src/coremods/core_dns.cpp

   1 /*
   2  * InspIRCd -- Internet Relay Chat Daemon
   3  *
   4  *   Copyright (C) 2013 Adam <Adam@anope.org>
   5  *   Copyright (C) 2003-2013 Anope Team <team@anope.org>
   6  *
   7  * This file is part of InspIRCd.  InspIRCd is free software: you can
   8  * redistribute it and/or modify it under the terms of the GNU General Public
   9  * License as published by the Free Software Foundation, version 2.
  10  *
  11  * This program is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  13  * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
  14  * details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include "inspircd.h"
  21 #include "modules/dns.h"
  22 #include <iostream>
  23 #include <fstream>
  24
  25 #ifdef _WIN32
  26 #include <Iphlpapi.h>
  27 #pragma comment(lib, "Iphlpapi.lib")
  28 #endif
  29
  30 namespace DNS
  31 {
  32         /** Maximum value of a dns request id, 16 bits wide, 0xFFFF.
  33          */
  34         const unsigned int MAX_REQUEST_ID = 0xFFFF;
  35 }
  36
  37 using namespace DNS;
  38
  39 /** A full packet sent or recieved to/from the nameserver
  40  */
  41 class Packet : public Query
  42 {
  43         static bool IsValidName(const std::string& name)
  44         {
  45                 return (name.find_first_not_of("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ.-") == std::string::npos);
  46         }
  47
  48         void PackName(unsigned char* output, unsigned short output_size, unsigned short& pos, const std::string& name)
  49         {
  50                 if (pos + name.length() + 2 > output_size)
  51                         throw Exception("Unable to pack name");
  52
  53                 ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "Packing name " + name);
  54
  55                 irc::sepstream sep(name, '.');
  56                 std::string token;
  57
  58                 while (sep.GetToken(token))
  59                 {
  60                         output[pos++] = token.length();
  61                         memcpy(&output[pos], token.data(), token.length());
  62                         pos += token.length();
  63                 }
  64
  65                 output[pos++] = 0;
  66         }
  67
  68         std::string UnpackName(const unsigned char* input, unsigned short input_size, unsigned short& pos)
  69         {
  70                 std::string name;
  71                 unsigned short pos_ptr = pos, lowest_ptr = input_size;
  72                 bool compressed = false;
  73
  74                 if (pos_ptr >= input_size)
  75                         throw Exception("Unable to unpack name - no input");
  76
  77                 while (input[pos_ptr] > 0)
  78                 {
  79                         unsigned short offset = input[pos_ptr];
  80
  81                         if (offset & POINTER)
  82                         {
  83                                 if ((offset & POINTER) != POINTER)
  84                                         throw Exception("Unable to unpack name - bogus compression header");
  85                                 if (pos_ptr + 1 >= input_size)
  86                                         throw Exception("Unable to unpack name - bogus compression header");
  87
  88                                 /* Place pos at the second byte of the first (farthest) compression pointer */
  89                                 if (compressed == false)
  90                                 {
  91                                         ++pos;
  92                                         compressed = true;
  93                                 }
  94
  95                                 pos_ptr = (offset & LABEL) << 8 | input[pos_ptr + 1];
  96
  97                                 /* Pointers can only go back */
  98                                 if (pos_ptr >= lowest_ptr)
  99                                         throw Exception("Unable to unpack name - bogus compression pointer");
 100                                 lowest_ptr = pos_ptr;
 101                         }
 102                         else
 103                         {
 104                                 if (pos_ptr + offset + 1 >= input_size)
 105                                         throw Exception("Unable to unpack name - offset too large");
 106                                 if (!name.empty())
 107                                         name += ".";
 108                                 for (unsigned i = 1; i <= offset; ++i)
 109                                         name += input[pos_ptr + i];
 110
 111                                 pos_ptr += offset + 1;
 112                                 if (compressed == false)
 113                                         /* Move up pos */
 114                                         pos = pos_ptr;
 115                         }
 116                 }
 117
