authd/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  * July 1999 - Rewrote a bunch of stuff here. Change hostent builder code,
  11  *     added callbacks and reference counting of returned hostents.
  12  *     --Bleep (Thomas Helvey <tomh@inxpress.net>)
  13  *
  14  * This was all needlessly complicated for irc. Simplified. No more hostent
  15  * All we really care about is the IP -> hostname mappings. Thats all.
  16  *
  17  * Apr 28, 2003 --cryogen and Dianora
  18  *
  19  * DNS server flooding lessened, AAAA-or-A lookup removed, ip6.int support
  20  * removed, various robustness fixes
  21  *
  22  * 2006 --jilles and nenolod
  23  *
  24  * Resend queries to other servers if the DNS server replies with an error or
  25  * an invalid response. Also, avoid servers that return errors or invalid
  26  * responses.
  27  *
  28  * October 2012 --mr_flea
  29  *
  30  * ircd-ratbox changes for random IDs merged back in.
  31  *
  32  * January 2016 --kaniini
  33  */
  34
  35 #include <rb_lib.h>
  36 #include "setup.h"
  37 #include "res.h"
  38 #include "reslib.h"
  39
  40 #if (CHAR_BIT != 8)
  41 #error this code needs to be able to address individual octets
  42 #endif
  43
  44 static PF res_readreply;
  45
  46 #define MAXPACKET      1024     /* rfc sez 512 but we expand names so ... */
  47 #define RES_MAXALIASES 35       /* maximum aliases allowed */
  48 #define RES_MAXADDRS   35       /* maximum addresses allowed */
  49 #define AR_TTL         600      /* TTL in seconds for dns cache entries */
  50
  51 /* RFC 1104/1105 wasn't very helpful about what these fields
  52  * should be named, so for now, we'll just name them this way.
  53  * we probably should look at what named calls them or something.
  54  */
  55 #define TYPE_SIZE         (size_t)2
  56 #define CLASS_SIZE        (size_t)2
  57 #define TTL_SIZE          (size_t)4
  58 #define RDLENGTH_SIZE     (size_t)2
  59 #define ANSWER_FIXED_SIZE (TYPE_SIZE + CLASS_SIZE + TTL_SIZE + RDLENGTH_SIZE)
  60
  61 #ifdef RB_IPV6
  62 struct in6_addr ipv6_addr;
  63 #endif
  64 struct in_addr ipv4_addr;
  65
  66 struct reslist
  67 {
  68         rb_dlink_node node;
  69         int id;
  70         time_t ttl;
  71         char type;
  72         char queryname[IRCD_RES_HOSTLEN + 1]; /* name currently being queried */
  73         char retries;           /* retry counter */
  74         char sends;             /* number of sends (>1 means resent) */
  75         time_t sentat;
  76         time_t timeout;
  77         int lastns;     /* index of last server sent to */
  78         struct rb_sockaddr_storage addr;
  79         char *name;
  80         struct DNSQuery *query; /* query callback for this request */
  81 };
  82
  83 static rb_fde_t *res_fd;
  84 static rb_dlink_list request_list = { NULL, NULL, 0 };
  85 static int ns_failure_count[IRCD_MAXNS]; /* timeouts and invalid/failed replies */
  86
  87 static void rem_request(struct reslist *request);
  88 static struct reslist *make_request(struct DNSQuery *query);
  89 static void gethost_byname_type_fqdn(const char *name, struct DNSQuery *query,
  90                 int type);
  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 static uint16_t generate_random_id(void);
 102
 103 #ifdef RES_MIN
 104 #undef RES_MIN
 105 #endif
 106
 107 #define RES_MIN(a, b)  ((a) < (b) ? (a) : (b))
 108
 109 /*
 110  * int
 111  * res_ourserver(inp)
 112  *      looks up "inp" in irc_nsaddr_list[]
 113  * returns:
 114  *      server ID or -1 for not found
 115  * author:
 116  *      paul vixie, 29may94
 117  *      revised for ircd, cryogen(stu) may03
 118  *      slightly modified for charybdis, mr_flea oct12
 119  */
 120 static int
 121 res_ourserver(const struct rb_sockaddr_storage *inp)
 122 {
 123 #ifdef RB_IPV6
 124         const struct sockaddr_in6 *v6;
 125         const struct sockaddr_in6 *v6in = (const struct sockaddr_in6 *)inp;
