src/res.c

   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: res.c 3301 2007-03-28 15:04:06Z jilles $
  11  * from Hybrid Id: res.c 459 2006-02-12 22:21:37Z db $
  12  *
  13  * July 1999 - Rewrote a bunch of stuff here. Change hostent builder code,
  14  *     added callbacks and reference counting of returned hostents.
  15  *     --Bleep (Thomas Helvey <tomh@inxpress.net>)
  16  *
  17  * This was all needlessly complicated for irc. Simplified. No more hostent
  18  * All we really care about is the IP -> hostname mappings. Thats all.
  19  *
  20  * Apr 28, 2003 --cryogen and Dianora
  21  *
  22  * DNS server flooding lessened, AAAA-or-A lookup removed, ip6.int support
  23  * removed, various robustness fixes
  24  *
  25  * 2006 --jilles and nenolod
  26  *
  27  * Resend queries to other servers if the DNS server replies with an error or
  28  * an invalid response. Also, avoid servers that return errors or invalid
  29  * responses.
  30  *
  31  * October 2012 --mr_flea
  32  */
  33
  34 #include "stdinc.h"
  35 #include "ircd_defs.h"
  36 #include "common.h"
  37 #include "ircd.h"
  38 #include "res.h"
  39 #include "reslib.h"
  40 #include "match.h"
  41 #include "numeric.h"
  42 #include "client.h" /* SNO_* */
  43 #include "s_assert.h"
  44 #include "logger.h"
  45 #include "send.h"
  46
  47 #if (CHAR_BIT != 8)
  48 #error this code needs to be able to address individual octets
  49 #endif
  50
  51 static PF res_readreply;
  52
  53 #define MAXPACKET      1024     /* rfc sez 512 but we expand names so ... */
  54 #define RES_MAXALIASES 35       /* maximum aliases allowed */
  55 #define RES_MAXADDRS   35       /* maximum addresses allowed */
  56 #define AR_TTL         600      /* TTL in seconds for dns cache entries */
  57
  58 /* RFC 1104/1105 wasn't very helpful about what these fields
  59  * should be named, so for now, we'll just name them this way.
  60  * we probably should look at what named calls them or something.
  61  */
  62 #define TYPE_SIZE         (size_t)2
  63 #define CLASS_SIZE        (size_t)2
  64 #define TTL_SIZE          (size_t)4
  65 #define RDLENGTH_SIZE     (size_t)2
  66 #define ANSWER_FIXED_SIZE (TYPE_SIZE + CLASS_SIZE + TTL_SIZE + RDLENGTH_SIZE)
  67
  68 struct reslist
  69 {
  70         rb_dlink_node node;
  71         int id;
  72         time_t ttl;
  73         char type;
  74         char queryname[IRCD_RES_HOSTLEN + 1]; /* name currently being queried */
  75         char retries;           /* retry counter */
  76         char sends;             /* number of sends (>1 means resent) */
  77         time_t sentat;
  78         time_t timeout;
  79         unsigned int lastns;    /* index of last server sent to */
  80         struct rb_sockaddr_storage addr;
  81         char *name;
  82         struct DNSQuery *query; /* query callback for this request */
  83 };
  84
  85 static rb_fde_t *res_fd;
  86 static rb_dlink_list request_list = { NULL, NULL, 0 };
  87 static int ns_failure_count[IRCD_MAXNS]; /* timeouts and invalid/failed replies */
  88
  89 static void rem_request(struct reslist *request);
  90 static struct reslist *make_request(struct DNSQuery *query);
  91 static void do_query_name(struct DNSQuery *query, const char *name, struct reslist *request, int);
  92 static void do_query_number(struct DNSQuery *query, const struct rb_sockaddr_storage *,
  93                             struct reslist *request);
  94 static void query_name(struct reslist *request);
  95 static int send_res_msg(const char *buf, int len, int count);
  96 static void resend_query(struct reslist *request);
  97 static int check_question(struct reslist *request, HEADER * header, char *buf, char *eob);
  98 static int proc_answer(struct reslist *request, HEADER * header, char *, char *);
  99 static struct reslist *find_id(int id);
 100 static struct DNSReply *make_dnsreply(struct reslist *request);
 101
 102 /*
 103  * int
 104  * res_ourserver(inp)
 105  *      looks up "inp" in irc_nsaddr_list[]
 106  * returns:
 107  *      server ID or -1 for not found
 108  * author:
 109  *      paul vixie, 29may94
 110  *      revised for ircd, cryogen(stu) may03
 111  *      slightly modified for charybdis, mr_flea oct12
 112  */
 113 static int res_ourserver(const struct rb_sockaddr_storage *inp)
 114 {
 115 #ifdef RB_IPV6
 116         const struct sockaddr_in6 *v6;
 117         const struct sockaddr_in6 *v6in = (const struct sockaddr_in6 *)inp;
 118 #endif
 119         const struct sockaddr_in *v4;
 120         const struct sockaddr_in *v4in = (const struct sockaddr_in *)inp;
 121         int ns;
 122
 123         for (ns = 0; ns < irc_nscount; ns++)
 124         {
 125                 const struct rb_sockaddr_storage *srv = &irc_nsaddr_list[ns];
 126
 127                 if (srv->ss_family != inp->ss_family)
 128                         continue;
 129
 130 #ifdef RB_IPV6
 131                 v6 = (const struct sockaddr_in6 *)srv;
 132 #endif
 133                 v4 = (const struct sockaddr_in *)srv;
 134
 135                 /* could probably just memcmp(srv, inp, srv.ss_len) here
 136                  * but we'll err on the side of caution - stu
 137                  */
 138                 switch (srv->ss_family)
 139                 {
 140 #ifdef RB_IPV6
 141                         case AF_INET6:
 142                                 if (v6->sin6_port == v6in->sin6_port)
 143                                         if ((memcmp(&v6->sin6_addr.s6_addr, &v6in->sin6_addr.s6_addr,
 144                                                                         sizeof(struct in6_addr)) == 0) ||
 145                                                         (memcmp(&v6->sin6_addr.s6_addr, &in6addr_any,
 146                                                                         sizeof(struct in6_addr)) == 0))
 147                                         {
 148                                                 return ns;
 149                                         }
 150                                 break;
 151 #endif
 152                         case AF_INET:
 153                                 if (v4->sin_port == v4in->sin_port)
 154                                         if ((v4->sin_addr.s_addr == INADDR_ANY)
 155                                                         || (v4->sin_addr.s_addr == v4in->sin_addr.s_addr))
 156                                         {
 157                                                 return ns;
 158                                         }
 159                                 break;
 160                         default:
 161                                 break;
 162                 }
 163         }
 164
 165         return -1;
 166 }
 167
 168 /*
 169  * timeout_query_list - Remove queries from the list which have been
 170  * there too long without being resolved.
 171  */
 172 static time_t timeout_query_list(time_t now)
 173 {
 174         rb_dlink_node *ptr;
 175         rb_dlink_node *next_ptr;
 176         struct reslist *request;
 177         time_t next_time = 0;
 178         time_t timeout = 0;
 179
 180         RB_DLINK_FOREACH_SAFE(ptr, next_ptr, request_list.head)
 181         {
 182                 request = ptr->data;
 183                 timeout = request->sentat + request->timeout;
 184
 185                 if (now >= timeout)
 186                 {
 187                         ns_failure_count[request->lastns]++;
 188                         request->sentat = now;
 189                         request->timeout += request->timeout;
 190                         resend_query(request);
 191                 }
 192
 193                 if ((next_time == 0) || timeout < next_time)
 194                 {
 195                         next_time = timeout;
 196                 }
 197         }
 198
 199         return (next_time > now) ? next_time : (now + AR_TTL);
 200 }
 201
 202 /*
 203  * timeout_resolver - check request list
 204  */
 205 static void timeout_resolver(void *notused)
 206 {
 207         timeout_query_list(rb_current_time());
 208 }
 209
 210 static struct ev_entry *timeout_resolver_ev = NULL;
 211
 212 /*