 118                 /* +1 pos either to one byte after the compression pointer or one byte after the ending \0 */
 119                 ++pos;
 120
 121                 if (name.empty())
 122                         throw Exception("Unable to unpack name - no name");
 123
 124                 ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "Unpack name " + name);
 125
 126                 return name;
 127         }
 128
 129         Question UnpackQuestion(const unsigned char* input, unsigned short input_size, unsigned short& pos)
 130         {
 131                 Question q;
 132
 133                 q.name = this->UnpackName(input, input_size, pos);
 134
 135                 if (pos + 4 > input_size)
 136                         throw Exception("Unable to unpack question");
 137
 138                 q.type = static_cast<QueryType>(input[pos] << 8 | input[pos + 1]);
 139                 pos += 2;
 140
 141                 // Skip over query class code
 142                 pos += 2;
 143
 144                 return q;
 145         }
 146
 147         ResourceRecord UnpackResourceRecord(const unsigned char* input, unsigned short input_size, unsigned short& pos)
 148         {
 149                 ResourceRecord record = static_cast<ResourceRecord>(this->UnpackQuestion(input, input_size, pos));
 150
 151                 if (pos + 6 > input_size)
 152                         throw Exception("Unable to unpack resource record");
 153
 154                 record.ttl = (input[pos] << 24) | (input[pos + 1] << 16) | (input[pos + 2] << 8) | input[pos + 3];
 155                 pos += 4;
 156
 157                 uint16_t rdlength = input[pos] << 8 | input[pos + 1];
 158                 pos += 2;
 159
 160                 switch (record.type)
 161                 {
 162                         case QUERY_A:
 163                         {
 164                                 if (pos + 4 > input_size)
 165                                         throw Exception("Unable to unpack resource record");
 166
 167                                 irc::sockets::sockaddrs addrs;
 168                                 memset(&addrs, 0, sizeof(addrs));
 169
 170                                 addrs.in4.sin_family = AF_INET;
 171                                 addrs.in4.sin_addr.s_addr = input[pos] | (input[pos + 1] << 8) | (input[pos + 2] << 16)  | (input[pos + 3] << 24);
 172                                 pos += 4;
 173
 174                                 record.rdata = addrs.addr();
 175                                 break;
 176                         }
 177                         case QUERY_AAAA:
 178                         {
 179                                 if (pos + 16 > input_size)
 180                                         throw Exception("Unable to unpack resource record");
 181
 182                                 irc::sockets::sockaddrs addrs;
 183                                 memset(&addrs, 0, sizeof(addrs));
 184
 185                                 addrs.in6.sin6_family = AF_INET6;
 186                                 for (int j = 0; j < 16; ++j)
 187                                         addrs.in6.sin6_addr.s6_addr[j] = input[pos + j];
 188                                 pos += 16;
 189
 190                                 record.rdata = addrs.addr();
 191
 192                                 break;
 193                         }
 194                         case QUERY_CNAME:
 195                         case QUERY_PTR:
 196                         {
 197                                 record.rdata = this->UnpackName(input, input_size, pos);
 198                                 if (!IsValidName(record.rdata))
 199                                         throw Exception("Invalid name"); // XXX: Causes the request to time out
 200
 201                                 break;
 202                         }
 203                         case QUERY_TXT:
 204                         {
 205                                 if (pos + rdlength > input_size)
 206                                         throw Exception("Unable to unpack txt resource record");
 207
 208                                 record.rdata = std::string(reinterpret_cast<const char *>(input + pos), rdlength);
 209                                 pos += rdlength;
 210
 211                                 if (record.rdata.find_first_of("\r\n\0", 0, 3) != std::string::npos)
 212                                         throw Exception("Invalid character in txt record");
 213
 214                                 break;
 215                         }
 216                         default:
 217                                 break;
 218                 }
 219
 220                 if (!record.name.empty() && !record.rdata.empty())
 221                         ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, record.name + " -> " + record.rdata);
 222
 223                 return record;
 224         }
 225
