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      1 /* $Id: evdns.c 6979 2006-08-04 18:31:13Z nickm $ */
      2 
      3 /* The original version of this module was written by Adam Langley; for
      4  * a history of modifications, check out the subversion logs.
      5  *
      6  * When editing this module, try to keep it re-mergeable by Adam.  Don't
      7  * reformat the whitespace, add Tor dependencies, or so on.
      8  *
      9  * TODO:
     10  *   - Support IPv6 and PTR records.
     11  *   - Replace all externally visible magic numbers with #defined constants.
     12  *   - Write doccumentation for APIs of all external functions.
     13  */
     14 
     15 /* Async DNS Library
     16  * Adam Langley <agl (at) imperialviolet.org>
     17  * http://www.imperialviolet.org/eventdns.html
     18  * Public Domain code
     19  *
     20  * This software is Public Domain. To view a copy of the public domain dedication,
     21  * visit http://creativecommons.org/licenses/publicdomain/ or send a letter to
     22  * Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.
     23  *
     24  * I ask and expect, but do not require, that all derivative works contain an
     25  * attribution similar to:
     26  * 	Parts developed by Adam Langley <agl (at) imperialviolet.org>
     27  *
     28  * You may wish to replace the word "Parts" with something else depending on
     29  * the amount of original code.
     30  *
     31  * (Derivative works does not include programs which link against, run or include
     32  * the source verbatim in their source distributions)
     33  *
     34  * Version: 0.1b
     35  */
     36 
     37 #include <sys/types.h>
     38 #ifdef HAVE_CONFIG_H
     39 #include "config.h"
     40 #endif
     41 
     42 #ifdef DNS_USE_FTIME_FOR_ID
     43 #include <sys/timeb.h>
     44 #endif
     45 
     46 #ifndef DNS_USE_CPU_CLOCK_FOR_ID
     47 #ifndef DNS_USE_GETTIMEOFDAY_FOR_ID
     48 #ifndef DNS_USE_OPENSSL_FOR_ID
     49 #ifndef DNS_USE_FTIME_FOR_ID
     50 #error Must configure at least one id generation method.
     51 #error Please see the documentation.
     52 #endif
     53 #endif
     54 #endif
     55 #endif
     56 
     57 /* #define _POSIX_C_SOURCE 200507 */
     58 #define _GNU_SOURCE
     59 
     60 #ifdef DNS_USE_CPU_CLOCK_FOR_ID
     61 #ifdef DNS_USE_OPENSSL_FOR_ID
     62 #error Multiple id options selected
     63 #endif
     64 #ifdef DNS_USE_GETTIMEOFDAY_FOR_ID
     65 #error Multiple id options selected
     66 #endif
     67 #include <time.h>
     68 #endif
     69 
     70 #ifdef DNS_USE_OPENSSL_FOR_ID
     71 #ifdef DNS_USE_GETTIMEOFDAY_FOR_ID
     72 #error Multiple id options selected
     73 #endif
     74 #include <openssl/rand.h>
     75 #endif
     76 
     77 #ifndef _FORTIFY_SOURCE
     78 #define _FORTIFY_SOURCE 3
     79 #endif
     80 
     81 #include <string.h>
     82 #include <fcntl.h>
     83 #ifdef HAVE_SYS_TIME_H
     84 #include <sys/time.h>
     85 #endif
     86 #ifdef HAVE_STDINT_H
     87 #include <stdint.h>
     88 #endif
     89 #include <stdlib.h>
     90 #include <string.h>
     91 #include <errno.h>
     92 #include <assert.h>
     93 #ifdef HAVE_UNISTD_H
     94 #include <unistd.h>
     95 #endif
     96 #include <limits.h>
     97 #include <sys/stat.h>
     98 #include <ctype.h>
     99 #include <stdio.h>
    100 #include <stdarg.h>
    101 
    102 #include "evdns.h"
    103 #include "evutil.h"
    104 #include "log.h"
    105 #ifdef WIN32
    106 #include <winsock2.h>
    107 #include <windows.h>
    108 #include <iphlpapi.h>
    109 #include <io.h>
    110 #else
    111 #include <sys/socket.h>
    112 #include <netinet/in.h>
    113 #include <arpa/inet.h>
    114 #endif
    115 
    116 #ifdef HAVE_NETINET_IN6_H
    117 #include <netinet/in6.h>
    118 #endif
    119 
    120 #define EVDNS_LOG_DEBUG 0
    121 #define EVDNS_LOG_WARN 1
    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 #ifdef __USE_ISOC99B
    133 /* libevent doesn't work without this */
    134 typedef ev_uint8_t u_char;
    135 typedef unsigned int uint;
    136 #endif
    137 #include "event.h"
    138 
    139 #define u64 ev_uint64_t
    140 #define u32 ev_uint32_t
    141 #define u16 ev_uint16_t
    142 #define u8  ev_uint8_t
    143 
    144 #ifdef WIN32
    145 #define open _open
    146 #define read _read
    147 #define close _close
    148 #define strdup _strdup
    149 #endif
    150 
    151 #define MAX_ADDRS 32  /* maximum number of addresses from a single packet */
    152 /* which we bother recording */
    153 
    154 #define TYPE_A         EVDNS_TYPE_A
    155 #define TYPE_CNAME     5
    156 #define TYPE_PTR       EVDNS_TYPE_PTR
    157 #define TYPE_AAAA      EVDNS_TYPE_AAAA
    158 
    159 #define CLASS_INET     EVDNS_CLASS_INET
    160 
    161 struct request {
    162 	u8 *request;  /* the dns packet data */
    163 	unsigned int request_len;
    164 	int reissue_count;
    165 	int tx_count;  /* the number of times that this packet has been sent */
    166 	unsigned int request_type; /* TYPE_PTR or TYPE_A */
    167 	void *user_pointer;  /* the pointer given to us for this request */
    168 	evdns_callback_type user_callback;
    169 	struct nameserver *ns;  /* the server which we last sent it */
    170 
    171 	/* elements used by the searching code */
    172 	int search_index;
    173 	struct search_state *search_state;
    174 	char *search_origname;  /* needs to be free()ed */
    175 	int search_flags;
    176 
    177 	/* these objects are kept in a circular list */
    178 	struct request *next, *prev;
    179 
    180 	struct event timeout_event;
    181 
    182 	u16 trans_id;  /* the transaction id */
    183 	char request_appended;  /* true if the request pointer is data which follows this struct */
    184 	char transmit_me;  /* needs to be transmitted */
    185 };
    186 
    187 #ifndef HAVE_STRUCT_IN6_ADDR
    188 struct in6_addr {
    189 	u8 s6_addr[16];
    190 };
    191 #endif
    192 
    193 struct reply {
    194 	unsigned int type;
    195 	unsigned int have_answer;
    196 	union {
    197 		struct {
    198 			u32 addrcount;
    199 			u32 addresses[MAX_ADDRS];
    200 		} a;
    201 		struct {
    202 			u32 addrcount;
    203 			struct in6_addr addresses[MAX_ADDRS];
    204 		} aaaa;
    205 		struct {
    206 			char name[HOST_NAME_MAX];
    207 		} ptr;
    208 	} data;
    209 };
    210 
    211 struct nameserver {
    212 	int socket;  /* a connected UDP socket */
    213 	u32 address;
    214 	u16 port;
    215 	int failed_times;  /* number of times which we have given this server a chance */
    216 	int timedout;  /* number of times in a row a request has timed out */
    217 	struct event event;
    218 	/* these objects are kept in a circular list */
    219 	struct nameserver *next, *prev;
    220 	struct event timeout_event;  /* used to keep the timeout for */
    221 				     /* when we next probe this server. */
    222 				     /* Valid if state == 0 */
    223 	char state;  /* zero if we think that this server is down */
    224 	char choked;  /* true if we have an EAGAIN from this server's socket */
    225 	char write_waiting;  /* true if we are waiting for EV_WRITE events */
    226 };
    227 
    228 static struct request *req_head = NULL, *req_waiting_head = NULL;
    229 static struct nameserver *server_head = NULL;
    230 
    231 /* Represents a local port where we're listening for DNS requests. Right now, */
    232 /* only UDP is supported. */
    233 struct evdns_server_port {
    234 	int socket; /* socket we use to read queries and write replies. */
    235 	int refcnt; /* reference count. */
    236 	char choked; /* Are we currently blocked from writing? */
    237 	char closing; /* Are we trying to close this port, pending writes? */
    238 	evdns_request_callback_fn_type user_callback; /* Fn to handle requests */
    239 	void *user_data; /* Opaque pointer passed to user_callback */
    240 	struct event event; /* Read/write event */
    241 	/* circular list of replies that we want to write. */
    242 	struct server_request *pending_replies;
    243 };
    244 
    245 /* Represents part of a reply being built.	(That is, a single RR.) */
    246 struct server_reply_item {
    247 	struct server_reply_item *next; /* next item in sequence. */
    248 	char *name; /* name part of the RR */
    249 	u16 type : 16; /* The RR type */
    250 	u16 class : 16; /* The RR class (usually CLASS_INET) */
    251 	u32 ttl; /* The RR TTL */
    252 	char is_name; /* True iff data is a label */
    253 	u16 datalen; /* Length of data; -1 if data is a label */
    254 	void *data; /* The contents of the RR */
    255 };
    256 
    257 /* Represents a request that we've received as a DNS server, and holds */
    258 /* the components of the reply as we're constructing it. */
    259 struct server_request {
    260 	/* Pointers to the next and previous entries on the list of replies */
    261 	/* that we're waiting to write.	 Only set if we have tried to respond */
    262 	/* and gotten EAGAIN. */
    263 	struct server_request *next_pending;
    264 	struct server_request *prev_pending;
    265 
    266 	u16 trans_id; /* Transaction id. */
    267 	struct evdns_server_port *port; /* Which port received this request on? */
    268 	struct sockaddr_storage addr; /* Where to send the response */
    269 	socklen_t addrlen; /* length of addr */
    270 
    271 	int n_answer; /* how many answer RRs have been set? */
    272 	int n_authority; /* how many authority RRs have been set? */
    273 	int n_additional; /* how many additional RRs have been set? */
    274 
    275 	struct server_reply_item *answer; /* linked list of answer RRs */
    276 	struct server_reply_item *authority; /* linked list of authority RRs */
    277 	struct server_reply_item *additional; /* linked list of additional RRs */
    278 
    279 	/* Constructed response.  Only set once we're ready to send a reply. */
    280 	/* Once this is set, the RR fields are cleared, and no more should be set. */
    281 	char *response;
    282 	size_t response_len;
    283 
    284 	/* Caller-visible fields: flags, questions. */
    285 	struct evdns_server_request base;
    286 };
    287 
    288 /* helper macro */
    289 #define OFFSET_OF(st, member) ((off_t) (((char*)&((st*)0)->member)-(char*)0))
    290 
    291 /* Given a pointer to an evdns_server_request, get the corresponding */
    292 /* server_request. */
    293 #define TO_SERVER_REQUEST(base_ptr)										\
    294 	((struct server_request*)											\
    295 	 (((char*)(base_ptr) - OFFSET_OF(struct server_request, base))))
    296 
    297 /* The number of good nameservers that we have */
    298 static int global_good_nameservers = 0;
    299 
    300 /* inflight requests are contained in the req_head list */
    301 /* and are actually going out across the network */
    302 static int global_requests_inflight = 0;
    303 /* requests which aren't inflight are in the waiting list */
    304 /* and are counted here */
    305 static int global_requests_waiting = 0;
    306 
    307 static int global_max_requests_inflight = 64;
    308 
    309 static struct timeval global_timeout = {5, 0};  /* 5 seconds */
    310 static int global_max_reissues = 1;  /* a reissue occurs when we get some errors from the server */
    311 static int global_max_retransmits = 3;  /* number of times we'll retransmit a request which timed out */
    312 /* number of timeouts in a row before we consider this server to be down */
    313 static int global_max_nameserver_timeout = 3;
    314 
    315 /* These are the timeout values for nameservers. If we find a nameserver is down */
    316 /* we try to probe it at intervals as given below. Values are in seconds. */
    317 static const struct timeval global_nameserver_timeouts[] = {{10, 0}, {60, 0}, {300, 0}, {900, 0}, {3600, 0}};
    318 static const int global_nameserver_timeouts_length = sizeof(global_nameserver_timeouts)/sizeof(struct timeval);
    319 
    320 static struct nameserver *nameserver_pick(void);
    321 static void evdns_request_insert(struct request *req, struct request **head);
    322 static void nameserver_ready_callback(int fd, short events, void *arg);
    323 static int evdns_transmit(void);
    324 static int evdns_request_transmit(struct request *req);
    325 static void nameserver_send_probe(struct nameserver *const ns);
    326 static void search_request_finished(struct request *const);
    327 static int search_try_next(struct request *const req);
    328 static int search_request_new(int type, const char *const name, int flags, evdns_callback_type user_callback, void *user_arg);
    329 static void evdns_requests_pump_waiting_queue(void);
    330 static u16 transaction_id_pick(void);
    331 static struct request *request_new(int type, const char *name, int flags, evdns_callback_type callback, void *ptr);
    332 static void request_submit(struct request *const req);
    333 
    334 static int server_request_free(struct server_request *req);
    335 static void server_request_free_answers(struct server_request *req);
    336 static void server_port_free(struct evdns_server_port *port);
    337 static void server_port_ready_callback(int fd, short events, void *arg);
    338 
    339 static int strtoint(const char *const str);
    340 
    341 #ifdef WIN32
    342 static int
    343 last_error(int sock)
    344 {
    345 	int optval, optvallen=sizeof(optval);
    346 	int err = WSAGetLastError();
    347 	if (err == WSAEWOULDBLOCK && sock >= 0) {
    348 		if (getsockopt(sock, SOL_SOCKET, SO_ERROR, (void*)&optval,
    349 			       &optvallen))
    350 			return err;
    351 		if (optval)
    352 			return optval;
    353 	}
    354 	return err;
    355 
    356 }
    357 static int
    358 error_is_eagain(int err)
    359 {
    360 	return err == EAGAIN || err == WSAEWOULDBLOCK;
    361 }
    362 static int
    363 inet_aton(const char *c, struct in_addr *addr)
    364 {
    365 	ev_uint32_t r;
    366 	if (strcmp(c, "255.255.255.255") == 0) {
    367 		addr->s_addr = 0xffffffffu;
    368 	} else {
    369 		r = inet_addr(c);
    370 		if (r == INADDR_NONE)
    371 			return 0;
    372 		addr->s_addr = r;
    373 	}
    374 	return 1;
    375 }
    376 #else
    377 #define last_error(sock) (errno)
    378 #define error_is_eagain(err) ((err) == EAGAIN)
    379 #endif
    380 #define CLOSE_SOCKET(s) EVUTIL_CLOSESOCKET(s)
    381 
    382 #define ISSPACE(c) isspace((int)(unsigned char)(c))
    383 #define ISDIGIT(c) isdigit((int)(unsigned char)(c))
    384 
    385 static const char *
    386 debug_ntoa(u32 address)
    387 {
    388 	static char buf[32];
    389 	u32 a = ntohl(address);
    390 	evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d",
    391                       (int)(u8)((a>>24)&0xff),
    392                       (int)(u8)((a>>16)&0xff),
    393                       (int)(u8)((a>>8 )&0xff),
    394   		      (int)(u8)((a    )&0xff));
    395 	return buf;
    396 }
    397 
    398 static evdns_debug_log_fn_type evdns_log_fn = NULL;
    399 
    400 void
    401 evdns_set_log_fn(evdns_debug_log_fn_type fn)
    402 {
    403   evdns_log_fn = fn;
    404 }
    405 
    406 #ifdef __GNUC__
    407 #define EVDNS_LOG_CHECK  __attribute__ ((format(printf, 2, 3)))
    408 #else
    409 #define EVDNS_LOG_CHECK
    410 #endif
    411 
    412 static void _evdns_log(int warn, const char *fmt, ...) EVDNS_LOG_CHECK;
    413 static void
    414 _evdns_log(int warn, const char *fmt, ...)
