pdns/nameserver.cc

   1 /*
   2     Copyright (C) 2002 - 2012  PowerDNS.COM BV
   3
   4     This program is free software; you can redistribute it and/or modify
   5     it under the terms of the GNU General Public License version 2 as
   6     published by the Free Software Foundation.
   7
   8     Additionally, the license of this program contains a special
   9     exception which allows to distribute the program in binary form when
  10     it is linked against OpenSSL.
  11
  12     This program is distributed in the hope that it will be useful,
  13     but WITHOUT ANY WARRANTY; without even the implied warranty of
  14     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15     GNU General Public License for more details.
  16
  17     You should have received a copy of the GNU General Public License
  18     along with this program; if not, write to the Free Software
  19     Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  20 */
  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 as its DNSBackend. The UeberBackend by default has no DNSBackends within itself, those are loaded
  65     using the pdns_control tool. This way DNSBackend implementations can be kept completely separate (but they often aren't).s
  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       L<<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     memset(&locala,0,sizeof(locala));
 116     locala.sin4.sin_family=AF_INET;
 117
 118     if(localname=="0.0.0.0")
 119       setsockopt(s, IPPROTO_IP, GEN_IP_PKTINFO, &one, sizeof(one));
 120
 121     if (!setSocketTimestamps(s))
 122       L<<Logger::Warning<<"Unable to enable timestamp reporting for socket"<<endl;
 123
 124 #ifdef SO_REUSEPORT
 125     if( d_can_reuseport )
 126         if( setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &one, sizeof(one)) )
 127           d_can_reuseport = false;
 128 #endif
 129
 130     if( ::arg().mustDo("non-local-bind") )
 131         Utility::setBindAny(AF_INET, s);
 132
 133     locala=ComboAddress(localname, ::arg().asNum("local-port"));
 134     if(locala.sin4.sin_family != AF_INET)
 135       throw PDNSException("Attempting to bind IPv4 socket to IPv6 address");
 136
 137     if( !d_additional_socket )
 138         g_localaddresses.push_back(locala);
 139
 140     if(::bind(s, (sockaddr*)&locala, locala.getSocklen()) < 0) {
 141       string binderror = strerror(errno);
 142       close(s);
 143       if( errno == EADDRNOTAVAIL && ! ::arg().mustDo("local-address-nonexist-fail") ) {
 144         L<<Logger::Error<<"IPv4 Address " << localname << " does not exist on this server - skipping UDP bind" << endl;
 145         continue;
 146       } else {
 147         L<<Logger::Error<<"Unable to bind UDP socket to '"+locala.toStringWithPort()+"': "<<binderror<<endl;
 148         throw PDNSException("Unable to bind to UDP socket");
 149       }
 150     }
 151     d_sockets.push_back(s);
 152     L<<Logger::Error<<"UDP server bound to "<<locala.toStringWithPort()<<endl;
 153     struct pollfd pfd;
 154     pfd.fd = s;
 155     pfd.events = POLLIN;
 156     pfd.revents = 0;
 157     d_rfds.push_back(pfd);
 158   }
 159 }
 160
 161 bool AddressIsUs(const ComboAddress& remote)
 162 {
 163   for(const ComboAddress& us :  g_localaddresses) {
 164     if(remote == us)
 165       return true;
 166     if(IsAnyAddress(us)) {
 167       int s = socket(remote.sin4.sin_family, SOCK_DGRAM, 0);
 168       if(s < 0)
 169         continue;
 170
 171       if(connect(s, (struct sockaddr*)&remote, remote.getSocklen()) < 0) {
 172         close(s);
 173         continue;