 226  public:
 227         static const int POINTER = 0xC0;
 228         static const int LABEL = 0x3F;
 229         static const int HEADER_LENGTH = 12;
 230
 231         /* ID for this packet */
 232         RequestId id;
 233         /* Flags on the packet */
 234         unsigned short flags;
 235
 236         Packet() : id(0), flags(0)
 237         {
 238         }
 239
 240         void Fill(const unsigned char* input, const unsigned short len)
 241         {
 242                 if (len < HEADER_LENGTH)
 243                         throw Exception("Unable to fill packet");
 244
 245                 unsigned short packet_pos = 0;
 246
 247                 this->id = (input[packet_pos] << 8) | input[packet_pos + 1];
 248                 packet_pos += 2;
 249
 250                 this->flags = (input[packet_pos] << 8) | input[packet_pos + 1];
 251                 packet_pos += 2;
 252
 253                 unsigned short qdcount = (input[packet_pos] << 8) | input[packet_pos + 1];
 254                 packet_pos += 2;
 255
 256                 unsigned short ancount = (input[packet_pos] << 8) | input[packet_pos + 1];
 257                 packet_pos += 2;
 258
 259                 unsigned short nscount = (input[packet_pos] << 8) | input[packet_pos + 1];
 260                 packet_pos += 2;
 261
 262                 unsigned short arcount = (input[packet_pos] << 8) | input[packet_pos + 1];
 263                 packet_pos += 2;
 264
 265                 ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "qdcount: " + ConvToStr(qdcount) + " ancount: " + ConvToStr(ancount) + " nscount: " + ConvToStr(nscount) + " arcount: " + ConvToStr(arcount));
 266
 267                 if (qdcount != 1)
 268                         throw Exception("Question count != 1 in incoming packet");
 269
 270                 this->question = this->UnpackQuestion(input, len, packet_pos);
 271
 272                 for (unsigned i = 0; i < ancount; ++i)
 273                         this->answers.push_back(this->UnpackResourceRecord(input, len, packet_pos));
 274         }
 275
 276         unsigned short Pack(unsigned char* output, unsigned short output_size)
 277         {
 278                 if (output_size < HEADER_LENGTH)
 279                         throw Exception("Unable to pack packet");
 280
 281                 unsigned short pos = 0;
 282
 283                 output[pos++] = this->id >> 8;
 284                 output[pos++] = this->id & 0xFF;
 285                 output[pos++] = this->flags >> 8;
 286                 output[pos++] = this->flags & 0xFF;
 287                 output[pos++] = 0; // Question count, high byte
 288                 output[pos++] = 1; // Question count, low byte
 289                 output[pos++] = 0; // Answer count, high byte
 290                 output[pos++] = 0; // Answer count, low byte
 291                 output[pos++] = 0;
 292                 output[pos++] = 0;
 293                 output[pos++] = 0;
 294                 output[pos++] = 0;
 295
 296                 {
 297                         Question& q = this->question;
 298
 299                         if (q.type == QUERY_PTR)
 300                         {
 301                                 irc::sockets::sockaddrs ip;
 302                                 irc::sockets::aptosa(q.name, 0, ip);
 303
 304                                 if (q.name.find(':') != std::string::npos)
 305                                 {
 306                                         static const char* const hex = "0123456789abcdef";
 307                                         char reverse_ip[128];
 308                                         unsigned reverse_ip_count = 0;
 309                                         for (int j = 15; j >= 0; --j)
 310                                         {
 311                                                 reverse_ip[reverse_ip_count++] = hex[ip.in6.sin6_addr.s6_addr[j] & 0xF];
 312                                                 reverse_ip[reverse_ip_count++] = '.';
 313                                                 reverse_ip[reverse_ip_count++] = hex[ip.in6.sin6_addr.s6_addr[j] >> 4];
 314                                                 reverse_ip[reverse_ip_count++] = '.';
 315                                         }
 316                                         reverse_ip[reverse_ip_count++] = 0;
 317
 318                                         q.name = reverse_ip;
 319                                         q.name += "ip6.arpa";
 320                                 }
 321                                 else
 322                                 {
 323                                         unsigned long forward = ip.in4.sin_addr.s_addr;
 324                                         ip.in4.sin_addr.s_addr = forward << 24 | (forward & 0xFF00) << 8 | (forward & 0xFF0000) >> 8 | forward >> 24;
 325
 326                                         q.name = ip.addr() + ".in-addr.arpa";
