/[svn]/ircd-hybrid-7.2/src/irc_res.c
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Contents of /ircd-hybrid-7.2/src/irc_res.c

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Revision 984 - (show annotations)
Fri Aug 14 13:18:14 2009 UTC (10 years, 2 months ago) by michael
File MIME type: text/x-chdr
File size: 24235 byte(s)
- res_readreply(): fix broken logic with ipv6 enabled where we ONLY sent a
                   second A QUERY in case a -broken- nameserver returns NXDOMAIN
                   for AAAA when A record exists. fixed and removed workaround
                   for broken nameservers.

1 /*
2 * A rewrite of Darren Reeds original res.c As there is nothing
3 * left of Darrens original code, this is now licensed by the hybrid group.
4 * (Well, some of the function names are the same, and bits of the structs..)
5 * You can use it where it is useful, free even. Buy us a beer and stuff.
6 *
7 * The authors takes no responsibility for any damage or loss
8 * of property which results from the use of this software.
9 *
10 * $Id$
11 *
12 * July 1999 - Rewrote a bunch of stuff here. Change hostent builder code,
13 * added callbacks and reference counting of returned hostents.
14 * --Bleep (Thomas Helvey <tomh@inxpress.net>)
15 *
16 * This was all needlessly complicated for irc. Simplified. No more hostent
17 * All we really care about is the IP -> hostname mappings. Thats all.
18 *
19 * Apr 28, 2003 --cryogen and Dianora
20 */
21
22 #include "stdinc.h"
23 #include "tools.h"
24 #include "client.h"
25 #include "list.h"
26 #include "common.h"
27 #include "event.h"
28 #include "irc_string.h"
29 #include "sprintf_irc.h"
30 #include "ircd.h"
31 #include "numeric.h"
32 #include "restart.h"
33 #include "rng_mt.h"
34 #include "fdlist.h"
35 #include "fileio.h" /* for fbopen / fbclose / fbputs */
36 #include "s_bsd.h"
37 #include "s_log.h"
38 #include "send.h"
39 #include "memory.h"
40 #include "irc_res.h"
41 #include "irc_reslib.h"
42 #include "irc_getnameinfo.h"
43
44 #if (CHAR_BIT != 8)
45 #error this code needs to be able to address individual octets
46 #endif
47
48 static PF res_readreply;
49
50 #define MAXPACKET 1024 /* rfc sez 512 but we expand names so ... */
51 #define RES_MAXALIASES 35 /* maximum aliases allowed */
52 #define RES_MAXADDRS 35 /* maximum addresses allowed */
53 #define AR_TTL 600 /* TTL in seconds for dns cache entries */
54
55 /* RFC 1104/1105 wasn't very helpful about what these fields
56 * should be named, so for now, we'll just name them this way.
57 * we probably should look at what named calls them or something.
58 */
59 #define TYPE_SIZE (size_t)2
60 #define CLASS_SIZE (size_t)2
61 #define TTL_SIZE (size_t)4
62 #define RDLENGTH_SIZE (size_t)2
63 #define ANSWER_FIXED_SIZE (TYPE_SIZE + CLASS_SIZE + TTL_SIZE + RDLENGTH_SIZE)
64
65 typedef enum
66 {
67 REQ_IDLE, /* We're doing not much at all */
68 REQ_PTR, /* Looking up a PTR */
69 REQ_A, /* Looking up an A, possibly because AAAA failed */
70 #ifdef IPV6
71 REQ_AAAA, /* Looking up an AAAA */
72 #endif
73 REQ_CNAME, /* We got a CNAME in response, we better get a real answer next */
74 REQ_INT /* ip6.arpa failed, falling back to ip6.int */