    415 {
    416   va_list args;
    417   static char buf[512];
    418   if (!evdns_log_fn)
    419     return;
    420   va_start(args,fmt);
    421   evutil_vsnprintf(buf, sizeof(buf), fmt, args);
    422   buf[sizeof(buf)-1] = '\0';
    423   evdns_log_fn(warn, buf);
    424   va_end(args);
    425 }
    426 
    427 #define log _evdns_log
    428 
    429 /* This walks the list of inflight requests to find the */
    430 /* one with a matching transaction id. Returns NULL on */
    431 /* failure */
    432 static struct request *
    433 request_find_from_trans_id(u16 trans_id) {
    434 	struct request *req = req_head, *const started_at = req_head;
    435 
    436 	if (req) {
    437 		do {
    438 			if (req->trans_id == trans_id) return req;
    439 			req = req->next;
    440 		} while (req != started_at);
    441 	}
    442 
    443 	return NULL;
    444 }
    445 
    446 /* a libevent callback function which is called when a nameserver */
    447 /* has gone down and we want to test if it has came back to life yet */
    448 static void
    449 nameserver_prod_callback(int fd, short events, void *arg) {
    450 	struct nameserver *const ns = (struct nameserver *) arg;
    451         (void)fd;
    452         (void)events;
    453 
    454 	nameserver_send_probe(ns);
    455 }
    456 
    457 /* a libevent callback which is called when a nameserver probe (to see if */
    458 /* it has come back to life) times out. We increment the count of failed_times */
    459 /* and wait longer to send the next probe packet. */
    460 static void
    461 nameserver_probe_failed(struct nameserver *const ns) {
    462 	const struct timeval * timeout;
    463 	(void) evtimer_del(&ns->timeout_event);
    464 	if (ns->state == 1) {
    465 		/* This can happen if the nameserver acts in a way which makes us mark */
    466 		/* it as bad and then starts sending good replies. */
    467 		return;
    468 	}
    469 
    470 	timeout =
    471 	  &global_nameserver_timeouts[MIN(ns->failed_times,
    472 					  global_nameserver_timeouts_length - 1)];
    473 	ns->failed_times++;
    474 
    475 	if (evtimer_add(&ns->timeout_event, (struct timeval *) timeout) < 0) {
    476           log(EVDNS_LOG_WARN,
    477               "Error from libevent when adding timer event for %s",
    478               debug_ntoa(ns->address));
    479           /* ???? Do more? */
    480         }
    481 }
    482 
    483 /* called when a nameserver has been deemed to have failed. For example, too */
    484 /* many packets have timed out etc */
    485 static void
    486 nameserver_failed(struct nameserver *const ns, const char *msg) {
    487 	struct request *req, *started_at;
    488 	/* if this nameserver has already been marked as failed */
    489 	/* then don't do anything */
    490 	if (!ns->state) return;
    491 
    492 	log(EVDNS_LOG_WARN, "Nameserver %s has failed: %s",
    493             debug_ntoa(ns->address), msg);
    494 	global_good_nameservers--;
    495 	assert(global_good_nameservers >= 0);
    496 	if (global_good_nameservers == 0) {
    497 		log(EVDNS_LOG_WARN, "All nameservers have failed");
    498 	}
    499 
    500 	ns->state = 0;
    501 	ns->failed_times = 1;
    502 
    503 	if (evtimer_add(&ns->timeout_event, (struct timeval *) &global_nameserver_timeouts[0]) < 0) {
    504 		log(EVDNS_LOG_WARN,
    505 		    "Error from libevent when adding timer event for %s",
    506 		    debug_ntoa(ns->address));
    507 		/* ???? Do more? */
    508         }
    509 
    510 	/* walk the list of inflight requests to see if any can be reassigned to */
    511 	/* a different server. Requests in the waiting queue don't have a */
    512 	/* nameserver assigned yet */
    513 
    514 	/* if we don't have *any* good nameservers then there's no point */
    515 	/* trying to reassign requests to one */
    516 	if (!global_good_nameservers) return;
    517 
    518 	req = req_head;
    519 	started_at = req_head;
    520 	if (req) {
    521 		do {
    522 			if (req->tx_count == 0 && req->ns == ns) {
    523 				/* still waiting to go out, can be moved */
    524 				/* to another server */
    525 				req->ns = nameserver_pick();
    526 			}
    527 			req = req->next;
    528 		} while (req != started_at);
    529 	}
    530 }
    531 
    532 static void
    533 nameserver_up(struct nameserver *const ns) {
    534 	if (ns->state) return;
    535 	log(EVDNS_LOG_WARN, "Nameserver %s is back up",
    536 	    debug_ntoa(ns->address));
    537 	evtimer_del(&ns->timeout_event);
    538 	ns->state = 1;
    539 	ns->failed_times = 0;
    540 	ns->timedout = 0;
    541 	global_good_nameservers++;
    542 }
    543 
    544 static void
    545 request_trans_id_set(struct request *const req, const u16 trans_id) {
    546 	req->trans_id = trans_id;
    547 	*((u16 *) req->request) = htons(trans_id);
    548 }
    549 
    550 /* Called to remove a request from a list and dealloc it. */
    551 /* head is a pointer to the head of the list it should be */
    552 /* removed from or NULL if the request isn't in a list. */
    553 static void
    554 request_finished(struct request *const req, struct request **head) {
    555 	if (head) {
    556 		if (req->next == req) {
    557 			/* only item in the list */
    558 			*head = NULL;
    559 		} else {
    560 			req->next->prev = req->prev;
    561 			req->prev->next = req->next;
    562 			if (*head == req) *head = req->next;
    563 		}
    564 	}
    565 
    566 	log(EVDNS_LOG_DEBUG, "Removing timeout for request %lx",
    567 	    (unsigned long) req);
    568 	evtimer_del(&req->timeout_event);
    569 
    570 	search_request_finished(req);
    571 	global_requests_inflight--;
    572 
    573 	if (!req->request_appended) {
    574 		/* need to free the request data on it's own */
    575 		free(req->request);
    576 	} else {
    577 		/* the request data is appended onto the header */
    578 		/* so everything gets free()ed when we: */
    579 	}
    580 
    581 	free(req);
    582 
    583 	evdns_requests_pump_waiting_queue();
    584 }
    585 
    586 /* This is called when a server returns a funny error code. */
    587 /* We try the request again with another server. */
    588 /* */
    589 /* return: */
    590 /*   0 ok */
    591 /*   1 failed/reissue is pointless */
    592 static int
    593 request_reissue(struct request *req) {
    594 	const struct nameserver *const last_ns = req->ns;
    595 	/* the last nameserver should have been marked as failing */
    596 	/* by the caller of this function, therefore pick will try */
    597 	/* not to return it */
    598 	req->ns = nameserver_pick();
    599 	if (req->ns == last_ns) {
    600 		/* ... but pick did return it */
    601 		/* not a lot of point in trying again with the */
    602 		/* same server */
    603 		return 1;
    604 	}
    605 
    606 	req->reissue_count++;
    607 	req->tx_count = 0;
    608 	req->transmit_me = 1;
    609 
    610 	return 0;
    611 }
    612 
    613 /* this function looks for space on the inflight queue and promotes */
    614 /* requests from the waiting queue if it can. */
    615 static void
    616 evdns_requests_pump_waiting_queue(void) {
    617 	while (global_requests_inflight < global_max_requests_inflight &&
    618 	    global_requests_waiting) {
    619 		struct request *req;
    620 		/* move a request from the waiting queue to the inflight queue */
    621 		assert(req_waiting_head);
    622 		if (req_waiting_head->next == req_waiting_head) {
    623 			/* only one item in the queue */
    624 			req = req_waiting_head;
    625 			req_waiting_head = NULL;
    626 		} else {
    627 			req = req_waiting_head;
    628 			req->next->prev = req->prev;
    629 			req->prev->next = req->next;
    630 			req_waiting_head = req->next;
    631 		}
    632 
    633 		global_requests_waiting--;
    634 		global_requests_inflight++;
    635 
    636 		req->ns = nameserver_pick();
    637 		request_trans_id_set(req, transaction_id_pick());
    638 
    639 		evdns_request_insert(req, &req_head);
    640 		evdns_request_transmit(req);
    641 		evdns_transmit();
    642 	}
    643 }
    644 
    645 static void
    646 reply_callback(struct request *const req, u32 ttl, u32 err, struct reply *reply) {
    647 	switch (req->request_type) {
    648 	case TYPE_A:
    649 		if (reply)
    650 			req->user_callback(DNS_ERR_NONE, DNS_IPv4_A,
    651 							   reply->data.a.addrcount, ttl,
    652 						 reply->data.a.addresses,
    653 							   req->user_pointer);
    654 		else
    655 			req->user_callback(err, 0, 0, 0, NULL, req->user_pointer);
    656 		return;
    657 	case TYPE_PTR:
    658 		if (reply) {
    659 			char *name = reply->data.ptr.name;
    660 			req->user_callback(DNS_ERR_NONE, DNS_PTR, 1, ttl,
    661 							   &name, req->user_pointer);
    662 		} else {
    663 			req->user_callback(err, 0, 0, 0, NULL,
    664 							   req->user_pointer);
    665 		}
    666 		return;
    667 	case TYPE_AAAA:
    668 		if (reply)
    669 			req->user_callback(DNS_ERR_NONE, DNS_IPv6_AAAA,
    670 							   reply->data.aaaa.addrcount, ttl,
    671 							   reply->data.aaaa.addresses,
    672 							   req->user_pointer);
    673 		else
    674 			req->user_callback(err, 0, 0, 0, NULL, req->user_pointer);
    675                 return;
    676 	}
    677 	assert(0);
    678 }
    679 
    680 /* this processes a parsed reply packet */
    681 static void
    682 reply_handle(struct request *const req, u16 flags, u32 ttl, struct reply *reply) {
    683 	int error;
    684 	static const int error_codes[] = {
    685 		DNS_ERR_FORMAT, DNS_ERR_SERVERFAILED, DNS_ERR_NOTEXIST,
    686 		DNS_ERR_NOTIMPL, DNS_ERR_REFUSED
    687 	};
    688 
    689 	if (flags & 0x020f || !reply || !reply->have_answer) {
    690 		/* there was an error */
    691 		if (flags & 0x0200) {
    692 			error = DNS_ERR_TRUNCATED;
    693 		} else {
    694 			u16 error_code = (flags & 0x000f) - 1;
    695 			if (error_code > 4) {
    696 				error = DNS_ERR_UNKNOWN;
    697 			} else {
    698 				error = error_codes[error_code];
    699 			}
    700 		}
    701 
    702 		switch(error) {
    703 		case DNS_ERR_NOTIMPL:
    704 		case DNS_ERR_REFUSED:
    705 			/* we regard these errors as marking a bad nameserver */
    706 			if (req->reissue_count < global_max_reissues) {
    707 				char msg[64];
    708 				evutil_snprintf(msg, sizeof(msg),
    709 				    "Bad response %d (%s)",
    710 					 error, evdns_err_to_string(error));
    711 				nameserver_failed(req->ns, msg);
    712 				if (!request_reissue(req)) return;
    713 			}
    714 			break;
    715 		case DNS_ERR_SERVERFAILED:
    716 			/* rcode 2 (servfailed) sometimes means "we
    717 			 * are broken" and sometimes (with some binds)
    718 			 * means "that request was very confusing."
    719 			 * Treat this as a timeout, not a failure.
