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::bindAddresses()
  90 {
  91   vector<string>locals;
  92   stringtok(locals,::arg()["local-ipv6"]," ,");
  93   if (!locals.empty()) {
  94     g_log<<Logger::Error<<"NOTE: Deprecated local-ipv6 setting used. Please move those addresses to the local-address setting."<<endl;
  95   }
  96   stringtok(locals,::arg()["local-address"]," ,");
  97
  98   int one = 1;
  99
 100   if(locals.empty())
 101     throw PDNSException("No local address specified");
 102
 103   int s;
 104   // for(vector<string>::const_iterator i=locals.begin();i!=locals.end();++i) {
 105   for (const auto &local : locals) {
 106     ComboAddress locala(local, ::arg().asNum("local-port"));
 107
 108     s = socket(locala.sin4.sin_family, SOCK_DGRAM, 0);
 109
 110     if(s < 0) {
 111       if(errno == EAFNOSUPPORT) {
 112         g_log<<Logger::Error<<"Binding "<<locala.toStringWithPort()<<": Address Family is not supported - skipping bind" << endl;
 113         return;
 114       }
 115       throw PDNSException("Unable to acquire a UDP socket: "+stringerror());
 116     }
 117
 118     setCloseOnExec(s);
 119     if(!setNonBlocking(s))
 120       throw PDNSException("Unable to set UDP socket " + locala.toStringWithPort() + " to non-blocking: "+stringerror());
 121
 122     if(IsAnyAddress(locala)) {
 123       setsockopt(s, IPPROTO_IP, GEN_IP_PKTINFO, &one, sizeof(one));
 124       if (locala.isIPv6()) {
 125         setsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY, &one, sizeof(one));      // if this fails, we report an error in tcpreceiver too
 126 #ifdef IPV6_RECVPKTINFO
 127         setsockopt(s, IPPROTO_IPV6, IPV6_RECVPKTINFO, &one, sizeof(one));
 128 #endif
 129       }
 130     }
 131
 132     if (!setSocketTimestamps(s))
 133       g_log<<Logger::Warning<<"Unable to enable timestamp reporting for socket "<<locala.toStringWithPort()<<endl;
 134
 135     if (locala.isIPv4()) {
 136       try {
 137         setSocketIgnorePMTU(s);
 138       }
 139       catch(const std::exception& e) {
 140         g_log<<Logger::Warning<<"Failed to set IP_MTU_DISCOVER on UDP server socket: "<<e.what()<<endl;
 141       }
 142     }
 143
 144 #ifdef SO_REUSEPORT
 145     if( d_can_reuseport )
 146         if( setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &one, sizeof(one)) )
 147           d_can_reuseport = false;
 148 #endif
 149
 150     if( ::arg().mustDo("non-local-bind") )
 151       Utility::setBindAny(locala.sin4.sin_family, s);
 152
 153     if( !d_additional_socket )
 154         g_localaddresses.push_back(locala);
 155
 156     if(::bind(s, (sockaddr*)&locala, locala.getSocklen()) < 0) {
 157       string binderror = stringerror();
 158       close(s);
 159       if( errno == EADDRNOTAVAIL && ! ::arg().mustDo("local-address-nonexist-fail") ) {
 160         g_log<<Logger::Error<<"Address " << locala << " does not exist on this server - skipping UDP bind" << endl;
 161         continue;
 162       } else {
 163         g_log<<Logger::Error<<"Unable to bind UDP socket to '"+locala.toStringWithPort()+"': "<<binderror<<endl;
 164         throw PDNSException("Unable to bind to UDP socket");
 165       }
 166     }
 167     d_sockets.push_back(s);
 168     struct pollfd pfd;
 169     pfd.fd = s;
 170     pfd.events = POLLIN;
 171     pfd.revents = 0;
 172     d_rfds.push_back(pfd);
 173     g_log<<Logger::Error<<"UDP server bound to "<<locala.toStringWithPort()<<endl;
 174   }
 175 }
 176
 177 bool AddressIsUs(const ComboAddress& remote)
 178 {
 179   for(const ComboAddress& us :  g_localaddresses) {
 180     if(remote == us)
 181       return true;
 182     if(IsAnyAddress(us)) {
 183       int s = socket(remote.sin4.sin_family, SOCK_DGRAM, 0);
 184       if(s < 0)
 185         continue;
 186
 187       if(connect(s, (struct sockaddr*)&remote, remote.getSocklen()) < 0) {
 188         close(s);
 189         continue;
 190       }
 191
 192       ComboAddress actualLocal;
 193       actualLocal.sin4.sin_family = remote.sin4.sin_family;
 194       socklen_t socklen = actualLocal.getSocklen();
 195
 196       if(getsockname(s, (struct sockaddr*) &actualLocal, &socklen) < 0) {
 197         close(s);
 198         continue;
 199       }
 200       close(s);
 201       actualLocal.sin4.sin_port = us.sin4.sin_port;
 202       if(actualLocal == remote)
 203         return true;
 204     }
 205   }
 206   return false;
 207 }
 208
 209 UDPNameserver::UDPNameserver( bool additional_socket )
 210 {
 211 #ifdef SO_REUSEPORT
 212   d_can_reuseport = ::arg().mustDo("reuseport");
 213 #endif
 214   // Are we the main socket (false) or a rebinding using SO_REUSEPORT ?