 174       }
 175
 176       ComboAddress actualLocal;
 177       actualLocal.sin4.sin_family = remote.sin4.sin_family;
 178       socklen_t socklen = actualLocal.getSocklen();
 179
 180       if(getsockname(s, (struct sockaddr*) &actualLocal, &socklen) < 0) {
 181         close(s);
 182         continue;
 183       }
 184       close(s);
 185       actualLocal.sin4.sin_port = us.sin4.sin_port;
 186       if(actualLocal == remote)
 187         return true;
 188     }
 189   }
 190   return false;
 191 }
 192
 193
 194 void UDPNameserver::bindIPv6()
 195 {
 196   vector<string> locals;
 197   stringtok(locals,::arg()["local-ipv6"]," ,");
 198   int one=1;
 199
 200   if(locals.empty())
 201     return;
 202
 203   int s;
 204   for(vector<string>::const_iterator i=locals.begin();i!=locals.end();++i) {
 205     string localname(*i);
 206
 207     s=socket(AF_INET6,SOCK_DGRAM,0);
 208     if(s<0) {
 209       if( errno == EAFNOSUPPORT ) {
 210         L<<Logger::Error<<"IPv6 Address Family is not supported - skipping UDPv6 bind" << endl;
 211         return;
 212       } else {
 213         L<<Logger::Error<<"Unable to acquire a UDPv6 socket: "+string(strerror(errno)) << endl;
 214         throw PDNSException("Unable to acquire a UDPv6 socket: "+string(strerror(errno)));
 215       }
 216     }
 217
 218     setCloseOnExec(s);
 219     if(!setNonBlocking(s))
 220       throw PDNSException("Unable to set UDPv6 socket to non-blocking: "+stringerror());
 221
 222     ComboAddress locala(localname, ::arg().asNum("local-port"));
 223
 224     if(IsAnyAddress(locala)) {
 225       setsockopt(s, IPPROTO_IP, GEN_IP_PKTINFO, &one, sizeof(one));     // linux supports this, so why not - might fail on other systems
 226 #ifdef IPV6_RECVPKTINFO
 227       setsockopt(s, IPPROTO_IPV6, IPV6_RECVPKTINFO, &one, sizeof(one));
 228 #endif
 229       setsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY, &one, sizeof(one));      // if this fails, we report an error in tcpreceiver too
 230     }
 231
 232     if (!setSocketTimestamps(s))
 233       L<<Logger::Warning<<"Unable to enable timestamp reporting for socket"<<endl;
 234
 235 #ifdef SO_REUSEPORT
 236     if( d_can_reuseport )
 237         if( setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &one, sizeof(one)) )
 238           d_can_reuseport = false;
 239 #endif
 240
 241     if( ::arg().mustDo("non-local-bind") )
 242         Utility::setBindAny(AF_INET6, s);
 243
 244     if( !d_additional_socket )
 245         g_localaddresses.push_back(locala);
 246     if(::bind(s, (sockaddr*)&locala, sizeof(locala))<0) {
 247       close(s);
 248       if( errno == EADDRNOTAVAIL && ! ::arg().mustDo("local-ipv6-nonexist-fail") ) {
 249         L<<Logger::Error<<"IPv6 Address " << localname << " does not exist on this server - skipping UDP bind" << endl;
 250         continue;
 251       } else {
 252         L<<Logger::Error<<"Unable to bind to UDPv6 socket "<< localname <<": "<<strerror(errno)<<endl;
 253         throw PDNSException("Unable to bind to UDPv6 socket");
 254       }
 255     }
 256     d_sockets.push_back(s);
 257     struct pollfd pfd;
 258     pfd.fd = s;
 259     pfd.events = POLLIN;
 260     pfd.revents = 0;
 261     d_rfds.push_back(pfd);
 262     L<<Logger::Error<<"UDPv6 server bound to "<<locala.toStringWithPort()<<endl;
 263   }
 264 }
 265
 266 UDPNameserver::UDPNameserver( bool additional_socket )
 267 {
 268 #ifdef SO_REUSEPORT
 269   d_can_reuseport = ::arg().mustDo("reuseport");
 270 #endif
 271   // Are we the main socket (false) or a rebinding using SO_REUSEPORT ?