    720 			 */
    721 			log(EVDNS_LOG_DEBUG, "Got a SERVERFAILED from nameserver %s; "
    722 				"will allow the request to time out.",
    723 				debug_ntoa(req->ns->address));
    724 			break;
    725 		default:
    726 			/* we got a good reply from the nameserver */
    727 			nameserver_up(req->ns);
    728 		}
    729 
    730 		if (req->search_state && req->request_type != TYPE_PTR) {
    731 			/* if we have a list of domains to search in,
    732 			 * try the next one */
    733 			if (!search_try_next(req)) {
    734 				/* a new request was issued so this
    735 				 * request is finished and */
    736 				/* the user callback will be made when
    737 				 * that request (or a */
    738 				/* child of it) finishes. */
    739 				request_finished(req, &req_head);
    740 				return;
    741 			}
    742 		}
    743 
    744 		/* all else failed. Pass the failure up */
    745 		reply_callback(req, 0, error, NULL);
    746 		request_finished(req, &req_head);
    747 	} else {
    748 		/* all ok, tell the user */
    749 		reply_callback(req, ttl, 0, reply);
    750 		nameserver_up(req->ns);
    751 		request_finished(req, &req_head);
    752 	}
    753 }
    754 
    755 static int
    756 name_parse(u8 *packet, int length, int *idx, char *name_out, int name_out_len) {
    757 	int name_end = -1;
    758 	int j = *idx;
    759 	int ptr_count = 0;
    760 #define GET32(x) do { if (j + 4 > length) goto err; memcpy(&_t32, packet + j, 4); j += 4; x = ntohl(_t32); } while(0)
    761 #define GET16(x) do { if (j + 2 > length) goto err; memcpy(&_t, packet + j, 2); j += 2; x = ntohs(_t); } while(0)
    762 #define GET8(x) do { if (j >= length) goto err; x = packet[j++]; } while(0)
    763 
    764 	char *cp = name_out;
    765 	const char *const end = name_out + name_out_len;
    766 
    767 	/* Normally, names are a series of length prefixed strings terminated */
    768 	/* with a length of 0 (the lengths are u8's < 63). */
    769 	/* However, the length can start with a pair of 1 bits and that */
    770 	/* means that the next 14 bits are a pointer within the current */
    771 	/* packet. */
    772 
    773 	for(;;) {
    774 		u8 label_len;
    775 		if (j >= length) return -1;
    776 		GET8(label_len);
    777 		if (!label_len) break;
    778 		if (label_len & 0xc0) {
    779 			u8 ptr_low;
    780 			GET8(ptr_low);
    781 			if (name_end < 0) name_end = j;
    782 			j = (((int)label_len & 0x3f) << 8) + ptr_low;
    783 			/* Make sure that the target offset is in-bounds. */
    784 			if (j < 0 || j >= length) return -1;
    785 			/* If we've jumped more times than there are characters in the
    786 			 * message, we must have a loop. */
    787 			if (++ptr_count > length) return -1;
    788 			continue;
    789 		}
    790 		if (label_len > 63) return -1;
    791 		if (cp != name_out) {
    792 			if (cp + 1 >= end) return -1;
    793 			*cp++ = '.';
    794 		}
    795 		if (cp + label_len >= end) return -1;
    796 		memcpy(cp, packet + j, label_len);
    797 		cp += label_len;
    798 		j += label_len;
    799 	}
    800 	if (cp >= end) return -1;
    801 	*cp = '\0';
    802 	if (name_end < 0)
    803 		*idx = j;
    804 	else
    805 		*idx = name_end;
    806 	return 0;
    807  err:
    808 	return -1;
    809 }
    810 
    811 /* parses a raw request from a nameserver */
    812 static int
    813 reply_parse(u8 *packet, int length) {
    814 	int j = 0, k = 0;  /* index into packet */
    815 	u16 _t;  /* used by the macros */
    816 	u32 _t32;  /* used by the macros */
    817 	char tmp_name[256], cmp_name[256]; /* used by the macros */
    818 
    819 	u16 trans_id, questions, answers, authority, additional, datalength;
    820         u16 flags = 0;
    821 	u32 ttl, ttl_r = 0xffffffff;
    822 	struct reply reply;
    823 	struct request *req = NULL;
    824 	unsigned int i;
    825 
    826 	GET16(trans_id);
    827 	GET16(flags);
    828 	GET16(questions);
    829 	GET16(answers);
    830 	GET16(authority);
    831 	GET16(additional);
    832 	(void) authority; /* suppress "unused variable" warnings. */
    833 	(void) additional; /* suppress "unused variable" warnings. */
    834 
    835 	req = request_find_from_trans_id(trans_id);
    836 	if (!req) return -1;
    837 
    838 	memset(&reply, 0, sizeof(reply));
    839 
    840 	/* If it's not an answer, it doesn't correspond to any request. */
    841 	if (!(flags & 0x8000)) return -1;  /* must be an answer */
    842 	if (flags & 0x020f) {
    843 		/* there was an error */
    844 		goto err;
    845 	}
    846 	/* if (!answers) return; */  /* must have an answer of some form */
    847 
    848 	/* This macro skips a name in the DNS reply. */
    849 #define SKIP_NAME \
    850 	do { tmp_name[0] = '\0';				\
    851 		if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name))<0)\
    852 			goto err;				\
    853 	} while(0)
    854 #define TEST_NAME \
    855 	do { tmp_name[0] = '\0';				\
    856 		cmp_name[0] = '\0';				\
    857 		k = j;						\
    858 		if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name))<0)\
    859 			goto err;					\
    860 		if (name_parse(req->request, req->request_len, &k, cmp_name, sizeof(cmp_name))<0)	\
    861 			goto err;				\
    862 		if (memcmp(tmp_name, cmp_name, strlen (tmp_name)) != 0)	\
    863 			return (-1); /* we ignore mismatching names */	\
    864 	} while(0)
    865 
    866 	reply.type = req->request_type;
    867 
    868 	/* skip over each question in the reply */
    869 	for (i = 0; i < questions; ++i) {
    870 		/* the question looks like
    871 		 *   <label:name><u16:type><u16:class>
    872 		 */
    873 		TEST_NAME;
    874 		j += 4;
    875 		if (j > length) goto err;
    876 	}
    877 
    878 	/* now we have the answer section which looks like
    879 	 * <label:name><u16:type><u16:class><u32:ttl><u16:len><data...>
    880 	 */
    881 
    882 	for (i = 0; i < answers; ++i) {
    883 		u16 type, class;
    884 
    885 		SKIP_NAME;
    886 		GET16(type);
    887 		GET16(class);
    888 		GET32(ttl);
    889 		GET16(datalength);
    890 
    891 		if (type == TYPE_A && class == CLASS_INET) {
    892 			int addrcount, addrtocopy;
    893 			if (req->request_type != TYPE_A) {
    894 				j += datalength; continue;
    895 			}
    896 			if ((datalength & 3) != 0) /* not an even number of As. */
    897 			    goto err;
    898 			addrcount = datalength >> 2;
    899 			addrtocopy = MIN(MAX_ADDRS - reply.data.a.addrcount, (unsigned)addrcount);
    900 
    901 			ttl_r = MIN(ttl_r, ttl);
    902 			/* we only bother with the first four addresses. */
    903 			if (j + 4*addrtocopy > length) goto err;
    904 			memcpy(&reply.data.a.addresses[reply.data.a.addrcount],
    905 				   packet + j, 4*addrtocopy);
    906 			j += 4*addrtocopy;
    907 			reply.data.a.addrcount += addrtocopy;
    908 			reply.have_answer = 1;
    909 			if (reply.data.a.addrcount == MAX_ADDRS) break;
    910 		} else if (type == TYPE_PTR && class == CLASS_INET) {
    911 			if (req->request_type != TYPE_PTR) {
    912 				j += datalength; continue;
    913 			}
    914 			if (name_parse(packet, length, &j, reply.data.ptr.name,
    915 						   sizeof(reply.data.ptr.name))<0)
    916 				goto err;
    917 			ttl_r = MIN(ttl_r, ttl);
    918 			reply.have_answer = 1;
    919 			break;
    920 		} else if (type == TYPE_AAAA && class == CLASS_INET) {
    921 			int addrcount, addrtocopy;
    922 			if (req->request_type != TYPE_AAAA) {
    923 				j += datalength; continue;
    924 			}
    925 			if ((datalength & 15) != 0) /* not an even number of AAAAs. */
    926 				goto err;
    927 			addrcount = datalength >> 4;  /* each address is 16 bytes long */
    928 			addrtocopy = MIN(MAX_ADDRS - reply.data.aaaa.addrcount, (unsigned)addrcount);
    929 			ttl_r = MIN(ttl_r, ttl);
    930 
    931 			/* we only bother with the first four addresses. */
    932 			if (j + 16*addrtocopy > length) goto err;
    933 			memcpy(&reply.data.aaaa.addresses[reply.data.aaaa.addrcount],
    934 				   packet + j, 16*addrtocopy);
    935 			reply.data.aaaa.addrcount += addrtocopy;
    936 			j += 16*addrtocopy;
    937 			reply.have_answer = 1;
    938 			if (reply.data.aaaa.addrcount == MAX_ADDRS) break;
    939 		} else {
    940 			/* skip over any other type of resource */
    941 			j += datalength;
    942 		}
    943 	}
    944 
    945 	reply_handle(req, flags, ttl_r, &reply);
    946 	return 0;
    947  err:
    948 	if (req)
    949 		reply_handle(req, flags, 0, NULL);
    950 	return -1;
    951 }
    952 
    953 /* Parse a raw request (packet,length) sent to a nameserver port (port) from */
    954 /* a DNS client (addr,addrlen), and if it's well-formed, call the corresponding */
    955 /* callback. */
    956 static int
    957 request_parse(u8 *packet, int length, struct evdns_server_port *port, struct sockaddr *addr, socklen_t addrlen)
    958 {
    959 	int j = 0;	/* index into packet */
    960 	u16 _t;	 /* used by the macros */
    961 	char tmp_name[256]; /* used by the macros */
    962 
    963 	int i;
    964 	u16 trans_id, flags, questions, answers, authority, additional;
    965 	struct server_request *server_req = NULL;
    966 
    967 	/* Get the header fields */
    968 	GET16(trans_id);
    969 	GET16(flags);
    970 	GET16(questions);
    971 	GET16(answers);
    972 	GET16(authority);
    973 	GET16(additional);
    974 
    975 	if (flags & 0x8000) return -1; /* Must not be an answer. */
    976 	flags &= 0x0110; /* Only RD and CD get preserved. */
    977 
    978 	server_req = malloc(sizeof(struct server_request));
    979 	if (server_req == NULL) return -1;
    980 	memset(server_req, 0, sizeof(struct server_request));
    981 
    982 	server_req->trans_id = trans_id;
    983 	memcpy(&server_req->addr, addr, addrlen);
    984 	server_req->addrlen = addrlen;
    985 
    986 	server_req->base.flags = flags;
    987 	server_req->base.nquestions = 0;
    988 	server_req->base.questions = malloc(sizeof(struct evdns_server_question *) * questions);
    989 	if (server_req->base.questions == NULL)
    990 		goto err;
    991 
    992 	for (i = 0; i < questions; ++i) {
    993 		u16 type, class;
    994 		struct evdns_server_question *q;
    995 		int namelen;
    996 		if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name))<0)
    997 			goto err;
    998 		GET16(type);
    999 		GET16(class);
   1000 		namelen = strlen(tmp_name);
   1001 		q = malloc(sizeof(struct evdns_server_question) + namelen);
   1002 		if (!q)
   1003 			goto err;
   1004 		q->type = type;
   1005 		q->dns_question_class = class;
   1006 		memcpy(q->name, tmp_name, namelen+1);
   1007 		server_req->base.questions[server_req->base.nquestions++] = q;
   1008 	}
   1009 
   1010 	/* Ignore answers, authority, and additional. */
   1011 
   1012 	server_req->port = port;
   1013 	port->refcnt++;
   1014 
   1015 	/* Only standard queries are supported. */
   1016 	if (flags & 0x7800) {
   1017 		evdns_server_request_respond(&(server_req->base), DNS_ERR_NOTIMPL);
   1018 		return -1;
   1019 	}
   1020 
   1021 	port->user_callback(&(server_req->base), port->user_data);
   1022 
   1023 	return 0;
   1024 err:
   1025 	if (server_req) {
   1026 		if (server_req->base.questions) {
   1027 			for (i = 0; i < server_req->base.nquestions; ++i)
   1028 				free(server_req->base.questions[i]);
   1029 			free(server_req->base.questions);
   1030 		}
   1031 		free(server_req);
   1032 	}
   1033 	return -1;
   1034 
   1035 #undef SKIP_NAME
   1036 #undef GET32
   1037 #undef GET16
   1038 #undef GET8
   1039 }
   1040 
   1041 static u16
   1042 default_transaction_id_fn(void)
   1043 {
   1044 	u16 trans_id;
   1045 #ifdef DNS_USE_CPU_CLOCK_FOR_ID
   1046 	struct timespec ts;
   1047 	static int clkid = -1;
   1048 	if (clkid == -1) {
   1049 		clkid = CLOCK_REALTIME;
   1050 #ifdef CLOCK_MONOTONIC
   1051 		if (clock_gettime(CLOCK_MONOTONIC, &ts) != -1)
   1052 			clkid = CLOCK_MONOTONIC;
   1053 #endif
   1054 	}
   1055 	if (clock_gettime(clkid, &ts) == -1)
   1056 		event_err(1, "clock_gettime");
   1057 	trans_id = ts.tv_nsec & 0xffff;
   1058 #endif
   1059 
   1060 #ifdef DNS_USE_FTIME_FOR_ID
   1061 	struct _timeb tb;
   1062 	_ftime(&tb);
   1063 	trans_id = tb.millitm & 0xffff;
   1064 #endif
   1065 
   1066 #ifdef DNS_USE_GETTIMEOFDAY_FOR_ID
   1067 	struct timeval tv;
   1068 	evutil_gettimeofday(&tv, NULL);
   1069 	trans_id = tv.tv_usec & 0xffff;
   1070 #endif
   1071 
   1072 #ifdef DNS_USE_OPENSSL_FOR_ID
   1073 	if (RAND_pseudo_bytes((u8 *) &trans_id, 2) == -1) {
   1074 		/* in the case that the RAND call fails we back */
   1075 		/* down to using gettimeofday. */
   1076 		/*
   1077 		  struct timeval tv;
   1078 		  evutil_gettimeofday(&tv, NULL);
   1079 		  trans_id = tv.tv_usec & 0xffff;
   1080 		*/
   1081 		abort();
   1082 	}
   1083 #endif
   1084 	return trans_id;
   1085 }
   1086 
   1087 static ev_uint16_t (*trans_id_function)(void) = default_transaction_id_fn;
   1088 
   1089 void
   1090 evdns_set_transaction_id_fn(ev_uint16_t (*fn)(void))
   1091 {
   1092 	if (fn)
   1093 		trans_id_function = fn;
   1094 	else
   1095 		trans_id_function = default_transaction_id_fn;
   1096 }
   1097 
   1098 /* Try to choose a strong transaction id which isn't already in flight */
   1099 static u16
   1100 transaction_id_pick(void) {
   1101 	for (;;) {
   1102 		const struct request *req = req_head, *started_at;
   1103 		u16 trans_id = trans_id_function();
   1104 
   1105 		if (trans_id == 0xffff) continue;
   1106 		/* now check to see if that id is already inflight */
   1107 		req = started_at = req_head;
   1108 		if (req) {
   1109 			do {
   1110 				if (req->trans_id == trans_id) break;
   1111 				req = req->next;
   1112 			} while (req != started_at);
   1113 		}
   1114 		/* we didn't find it, so this is a good id */
   1115 		if (req == started_at) return trans_id;
   1116 	}
   1117 }
   1118 
   1119 /* choose a namesever to use. This function will try to ignore */
   1120 /* nameservers which we think are down and load balance across the rest */
