pdns/nameserver.cc

   1 /*
   2  * This file is part of PowerDNS or dnsdist.
   3  * Copyright -- PowerDNS.COM B.V. and its contributors
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of version 2 of the GNU General Public License as
   7  * published by the Free Software Foundation.
   8  *
   9  * In addition, for the avoidance of any doubt, permission is granted to
  10  * link this program with OpenSSL and to (re)distribute the binaries
  11  * produced as the result of such linking.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  21  */
  22 #ifdef HAVE_CONFIG_H
  23 #include "config.h"
  24 #endif
  25 #include "utility.hh"
  26 #include <cstdio>
  27 #include <cstring>
  28 #include <cstdlib>
  29 #include <cerrno>
  30 #include <iostream>
  31 #include <string>
  32 #include <sys/types.h>
  33 #include "responsestats.hh"
  34
  35 #include "dns.hh"
  36 #include "dnsbackend.hh"
  37 #include "dnspacket.hh"
  38 #include "nameserver.hh"
  39 #include "distributor.hh"
  40 #include "logger.hh"
  41 #include "arguments.hh"
  42 #include "statbag.hh"
  43
  44 #include "namespaces.hh"
  45
  46 extern StatBag S;
  47
  48 /** \mainpage
  49     PowerDNS is a very versatile nameserver that can answer questions from different backends. To implement your
  50     own backend, see the documentation for the DNSBackend class.
  51
  52     \section copyright Copyright and License
  53     PowerDNS is (C) 2001-2008 PowerDNS.COM BV. It is distributed according to the terms of the General Public License version 2.
  54
  55     \section overview High level overview
  56
  57     The Distributor contains a configurable number of PacketHandler instances, each in its own thread, for connection pooling.
  58     PacketHandler instances are recycled of they let escape an PDNSException.
  59
  60     The PacketHandler implements the RFC1034 algorithm and converts question packets into DNSBackend queries.
  61
  62     A DNSBackend is an entity that returns DNSResourceRecord objects in return to explicit questions for domains with a specified QType
  63
  64     PowerDNS uses the UeberBackend, which hosts DNSBackends. By default it has no DNSBackends within itself, those are loaded
  65     by setting --load=<list of backends>. This way DNSBackend implementations can be kept completely separate, but most aren't.
  66
  67     If one or more DNSBackends are loaded, the UeberBackend fields the queries to all of them until one answers.
  68
  69     \section TCP TCP Operations
  70
  71     The TCP operation runs within a single thread called tcpreceiver(), that also queries the PacketHandler.
  72
  73     \section Cache Caching
  74
  75     On its own, this setup is not suitable for high performance operations. A single DNS query can turn into many DNSBackend questions,
  76     each taking many milliseconds to complete. This is why the qthread() first checks the PacketCache to see if an answer is known to a packet
  77     asking this question. If so, the entire Distributor is shunted, and the answer is sent back *directly*, within a few microseconds.
  78
  79     \section misc Miscellaneous
  80     Configuration details are available via the ArgvMap instance arg. Statistics are created by making calls to the StatBag object called S.
  81     These statistics are made available via the UeberBackend on the same socket that is used for dynamic module commands.