75 } request_state;
76
77 struct reslist
78 {
79 dlink_node node;
80 int id;
81 int sent; /* number of requests sent */
82 request_state state; /* State the resolver machine is in */
83 time_t ttl;
84 char type;
85 char retries; /* retry counter */
86 char sends; /* number of sends (>1 means resent) */
87 char resend; /* send flag. 0 == dont resend */
88 time_t sentat;
89 time_t timeout;
90 struct irc_ssaddr addr;
91 char *name;
92 struct DNSQuery *query; /* query callback for this request */
93 };
94
95 static fde_t ResolverFileDescriptor;
96 static dlink_list request_list = { NULL, NULL, 0 };
97
98 static void rem_request(struct reslist *request);
99 static struct reslist *make_request(struct DNSQuery *query);
100 static void do_query_name(struct DNSQuery *query,
101 const char* name, struct reslist *request, int);
102 static void do_query_number(struct DNSQuery *query,
103 const struct irc_ssaddr *,
104 struct reslist *request);
105 static void query_name(const char *name, int query_class, int query_type,
106 struct reslist *request);
107 static int send_res_msg(const char *buf, int len, int count);
108 static void resend_query(struct reslist *request);
109 static int proc_answer(struct reslist *request, HEADER *header, char *, char *);
110 static struct reslist *find_id(int id);
111 static struct DNSReply *make_dnsreply(struct reslist *request);
112
113 extern struct irc_ssaddr irc_nsaddr_list[IRCD_MAXNS];
114 extern int irc_nscount;
115 extern char irc_domain[HOSTLEN+1];
116
117
118 /*
119 * int
120 * res_ourserver(inp)
121 * looks up "inp" in irc_nsaddr_list[]
122 * returns:
123 * 0 : not found
124 * >0 : found
125 * author:
126 * paul vixie, 29may94
127 * revised for ircd, cryogen(stu) may03
128 */
129 static int
130 res_ourserver(const struct irc_ssaddr *inp)
131 {
132 #ifdef IPV6
133 struct sockaddr_in6 *v6;
134 struct sockaddr_in6 *v6in = (struct sockaddr_in6 *)inp;
135 #endif
136 struct sockaddr_in *v4;
137 struct sockaddr_in *v4in = (struct sockaddr_in *)inp;
138 int ns;
139
140 for (ns = 0; ns < irc_nscount; ns++)
141 {
142 const struct irc_ssaddr *srv = &irc_nsaddr_list[ns];
143 #ifdef IPV6
144 v6 = (struct sockaddr_in6 *)srv;
145 #endif
146 v4 = (struct sockaddr_in *)srv;
147
148 /* could probably just memcmp(srv, inp, srv.ss_len) here
149 * but we'll air on the side of caution - stu
150 *
151 */
152 switch (srv->ss.ss_family)
153 {
154 #ifdef IPV6
155 case AF_INET6:
156 if (srv->ss.ss_family == inp->ss.ss_family)
157 if (v6->sin6_port == v6in->sin6_port)
158 if ((memcmp(&v6->sin6_addr.s6_addr, &v6in->sin6_addr.s6_addr,
159 sizeof(struct in6_addr)) == 0) ||
160 (memcmp(&v6->sin6_addr.s6_addr, &in6addr_any,
161 sizeof(struct in6_addr)) == 0))
162 return(1);
163 break;
164 #endif
165 case AF_INET:
166 if (srv->ss.ss_family == inp->ss.ss_family)
167 if (v4->sin_port == v4in->sin_port)
168 if ((v4->sin_addr.s_addr == INADDR_ANY) ||
169 (v4->sin_addr.s_addr == v4in->sin_addr.s_addr))
170 return(1);
171 break;
172 default:
173 break;
174 }
175 }
176
177 return(0);
178 }
179
180 /*
181 * timeout_query_list - Remove queries from the list which have been
182 * there too long without being resolved.
