pdns/tcpreceiver.cc

   1 /*
   2     PowerDNS Versatile Database Driven Nameserver
   3     Copyright (C) 2002  PowerDNS.COM BV
   4
   5     This program is free software; you can redistribute it and/or modify
   6     it under the terms of the GNU General Public License as published by
   7     the Free Software Foundation; either version 2 of the License, or
   8     (at your option) any later version.
   9
  10     This program is distributed in the hope that it will be useful,
  11     but WITHOUT ANY WARRANTY; without even the implied warranty of
  12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13     GNU General Public License for more details.
  14
  15     You should have received a copy of the GNU General Public License
  16     along with this program; if not, write to the Free Software
  17     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18 */
  19 #include "utility.hh"
  20 #include <cstdio>
  21 #include <cstring>
  22 #include <cstdlib>
  23 #include <sys/types.h>
  24 #include <iostream>
  25 #include <string>
  26 #include "tcpreceiver.hh"
  27
  28 #include <errno.h>
  29 #include <signal.h>
  30
  31 #include "ueberbackend.hh"
  32 #include "dnspacket.hh"
  33 #include "nameserver.hh"
  34 #include "distributor.hh"
  35 #include "lock.hh"
  36 #include "logger.hh"
  37 #include "arguments.hh"
  38 #include "packetcache.hh"
  39 #include "packethandler.hh"
  40 #include "statbag.hh"
  41 #include "resolver.hh"
  42 #include "communicator.hh"
  43
  44 extern PacketCache PC;
  45 extern StatBag S;
  46
  47 /**
  48 \file tcpreceiver.cc
  49 \brief This file implements the tcpreceiver that receives and answers questions over TCP/IP
  50 */
  51
  52 pthread_mutex_t TCPNameserver::s_plock = PTHREAD_MUTEX_INITIALIZER;
  53 Semaphore *TCPNameserver::d_connectionroom_sem;
  54 PacketHandler *TCPNameserver::s_P;
  55 int TCPNameserver::s_timeout;
  56
  57
  58 int TCPNameserver::sendDelPacket(DNSPacket *p, int outsock)
  59 {
  60   const char *buf=p->getData();
  61   int res=sendData(buf, p->len, outsock);
  62   delete p;
  63   return res;
  64 }
  65
  66
  67 void TCPNameserver::go()
  68 {
  69   L<<Logger::Error<<"Creating backend connection for TCP"<<endl;
  70   s_P=0;
  71   try {
  72     s_P=new PacketHandler;
  73   }
  74   catch(AhuException &ae) {
  75     L<<Logger::Error<<Logger::NTLog<<"TCP server is unable to launch backends - will try again when questions come in"<<endl;
  76   }
  77   pthread_create(&d_tid, 0, launcher, static_cast<void *>(this));
  78 }
  79
  80 void *TCPNameserver::launcher(void *data)
  81 {
  82   static_cast<TCPNameserver *>(data)->thread();
  83   return 0;
  84 }
  85
  86
  87 int TCPNameserver::readLength(int fd, struct sockaddr_in *remote)
  88 {
  89   int bytesLeft=2;
  90   unsigned char buf[2];
  91
  92   Utility::socklen_t remotelen=sizeof(*remote);
  93   getpeername(fd, (struct sockaddr *)remote, &remotelen);
  94
  95   while(bytesLeft) {
  96     int ret=waitForData(fd, s_timeout);
  97     if(ret<0)
  98       throw AhuException("Waiting on data from remote TCP client "+string(inet_ntoa(remote->sin_addr))+": "+stringerror());
  99
 100     ret=recv(fd, reinterpret_cast< char * >( buf ) +2-bytesLeft, bytesLeft,0);
 101     if(ret<0)
 102       throw AhuException("Trying to read data from remote TCP client "+string(inet_ntoa(remote->sin_addr))+": "+stringerror());
 103     if(!ret) {
 104       DLOG(L<<"Remote TCP client "+string(inet_ntoa(remote->sin_addr))+" closed connection");
 105       return -1;
 106     }
 107     bytesLeft-=ret;
 108   }
