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 /* Build an rDNS style query - if suffix is NULL, use the appropriate .arpa zone */
 469 void build_rdns(char *buf, size_t size, const struct rb_sockaddr_storage *addr, const char *suffix)
 470 {
 471         const unsigned char *cp;
 472
 473         if (GET_SS_FAMILY(addr) == AF_INET)
 474         {
 475                 const struct sockaddr_in *v4 = (const struct sockaddr_in *)addr;
 476                 cp = (const unsigned char *)&v4->sin_addr.s_addr;
 477
 478                 (void) snprintf(buf, size, "%u.%u.%u.%u.%s",
 479                         (unsigned int)(cp[3]),
 480                         (unsigned int)(cp[2]),
 481                         (unsigned int)(cp[1]),
 482                         (unsigned int)(cp[0]),
 483                         suffix == NULL ? "in-addr.arpa" : suffix);
 484         }
 485 #ifdef RB_IPV6
 486         else if (GET_SS_FAMILY(addr) == AF_INET6)
 487         {
 488                 const struct sockaddr_in6 *v6 = (const struct sockaddr_in6 *)addr;
 489                 cp = (const unsigned char *)&v6->sin6_addr.s6_addr;
 490
 491                 (void) snprintf(buf, size,
 492                         "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%s",
 493                         (unsigned int)(cp[15] & 0xf), (unsigned int)(cp[15] >> 4),
 494                         (unsigned int)(cp[14] & 0xf), (unsigned int)(cp[14] >> 4),
 495                         (unsigned int)(cp[13] & 0xf), (unsigned int)(cp[13] >> 4),
 496                         (unsigned int)(cp[12] & 0xf), (unsigned int)(cp[12] >> 4),
 497                         (unsigned int)(cp[11] & 0xf), (unsigned int)(cp[11] >> 4),
 498                         (unsigned int)(cp[10] & 0xf), (unsigned int)(cp[10] >> 4),
 499                         (unsigned int)(cp[9] & 0xf), (unsigned int)(cp[9] >> 4),
 500                         (unsigned int)(cp[8] & 0xf), (unsigned int)(cp[8] >> 4),
 501                         (unsigned int)(cp[7] & 0xf), (unsigned int)(cp[7] >> 4),
 502                         (unsigned int)(cp[6] & 0xf), (unsigned int)(cp[6] >> 4),
 503                         (unsigned int)(cp[5] & 0xf), (unsigned int)(cp[5] >> 4),
 504                         (unsigned int)(cp[4] & 0xf), (unsigned int)(cp[4] >> 4),
 505                         (unsigned int)(cp[3] & 0xf), (unsigned int)(cp[3] >> 4),
 506                         (unsigned int)(cp[2] & 0xf), (unsigned int)(cp[2] >> 4),
 507                         (unsigned int)(cp[1] & 0xf), (unsigned int)(cp[1] >> 4),
 508                         (unsigned int)(cp[0] & 0xf), (unsigned int)(cp[0] >> 4),
 509                         suffix == NULL ? "ip6.arpa" : suffix);
 510         }
 511 #endif
 512 }
 513
 514 /*
 515  * do_query_number - Use this to do reverse IP# lookups.
 516  */
 517 static void do_query_number(struct DNSQuery *query, const struct rb_sockaddr_storage *addr,
 518                             struct reslist *request)
 519 {
 520         if (request == NULL)
 521         {
 522                 request = make_request(query);
 523                 memcpy(&request->addr, addr, sizeof(struct rb_sockaddr_storage));
 524                 request->name = (char *)rb_malloc(IRCD_RES_HOSTLEN + 1);
 525         }
 526
 527         build_rdns(request->queryname, IRCD_RES_HOSTLEN + 1, addr, NULL);
 528
 529         request->type = T_PTR;
 530         query_name(request);
 531 }
 532
 533 /*
 534  * query_name - generate a query based on class, type and name.