 213  * start_resolver - do everything we need to read the resolv.conf file
 214  * and initialize the resolver file descriptor if needed
 215  */
 216 static void start_resolver(void)
 217 {
 218         int i;
 219
 220         irc_res_init();
 221         for (i = 0; i < irc_nscount; i++)
 222                 ns_failure_count[i] = 0;
 223
 224         if (res_fd == NULL)
 225         {
 226                 if ((res_fd = rb_socket(irc_nsaddr_list[0].ss_family, SOCK_DGRAM, 0,
 227                                "UDP resolver socket")) == NULL)
 228                         return;
 229
 230                 /* At the moment, the resolver FD data is global .. */
 231                 rb_setselect(res_fd, RB_SELECT_READ, res_readreply, NULL);
 232                 timeout_resolver_ev = rb_event_add("timeout_resolver", timeout_resolver, NULL, 1);
 233         }
 234 }
 235
 236 /*
 237  * init_resolver - initialize resolver and resolver library
 238  */
 239 void init_resolver(void)
 240 {
 241 #ifdef HAVE_SRAND48
 242         srand48(rb_current_time());
 243 #endif
 244         start_resolver();
 245 }
 246
 247 /*
 248  * restart_resolver - reread resolv.conf, reopen socket
 249  */
 250 void restart_resolver(void)
 251 {
 252         rb_close(res_fd);
 253         res_fd = NULL;
 254         rb_event_delete(timeout_resolver_ev);   /* -ddosen */
 255         start_resolver();
 256 }
 257
 258 /*
 259  * add_local_domain - Add the domain to hostname, if it is missing
 260  * (as suggested by eps@TOASTER.SFSU.EDU)
 261  */
 262 void add_local_domain(char *hname, size_t size)
 263 {
 264         /* try to fix up unqualified names */
 265         if (strchr(hname, '.') == NULL)
 266         {
 267                 if (irc_domain[0])
 268                 {
 269                         size_t len = strlen(hname);
 270
 271                         if ((strlen(irc_domain) + len + 2) < size)
 272                         {
 273                                 hname[len++] = '.';
 274                                 strcpy(hname + len, irc_domain);
 275                         }
 276                 }
 277         }
 278 }
 279
 280 /*
 281  * rem_request - remove a request from the list.
 282  * This must also free any memory that has been allocated for
 283  * temporary storage of DNS results.
 284  */
 285 static void rem_request(struct reslist *request)
 286 {
 287         rb_dlinkDelete(&request->node, &request_list);
 288         rb_free(request->name);
 289         rb_free(request);
 290 }
 291
 292 /*
 293  * make_request - Create a DNS request record for the server.
 294  */
 295 static struct reslist *make_request(struct DNSQuery *query)
 296 {
 297         struct reslist *request = rb_malloc(sizeof(struct reslist));
 298
 299         request->sentat = rb_current_time();
 300         request->retries = 3;
 301         request->timeout = 4;   /* start at 4 and exponential inc. */
 302         request->query = query;
 303
 304         /*
 305          * generate a unique id
 306          * NOTE: we don't have to worry about converting this to and from
 307          * network byte order, the nameserver does not interpret this value
 308          * and returns it unchanged
 309          *
 310          * we generate an id per request now (instead of per send) to allow
 311          * late replies to be used.
 312          */
 313 #ifdef HAVE_LRAND48
 314         do
 315         {
 316                 request->id = (request->id + lrand48()) & 0xffff;
 317         } while (find_id(request->id));
 318 #else
 319         int k = 0;
 320         struct timeval tv;
 321         gettimeofday(&tv, NULL);
 322         do
 323         {
 324                 request->id = (request->id + k + tv.tv_usec) & 0xffff;
 325                 k++;
 326         } while (find_id(request->id));
 327 #endif /* HAVE_LRAND48 */
 328
 329         rb_dlinkAdd(request, &request->node, &request_list);
 330
 331         return request;
 332 }
 333
 334 /*
 335  * delete_resolver_queries - cleanup outstanding queries
 336  * for which there no longer exist clients or conf lines.