  82
  83     \section Main Main
  84     The main() of PowerDNS can be found in receiver.cc - start reading there for further insights into the operation of the nameserver
  85 */
  86
  87 vector<ComboAddress> g_localaddresses; // not static, our unit tests need to poke this
  88
  89 void UDPNameserver::bindIPv4()
  90 {
  91   vector<string>locals;
  92   stringtok(locals,::arg()["local-address"]," ,");
  93   int one = 1;
  94
  95   if(locals.empty())
  96     throw PDNSException("No local address specified");
  97
  98   int s;
  99   for(vector<string>::const_iterator i=locals.begin();i!=locals.end();++i) {
 100     string localname(*i);
 101     ComboAddress locala;
 102
 103     s=socket(AF_INET,SOCK_DGRAM,0);
 104
 105     if(s<0) {
 106       g_log<<Logger::Error<<"Unable to acquire UDP socket: "+string(strerror(errno)) << endl;
 107       throw PDNSException("Unable to acquire a UDP socket: "+string(strerror(errno)));
 108     }
 109
 110     setCloseOnExec(s);
 111
 112     if(!setNonBlocking(s))
 113       throw PDNSException("Unable to set UDP socket to non-blocking: "+stringerror());
 114
 115     locala=ComboAddress(localname, ::arg().asNum("local-port"));
 116
 117     if(locala.sin4.sin_family != AF_INET)
 118       throw PDNSException("Attempting to bind IPv4 socket to IPv6 address");
 119
 120     if(IsAnyAddress(locala))
 121       setsockopt(s, IPPROTO_IP, GEN_IP_PKTINFO, &one, sizeof(one));
 122
 123     if (!setSocketTimestamps(s))
 124       g_log<<Logger::Warning<<"Unable to enable timestamp reporting for socket"<<endl;
 125
 126     if (locala.isIPv4()) {
 127       try {
 128         setSocketIgnorePMTU(s);
 129       }
 130       catch(const std::exception& e) {
 131         g_log<<Logger::Warning<<"Failed to set IP_MTU_DISCOVER on UDP server socket: "<<e.what()<<endl;
 132       }
 133     }
 134
 135 #ifdef SO_REUSEPORT
 136     if( d_can_reuseport )
 137         if( setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &one, sizeof(one)) )
 138           d_can_reuseport = false;
 139 #endif
 140
 141     if( ::arg().mustDo("non-local-bind") )
 142         Utility::setBindAny(AF_INET, s);
 143
 144
 145     if( !d_additional_socket )
 146         g_localaddresses.push_back(locala);
 147
 148     if(::bind(s, (sockaddr*)&locala, locala.getSocklen()) < 0) {
 149       string binderror = strerror(errno);
 150       close(s);
 151       if( errno == EADDRNOTAVAIL && ! ::arg().mustDo("local-address-nonexist-fail") ) {
 152         g_log<<Logger::Error<<"IPv4 Address " << localname << " does not exist on this server - skipping UDP bind" << endl;
 153         continue;
 154       } else {
 155         g_log<<Logger::Error<<"Unable to bind UDP socket to '"+locala.toStringWithPort()+"': "<<binderror<<endl;
 156         throw PDNSException("Unable to bind to UDP socket");
 157       }
 158     }
 159     d_sockets.push_back(s);
 160     g_log<<Logger::Error<<"UDP server bound to "<<locala.toStringWithPort()<<endl;
 161     struct pollfd pfd;
 162     pfd.fd = s;
 163     pfd.events = POLLIN;
 164     pfd.revents = 0;
 165     d_rfds.push_back(pfd);
 166   }
 167 }
 168
 169 bool AddressIsUs(const ComboAddress& remote)
 170 {
 171   for(const ComboAddress& us :  g_localaddresses) {
 172     if(remote == us)
 173       return true;
 174     if(IsAnyAddress(us)) {
 175       int s = socket(remote.sin4.sin_family, SOCK_DGRAM, 0);
 176       if(s < 0)
 177         continue;
 178
 179       if(connect(s, (struct sockaddr*)&remote, remote.getSocklen()) < 0) {
 180         close(s);
 181         continue;
 182       }
 183