   1121 /* by updating the server_head global each time. */
   1122 static struct nameserver *
   1123 nameserver_pick(void) {
   1124 	struct nameserver *started_at = server_head, *picked;
   1125 	if (!server_head) return NULL;
   1126 
   1127 	/* if we don't have any good nameservers then there's no */
   1128 	/* point in trying to find one. */
   1129 	if (!global_good_nameservers) {
   1130 		server_head = server_head->next;
   1131 		return server_head;
   1132 	}
   1133 
   1134 	/* remember that nameservers are in a circular list */
   1135 	for (;;) {
   1136 		if (server_head->state) {
   1137 			/* we think this server is currently good */
   1138 			picked = server_head;
   1139 			server_head = server_head->next;
   1140 			return picked;
   1141 		}
   1142 
   1143 		server_head = server_head->next;
   1144 		if (server_head == started_at) {
   1145 			/* all the nameservers seem to be down */
   1146 			/* so we just return this one and hope for the */
   1147 			/* best */
   1148 			assert(global_good_nameservers == 0);
   1149 			picked = server_head;
   1150 			server_head = server_head->next;
   1151 			return picked;
   1152 		}
   1153 	}
   1154 }
   1155 
   1156 static int
   1157 address_is_correct(struct nameserver *ns, struct sockaddr *sa, socklen_t slen)
   1158 {
   1159 	struct sockaddr_in *sin = (struct sockaddr_in*) sa;
   1160 	if (sa->sa_family != AF_INET || slen != sizeof(struct sockaddr_in))
   1161 		return 0;
   1162 	if (sin->sin_addr.s_addr != ns->address)
   1163 		return 0;
   1164 	return 1;
   1165 }
   1166 
   1167 /* this is called when a namesever socket is ready for reading */
   1168 static void
   1169 nameserver_read(struct nameserver *ns) {
   1170 	u8 packet[1500];
   1171 	struct sockaddr_storage ss;
   1172 	socklen_t addrlen = sizeof(ss);
   1173 
   1174 	for (;;) {
   1175           	const int r = recvfrom(ns->socket, packet, sizeof(packet), 0,
   1176 		    (struct sockaddr*)&ss, &addrlen);
   1177 		if (r < 0) {
   1178 			int err = last_error(ns->socket);
   1179 			if (error_is_eagain(err)) return;
   1180 			nameserver_failed(ns, strerror(err));
   1181 			return;
   1182 		}
   1183 		if (!address_is_correct(ns, (struct sockaddr*)&ss, addrlen)) {
   1184 			log(EVDNS_LOG_WARN, "Address mismatch on received "
   1185 			    "DNS packet.");
   1186 			return;
   1187 		}
   1188 		ns->timedout = 0;
   1189 		reply_parse(packet, r);
   1190 	}
   1191 }
   1192 
   1193 /* Read a packet from a DNS client on a server port s, parse it, and */
   1194 /* act accordingly. */
   1195 static void
   1196 server_port_read(struct evdns_server_port *s) {
   1197 	u8 packet[1500];
   1198 	struct sockaddr_storage addr;
   1199 	socklen_t addrlen;
   1200 	int r;
   1201 
   1202 	for (;;) {
   1203 		addrlen = sizeof(struct sockaddr_storage);
   1204 		r = recvfrom(s->socket, packet, sizeof(packet), 0,
   1205 					 (struct sockaddr*) &addr, &addrlen);
   1206 		if (r < 0) {
   1207 			int err = last_error(s->socket);
   1208 			if (error_is_eagain(err)) return;
   1209 			log(EVDNS_LOG_WARN, "Error %s (%d) while reading request.",
   1210 				strerror(err), err);
   1211 			return;
   1212 		}
   1213 		request_parse(packet, r, s, (struct sockaddr*) &addr, addrlen);
   1214 	}
   1215 }
   1216 
   1217 /* Try to write all pending replies on a given DNS server port. */
   1218 static void
   1219 server_port_flush(struct evdns_server_port *port)
   1220 {
   1221 	while (port->pending_replies) {
   1222 		struct server_request *req = port->pending_replies;
   1223 		int r = sendto(port->socket, req->response, req->response_len, 0,
   1224 			   (struct sockaddr*) &req->addr, req->addrlen);
   1225 		if (r < 0) {
   1226 			int err = last_error(port->socket);
   1227 			if (error_is_eagain(err))
   1228 				return;
   1229 			log(EVDNS_LOG_WARN, "Error %s (%d) while writing response to port; dropping", strerror(err), err);
   1230 		}
   1231 		if (server_request_free(req)) {
   1232 			/* we released the last reference to req->port. */
   1233 			return;
   1234 		}
   1235 	}
   1236 
   1237 	/* We have no more pending requests; stop listening for 'writeable' events. */
   1238 	(void) event_del(&port->event);
   1239 	event_set(&port->event, port->socket, EV_READ | EV_PERSIST,
   1240 			  server_port_ready_callback, port);
   1241 	if (event_add(&port->event, NULL) < 0) {
   1242 		log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server.");
   1243 		/* ???? Do more? */
   1244 	}
   1245 }
   1246 
   1247 /* set if we are waiting for the ability to write to this server. */
   1248 /* if waiting is true then we ask libevent for EV_WRITE events, otherwise */
   1249 /* we stop these events. */
   1250 static void
   1251 nameserver_write_waiting(struct nameserver *ns, char waiting) {
   1252 	if (ns->write_waiting == waiting) return;
   1253 
   1254 	ns->write_waiting = waiting;
   1255 	(void) event_del(&ns->event);
   1256 	event_set(&ns->event, ns->socket, EV_READ | (waiting ? EV_WRITE : 0) | EV_PERSIST,
   1257 			nameserver_ready_callback, ns);
   1258 	if (event_add(&ns->event, NULL) < 0) {
   1259           log(EVDNS_LOG_WARN, "Error from libevent when adding event for %s",
   1260               debug_ntoa(ns->address));
   1261           /* ???? Do more? */
   1262         }
   1263 }
   1264 
   1265 /* a callback function. Called by libevent when the kernel says that */
   1266 /* a nameserver socket is ready for writing or reading */
   1267 static void
   1268 nameserver_ready_callback(int fd, short events, void *arg) {
   1269 	struct nameserver *ns = (struct nameserver *) arg;
   1270         (void)fd;
   1271 
   1272 	if (events & EV_WRITE) {
   1273 		ns->choked = 0;
   1274 		if (!evdns_transmit()) {
   1275 			nameserver_write_waiting(ns, 0);
   1276 		}
   1277 	}
   1278 	if (events & EV_READ) {
   1279 		nameserver_read(ns);
   1280 	}
   1281 }
   1282 
   1283 /* a callback function. Called by libevent when the kernel says that */
   1284 /* a server socket is ready for writing or reading. */
   1285 static void
   1286 server_port_ready_callback(int fd, short events, void *arg) {
   1287 	struct evdns_server_port *port = (struct evdns_server_port *) arg;
   1288 	(void) fd;
   1289 
   1290 	if (events & EV_WRITE) {
   1291 		port->choked = 0;
   1292 		server_port_flush(port);
   1293 	}
   1294 	if (events & EV_READ) {
   1295 		server_port_read(port);
   1296 	}
   1297 }
   1298 
   1299 /* This is an inefficient representation; only use it via the dnslabel_table_*
   1300  * functions, so that is can be safely replaced with something smarter later. */
   1301 #define MAX_LABELS 128
   1302 /* Structures used to implement name compression */
   1303 struct dnslabel_entry { char *v; off_t pos; };
   1304 struct dnslabel_table {
   1305 	int n_labels; /* number of current entries */
   1306 	/* map from name to position in message */
   1307 	struct dnslabel_entry labels[MAX_LABELS];
   1308 };
   1309 
   1310 /* Initialize dnslabel_table. */
   1311 static void
   1312 dnslabel_table_init(struct dnslabel_table *table)
   1313 {
   1314 	table->n_labels = 0;
   1315 }
   1316 
   1317 /* Free all storage held by table, but not the table itself. */
   1318 static void
   1319 dnslabel_clear(struct dnslabel_table *table)
   1320 {
   1321 	int i;
   1322 	for (i = 0; i < table->n_labels; ++i)
   1323 		free(table->labels[i].v);
   1324 	table->n_labels = 0;
   1325 }
   1326 
   1327 /* return the position of the label in the current message, or -1 if the label */
   1328 /* hasn't been used yet. */
   1329 static int
   1330 dnslabel_table_get_pos(const struct dnslabel_table *table, const char *label)
   1331 {
   1332 	int i;
   1333 	for (i = 0; i < table->n_labels; ++i) {
   1334 		if (!strcmp(label, table->labels[i].v))
   1335 			return table->labels[i].pos;
   1336 	}
   1337 	return -1;
   1338 }
   1339 
   1340 /* remember that we've used the label at position pos */
   1341 static int
   1342 dnslabel_table_add(struct dnslabel_table *table, const char *label, off_t pos)
   1343 {
   1344 	char *v;
   1345 	int p;
   1346 	if (table->n_labels == MAX_LABELS)
   1347 		return (-1);
   1348 	v = strdup(label);
   1349 	if (v == NULL)
   1350 		return (-1);
   1351 	p = table->n_labels++;
   1352 	table->labels[p].v = v;
   1353 	table->labels[p].pos = pos;
   1354 
   1355 	return (0);
   1356 }
   1357 
   1358 /* Converts a string to a length-prefixed set of DNS labels, starting */
   1359 /* at buf[j]. name and buf must not overlap. name_len should be the length */
   1360 /* of name.	 table is optional, and is used for compression. */
   1361 /* */
   1362 /* Input: abc.def */
   1363 /* Output: <3>abc<3>def<0> */
   1364 /* */
   1365 /* Returns the first index after the encoded name, or negative on error. */
   1366 /*	 -1	 label was > 63 bytes */
   1367 /*	 -2	 name too long to fit in buffer. */
   1368 /* */
   1369 static off_t
   1370 dnsname_to_labels(u8 *const buf, size_t buf_len, off_t j,
   1371 				  const char *name, const int name_len,
   1372 				  struct dnslabel_table *table) {
   1373 	const char *end = name + name_len;
   1374 	int ref = 0;
   1375 	u16 _t;
   1376 
   1377 #define APPEND16(x) do {						   \
   1378 		if (j + 2 > (off_t)buf_len)				   \
   1379 			goto overflow;						   \
   1380 		_t = htons(x);							   \
   1381 		memcpy(buf + j, &_t, 2);				   \
   1382 		j += 2;									   \
   1383 	} while (0)
   1384 #define APPEND32(x) do {						   \
   1385 		if (j + 4 > (off_t)buf_len)				   \
   1386 			goto overflow;						   \
   1387 		_t32 = htonl(x);						   \
   1388 		memcpy(buf + j, &_t32, 4);				   \
   1389 		j += 4;									   \
   1390 	} while (0)
   1391 
   1392 	if (name_len > 255) return -2;
   1393 
   1394 	for (;;) {
   1395 		const char *const start = name;
   1396 		if (table && (ref = dnslabel_table_get_pos(table, name)) >= 0) {
   1397 			APPEND16(ref | 0xc000);
   1398 			return j;
   1399 		}
   1400 		name = strchr(name, '.');
   1401 		if (!name) {
   1402 			const unsigned int label_len = end - start;
   1403 			if (label_len > 63) return -1;
   1404 			if ((size_t)(j+label_len+1) > buf_len) return -2;
   1405 			if (table) dnslabel_table_add(table, start, j);
   1406 			buf[j++] = label_len;
   1407 
   1408 			memcpy(buf + j, start, end - start);
   1409 			j += end - start;
   1410 			break;
   1411 		} else {
   1412 			/* append length of the label. */
   1413 			const unsigned int label_len = name - start;
   1414 			if (label_len > 63) return -1;
   1415 			if ((size_t)(j+label_len+1) > buf_len) return -2;
   1416 			if (table) dnslabel_table_add(table, start, j);
   1417 			buf[j++] = label_len;
   1418 
   1419 			memcpy(buf + j, start, name - start);
   1420 			j += name - start;
   1421 			/* hop over the '.' */
   1422 			name++;
   1423 		}
   1424 	}
   1425 
   1426 	/* the labels must be terminated by a 0. */
   1427 	/* It's possible that the name ended in a . */
   1428 	/* in which case the zero is already there */
   1429 	if (!j || buf[j-1]) buf[j++] = 0;
   1430 	return j;
   1431  overflow:
   1432 	return (-2);
   1433 }
   1434 
   1435 /* Finds the length of a dns request for a DNS name of the given */
   1436 /* length. The actual request may be smaller than the value returned */
   1437 /* here */
   1438 static int
   1439 evdns_request_len(const int name_len) {
   1440 	return 96 + /* length of the DNS standard header */
   1441 		name_len + 2 +
   1442 		4;  /* space for the resource type */
   1443 }
   1444 
   1445 /* build a dns request packet into buf. buf should be at least as long */
   1446 /* as evdns_request_len told you it should be. */
   1447 /* */
   1448 /* Returns the amount of space used. Negative on error. */
   1449 static int
   1450 evdns_request_data_build(const char *const name, const int name_len,
   1451     const u16 trans_id, const u16 type, const u16 class,
   1452     u8 *const buf, size_t buf_len) {
   1453 	off_t j = 0;  /* current offset into buf */
   1454 	u16 _t;  /* used by the macros */
   1455 
   1456 	APPEND16(trans_id);
   1457 	APPEND16(0x0100);  /* standard query, recusion needed */
   1458 	APPEND16(1);  /* one question */
   1459 	APPEND16(0);  /* no answers */
   1460 	APPEND16(0);  /* no authority */
   1461 	APPEND16(0);  /* no additional */
   1462 
   1463 	j = dnsname_to_labels(buf, buf_len, j, name, name_len, NULL);
   1464 	if (j < 0) {
   1465 		return (int)j;
   1466 	}
   1467 
   1468 	APPEND16(type);
   1469 	APPEND16(class);
   1470 
   1471 	return (int)j;
   1472  overflow:
   1473 	return (-1);
   1474 }
   1475 
   1476 /* exported function */
   1477 struct evdns_server_port *
   1478 evdns_add_server_port(int socket, int is_tcp, evdns_request_callback_fn_type cb, void *user_data)
   1479 {
   1480 	struct evdns_server_port *port;
   1481 	if (!(port = malloc(sizeof(struct evdns_server_port))))
   1482 		return NULL;
   1483 	memset(port, 0, sizeof(struct evdns_server_port));
   1484 
   1485 	assert(!is_tcp); /* TCP sockets not yet implemented */
   1486 	port->socket = socket;
   1487 	port->refcnt = 1;
   1488 	port->choked = 0;
   1489 	port->closing = 0;
   1490 	port->user_callback = cb;
   1491 	port->user_data = user_data;
   1492 	port->pending_replies = NULL;
   1493 
   1494 	event_set(&port->event, port->socket, EV_READ | EV_PERSIST,
   1495 			  server_port_ready_callback, port);
   1496 	event_add(&port->event, NULL); /* check return. */
   1497 	return port;
   1498 }
   1499 
   1500 /* exported function */
   1501 void
   1502 evdns_close_server_port(struct evdns_server_port *port)
   1503 {
   1504 	if (--port->refcnt == 0)
   1505 		server_port_free(port);
   1506 	port->closing = 1;
   1507 }
   1508 
   1509 /* exported function */
   1510 int
   1511 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)
   1512 {
   1513 	struct server_request *req = TO_SERVER_REQUEST(_req);
   1514 	struct server_reply_item **itemp, *item;
   1515 	int *countp;
   1516 