 126 #endif
 127         const struct sockaddr_in *v4;
 128         const struct sockaddr_in *v4in = (const struct sockaddr_in *)inp;
 129         int ns;
 130
 131         for(ns = 0; ns < irc_nscount; ns++)
 132         {
 133                 const struct rb_sockaddr_storage *srv = &irc_nsaddr_list[ns];
 134 #ifdef RB_IPV6
 135                 v6 = (const struct sockaddr_in6 *)srv;
 136 #endif
 137                 v4 = (const struct sockaddr_in *)srv;
 138
 139                 /* could probably just memcmp(srv, inp, srv.ss_len) here
 140                  * but we'll air on the side of caution - stu
 141                  */
 142                 switch (GET_SS_FAMILY(srv))
 143                 {
 144 #ifdef RB_IPV6
 145                 case AF_INET6:
 146                         if(GET_SS_FAMILY(srv) == GET_SS_FAMILY(inp))
 147                                 if(v6->sin6_port == v6in->sin6_port)
 148                                         if((memcmp(&v6->sin6_addr.s6_addr, &v6in->sin6_addr.s6_addr,
 149                                                    sizeof(struct in6_addr)) == 0) ||
 150                                            (memcmp(&v6->sin6_addr.s6_addr, &in6addr_any,
 151                                                    sizeof(struct in6_addr)) == 0))
 152                                                 return 1;
 153                         break;
 154 #endif
 155                 case AF_INET:
 156                         if(GET_SS_FAMILY(srv) == GET_SS_FAMILY(inp))
 157                                 if(v4->sin_port == v4in->sin_port)
 158                                         if((v4->sin_addr.s_addr == INADDR_ANY)
 159                                            || (v4->sin_addr.s_addr == v4in->sin_addr.s_addr))
 160                                                 return 1;
 161                         break;
 162                 default:
 163                         break;
 164                 }
 165         }
 166
 167         return 0;
 168 }
 169
 170 /*
 171  * timeout_query_list - Remove queries from the list which have been
 172  * there too long without being resolved.
 173  */
 174 static time_t timeout_query_list(time_t now)
 175 {
 176         rb_dlink_node *ptr;
 177         rb_dlink_node *next_ptr;
 178         struct reslist *request;
 179         time_t next_time = 0;
 180         time_t timeout = 0;
 181
 182         RB_DLINK_FOREACH_SAFE(ptr, next_ptr, request_list.head)
 183         {
 184                 request = ptr->data;
 185                 timeout = request->sentat + request->timeout;
 186
 187                 if (now >= timeout)
 188                 {
 189                         ns_failure_count[request->lastns]++;
 190                         request->sentat = now;
 191                         request->timeout += request->timeout;
 192                         resend_query(request);
 193                 }
 194
 195                 if ((next_time == 0) || timeout < next_time)
 196                 {
 197                         next_time = timeout;
 198                 }
 199         }
 200
 201         return (next_time > now) ? next_time : (now + AR_TTL);
 202 }
 203
 204 /*
 205  * timeout_resolver - check request list
 206  */
 207 static void timeout_resolver(void *notused)
 208 {
 209         timeout_query_list(rb_current_time());
 210 }
 211
 212 static struct ev_entry *timeout_resolver_ev = NULL;
 213
 214 /*
 215  * start_resolver - do everything we need to read the resolv.conf file
 216  * and initialize the resolver file descriptor if needed
 217  */
 218 static void start_resolver(void)
 219 {
 220         int i;
 221
 222         irc_res_init();
 223         for (i = 0; i < irc_nscount; i++)
 224                 ns_failure_count[i] = 0;
 225
 226         if (res_fd == NULL)
 227         {
 228                 if ((res_fd = rb_socket(GET_SS_FAMILY(&irc_nsaddr_list[0]), SOCK_DGRAM, 0,
