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 #ifdef SO_REUSEPORT
 127     if( d_can_reuseport )
 128         if( setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &one, sizeof(one)) )
 129           d_can_reuseport = false;
 130 #endif
 131
 132     if( ::arg().mustDo("non-local-bind") )
 133         Utility::setBindAny(AF_INET, s);
 134
 135
 136     if( !d_additional_socket )
 137         g_localaddresses.push_back(locala);
 138
 139     if(::bind(s, (sockaddr*)&locala, locala.getSocklen()) < 0) {
 140       string binderror = strerror(errno);
 141       close(s);
 142       if( errno == EADDRNOTAVAIL && ! ::arg().mustDo("local-address-nonexist-fail") ) {
 143         g_log<<Logger::Error<<"IPv4 Address " << localname << " does not exist on this server - skipping UDP bind" << endl;
 144         continue;
 145       } else {
 146         g_log<<Logger::Error<<"Unable to bind UDP socket to '"+locala.toStringWithPort()+"': "<<binderror<<endl;
 147         throw PDNSException("Unable to bind to UDP socket");
 148       }
 149     }
 150     d_sockets.push_back(s);
 151     g_log<<Logger::Error<<"UDP server bound to "<<locala.toStringWithPort()<<endl;
 152     struct pollfd pfd;
 153     pfd.fd = s;
 154     pfd.events = POLLIN;
 155     pfd.revents = 0;
 156     d_rfds.push_back(pfd);
 157   }
 158 }
 159
 160 bool AddressIsUs(const ComboAddress& remote)
 161 {
 162   for(const ComboAddress& us :  g_localaddresses) {
 163     if(remote == us)
 164       return true;
 165     if(IsAnyAddress(us)) {
 166       int s = socket(remote.sin4.sin_family, SOCK_DGRAM, 0);
 167       if(s < 0)
 168         continue;
 169
 170       if(connect(s, (struct sockaddr*)&remote, remote.getSocklen()) < 0) {
 171         close(s);
 172         continue;
 173       }
 174
 175       ComboAddress actualLocal;
 176       actualLocal.sin4.sin_family = remote.sin4.sin_family;
 177       socklen_t socklen = actualLocal.getSocklen();
 178
 179       if(getsockname(s, (struct sockaddr*) &actualLocal, &socklen) < 0) {
 180         close(s);
 181         continue;
 182       }
 183       close(s);
 184       actualLocal.sin4.sin_port = us.sin4.sin_port;
 185       if(actualLocal == remote)
 186         return true;
 187     }
 188   }
 189   return false;
 190 }
 191
 192
 193 void UDPNameserver::bindIPv6()
 194 {
 195   vector<string> locals;
 196   stringtok(locals,::arg()["local-ipv6"]," ,");
 197   int one=1;
 198
 199   if(locals.empty())
 200     return;
 201
 202   int s;
 203   for(vector<string>::const_iterator i=locals.begin();i!=locals.end();++i) {
 204     string localname(*i);
 205
 206     s=socket(AF_INET6,SOCK_DGRAM,0);
 207     if(s<0) {
 208       if( errno == EAFNOSUPPORT ) {
 209         g_log<<Logger::Error<<"IPv6 Address Family is not supported - skipping UDPv6 bind" << endl;
 210         return;
 211       } else {
 212         g_log<<Logger::Error<<"Unable to acquire a UDPv6 socket: "+string(strerror(errno)) << endl;
 213         throw PDNSException("Unable to acquire a UDPv6 socket: "+string(strerror(errno)));
 214       }
 215     }
 216
 217     setCloseOnExec(s);
 218     if(!setNonBlocking(s))
 219       throw PDNSException("Unable to set UDPv6 socket to non-blocking: "+stringerror());
 220
 221     ComboAddress locala(localname, ::arg().asNum("local-port"));
 222
 223     if(IsAnyAddress(locala)) {
 224       setsockopt(s, IPPROTO_IP, GEN_IP_PKTINFO, &one, sizeof(one));     // linux supports this, so why not - might fail on other systems
 225 #ifdef IPV6_RECVPKTINFO
 226       setsockopt(s, IPPROTO_IPV6, IPV6_RECVPKTINFO, &one, sizeof(one));
 227 #endif
 228       setsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY, &one, sizeof(one));      // if this fails, we report an error in tcpreceiver too
 229     }
 230
 231     if (!setSocketTimestamps(s))
 232       g_log<<Logger::Warning<<"Unable to enable timestamp reporting for socket"<<endl;
 233
 234 #ifdef SO_REUSEPORT
 235     if( d_can_reuseport )
 236         if( setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &one, sizeof(one)) )
 237           d_can_reuseport = false;
 238 #endif
 239
 240     if( ::arg().mustDo("non-local-bind") )
 241         Utility::setBindAny(AF_INET6, s);
 242
 243     if( !d_additional_socket )
 244         g_localaddresses.push_back(locala);
 245     if(::bind(s, (sockaddr*)&locala, locala.getSocklen())<0) {
 246       close(s);
 247       if( errno == EADDRNOTAVAIL && ! ::arg().mustDo("local-ipv6-nonexist-fail") ) {
 248         g_log<<Logger::Error<<"IPv6 Address " << localname << " does not exist on this server - skipping UDP bind" << endl;
 249         continue;
 250       } else {
 251         g_log<<Logger::Error<<"Unable to bind to UDPv6 socket "<< localname <<": "<<strerror(errno)<<endl;
 252         throw PDNSException("Unable to bind to UDPv6 socket");
 253       }
 254     }
 255     d_sockets.push_back(s);
 256     struct pollfd pfd;
 257     pfd.fd = s;
 258     pfd.events = POLLIN;
 259     pfd.revents = 0;
 260     d_rfds.push_back(pfd);
 261     g_log<<Logger::Error<<"UDPv6 server bound to "<<locala.toStringWithPort()<<endl;
 262   }
 263 }
 264
 265 UDPNameserver::UDPNameserver( bool additional_socket )
 266 {
 267 #ifdef SO_REUSEPORT
 268   d_can_reuseport = ::arg().mustDo("reuseport");
 269 #endif
 270   // Are we the main socket (false) or a rebinding using SO_REUSEPORT ?
