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pdns-recursor 4.0.4-1+deb9u3~bpo8+1
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/*
 * This file is part of PowerDNS or dnsdist.
 * Copyright -- PowerDNS.COM B.V. and its contributors
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * In addition, for the avoidance of any doubt, permission is granted to
 * link this program with OpenSSL and to (re)distribute the binaries
 * produced as the result of such linking.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "utility.hh"
#include "lwres.hh"
#include <iostream>
#include "dnsrecords.hh"
#include <errno.h>
#include "misc.hh"
#include <algorithm>
#include <sstream>
#include <cstring>
#include <string>
#include <vector>
#include "dns.hh"
#include "qtype.hh"
#include "pdnsexception.hh"
#include "arguments.hh"
#include "sstuff.hh"
#include "syncres.hh"
#include "dnswriter.hh"
#include "dnsparser.hh"
#include "logger.hh"
#include "dns_random.hh"
#include <boost/scoped_array.hpp>
#include <boost/algorithm/string.hpp>
#include "validate-recursor.hh"
#include "ednssubnet.hh"

//! returns -2 for OS limits error, -1 for permanent error that has to do with remote **transport**, 0 for timeout, 1 for success
/** lwr is only filled out in case 1 was returned, and even when returning 1 for 'success', lwr might contain DNS errors
    Never throws! 
 */
int asyncresolve(const ComboAddress& ip, const DNSName& domain, int type, bool doTCP, bool sendRDQuery, int EDNS0Level, struct timeval* now, boost::optional<Netmask>& srcmask, LWResult *lwr)
{
  size_t len;
  size_t bufsize=g_outgoingEDNSBufsize;
  scoped_array<unsigned char> buf(new unsigned char[bufsize]);
  vector<uint8_t> vpacket;
  //  string mapped0x20=dns0x20(domain);
  DNSPacketWriter pw(vpacket, domain, type);

  pw.getHeader()->rd=sendRDQuery;
  pw.getHeader()->id=dns_random(0xffff);
  /* RFC 6840 section 5.9:
   *  This document further specifies that validating resolvers SHOULD set
   *  the CD bit on every upstream query.  This is regardless of whether
   *  the CD bit was set on the incoming query [...]
   *
   * sendRDQuery is only true if the qname is part of a forward-zone-recurse (or
   * set in the forward-zone-file), so we use this as an indicator for it being
   * an "upstream query". To stay true to "dnssec=off means 3.X behaviour", we
   * only set +CD on forwarded query in any mode other than dnssec=off.
   */
  pw.getHeader()->cd=(sendRDQuery && g_dnssecmode != DNSSECMode::Off);

  string ping;
  bool weWantEDNSSubnet=false;
  if(EDNS0Level) { 
    DNSPacketWriter::optvect_t opts;
    if(srcmask) {
      EDNSSubnetOpts eo;
      eo.source = *srcmask;
      //      cout<<"Adding request mask: "<<eo.source.toString()<<endl;
      opts.push_back(make_pair(8, makeEDNSSubnetOptsString(eo)));
      srcmask=boost::optional<Netmask>(); // this is also our return value
      weWantEDNSSubnet=true;
    }

    pw.addOpt(g_outgoingEDNSBufsize, 0, g_dnssecmode == DNSSECMode::Off ? 0 : EDNSOpts::DNSSECOK, opts); 
    pw.commit();
  }
  lwr->d_rcode = 0;
  lwr->d_haveEDNS = false;
  int ret;

  DTime dt;
  dt.set();
  *now=dt.getTimeval();
  errno=0;
  if(!doTCP) {
    int queryfd;
    if(ip.sin4.sin_family==AF_INET6)
      g_stats.ipv6queries++;

    if((ret=asendto((const char*)&*vpacket.begin(), vpacket.size(), 0, ip, pw.getHeader()->id,
                    domain, type, &queryfd)) < 0) {
      return ret; // passes back the -2 EMFILE
    }
  