 337  */
 338 void delete_resolver_queries(const struct DNSQuery *query)
 339 {
 340         rb_dlink_node *ptr;
 341         rb_dlink_node *next_ptr;
 342         struct reslist *request;
 343
 344         RB_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  * retryfreq - determine how many queries to wait before resending
 356  * if there have been that many consecutive timeouts
 357  */
 358 static int retryfreq(int timeouts)
 359 {
 360         switch (timeouts)
 361         {
 362                 case 1:
 363                         return 3;
 364                 case 2:
 365                         return 9;
 366                 case 3:
 367                         return 27;
 368                 case 4:
 369                         return 81;
 370                 default:
 371                         return 243;
 372         }
 373 }
 374
 375 /*
 376  * send_res_msg - sends msg to a nameserver.
 377  * This should reflect /etc/resolv.conf.
 378  * Returns number of nameserver successfully sent to
 379  * or -1 if no successful sends.
 380  */
 381 static int send_res_msg(const char *msg, int len, int rcount)
 382 {
 383         int i;
 384         int ns;
 385         static int retrycnt;
 386
 387         retrycnt++;
 388         /* First try a nameserver that seems to work.
 389          * Every once in a while, try a possibly broken one to check
 390          * if it is working again.
 391          */
 392         for (i = 0; i < irc_nscount; i++)
 393         {
 394                 ns = (i + rcount - 1) % irc_nscount;
 395                 if (ns_failure_count[ns] && retrycnt % retryfreq(ns_failure_count[ns]))
 396                         continue;
 397                 if (sendto(rb_get_fd(res_fd), msg, len, 0,
 398                      (struct sockaddr *)&(irc_nsaddr_list[ns]),
 399                                 GET_SS_LEN(&irc_nsaddr_list[ns])) == len)
 400                         return ns;
 401         }
 402
 403         /* No known working nameservers, try some broken one. */
 404         for (i = 0; i < irc_nscount; i++)
 405         {
 406                 ns = (i + rcount - 1) % irc_nscount;
 407                 if (!ns_failure_count[ns])
 408                         continue;
 409                 if (sendto(rb_get_fd(res_fd), msg, len, 0,
 410                      (struct sockaddr *)&(irc_nsaddr_list[ns]),
 411                                 GET_SS_LEN(&irc_nsaddr_list[ns])) == len)
 412                         return ns;
 413         }
 414
 415         return -1;
 416 }
 417
 418 /*
 419  * find_id - find a dns request id (id is determined by dn_mkquery)
 420  */
 421 static struct reslist *find_id(int id)
 422 {
 423         rb_dlink_node *ptr;
 424         struct reslist *request;
 425
 426         RB_DLINK_FOREACH(ptr, request_list.head)
 427         {
 428                 request = ptr->data;
 429
 430                 if (request->id == id)
 431                         return (request);
 432         }
 433
 434         return (NULL);
 435 }
 436
 437 /*
 438  * gethost_byname_type - get host address from name
 439  *
 440  */
 441 void gethost_byname_type(const char *name, struct DNSQuery *query, int type)
 442 {
 443         assert(name != 0);
 444         do_query_name(query, name, NULL, type);
 445 }
 446
 447 /*
 448  * gethost_byaddr - get host name from address
 449  */
 450 void gethost_byaddr(const struct rb_sockaddr_storage *addr, struct DNSQuery *query)
 451 {
 452         do_query_number(query, addr, NULL);
 453 }
 454
 455 /*
 456  * do_query_name - nameserver lookup name
 457  */
 458 static void do_query_name(struct DNSQuery *query, const char *name, struct reslist *request,
 459                           int type)
 460 {
 461         char host_name[IRCD_RES_HOSTLEN + 1];
 462
 463         rb_strlcpy(host_name, name, IRCD_RES_HOSTLEN + 1);
 464         add_local_domain(host_name, IRCD_RES_HOSTLEN);
 465
 466         if (request == NULL)
 467         {
 468                 request = make_request(query);
 469                 request->name = (char *)rb_malloc(strlen(host_name) + 1);
 470                 strcpy(request->name, host_name);
 471         }
 472
 473         rb_strlcpy(request->queryname, host_name, sizeof(request->queryname));
 474         request->type = type;
 475         query_name(request);
 476 }
 477
 478 /*
 479  * do_query_number - Use this to do reverse IP# lookups.