 271   d_additional_socket = additional_socket;
 272
 273   if(!::arg()["local-address"].empty())
 274     bindIPv4();
 275   if(!::arg()["local-ipv6"].empty())
 276     bindIPv6();
 277
 278   if(::arg()["local-address"].empty() && ::arg()["local-ipv6"].empty())
 279     g_log<<Logger::Critical<<"PDNS is deaf and mute! Not listening on any interfaces"<<endl;
 280 }
 281
 282 void UDPNameserver::send(DNSPacket *p)
 283 {
 284   string buffer=p->getString();
 285   g_rs.submitResponse(*p, true);
 286
 287   struct msghdr msgh;
 288   struct iovec iov;
 289   char cbuf[256];
 290
 291   fillMSGHdr(&msgh, &iov, cbuf, 0, (char*)buffer.c_str(), buffer.length(), &p->d_remote);
 292
 293   msgh.msg_control=NULL;
 294   if(p->d_anyLocal) {
 295     addCMsgSrcAddr(&msgh, cbuf, p->d_anyLocal.get_ptr(), 0);
 296   }
 297   DLOG(g_log<<Logger::Notice<<"Sending a packet to "<< p->getRemote() <<" ("<< buffer.length()<<" octets)"<<endl);
 298   if(buffer.length() > p->getMaxReplyLen()) {
 299     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;
 300   }
 301   if(sendmsg(p->getSocket(), &msgh, 0) < 0)
 302     g_log<<Logger::Error<<"Error sending reply with sendmsg (socket="<<p->getSocket()<<", dest="<<p->d_remote.toStringWithPort()<<"): "<<strerror(errno)<<endl;
 303 }
 304
 305 DNSPacket *UDPNameserver::receive(DNSPacket *prefilled, std::string& buffer)
 306 {
 307   ComboAddress remote;
 308   extern StatBag S;
 309   ssize_t len=-1;
 310   Utility::sock_t sock=-1;
 311
 312   struct msghdr msgh;
 313   struct iovec iov;
 314   char cbuf[256];
 315
 316   remote.sin6.sin6_family=AF_INET6; // make sure it is big enough
 317   fillMSGHdr(&msgh, &iov, cbuf, sizeof(cbuf), &buffer.at(0), buffer.size(), &remote);
 318
 319   int err;
 320   vector<struct pollfd> rfds= d_rfds;
 321
 322   for(auto &pfd :  rfds) {
 323     pfd.events = POLLIN;
 324     pfd.revents = 0;
 325   }
 326
 327   retry:;
 328
 329   err = poll(&rfds[0], rfds.size(), -1);
 330   if(err < 0) {
 331     if(errno==EINTR)
 332       goto retry;
 333     unixDie("Unable to poll for new UDP events");
 334   }
 335
 336   for(auto &pfd :  rfds) {
 337     if(pfd.revents & POLLIN) {
 338       sock=pfd.fd;
 339       if((len=recvmsg(sock, &msgh, 0)) < 0 ) {
 340         if(errno != EAGAIN)
 341           g_log<<Logger::Error<<"recvfrom gave error, ignoring: "<<strerror(errno)<<endl;
 342         return 0;
 343       }
 344       break;
 345     }
 346   }
 347   if(sock==-1)
 348     throw PDNSException("poll betrayed us! (should not happen)");
 349
 350   DLOG(g_log<<"Received a packet " << len <<" bytes long from "<< remote.toString()<<endl);
 351
 352   BOOST_STATIC_ASSERT(offsetof(sockaddr_in, sin_port) == offsetof(sockaddr_in6, sin6_port));
 353
 354   if(remote.sin4.sin_port == 0) // would generate error on responding. sin4 also works for ipv6
 355     return 0;
 356
 357   DNSPacket *packet;
 358   if(prefilled)  // they gave us a preallocated packet
 359     packet=prefilled;
 360   else
 361     packet=new DNSPacket(true); // don't forget to free it!
 362
 363   packet->setSocket(sock);
 364   packet->setRemote(&remote);
 365
 366   ComboAddress dest;
 367   if(HarvestDestinationAddress(&msgh, &dest)) {
 368 //    cerr<<"Setting d_anyLocal to '"<<dest.toString()<<"'"<<endl;
 369     packet->d_anyLocal = dest;
 370   }
 371
 372   struct timeval recvtv;
 373   if(HarvestTimestamp(&msgh, &recvtv)) {
 374     packet->d_dt.setTimeval(recvtv);
 375   }
 376   else
 377     packet->d_dt.set(); // timing
 378
 379   if(packet->parse(&buffer.at(0), (size_t) len)<0) {
 380     S.inc("corrupt-packets");
 381     S.ringAccount("remotes-corrupt", packet->d_remote);
 382
 383     if(!prefilled)
 384       delete packet;
 385     return 0; // unable to parse
 386   }
 387
 388   return packet;
 389 }