 327                                 }
 328                         }
 329
 330                         this->PackName(output, output_size, pos, q.name);
 331
 332                         if (pos + 4 >= output_size)
 333                                 throw Exception("Unable to pack packet");
 334
 335                         short s = htons(q.type);
 336                         memcpy(&output[pos], &s, 2);
 337                         pos += 2;
 338
 339                         // Query class, always IN
 340                         output[pos++] = 0;
 341                         output[pos++] = 1;
 342                 }
 343
 344                 return pos;
 345         }
 346 };
 347
 348 class MyManager : public Manager, public Timer, public EventHandler
 349 {
 350         typedef TR1NS::unordered_map<Question, Query, Question::hash> cache_map;
 351         cache_map cache;
 352
 353         irc::sockets::sockaddrs myserver;
 354         bool unloading;
 355
 356         /** Maximum number of entries in cache
 357          */
 358         static const unsigned int MAX_CACHE_SIZE = 1000;
 359
 360         static bool IsExpired(const Query& record, time_t now = ServerInstance->Time())
 361         {
 362                 const ResourceRecord& req = record.answers[0];
 363                 return (req.created + static_cast<time_t>(req.ttl) < now);
 364         }
 365
 366         /** Check the DNS cache to see if request can be handled by a cached result
 367          * @return true if a cached result was found.
 368          */
 369         bool CheckCache(DNS::Request* req, const DNS::Question& question)
 370         {
 371                 ServerInstance->Logs->Log(MODNAME, LOG_SPARSE, "cache: Checking cache for " + question.name);
 372
 373                 cache_map::iterator it = this->cache.find(question);
 374                 if (it == this->cache.end())
 375                         return false;
 376
 377                 Query& record = it->second;
 378                 if (IsExpired(record))
 379                 {
 380                         this->cache.erase(it);
 381                         return false;
 382                 }
 383
 384                 ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "cache: Using cached result for " + question.name);
 385                 record.cached = true;
 386                 req->OnLookupComplete(&record);
 387                 return true;
 388         }
 389
 390         /** Add a record to the dns cache
 391          * @param r The record
 392          */
 393         void AddCache(Query& r)
 394         {
 395                 if (cache.size() >= MAX_CACHE_SIZE)
 396                         cache.clear();
 397
 398                 // Determine the lowest TTL value and use that as the TTL of the cache entry
 399                 unsigned int cachettl = UINT_MAX;
 400                 for (std::vector<ResourceRecord>::const_iterator i = r.answers.begin(); i != r.answers.end(); ++i)
 401                 {
 402                         const ResourceRecord& rr = *i;
 403                         if (rr.ttl < cachettl)
 404                                 cachettl = rr.ttl;
 405                 }
 406
 407                 cachettl = std::min(cachettl, (unsigned int)5*60);
 408                 ResourceRecord& rr = r.answers.front();
 409                 // Set TTL to what we've determined to be the lowest
 410                 rr.ttl = cachettl;
 411                 ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "cache: added cache for " + rr.name + " -> " + rr.rdata + " ttl: " + ConvToStr(rr.ttl));
 412                 this->cache[r.question] = r;
 413         }
 414
 415  public:
 416         DNS::Request* requests[MAX_REQUEST_ID+1];
 417
 418         MyManager(Module* c) : Manager(c), Timer(5*60, true)
 419                 , unloading(false)
 420         {
 421                 for (unsigned int i = 0; i <= MAX_REQUEST_ID; ++i)
 422                         requests[i] = NULL;
 423                 ServerInstance->Timers.AddTimer(this);
 424         }
 425
 426         ~MyManager()
 427         {
 428                 // Ensure Process() will fail for new requests
 429                 unloading = true;
 430
 431                 for (unsigned int i = 0; i <= MAX_REQUEST_ID; ++i)
 432                 {
 433                         DNS::Request* request = requests[i];
 434                         if (!request)
 435                                 continue;
 436
 437                         Query rr(request->question);
 438                         rr.error = ERROR_UNKNOWN;
 439                         request->OnError(&rr);
 440
 441                         delete request;
 442                 }
 443         }
 444
 445         void Process(DNS::Request* req) CXX11_OVERRIDE
 446         {
 447                 if ((unloading) || (req->creator->dying))
 448                         throw Exception("Module is being unloaded");