 480  */
 481 static void do_query_number(struct DNSQuery *query, const struct rb_sockaddr_storage *addr,
 482                             struct reslist *request)
 483 {
 484         const unsigned char *cp;
 485
 486         if (request == NULL)
 487         {
 488                 request = make_request(query);
 489                 memcpy(&request->addr, addr, sizeof(struct rb_sockaddr_storage));
 490                 request->name = (char *)rb_malloc(IRCD_RES_HOSTLEN + 1);
 491         }
 492
 493         if (addr->ss_family == AF_INET)
 494         {
 495                 const struct sockaddr_in *v4 = (const struct sockaddr_in *)addr;
 496                 cp = (const unsigned char *)&v4->sin_addr.s_addr;
 497
 498                 rb_sprintf(request->queryname, "%u.%u.%u.%u.in-addr.arpa", (unsigned int)(cp[3]),
 499                            (unsigned int)(cp[2]), (unsigned int)(cp[1]), (unsigned int)(cp[0]));
 500         }
 501 #ifdef RB_IPV6
 502         else if (addr->ss_family == AF_INET6)
 503         {
 504                 const struct sockaddr_in6 *v6 = (const struct sockaddr_in6 *)addr;
 505                 cp = (const unsigned char *)&v6->sin6_addr.s6_addr;
 506
 507                 (void)sprintf(request->queryname, "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x."
 508                               "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.ip6.arpa",
 509                               (unsigned int)(cp[15] & 0xf), (unsigned int)(cp[15] >> 4),
 510                               (unsigned int)(cp[14] & 0xf), (unsigned int)(cp[14] >> 4),
 511                               (unsigned int)(cp[13] & 0xf), (unsigned int)(cp[13] >> 4),
 512                               (unsigned int)(cp[12] & 0xf), (unsigned int)(cp[12] >> 4),
 513                               (unsigned int)(cp[11] & 0xf), (unsigned int)(cp[11] >> 4),
 514                               (unsigned int)(cp[10] & 0xf), (unsigned int)(cp[10] >> 4),
 515                               (unsigned int)(cp[9] & 0xf), (unsigned int)(cp[9] >> 4),
 516                               (unsigned int)(cp[8] & 0xf), (unsigned int)(cp[8] >> 4),
 517                               (unsigned int)(cp[7] & 0xf), (unsigned int)(cp[7] >> 4),
 518                               (unsigned int)(cp[6] & 0xf), (unsigned int)(cp[6] >> 4),
 519                               (unsigned int)(cp[5] & 0xf), (unsigned int)(cp[5] >> 4),
 520                               (unsigned int)(cp[4] & 0xf), (unsigned int)(cp[4] >> 4),
 521                               (unsigned int)(cp[3] & 0xf), (unsigned int)(cp[3] >> 4),
 522                               (unsigned int)(cp[2] & 0xf), (unsigned int)(cp[2] >> 4),
 523                               (unsigned int)(cp[1] & 0xf), (unsigned int)(cp[1] >> 4),
 524                               (unsigned int)(cp[0] & 0xf), (unsigned int)(cp[0] >> 4));
 525         }
 526 #endif
 527
 528         request->type = T_PTR;
 529         query_name(request);
 530 }
 531
 532 /*
 533  * query_name - generate a query based on class, type and name.
 534  */
 535 static void query_name(struct reslist *request)
 536 {
 537         char buf[MAXPACKET];
 538         int request_len = 0;
 539         int ns;
 540
 541         memset(buf, 0, sizeof(buf));
 542
 543         if ((request_len =
 544              irc_res_mkquery(request->queryname, C_IN, request->type, (unsigned char *)buf, sizeof(buf))) > 0)
 545         {
 546                 HEADER *header = (HEADER *) buf;
 547                 header->id = request->id;
 548                 ++request->sends;
 549
 550                 ns = send_res_msg(buf, request_len, request->sends);
 551                 if (ns != -1)
 552                         request->lastns = ns;
 553         }
 554 }
 555
 556 static void resend_query(struct reslist *request)
 557 {
 558         if (--request->retries <= 0)
 559         {
 560                 (*request->query->callback) (request->query->ptr, NULL);
 561                 rem_request(request);
 562                 return;
 563         }
 564
 565         switch (request->type)
 566         {
 567           case T_PTR:
 568                   do_query_number(NULL, &request->addr, request);
 569                   break;
 570           case T_A:
 571 #ifdef RB_IPV6
 572           case T_AAAA:
 573 #endif
 574                   do_query_name(NULL, request->name, request, request->type);
 575                   break;
 576           default:
 577                   break;
 578         }
 579 }
 580
 581 /*
 582  * check_question - check if the reply really belongs to the
 583  * name we queried (to guard against late replies from previous
 584  * queries with the same id).