183 */
184 static time_t
185 timeout_query_list(time_t now)
186 {
187 dlink_node *ptr;
188 dlink_node *next_ptr;
189 struct reslist *request;
190 time_t next_time = 0;
191 time_t timeout = 0;
192
193 DLINK_FOREACH_SAFE(ptr, next_ptr, request_list.head)
194 {
195 request = ptr->data;
196 timeout = request->sentat + request->timeout;
197
198 if (now >= timeout)
199 {
200 if (--request->retries <= 0)
201 {
202 (*request->query->callback)(request->query->ptr, NULL);
203 rem_request(request);
204 continue;
205 }
206 else
207 {
208 request->sentat = now;
209 request->timeout += request->timeout;
210 resend_query(request);
211 }
212 }
213
214 if ((next_time == 0) || timeout < next_time)
215 {
216 next_time = timeout;
217 }
218 }
219
220 return((next_time > now) ? next_time : (now + AR_TTL));
221 }
222
223 /*
224 * timeout_resolver - check request list
225 */
226 static void
227 timeout_resolver(void *notused)
228 {
229 timeout_query_list(CurrentTime);
230 }
231
232 /*
233 * start_resolver - do everything we need to read the resolv.conf file
234 * and initialize the resolver file descriptor if needed
235 */
236 static void
237 start_resolver(void)
238 {
239 irc_res_init();
240
241 if (!ResolverFileDescriptor.flags.open)
242 {
243 if (comm_open(&ResolverFileDescriptor, irc_nsaddr_list[0].ss.ss_family,
244 SOCK_DGRAM, 0, "Resolver socket") == -1)
245 return;
246
247 /* At the moment, the resolver FD data is global .. */
248 comm_setselect(&ResolverFileDescriptor, COMM_SELECT_READ,
249 res_readreply, NULL, 0);
250 eventAdd("timeout_resolver", timeout_resolver, NULL, 1);
251 }
252 }
253
254 /*
255 * init_resolver - initialize resolver and resolver library
256 */
257 void
258 init_resolver(void)
259 {
260 memset(&ResolverFileDescriptor, 0, sizeof(fde_t));
261 start_resolver();
262 }
263
264 /*
265 * restart_resolver - reread resolv.conf, reopen socket
266 */
267 void
268 restart_resolver(void)
269 {
270 fd_close(&ResolverFileDescriptor);
271 eventDelete(timeout_resolver, NULL); /* -ddosen */
272 start_resolver();
273 }
274
275 /*
276 * add_local_domain - Add the domain to hostname, if it is missing
277 * (as suggested by eps@TOASTER.SFSU.EDU)
278 */
279 void
280 add_local_domain(char *hname, size_t size)
281 {
282 /* try to fix up unqualified names
283 */
284 if (strchr(hname, '.') == NULL)
285 {
286 if (irc_domain[0])
287 {
288 size_t len = strlen(hname);
289
290 if ((strlen(irc_domain) + len + 2) < size)
291 {
292 hname[len++] = '.';
293 strcpy(hname + len, irc_domain);
294 }
295 }
296 }
297 }
298
299 /*
300 * rem_request - remove a request from the list.
301 * This must also free any memory that has been allocated for
302 * temporary storage of DNS results.
303 */
304 static void
305 rem_request(struct reslist *request)
306 {
307 dlinkDelete(&request->node, &request_list);
308 MyFree(request->name);
309 MyFree(request);
310 }
311
312 /*
313 * make_request - Create a DNS request record for the server.
314 */
315 static struct reslist *
316 make_request(struct DNSQuery* query)
317 {
318 struct reslist *request;
319
320 request = (struct reslist *)MyMalloc(sizeof(struct reslist));
321
322 request->sentat = CurrentTime;
323 request->retries = 3;
324 request->resend = 1;
325 request->timeout = 4; /* start at 4 and exponential inc. */
326 request->query = query;
327 request->state = REQ_IDLE;
328
329 dlinkAdd(request, &request->node, &request_list);
330 return(request);
331 }
332
333 /*
334 * delete_resolver_queries - cleanup outstanding queries
335 * for which there no longer exist clients or conf lines.
336 */
337 void
338 delete_resolver_queries(const struct DNSQuery *query)
339 {
340 dlink_node *ptr;
341 dlink_node *next_ptr;
342 struct reslist *request;
343
344 DLINK_FOREACH_SAFE(ptr, next_ptr, request_list.head)
345 {
346 if ((request = ptr->data) != NULL)
347 {
348 if (query == request->query)
349 rem_request(request);
350 }
351 }
352 }
353
354 /*
355 * send_res_msg - sends msg to all nameservers found in the "_res" structure.
356 * This should reflect /etc/resolv.conf. We will get responses
357 * which arent needed but is easier than checking to see if nameserver
358 * isnt present. Returns number of messages successfully sent to
359 * nameservers or -1 if no successful sends.