 229                                "UDP resolver socket")) == NULL)
 230                         return;
 231
 232                 /* At the moment, the resolver FD data is global .. */
 233                 rb_setselect(res_fd, RB_SELECT_READ, res_readreply, NULL);
 234                 timeout_resolver_ev = rb_event_add("timeout_resolver", timeout_resolver, NULL, 1);
 235         }
 236 }
 237
 238 /*
 239  * init_resolver - initialize resolver and resolver library
 240  */
 241 void init_resolver(void)
 242 {
 243 #ifdef HAVE_SRAND48
 244         srand48(rb_current_time());
 245 #endif
 246         start_resolver();
 247 }
 248
 249 /*
 250  * restart_resolver - reread resolv.conf, reopen socket
 251  */
 252 void restart_resolver(void)
 253 {
 254         rb_close(res_fd);
 255         res_fd = NULL;
 256         rb_event_delete(timeout_resolver_ev);   /* -ddosen */
 257         start_resolver();
 258 }
 259
 260 /*
 261  * add_local_domain - Add the domain to hostname, if it is missing
 262  * (as suggested by eps@TOASTER.SFSU.EDU)
 263  */
 264 void add_local_domain(char *hname, size_t size)
 265 {
 266         /* try to fix up unqualified names */
 267         if (strchr(hname, '.') == NULL)
 268         {
 269                 if (irc_domain[0])
 270                 {
 271                         size_t len = strlen(hname);
 272
 273                         if ((strlen(irc_domain) + len + 2) < size)
 274                         {
 275                                 hname[len++] = '.';
 276                                 strcpy(hname + len, irc_domain);
 277                         }
 278                 }
 279         }
 280 }
 281
 282 /*
 283  * rem_request - remove a request from the list.
 284  * This must also free any memory that has been allocated for
 285  * temporary storage of DNS results.
 286  */
 287 static void rem_request(struct reslist *request)
 288 {
 289         rb_dlinkDelete(&request->node, &request_list);
 290         rb_free(request->name);
 291         rb_free(request);
 292 }
 293
 294 /*
 295  * make_request - Create a DNS request record for the server.
 296  */
 297 static struct reslist *make_request(struct DNSQuery *query)
 298 {
 299         struct reslist *request = rb_malloc(sizeof(struct reslist));
 300
 301         request->sentat = rb_current_time();
 302         request->retries = 3;
 303         request->timeout = 4;   /* start at 4 and exponential inc. */
 304         request->query = query;
 305
 306         /*
 307          * generate a unique id
 308          * NOTE: we don't have to worry about converting this to and from
 309          * network byte order, the nameserver does not interpret this value
 310          * and returns it unchanged
 311          *
 312          * we generate an id per request now (instead of per send) to allow
 313          * late replies to be used.
 314          */
 315         request->id = generate_random_id();
 316
 317         rb_dlinkAdd(request, &request->node, &request_list);
 318
 319         return request;
 320 }
 321
 322 /*
 323  * retryfreq - determine how many queries to wait before resending
 324  * if there have been that many consecutive timeouts
 325  */
 326 static int retryfreq(int timeouts)
 327 {
 328         switch (timeouts)
 329         {
 330                 case 1:
 331                         return 3;
 332                 case 2:
 333                         return 9;
 334                 case 3:
 335                         return 27;
 336                 case 4:
 337                         return 81;
 338                 default:
 339                         return 243;
 340         }
 341 }
 342
 343 /*
 344  * send_res_msg - sends msg to a nameserver.
 345  * This should reflect /etc/resolv.conf.
 346  * Returns number of nameserver successfully sent to
 347  * or -1 if no successful sends.