 449
 450                 ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "Processing request to lookup " + req->question.name + " of type " + ConvToStr(req->question.type) + " to " + this->myserver.addr());
 451
 452                 /* Create an id */
 453                 unsigned int tries = 0;
 454                 int id;
 455                 do
 456                 {
 457                         id = ServerInstance->GenRandomInt(DNS::MAX_REQUEST_ID+1);
 458
 459                         if (++tries == DNS::MAX_REQUEST_ID*5)
 460                         {
 461                                 // If we couldn't find an empty slot this many times, do a sequential scan as a last
 462                                 // resort. If an empty slot is found that way, go on, otherwise throw an exception
 463                                 id = -1;
 464                                 for (unsigned int i = 0; i <= DNS::MAX_REQUEST_ID; i++)
 465                                 {
 466                                         if (!this->requests[i])
 467                                         {
 468                                                 id = i;
 469                                                 break;
 470                                         }
 471                                 }
 472
 473                                 if (id == -1)
 474                                         throw Exception("DNS: All ids are in use");
 475
 476                                 break;
 477                         }
 478                 }
 479                 while (this->requests[id]);
 480
 481                 req->id = id;
 482                 this->requests[req->id] = req;
 483
 484                 Packet p;
 485                 p.flags = QUERYFLAGS_RD;
 486                 p.id = req->id;
 487                 p.question = req->question;
 488
 489                 unsigned char buffer[524];
 490                 unsigned short len = p.Pack(buffer, sizeof(buffer));
 491
 492                 /* Note that calling Pack() above can actually change the contents of p.question.name, if the query is a PTR,
 493                  * to contain the value that would be in the DNS cache, which is why this is here.
 494                  */
 495                 if (req->use_cache && this->CheckCache(req, p.question))
 496                 {
 497                         ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "Using cached result");
 498                         delete req;
 499                         return;
 500                 }
 501
 502                 // Update name in the original request so question checking works for PTR queries
 503                 req->question.name = p.question.name;
 504
 505                 if (SocketEngine::SendTo(this, buffer, len, 0, &this->myserver.sa, this->myserver.sa_size()) != len)
 506                         throw Exception("DNS: Unable to send query");
 507
 508                 // Add timer for timeout
 509                 ServerInstance->Timers.AddTimer(req);
 510         }
 511
 512         void RemoveRequest(DNS::Request* req) CXX11_OVERRIDE
 513         {
 514                 if (requests[req->id] == req)
 515                         requests[req->id] = NULL;
 516         }
 517
 518         std::string GetErrorStr(Error e) CXX11_OVERRIDE
 519         {
 520                 switch (e)
 521                 {
 522                         case ERROR_UNLOADED:
 523                                 return "Module is unloading";
 524                         case ERROR_TIMEDOUT:
 525                                 return "Request timed out";
 526                         case ERROR_NOT_AN_ANSWER:
 527                         case ERROR_NONSTANDARD_QUERY:
 528                         case ERROR_FORMAT_ERROR:
 529                         case ERROR_MALFORMED:
 530                                 return "Malformed answer";
 531                         case ERROR_SERVER_FAILURE:
 532                         case ERROR_NOT_IMPLEMENTED:
 533                         case ERROR_REFUSED:
 534                         case ERROR_INVALIDTYPE:
 535                                 return "Nameserver failure";
 536                         case ERROR_DOMAIN_NOT_FOUND:
 537                         case ERROR_NO_RECORDS:
 538                                 return "Domain not found";
 539                         case ERROR_NONE:
 540                         case ERROR_UNKNOWN:
 541                         default:
 542                                 return "Unknown error";
 543                 }
 544         }
 545
 546         void OnEventHandlerError(int errcode) CXX11_OVERRIDE
 547         {
 548                 ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "UDP socket got an error event");
 549         }
 550
 551         void OnEventHandlerRead() CXX11_OVERRIDE
 552         {
