pdns/nameserver.cc

   1 /*
   2     Copyright (C) 2002  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 as published by
   6     the Free Software Foundation; either version 2 of the License, or
   7     (at your option) any later version.
   8
   9     This program is distributed in the hope that it will be useful,
  10     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12     GNU General Public License for more details.
  13
  14     You should have received a copy of the GNU General Public License
  15     along with this program; if not, write to the Free Software
  16     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  17 */
  18 // $Id: nameserver.cc,v 1.3 2002/12/10 13:36:26 ahu Exp $
  19 #include "utility.hh"
  20 #include <cstdio>
  21 #include <cstring>
  22 #include <cstdlib>
  23 #include <cerrno>
  24 #include <iostream>
  25 #include <string>
  26 #include <sys/types.h>
  27
  28 #include "dns.hh"
  29 #include "dnsbackend.hh"
  30 #include "dnspacket.hh"
  31 #include "nameserver.hh"
  32 #include "distributor.hh"
  33 #include "logger.hh"
  34 #include "arguments.hh"
  35 #include "statbag.hh"
  36
  37 extern StatBag S;
  38
  39 /** \mainpage
  40     ahudns is a very versatile nameserver that can answer questions from different backends. To implement your
  41     own backend, see the documentation for the DNSBackend class.
  42
  43     \section copyright Copyright and License
  44     AhuDNS is (C) 2002 PowerDNS BV.
  45
  46     AhuDNS is NOT open source (yet), so treat this code as a trade secret. If it has been supplied to you for evaluation,
  47     this does not mean that you can deploy the code!
  48
  49     \section overview High level overview
  50
  51     AhuDNS is highly threaded, which means that several tasks each have their own process thread. Two of the pivotal
  52     threads are the qthread() and the athread().
  53
  54     - The qthread() receives questions over the network (via the Nameserver class, which returns DNSPacket objects), and gives them to the Distributor.
  55     - The athread() waits on the Distributor to return answers, ready to send back over the network, again via UDPNameserver.
  56
  57     The Distributor contains a configurable number of PacketHandler instances, each in its own thread, for connection pooling
  58
  59     The PacketHandler implements the RFC1034 algorithm and converts question packets into DNSBackend queries.
  60
  61     A DNSBackend is an entity that returns DNSResourceRecord objects in return to explicit questions for domains with a specified QType
  62
  63     AhuDNS uses the UeberBackend as its DNSBackend. The UeberBackend by default has no DNSBackends within itself, those are loaded
  64     using the dynloader tool. This way DNSBackend implementations can be kept completely separate.
  65
  66     If one or more DNSBackends are loaded, the UeberBackend fields the queries to all of them until one answers.
  67
  68     \section TCP TCP Operations
  69
  70     The TCP operation runs within a single thread called tcpreceiver(), that also queries the PacketHandler.
  71
  72     \section Cache Caching
  73
  74     On its own, this setup is not suitable for high performance operations. A single DNS query can turn into many DNSBackend questions,
  75     each taking many miliseconds to complete. This is why the qthread() first checks the PacketCache to see if an answer is known to a packet
  76     asking this question. If so, the entire Distributor is shunted, and the answer is sent back *directly*, within a few microseconds.
  77
  78     In turn, the athread() offers each outgoing packet to the PacketCache for possible inclusion.
  79
  80     \section misc Miscellaneous
  81     Configuration details are available via the ArgvMap instance arg. Statistics are created by making calls to the StatBag object called S.
  82     These statistics are made available via the UeberBackend on the same socket that is used for dynamic module commands.