 348  */
 349 static int send_res_msg(const char *msg, int len, int rcount)
 350 {
 351         int i;
 352         int ns;
 353         static int retrycnt;
 354
 355         retrycnt++;
 356         /* First try a nameserver that seems to work.
 357          * Every once in a while, try a possibly broken one to check
 358          * if it is working again.
 359          */
 360         for (i = 0; i < irc_nscount; i++)
 361         {
 362                 ns = (i + rcount - 1) % irc_nscount;
 363                 if (ns_failure_count[ns] && retrycnt % retryfreq(ns_failure_count[ns]))
 364                         continue;
 365                 if (sendto(rb_get_fd(res_fd), msg, len, 0,
 366                      (struct sockaddr *)&(irc_nsaddr_list[ns]),
 367                                 GET_SS_LEN(&irc_nsaddr_list[ns])) == len)
 368                         return ns;
 369         }
 370
 371         /* No known working nameservers, try some broken one. */
 372         for (i = 0; i < irc_nscount; i++)
 373         {
 374                 ns = (i + rcount - 1) % irc_nscount;
 375                 if (!ns_failure_count[ns])
 376                         continue;
 377                 if (sendto(rb_get_fd(res_fd), msg, len, 0,
 378                      (struct sockaddr *)&(irc_nsaddr_list[ns]),
 379                                 GET_SS_LEN(&irc_nsaddr_list[ns])) == len)
 380                         return ns;
 381         }
 382
 383         return -1;
 384 }
 385
 386 /*
 387  * find_id - find a dns request id (id is determined by dn_mkquery)
 388  */
 389 static struct reslist *find_id(int id)
 390 {
 391         rb_dlink_node *ptr;
 392         struct reslist *request;
 393
 394         RB_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 static uint16_t
 406 generate_random_id(void)
 407 {
 408         uint16_t id;
 409
 410         do
 411         {
 412                 rb_get_random(&id, sizeof(id));
 413                 if(id == 0xffff)
 414                         continue;
 415         }
 416         while(find_id(id));
 417         return id;
 418 }
 419
 420 /*
 421  * gethost_byname_type - get host address from name, adding domain if needed
 422  */
 423 void gethost_byname_type(const char *name, struct DNSQuery *query, int type)
 424 {
 425         char fqdn[IRCD_RES_HOSTLEN + 1];
 426         assert(name != 0);
 427
 428         rb_strlcpy(fqdn, name, sizeof fqdn);
 429         add_local_domain(fqdn, IRCD_RES_HOSTLEN);
 430         gethost_byname_type_fqdn(fqdn, query, type);
 431 }
 432
 433 /*
 434  * gethost_byname_type_fqdn - get host address from fqdn
 435  */
 436 static void gethost_byname_type_fqdn(const char *name, struct DNSQuery *query,
 437                 int type)
 438 {
 439         assert(name != 0);
 440         do_query_name(query, name, NULL, type);
 441 }
 442
 443 /*
 444  * gethost_byaddr - get host name from address
 445  */
 446 void gethost_byaddr(const struct rb_sockaddr_storage *addr, struct DNSQuery *query)
 447 {
 448         do_query_number(query, addr, NULL);
 449 }
 450
 451 /*
 452  * do_query_name - nameserver lookup name
 453  */
 454 static void do_query_name(struct DNSQuery *query, const char *name, struct reslist *request,
 455                           int type)
 456 {
 457         if (request == NULL)
 458         {
 459                 request = make_request(query);
 460                 request->name = rb_strdup(name);
 461         }
 462
 463         rb_strlcpy(request->queryname, name, sizeof(request->queryname));
 464         request->type = type;
 465         query_name(request);
 466 }
 467
 468 /*
 469  * do_query_number - Use this to do reverse IP# lookups.