 215   d_additional_socket = additional_socket;
 216
 217   if(::arg()["local-address"].empty())
 218     g_log<<Logger::Critical<<"PDNS is deaf and mute! Not listening on any interfaces"<<endl;
 219
 220   bindAddresses();
 221 }
 222
 223 void UDPNameserver::send(DNSPacket& p)
 224 {
 225   const string& buffer=p.getString();
 226   g_rs.submitResponse(p, true);
 227
 228   struct msghdr msgh;
 229   struct iovec iov;
 230   cmsgbuf_aligned cbuf;
 231
 232   fillMSGHdr(&msgh, &iov, &cbuf, 0, (char*)buffer.c_str(), buffer.length(), &p.d_remote);
 233
 234   msgh.msg_control=NULL;
 235   if(p.d_anyLocal) {
 236     addCMsgSrcAddr(&msgh, &cbuf, p.d_anyLocal.get_ptr(), 0);
 237   }
 238   DLOG(g_log<<Logger::Notice<<"Sending a packet to "<< p.getRemote() <<" ("<< buffer.length()<<" octets)"<<endl);
 239   if(buffer.length() > p.getMaxReplyLen()) {
 240     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;
 241   }
 242   if(sendmsg(p.getSocket(), &msgh, 0) < 0)
 243     g_log<<Logger::Error<<"Error sending reply with sendmsg (socket="<<p.getSocket()<<", dest="<<p.d_remote.toStringWithPort()<<"): "<<stringerror()<<endl;
 244 }
 245
 246 bool UDPNameserver::receive(DNSPacket& packet, std::string& buffer)
 247 {
 248   ComboAddress remote;
 249   extern StatBag S;
 250   ssize_t len=-1;
 251   Utility::sock_t sock=-1;
 252
 253   struct msghdr msgh;
 254   struct iovec iov;
 255   cmsgbuf_aligned cbuf;
 256
 257   remote.sin6.sin6_family=AF_INET6; // make sure it is big enough
 258   fillMSGHdr(&msgh, &iov, &cbuf, sizeof(cbuf), &buffer.at(0), buffer.size(), &remote);
 259
 260   int err;
 261   vector<struct pollfd> rfds= d_rfds;
 262
 263   for(auto &pfd :  rfds) {
 264     pfd.events = POLLIN;
 265     pfd.revents = 0;
 266   }
 267
 268   retry:;
 269
 270   err = poll(&rfds[0], rfds.size(), -1);
 271   if(err < 0) {
 272     if(errno==EINTR)
 273       goto retry;
 274     unixDie("Unable to poll for new UDP events");
 275   }
 276
 277   for(auto &pfd :  rfds) {
 278     if(pfd.revents & POLLIN) {
 279       sock=pfd.fd;
 280       if((len=recvmsg(sock, &msgh, 0)) < 0 ) {
 281         if(errno != EAGAIN)
 282           g_log<<Logger::Error<<"recvfrom gave error, ignoring: "<<stringerror()<<endl;
 283         return 0;
 284       }
 285       break;
 286     }
 287   }
 288   if(sock==-1)
 289     throw PDNSException("poll betrayed us! (should not happen)");
 290
 291   DLOG(g_log<<"Received a packet " << len <<" bytes long from "<< remote.toString()<<endl);
 292
 293   BOOST_STATIC_ASSERT(offsetof(sockaddr_in, sin_port) == offsetof(sockaddr_in6, sin6_port));
 294
 295   if(remote.sin4.sin_port == 0) // would generate error on responding. sin4 also works for ipv6
 296     return 0;
 297
 298   packet.setSocket(sock);
 299   packet.setRemote(&remote);
 300
 301   ComboAddress dest;
 302   if(HarvestDestinationAddress(&msgh, &dest)) {
 303 //    cerr<<"Setting d_anyLocal to '"<<dest.toString()<<"'"<<endl;
 304     packet.d_anyLocal = dest;
 305   }
 306
 307   struct timeval recvtv;
 308   if(HarvestTimestamp(&msgh, &recvtv)) {
 309     packet.d_dt.setTimeval(recvtv);
 310   }
 311   else
 312     packet.d_dt.set(); // timing
 313
 314   if(packet.parse(&buffer.at(0), (size_t) len)<0) {
 315     S.inc("corrupt-packets");
 316     S.ringAccount("remotes-corrupt", packet.d_remote);
 317
 318     return false; // unable to parse
 319   }
 320
 321   return true;
 322 }