 553                 unsigned char buffer[524];
 554                 irc::sockets::sockaddrs from;
 555                 socklen_t x = sizeof(from);
 556
 557                 int length = SocketEngine::RecvFrom(this, buffer, sizeof(buffer), 0, &from.sa, &x);
 558
 559                 if (length < Packet::HEADER_LENGTH)
 560                         return;
 561
 562                 if (myserver != from)
 563                 {
 564                         std::string server1 = from.str();
 565                         std::string server2 = myserver.str();
 566                         ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "Got a result from the wrong server! Bad NAT or DNS forging attempt? '%s' != '%s'",
 567                                 server1.c_str(), server2.c_str());
 568                         return;
 569                 }
 570
 571                 Packet recv_packet;
 572                 bool valid = false;
 573
 574                 try
 575                 {
 576                         recv_packet.Fill(buffer, length);
 577                         valid = true;
 578                 }
 579                 catch (Exception& ex)
 580                 {
 581                         ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, ex.GetReason());
 582                 }
 583
 584                 // recv_packet.id must be filled in here
 585                 DNS::Request* request = this->requests[recv_packet.id];
 586                 if (request == NULL)
 587                 {
 588                         ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "Received an answer for something we didn't request");
 589                         return;
 590                 }
 591
 592                 if (request->question != recv_packet.question)
 593                 {
 594                         // This can happen under high latency, drop it silently, do not fail the request
 595                         ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "Received an answer that isn't for a question we asked");
 596                         return;
 597                 }
 598
 599                 if (!valid)
 600                 {
 601                         ServerInstance->stats.DnsBad++;
 602                         recv_packet.error = ERROR_MALFORMED;
 603                         request->OnError(&recv_packet);
 604                 }
 605                 else if (recv_packet.flags & QUERYFLAGS_OPCODE)
 606                 {
 607                         ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "Received a nonstandard query");
 608                         ServerInstance->stats.DnsBad++;
 609                         recv_packet.error = ERROR_NONSTANDARD_QUERY;
 610                         request->OnError(&recv_packet);
 611                 }
 612                 else if (!(recv_packet.flags & QUERYFLAGS_QR) || (recv_packet.flags & QUERYFLAGS_RCODE))
 613                 {
 614                         Error error = ERROR_UNKNOWN;
 615
 616                         switch (recv_packet.flags & QUERYFLAGS_RCODE)
 617                         {
 618                                 case 1:
 619                                         ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "format error");
 620                                         error = ERROR_FORMAT_ERROR;
 621                                         break;
 622                                 case 2:
 623                                         ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "server error");
 624                                         error = ERROR_SERVER_FAILURE;
 625                                         break;
 626                                 case 3:
 627                                         ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "domain not found");
 628                                         error = ERROR_DOMAIN_NOT_FOUND;
 629                                         break;
 630                                 case 4:
 631                                         ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "not implemented");
 632                                         error = ERROR_NOT_IMPLEMENTED;
 633                                         break;
 634                                 case 5:
 635                                         ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "refused");
 636                                         error = ERROR_REFUSED;
 637                                         break;
 638                                 default:
 639                                         break;
 640                         }
 641
 642                         ServerInstance->stats.DnsBad++;
 643                         recv_packet.error = error;
 644                         request->OnError(&recv_packet);
 645                 }
 646                 else if (recv_packet.answers.empty())
 647                 {
