1: /* $Id: evdns.c,v 1.1.1.1 2012/02/21 23:02:54 misho Exp $ */
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@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@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 (nameserver && 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 = LoadLibraryA("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 (RegQueryValueExA(key, subkey, 0, &type, NULL, &bufsz)
2920: != ERROR_MORE_DATA)
2921: return -1;
2922: if (!(buf = malloc(bufsz)))
2923: return -1;
2924:
2925: if (RegQueryValueExA(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 (RegOpenKeyExA(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 = RegOpenKeyExA(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 (RegOpenKeyExA(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
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