->addr, &ss, socklen);
4233 		memcpy(he->hostname, hostname, namelen+1);
4234 		he->addrlen = socklen;
4235 
4236 		TAILQ_INSERT_TAIL(&base->hostsdb, he, next);
4237 
4238 		if (hash)
4239 			return 0;
4240 	}
4241 
4242 	return 0;
4243 #undef NEXT_TOKEN
4244 }
4245 
4246 static int
4247 evdns_base_load_hosts_impl(struct evdns_base *base, const char *hosts_fname)
4248 {
4249 	char *str=NULL, *cp, *eol;
4250 	size_t len;
4251 	int err=0;
4252 
4253 	ASSERT_LOCKED(base);
4254 
4255 	if (hosts_fname == NULL ||
4256 	    (err = evutil_read_file_(hosts_fname, &str, &len, 0)) < 0) {
4257 		char tmp[64];
4258 		strlcpy(tmp, "127.0.0.1   localhost", sizeof(tmp));
4259 		evdns_base_parse_hosts_line(base, tmp);
4260 		strlcpy(tmp, "::1   localhost", sizeof(tmp));
4261 		evdns_base_parse_hosts_line(base, tmp);
4262 		return err ? -1 : 0;
4263 	}
4264 
4265 	/* This will break early if there is a NUL in the hosts file.
4266 	 * Probably not a problem.*/
4267 	cp = str;
4268 	for (;;) {
4269 		eol = strchr(cp, '\n');
4270 
4271 		if (eol) {
4272 			*eol = '\0';
4273 			evdns_base_parse_hosts_line(base, cp);
4274 			cp = eol+1;
4275 		} else {
4276 			evdns_base_parse_hosts_line(base, cp);
4277 			break;
4278 		}
4279 	}
4280 
4281 	mm_free(str);
4282 	return 0;
4283 }
4284 
4285 int
4286 evdns_base_load_hosts(struct evdns_base *base, const char *hosts_fname)
4287 {
4288 	int res;
4289 	if (!base)
4290 		base = current_base;
4291 	EVDNS_LOCK(base);
4292 	res = evdns_base_load_hosts_impl(base, hosts_fname);
4293 	EVDNS_UNLOCK(base);
4294 	return res;
4295 }
4296 
4297 /* A single request for a getaddrinfo, either v4 or v6. */
4298 struct getaddrinfo_subrequest {
4299 	struct evdns_request *r;
4300 	ev_uint32_t type;
4301 };
4302 
4303 /* State data used to implement an in-progress getaddrinfo. */
4304 struct evdns_getaddrinfo_request {
4305 	struct evdns_base *evdns_base;
4306 	/* Copy of the modified 'hints' data that we'll use to build
4307 	 * answers. */
4308 	struct evutil_addrinfo hints;
4309 	/* The callback to invoke when we're done */
4310 	evdns_getaddrinfo_cb user_cb;
4311 	/* User-supplied data to give to the callback. */
4312 	void *user_data;
4313 	/* The port to use when building sockaddrs. */
4314 	ev_uint16_t port;
4315 	/* The sub_request for an A record (if any) */
4316 	struct getaddrinfo_subrequest ipv4_request;
4317 	/* The sub_request for an AAAA record (if any) */
4318 	struct getaddrinfo_subrequest ipv6_request;
4319 
4320 	/* The cname result that we were told (if any) */
4321 	char *cname_result;
4322 
4323 	/* If we have one request answered and one request still inflight,
4324 	 * then this field holds the answer from the first request... */
4325 	struct evutil_addrinfo *pending_result;
4326 	/* And this event is a timeout that will tell us to cancel the second
4327 	 * request if it's taking a long time. */
4328 	struct event timeout;
4329 
4330 	/* And this field holds the error code from the first request... */
4331 	int pending_error;
4332 	/* If this is set, the user canceled this request. */
4333 	unsigned user_canceled : 1;
4334 	/* If this is set, the user can no longer cancel this request; we're
4335 	 * just waiting for the free. */
4336 	unsigned request_done : 1;
4337 };
4338 
4339 /* Convert an evdns errors to the equivalent getaddrinfo error. */
4340 static int
4341 evdns_err_to_getaddrinfo_err(int e1)