 470  */
 471 static void do_query_number(struct DNSQuery *query, const struct rb_sockaddr_storage *addr,
 472                             struct reslist *request)
 473 {
 474         const unsigned char *cp;
 475
 476         if (request == NULL)
 477         {
 478                 request = make_request(query);
 479                 memcpy(&request->addr, addr, sizeof(struct rb_sockaddr_storage));
 480                 request->name = (char *)rb_malloc(IRCD_RES_HOSTLEN + 1);
 481         }
 482
 483         if (GET_SS_FAMILY(addr) == AF_INET)
 484         {
 485                 const struct sockaddr_in *v4 = (const struct sockaddr_in *)addr;
 486                 cp = (const unsigned char *)&v4->sin_addr.s_addr;
 487
 488                 sprintf(request->queryname, "%u.%u.%u.%u.in-addr.arpa", (unsigned int)(cp[3]),
 489                            (unsigned int)(cp[2]), (unsigned int)(cp[1]), (unsigned int)(cp[0]));
 490         }
 491 #ifdef RB_IPV6
 492         else if (GET_SS_FAMILY(addr) == AF_INET6)
 493         {
 494                 const struct sockaddr_in6 *v6 = (const struct sockaddr_in6 *)addr;
 495                 cp = (const unsigned char *)&v6->sin6_addr.s6_addr;
 496
 497                 (void)sprintf(request->queryname, "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x."
 498                               "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.ip6.arpa",
 499                               (unsigned int)(cp[15] & 0xf), (unsigned int)(cp[15] >> 4),
 500                               (unsigned int)(cp[14] & 0xf), (unsigned int)(cp[14] >> 4),
 501                               (unsigned int)(cp[13] & 0xf), (unsigned int)(cp[13] >> 4),
 502                               (unsigned int)(cp[12] & 0xf), (unsigned int)(cp[12] >> 4),
 503                               (unsigned int)(cp[11] & 0xf), (unsigned int)(cp[11] >> 4),
 504                               (unsigned int)(cp[10] & 0xf), (unsigned int)(cp[10] >> 4),
 505                               (unsigned int)(cp[9] & 0xf), (unsigned int)(cp[9] >> 4),
 506                               (unsigned int)(cp[8] & 0xf), (unsigned int)(cp[8] >> 4),
 507                               (unsigned int)(cp[7] & 0xf), (unsigned int)(cp[7] >> 4),
 508                               (unsigned int)(cp[6] & 0xf), (unsigned int)(cp[6] >> 4),
 509                               (unsigned int)(cp[5] & 0xf), (unsigned int)(cp[5] >> 4),
 510                               (unsigned int)(cp[4] & 0xf), (unsigned int)(cp[4] >> 4),
 511                               (unsigned int)(cp[3] & 0xf), (unsigned int)(cp[3] >> 4),
 512                               (unsigned int)(cp[2] & 0xf), (unsigned int)(cp[2] >> 4),
 513                               (unsigned int)(cp[1] & 0xf), (unsigned int)(cp[1] >> 4),
 514                               (unsigned int)(cp[0] & 0xf), (unsigned int)(cp[0] >> 4));
 515         }
 516 #endif
 517
 518         request->type = T_PTR;
 519         query_name(request);
 520 }
 521
 522 /*
 523  * query_name - generate a query based on class, type and name.
 524  */
 525 static void query_name(struct reslist *request)
 526 {
 527         char buf[MAXPACKET];
 528         int request_len = 0;
 529         int ns;
 530
 531         memset(buf, 0, sizeof(buf));
 532
 533         if ((request_len =
 534              irc_res_mkquery(request->queryname, C_IN, request->type, (unsigned char *)buf, sizeof(buf))) > 0)
 535         {
 536                 HEADER *header = (HEADER *)(void *)buf;
 537                 header->id = request->id;
 538                 ++request->sends;
 539
 540                 ns = send_res_msg(buf, request_len, request->sends);
 541                 if (ns != -1)
 542                         request->lastns = ns;
 543         }
 544 }
 545
 546 static void resend_query(struct reslist *request)
 547 {
 548         if (--request->retries <= 0)
 549         {
 550                 (*request->query->callback) (request->query->ptr, NULL);
 551                 rem_request(request);
 552                 return;
 553         }
 554
 555         switch (request->type)
 556         {
 557           case T_PTR:
 558                   do_query_number(NULL, &request->addr, request);
 559                   break;
 560           case T_A:
 561 #ifdef RB_IPV6
 562           case T_AAAA:
 563 #endif
 564                   do_query_name(NULL, request->name, request, request->type);
 565                   break;
 566           default:
 567                   break;
 568         }
 569 }
 570
 571 /*
 572  * check_question - check if the reply really belongs to the
 573  * name we queried (to guard against late replies from previous
 574  * queries with the same id).