 109   return buf[0]*256+buf[1];
 110 }
 111
 112 void TCPNameserver::getQuestion(int fd, char *mesg, int pktlen, const struct sockaddr_in &remote)
 113 {
 114   int ret=0, bytesread=0;
 115   while(bytesread<pktlen) {
 116     if((ret=waitForData(fd,s_timeout))<0 || (ret=recv(fd,mesg+bytesread,pktlen-bytesread,0))<=0)
 117       goto err;
 118
 119     bytesread+=ret;
 120   }
 121   return;
 122
 123  err:;
 124   if(ret<0)
 125     throw AhuException("Error reading DNS data from TCP client "+string(inet_ntoa(remote.sin_addr))+": "+stringerror());
 126   else
 127     throw AhuException("Remote TCP client "+string(inet_ntoa(remote.sin_addr))+" closed connection");
 128 }
 129
 130 void *TCPNameserver::doConnection(void *data)
 131 {
 132   int fd=(int)data; // gotta love C
 133   pthread_detach(pthread_self());
 134
 135   try {
 136     if(!s_P) {
 137       L<<Logger::Error<<"TCP server is without backend connections, launching"<<endl;
 138       s_P=new PacketHandler;
 139     }
 140     char mesg[512];
 141
 142     DLOG(L<<"TCP Connection accepted on fd "<<fd<<endl);
 143
 144     for(;;) {
 145       struct sockaddr_in remote;
 146
 147       int pktlen=readLength(fd, &remote);
 148       if(pktlen<0) // EOF
 149         break;
 150
 151       if(pktlen>511) {
 152         L<<Logger::Error<<"Received an overly large question from "<<inet_ntoa(remote.sin_addr)<<", dropping"<<endl;
 153         break;
 154       }
 155
 156       getQuestion(fd,mesg,pktlen,remote);
 157       S.inc("tcp-queries");
 158       DNSPacket *packet=new DNSPacket;
 159
 160       if(packet->parse(mesg, pktlen)<0)
 161         break;
 162
 163       packet->setRemote((struct sockaddr *)&remote,sizeof(remote));
 164
 165       if(packet->qtype.getCode()==QType::AXFR) {
 166         if(doAXFR(packet->qdomain, packet, fd))
 167           S.inc("tcp-answers");
 168         continue;
 169       }
 170
 171       if(packet->d.rd && arg().mustDo("recursor")) {
 172         // now what
 173         // this is a pretty rare event all in all, so we can afford to be slow
 174         S.inc("recursing-questions");
 175         Resolver res;
 176         unsigned int len;
 177         DLOG(L<<"About to hand query to recursor"<<endl);
 178         ServiceTuple st;
 179         st.port=53;
 180         parseService(arg()["recursor"],st);
 181
 182         char *buffer=res.sendReceive(st.host,st.port,packet->getRaw(),packet->len,&len);
 183         DLOG(L<<"got an answer from recursor: "<<len<<" bytes, "<<(int)buffer<<endl);
 184         if(buffer) {
 185           sendData(buffer,len,fd);
 186           DLOG(L<<"sent out to customer: "<<len<<" bytes"<<endl);
 187           delete buffer;
 188           S.inc("recursing-answers");
 189           S.inc("tcp-answers");
 190         }
 191         continue;
 192       }
 193
 194       DNSPacket* cached=new DNSPacket;
 195       if(!packet->d.rd && (PC.get(packet, cached))) { // short circuit - does the PacketCache recognize this question?
 196         cached->setRemote((struct sockaddr *)(packet->remote), sizeof(struct sockaddr_in));
 197         cached->spoofID(packet->d.id);
 198         if(sendDelPacket(cached, fd)<0)
 199           goto out;
 200
 201         S.inc("tcp-answers");
 202         continue;
 203       }
 204       else
 205         delete cached;
 206
 207       DNSPacket *reply;
 208       {
 209         Lock l(&s_plock);
 210         reply=s_P->question(packet); // we really need to ask the backend :-)
 211       }
 212
 213       delete packet;
 214
 215       if(!reply)  // unable to write an answer?