360 */
361 static int
362 send_res_msg(const char *msg, int len, int rcount)
363 {
364 int i;
365 int sent = 0;
366 int max_queries = IRCD_MIN(irc_nscount, rcount);
367
368 /* RES_PRIMARY option is not implemented
369 * if (res.options & RES_PRIMARY || 0 == max_queries)
370 */
371 if (max_queries == 0)
372 max_queries = 1;
373
374 for (i = 0; i < max_queries; i++)
375 {
376 if (sendto(ResolverFileDescriptor.fd, msg, len, 0,
377 (struct sockaddr*)&(irc_nsaddr_list[i]),
378 irc_nsaddr_list[i].ss_len) == len)
379 ++sent;
380 }
381
382 return(sent);
383 }
384
385 /*
386 * find_id - find a dns request id (id is determined by dn_mkquery)
387 */
388 static struct reslist *
389 find_id(int id)
390 {
391 dlink_node *ptr;
392 struct reslist *request;
393
394 DLINK_FOREACH(ptr, request_list.head)
395 {
396 request = ptr->data;
397
398 if (request->id == id)
399 return(request);
400 }
401
402 return(NULL);
403 }
404
405 /*
406 * gethost_byname_type - get host address from name
407 *
408 */
409 void
410 gethost_byname_type(const char *name, struct DNSQuery *query, int type)
411 {
412 assert(name != 0);
413 do_query_name(query, name, NULL, type);
414 }
415
416 /*
417 * gethost_byname - wrapper for _type - send T_AAAA first if IPV6 supported
418 */
419 void
420 gethost_byname(const char *name, struct DNSQuery *query)
421 {
422 #ifdef IPV6
423 gethost_byname_type(name, query, T_AAAA);
424 #else
425 gethost_byname_type(name, query, T_A);
426 #endif
427 }
428
429 /*
430 * gethost_byaddr - get host name from address
431 */
432 void
433 gethost_byaddr(const struct irc_ssaddr *addr, struct DNSQuery *query)
434 {
435 do_query_number(query, addr, NULL);
436 }
437
438 /*
439 * do_query_name - nameserver lookup name
440 */
441 static void
442 do_query_name(struct DNSQuery *query, const char *name,
443 struct reslist *request, int type)
444 {
445 char host_name[HOSTLEN + 1];
446
447 strlcpy(host_name, name, HOSTLEN);
448 add_local_domain(host_name, HOSTLEN);
449
450 if (request == NULL)
451 {
452 request = make_request(query);
453 request->name = (char *)MyMalloc(strlen(host_name) + 1);
454 request->type = type;
455 strcpy(request->name, host_name);
456 #ifdef IPV6
457 if (type != T_A)
458 request->state = REQ_AAAA;
459 else
460 #endif
461 request->state = REQ_A;
462 }
463
464 request->type = type;
465 query_name(host_name, C_IN, type, request);
466 }
467
468 /*
469 * do_query_number - Use this to do reverse IP# lookups.
470 */
471 static void
472 do_query_number(struct DNSQuery *query, const struct irc_ssaddr *addr,
473 struct reslist *request)
474 {
475 char ipbuf[128];
476 const unsigned char *cp;
477 #ifdef IPV6
478 const char *intarpa;
479 #endif
480 if (addr->ss.ss_family == AF_INET)
481 {
482 struct sockaddr_in *v4 = (struct sockaddr_in *)addr;
483 cp = (const unsigned char*)&v4->sin_addr.s_addr;
484
485 ircsprintf(ipbuf, "%u.%u.%u.%u.in-addr.arpa.",
486 (unsigned int)(cp[3]), (unsigned int)(cp[2]),
487 (unsigned int)(cp[1]), (unsigned int)(cp[0]));
488 }
489 #ifdef IPV6
490 else if (addr->ss.ss_family == AF_INET6)
491 {
492 struct sockaddr_in6 *v6 = (struct sockaddr_in6 *)addr;
493 cp = (const unsigned char *)&v6->sin6_addr.s6_addr;
494
495 if (request != NULL && request->state == REQ_INT)
496 intarpa = "int";
497 else
498 intarpa = "arpa";
499
500 (void)sprintf(ipbuf, "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x."