  83
  84     \section Main Main
  85     The main() of AhuDNS can be found in receiver.cc - start reading there for further insights into the operation of the nameserver
  86
  87
  88 */
  89
  90 void UDPNameserver::bindIPv4()
  91 {
  92   vector<string>locals;
  93   stringtok(locals,arg()["local-address"]," ,");
  94
  95   if(locals.empty())
  96     throw AhuException("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     struct sockaddr_in locala;
 102
 103     s=socket(AF_INET,SOCK_DGRAM,0);
 104     if(s<0)
 105       throw AhuException("Unable to acquire a UDP socket: "+string(strerror(errno)));
 106
 107     memset(&locala,0,sizeof(locala));
 108     locala.sin_family=AF_INET;
 109
 110     if(localname=="0.0.0.0") {
 111       L<<Logger::Warning<<"It is advised to bind to explicit addresses with the --local-address option"<<endl;
 112
 113       locala.sin_addr.s_addr = INADDR_ANY;
 114     }
 115     else
 116     {
 117       struct hostent *h=0;
 118       h=gethostbyname(localname.c_str());
 119       if(!h)
 120         throw AhuException("Unable to resolve local address");
 121
 122       locala.sin_addr.s_addr=*(int*)h->h_addr;
 123     }
 124
 125     locala.sin_port=htons(arg().asNum("local-port"));
 126
 127     if(bind(s, (sockaddr*)&locala,sizeof(locala))<0) {
 128       L<<Logger::Error<<"binding to UDP socket: "<<strerror(errno)<<endl;
 129       throw AhuException("Unable to bind to UDP socket");
 130     }
 131     d_highfd=max(s,d_highfd);
 132     d_sockets.push_back(s);
 133     L<<Logger::Error<<"UDP server bound to "<<localname<<":"<<arg()["local-port"]<<endl;
 134     FD_SET(s, &d_rfds);
 135   }
 136 }
 137
 138 void UDPNameserver::bindIPv6()
 139 {
 140 #if !WIN32 && HAVE_IPV6
 141   vector<string>locals;
 142   stringtok(locals,arg()["local-ipv6"]," ,");
 143
 144   if(locals.empty())
 145     return;
 146
 147
 148   int s;
 149   for(vector<string>::const_iterator i=locals.begin();i!=locals.end();++i) {
 150     string localname(*i);
 151
 152     s=socket(AF_INET6,SOCK_DGRAM,0);
 153     if(s<0)
 154       throw AhuException("Unable to acquire a UDPv6 socket: "+string(strerror(errno)));
 155
 156     if(localname=="::0") {
 157       L<<Logger::Warning<<"It is advised to bind to explicit addresses with the --local-ipv6 option"<<endl;
 158     }
 159
 160     sockaddr_in6 locala;
 161     locala.sin6_port=ntohs(arg().asNum("local-port"));
 162     if(!inet_pton(AF_INET6, localname.c_str(), (void *)&locala.sin6_addr)) {
 163       addrinfo *addrinfos;
 164       addrinfo hints;
 165       memset(&hints,0,sizeof(hints));
 166       hints.ai_socktype=SOCK_DGRAM;
 167       hints.ai_family=AF_INET6;
 168
 169       if(getaddrinfo(localname.c_str(),arg()["local-port"].c_str(),&hints,&addrinfos))
 170         throw AhuException("Unable to resolve local IPv6 address '"+localname+"'");
 171       memcpy(&locala,addrinfos->ai_addr,addrinfos->ai_addrlen);
 172     }
 173
 174     if(bind(s, (sockaddr*)&locala, sizeof(locala))<0) {
 175       L<<Logger::Error<<"binding to UDP ipv6 socket: "<<strerror(errno)<<endl;
 176       throw AhuException("Unable to bind to UDP ipv6 socket");
 177     }
 178     d_highfd=max(s,d_highfd);
 179     d_sockets.push_back(s);
 180     L<<Logger::Error<<"UDPv6 server bound to "<<localname<<":"<<arg()["local-port"]<<endl;
 181     FD_SET(s, &d_rfds);
 182   }
 183 #endif // WIN32
 184 }
 185
 186 UDPNameserver::UDPNameserver()
 187 {
 188   d_highfd=0;
 189   FD_ZERO(&d_rfds);
 190   if(!arg()["local-address"].empty())
 191     bindIPv4();
 192   if(!arg()["local-ipv6"].empty())
 193     bindIPv6();
 194
 195   if(arg()["local-address"].empty() && arg()["local-ipv6"].empty())
 196     L<<Logger::Critical<<"PDNS is deaf and mute! Not listening on any interfaces"<<endl;
 197
 198 }
 199
 200 void UDPNameserver::send(DNSPacket *p)
 201 {
 202   const char *buffer=p->getData();
 203   DLOG(L<<Logger::Notice<<"Sending a packet to "<<inet_ntoa( reinterpret_cast< sockaddr_in * >(( p->remote ))->sin_addr)<<" ("<<p->len<<" octets)"<<endl);
 204   if(p->len>512) {
 205     p=new DNSPacket(*p);
 206     p->truncate(512);
 207     buffer=p->getData();
 208     if(sendto(p->getSocket(),buffer,p->len,0,(struct sockaddr *)(p->remote),p->d_socklen)<0)
 209       L<<Logger::Error<<"Error sending reply with sendto (socket="<<p->getSocket()<<"): "<<strerror(errno)<<endl;
 210     delete p;
 211   }
 212   else {
 213
 214     if(sendto(p->getSocket(),buffer,p->len,0,(struct sockaddr *)(p->remote),p->d_socklen)<0)
 215       L<<Logger::Error<<"Error sending reply with sendto (socket="<<p->getSocket()<<"): "<<strerror(errno)<<endl;
 216
 217
 218
 219   }
 220 }
 221