 216         break;
 217
 218       S.inc("tcp-answers");
 219       sendDelPacket(reply, fd);
 220     }
 221
 222   out:;
 223   }
 224   catch(DBException &e) {
 225     L<<Logger::Error<<"TCP Connection Thread unable to answer a question because of a backend error"<<endl;
 226   }
 227   catch(AhuException &ae) {
 228     L<<Logger::Error<<"TCP nameserver: "<<ae.reason<<endl;
 229   }
 230   catch(exception &e) {
 231     L<<Logger::Error<<"TCP Connection Thread died because of STL error: "<<e.what()<<endl;
 232   }
 233   catch( ... )
 234   {
 235     L << Logger::Error << "TCP Connection Thread caught unknown exception." << endl;
 236   }
 237   Utility::closesocket(fd);
 238   d_connectionroom_sem->post();
 239
 240   return 0;
 241 }
 242
 243 static bool canDoAXFR(DNSPacket *q)
 244 {
 245   if(!arg().mustDo("disable-axfr")) // default is 'everybody can do axfr'
 246     return true;
 247
 248   vector<string>parts;
 249   stringtok(parts,arg()["allow-axfr-ips"],", "); // is this IP on the guestlist?
 250   for(vector<string>::const_iterator i=parts.begin();i!=parts.end();++i) {
 251     if(matchNetmask(q->getRemote().c_str(),i->c_str())==1)
 252       return true;
 253   }
 254
 255   extern CommunicatorClass Communicator;
 256
 257   if(Communicator.justNotified(q->qdomain, q->getRemote())) { // we just notified this ip
 258     L<<Logger::Warning<<"Approved AXFR of '"<<q->qdomain<<"' from recently notified slave "<<q->getRemote()<<endl;
 259     return true;
 260   }
 261
 262   return false;
 263 }
 264
 265 /** do the actual zone transfer. Return 0 in case of error, 1 in case of success */
 266 int TCPNameserver::doAXFR(const string &target, DNSPacket *q, int outsock)
 267 {
 268   DNSPacket *outpacket=0;
 269   if(!canDoAXFR(q)) {
 270     L<<Logger::Error<<"AXFR of domain '"<<target<<"' denied to "<<q->getRemote()<<endl;
 271
 272     outpacket=q->replyPacket();
 273     outpacket->setRcode(RCode::Refused);
 274     // FIXME: should actually figure out if we are auth over a zone, and send out 9 if we aren't
 275     sendDelPacket(outpacket,outsock);
 276     return 0;
 277   }
 278   L<<Logger::Error<<"AXFR of domain '"<<target<<"' initiated by "<<q->getRemote()<<endl;
 279   outpacket=q->replyPacket();
 280
 281   DNSResourceRecord soa;
 282   DNSResourceRecord rr;
 283
 284   SOAData sd;
 285   {
 286     Lock l(&s_plock);
 287
 288     // find domain_id via SOA and list complete domain. No SOA, no AXFR
 289
 290     DLOG(L<<"Looking for SOA"<<endl);
 291
 292     if(!s_P->getBackend()->getSOA(target,sd)) {
 293       outpacket->setRcode(9); // 'NOTAUTH'
 294       sendDelPacket(outpacket,outsock);
 295       return 0;
 296     }
 297     soa.qname=target;
 298     soa.qtype=QType::SOA;
 299     soa.content=DNSPacket::serializeSOAData(sd);
 300     soa.ttl=sd.default_ttl;
 301     soa.domain_id=sd.domain_id;
 302     soa.d_place=DNSResourceRecord::ANSWER;
 303   }
 304
 305   DLOG(L<<"Issuing list command - opening dedicated database connection"<<endl);
 306   PacketHandler P;
 307   DNSBackend *B=P.getBackend();
 308
 309   // now list zone
 310   if(!(B->list(sd.domain_id))) {
 311     L<<Logger::Error<<"Backend signals error condition"<<endl;
 312     outpacket->setRcode(2); // 'SERVFAIL'
 313     sendDelPacket(outpacket,outsock);
 314     return 0;
 315   }
 316
 317   /* write first part of answer */
 318
 319   DLOG(L<<"Sending out SOA"<<endl);
 320   outpacket->addRecord(soa); // AXFR format begins and ends with a SOA record, so we add one
 321   sendDelPacket(outpacket, outsock);
 322
 323   /* now write all other records */
 324
 325   int count=0;
 326   int chunk=100; // FIXME: this should probably be autosizing
 327   if(arg().mustDo("strict-rfc-axfrs"))
 328     chunk=1;
 329
 330   outpacket=q->replyPacket();
 331   outpacket->setCompress(false);
 332
 333   while(B->get(rr)) {
 334     if(rr.qtype.getCode()==6)
 335       continue; // skip SOA - would indicate end of AXFR
 336
 337     outpacket->addRecord(rr);
 338
 339     if(!((++count)%chunk)) {
 340       count=0;
 341
 342       if(sendDelPacket(outpacket, outsock)<0)  // FIXME: this leaks memory!