    // sleep until we see an answer to this, interface to mtasker
    
    ret=arecvfrom(reinterpret_cast<char *>(buf.get()), bufsize-1,0, ip, &len, pw.getHeader()->id, 
                  domain, type, queryfd, now);
  }
  else {
    try {
      Socket s(ip.sin4.sin_family, SOCK_STREAM);

      s.setNonBlocking();
      ComboAddress local = getQueryLocalAddress(ip.sin4.sin_family, 0);

      s.bind(local);
        
      ComboAddress remote = ip;
      remote.sin4.sin_port = htons(53);      
      s.connect(remote);
      
      uint16_t tlen=htons(vpacket.size());
      char *lenP=(char*)&tlen;
      const char *msgP=(const char*)&*vpacket.begin();
      string packet=string(lenP, lenP+2)+string(msgP, msgP+vpacket.size());
      
      ret=asendtcp(packet, &s);
      if(!(ret>0))           
        return ret;
      
      packet.clear();
      ret=arecvtcp(packet, 2, &s, false);
      if(!(ret > 0))
        return ret;
      
      memcpy(&tlen, packet.c_str(), sizeof(tlen));
      len=ntohs(tlen); // switch to the 'len' shared with the rest of the function
      
      ret=arecvtcp(packet, len, &s, false);
      if(!(ret > 0))
        return ret;
      
      if(len > bufsize) {
        bufsize=len;
        scoped_array<unsigned char> narray(new unsigned char[bufsize]);
        buf.swap(narray);
      }
      memcpy(buf.get(), packet.c_str(), len);

      ret=1;
    }
    catch(NetworkError& ne) {
      ret = -2; // OS limits error
    }
  }

  
  lwr->d_usec=dt.udiff();
  *now=dt.getTimeval();

  if(ret <= 0) // includes 'timeout'
    return ret;

  lwr->d_records.clear();
  try {
    lwr->d_tcbit=0;
    MOADNSParser mdp(false, (const char*)buf.get(), len);
    lwr->d_aabit=mdp.d_header.aa;
    lwr->d_tcbit=mdp.d_header.tc;
    lwr->d_rcode=mdp.d_header.rcode;
    
    if(mdp.d_header.rcode == RCode::FormErr && mdp.d_qname.empty() && mdp.d_qtype == 0 && mdp.d_qclass == 0) {
      return 1; // this is "success", the error is set in lwr->d_rcode
    }

    if(domain != mdp.d_qname) { 
      if(!mdp.d_qname.empty() && domain.toString().find((char)0) == string::npos /* ugly */) {// embedded nulls are too noisy, plus empty domains are too
        L<<Logger::Notice<<"Packet purporting to come from remote server "<<ip.toString()<<" contained wrong answer: '" << domain << "' != '" << mdp.d_qname << "'" << endl;
      }
      // unexpected count has already been done @ pdns_recursor.cc
      goto out;
    }
    
    for(const auto& a : mdp.d_answers)
      lwr->d_records.push_back(a.first);

    EDNSOpts edo;
    if(EDNS0Level > 0 && getEDNSOpts(mdp, &edo)) {
      lwr->d_haveEDNS = true;

      if(weWantEDNSSubnet) {
        for(const auto& opt : edo.d_options) {
          if(opt.first==8) {
            EDNSSubnetOpts reso;
            if(getEDNSSubnetOptsFromString(opt.second, &reso)) {
              //	    cerr<<"EDNS Subnet response: "<<reso.source.toString()<<", scope: "<<reso.scope.toString()<<", family = "<<reso.scope.getNetwork().sin4.sin_family<<endl;
              if(reso.scope.getBits())
                srcmask = reso.scope;
            }
          }
        }
      }
    }
        
    return 1;
  }
  catch(std::exception &mde) {
    if(::arg().mustDo("log-common-errors"))
      L<<Logger::Notice<<"Unable to parse packet from remote server "<<ip.toString()<<": "<<mde.what()<<endl;
    lwr->d_rcode = RCode::FormErr;
    g_stats.serverParseError++; 
    return 1; // success - oddly enough
  }
  catch(...) {
    L<<Logger::Notice<<"Unknown error parsing packet from remote server"<<endl;
  }
  
  g_stats.serverParseError++; 
  
 out:
  if(!lwr->d_rcode)
    lwr->d_rcode=RCode::ServFail;

  return -1;
}