 575  */
 576 static int check_question(struct reslist *request, HEADER * header, char *buf, char *eob)
 577 {
 578         char hostbuf[IRCD_RES_HOSTLEN + 1];     /* working buffer */
 579         unsigned char *current; /* current position in buf */
 580         int n;                  /* temp count */
 581
 582         current = (unsigned char *)buf + sizeof(HEADER);
 583         if (header->qdcount != 1)
 584                 return 0;
 585         n = irc_dn_expand((unsigned char *)buf, (unsigned char *)eob, current, hostbuf,
 586                           sizeof(hostbuf));
 587         if (n <= 0)
 588                 return 0;
 589         if (strcasecmp(hostbuf, request->queryname))
 590                 return 0;
 591         return 1;
 592 }
 593
 594 /*
 595  * proc_answer - process name server reply
 596  */
 597 static int proc_answer(struct reslist *request, HEADER * header, char *buf, char *eob)
 598 {
 599         char hostbuf[IRCD_RES_HOSTLEN + 100];   /* working buffer */
 600         unsigned char *current; /* current position in buf */
 601         int type;               /* answer type */
 602         int n;                  /* temp count */
 603         int rd_length;
 604         struct sockaddr_in *v4; /* conversion */
 605 #ifdef RB_IPV6
 606         struct sockaddr_in6 *v6;
 607 #endif
 608         current = (unsigned char *)buf + sizeof(HEADER);
 609
 610         for (; header->qdcount > 0; --header->qdcount)
 611         {
 612                 if ((n = irc_dn_skipname(current, (unsigned char *)eob)) < 0)
 613                         return 0;
 614
 615                 current += (size_t) n + QFIXEDSZ;
 616         }
 617
 618         /*
 619          * process each answer sent to us blech.
 620          */
 621         while (header->ancount > 0 && (char *)current < eob)
 622         {
 623                 header->ancount--;
 624
 625                 n = irc_dn_expand((unsigned char *)buf, (unsigned char *)eob, current, hostbuf,
 626                                   sizeof(hostbuf));
 627
 628                 if (n < 0)
 629                 {
 630                         /*
 631                          * broken message
 632                          */
 633                         return (0);
 634                 }
 635                 else if (n == 0)
 636                 {
 637                         /*
 638                          * no more answers left
 639                          */
 640                         return (0);
 641                 }
 642
 643                 hostbuf[IRCD_RES_HOSTLEN] = '\0';
 644
 645                 /* With Address arithmetic you have to be very anal
 646                  * this code was not working on alpha due to that
 647                  * (spotted by rodder/jailbird/dianora)
 648                  */
 649                 current += (size_t) n;
 650
 651                 if (!(((char *)current + ANSWER_FIXED_SIZE) < eob))
 652                         break;
 653
 654                 type = irc_ns_get16(current);
 655                 current += TYPE_SIZE;
 656
 657                 (void) irc_ns_get16(current);
 658                 current += CLASS_SIZE;
 659
 660                 request->ttl = irc_ns_get32(current);
 661                 current += TTL_SIZE;
 662
 663                 rd_length = irc_ns_get16(current);
 664                 current += RDLENGTH_SIZE;
 665
 666                 /*
 667                  * Wait to set request->type until we verify this structure
 668                  */
 669                 switch (type)
 670                 {
 671                   case T_A:
 672                           if (request->type != T_A)
 673                                   return (0);
 674
 675                           /*
 676                            * check for invalid rd_length or too many addresses
 677                            */
 678                           if (rd_length != sizeof(struct in_addr))
 679                                   return (0);