 343         return 0;
 344
 345       outpacket=q->replyPacket();
 346       outpacket->setCompress(false);
 347       // FIXME: Subsequent messages SHOULD NOT have a question section, though the final message MAY.
 348     }
 349   }
 350   if(count) {
 351     sendDelPacket(outpacket, outsock);
 352   }
 353
 354   DLOG(L<<"Done writing out records"<<endl);
 355   /* and terminate with yet again the SOA record */
 356   outpacket=q->replyPacket();
 357   outpacket->addRecord(soa);
 358   sendDelPacket(outpacket, outsock);
 359   DLOG(L<<"last packet - close"<<endl);
 360   L<<Logger::Error<<"AXFR of domain '"<<target<<"' to "<<q->getRemote()<<" finished"<<endl;
 361
 362   return 1;
 363 }
 364
 365 TCPNameserver::~TCPNameserver()
 366 {
 367   delete d_connectionroom_sem;
 368 }
 369
 370 TCPNameserver::TCPNameserver()
 371 {
 372 //  sem_init(&d_connectionroom_sem,0,arg().asNum("max-tcp-connections"));
 373   d_connectionroom_sem = new Semaphore( arg().asNum( "max-tcp-connections" ));
 374
 375   s_timeout=10;
 376   vector<string>locals;
 377   stringtok(locals,arg()["local-address"]," ,");
 378
 379   vector<string>locals6;
 380   stringtok(locals6,arg()["local-ipv6"]," ,");
 381
 382
 383   if(locals.empty() && locals6.empty())
 384     throw AhuException("No local address specified");
 385
 386   d_highfd=0;
 387
 388 #ifndef WIN32
 389   signal(SIGPIPE,SIG_IGN);
 390 #endif // WIN32
 391   FD_ZERO(&d_rfds);
 392
 393   for(vector<string>::const_iterator laddr=locals.begin();laddr!=locals.end();++laddr) {
 394     struct sockaddr_in local;
 395     int s=socket(AF_INET,SOCK_STREAM,0);
 396
 397     if(s<0)
 398       throw AhuException("Unable to acquire TCP socket: "+stringerror());
 399
 400     memset(&local,0,sizeof(local));
 401     local.sin_family=AF_INET;
 402
 403     struct hostent *h;
 404
 405     if ( *laddr == "0.0.0.0" )
 406     {
 407       local.sin_addr.s_addr = INADDR_ANY;
 408     }
 409     else
 410     {
 411       h=gethostbyname(laddr->c_str());
 412
 413       if(!h)
 414         throw AhuException("Unable to resolve local address '"+*laddr+"'");
 415
 416       local.sin_addr.s_addr=*(int*)h->h_addr;
 417     }
 418
 419     int tmp=1;
 420     if(setsockopt(s,SOL_SOCKET,SO_REUSEADDR,(char*)&tmp,sizeof tmp)<0) {
 421       L<<Logger::Error<<"Setsockopt failed"<<endl;
 422       exit(1);
 423     }
 424
 425     local.sin_port=htons(arg().asNum("local-port"));
 426
 427     if(bind(s, (sockaddr*)&local,sizeof(local))<0) {
 428       L<<Logger::Error<<"binding to TCP socket: "<<strerror(errno)<<endl;
 429       throw AhuException("Unable to bind to TCP socket");
 430     }
 431
 432     listen(s,128);
 433     L<<Logger::Error<<"TCP server bound to "<<*laddr<<":"<<arg()["local-port"]<<endl;
 434     d_sockets.push_back(s);
 435     FD_SET(s, &d_rfds);
 436     d_highfd=max(s,d_highfd);
 437   }
 438
 439   // TODO: Implement ipv6
 440 #if !WIN32 && HAVE_IPV6
 441   for(vector<string>::const_iterator laddr=locals6.begin();laddr!=locals6.end();++laddr) {
 442     int s=socket(AF_INET6,SOCK_STREAM,0);
 443
 444     if(s<0)
 445       throw AhuException("Unable to acquire TCPv6 socket: "+stringerror());
 446
 447     sockaddr_in6 locala;
 448     locala.sin6_port=ntohs(arg().asNum("local-port"));