501 "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.ip6.%s.",
502 (unsigned int)(cp[15]&0xf), (unsigned int)(cp[15]>>4),
503 (unsigned int)(cp[14]&0xf), (unsigned int)(cp[14]>>4),
504 (unsigned int)(cp[13]&0xf), (unsigned int)(cp[13]>>4),
505 (unsigned int)(cp[12]&0xf), (unsigned int)(cp[12]>>4),
506 (unsigned int)(cp[11]&0xf), (unsigned int)(cp[11]>>4),
507 (unsigned int)(cp[10]&0xf), (unsigned int)(cp[10]>>4),
508 (unsigned int)(cp[9]&0xf), (unsigned int)(cp[9]>>4),
509 (unsigned int)(cp[8]&0xf), (unsigned int)(cp[8]>>4),
510 (unsigned int)(cp[7]&0xf), (unsigned int)(cp[7]>>4),
511 (unsigned int)(cp[6]&0xf), (unsigned int)(cp[6]>>4),
512 (unsigned int)(cp[5]&0xf), (unsigned int)(cp[5]>>4),
513 (unsigned int)(cp[4]&0xf), (unsigned int)(cp[4]>>4),
514 (unsigned int)(cp[3]&0xf), (unsigned int)(cp[3]>>4),
515 (unsigned int)(cp[2]&0xf), (unsigned int)(cp[2]>>4),
516 (unsigned int)(cp[1]&0xf), (unsigned int)(cp[1]>>4),
517 (unsigned int)(cp[0]&0xf), (unsigned int)(cp[0]>>4), intarpa);
518 }
519 #endif
520 if (request == NULL)
521 {
522 request = make_request(query);
523 request->type = T_PTR;
524 memcpy(&request->addr, addr, sizeof(struct irc_ssaddr));
525 request->name = (char *)MyMalloc(HOSTLEN + 1);
526 }
527
528 query_name(ipbuf, C_IN, T_PTR, request);
529 }
530
531 /*
532 * query_name - generate a query based on class, type and name.
533 */
534 static void
535 query_name(const char *name, int query_class, int type,
536 struct reslist *request)
537 {
538 char buf[MAXPACKET];
539 int request_len = 0;
540
541 memset(buf, 0, sizeof(buf));
542
543 if ((request_len = irc_res_mkquery(name, query_class, type,
544 (unsigned char *)buf, sizeof(buf))) > 0)
545 {
546 HEADER *header = (HEADER *)buf;
547
548 /*
549 * generate an unique id
550 * NOTE: we don't have to worry about converting this to and from
551 * network byte order, the nameserver does not interpret this value
552 * and returns it unchanged
553 */
554 do
555 header->id = (header->id + genrand_int32()) & 0xffff;
556 while (find_id(header->id));
557
558 request->id = header->id;
559 ++request->sends;
560
561 request->sent += send_res_msg(buf, request_len, request->sends);
562 }
563 }
564
565 static void
566 resend_query(struct reslist *request)
567 {
568 if (request->resend == 0)
569 return;
570
571 switch (request->type)
572 {
573 case T_PTR:
574 do_query_number(NULL, &request->addr, request);
575 break;
576 case T_A:
577 do_query_name(NULL, request->name, request, request->type);
578 break;
579 #ifdef IPV6
580 case T_AAAA:
581 /* didnt work, try A */
582 if (request->state == REQ_AAAA)
583 do_query_name(NULL, request->name, request, T_A);
584 #endif
585 default:
586 break;
587 }
588 }
589
590 /*
591 * proc_answer - process name server reply
592 */
593 static int
594 proc_answer(struct reslist *request, HEADER* header, char* buf, char* eob)
595 {
596 char hostbuf[HOSTLEN + 100]; /* working buffer */
597 unsigned char *current; /* current position in buf */
598 int query_class; /* answer class */
599 int type; /* answer type */
600 int n; /* temp count */
601 int rd_length;
602 struct sockaddr_in *v4; /* conversion */
603 #ifdef IPV6
604 struct sockaddr_in6 *v6;
605 #endif
606 current = (unsigned char *)buf + sizeof(HEADER);
607
608 for (; header->qdcount > 0; --header->qdcount)
609 {
610 if ((n = irc_dn_skipname(current, (unsigned char *)eob)) < 0)
611 break;
612
613 current += (size_t) n + QFIXEDSZ;
614 }
615
616 /*
617 * process each answer sent to us blech.