   1517 	if (req->response) /* have we already answered? */
   1518 		return (-1);
   1519 
   1520 	switch (section) {
   1521 	case EVDNS_ANSWER_SECTION:
   1522 		itemp = &req->answer;
   1523 		countp = &req->n_answer;
   1524 		break;
   1525 	case EVDNS_AUTHORITY_SECTION:
   1526 		itemp = &req->authority;
   1527 		countp = &req->n_authority;
   1528 		break;
   1529 	case EVDNS_ADDITIONAL_SECTION:
   1530 		itemp = &req->additional;
   1531 		countp = &req->n_additional;
   1532 		break;
   1533 	default:
   1534 		return (-1);
   1535 	}
   1536 	while (*itemp) {
   1537 		itemp = &((*itemp)->next);
   1538 	}
   1539 	item = malloc(sizeof(struct server_reply_item));
   1540 	if (!item)
   1541 		return -1;
   1542 	item->next = NULL;
   1543 	if (!(item->name = strdup(name))) {
   1544 		free(item);
   1545 		return -1;
   1546 	}
   1547 	item->type = type;
   1548 	item->dns_question_class = class;
   1549 	item->ttl = ttl;
   1550 	item->is_name = is_name != 0;
   1551 	item->datalen = 0;
   1552 	item->data = NULL;
   1553 	if (data) {
   1554 		if (item->is_name) {
   1555 			if (!(item->data = strdup(data))) {
   1556 				free(item->name);
   1557 				free(item);
   1558 				return -1;
   1559 			}
   1560 			item->datalen = (u16)-1;
   1561 		} else {
   1562 			if (!(item->data = malloc(datalen))) {
   1563 				free(item->name);
   1564 				free(item);
   1565 				return -1;
   1566 			}
   1567 			item->datalen = datalen;
   1568 			memcpy(item->data, data, datalen);
   1569 		}
   1570 	}
   1571 
   1572 	*itemp = item;
   1573 	++(*countp);
   1574 	return 0;
   1575 }
   1576 
   1577 /* exported function */
   1578 int
   1579 evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, void *addrs, int ttl)
   1580 {
   1581 	return evdns_server_request_add_reply(
   1582 		  req, EVDNS_ANSWER_SECTION, name, TYPE_A, CLASS_INET,
   1583 		  ttl, n*4, 0, addrs);
   1584 }
   1585 
   1586 /* exported function */
   1587 int
   1588 evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, void *addrs, int ttl)
   1589 {
   1590 	return evdns_server_request_add_reply(
   1591 		  req, EVDNS_ANSWER_SECTION, name, TYPE_AAAA, CLASS_INET,
   1592 		  ttl, n*16, 0, addrs);
   1593 }
   1594 
   1595 /* exported function */
   1596 int
   1597 evdns_server_request_add_ptr_reply(struct evdns_server_request *req, struct in_addr *in, const char *inaddr_name, const char *hostname, int ttl)
   1598 {
   1599 	u32 a;
   1600 	char buf[32];
   1601 	assert(in || inaddr_name);
   1602 	assert(!(in && inaddr_name));
   1603 	if (in) {
   1604 		a = ntohl(in->s_addr);
   1605 		evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa",
   1606 				(int)(u8)((a	)&0xff),
   1607 				(int)(u8)((a>>8 )&0xff),
   1608 				(int)(u8)((a>>16)&0xff),
   1609 				(int)(u8)((a>>24)&0xff));
   1610 		inaddr_name = buf;
   1611 	}
   1612 	return evdns_server_request_add_reply(
   1613 		  req, EVDNS_ANSWER_SECTION, inaddr_name, TYPE_PTR, CLASS_INET,
   1614 		  ttl, -1, 1, hostname);
   1615 }
   1616 
   1617 /* exported function */
   1618 int
   1619 evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl)
   1620 {
   1621 	return evdns_server_request_add_reply(
   1622 		  req, EVDNS_ANSWER_SECTION, name, TYPE_CNAME, CLASS_INET,
   1623 		  ttl, -1, 1, cname);
   1624 }
   1625 
   1626 
   1627 static int
   1628 evdns_server_request_format_response(struct server_request *req, int err)
   1629 {
   1630 	unsigned char buf[1500];
   1631 	size_t buf_len = sizeof(buf);
   1632 	off_t j = 0, r;
   1633 	u16 _t;
   1634 	u32 _t32;
   1635 	int i;
   1636 	u16 flags;
   1637 	struct dnslabel_table table;
   1638 
   1639 	if (err < 0 || err > 15) return -1;
   1640 
   1641 	/* Set response bit and error code; copy OPCODE and RD fields from
   1642 	 * question; copy RA and AA if set by caller. */
   1643 	flags = req->base.flags;
   1644 	flags |= (0x8000 | err);
   1645 
   1646 	dnslabel_table_init(&table);
   1647 	APPEND16(req->trans_id);
   1648 	APPEND16(flags);
   1649 	APPEND16(req->base.nquestions);
   1650 	APPEND16(req->n_answer);
   1651 	APPEND16(req->n_authority);
   1652 	APPEND16(req->n_additional);
   1653 
   1654 	/* Add questions. */
   1655 	for (i=0; i < req->base.nquestions; ++i) {
   1656 		const char *s = req->base.questions[i]->name;
   1657 		j = dnsname_to_labels(buf, buf_len, j, s, strlen(s), &table);
   1658 		if (j < 0) {
   1659 			dnslabel_clear(&table);
   1660 			return (int) j;
   1661 		}
   1662 		APPEND16(req->base.questions[i]->type);
   1663 		APPEND16(req->base.questions[i]->dns_question_class);
   1664 	}
   1665 
   1666 	/* Add answer, authority, and additional sections. */
   1667 	for (i=0; i<3; ++i) {
   1668 		struct server_reply_item *item;
   1669 		if (i==0)
   1670 			item = req->answer;
   1671 		else if (i==1)
   1672 			item = req->authority;
   1673 		else
   1674 			item = req->additional;
   1675 		while (item) {
   1676 			r = dnsname_to_labels(buf, buf_len, j, item->name, strlen(item->name), &table);
   1677 			if (r < 0)
   1678 				goto overflow;
   1679 			j = r;
   1680 
   1681 			APPEND16(item->type);
   1682 			APPEND16(item->dns_question_class);
   1683 			APPEND32(item->ttl);
   1684 			if (item->is_name) {
   1685 				off_t len_idx = j, name_start;
   1686 				j += 2;
   1687 				name_start = j;
   1688 				r = dnsname_to_labels(buf, buf_len, j, item->data, strlen(item->data), &table);
   1689 				if (r < 0)
   1690 					goto overflow;
   1691 				j = r;
   1692 				_t = htons( (short) (j-name_start) );
   1693 				memcpy(buf+len_idx, &_t, 2);
   1694 			} else {
   1695 				APPEND16(item->datalen);
   1696 				if (j+item->datalen > (off_t)buf_len)
   1697 					goto overflow;
   1698 				memcpy(buf+j, item->data, item->datalen);
   1699 				j += item->datalen;
   1700 			}
   1701 			item = item->next;
   1702 		}
   1703 	}
   1704 
   1705 	if (j > 512) {
   1706 overflow:
   1707 		j = 512;
   1708 		buf[2] |= 0x02; /* set the truncated bit. */
   1709 	}
   1710 
   1711 	req->response_len = j;
   1712 
   1713 	if (!(req->response = malloc(req->response_len))) {
   1714 		server_request_free_answers(req);
   1715 		dnslabel_clear(&table);
   1716 		return (-1);
   1717 	}
   1718 	memcpy(req->response, buf, req->response_len);
   1719 	server_request_free_answers(req);
   1720 	dnslabel_clear(&table);
   1721 	return (0);
   1722 }
   1723 
   1724 /* exported function */
   1725 int
   1726 evdns_server_request_respond(struct evdns_server_request *_req, int err)
   1727 {
   1728 	struct server_request *req = TO_SERVER_REQUEST(_req);
   1729 	struct evdns_server_port *port = req->port;
   1730 	int r;
   1731 	if (!req->response) {
   1732 		if ((r = evdns_server_request_format_response(req, err))<0)
   1733 			return r;
   1734 	}
   1735 
   1736 	r = sendto(port->socket, req->response, req->response_len, 0,
   1737 			   (struct sockaddr*) &req->addr, req->addrlen);
   1738 	if (r<0) {
   1739 		int sock_err = last_error(port->socket);
   1740 		if (! error_is_eagain(sock_err))
   1741 			return -1;
   1742 
   1743 		if (port->pending_replies) {
   1744 			req->prev_pending = port->pending_replies->prev_pending;
   1745 			req->next_pending = port->pending_replies;
   1746 			req->prev_pending->next_pending =
   1747 				req->next_pending->prev_pending = req;
   1748 		} else {
   1749 			req->prev_pending = req->next_pending = req;
   1750 			port->pending_replies = req;
   1751 			port->choked = 1;
   1752 
   1753 			(void) event_del(&port->event);
   1754 			event_set(&port->event, port->socket, (port->closing?0:EV_READ) | EV_WRITE | EV_PERSIST, server_port_ready_callback, port);
   1755 
   1756 			if (event_add(&port->event, NULL) < 0) {
   1757 				log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server");
   1758 			}
   1759 
   1760 		}
   1761 
   1762 		return 1;
   1763 	}
   1764 	if (server_request_free(req))
   1765 		return 0;
   1766 
   1767 	if (port->pending_replies)
   1768 		server_port_flush(port);
   1769 
   1770 	return 0;
   1771 }
   1772 
   1773 /* Free all storage held by RRs in req. */
   1774 static void
   1775 server_request_free_answers(struct server_request *req)
   1776 {
   1777 	struct server_reply_item *victim, *next, **list;
   1778 	int i;
   1779 	for (i = 0; i < 3; ++i) {
   1780 		if (i==0)
   1781 			list = &req->answer;
   1782 		else if (i==1)
   1783 			list = &req->authority;
   1784 		else
   1785 			list = &req->additional;
   1786 
   1787 		victim = *list;
   1788 		while (victim) {
   1789 			next = victim->next;
   1790 			free(victim->name);
   1791 			if (victim->data)
   1792 				free(victim->data);
   1793 			free(victim);
   1794 			victim = next;
   1795 		}
   1796 		*list = NULL;
   1797 	}
   1798 }
   1799 
   1800 /* Free all storage held by req, and remove links to it. */
   1801 /* return true iff we just wound up freeing the server_port. */
   1802 static int
   1803 server_request_free(struct server_request *req)
   1804 {
   1805 	int i, rc=1;
   1806 	if (req->base.questions) {
   1807 		for (i = 0; i < req->base.nquestions; ++i)
   1808 			free(req->base.questions[i]);
   1809 		free(req->base.questions);
   1810 	}
   1811 
   1812 	if (req->port) {
   1813 		if (req->port->pending_replies == req) {
   1814 			if (req->next_pending)
   1815 				req->port->pending_replies = req->next_pending;
   1816 			else
   1817 				req->port->pending_replies = NULL;
   1818 		}
   1819 		rc = --req->port->refcnt;
   1820 	}
   1821 
   1822 	if (req->response) {
   1823 		free(req->response);
   1824 	}
   1825 
   1826 	server_request_free_answers(req);
   1827 
   1828 	if (req->next_pending && req->next_pending != req) {
   1829 		req->next_pending->prev_pending = req->prev_pending;
   1830 		req->prev_pending->next_pending = req->next_pending;
   1831 	}
   1832 
   1833 	if (rc == 0) {
   1834 		server_port_free(req->port);
   1835 		free(req);
   1836 		return (1);
   1837 	}
   1838 	free(req);
   1839 	return (0);
   1840 }
   1841 
   1842 /* Free all storage held by an evdns_server_port.  Only called when  */
   1843 static void
   1844 server_port_free(struct evdns_server_port *port)
   1845 {
   1846 	assert(port);
   1847 	assert(!port->refcnt);
   1848 	assert(!port->pending_replies);
   1849 	if (port->socket > 0) {
   1850 		CLOSE_SOCKET(port->socket);
   1851 		port->socket = -1;
   1852 	}
   1853 	(void) event_del(&port->event);
   1854 	/* XXXX actually free the port? -NM */
   1855 }
   1856 
   1857 /* exported function */
   1858 int
   1859 evdns_server_request_drop(struct evdns_server_request *_req)
   1860 {
   1861 	struct server_request *req = TO_SERVER_REQUEST(_req);
   1862 	server_request_free(req);
   1863 	return 0;
   1864 }
   1865 
   1866 /* exported function */
   1867 int
   1868 evdns_server_request_get_requesting_addr(struct evdns_server_request *_req, struct sockaddr *sa, int addr_len)
   1869 {
   1870 	struct server_request *req = TO_SERVER_REQUEST(_req);
   1871 	if (addr_len < (int)req->addrlen)
   1872 		return -1;
   1873 	memcpy(sa, &(req->addr), req->addrlen);
   1874 	return req->addrlen;
   1875 }
   1876 
   1877 #undef APPEND16
   1878 #undef APPEND32
   1879 
   1880 /* this is a libevent callback function which is called when a request */
   1881 /* has timed out. */
   1882 static void
   1883 evdns_request_timeout_callback(int fd, short events, void *arg) {
   1884 	struct request *const req = (struct request *) arg;
   1885         (void) fd;
   1886         (void) events;
   1887 
   1888 	log(EVDNS_LOG_DEBUG, "Request %lx timed out", (unsigned long) arg);
   1889 
   1890 	req->ns->timedout++;
   1891 	if (req->ns->timedout > global_max_nameserver_timeout) {
   1892 		req->ns->timedout = 0;
   1893 		nameserver_failed(req->ns, "request timed out.");
   1894 	}
   1895 
   1896 	(void) evtimer_del(&req->timeout_event);
   1897 	if (req->tx_count >= global_max_retransmits) {
   1898 		/* this request has failed */
   1899 		reply_callback(req, 0, DNS_ERR_TIMEOUT, NULL);
   1900 		request_finished(req, &req_head);
   1901 	} else {
   1902 		/* retransmit it */
   1903 		evdns_request_transmit(req);
   1904 	}
   1905 }
   1906 
   1907 /* try to send a request to a given server. */
   1908 /* */
   1909 /* return: */
   1910 /*   0 ok */
   1911 /*   1 temporary failure */
   1912 /*   2 other failure */
   1913 static int
   1914 evdns_request_transmit_to(struct request *req, struct nameserver *server) {
   1915 	struct sockaddr_in sin;
   1916 	int r;
   1917 	memset(&sin, 0, sizeof(sin));
   1918 	sin.sin_addr.s_addr = req->ns->address;
   1919 	sin.sin_port = req->ns->port;
   1920 	sin.sin_family = AF_INET;
   1921 
   1922 	r = sendto(server->socket, req->request, req->request_len, 0,
   1923 	    (struct sockaddr*)&sin, sizeof(sin));
   1924 	if (r < 0) {
   1925 		int err = last_error(server->socket);
   1926 		if (error_is_eagain(err)) return 1;
   1927 		nameserver_failed(req->ns, strerror(err));
   1928 		return 2;
   1929 	} else if (r != (int)req->request_len) {
   1930 		return 1;  /* short write */
   1931 	} else {
   1932 		return 0;
   1933 	}
   1934 }
   1935 
   1936 /* try to send a request, updating the fields of the request */
   1937 /* as needed */
   1938 /* */
   1939 /* return: */
   1940 /*   0 ok */
   1941 /*   1 failed */
   1942 static int
   1943 evdns_request_transmit(struct request *req) {
   1944 	int retcode = 0, r;
   1945 
   1946 	/* if we fail to send this packet then this flag marks it */
   1947 	/* for evdns_transmit */
   1948 	req->transmit_me = 1;
   1949 	if (req->trans_id == 0xffff) abort();
   1950 
   1951 	if (req->ns->choked) {
   1952 		/* don't bother trying to write to a socket */
   1953 		/* which we have had EAGAIN from */
   1954 		return 1;
   1955 	}
   1956 
   1957 	r = evdns_request_transmit_to(req, req->ns);
   1958 	switch (r) {
   1959 	case 1:
   1960 		/* temp failure */
   1961 		req->ns->choked = 1;
   1962 		nameserver_write_waiting(req->ns, 1);
   1963 		return 1;
   1964 	case 2:
   1965 		/* failed in some other way */
   1966 		retcode = 1;