 449     locala.sin6_family=AF_INET6;
 450     locala.sin6_flowinfo=0;
 451
 452
 453     if(!inet_pton(AF_INET6, laddr->c_str(), (void *)&locala.sin6_addr)) {
 454       addrinfo *addrinfos;
 455       addrinfo hints;
 456       memset(&hints,0,sizeof(hints));
 457       hints.ai_socktype=SOCK_STREAM;
 458       hints.ai_family=AF_INET6;
 459
 460       if(getaddrinfo(laddr->c_str(),arg()["local-port"].c_str(),&hints,&addrinfos))
 461         throw AhuException("Unable to resolve local IPv6 address '"+*laddr+"'");
 462
 463       memcpy(&locala,addrinfos->ai_addr,addrinfos->ai_addrlen);
 464     }
 465
 466     int tmp=1;
 467     if(setsockopt(s,SOL_SOCKET,SO_REUSEADDR,(char*)&tmp,sizeof tmp)<0) {
 468       L<<Logger::Error<<"Setsockopt failed"<<endl;
 469       exit(1);
 470     }
 471
 472
 473     if(bind(s, (const sockaddr*)&locala, sizeof(locala))<0) {
 474       L<<Logger::Error<<"binding to TCP socket: "<<strerror(errno)<<endl;
 475       throw AhuException("Unable to bind to TCPv6 socket");
 476     }
 477
 478     listen(s,128);
 479     L<<Logger::Error<<"TCPv6 server bound to "<<*laddr<<":"<<arg()["local-port"]<<endl;
 480     d_sockets.push_back(s);
 481     FD_SET(s, &d_rfds);
 482     d_highfd=max(s,d_highfd);
 483   }
 484 #endif // WIN32
 485 }
 486
 487
 488 //! Start of TCP operations thread
 489 void TCPNameserver::thread()
 490 {
 491   struct timeval tv;
 492   tv.tv_sec=1;
 493   tv.tv_usec=0;
 494   try {
 495     for(;;) {
 496       int fd;
 497       struct sockaddr_in remote;
 498       Utility::socklen_t addrlen=sizeof(remote);
 499
 500       fd_set rfds=d_rfds;
 501
 502       select(d_highfd+1, &rfds, 0, 0,  0); // blocks
 503       int sock=-1;
 504       for(vector<int>::const_iterator i=d_sockets.begin();i!=d_sockets.end();++i) {
 505         if(FD_ISSET(*i, &rfds)) {
 506           sock=*i;
 507           addrlen=sizeof(remote);
 508
 509           if((fd=accept(sock, (sockaddr*)&remote, &addrlen))<0) {
 510             L<<Logger::Error<<"TCP question accept error: "<<strerror(errno)<<endl;
 511
 512             if(errno==EMFILE) {
 513               L<<Logger::Error<<Logger::NTLog<<"TCP handler out of filedescriptors, exiting, won't recover from this"<<endl;
 514               exit(1);
 515             }
 516           }
 517           else {
 518             pthread_t tid;
 519             d_connectionroom_sem->wait(); // blocks if no connections are available
 520
 521             int room;
 522             d_connectionroom_sem->getValue( &room);
 523             if(room<1)
 524               L<<Logger::Warning<<Logger::NTLog<<"Limit of simultaneous TCP connections reached - raise max-tcp-connections"<<endl;
 525
 526             if(pthread_create(&tid, 0, &doConnection, (void *)fd)) {
 527               L<<Logger::Error<<"Error creating thread: "<<stringerror()<<endl;
 528               d_connectionroom_sem->post();
 529             }
 530           }
 531         }
 532       }
 533     }
 534   }
 535   catch(AhuException &AE) {
 536     L<<Logger::Error<<"TCP Namerserver thread dying because of fatal error: "<<AE.reason<<endl;
 537   }
 538   catch(...) {
 539     L<<Logger::Error<<"TCPNameserver dying because of an unexpected fatal error"<<endl;
 540   }
 541   exit(1); // take rest of server with us
 542 }
 543
 544