4342 {
4343 	/* XXX Do this better! */
4344 	if (e1 == DNS_ERR_NONE)
4345 		return 0;
4346 	else if (e1 == DNS_ERR_NOTEXIST)
4347 		return EVUTIL_EAI_NONAME;
4348 	else
4349 		return EVUTIL_EAI_FAIL;
4350 }
4351 
4352 /* Return the more informative of two getaddrinfo errors. */
4353 static int
4354 getaddrinfo_merge_err(int e1, int e2)
4355 {
4356 	/* XXXX be cleverer here. */
4357 	if (e1 == 0)
4358 		return e2;
4359 	else
4360 		return e1;
4361 }
4362 
4363 static void
4364 free_getaddrinfo_request(struct evdns_getaddrinfo_request *data)
4365 {
4366 	/* DO NOT CALL this if either of the requests is pending.  Only once
4367 	 * both callbacks have been invoked is it safe to free the request */
4368 	if (data->pending_result)
4369 		evutil_freeaddrinfo(data->pending_result);
4370 	if (data->cname_result)
4371 		mm_free(data->cname_result);
4372 	event_del(&data->timeout);
4373 	mm_free(data);
4374 	return;
4375 }
4376 
4377 static void
4378 add_cname_to_reply(struct evdns_getaddrinfo_request *data,
4379     struct evutil_addrinfo *ai)
4380 {
4381 	if (data->cname_result && ai) {
4382 		ai->ai_canonname = data->cname_result;
4383 		data->cname_result = NULL;
4384 	}
4385 }
4386 
4387 /* Callback: invoked when one request in a mixed-format A/AAAA getaddrinfo
4388  * request has finished, but the other one took too long to answer. Pass
4389  * along the answer we got, and cancel the other request.
4390  */
4391 static void
4392 evdns_getaddrinfo_timeout_cb(evutil_socket_t fd, short what, void *ptr)
4393 {
4394 	int v4_timedout = 0, v6_timedout = 0;
4395 	struct evdns_getaddrinfo_request *data = ptr;
4396 
4397 	/* Cancel any pending requests, and note which one */
4398 	if (data->ipv4_request.r) {
4399 		/* XXXX This does nothing if the request's callback is already
4400 		 * running (pending_cb is set). */
4401 		evdns_cancel_request(NULL, data->ipv4_request.r);
4402 		v4_timedout = 1;
4403 		EVDNS_LOCK(data->evdns_base);
4404 		++data->evdns_base->getaddrinfo_ipv4_timeouts;
4405 		EVDNS_UNLOCK(data->evdns_base);
4406 	}
4407 	if (data->ipv6_request.r) {
4408 		/* XXXX This does nothing if the request's callback is already
4409 		 * running (pending_cb is set). */
4410 		evdns_cancel_request(NULL, data->ipv6_request.r);
4411 		v6_timedout = 1;
4412 		EVDNS_LOCK(data->evdns_base);
4413 		++data->evdns_base->getaddrinfo_ipv6_timeouts;
4414 		EVDNS_UNLOCK(data->evdns_base);
4415 	}
4416 
4417 	/* We only use this timeout callback when we have an answer for
4418 	 * one address. */
4419 	EVUTIL_ASSERT(!v4_timedout || !v6_timedout);
4420 
4421 	/* Report the outcome of the other request that didn't time out. */
4422 	if (data->pending_result) {
4423 		add_cname_to_reply(data, data->pending_result);
4424 		data->user_cb(0, data->pending_result, data->user_data);
4425 		data->pending_result = NULL;
4426 	} else {
4427 		int e = data->pending_error;
4428 		if (!e)
4429 			e = EVUTIL_EAI_AGAIN;
4430 		data->user_cb(e, NULL, data->user_data);
4431 	}
4432 
4433 	data->user_cb = NULL; /* prevent double-call if evdns callbacks are
4434 			       * in-progress. XXXX It would be better if this
4435 			       * weren't necessary. */
4436 
4437 	if (!v4_timedout && !v6_timedout) {
4438 		/* should be impossible? XXXX */
4439 		free_getaddrinfo_request(data);
4440 	}
4441 }
4442 
4443 static int