 535  */
 536 static void query_name(struct reslist *request)
 537 {
 538         char buf[MAXPACKET];
 539         int request_len = 0;
 540         int ns;
 541
 542         memset(buf, 0, sizeof(buf));
 543
 544         if ((request_len =
 545              irc_res_mkquery(request->queryname, C_IN, request->type, (unsigned char *)buf, sizeof(buf))) > 0)
 546         {
 547                 HEADER *header = (HEADER *)(void *)buf;
 548                 header->id = request->id;
 549                 ++request->sends;
 550
 551                 ns = send_res_msg(buf, request_len, request->sends);
 552                 if (ns != -1)
 553                         request->lastns = ns;
 554         }
 555 }
 556
 557 static void resend_query(struct reslist *request)
 558 {
 559         if (--request->retries <= 0)
 560         {
 561                 (*request->query->callback) (request->query->ptr, NULL);
 562                 rem_request(request);
 563                 return;
 564         }
 565
 566         switch (request->type)
 567         {
 568           case T_PTR:
 569                   do_query_number(NULL, &request->addr, request);
 570                   break;
 571           case T_A:
 572 #ifdef RB_IPV6
 573           case T_AAAA:
 574 #endif
 575                   do_query_name(NULL, request->name, request, request->type);
 576                   break;
 577           default:
 578                   break;
 579         }
 580 }
 581
 582 /*
 583  * check_question - check if the reply really belongs to the
 584  * name we queried (to guard against late replies from previous
 585  * queries with the same id).
 586  */
 587 static int check_question(struct reslist *request, HEADER * header, char *buf, char *eob)
 588 {
 589         char hostbuf[IRCD_RES_HOSTLEN + 1];     /* working buffer */
 590         unsigned char *current; /* current position in buf */
 591         int n;                  /* temp count */
 592
 593         current = (unsigned char *)buf + sizeof(HEADER);
 594         if (header->qdcount != 1)
 595                 return 0;
 596         n = irc_dn_expand((unsigned char *)buf, (unsigned char *)eob, current, hostbuf,
 597                           sizeof(hostbuf));
 598         if (n <= 0)
 599                 return 0;
 600         if (strcasecmp(hostbuf, request->queryname))
 601                 return 0;
 602         return 1;
 603 }
 604
 605 /*
 606  * proc_answer - process name server reply
 607  */
 608 static int proc_answer(struct reslist *request, HEADER * header, char *buf, char *eob)
 609 {
 610         char hostbuf[IRCD_RES_HOSTLEN + 100];   /* working buffer */
 611         unsigned char *current; /* current position in buf */
 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                 (void) 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                           break;
 731                 }
 732         }
 733
 734         return (1);
 735 }
 736
 737 /*
 738  * res_read_single_reply - read a dns reply from the nameserver and process it.
 739  * Return value: 1 if a packet was read, 0 otherwise
 740  */
 741 static int res_read_single_reply(rb_fde_t *F, void *data)
 742 {
 743         char buf[sizeof(HEADER) + MAXPACKET]
 744                 /* Sparc and alpha need 16bit-alignment for accessing header->id
 745                  * (which is uint16_t). Because of the header = (HEADER*) buf;
 746                  * lateron, this is neeeded. --FaUl
 747                  */
 748 #if defined(__sparc__) || defined(__alpha__)
 749                 __attribute__ ((aligned(16)))
 750 #endif
 751                 ;
 752         HEADER *header;
 753         struct reslist *request = NULL;
 754         struct DNSReply *reply = NULL;
 755         int rc;
 756         int answer_count;
 757         socklen_t len = sizeof(struct rb_sockaddr_storage);
 758         struct rb_sockaddr_storage lsin;
 759         int ns;
 760
 761         rc = recvfrom(rb_get_fd(F), buf, sizeof(buf), 0, (struct sockaddr *)&lsin, &len);
 762
 763         /* No packet */
 764         if (rc == 0 || rc == -1)
 765                 return 0;
 766
 767         /* Too small */
 768         if (rc <= (int)(sizeof(HEADER)))
 769                 return 1;
 770
 771         /*
 772          * convert DNS reply reader from Network byte order to CPU byte order.