 184       ComboAddress actualLocal;
 185       actualLocal.sin4.sin_family = remote.sin4.sin_family;
 186       socklen_t socklen = actualLocal.getSocklen();
 187
 188       if(getsockname(s, (struct sockaddr*) &actualLocal, &socklen) < 0) {
 189         close(s);
 190         continue;
 191       }
 192       close(s);
 193       actualLocal.sin4.sin_port = us.sin4.sin_port;
 194       if(actualLocal == remote)
 195         return true;
 196     }
 197   }
 198   return false;
 199 }
 200
 201
 202 void UDPNameserver::bindIPv6()
 203 {
 204   vector<string> locals;
 205   stringtok(locals,::arg()["local-ipv6"]," ,");
 206   int one=1;
 207
 208   if(locals.empty())
 209     return;
 210
 211   int s;
 212   for(vector<string>::const_iterator i=locals.begin();i!=locals.end();++i) {
 213     string localname(*i);
 214
 215     s=socket(AF_INET6,SOCK_DGRAM,0);
 216     if(s<0) {
 217       if( errno == EAFNOSUPPORT ) {
 218         g_log<<Logger::Error<<"IPv6 Address Family is not supported - skipping UDPv6 bind" << endl;
 219         return;
 220       } else {
 221         g_log<<Logger::Error<<"Unable to acquire a UDPv6 socket: "+string(strerror(errno)) << endl;
 222         throw PDNSException("Unable to acquire a UDPv6 socket: "+string(strerror(errno)));
 223       }
 224     }
 225
 226     setCloseOnExec(s);
 227     if(!setNonBlocking(s))
 228       throw PDNSException("Unable to set UDPv6 socket to non-blocking: "+stringerror());
 229
 230     ComboAddress locala(localname, ::arg().asNum("local-port"));
 231
 232     if(IsAnyAddress(locala)) {
 233       setsockopt(s, IPPROTO_IP, GEN_IP_PKTINFO, &one, sizeof(one));     // linux supports this, so why not - might fail on other systems
 234 #ifdef IPV6_RECVPKTINFO
 235       setsockopt(s, IPPROTO_IPV6, IPV6_RECVPKTINFO, &one, sizeof(one));
 236 #endif
 237       setsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY, &one, sizeof(one));      // if this fails, we report an error in tcpreceiver too
 238     }
 239
 240     if (!setSocketTimestamps(s))
 241       g_log<<Logger::Warning<<"Unable to enable timestamp reporting for socket"<<endl;
 242
 243 #ifdef SO_REUSEPORT
 244     if( d_can_reuseport )
 245         if( setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &one, sizeof(one)) )
 246           d_can_reuseport = false;
 247 #endif
 248
 249     if( ::arg().mustDo("non-local-bind") )
 250         Utility::setBindAny(AF_INET6, s);
 251
 252     if( !d_additional_socket )
 253         g_localaddresses.push_back(locala);
 254     if(::bind(s, (sockaddr*)&locala, locala.getSocklen())<0) {
 255       close(s);
 256       if( errno == EADDRNOTAVAIL && ! ::arg().mustDo("local-ipv6-nonexist-fail") ) {
 257         g_log<<Logger::Error<<"IPv6 Address " << localname << " does not exist on this server - skipping UDP bind" << endl;
 258         continue;
 259       } else {
 260         g_log<<Logger::Error<<"Unable to bind to UDPv6 socket "<< localname <<": "<<strerror(errno)<<endl;
 261         throw PDNSException("Unable to bind to UDPv6 socket");
 262       }
 263     }
 264     d_sockets.push_back(s);
 265     struct pollfd pfd;
 266     pfd.fd = s;
 267     pfd.events = POLLIN;
 268     pfd.revents = 0;
 269     d_rfds.push_back(pfd);
 270     g_log<<Logger::Error<<"UDPv6 server bound to "<<locala.toStringWithPort()<<endl;
 271   }
 272 }
 273
 274 UDPNameserver::UDPNameserver( bool additional_socket )
 275 {
 276 #ifdef SO_REUSEPORT
 277   d_can_reuseport = ::arg().mustDo("reuseport");
 278 #endif
 279   // Are we the main socket (false) or a rebinding using SO_REUSEPORT ?