4444 evdns_getaddrinfo_set_timeout(struct evdns_base *evdns_base,
4445     struct evdns_getaddrinfo_request *data)
4446 {
4447 	return event_add(&data->timeout, &evdns_base->global_getaddrinfo_allow_skew);
4448 }
4449 
4450 static inline int
4451 evdns_result_is_answer(int result)
4452 {
4453 	return (result != DNS_ERR_NOTIMPL && result != DNS_ERR_REFUSED &&
4454 	    result != DNS_ERR_SERVERFAILED && result != DNS_ERR_CANCEL);
4455 }
4456 
4457 static void
4458 evdns_getaddrinfo_gotresolve(int result, char type, int count,
4459     int ttl, void *addresses, void *arg)
4460 {
4461 	int i;
4462 	struct getaddrinfo_subrequest *req = arg;
4463 	struct getaddrinfo_subrequest *other_req;
4464 	struct evdns_getaddrinfo_request *data;
4465 
4466 	struct evutil_addrinfo *res;
4467 
4468 	struct sockaddr_in sin;
4469 	struct sockaddr_in6 sin6;
4470 	struct sockaddr *sa;
4471 	int socklen, addrlen;
4472 	void *addrp;
4473 	int err;
4474 	int user_canceled;
4475 
4476 	EVUTIL_ASSERT(req->type == DNS_IPv4_A || req->type == DNS_IPv6_AAAA);
4477 	if (req->type == DNS_IPv4_A) {
4478 		data = EVUTIL_UPCAST(req, struct evdns_getaddrinfo_request, ipv4_request);
4479 		other_req = &data->ipv6_request;
4480 	} else {
4481 		data = EVUTIL_UPCAST(req, struct evdns_getaddrinfo_request, ipv6_request);
4482 		other_req = &data->ipv4_request;
4483 	}
4484 
4485 	/** Called from evdns_base_free() with @fail_requests == 1 */
4486 	if (result != DNS_ERR_SHUTDOWN) {
4487 		EVDNS_LOCK(data->evdns_base);
4488 		if (evdns_result_is_answer(result)) {
4489 			if (req->type == DNS_IPv4_A)
4490 				++data->evdns_base->getaddrinfo_ipv4_answered;
4491 			else
4492 				++data->evdns_base->getaddrinfo_ipv6_answered;
4493 		}
4494 		user_canceled = data->user_canceled;
4495 		if (other_req->r == NULL)
4496 			data->request_done = 1;
4497 		EVDNS_UNLOCK(data->evdns_base);
4498 	} else {
4499 		data->evdns_base = NULL;
4500 		user_canceled = data->user_canceled;
4501 	}
4502 
4503 	req->r = NULL;
4504 
4505 	if (result == DNS_ERR_CANCEL && ! user_canceled) {
4506 		/* Internal cancel request from timeout or internal error.
4507 		 * we already answered the user. */
4508 		if (other_req->r == NULL)
4509 			free_getaddrinfo_request(data);
4510 		return;
4511 	}
4512 
4513 	if (data->user_cb == NULL) {
4514 		/* We already answered.  XXXX This shouldn't be needed; see
4515 		 * comments in evdns_getaddrinfo_timeout_cb */
4516 		free_getaddrinfo_request(data);
4517 		return;
4518 	}
4519 
4520 	if (result == DNS_ERR_NONE) {
4521 		if (count == 0)
4522 			err = EVUTIL_EAI_NODATA;
4523 		else
4524 			err = 0;
4525 	} else {
4526 		err = evdns_err_to_getaddrinfo_err(result);
4527 	}
4528 
4529 	if (err) {
4530 		/* Looks like we got an error. */
4531 		if (other_req->r) {
4532 			/* The other request is still working; maybe it will
4533 			 * succeed. */
4534 			/* XXXX handle failure from set_timeout */
4535 			if (result != DNS_ERR_SHUTDOWN) {
4536 				evdns_getaddrinfo_set_timeout(data->evdns_base, data);
4537 			}
4538 			data->pending_error = err;
4539 			return;
4540 		}
4541 
4542 		if (user_canceled) {
4543 			data->user_cb(EVUTIL_EAI_CANCEL, NULL, data->user_data);
4544 		} else if (data->pending_result) {
4545 			/* If we have an answer waiting, and we weren't
4546 			 * canceled, ignore this error. */
4547 			add_cname_to_reply(data, data->pending_result);
