pdns/lwres.cc

   1 /*
   2     PowerDNS Versatile Database Driven Nameserver
   3     Copyright (C) 2002 - 2010 PowerDNS.COM BV
   4
   5     This program is free software; you can redistribute it and/or modify
   6     it under the terms of the GNU General Public License version 2 as
   7     published by the Free Software Foundation
   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., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  17 */
  18
  19
  20 #include "utility.hh"
  21 #include "lwres.hh"
  22 #include <iostream>
  23 #include "dnsrecords.hh"
  24 #include <errno.h>
  25 #include "misc.hh"
  26 #include <algorithm>
  27 #include <sstream>
  28 #include <cstring>
  29 #include <string>
  30 #include <vector>
  31 #include "dns.hh"
  32 #include "qtype.hh"
  33 #include "ahuexception.hh"
  34 #include "arguments.hh"
  35 #include "sstuff.hh"
  36 #include "syncres.hh"
  37 #include "dnswriter.hh"
  38 #include "dnsparser.hh"
  39 #include "logger.hh"
  40 #include "dns_random.hh"
  41 #include <boost/scoped_array.hpp>
  42 #include <boost/algorithm/string.hpp>
  43
  44 string dns0x20(const std::string& in)
  45 {
  46   string ret(in);
  47   string::size_type len=ret.size();
  48   for(string::size_type pos = 0 ; pos < len; ++pos) {
  49     if(isalpha(in[pos]) && dns_random(2))
  50       ret[pos]^=0x20;
  51   }
  52   //  cerr<<"'"<<in<<"' -> '"<<ret<<"'\n";
  53   return ret;
  54 }
  55
  56 //! returns -2 for OS limits error, -1 for permanent error that has to do with remote **transport**, 0 for timeout, 1 for success
  57 /** lwr is only filled out in case 1 was returned, and even when returning 1 for 'success', lwr might contain DNS errors
  58     Never throws!
  59  */
  60 int asyncresolve(const ComboAddress& ip, const string& domain, int type, bool doTCP, bool sendRDQuery, int EDNS0Level, struct timeval* now, LWResult *lwr)
  61 {
  62   int len;
  63   int bufsize=1500;
  64   scoped_array<unsigned char> buf(new unsigned char[bufsize]);
  65   vector<uint8_t> vpacket;
  66   //  string mapped0x20=dns0x20(domain);
  67   DNSPacketWriter pw(vpacket, domain, type);
  68
  69   pw.getHeader()->rd=sendRDQuery;
  70   pw.getHeader()->id=dns_random(0xffff);
  71
  72   string ping;
  73
  74   uint32_t nonce=dns_random(0xffffffff);
  75   ping.assign((char*) &nonce, 4);
  76
  77   if(EDNS0Level && !doTCP) {
  78     DNSPacketWriter::optvect_t opts;
  79     if(EDNS0Level > 1) {
  80       opts.push_back(make_pair(5, ping));
  81     }
  82
  83     pw.addOpt(1200, 0, 0, opts); // 1200 bytes answer size
  84     pw.commit();
  85   }
  86   lwr->d_rcode = 0;
  87   lwr->d_pingCorrect = false;
  88   lwr->d_haveEDNS = false;
  89
  90   int ret;
  91
  92   DTime dt;
  93   dt.setTimeval(*now);
  94   errno=0;
  95   if(!doTCP) {
  96     int queryfd;
  97     if(ip.sin4.sin_family==AF_INET6)
  98       g_stats.ipv6queries++;
  99
 100     if((ret=asendto((const char*)&*vpacket.begin(), (int)vpacket.size(), 0, ip, pw.getHeader()->id,
 101                     domain, type, &queryfd)) < 0) {
 102       return ret; // passes back the -2 EMFILE
 103     }
 104
 105     // sleep until we see an answer to this, interface to mtasker
 106
 107     ret=arecvfrom(reinterpret_cast<char *>(buf.get()), bufsize-1,0, ip, &len, pw.getHeader()->id,
 108                   domain, type, queryfd, now);
 109   }
 110   else {
 111     try {
 112       Socket s((AddressFamily)ip.sin4.sin_family, Stream);
 113
 114       s.setNonBlocking();
 115       ComboAddress local = getQueryLocalAddress(ip.sin4.sin_family, 0);
 116
 117       s.bind(local);
 118
 119       ComboAddress remote = ip;
 120       remote.sin4.sin_port = htons(53);
 121       s.connect(remote);
 122