 773          */
 774         header = (HEADER *)(void *)buf;
 775         header->ancount = ntohs(header->ancount);
 776         header->qdcount = ntohs(header->qdcount);
 777         header->nscount = ntohs(header->nscount);
 778         header->arcount = ntohs(header->arcount);
 779
 780         /*
 781          * response for an id which we have already received an answer for
 782          * just ignore this response.
 783          */
 784         if (0 == (request = find_id(header->id)))
 785                 return 1;
 786
 787         /*
 788          * check against possibly fake replies
 789          */
 790         ns = res_ourserver(&lsin);
 791         if (ns == -1)
 792                 return 1;
 793
 794         if (ns != request->lastns)
 795         {
 796                 /*
 797                  * We'll accept the late reply, but penalize it a little more to make
 798                  * sure a laggy server doesn't end up favored.
 799                  */
 800                 ns_failure_count[ns] += 3;
 801         }
 802
 803
 804         if (!check_question(request, header, buf, buf + rc))
 805                 return 1;
 806
 807         if ((header->rcode != NO_ERRORS) || (header->ancount == 0))
 808         {
 809                 /*
 810                  * RFC 2136 states that in the event of a server returning SERVFAIL
 811                  * or NOTIMP, the request should be resent to the next server.
 812                  * Additionally, if the server refuses our query, resend it as well.
 813                  * -- mr_flea
 814                  */
 815                 if (SERVFAIL == header->rcode || NOTIMP == header->rcode ||
 816                                 REFUSED == header->rcode)
 817                 {
 818                         ns_failure_count[ns]++;
 819                         resend_query(request);
 820                 }
 821                 else
 822                 {
 823                         /*
 824                          * Either a fatal error was returned or no answer. Cancel the
 825                          * request.
 826                          */
 827                         if (NXDOMAIN == header->rcode)
 828                         {
 829                                 /* If the rcode is NXDOMAIN, treat it as a good response. */
 830                                 ns_failure_count[ns] /= 4;
 831                         }
 832                         (*request->query->callback) (request->query->ptr, NULL);
 833                         rem_request(request);
 834                 }
 835                 return 1;
 836         }
 837         /*
 838          * If this fails there was an error decoding the received packet.
 839          * -- jilles
 840          */
 841         answer_count = proc_answer(request, header, buf, buf + rc);
 842
 843         if (answer_count)
 844         {
 845                 if (request->type == T_PTR)
 846                 {
 847                         if (request->name == NULL)
 848                         {
 849                                 /*
 850                                  * Got a PTR response with no name, something strange is
 851                                  * happening. Try another DNS server.
 852                                  */
 853                                 ns_failure_count[ns]++;
 854                                 resend_query(request);
 855                                 return 1;
 856                         }
 857
 858                         /*
 859                          * Lookup the 'authoritative' name that we were given for the
 860                          * ip#.
 861                          */
 862 #ifdef RB_IPV6
 863                         if (GET_SS_FAMILY(&request->addr) == AF_INET6)
 864                                 gethost_byname_type_fqdn(request->name, request->query, T_AAAA);
 865                         else
 866 #endif
 867                                 gethost_byname_type_fqdn(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                         rb_free(reply);
 878                         rem_request(request);
 879                 }
 880
 881                 ns_failure_count[ns] /= 4;
 882         }
 883         else
 884         {
 885                 /* Invalid or corrupt reply - try another resolver. */
 886                 ns_failure_count[ns]++;
 887                 resend_query(request);
 888         }
 889         return 1;
 890 }
 891
 892 static void
 893 res_readreply(rb_fde_t *F, void *data)
 894 {
 895         while (res_read_single_reply(F, data))
 896                 ;
 897         rb_setselect(F, RB_SELECT_READ, res_readreply, NULL);
 898 }
 899
 900 static struct DNSReply *
 901 make_dnsreply(struct reslist *request)
 902 {
 903         struct DNSReply *cp;
 904         lrb_assert(request != 0);
 905
 906         cp = (struct DNSReply *)rb_malloc(sizeof(struct DNSReply));
 907
 908         cp->h_name = request->name;
 909         memcpy(&cp->addr, &request->addr, sizeof(cp->addr));
 910         return (cp);
 911 }