4548 			data->user_cb(0, data->pending_result, data->user_data);
4549 			data->pending_result = NULL;
4550 		} else {
4551 			if (data->pending_error)
4552 				err = getaddrinfo_merge_err(err,
4553 				    data->pending_error);
4554 			data->user_cb(err, NULL, data->user_data);
4555 		}
4556 		free_getaddrinfo_request(data);
4557 		return;
4558 	} else if (user_canceled) {
4559 		if (other_req->r) {
4560 			/* The other request is still working; let it hit this
4561 			 * callback with EVUTIL_EAI_CANCEL callback and report
4562 			 * the failure. */
4563 			return;
4564 		}
4565 		data->user_cb(EVUTIL_EAI_CANCEL, NULL, data->user_data);
4566 		free_getaddrinfo_request(data);
4567 		return;
4568 	}
4569 
4570 	/* Looks like we got some answers. We should turn them into addrinfos
4571 	 * and then either queue those or return them all. */
4572 	EVUTIL_ASSERT(type == DNS_IPv4_A || type == DNS_IPv6_AAAA);
4573 
4574 	if (type == DNS_IPv4_A) {
4575 		memset(&sin, 0, sizeof(sin));
4576 		sin.sin_family = AF_INET;
4577 		sin.sin_port = htons(data->port);
4578 
4579 		sa = (struct sockaddr *)&sin;
4580 		socklen = sizeof(sin);
4581 		addrlen = 4;
4582 		addrp = &sin.sin_addr.s_addr;
4583 	} else {
4584 		memset(&sin6, 0, sizeof(sin6));
4585 		sin6.sin6_family = AF_INET6;
4586 		sin6.sin6_port = htons(data->port);
4587 
4588 		sa = (struct sockaddr *)&sin6;
4589 		socklen = sizeof(sin6);
4590 		addrlen = 16;
4591 		addrp = &sin6.sin6_addr.s6_addr;
4592 	}
4593 
4594 	res = NULL;
4595 	for (i=0; i < count; ++i) {
4596 		struct evutil_addrinfo *ai;
4597 		memcpy(addrp, ((char*)addresses)+i*addrlen, addrlen);
4598 		ai = evutil_new_addrinfo_(sa, socklen, &data->hints);
4599 		if (!ai) {
4600 			if (other_req->r) {
4601 				evdns_cancel_request(NULL, other_req->r);
4602 			}
4603 			data->user_cb(EVUTIL_EAI_MEMORY, NULL, data->user_data);
4604 			if (res)
4605 				evutil_freeaddrinfo(res);
4606 
4607 			if (other_req->r == NULL)
4608 				free_getaddrinfo_request(data);
4609 			return;
4610 		}
4611 		res = evutil_addrinfo_append_(res, ai);
4612 	}
4613 
4614 	if (other_req->r) {
4615 		/* The other request is still in progress; wait for it */
4616 		/* XXXX handle failure from set_timeout */
4617 		evdns_getaddrinfo_set_timeout(data->evdns_base, data);
4618 		data->pending_result = res;
4619 		return;
4620 	} else {
4621 		/* The other request is done or never started; append its
4622 		 * results (if any) and return them. */
4623 		if (data->pending_result) {
4624 			if (req->type == DNS_IPv4_A)
4625 				res = evutil_addrinfo_append_(res,
4626 				    data->pending_result);
4627 			else
4628 				res = evutil_addrinfo_append_(
4629 				    data->pending_result, res);
4630 			data->pending_result = NULL;
4631 		}
4632 
4633 		/* Call the user callback. */
4634 		add_cname_to_reply(data, res);
4635 		data->user_cb(0, res, data->user_data);
4636 
4637 		/* Free data. */
4638 		free_getaddrinfo_request(data);
4639 	}
4640 }
4641 
4642 static struct hosts_entry *
4643 find_hosts_entry(struct evdns_base *base, const char *hostname,
4644     struct hosts_entry *find_after)
4645 {
4646 	struct hosts_entry *e;
4647 
4648 	if (find_after)
4649 		e = TAILQ_NEXT(find_after, next);
4650 	else
4651 		e = TAILQ_FIRST(&base->hostsdb);
4652 
4653 	for (; e; e = TAILQ_NEXT(e, next)) {
4654 		if (!evutil_ascii_strcasecmp(e->hostname, hostname))
4655 			return e;
4656 	}