618 */
619 while (header->ancount > 0 && (char *)current < eob)
620 {
621 header->ancount--;
622
623 n = irc_dn_expand((unsigned char *)buf, (unsigned char *)eob, current,
624 hostbuf, sizeof(hostbuf));
625
626 if (n < 0)
627 {
628 /*
629 * broken message
630 */
631 return(0);
632 }
633 else if (n == 0)
634 {
635 /*
636 * no more answers left
637 */
638 return(0);
639 }
640
641 hostbuf[HOSTLEN] = '\0';
642
643 /* With Address arithmetic you have to be very anal
644 * this code was not working on alpha due to that
645 * (spotted by rodder/jailbird/dianora)
646 */
647 current += (size_t) n;
648
649 if (!(((char *)current + ANSWER_FIXED_SIZE) < eob))
650 break;
651
652 type = irc_ns_get16(current);
653 current += TYPE_SIZE;
654
655 query_class = irc_ns_get16(current);
656 current += CLASS_SIZE;
657
658 request->ttl = irc_ns_get32(current);
659 current += TTL_SIZE;
660
661 rd_length = irc_ns_get16(current);
662 current += RDLENGTH_SIZE;
663
664 /*
665 * Wait to set request->type until we verify this structure
666 */
667 switch (type)
668 {
669 case T_A:
670 if (request->type != T_A)
671 return(0);
672
673 /*
674 * check for invalid rd_length or too many addresses
675 */
676 if (rd_length != sizeof(struct in_addr))
677 return(0);
678 v4 = (struct sockaddr_in *)&request->addr;
679 request->addr.ss_len = sizeof(struct sockaddr_in);
680 v4->sin_family = AF_INET;
681 memcpy(&v4->sin_addr, current, sizeof(struct in_addr));
682 return(1);
683 break;
684 #ifdef IPV6
685 case T_AAAA:
686 if (request->type != T_AAAA)
687 return(0);
688 if (rd_length != sizeof(struct in6_addr))
689 return(0);
690 request->addr.ss_len = sizeof(struct sockaddr_in6);
691 v6 = (struct sockaddr_in6 *)&request->addr;
692 v6->sin6_family = AF_INET6;
693 memcpy(&v6->sin6_addr, current, sizeof(struct in6_addr));
694 return(1);
695 break;
696 #endif
697 case T_PTR:
698 if (request->type != T_PTR)
699 return(0);
700 n = irc_dn_expand((unsigned char *)buf, (unsigned char *)eob,
701 current, hostbuf, sizeof(hostbuf));
702 if (n < 0)
703 return(0); /* broken message */
704 else if (n == 0)
705 return(0); /* no more answers left */
706
707 strlcpy(request->name, hostbuf, HOSTLEN);
708
709 return(1);
710 break;
711 case T_CNAME: /* first check we already havent started looking
712 into a cname */
713 if (request->type != T_PTR)
714 return(0);
715
716 if (request->state == REQ_CNAME)
717 {
718 n = irc_dn_expand((unsigned char *)buf, (unsigned char *)eob,
719 current, hostbuf, sizeof(hostbuf));
720
721 if (n < 0)
722 return(0);
723 return(1);
724 }
725
726 request->state = REQ_CNAME;
727 current += rd_length;
728 break;
729
730 default:
731 /* XXX I'd rather just throw away the entire bogus thing
732 * but its possible its just a broken nameserver with still
733 * valid answers. But lets do some rudimentary logging for now...
734 */
735 ilog(L_ERROR, "irc_res.c bogus type %d", type);
736 break;
737 }
738 }
739
740 return(1);
741 }
742
743 /*
744 * res_readreply - read a dns reply from the nameserver and process it.
745 */
746 static void
747 res_readreply(fde_t *fd, void *data)
748 {
749 char buf[sizeof(HEADER) + MAXPACKET]
750 /* Sparc and alpha need 16bit-alignment for accessing header->id
751 * (which is uint16_t). Because of the header = (HEADER*) buf;
752 * lateron, this is neeeded. --FaUl
753 */
754 #if defined(__sparc__) || defined(__alpha__)
755 __attribute__((aligned (16)))
756 #endif
757 ;
758 HEADER *header;
759 struct reslist *request = NULL;
760 struct DNSReply *reply = NULL;
761 int rc;
762 int answer_count;
763 socklen_t len = sizeof(struct irc_ssaddr);
764 struct irc_ssaddr lsin;
765
766 rc = recvfrom(fd->fd, buf, sizeof(buf), 0, (struct sockaddr *)&lsin, &len);
767
768 /* Re-schedule a read *after* recvfrom, or we'll be registering
769 * interest where it'll instantly be ready for read :-) -- adrian
770 */
771 comm_setselect(fd, COMM_SELECT_READ, res_readreply, NULL, 0);
772
773 /* Better to cast the sizeof instead of rc */
774 if (rc <= (int)(sizeof(HEADER)))
775 return;
776
777 /*
778 * convert DNS reply reader from Network byte order to CPU byte order.