 585  */
 586 static int check_question(struct reslist *request, HEADER * header, char *buf, char *eob)
 587 {
 588         char hostbuf[IRCD_RES_HOSTLEN + 1];     /* working buffer */
 589         unsigned char *current; /* current position in buf */
 590         int n;                  /* temp count */
 591
 592         current = (unsigned char *)buf + sizeof(HEADER);
 593         if (header->qdcount != 1)
 594                 return 0;
 595         n = irc_dn_expand((unsigned char *)buf, (unsigned char *)eob, current, hostbuf,
 596                           sizeof(hostbuf));
 597         if (n <= 0)
 598                 return 0;
 599         if (strcasecmp(hostbuf, request->queryname))
 600                 return 0;
 601         return 1;
 602 }
 603
 604 /*
 605  * proc_answer - process name server reply
 606  */
 607 static int proc_answer(struct reslist *request, HEADER * header, char *buf, char *eob)
 608 {
 609         char hostbuf[IRCD_RES_HOSTLEN + 100];   /* working buffer */
 610         unsigned char *current; /* current position in buf */
 611         int query_class;        /* answer class */
 612         int type;               /* answer type */
 613         int n;                  /* temp count */
 614         int rd_length;
 615         struct sockaddr_in *v4; /* conversion */
 616 #ifdef RB_IPV6
 617         struct sockaddr_in6 *v6;
 618 #endif
 619         current = (unsigned char *)buf + sizeof(HEADER);
 620
 621         for (; header->qdcount > 0; --header->qdcount)
 622         {
 623                 if ((n = irc_dn_skipname(current, (unsigned char *)eob)) < 0)
 624                         return 0;
 625
 626                 current += (size_t) n + QFIXEDSZ;
 627         }
 628
 629         /*
 630          * process each answer sent to us blech.
 631          */
 632         while (header->ancount > 0 && (char *)current < eob)
 633         {
 634                 header->ancount--;
 635
 636                 n = irc_dn_expand((unsigned char *)buf, (unsigned char *)eob, current, hostbuf,
 637                                   sizeof(hostbuf));
 638
 639                 if (n < 0)
 640                 {
 641                         /*
 642                          * broken message
 643                          */
 644                         return (0);
 645                 }
 646                 else if (n == 0)
 647                 {
 648                         /*
 649                          * no more answers left
 650                          */
 651                         return (0);
 652                 }
 653
 654                 hostbuf[IRCD_RES_HOSTLEN] = '\0';
 655
 656                 /* With Address arithmetic you have to be very anal
 657                  * this code was not working on alpha due to that
 658                  * (spotted by rodder/jailbird/dianora)
 659                  */
 660                 current += (size_t) n;
 661
 662                 if (!(((char *)current + ANSWER_FIXED_SIZE) < eob))
 663                         break;
 664
 665                 type = irc_ns_get16(current);
 666                 current += TYPE_SIZE;
 667
 668                 query_class = irc_ns_get16(current);
 669                 current += CLASS_SIZE;
 670
 671                 request->ttl = irc_ns_get32(current);
 672                 current += TTL_SIZE;
 673
 674                 rd_length = irc_ns_get16(current);
 675                 current += RDLENGTH_SIZE;
 676
 677                 /*
 678                  * Wait to set request->type until we verify this structure
 679                  */
 680                 switch (type)
 681                 {
 682                   case T_A:
 683                           if (request->type != T_A)
 684                                   return (0);
 685
 686                           /*
 687                            * check for invalid rd_length or too many addresses
 688                            */
 689                           if (rd_length != sizeof(struct in_addr))
 690                                   return (0);
 691                           v4 = (struct sockaddr_in *)&request->addr;
 692                           SET_SS_LEN(&request->addr, sizeof(struct sockaddr_in));
 693                           v4->sin_family = AF_INET;
 694                           memcpy(&v4->sin_addr, current, sizeof(struct in_addr));
 695                           return (1);
 696                           break;
 697 #ifdef RB_IPV6