 680                           v4 = (struct sockaddr_in *)&request->addr;
 681                           SET_SS_LEN(&request->addr, sizeof(struct sockaddr_in));
 682                           v4->sin_family = AF_INET;
 683                           memcpy(&v4->sin_addr, current, sizeof(struct in_addr));
 684                           return (1);
 685                           break;
 686 #ifdef RB_IPV6
 687                   case T_AAAA:
 688                           if (request->type != T_AAAA)
 689                                   return (0);
 690                           if (rd_length != sizeof(struct in6_addr))
 691                                   return (0);
 692                           SET_SS_LEN(&request->addr, sizeof(struct sockaddr_in6));
 693                           v6 = (struct sockaddr_in6 *)&request->addr;
 694                           v6->sin6_family = AF_INET6;
 695                           memcpy(&v6->sin6_addr, current, sizeof(struct in6_addr));
 696                           return (1);
 697                           break;
 698 #endif
 699                   case T_PTR:
 700                           if (request->type != T_PTR)
 701                                   return (0);
 702                           n = irc_dn_expand((unsigned char *)buf, (unsigned char *)eob, current,
 703                                             hostbuf, sizeof(hostbuf));
 704                           if (n < 0)
 705                                   return (0);   /* broken message */
 706                           else if (n == 0)
 707                                   return (0);   /* no more answers left */
 708
 709                           rb_strlcpy(request->name, hostbuf, IRCD_RES_HOSTLEN + 1);
 710
 711                           return (1);
 712                           break;
 713                   case T_CNAME:
 714                           /* real answer will follow */
 715                           current += rd_length;
 716                           break;
 717
 718                   default:
 719                           break;
 720                 }
 721         }
 722
 723         return (1);
 724 }
 725
 726 /*
 727  * res_read_single_reply - read a dns reply from the nameserver and process it.
 728  * Return value: 1 if a packet was read, 0 otherwise
 729  */
 730 static int res_read_single_reply(rb_fde_t *F, void *data)
 731 {
 732         char buf[sizeof(HEADER) + MAXPACKET]
 733                 /* Sparc and alpha need 16bit-alignment for accessing header->id
 734                  * (which is uint16_t). Because of the header = (HEADER*) buf;
 735                  * lateron, this is neeeded. --FaUl
 736                  */
 737 #if defined(__sparc__) || defined(__alpha__)
 738                 __attribute__ ((aligned(16)))
 739 #endif
 740                 ;
 741         HEADER *header;
 742         struct reslist *request = NULL;
 743         struct DNSReply *reply = NULL;
 744         int rc;
 745         int answer_count;
 746         socklen_t len = sizeof(struct rb_sockaddr_storage);
 747         struct rb_sockaddr_storage lsin;
 748         int ns;
 749
 750         rc = recvfrom(rb_get_fd(F), buf, sizeof(buf), 0, (struct sockaddr *)&lsin, &len);
 751
 752         /* No packet */
 753         if (rc == 0 || rc == -1)
 754                 return 0;
 755
 756         /* Too small */
 757         if (rc <= (int)(sizeof(HEADER)))
 758                 return 1;
 759
 760         /*
 761          * convert DNS reply reader from Network byte order to CPU byte order.
 762          */
 763         header = (HEADER *)(void *)buf;
 764         header->ancount = ntohs(header->ancount);
 765         header->qdcount = ntohs(header->qdcount);
 766         header->nscount = ntohs(header->nscount);
 767         header->arcount = ntohs(header->arcount);
 768
 769         /*
 770          * response for an id which we have already received an answer for
 771          * just ignore this response.