   1967 		/* fall through */
   1968 	default:
   1969 		/* all ok */
   1970 		log(EVDNS_LOG_DEBUG,
   1971 		    "Setting timeout for request %lx", (unsigned long) req);
   1972 		if (evtimer_add(&req->timeout_event, &global_timeout) < 0) {
   1973                   log(EVDNS_LOG_WARN,
   1974 		      "Error from libevent when adding timer for request %lx",
   1975                       (unsigned long) req);
   1976                   /* ???? Do more? */
   1977                 }
   1978 		req->tx_count++;
   1979 		req->transmit_me = 0;
   1980 		return retcode;
   1981 	}
   1982 }
   1983 
   1984 static void
   1985 nameserver_probe_callback(int result, char type, int count, int ttl, void *addresses, void *arg) {
   1986 	struct nameserver *const ns = (struct nameserver *) arg;
   1987         (void) type;
   1988         (void) count;
   1989         (void) ttl;
   1990         (void) addresses;
   1991 
   1992 	if (result == DNS_ERR_NONE || result == DNS_ERR_NOTEXIST) {
   1993 		/* this is a good reply */
   1994 		nameserver_up(ns);
   1995 	} else nameserver_probe_failed(ns);
   1996 }
   1997 
   1998 static void
   1999 nameserver_send_probe(struct nameserver *const ns) {
   2000 	struct request *req;
   2001 	/* here we need to send a probe to a given nameserver */
   2002 	/* in the hope that it is up now. */
   2003 
   2004   	log(EVDNS_LOG_DEBUG, "Sending probe to %s", debug_ntoa(ns->address));
   2005 
   2006 	req = request_new(TYPE_A, "www.google.com", DNS_QUERY_NO_SEARCH, nameserver_probe_callback, ns);
   2007         if (!req) return;
   2008 	/* we force this into the inflight queue no matter what */
   2009 	request_trans_id_set(req, transaction_id_pick());
   2010 	req->ns = ns;
   2011 	request_submit(req);
   2012 }
   2013 
   2014 /* returns: */
   2015 /*   0 didn't try to transmit anything */
   2016 /*   1 tried to transmit something */
   2017 static int
   2018 evdns_transmit(void) {
   2019 	char did_try_to_transmit = 0;
   2020 
   2021 	if (req_head) {
   2022 		struct request *const started_at = req_head, *req = req_head;
   2023 		/* first transmit all the requests which are currently waiting */
   2024 		do {
   2025 			if (req->transmit_me) {
   2026 				did_try_to_transmit = 1;
   2027 				evdns_request_transmit(req);
   2028 			}
   2029 
   2030 			req = req->next;
   2031 		} while (req != started_at);
   2032 	}
   2033 
   2034 	return did_try_to_transmit;
   2035 }
   2036 
   2037 /* exported function */
   2038 int
   2039 evdns_count_nameservers(void)
   2040 {
   2041 	const struct nameserver *server = server_head;
   2042 	int n = 0;
   2043 	if (!server)
   2044 		return 0;
   2045 	do {
   2046 		++n;
   2047 		server = server->next;
   2048 	} while (server != server_head);
   2049 	return n;
   2050 }
   2051 
   2052 /* exported function */
   2053 int
   2054 evdns_clear_nameservers_and_suspend(void)
   2055 {
   2056 	struct nameserver *server = server_head, *started_at = server_head;
   2057 	struct request *req = req_head, *req_started_at = req_head;
   2058 
   2059 	if (!server)
   2060 		return 0;
   2061 	while (1) {
   2062 		struct nameserver *next = server->next;
   2063 		(void) event_del(&server->event);
   2064 		if (evtimer_initialized(&server->timeout_event))
   2065 			(void) evtimer_del(&server->timeout_event);
   2066 		if (server->socket >= 0)
   2067 			CLOSE_SOCKET(server->socket);
   2068 		free(server);
   2069 		if (next == started_at)
   2070 			break;
   2071 		server = next;
   2072 	}
   2073 	server_head = NULL;
   2074 	global_good_nameservers = 0;
   2075 
   2076 	while (req) {
   2077 		struct request *next = req->next;
   2078 		req->tx_count = req->reissue_count = 0;
   2079 		req->ns = NULL;
   2080 		/* ???? What to do about searches? */
   2081 		(void) evtimer_del(&req->timeout_event);
   2082 		req->trans_id = 0;
   2083 		req->transmit_me = 0;
   2084 
   2085 		global_requests_waiting++;
   2086 		evdns_request_insert(req, &req_waiting_head);
   2087 		/* We want to insert these suspended elements at the front of
   2088 		 * the waiting queue, since they were pending before any of
   2089 		 * the waiting entries were added.  This is a circular list,
   2090 		 * so we can just shift the start back by one.*/
   2091 		req_waiting_head = req_waiting_head->prev;
   2092 
   2093 		if (next == req_started_at)
   2094 			break;
   2095 		req = next;
   2096 	}
   2097 	req_head = NULL;
   2098 	global_requests_inflight = 0;
   2099 
   2100 	return 0;
   2101 }
   2102 
   2103 
   2104 /* exported function */
   2105 int
   2106 evdns_resume(void)
   2107 {
   2108 	evdns_requests_pump_waiting_queue();
   2109 	return 0;
   2110 }
   2111 
   2112 static int
   2113 _evdns_nameserver_add_impl(unsigned long int address, int port) {
   2114 	/* first check to see if we already have this nameserver */
   2115 
   2116 	const struct nameserver *server = server_head, *const started_at = server_head;
   2117 	struct nameserver *ns;
   2118 	int err = 0;
   2119 	if (server) {
   2120 		do {
   2121 			if (server->address == address) return 3;
   2122 			server = server->next;
   2123 		} while (server != started_at);
   2124 	}
   2125 
   2126 	ns = (struct nameserver *) malloc(sizeof(struct nameserver));
   2127         if (!ns) return -1;
   2128 
   2129 	memset(ns, 0, sizeof(struct nameserver));
   2130 
   2131 	evtimer_set(&ns->timeout_event, nameserver_prod_callback, ns);
   2132 
   2133 	ns->socket = socket(PF_INET, SOCK_DGRAM, 0);
   2134 	if (ns->socket < 0) { err = 1; goto out1; }
   2135         evutil_make_socket_nonblocking(ns->socket);
   2136 
   2137 	ns->address = address;
   2138 	ns->port = htons(port);
   2139 	ns->state = 1;
   2140 	event_set(&ns->event, ns->socket, EV_READ | EV_PERSIST, nameserver_ready_callback, ns);
   2141 	if (event_add(&ns->event, NULL) < 0) {
   2142           err = 2;
   2143           goto out2;
   2144         }
   2145 
   2146 	log(EVDNS_LOG_DEBUG, "Added nameserver %s", debug_ntoa(address));
   2147 
   2148 	/* insert this nameserver into the list of them */
   2149 	if (!server_head) {
   2150 		ns->next = ns->prev = ns;
   2151 		server_head = ns;
   2152 	} else {
   2153 		ns->next = server_head->next;
   2154 		ns->prev = server_head;
   2155 		server_head->next = ns;
   2156 		if (server_head->prev == server_head) {
   2157 			server_head->prev = ns;
   2158 		}
   2159 	}
   2160 
   2161 	global_good_nameservers++;
   2162 
   2163 	return 0;
   2164 
   2165 out2:
   2166 	CLOSE_SOCKET(ns->socket);
   2167 out1:
   2168 	free(ns);
   2169 	log(EVDNS_LOG_WARN, "Unable to add nameserver %s: error %d", debug_ntoa(address), err);
   2170 	return err;
   2171 }
   2172 
   2173 /* exported function */
   2174 int
   2175 evdns_nameserver_add(unsigned long int address) {
   2176 	return _evdns_nameserver_add_impl(address, 53);
   2177 }
   2178 
   2179 /* exported function */
   2180 int
   2181 evdns_nameserver_ip_add(const char *ip_as_string) {
   2182 	struct in_addr ina;
   2183 	int port;
   2184 	char buf[20];
   2185 	const char *cp;
   2186 	cp = strchr(ip_as_string, ':');
   2187 	if (! cp) {
   2188 		cp = ip_as_string;
   2189 		port = 53;
   2190 	} else {
   2191 		port = strtoint(cp+1);
   2192 		if (port < 0 || port > 65535) {
   2193 			return 4;
   2194 		}
   2195 		if ((cp-ip_as_string) >= (int)sizeof(buf)) {
   2196 			return 4;
   2197 		}
   2198 		memcpy(buf, ip_as_string, cp-ip_as_string);
   2199 		buf[cp-ip_as_string] = '\0';
   2200 		cp = buf;
   2201 	}
   2202 	if (!inet_aton(cp, &ina)) {
   2203 		return 4;
   2204 	}
   2205 	return _evdns_nameserver_add_impl(ina.s_addr, port);
   2206 }
   2207 
   2208 /* insert into the tail of the queue */
   2209 static void
   2210 evdns_request_insert(struct request *req, struct request **head) {
   2211 	if (!*head) {
   2212 		*head = req;
   2213 		req->next = req->prev = req;
   2214 		return;
   2215 	}
   2216 
   2217 	req->prev = (*head)->prev;
   2218 	req->prev->next = req;
   2219 	req->next = *head;
   2220 	(*head)->prev = req;
   2221 }
   2222 
   2223 static int
   2224 string_num_dots(const char *s) {
   2225 	int count = 0;
   2226 	while ((s = strchr(s, '.'))) {
   2227 		s++;
   2228 		count++;
   2229 	}
   2230 	return count;
   2231 }
   2232 
   2233 static struct request *
   2234 request_new(int type, const char *name, int flags,
   2235     evdns_callback_type callback, void *user_ptr) {
   2236 	const char issuing_now =
   2237 	    (global_requests_inflight < global_max_requests_inflight) ? 1 : 0;
   2238 
   2239 	const int name_len = strlen(name);
   2240 	const int request_max_len = evdns_request_len(name_len);
   2241 	const u16 trans_id = issuing_now ? transaction_id_pick() : 0xffff;
   2242 	/* the request data is alloced in a single block with the header */
   2243 	struct request *const req =
   2244 	    (struct request *) malloc(sizeof(struct request) + request_max_len);
   2245 	int rlen;
   2246         (void) flags;
   2247 
   2248         if (!req) return NULL;
   2249 	memset(req, 0, sizeof(struct request));
   2250 
   2251 	evtimer_set(&req->timeout_event, evdns_request_timeout_callback, req);
   2252 
   2253 	/* request data lives just after the header */
   2254 	req->request = ((u8 *) req) + sizeof(struct request);
   2255 	/* denotes that the request data shouldn't be free()ed */
   2256 	req->request_appended = 1;
   2257 	rlen = evdns_request_data_build(name, name_len, trans_id,
   2258 	    type, CLASS_INET, req->request, request_max_len);
   2259 	if (rlen < 0)
   2260 		goto err1;
   2261 	req->request_len = rlen;
   2262 	req->trans_id = trans_id;
   2263 	req->tx_count = 0;
   2264 	req->request_type = type;
   2265 	req->user_pointer = user_ptr;
   2266 	req->user_callback = callback;
   2267 	req->ns = issuing_now ? nameserver_pick() : NULL;
   2268 	req->next = req->prev = NULL;
   2269 
   2270 	return req;
   2271 err1:
   2272 	free(req);
   2273 	return NULL;
   2274 }
   2275 
   2276 static void
   2277 request_submit(struct request *const req) {
   2278 	if (req->ns) {
   2279 		/* if it has a nameserver assigned then this is going */
   2280 		/* straight into the inflight queue */
   2281 		evdns_request_insert(req, &req_head);
   2282 		global_requests_inflight++;
   2283 		evdns_request_transmit(req);
   2284 	} else {
   2285 		evdns_request_insert(req, &req_waiting_head);
   2286 		global_requests_waiting++;
   2287 	}
   2288 }
   2289 
   2290 /* exported function */
   2291 int evdns_resolve_ipv4(const char *name, int flags,
   2292     evdns_callback_type callback, void *ptr) {
   2293 	log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name);
   2294 	if (flags & DNS_QUERY_NO_SEARCH) {
   2295 		struct request *const req =
   2296 			request_new(TYPE_A, name, flags, callback, ptr);
   2297 		if (req == NULL)
   2298 			return (1);
   2299 		request_submit(req);
   2300 		return (0);
   2301 	} else {
   2302 		return (search_request_new(TYPE_A, name, flags, callback, ptr));
   2303 	}
   2304 }
   2305 
   2306 /* exported function */
   2307 int evdns_resolve_ipv6(const char *name, int flags,
   2308 					   evdns_callback_type callback, void *ptr) {
   2309 	log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name);
   2310 	if (flags & DNS_QUERY_NO_SEARCH) {
   2311 		struct request *const req =
   2312 			request_new(TYPE_AAAA, name, flags, callback, ptr);
   2313 		if (req == NULL)
   2314 			return (1);
   2315 		request_submit(req);
   2316 		return (0);
   2317 	} else {
   2318 		return (search_request_new(TYPE_AAAA, name, flags, callback, ptr));
   2319 	}
   2320 }
   2321 
   2322 int evdns_resolve_reverse(const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) {
   2323 	char buf[32];
   2324 	struct request *req;
   2325 	u32 a;
   2326 	assert(in);
   2327 	a = ntohl(in->s_addr);
   2328 	evutil_snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa",
   2329 			(int)(u8)((a	)&0xff),
   2330 			(int)(u8)((a>>8 )&0xff),
   2331 			(int)(u8)((a>>16)&0xff),
   2332 			(int)(u8)((a>>24)&0xff));
   2333 	log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf);
   2334 	req = request_new(TYPE_PTR, buf, flags, callback, ptr);
   2335 	if (!req) return 1;
   2336 	request_submit(req);
   2337 	return 0;
   2338 }
   2339 
   2340 int evdns_resolve_reverse_ipv6(const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) {
   2341 	/* 32 nybbles, 32 periods, "ip6.arpa", NUL. */
   2342 	char buf[73];
   2343 	char *cp;
   2344 	struct request *req;
   2345 	int i;
   2346 	assert(in);
   2347 	cp = buf;
   2348 	for (i=15; i >= 0; --i) {
   2349 		u8 byte = in->s6_addr[i];
   2350 		*cp++ = "0123456789abcdef"[byte & 0x0f];
   2351 		*cp++ = '.';
   2352 		*cp++ = "0123456789abcdef"[byte >> 4];
   2353 		*cp++ = '.';
   2354 	}
   2355 	assert(cp + strlen("ip6.arpa") < buf+sizeof(buf));
   2356 	memcpy(cp, "ip6.arpa", strlen("ip6.arpa")+1);
   2357 	log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf);
   2358 	req = request_new(TYPE_PTR, buf, flags, callback, ptr);
   2359 	if (!req) return 1;
   2360 	request_submit(req);
   2361 	return 0;
   2362 }
   2363 
   2364 /*/////////////////////////////////////////////////////////////////// */
   2365 /* Search support */
   2366 /* */
   2367 /* the libc resolver has support for searching a number of domains */
   2368 /* to find a name. If nothing else then it takes the single domain */
   2369 /* from the gethostname() call. */
   2370 /* */
   2371 /* It can also be configured via the domain and search options in a */
   2372 /* resolv.conf. */
   2373 /* */
   2374 /* The ndots option controls how many dots it takes for the resolver */
   2375 /* to decide that a name is non-local and so try a raw lookup first. */
   2376 
   2377 struct search_domain {
   2378 	int len;
   2379 	struct search_domain *next;
   2380 	/* the text string is appended to this structure */
   2381 };
   2382 
   2383 struct search_state {
   2384 	int refcount;
   2385 	int ndots;
   2386 	int num_domains;
   2387 	struct search_domain *head;