 280   d_additional_socket = additional_socket;
 281
 282   if(!::arg()["local-address"].empty())
 283     bindIPv4();
 284   if(!::arg()["local-ipv6"].empty())
 285     bindIPv6();
 286
 287   if(::arg()["local-address"].empty() && ::arg()["local-ipv6"].empty())
 288     g_log<<Logger::Critical<<"PDNS is deaf and mute! Not listening on any interfaces"<<endl;
 289 }
 290
 291 void UDPNameserver::send(DNSPacket *p)
 292 {
 293   string buffer=p->getString();
 294   g_rs.submitResponse(*p, true);
 295
 296   struct msghdr msgh;
 297   struct iovec iov;
 298   char cbuf[256];
 299
 300   fillMSGHdr(&msgh, &iov, cbuf, 0, (char*)buffer.c_str(), buffer.length(), &p->d_remote);
 301
 302   msgh.msg_control=NULL;
 303   if(p->d_anyLocal) {
 304     addCMsgSrcAddr(&msgh, cbuf, p->d_anyLocal.get_ptr(), 0);
 305   }
 306   DLOG(g_log<<Logger::Notice<<"Sending a packet to "<< p->getRemote() <<" ("<< buffer.length()<<" octets)"<<endl);
 307   if(buffer.length() > p->getMaxReplyLen()) {
 308     g_log<<Logger::Error<<"Weird, trying to send a message that needs truncation, "<< buffer.length()<<" > "<<p->getMaxReplyLen()<<". Question was for "<<p->qdomain<<"|"<<p->qtype.getName()<<endl;
 309   }
 310   if(sendmsg(p->getSocket(), &msgh, 0) < 0)
 311     g_log<<Logger::Error<<"Error sending reply with sendmsg (socket="<<p->getSocket()<<", dest="<<p->d_remote.toStringWithPort()<<"): "<<strerror(errno)<<endl;
 312 }
 313
 314 DNSPacket *UDPNameserver::receive(DNSPacket *prefilled, std::string& buffer)
 315 {
 316   ComboAddress remote;
 317   extern StatBag S;
 318   ssize_t len=-1;
 319   Utility::sock_t sock=-1;
 320
 321   struct msghdr msgh;
 322   struct iovec iov;
 323   char cbuf[256];
 324
 325   remote.sin6.sin6_family=AF_INET6; // make sure it is big enough
 326   fillMSGHdr(&msgh, &iov, cbuf, sizeof(cbuf), &buffer.at(0), buffer.size(), &remote);
 327
 328   int err;
 329   vector<struct pollfd> rfds= d_rfds;
 330
 331   for(auto &pfd :  rfds) {
 332     pfd.events = POLLIN;
 333     pfd.revents = 0;
 334   }
 335
 336   retry:;
 337
 338   err = poll(&rfds[0], rfds.size(), -1);
 339   if(err < 0) {
 340     if(errno==EINTR)
 341       goto retry;
 342     unixDie("Unable to poll for new UDP events");
 343   }
 344
 345   for(auto &pfd :  rfds) {
 346     if(pfd.revents & POLLIN) {
 347       sock=pfd.fd;
 348       if((len=recvmsg(sock, &msgh, 0)) < 0 ) {
 349         if(errno != EAGAIN)
 350           g_log<<Logger::Error<<"recvfrom gave error, ignoring: "<<strerror(errno)<<endl;
 351         return 0;
 352       }
 353       break;
 354     }
 355   }
 356   if(sock==-1)
 357     throw PDNSException("poll betrayed us! (should not happen)");
 358
 359   DLOG(g_log<<"Received a packet " << len <<" bytes long from "<< remote.toString()<<endl);
 360
 361   BOOST_STATIC_ASSERT(offsetof(sockaddr_in, sin_port) == offsetof(sockaddr_in6, sin6_port));
 362
 363   if(remote.sin4.sin_port == 0) // would generate error on responding. sin4 also works for ipv6
 364     return 0;
 365
 366   DNSPacket *packet;
 367   if(prefilled)  // they gave us a preallocated packet
 368     packet=prefilled;
 369   else
 370     packet=new DNSPacket(true); // don't forget to free it!
 371
 372   packet->setSocket(sock);
 373   packet->setRemote(&remote);
 374
 375   ComboAddress dest;
 376   if(HarvestDestinationAddress(&msgh, &dest)) {
 377 //    cerr<<"Setting d_anyLocal to '"<<dest.toString()<<"'"<<endl;
 378     packet->d_anyLocal = dest;
 379   }
 380
 381   struct timeval recvtv;
 382   if(HarvestTimestamp(&msgh, &recvtv)) {
 383     packet->d_dt.setTimeval(recvtv);
 384   }
 385   else
 386     packet->d_dt.set(); // timing
 387
 388   if(packet->parse(&buffer.at(0), (size_t) len)<0) {
 389     S.inc("corrupt-packets");
 390     S.ringAccount("remotes-corrupt", packet->d_remote);
 391
 392     if(!prefilled)
 393       delete packet;
 394     return 0; // unable to parse
 395   }
 396
 397   return packet;
 398 }