4657 	return NULL;
4658 }
4659 
4660 static int
4661 evdns_getaddrinfo_fromhosts(struct evdns_base *base,
4662     const char *nodename, struct evutil_addrinfo *hints, ev_uint16_t port,
4663     struct evutil_addrinfo **res)
4664 {
4665 	int n_found = 0;
4666 	struct hosts_entry *e;
4667 	struct evutil_addrinfo *ai=NULL;
4668 	int f = hints->ai_family;
4669 
4670 	EVDNS_LOCK(base);
4671 	for (e = find_hosts_entry(base, nodename, NULL); e;
4672 	    e = find_hosts_entry(base, nodename, e)) {
4673 		struct evutil_addrinfo *ai_new;
4674 		++n_found;
4675 		if ((e->addr.sa.sa_family == AF_INET && f == PF_INET6) ||
4676 		    (e->addr.sa.sa_family == AF_INET6 && f == PF_INET))
4677 			continue;
4678 		ai_new = evutil_new_addrinfo_(&e->addr.sa, e->addrlen, hints);
4679 		if (!ai_new) {
4680 			n_found = 0;
4681 			goto out;
4682 		}
4683 		sockaddr_setport(ai_new->ai_addr, port);
4684 		ai = evutil_addrinfo_append_(ai, ai_new);
4685 	}
4686 	EVDNS_UNLOCK(base);
4687 out:
4688 	if (n_found) {
4689 		/* Note that we return an empty answer if we found entries for
4690 		 * this hostname but none were of the right address type. */
4691 		*res = ai;
4692 		return 0;
4693 	} else {
4694 		if (ai)
4695 			evutil_freeaddrinfo(ai);
4696 		return -1;
4697 	}
4698 }
4699 
4700 struct evdns_getaddrinfo_request *
4701 evdns_getaddrinfo(struct evdns_base *dns_base,
4702     const char *nodename, const char *servname,
4703     const struct evutil_addrinfo *hints_in,
4704     evdns_getaddrinfo_cb cb, void *arg)
4705 {
4706 	struct evdns_getaddrinfo_request *data;
4707 	struct evutil_addrinfo hints;
4708 	struct evutil_addrinfo *res = NULL;
4709 	int err;
4710 	int port = 0;
4711 	int want_cname = 0;
4712 	int started = 0;
4713 
4714 	if (!dns_base) {
4715 		dns_base = current_base;
4716 		if (!dns_base) {
4717 			log(EVDNS_LOG_WARN,
4718 			    "Call to getaddrinfo_async with no "
4719 			    "evdns_base configured.");
4720 			cb(EVUTIL_EAI_FAIL, NULL, arg); /* ??? better error? */
4721 			return NULL;
4722 		}
4723 	}
4724 
4725 	/* If we _must_ answer this immediately, do so. */
4726 	if ((hints_in && (hints_in->ai_flags & EVUTIL_AI_NUMERICHOST))) {
4727 		res = NULL;
4728 		err = evutil_getaddrinfo(nodename, servname, hints_in, &res);
4729 		cb(err, res, arg);
4730 		return NULL;
4731 	}
4732 
4733 	if (hints_in) {
4734 		memcpy(&hints, hints_in, sizeof(hints));
4735 	} else {
4736 		memset(&hints, 0, sizeof(hints));
4737 		hints.ai_family = PF_UNSPEC;
4738 	}
4739 
4740 	evutil_adjust_hints_for_addrconfig_(&hints);
4741 
4742 	/* Now try to see if we _can_ answer immediately. */
4743 	/* (It would be nice to do this by calling getaddrinfo directly, with
4744 	 * AI_NUMERICHOST, on plaforms that have it, but we can't: there isn't
4745 	 * a reliable way to distinguish the "that wasn't a numeric host!" case
4746 	 * from any other EAI_NONAME cases.) */
4747 	err = evutil_getaddrinfo_common_(nodename, servname, &hints, &res, &port);
4748 	if (err != EVUTIL_EAI_NEED_RESOLVE) {
4749 		cb(err, res, arg);
4750 		return NULL;
4751 	}
4752 
4753 	/* If there is an entry in the hosts file, we should give it now. */
4754 	if (!evdns_getaddrinfo_fromhosts(dns_base, nodename, &hints, port, &res)) {
4755 		cb(0, res, arg);
4756 		return NULL;
4757 	}
4758 
4759 	/* Okay, things are serious now. We're going to need to actually
4760 	 * launch a request.