   2388 };
   2389 
   2390 static struct search_state *global_search_state = NULL;
   2391 
   2392 static void
   2393 search_state_decref(struct search_state *const state) {
   2394 	if (!state) return;
   2395 	state->refcount--;
   2396 	if (!state->refcount) {
   2397 		struct search_domain *next, *dom;
   2398 		for (dom = state->head; dom; dom = next) {
   2399 			next = dom->next;
   2400 			free(dom);
   2401 		}
   2402 		free(state);
   2403 	}
   2404 }
   2405 
   2406 static struct search_state *
   2407 search_state_new(void) {
   2408 	struct search_state *state = (struct search_state *) malloc(sizeof(struct search_state));
   2409         if (!state) return NULL;
   2410 	memset(state, 0, sizeof(struct search_state));
   2411 	state->refcount = 1;
   2412 	state->ndots = 1;
   2413 
   2414 	return state;
   2415 }
   2416 
   2417 static void
   2418 search_postfix_clear(void) {
   2419 	search_state_decref(global_search_state);
   2420 
   2421 	global_search_state = search_state_new();
   2422 }
   2423 
   2424 /* exported function */
   2425 void
   2426 evdns_search_clear(void) {
   2427 	search_postfix_clear();
   2428 }
   2429 
   2430 static void
   2431 search_postfix_add(const char *domain) {
   2432 	int domain_len;
   2433 	struct search_domain *sdomain;
   2434 	while (domain[0] == '.') domain++;
   2435 	domain_len = strlen(domain);
   2436 
   2437 	if (!global_search_state) global_search_state = search_state_new();
   2438         if (!global_search_state) return;
   2439 	global_search_state->num_domains++;
   2440 
   2441 	sdomain = (struct search_domain *) malloc(sizeof(struct search_domain) + domain_len);
   2442         if (!sdomain) return;
   2443 	memcpy( ((u8 *) sdomain) + sizeof(struct search_domain), domain, domain_len);
   2444 	sdomain->next = global_search_state->head;
   2445 	sdomain->len = domain_len;
   2446 
   2447 	global_search_state->head = sdomain;
   2448 }
   2449 
   2450 /* reverse the order of members in the postfix list. This is needed because, */
   2451 /* when parsing resolv.conf we push elements in the wrong order */
   2452 static void
   2453 search_reverse(void) {
   2454 	struct search_domain *cur, *prev = NULL, *next;
   2455 	cur = global_search_state->head;
   2456 	while (cur) {
   2457 		next = cur->next;
   2458 		cur->next = prev;
   2459 		prev = cur;
   2460 		cur = next;
   2461 	}
   2462 
   2463 	global_search_state->head = prev;
   2464 }
   2465 
   2466 /* exported function */
   2467 void
   2468 evdns_search_add(const char *domain) {
   2469 	search_postfix_add(domain);
   2470 }
   2471 
   2472 /* exported function */
   2473 void
   2474 evdns_search_ndots_set(const int ndots) {
   2475 	if (!global_search_state) global_search_state = search_state_new();
   2476         if (!global_search_state) return;
   2477 	global_search_state->ndots = ndots;
   2478 }
   2479 
   2480 static void
   2481 search_set_from_hostname(void) {
   2482 	char hostname[HOST_NAME_MAX + 1], *domainname;
   2483 
   2484 	search_postfix_clear();
   2485 	if (gethostname(hostname, sizeof(hostname))) return;
   2486 	domainname = strchr(hostname, '.');
   2487 	if (!domainname) return;
   2488 	search_postfix_add(domainname);
   2489 }
   2490 
   2491 /* warning: returns malloced string */
   2492 static char *
   2493 search_make_new(const struct search_state *const state, int n, const char *const base_name) {
   2494 	const int base_len = strlen(base_name);
   2495 	const char need_to_append_dot = base_name[base_len - 1] == '.' ? 0 : 1;
   2496 	struct search_domain *dom;
   2497 
   2498 	for (dom = state->head; dom; dom = dom->next) {
   2499 		if (!n--) {
   2500 			/* this is the postfix we want */
   2501 			/* the actual postfix string is kept at the end of the structure */
   2502 			const u8 *const postfix = ((u8 *) dom) + sizeof(struct search_domain);
   2503 			const int postfix_len = dom->len;
   2504 			char *const newname = (char *) malloc(base_len + need_to_append_dot + postfix_len + 1);
   2505                         if (!newname) return NULL;
   2506 			memcpy(newname, base_name, base_len);
   2507 			if (need_to_append_dot) newname[base_len] = '.';
   2508 			memcpy(newname + base_len + need_to_append_dot, postfix, postfix_len);
   2509 			newname[base_len + need_to_append_dot + postfix_len] = 0;
   2510 			return newname;
   2511 		}
   2512 	}
   2513 
   2514 	/* we ran off the end of the list and still didn't find the requested string */
   2515 	abort();
   2516 	return NULL; /* unreachable; stops warnings in some compilers. */
   2517 }
   2518 
   2519 static int
   2520 search_request_new(int type, const char *const name, int flags, evdns_callback_type user_callback, void *user_arg) {
   2521 	assert(type == TYPE_A || type == TYPE_AAAA);
   2522 	if ( ((flags & DNS_QUERY_NO_SEARCH) == 0) &&
   2523 	     global_search_state &&
   2524 		 global_search_state->num_domains) {
   2525 		/* we have some domains to search */
   2526 		struct request *req;
   2527 		if (string_num_dots(name) >= global_search_state->ndots) {
   2528 			req = request_new(type, name, flags, user_callback, user_arg);
   2529 			if (!req) return 1;
   2530 			req->search_index = -1;
   2531 		} else {
   2532 			char *const new_name = search_make_new(global_search_state, 0, name);
   2533                         if (!new_name) return 1;
   2534 			req = request_new(type, new_name, flags, user_callback, user_arg);
   2535 			free(new_name);
   2536 			if (!req) return 1;
   2537 			req->search_index = 0;
   2538 		}
   2539 		req->search_origname = strdup(name);
   2540 		req->search_state = global_search_state;
   2541 		req->search_flags = flags;
   2542 		global_search_state->refcount++;
   2543 		request_submit(req);
   2544 		return 0;
   2545 	} else {
   2546 		struct request *const req = request_new(type, name, flags, user_callback, user_arg);
   2547 		if (!req) return 1;
   2548 		request_submit(req);
   2549 		return 0;
   2550 	}
   2551 }
   2552 
   2553 /* this is called when a request has failed to find a name. We need to check */
   2554 /* if it is part of a search and, if so, try the next name in the list */
   2555 /* returns: */
   2556 /*   0 another request has been submitted */
   2557 /*   1 no more requests needed */
   2558 static int
   2559 search_try_next(struct request *const req) {
   2560 	if (req->search_state) {
   2561 		/* it is part of a search */
   2562 		char *new_name;
   2563 		struct request *newreq;
   2564 		req->search_index++;
   2565 		if (req->search_index >= req->search_state->num_domains) {
   2566 			/* no more postfixes to try, however we may need to try */
   2567 			/* this name without a postfix */
   2568 			if (string_num_dots(req->search_origname) < req->search_state->ndots) {
   2569 				/* yep, we need to try it raw */
   2570 				newreq = request_new(req->request_type, req->search_origname, req->search_flags, req->user_callback, req->user_pointer);
   2571 				log(EVDNS_LOG_DEBUG, "Search: trying raw query %s", req->search_origname);
   2572 				if (newreq) {
   2573 					request_submit(newreq);
   2574 					return 0;
   2575 				}
   2576 			}
   2577 			return 1;
   2578 		}
   2579 
   2580 		new_name = search_make_new(req->search_state, req->search_index, req->search_origname);
   2581                 if (!new_name) return 1;
   2582 		log(EVDNS_LOG_DEBUG, "Search: now trying %s (%d)", new_name, req->search_index);
   2583 		newreq = request_new(req->request_type, new_name, req->search_flags, req->user_callback, req->user_pointer);
   2584 		free(new_name);
   2585 		if (!newreq) return 1;
   2586 		newreq->search_origname = req->search_origname;
   2587 		req->search_origname = NULL;
   2588 		newreq->search_state = req->search_state;
   2589 		newreq->search_flags = req->search_flags;
   2590 		newreq->search_index = req->search_index;
   2591 		newreq->search_state->refcount++;
   2592 		request_submit(newreq);
   2593 		return 0;
   2594 	}
   2595 	return 1;
   2596 }
   2597 
   2598 static void
   2599 search_request_finished(struct request *const req) {
   2600 	if (req->search_state) {
   2601 		search_state_decref(req->search_state);
   2602 		req->search_state = NULL;
   2603 	}
   2604 	if (req->search_origname) {
   2605 		free(req->search_origname);
   2606 		req->search_origname = NULL;
   2607 	}
   2608 }
   2609 
   2610 /*/////////////////////////////////////////////////////////////////// */
   2611 /* Parsing resolv.conf files */
   2612 
   2613 static void
   2614 evdns_resolv_set_defaults(int flags) {
   2615 	/* if the file isn't found then we assume a local resolver */
   2616 	if (flags & DNS_OPTION_SEARCH) search_set_from_hostname();
   2617 	if (flags & DNS_OPTION_NAMESERVERS) evdns_nameserver_ip_add("127.0.0.1");
   2618 }
   2619 
   2620 #ifndef HAVE_STRTOK_R
   2621 static char *
   2622 strtok_r(char *s, const char *delim, char **state) {
   2623 	return strtok(s, delim);
   2624 }
   2625 #endif
   2626 
   2627 /* helper version of atoi which returns -1 on error */
   2628 static int
   2629 strtoint(const char *const str) {
   2630 	char *endptr;
   2631 	const int r = strtol(str, &endptr, 10);
   2632 	if (*endptr) return -1;
   2633 	return r;
   2634 }
   2635 
   2636 /* helper version of atoi that returns -1 on error and clips to bounds. */
   2637 static int
   2638 strtoint_clipped(const char *const str, int min, int max)
   2639 {
   2640 	int r = strtoint(str);
   2641 	if (r == -1)
   2642 		return r;
   2643 	else if (r<min)
   2644 		return min;
   2645 	else if (r>max)
   2646 		return max;
   2647 	else
   2648 		return r;
   2649 }
   2650 
   2651 /* exported function */
   2652 int
   2653 evdns_set_option(const char *option, const char *val, int flags)
   2654 {
   2655 	if (!strncmp(option, "ndots:", 6)) {
   2656 		const int ndots = strtoint(val);
   2657 		if (ndots == -1) return -1;
   2658 		if (!(flags & DNS_OPTION_SEARCH)) return 0;
   2659 		log(EVDNS_LOG_DEBUG, "Setting ndots to %d", ndots);
   2660 		if (!global_search_state) global_search_state = search_state_new();
   2661 		if (!global_search_state) return -1;
   2662 		global_search_state->ndots = ndots;
   2663 	} else if (!strncmp(option, "timeout:", 8)) {
   2664 		const int timeout = strtoint(val);
   2665 		if (timeout == -1) return -1;
   2666 		if (!(flags & DNS_OPTION_MISC)) return 0;
   2667 		log(EVDNS_LOG_DEBUG, "Setting timeout to %d", timeout);
   2668 		global_timeout.tv_sec = timeout;
   2669 	} else if (!strncmp(option, "max-timeouts:", 12)) {
   2670 		const int maxtimeout = strtoint_clipped(val, 1, 255);
   2671 		if (maxtimeout == -1) return -1;
   2672 		if (!(flags & DNS_OPTION_MISC)) return 0;
   2673 		log(EVDNS_LOG_DEBUG, "Setting maximum allowed timeouts to %d",
   2674 			maxtimeout);
   2675 		global_max_nameserver_timeout = maxtimeout;
   2676 	} else if (!strncmp(option, "max-inflight:", 13)) {
   2677 		const int maxinflight = strtoint_clipped(val, 1, 65000);
   2678 		if (maxinflight == -1) return -1;
   2679 		if (!(flags & DNS_OPTION_MISC)) return 0;
   2680 		log(EVDNS_LOG_DEBUG, "Setting maximum inflight requests to %d",
   2681 			maxinflight);
   2682 		global_max_requests_inflight = maxinflight;
   2683 	} else if (!strncmp(option, "attempts:", 9)) {
   2684 		int retries = strtoint(val);
   2685 		if (retries == -1) return -1;
   2686 		if (retries > 255) retries = 255;
   2687 		if (!(flags & DNS_OPTION_MISC)) return 0;
   2688 		log(EVDNS_LOG_DEBUG, "Setting retries to %d", retries);
   2689 		global_max_retransmits = retries;
   2690 	}
   2691 	return 0;
   2692 }
   2693 
   2694 static void
   2695 resolv_conf_parse_line(char *const start, int flags) {
   2696 	char *strtok_state;
   2697 	static const char *const delims = " \t";
   2698 #define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state)
   2699 
   2700 	char *const first_token = strtok_r(start, delims, &strtok_state);
   2701 	if (!first_token) return;
   2702 
   2703 	if (!strcmp(first_token, "nameserver") && (flags & DNS_OPTION_NAMESERVERS)) {
   2704 		const char *const nameserver = NEXT_TOKEN;
   2705 		struct in_addr ina;
   2706 
   2707 		if (inet_aton(nameserver, &ina)) {
   2708 			/* address is valid */
   2709 			evdns_nameserver_add(ina.s_addr);
   2710 		}
   2711 	} else if (!strcmp(first_token, "domain") && (flags & DNS_OPTION_SEARCH)) {
   2712 		const char *const domain = NEXT_TOKEN;
   2713 		if (domain) {
   2714 			search_postfix_clear();
   2715 			search_postfix_add(domain);
   2716 		}
   2717 	} else if (!strcmp(first_token, "search") && (flags & DNS_OPTION_SEARCH)) {
   2718 		const char *domain;
   2719 		search_postfix_clear();
   2720 
   2721 		while ((domain = NEXT_TOKEN)) {
   2722 			search_postfix_add(domain);
   2723 		}
   2724 		search_reverse();
   2725 	} else if (!strcmp(first_token, "options")) {
   2726 		const char *option;
   2727 		while ((option = NEXT_TOKEN)) {
   2728 			const char *val = strchr(option, ':');
   2729 			evdns_set_option(option, val ? val+1 : "", flags);
   2730 		}
   2731 	}
   2732 #undef NEXT_TOKEN
   2733 }
   2734 
   2735 /* exported function */
   2736 /* returns: */
   2737 /*   0 no errors */
   2738 /*   1 failed to open file */
   2739 /*   2 failed to stat file */
   2740 /*   3 file too large */
   2741 /*   4 out of memory */
   2742 /*   5 short read from file */
   2743 int
   2744 evdns_resolv_conf_parse(int flags, const char *const filename) {
   2745 	struct stat st;
   2746 	int fd, n, r;
   2747 	u8 *resolv;
   2748 	char *start;
   2749 	int err = 0;
   2750 
   2751 	log(EVDNS_LOG_DEBUG, "Parsing resolv.conf file %s", filename);
   2752 
   2753 	fd = open(filename, O_RDONLY);
   2754 	if (fd < 0) {
   2755 		evdns_resolv_set_defaults(flags);
   2756 		return 1;
   2757 	}
   2758 
   2759 	if (fstat(fd, &st)) { err = 2; goto out1; }
   2760 	if (!st.st_size) {
   2761 		evdns_resolv_set_defaults(flags);
   2762 		err = (flags & DNS_OPTION_NAMESERVERS) ? 6 : 0;
   2763 		goto out1;
   2764 	}