 272   d_additional_socket = additional_socket;
 273
 274   if(!::arg()["local-address"].empty())
 275     bindIPv4();
 276   if(!::arg()["local-ipv6"].empty())
 277     bindIPv6();
 278
 279   if(::arg()["local-address"].empty() && ::arg()["local-ipv6"].empty())
 280     L<<Logger::Critical<<"PDNS is deaf and mute! Not listening on any interfaces"<<endl;
 281 }
 282
 283 void UDPNameserver::send(DNSPacket *p)
 284 {
 285   string buffer=p->getString();
 286   g_rs.submitResponse(*p, true);
 287
 288   struct msghdr msgh;
 289   struct iovec iov;
 290   char cbuf[256];
 291
 292   fillMSGHdr(&msgh, &iov, cbuf, 0, (char*)buffer.c_str(), buffer.length(), &p->d_remote);
 293
 294   msgh.msg_control=NULL;
 295   if(p->d_anyLocal) {
 296     addCMsgSrcAddr(&msgh, cbuf, p->d_anyLocal.get_ptr(), 0);
 297   }
 298   DLOG(L<<Logger::Notice<<"Sending a packet to "<< p->getRemote() <<" ("<< buffer.length()<<" octets)"<<endl);
 299   if(buffer.length() > p->getMaxReplyLen()) {
 300     L<<Logger::Error<<"Weird, trying to send a message that needs truncation, "<< buffer.length()<<" > "<<p->getMaxReplyLen()<<endl;
 301   }
 302   if(sendmsg(p->getSocket(), &msgh, 0) < 0)
 303     L<<Logger::Error<<"Error sending reply with sendmsg (socket="<<p->getSocket()<<", dest="<<p->d_remote.toStringWithPort()<<"): "<<strerror(errno)<<endl;
 304 }
 305
 306 DNSPacket *UDPNameserver::receive(DNSPacket *prefilled)
 307 {
 308   ComboAddress remote;
 309   extern StatBag S;
 310   ssize_t len=-1;
 311   char mesg[DNSPacket::s_udpTruncationThreshold];
 312   Utility::sock_t sock=-1;
 313
 314   struct msghdr msgh;
 315   struct iovec iov;
 316   char cbuf[256];
 317
 318   remote.sin6.sin6_family=AF_INET6; // make sure it is big enough
 319   fillMSGHdr(&msgh, &iov, cbuf, sizeof(cbuf), mesg, sizeof(mesg), &remote);
 320
 321   int err;
 322   vector<struct pollfd> rfds= d_rfds;
 323
 324   for(struct pollfd &pfd :  rfds) {
 325     pfd.events = POLLIN;
 326     pfd.revents = 0;
 327   }
 328
 329   retry:;
 330
 331   err = poll(&rfds[0], rfds.size(), -1);
 332   if(err < 0) {
 333     if(errno==EINTR)
 334       goto retry;
 335     unixDie("Unable to poll for new UDP events");
 336   }
 337
 338   for(struct pollfd &pfd :  rfds) {
 339     if(pfd.revents & POLLIN) {
 340       sock=pfd.fd;
 341       if((len=recvmsg(sock, &msgh, 0)) < 0 ) {
 342         if(errno != EAGAIN)
 343           L<<Logger::Error<<"recvfrom gave error, ignoring: "<<strerror(errno)<<endl;
 344         return 0;
 345       }
 346       break;
 347     }
 348   }
 349   if(sock==-1)
 350     throw PDNSException("poll betrayed us! (should not happen)");
 351
 352   DLOG(L<<"Received a packet " << len <<" bytes long from "<< remote.toString()<<endl);
 353
 354   BOOST_STATIC_ASSERT(offsetof(sockaddr_in, sin_port) == offsetof(sockaddr_in6, sin6_port));
 355
 356   if(remote.sin4.sin_port == 0) // would generate error on responding. sin4 also works for ipv6
 357     return 0;
 358
 359   DNSPacket *packet;
 360   if(prefilled)  // they gave us a preallocated packet
 361     packet=prefilled;
 362   else
 363     packet=new DNSPacket; // don't forget to free it!
 364
 365   packet->setSocket(sock);
 366   packet->setRemote(&remote);
 367
 368   ComboAddress dest;
 369   if(HarvestDestinationAddress(&msgh, &dest)) {
 370 //    cerr<<"Setting d_anyLocal to '"<<dest.toString()<<"'"<<endl;
 371     packet->d_anyLocal = dest;
 372   }
 373
 374   struct timeval recvtv;
 375   if(HarvestTimestamp(&msgh, &recvtv)) {
 376     packet->d_dt.setTimeval(recvtv);
 377   }
 378   else
 379     packet->d_dt.set(); // timing
 380
 381   if(packet->parse(mesg, (size_t) len)<0) {
 382     S.inc("corrupt-packets");
 383     S.ringAccount("remotes-corrupt", packet->d_remote);
 384
 385     if(!prefilled)
 386       delete packet;
 387     return 0; // unable to parse
 388   }
 389
 390   return packet;
 391 }