4761 	 */
4762 	data = mm_calloc(1,sizeof(struct evdns_getaddrinfo_request));
4763 	if (!data) {
4764 		cb(EVUTIL_EAI_MEMORY, NULL, arg);
4765 		return NULL;
4766 	}
4767 
4768 	memcpy(&data->hints, &hints, sizeof(data->hints));
4769 	data->port = (ev_uint16_t)port;
4770 	data->ipv4_request.type = DNS_IPv4_A;
4771 	data->ipv6_request.type = DNS_IPv6_AAAA;
4772 	data->user_cb = cb;
4773 	data->user_data = arg;
4774 	data->evdns_base = dns_base;
4775 
4776 	want_cname = (hints.ai_flags & EVUTIL_AI_CANONNAME);
4777 
4778 	/* If we are asked for a PF_UNSPEC address, we launch two requests in
4779 	 * parallel: one for an A address and one for an AAAA address.  We
4780 	 * can't send just one request, since many servers only answer one
4781 	 * question per DNS request.
4782 	 *
4783 	 * Once we have the answer to one request, we allow for a short
4784 	 * timeout before we report it, to see if the other one arrives.  If
4785 	 * they both show up in time, then we report both the answers.
4786 	 *
4787 	 * If too many addresses of one type time out or fail, we should stop
4788 	 * launching those requests. (XXX we don't do that yet.)
4789 	 */
4790 
4791 	EVDNS_LOCK(dns_base);
4792 
4793 	if (hints.ai_family != PF_INET6) {
4794 		log(EVDNS_LOG_DEBUG, "Sending request for %s on ipv4 as %p",
4795 		    nodename, &data->ipv4_request);
4796 
4797 		data->ipv4_request.r = evdns_base_resolve_ipv4(dns_base,
4798 		    nodename, 0, evdns_getaddrinfo_gotresolve,
4799 		    &data->ipv4_request);
4800 		if (want_cname && data->ipv4_request.r)
4801 			data->ipv4_request.r->current_req->put_cname_in_ptr =
4802 			    &data->cname_result;
4803 	}
4804 	if (hints.ai_family != PF_INET) {
4805 		log(EVDNS_LOG_DEBUG, "Sending request for %s on ipv6 as %p",
4806 		    nodename, &data->ipv6_request);
4807 
4808 		data->ipv6_request.r = evdns_base_resolve_ipv6(dns_base,
4809 		    nodename, 0, evdns_getaddrinfo_gotresolve,
4810 		    &data->ipv6_request);
4811 		if (want_cname && data->ipv6_request.r)
4812 			data->ipv6_request.r->current_req->put_cname_in_ptr =
4813 			    &data->cname_result;
4814 	}
4815 
4816 	evtimer_assign(&data->timeout, dns_base->event_base,
4817 	    evdns_getaddrinfo_timeout_cb, data);
4818 
4819 	started = (data->ipv4_request.r || data->ipv6_request.r);
4820 
4821 	EVDNS_UNLOCK(dns_base);
4822 
4823 	if (started) {
4824 		return data;
4825 	} else {
4826 		mm_free(data);
4827 		cb(EVUTIL_EAI_FAIL, NULL, arg);
4828 		return NULL;
4829 	}
4830 }
4831 
4832 void
4833 evdns_getaddrinfo_cancel(struct evdns_getaddrinfo_request *data)
4834 {
4835 	EVDNS_LOCK(data->evdns_base);
4836 	if (data->request_done) {
4837 		EVDNS_UNLOCK(data->evdns_base);
4838 		return;
4839 	}
4840 	event_del(&data->timeout);
4841 	data->user_canceled = 1;
4842 	if (data->ipv4_request.r)
4843 		evdns_cancel_request(data->evdns_base, data->ipv4_request.r);
4844 	if (data->ipv6_request.r)
4845 		evdns_cancel_request(data->evdns_base, data->ipv6_request.r);
4846 	EVDNS_UNLOCK(data->evdns_base);
4847 }
4848