 123       uint16_t tlen=htons(vpacket.size());
 124       char *lenP=(char*)&tlen;
 125       const char *msgP=(const char*)&*vpacket.begin();
 126       string packet=string(lenP, lenP+2)+string(msgP, msgP+vpacket.size());
 127
 128       ret=asendtcp(packet, &s);
 129       if(!(ret>0))
 130         return ret;
 131
 132       packet.clear();
 133       ret=arecvtcp(packet, 2, &s);
 134       if(!(ret > 0))
 135         return ret;
 136
 137       memcpy(&tlen, packet.c_str(), 2);
 138       len=ntohs(tlen); // switch to the 'len' shared with the rest of the function
 139
 140       ret=arecvtcp(packet, len, &s);
 141       if(!(ret > 0))
 142         return ret;
 143
 144       if(len > bufsize) {
 145         bufsize=len;
 146         scoped_array<unsigned char> narray(new unsigned char[bufsize]);
 147         buf.swap(narray);
 148       }
 149       memcpy(buf.get(), packet.c_str(), len);
 150
 151       ret=1;
 152     }
 153     catch(NetworkError& ne) {
 154       ret = -2; // OS limits error
 155     }
 156   }
 157
 158
 159   lwr->d_usec=dt.udiff();
 160   *now=dt.getTimeval();
 161
 162   if(ret <= 0) // includes 'timeout'
 163     return ret;
 164
 165   lwr->d_result.clear();
 166   try {
 167     lwr->d_tcbit=0;
 168     MOADNSParser mdp((const char*)buf.get(), len);
 169     lwr->d_aabit=mdp.d_header.aa;
 170     lwr->d_tcbit=mdp.d_header.tc;
 171     lwr->d_rcode=mdp.d_header.rcode;
 172
 173     if(mdp.d_header.rcode == RCode::FormErr && mdp.d_qname.empty() && mdp.d_qtype == 0 && mdp.d_qclass == 0) {
 174       return 1; // this is "success", the error is set in lwr->d_rcode
 175     }
 176
 177     if(!pdns_iequals(domain, mdp.d_qname)) {
 178       if(!mdp.d_qname.empty() && domain.find((char)0) == string::npos) {// embedded nulls are too noisy, plus empty domains are too
 179         L<<Logger::Notice<<"Packet purporting to come from remote server "<<ip.toString()<<" contained wrong answer: '" << domain << "' != '" << mdp.d_qname << "'" << endl;
 180       }
 181       // unexpected count has already been done @ pdns_recursor.cc
 182       goto out;
 183     }
 184
 185     for(MOADNSParser::answers_t::const_iterator i=mdp.d_answers.begin(); i!=mdp.d_answers.end(); ++i) {
 186       DNSResourceRecord rr;
 187       rr.priority = 0;
 188       rr.qtype=i->first.d_type;
 189       rr.qname=i->first.d_label;
 190       rr.ttl=i->first.d_ttl;
 191       rr.content=i->first.d_content->getZoneRepresentation();  // this should be the serialised form
 192       rr.d_place=(DNSResourceRecord::Place) i->first.d_place;
 193       lwr->d_result.push_back(rr);
 194     }
 195
 196     EDNSOpts edo;
 197     if(EDNS0Level > 1 && getEDNSOpts(mdp, &edo)) {
 198       lwr->d_haveEDNS = true;
 199       for(vector<pair<uint16_t, string> >::const_iterator iter = edo.d_options.begin();
 200           iter != edo.d_options.end();
 201           ++iter) {
 202         if(iter->first == 5 || iter->first == 4) {// 'EDNS PING'
 203           if(iter->second == ping)  {
 204             lwr->d_pingCorrect = true;
 205           }
 206         }
 207       }
 208     }
 209
 210     return 1;
 211   }
 212   catch(std::exception &mde) {
 213     if(::arg().mustDo("log-common-errors"))
 214       L<<Logger::Notice<<"Unable to parse packet from remote server "<<ip.toString()<<": "<<mde.what()<<endl;
 215     lwr->d_rcode = RCode::FormErr;
 216     g_stats.serverParseError++;
 217     return 1; // success - oddly enough
 218   }
 219   catch(...) {
 220     L<<Logger::Notice<<"Unknown error parsing packet from remote server"<<endl;
 221   }
 222
 223   g_stats.serverParseError++;
 224
 225  out:
 226   if(!lwr->d_rcode)
 227     lwr->d_rcode=RCode::ServFail;
 228
 229   return -1;
 230 }
 231
 232