 648                         ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "No resource records returned");
 649                         ServerInstance->stats.DnsBad++;
 650                         recv_packet.error = ERROR_NO_RECORDS;
 651                         request->OnError(&recv_packet);
 652                 }
 653                 else
 654                 {
 655                         ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "Lookup complete for " + request->question.name);
 656                         ServerInstance->stats.DnsGood++;
 657                         request->OnLookupComplete(&recv_packet);
 658                         this->AddCache(recv_packet);
 659                 }
 660
 661                 ServerInstance->stats.Dns++;
 662
 663                 /* Request's destructor removes it from the request map */
 664                 delete request;
 665         }
 666
 667         bool Tick(time_t now) CXX11_OVERRIDE
 668         {
 669                 ServerInstance->Logs->Log(MODNAME, LOG_DEBUG, "cache: purging DNS cache");
 670
 671                 for (cache_map::iterator it = this->cache.begin(); it != this->cache.end(); )
 672                 {
 673                         const Query& query = it->second;
 674                         if (IsExpired(query, now))
 675                                 this->cache.erase(it++);
 676                         else
 677                                 ++it;
 678                 }
 679                 return true;
 680         }
 681
 682         void Rehash(const std::string& dnsserver, std::string sourceaddr, unsigned int sourceport)
 683         {
 684                 if (this->GetFd() > -1)
 685                 {
 686                         SocketEngine::Shutdown(this, 2);
 687                         SocketEngine::Close(this);
 688
 689                         /* Remove expired entries from the cache */
 690                         this->Tick(ServerInstance->Time());
 691                 }
 692
 693                 irc::sockets::aptosa(dnsserver, DNS::PORT, myserver);
 694
 695                 /* Initialize mastersocket */
 696                 int s = socket(myserver.sa.sa_family, SOCK_DGRAM, 0);
 697                 this->SetFd(s);
 698
 699                 /* Have we got a socket? */
 700                 if (this->GetFd() != -1)
 701                 {
 702                         SocketEngine::SetReuse(s);
 703                         SocketEngine::NonBlocking(s);
 704
 705                         irc::sockets::sockaddrs bindto;
 706                         if (sourceaddr.empty())
 707                         {
 708                                 // set a sourceaddr for irc::sockets::aptosa() based on the servers af type
 709                                 if (myserver.sa.sa_family == AF_INET)
 710                                         sourceaddr = "0.0.0.0";
 711                                 else if (myserver.sa.sa_family == AF_INET6)
 712                                         sourceaddr = "::";
 713                         }
 714                         irc::sockets::aptosa(sourceaddr, sourceport, bindto);
 715
 716                         if (SocketEngine::Bind(this->GetFd(), bindto) < 0)
 717                         {
 718                                 /* Failed to bind */
 719                                 ServerInstance->Logs->Log(MODNAME, LOG_SPARSE, "Error binding dns socket - hostnames will NOT resolve");
 720                                 SocketEngine::Close(this->GetFd());
 721                                 this->SetFd(-1);
 722                         }
 723                         else if (!SocketEngine::AddFd(this, FD_WANT_POLL_READ | FD_WANT_NO_WRITE))
 724                         {
 725                                 ServerInstance->Logs->Log(MODNAME, LOG_SPARSE, "Internal error starting DNS - hostnames will NOT resolve.");
 726                                 SocketEngine::Close(this->GetFd());
 727                                 this->SetFd(-1);
 728                         }
 729
 730                         if (bindto.sa.sa_family != myserver.sa.sa_family)
 731                                 ServerInstance->Logs->Log(MODNAME, LOG_SPARSE, "Nameserver address family differs from source address family - hostnames might not resolve");
 732                 }
 733                 else
 734                 {
 735                         ServerInstance->Logs->Log(MODNAME, LOG_SPARSE, "Error creating DNS socket - hostnames will NOT resolve");
 736                 }
 737         }
 738 };
 739
 740 class ModuleDNS : public Module
 741 {
 742         MyManager manager;
 743         std::string DNSServer;
 744         std::string SourceIP;
 745         unsigned int SourcePort;
 746
 747         void FindDNSServer()
 748         {
 749 #ifdef _WIN32
 750                 // attempt to look up their nameserver from the system