   2765 	if (st.st_size > 65535) { err = 3; goto out1; }  /* no resolv.conf should be any bigger */
   2766 
   2767 	resolv = (u8 *) malloc((size_t)st.st_size + 1);
   2768 	if (!resolv) { err = 4; goto out1; }
   2769 
   2770 	n = 0;
   2771 	while ((r = read(fd, resolv+n, (size_t)st.st_size-n)) > 0) {
   2772 		n += r;
   2773 		if (n == st.st_size)
   2774 			break;
   2775 		assert(n < st.st_size);
   2776  	}
   2777 	if (r < 0) { err = 5; goto out2; }
   2778 	resolv[n] = 0;	 /* we malloced an extra byte; this should be fine. */
   2779 
   2780 	start = (char *) resolv;
   2781 	for (;;) {
   2782 		char *const newline = strchr(start, '\n');
   2783 		if (!newline) {
   2784 			resolv_conf_parse_line(start, flags);
   2785 			break;
   2786 		} else {
   2787 			*newline = 0;
   2788 			resolv_conf_parse_line(start, flags);
   2789 			start = newline + 1;
   2790 		}
   2791 	}
   2792 
   2793 	if (!server_head && (flags & DNS_OPTION_NAMESERVERS)) {
   2794 		/* no nameservers were configured. */
   2795 		evdns_nameserver_ip_add("127.0.0.1");
   2796 		err = 6;
   2797 	}
   2798 	if (flags & DNS_OPTION_SEARCH && (!global_search_state || global_search_state->num_domains == 0)) {
   2799 		search_set_from_hostname();
   2800 	}
   2801 
   2802 out2:
   2803 	free(resolv);
   2804 out1:
   2805 	close(fd);
   2806 	return err;
   2807 }
   2808 
   2809 #ifdef WIN32
   2810 /* Add multiple nameservers from a space-or-comma-separated list. */
   2811 static int
   2812 evdns_nameserver_ip_add_line(const char *ips) {
   2813 	const char *addr;
   2814 	char *buf;
   2815 	int r;
   2816 	while (*ips) {
   2817 		while (ISSPACE(*ips) || *ips == ',' || *ips == '\t')
   2818 			++ips;
   2819 		addr = ips;
   2820 		while (ISDIGIT(*ips) || *ips == '.' || *ips == ':')
   2821 			++ips;
   2822 		buf = malloc(ips-addr+1);
   2823 		if (!buf) return 4;
   2824 		memcpy(buf, addr, ips-addr);
   2825 		buf[ips-addr] = '\0';
   2826 		r = evdns_nameserver_ip_add(buf);
   2827 		free(buf);
   2828 		if (r) return r;
   2829 	}
   2830 	return 0;
   2831 }
   2832 
   2833 typedef DWORD(WINAPI *GetNetworkParams_fn_t)(FIXED_INFO *, DWORD*);
   2834 
   2835 /* Use the windows GetNetworkParams interface in iphlpapi.dll to */
   2836 /* figure out what our nameservers are. */
   2837 static int
   2838 load_nameservers_with_getnetworkparams(void)
   2839 {
   2840 	/* Based on MSDN examples and inspection of  c-ares code. */
   2841 	FIXED_INFO *fixed;
   2842 	HMODULE handle = 0;
   2843 	ULONG size = sizeof(FIXED_INFO);
   2844 	void *buf = NULL;
   2845 	int status = 0, r, added_any;
   2846 	IP_ADDR_STRING *ns;
   2847 	GetNetworkParams_fn_t fn;
   2848 
   2849 	if (!(handle = LoadLibrary("iphlpapi.dll"))) {
   2850 		log(EVDNS_LOG_WARN, "Could not open iphlpapi.dll");
   2851 		status = -1;
   2852 		goto done;
   2853 	}
   2854 	if (!(fn = (GetNetworkParams_fn_t) GetProcAddress(handle, "GetNetworkParams"))) {
   2855 		log(EVDNS_LOG_WARN, "Could not get address of function.");
   2856 		status = -1;
   2857 		goto done;
   2858 	}
   2859 
   2860 	buf = malloc(size);
   2861 	if (!buf) { status = 4; goto done; }
   2862 	fixed = buf;
   2863 	r = fn(fixed, &size);
   2864 	if (r != ERROR_SUCCESS && r != ERROR_BUFFER_OVERFLOW) {
   2865 		status = -1;
   2866 		goto done;
   2867 	}
   2868 	if (r != ERROR_SUCCESS) {
   2869 		free(buf);
   2870 		buf = malloc(size);
   2871 		if (!buf) { status = 4; goto done; }
   2872 		fixed = buf;
   2873 		r = fn(fixed, &size);
   2874 		if (r != ERROR_SUCCESS) {
   2875 			log(EVDNS_LOG_DEBUG, "fn() failed.");
   2876 			status = -1;
   2877 			goto done;
   2878 		}
   2879 	}
   2880 
   2881 	assert(fixed);
   2882 	added_any = 0;
   2883 	ns = &(fixed->DnsServerList);
   2884 	while (ns) {
   2885 		r = evdns_nameserver_ip_add_line(ns->IpAddress.String);
   2886 		if (r) {
   2887 			log(EVDNS_LOG_DEBUG,"Could not add nameserver %s to list,error: %d",
   2888 				(ns->IpAddress.String),(int)GetLastError());
   2889 			status = r;
   2890 			goto done;
   2891 		} else {
   2892 			log(EVDNS_LOG_DEBUG,"Succesfully added %s as nameserver",ns->IpAddress.String);
   2893 		}
   2894 
   2895 		added_any++;
   2896 		ns = ns->Next;
   2897 	}
   2898 
   2899 	if (!added_any) {
   2900 		log(EVDNS_LOG_DEBUG, "No nameservers added.");
   2901 		status = -1;
   2902 	}
   2903 
   2904  done:
   2905 	if (buf)
   2906 		free(buf);
   2907 	if (handle)
   2908 		FreeLibrary(handle);
   2909 	return status;
   2910 }
   2911 
   2912 static int
   2913 config_nameserver_from_reg_key(HKEY key, const char *subkey)
   2914 {
   2915 	char *buf;
   2916 	DWORD bufsz = 0, type = 0;
   2917 	int status = 0;
   2918 
   2919 	if (RegQueryValueEx(key, subkey, 0, &type, NULL, &bufsz)
   2920 	    != ERROR_MORE_DATA)
   2921 		return -1;
   2922 	if (!(buf = malloc(bufsz)))
   2923 		return -1;
   2924 
   2925 	if (RegQueryValueEx(key, subkey, 0, &type, (LPBYTE)buf, &bufsz)
   2926 	    == ERROR_SUCCESS && bufsz > 1) {
   2927 		status = evdns_nameserver_ip_add_line(buf);
   2928 	}
   2929 
   2930 	free(buf);
   2931 	return status;
   2932 }
   2933 
   2934 #define SERVICES_KEY "System\\CurrentControlSet\\Services\\"
   2935 #define WIN_NS_9X_KEY  SERVICES_KEY "VxD\\MSTCP"
   2936 #define WIN_NS_NT_KEY  SERVICES_KEY "Tcpip\\Parameters"
   2937 
   2938 static int
   2939 load_nameservers_from_registry(void)
   2940 {
   2941 	int found = 0;
   2942 	int r;
   2943 #define TRY(k, name) \
   2944 	if (!found && config_nameserver_from_reg_key(k,name) == 0) {	\
   2945 		log(EVDNS_LOG_DEBUG,"Found nameservers in %s/%s",#k,name); \
   2946 		found = 1;						\
   2947 	} else if (!found) {						\
   2948 		log(EVDNS_LOG_DEBUG,"Didn't find nameservers in %s/%s", \
   2949 		    #k,#name);						\
   2950 	}
   2951 
   2952 	if (((int)GetVersion()) > 0) { /* NT */
   2953 		HKEY nt_key = 0, interfaces_key = 0;
   2954 
   2955 		if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0,
   2956 				 KEY_READ, &nt_key) != ERROR_SUCCESS) {
   2957 			log(EVDNS_LOG_DEBUG,"Couldn't open nt key, %d",(int)GetLastError());
   2958 			return -1;
   2959 		}
   2960 		r = RegOpenKeyEx(nt_key, "Interfaces", 0,
   2961 			     KEY_QUERY_VALUE|KEY_ENUMERATE_SUB_KEYS,
   2962 			     &interfaces_key);
   2963 		if (r != ERROR_SUCCESS) {
   2964 			log(EVDNS_LOG_DEBUG,"Couldn't open interfaces key, %d",(int)GetLastError());
   2965 			return -1;
   2966 		}
   2967 		TRY(nt_key, "NameServer");
   2968 		TRY(nt_key, "DhcpNameServer");
   2969 		TRY(interfaces_key, "NameServer");
   2970 		TRY(interfaces_key, "DhcpNameServer");
   2971 		RegCloseKey(interfaces_key);
   2972 		RegCloseKey(nt_key);
   2973 	} else {
   2974 		HKEY win_key = 0;
   2975 		if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_9X_KEY, 0,
   2976 				 KEY_READ, &win_key) != ERROR_SUCCESS) {
   2977 			log(EVDNS_LOG_DEBUG, "Couldn't open registry key, %d", (int)GetLastError());
   2978 			return -1;
   2979 		}
   2980 		TRY(win_key, "NameServer");
   2981 		RegCloseKey(win_key);
   2982 	}
   2983 
   2984 	if (found == 0) {
   2985 		log(EVDNS_LOG_WARN,"Didn't find any nameservers.");
   2986 	}
   2987 
   2988 	return found ? 0 : -1;
   2989 #undef TRY
   2990 }
   2991 
   2992 int
   2993 evdns_config_windows_nameservers(void)
   2994 {
   2995 	if (load_nameservers_with_getnetworkparams() == 0)
   2996 		return 0;
   2997 	return load_nameservers_from_registry();
   2998 }
   2999 #endif
   3000 
   3001 int
   3002 evdns_init(void)
   3003 {
   3004 	int res = 0;
   3005 #ifdef WIN32
   3006 	res = evdns_config_windows_nameservers();
   3007 #else
   3008 	res = evdns_resolv_conf_parse(DNS_OPTIONS_ALL, "/etc/resolv.conf");
   3009 #endif
   3010 
   3011 	return (res);
   3012 }
   3013 
   3014 const char *
   3015 evdns_err_to_string(int err)
   3016 {
   3017     switch (err) {
   3018 	case DNS_ERR_NONE: return "no error";
   3019 	case DNS_ERR_FORMAT: return "misformatted query";
   3020 	case DNS_ERR_SERVERFAILED: return "server failed";
   3021 	case DNS_ERR_NOTEXIST: return "name does not exist";
   3022 	case DNS_ERR_NOTIMPL: return "query not implemented";
   3023 	case DNS_ERR_REFUSED: return "refused";
   3024 
   3025 	case DNS_ERR_TRUNCATED: return "reply truncated or ill-formed";
   3026 	case DNS_ERR_UNKNOWN: return "unknown";
   3027 	case DNS_ERR_TIMEOUT: return "request timed out";
   3028 	case DNS_ERR_SHUTDOWN: return "dns subsystem shut down";
   3029 	default: return "[Unknown error code]";
   3030     }
   3031 }
   3032 
   3033 void
   3034 evdns_shutdown(int fail_requests)
   3035 {
   3036 	struct nameserver *server, *server_next;
   3037 	struct search_domain *dom, *dom_next;
   3038 
   3039 	while (req_head) {
   3040 		if (fail_requests)
   3041 			reply_callback(req_head, 0, DNS_ERR_SHUTDOWN, NULL);
   3042 		request_finished(req_head, &req_head);
   3043 	}
   3044 	while (req_waiting_head) {
   3045 		if (fail_requests)
   3046 			reply_callback(req_waiting_head, 0, DNS_ERR_SHUTDOWN, NULL);
   3047 		request_finished(req_waiting_head, &req_waiting_head);
   3048 	}
   3049 	global_requests_inflight = global_requests_waiting = 0;
   3050 
   3051 	for (server = server_head; server; server = server_next) {
   3052 		server_next = server->next;
   3053 		if (server->socket >= 0)
   3054 			CLOSE_SOCKET(server->socket);
   3055 		(void) event_del(&server->event);
   3056 		if (server->state == 0)
   3057                         (void) event_del(&server->timeout_event);
   3058 		free(server);
   3059 		if (server_next == server_head)
   3060 			break;
   3061 	}
   3062 	server_head = NULL;
   3063 	global_good_nameservers = 0;
   3064 
   3065 	if (global_search_state) {
   3066 		for (dom = global_search_state->head; dom; dom = dom_next) {
   3067 			dom_next = dom->next;
   3068 			free(dom);
   3069 		}
   3070 		free(global_search_state);
   3071 		global_search_state = NULL;
   3072 	}
   3073 	evdns_log_fn = NULL;
   3074 }
   3075 
   3076 #ifdef EVDNS_MAIN
   3077 void
   3078 main_callback(int result, char type, int count, int ttl,
   3079 			  void *addrs, void *orig) {
   3080 	char *n = (char*)orig;
   3081 	int i;
   3082 	for (i = 0; i < count; ++i) {
   3083 		if (type == DNS_IPv4_A) {
   3084 			printf("%s: %s\n", n, debug_ntoa(((u32*)addrs)[i]));
   3085 		} else if (type == DNS_PTR) {
   3086 			printf("%s: %s\n", n, ((char**)addrs)[i]);
   3087 		}
   3088 	}
   3089 	if (!count) {
   3090 		printf("%s: No answer (%d)\n", n, result);
   3091 	}
   3092 	fflush(stdout);
   3093 }
   3094 void
   3095 evdns_server_callback(struct evdns_server_request *req, void *data)
   3096 {
   3097 	int i, r;
   3098 	(void)data;
   3099 	/* dummy; give 192.168.11.11 as an answer for all A questions,
   3100 	 *	give foo.bar.example.com as an answer for all PTR questions. */
   3101 	for (i = 0; i < req->nquestions; ++i) {
   3102 		u32 ans = htonl(0xc0a80b0bUL);
   3103 		if (req->questions[i]->type == EVDNS_TYPE_A &&
   3104 			req->questions[i]->dns_question_class == EVDNS_CLASS_INET) {
   3105 			printf(" -- replying for %s (A)\n", req->questions[i]->name);
   3106 			r = evdns_server_request_add_a_reply(req, req->questions[i]->name,
   3107 										  1, &ans, 10);
   3108 			if (r<0)
   3109 				printf("eeep, didn't work.\n");
   3110 		} else if (req->questions[i]->type == EVDNS_TYPE_PTR &&
   3111 				   req->questions[i]->dns_question_class == EVDNS_CLASS_INET) {
   3112 			printf(" -- replying for %s (PTR)\n", req->questions[i]->name);
   3113 			r = evdns_server_request_add_ptr_reply(req, NULL, req->questions[i]->name,
   3114 											"foo.bar.example.com", 10);
   3115 		} else {
   3116 			printf(" -- skipping %s [%d %d]\n", req->questions[i]->name,
   3117 				   req->questions[i]->type, req->questions[i]->dns_question_class);
   3118 		}
   3119 	}
   3120 
   3121 	r = evdns_request_respond(req, 0);
   3122 	if (r<0)
   3123 		printf("eeek, couldn't send reply.\n");
   3124 }
   3125 
   3126 void
   3127 logfn(int is_warn, const char *msg) {
   3128   (void) is_warn;
   3129   fprintf(stderr, "%s\n", msg);
   3130 }
   3131 int
   3132 main(int c, char **v) {
   3133 	int idx;
   3134 	int reverse = 0, verbose = 1, servertest = 0;
   3135 	if (c<2) {
   3136 		fprintf(stderr, "syntax: %s [-x] [-v] hostname\n", v[0]);
   3137 		fprintf(stderr, "syntax: %s [-servertest]\n", v[0]);
   3138 		return 1;
   3139 	}
   3140 	idx = 1;
   3141 	while (idx < c && v[idx][0] == '-') {
   3142 		if (!strcmp(v[idx], "-x"))
   3143 			reverse = 1;
   3144 		else if (!strcmp(v[idx], "-v"))
   3145 			verbose = 1;
   3146 		else if (!strcmp(v[idx], "-servertest"))
   3147 			servertest = 1;
   3148 		else
   3149 			fprintf(stderr, "Unknown option %s\n", v[idx]);
   3150 		++idx;
   3151 	}
   3152 	event_init();
   3153 	if (verbose)
   3154 		evdns_set_log_fn(logfn);
   3155 	evdns_resolv_conf_parse(DNS_OPTION_NAMESERVERS, "/etc/resolv.conf");
   3156 	if (servertest) {
   3157 		int sock;
   3158 		struct sockaddr_in my_addr;
   3159 		sock = socket(PF_INET, SOCK_DGRAM, 0);
   3160                 evutil_make_socket_nonblocking(sock);
   3161 		my_addr.sin_family = AF_INET;
   3162 		my_addr.sin_port = htons(10053);
   3163 		my_addr.sin_addr.s_addr = INADDR_ANY;
   3164 		if (bind(sock, (struct sockaddr*)&my_addr, sizeof(my_addr))<0) {
   3165 			perror("bind");
   3166 			exit(1);
   3167 		}
   3168 		evdns_add_server_port(sock, 0, evdns_server_callback, NULL);
   3169 	}
   3170 	for (; idx < c; ++idx) {
   3171 		if (reverse) {
   3172 			struct in_addr addr;
   3173 			if (!inet_aton(v[idx], &addr)) {
   3174 				fprintf(stderr, "Skipping non-IP %s\n", v[idx]);
   3175 				continue;
   3176 			}
   3177 			fprintf(stderr, "resolving %s...\n",v[idx]);
   3178 			evdns_resolve_reverse(&addr, 0, main_callback, v[idx]);
   3179 		} else {
   3180 			fprintf(stderr, "resolving (fwd) %s...\n",v[idx]);
   3181 			evdns_resolve_ipv4(v[idx], 0, main_callback, v[idx]);
   3182 		}
   3183 	}
   3184 	fflush(stdout);
   3185 	event_dispatch();
   3186 	return 0;
   3187 }
   3188 #endif
   3189