 698                   case T_AAAA:
 699                           if (request->type != T_AAAA)
 700                                   return (0);
 701                           if (rd_length != sizeof(struct in6_addr))
 702                                   return (0);
 703                           SET_SS_LEN(&request->addr, sizeof(struct sockaddr_in6));
 704                           v6 = (struct sockaddr_in6 *)&request->addr;
 705                           v6->sin6_family = AF_INET6;
 706                           memcpy(&v6->sin6_addr, current, sizeof(struct in6_addr));
 707                           return (1);
 708                           break;
 709 #endif
 710                   case T_PTR:
 711                           if (request->type != T_PTR)
 712                                   return (0);
 713                           n = irc_dn_expand((unsigned char *)buf, (unsigned char *)eob, current,
 714                                             hostbuf, sizeof(hostbuf));
 715                           if (n < 0)
 716                                   return (0);   /* broken message */
 717                           else if (n == 0)
 718                                   return (0);   /* no more answers left */
 719
 720                           rb_strlcpy(request->name, hostbuf, IRCD_RES_HOSTLEN + 1);
 721
 722                           return (1);
 723                           break;
 724                   case T_CNAME:
 725                           /* real answer will follow */
 726                           current += rd_length;
 727                           break;
 728
 729                   default:
 730                           /* XXX I'd rather just throw away the entire bogus thing
 731                            * but its possible its just a broken nameserver with still
 732                            * valid answers. But lets do some rudimentary logging for now...
 733                            */
 734                           ilog(L_MAIN, "irc_res.c bogus type %d", type);
 735                           break;
 736                 }
 737         }
 738
 739         return (1);
 740 }
 741
 742 /*
 743  * res_read_single_reply - read a dns reply from the nameserver and process it.
 744  * Return value: 1 if a packet was read, 0 otherwise
 745  */
 746 static int res_read_single_reply(rb_fde_t *F, void *data)
 747 {
 748         char buf[sizeof(HEADER) + MAXPACKET]
 749                 /* Sparc and alpha need 16bit-alignment for accessing header->id
 750                  * (which is uint16_t). Because of the header = (HEADER*) buf;
 751                  * lateron, this is neeeded. --FaUl
 752                  */
 753 #if defined(__sparc__) || defined(__alpha__)
 754                 __attribute__ ((aligned(16)))
 755 #endif
 756                 ;
 757         HEADER *header;
 758         struct reslist *request = NULL;
 759         struct DNSReply *reply = NULL;
 760         int rc;
 761         int answer_count;
 762         socklen_t len = sizeof(struct rb_sockaddr_storage);
 763         struct rb_sockaddr_storage lsin;
 764         int ns;
 765
 766         rc = recvfrom(rb_get_fd(F), buf, sizeof(buf), 0, (struct sockaddr *)&lsin, &len);
 767
 768         /* No packet */
 769         if (rc == 0 || rc == -1)
 770                 return 0;
 771
 772         /* Too small */
 773         if (rc <= (int)(sizeof(HEADER)))
 774                 return 1;
 775
 776         /*
 777          * convert DNS reply reader from Network byte order to CPU byte order.
 778          */
 779         header = (HEADER *) buf;
 780         header->ancount = ntohs(header->ancount);
 781         header->qdcount = ntohs(header->qdcount);
 782         header->nscount = ntohs(header->nscount);
 783         header->arcount = ntohs(header->arcount);
 784
 785         /*
 786          * response for an id which we have already received an answer for
 787          * just ignore this response.
 788          */
 789         if (0 == (request = find_id(header->id)))
 790                 return 1;
 791
 792         /*
 793          * check against possibly fake replies
 794          */
 795         ns = res_ourserver(&lsin);
 796         if (ns == -1)
 797                 return 1;
 798
 799         if (ns != request->lastns)
 800         {
 801                 /*
 802                  * We'll accept the late reply, but penalize it a little more to make
 803                  * sure a laggy server doesn't end up favored.