779 */
780 header = (HEADER *)buf;
781 header->ancount = ntohs(header->ancount);
782 header->qdcount = ntohs(header->qdcount);
783 header->nscount = ntohs(header->nscount);
784 header->arcount = ntohs(header->arcount);
785
786 /*
787 * response for an id which we have already received an answer for
788 * just ignore this response.
789 */
790 if (0 == (request = find_id(header->id)))
791 return;
792
793 /*
794 * check against possibly fake replies
795 */
796 if (!res_ourserver(&lsin))
797 return;
798
799 if ((header->rcode != NO_ERRORS) || (header->ancount == 0))
800 {
801 if (header->rcode == SERVFAIL || header->rcode == NXDOMAIN)
802 {
803 /*
804 * If a bad error was returned, stop here and don't
805 * send any more (no retries granted).
806 */
807 (*request->query->callback)(request->query->ptr, NULL);
808 rem_request(request);
809 }
810 #ifdef IPV6
811 else
812 {
813 /*
814 * If we havent already tried this, and we're looking up AAAA, try A
815 * now
816 */
817 if (request->state == REQ_AAAA && request->type == T_AAAA)
818 {
819 request->timeout += 4;
820 resend_query(request);
821 }
822 else if (request->type == T_PTR && request->state != REQ_INT &&
823 request->addr.ss.ss_family == AF_INET6)
824 {
825 request->state = REQ_INT;
826 request->timeout += 4;
827 request->retries--;
828 resend_query(request);
829 }
830 }
831 #endif
832
833 return;
834 }
835
836 /*
837 * If this fails there was an error decoding the received packet,
838 * try it again and hope it works the next time.
839 */
840 answer_count = proc_answer(request, header, buf, buf + rc);
841
842 if (answer_count)
843 {
844 if (request->type == T_PTR)
845 {
846 if (request->name == NULL)
847 {
848 /*
849 * got a PTR response with no name, something bogus is happening
850 * don't bother trying again, the client address doesn't resolve
851 */
852 (*request->query->callback)(request->query->ptr, reply);
853 rem_request(request);
854 return;
855 }
856
857 /*
858 * Lookup the 'authoritative' name that we were given for the
859 * ip#.
860 *
861 */
862 #ifdef IPV6
863 if (request->addr.ss.ss_family == AF_INET6)
864 gethost_byname_type(request->name, request->query, T_AAAA);
865 else
866 #endif
867 gethost_byname_type(request->name, request->query, T_A);
868 rem_request(request);
869 }
870 else
871 {
872 /*
873 * got a name and address response, client resolved
874 */
875 reply = make_dnsreply(request);
876 (*request->query->callback)(request->query->ptr, reply);
877 MyFree(reply);
878 rem_request(request);
879 }
880 }
881 else if (!request->sent)
882 {
883 /* XXX - we got a response for a query we didn't send with a valid id?
884 * this should never happen, bail here and leave the client unresolved
885 */
886 assert(0);
887
888 /* XXX don't leak it */
889 rem_request(request);
890 }
891 }
892
893 static struct DNSReply *
894 make_dnsreply(struct reslist *request)
895 {
896 struct DNSReply *cp;
897 assert(request != 0);
898
899 cp = (struct DNSReply *)MyMalloc(sizeof(struct DNSReply));
900
901 cp->h_name = request->name;
902 memcpy(&cp->addr, &request->addr, sizeof(cp->addr));
903 return(cp);
904 }
905
906 void
907 report_dns_servers(struct Client *source_p)
908 {
909 int i;
910 char ipaddr[HOSTIPLEN];
911
912 for (i = 0; i < irc_nscount; i++)
913 {
914 irc_getnameinfo((struct sockaddr *)&(irc_nsaddr_list[i]),
915 irc_nsaddr_list[i].ss_len, ipaddr, HOSTIPLEN, NULL, 0,
916 NI_NUMERICHOST);
917 sendto_one(source_p, form_str(RPL_STATSALINE),
918 me.name, source_p->name, ipaddr);
919 }
920 }

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