 772          */
 773         if (0 == (request = find_id(header->id)))
 774                 return 1;
 775
 776         /*
 777          * check against possibly fake replies
 778          */
 779         ns = res_ourserver(&lsin);
 780         if (ns == -1)
 781                 return 1;
 782
 783         if (ns != request->lastns)
 784         {
 785                 /*
 786                  * We'll accept the late reply, but penalize it a little more to make
 787                  * sure a laggy server doesn't end up favored.
 788                  */
 789                 ns_failure_count[ns] += 3;
 790         }
 791
 792
 793         if (!check_question(request, header, buf, buf + rc))
 794                 return 1;
 795
 796         if ((header->rcode != NO_ERRORS) || (header->ancount == 0))
 797         {
 798                 /*
 799                  * RFC 2136 states that in the event of a server returning SERVFAIL
 800                  * or NOTIMP, the request should be resent to the next server.
 801                  * Additionally, if the server refuses our query, resend it as well.
 802                  * -- mr_flea
 803                  */
 804                 if (SERVFAIL == header->rcode || NOTIMP == header->rcode ||
 805                                 REFUSED == header->rcode)
 806                 {
 807                         ns_failure_count[ns]++;
 808                         resend_query(request);
 809                 }
 810                 else
 811                 {
 812                         /*
 813                          * Either a fatal error was returned or no answer. Cancel the
 814                          * request.
 815                          */
 816                         if (NXDOMAIN == header->rcode)
 817                         {
 818                                 /* If the rcode is NXDOMAIN, treat it as a good response. */
 819                                 ns_failure_count[ns] /= 4;
 820                         }
 821                         (*request->query->callback) (request->query->ptr, NULL);
 822                         rem_request(request);
 823                 }
 824                 return 1;
 825         }
 826         /*
 827          * If this fails there was an error decoding the received packet.
 828          * -- jilles
 829          */
 830         answer_count = proc_answer(request, header, buf, buf + rc);
 831
 832         if (answer_count)
 833         {
 834                 if (request->type == T_PTR)
 835                 {
 836                         if (request->name == NULL)
 837                         {
 838                                 /*
 839                                  * Got a PTR response with no name, something strange is
 840                                  * happening. Try another DNS server.
 841                                  */
 842                                 ns_failure_count[ns]++;
 843                                 resend_query(request);
 844                                 return 1;
 845                         }
 846
 847                         /*
 848                          * Lookup the 'authoritative' name that we were given for the
 849                          * ip#.
 850                          */
 851 #ifdef RB_IPV6
 852                         if (GET_SS_FAMILY(&request->addr) == AF_INET6)
 853                                 gethost_byname_type_fqdn(request->name, request->query, T_AAAA);
 854                         else
 855 #endif
 856                                 gethost_byname_type_fqdn(request->name, request->query, T_A);
 857                         rem_request(request);
 858                 }
 859                 else
 860                 {
 861                         /*
 862                          * got a name and address response, client resolved
 863                          */
 864                         reply = make_dnsreply(request);
 865                         (*request->query->callback) (request->query->ptr, reply);
 866                         rb_free(reply);
 867                         rem_request(request);
 868                 }
 869
 870                 ns_failure_count[ns] /= 4;
 871         }
 872         else
 873         {
 874                 /* Invalid or corrupt reply - try another resolver. */
 875                 ns_failure_count[ns]++;
 876                 resend_query(request);
 877         }
 878         return 1;
 879 }
 880
 881 static void
 882 res_readreply(rb_fde_t *F, void *data)
 883 {
 884         while (res_read_single_reply(F, data))
 885                 ;
 886         rb_setselect(F, RB_SELECT_READ, res_readreply, NULL);
 887 }
 888
 889 static struct DNSReply *
 890 make_dnsreply(struct reslist *request)
 891 {
 892         struct DNSReply *cp;
 893         lrb_assert(request != 0);
 894
 895         cp = (struct DNSReply *)rb_malloc(sizeof(struct DNSReply));
 896
 897         cp->h_name = request->name;
 898         memcpy(&cp->addr, &request->addr, sizeof(cp->addr));
 899         return (cp);
 900 }