 751                 ServerInstance->Logs->Log(MODNAME, LOG_DEFAULT, "WARNING: <dns:server> not defined, attempting to find a working server in the system settings...");
 752
 753                 PFIXED_INFO pFixedInfo;
 754                 DWORD dwBufferSize = sizeof(FIXED_INFO);
 755                 pFixedInfo = (PFIXED_INFO) HeapAlloc(GetProcessHeap(), 0, sizeof(FIXED_INFO));
 756
 757                 if (pFixedInfo)
 758                 {
 759                         if (GetNetworkParams(pFixedInfo, &dwBufferSize) == ERROR_BUFFER_OVERFLOW)
 760                         {
 761                                 HeapFree(GetProcessHeap(), 0, pFixedInfo);
 762                                 pFixedInfo = (PFIXED_INFO) HeapAlloc(GetProcessHeap(), 0, dwBufferSize);
 763                         }
 764
 765                         if (pFixedInfo)
 766                         {
 767                                 if (GetNetworkParams(pFixedInfo, &dwBufferSize) == NO_ERROR)
 768                                         DNSServer = pFixedInfo->DnsServerList.IpAddress.String;
 769
 770                                 HeapFree(GetProcessHeap(), 0, pFixedInfo);
 771                         }
 772
 773                         if (!DNSServer.empty())
 774                         {
 775                                 ServerInstance->Logs->Log(MODNAME, LOG_DEFAULT, "<dns:server> set to '%s' as first active resolver in the system settings.", DNSServer.c_str());
 776                                 return;
 777                         }
 778                 }
 779
 780                 ServerInstance->Logs->Log(MODNAME, LOG_DEFAULT, "No viable nameserver found! Defaulting to nameserver '127.0.0.1'!");
 781 #else
 782                 // attempt to look up their nameserver from /etc/resolv.conf
 783                 ServerInstance->Logs->Log(MODNAME, LOG_DEFAULT, "WARNING: <dns:server> not defined, attempting to find working server in /etc/resolv.conf...");
 784
 785                 std::ifstream resolv("/etc/resolv.conf");
 786
 787                 while (resolv >> DNSServer)
 788                 {
 789                         if (DNSServer == "nameserver")
 790                         {
 791                                 resolv >> DNSServer;
 792                                 if (DNSServer.find_first_not_of("0123456789.") == std::string::npos || DNSServer.find_first_not_of("0123456789ABCDEFabcdef:") == std::string::npos)
 793                                 {
 794                                         ServerInstance->Logs->Log(MODNAME, LOG_DEFAULT, "<dns:server> set to '%s' as first resolver in /etc/resolv.conf.",DNSServer.c_str());
 795                                         return;
 796                                 }
 797                         }
 798                 }
 799
 800                 ServerInstance->Logs->Log(MODNAME, LOG_DEFAULT, "/etc/resolv.conf contains no viable nameserver entries! Defaulting to nameserver '127.0.0.1'!");
 801 #endif
 802                 DNSServer = "127.0.0.1";
 803         }
 804
 805  public:
 806         ModuleDNS() : manager(this)
 807                 , SourcePort(0)
 808         {
 809         }
 810
 811         void ReadConfig(ConfigStatus& status) CXX11_OVERRIDE
 812         {
 813                 std::string oldserver = DNSServer;
 814                 const std::string oldip = SourceIP;
 815                 const unsigned int oldport = SourcePort;
 816
 817                 ConfigTag* tag = ServerInstance->Config->ConfValue("dns");
 818                 DNSServer = tag->getString("server");
 819                 SourceIP = tag->getString("sourceip");
 820                 SourcePort = tag->getInt("sourceport", 0, 0, 65535);
 821
 822                 if (DNSServer.empty())
 823                         FindDNSServer();
 824
 825                 if (oldserver != DNSServer || oldip != SourceIP || oldport != SourcePort)
 826                         this->manager.Rehash(DNSServer, SourceIP, SourcePort);
 827         }
 828
 829         void OnUnloadModule(Module* mod) CXX11_OVERRIDE
 830         {
 831                 for (unsigned int i = 0; i <= MAX_REQUEST_ID; ++i)
 832                 {
 833                         DNS::Request* req = this->manager.requests[i];
 834                         if (!req)
 835                                 continue;
 836
 837                         if (req->creator == mod)
 838                         {
 839                                 Query rr(req->question);
 840                                 rr.error = ERROR_UNLOADED;
 841                                 req->OnError(&rr);
 842
 843                                 delete req;
 844                         }
 845                 }
 846         }
 847
 848         Version GetVersion() CXX11_OVERRIDE
 849         {
 850                 return Version("DNS support", VF_CORE|VF_VENDOR);
 851         }
 852 };
 853
 854 MODULE_INIT(ModuleDNS)
 855