 804                  */
 805                 ns_failure_count[ns] += 3;
 806         }
 807
 808
 809         if (!check_question(request, header, buf, buf + rc))
 810                 return 1;
 811
 812         if ((header->rcode != NO_ERRORS) || (header->ancount == 0))
 813         {
 814                 /*
 815                  * RFC 2136 states that in the event of a server returning SERVFAIL
 816                  * or NOTIMP, the request should be resent to the next server.
 817                  * Additionally, if the server refuses our query, resend it as well.
 818                  * -- mr_flea
 819                  */
 820                 if (SERVFAIL == header->rcode || NOTIMP == header->rcode ||
 821                                 REFUSED == header->rcode)
 822                 {
 823                         ns_failure_count[ns]++;
 824                         resend_query(request);
 825                 }
 826                 else
 827                 {
 828                         /*
 829                          * Either a fatal error was returned or no answer. Cancel the
 830                          * request.
 831                          */
 832                         if (NXDOMAIN == header->rcode)
 833                         {
 834                                 /* If the rcode is NXDOMAIN, treat it as a good response. */
 835                                 ns_failure_count[ns] /= 4;
 836                         }
 837                         (*request->query->callback) (request->query->ptr, NULL);
 838                         rem_request(request);
 839                 }
 840                 return 1;
 841         }
 842         /*
 843          * If this fails there was an error decoding the received packet.
 844          * -- jilles
 845          */
 846         answer_count = proc_answer(request, header, buf, buf + rc);
 847
 848         if (answer_count)
 849         {
 850                 if (request->type == T_PTR)
 851                 {
 852                         if (request->name == NULL)
 853                         {
 854                                 /*
 855                                  * Got a PTR response with no name, something strange is
 856                                  * happening. Try another DNS server.
 857                                  */
 858                                 ns_failure_count[ns]++;
 859                                 resend_query(request);
 860                                 return 1;
 861                         }
 862
 863                         /*
 864                          * Lookup the 'authoritative' name that we were given for the
 865                          * ip#.
 866                          */
 867 #ifdef RB_IPV6
 868                         if (request->addr.ss_family == AF_INET6)
 869                                 gethost_byname_type(request->name, request->query, T_AAAA);
 870                         else
 871 #endif
 872                                 gethost_byname_type(request->name, request->query, T_A);
 873                         rem_request(request);
 874                 }
 875                 else
 876                 {
 877                         /*
 878                          * got a name and address response, client resolved
 879                          */
 880                         reply = make_dnsreply(request);
 881                         (*request->query->callback) (request->query->ptr, reply);
 882                         rb_free(reply);
 883                         rem_request(request);
 884                 }
 885
 886                 ns_failure_count[ns] /= 4;
 887         }
 888         else
 889         {
 890                 /* Invalid or corrupt reply - try another resolver. */
 891                 ns_failure_count[ns]++;
 892                 resend_query(request);
 893         }
 894         return 1;
 895 }
 896
 897 static void res_readreply(rb_fde_t *F, void *data)
 898 {
 899         while (res_read_single_reply(F, data))
 900                 ;
 901         rb_setselect(F, RB_SELECT_READ, res_readreply, NULL);
 902 }
 903
 904 static struct DNSReply *make_dnsreply(struct reslist *request)
 905 {
 906         struct DNSReply *cp;
 907         s_assert(request != 0);
 908
 909         cp = (struct DNSReply *)rb_malloc(sizeof(struct DNSReply));
 910
 911         cp->h_name = request->name;
 912         memcpy(&cp->addr, &request->addr, sizeof(cp->addr));
 913         return (cp);
 914 }
 915
 916 void report_dns_servers(struct Client *source_p)
 917 {
 918         int i;
 919         char ipaddr[128];
 920
 921         for (i = 0; i < irc_nscount; i++)
 922         {
 923                 if (!rb_inet_ntop_sock((struct sockaddr *)&(irc_nsaddr_list[i]),
 924                                 ipaddr, sizeof ipaddr))
 925                         rb_strlcpy(ipaddr, "?", sizeof ipaddr);
 926                 sendto_one_numeric(source_p, RPL_STATSDEBUG,
 927                                 "A %s %d", ipaddr, ns_failure_count[i]);
 928         }
 929 }