root/trunk/pdns/pdns/syncres.cc @ 1628

/*
    PowerDNS Versatile Database Driven Nameserver
    Copyright (C) 2003 - 2010  PowerDNS.COM BV

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License version 2 as published 
    by the Free Software Foundation

    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 St, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include <boost/algorithm/string.hpp>
#include "utility.hh"
#include "syncres.hh"
#include <iostream>
#include <map>
#include <algorithm>
#include <set>
#include <cerrno>
#include <cstdio>
#include <cstdlib>
#include <utility>
#include <deque>
#include "logger.hh"
#include "misc.hh"
#include "arguments.hh"
#include "lwres.hh"
#include "recursor_cache.hh"
#include "dnsparser.hh"
#include "dns_random.hh"
#include "lock.hh"

__thread SyncRes::StaticStorage* t_sstorage;

unsigned int SyncRes::s_maxnegttl;
unsigned int SyncRes::s_maxcachettl;
unsigned int SyncRes::s_packetcachettl;
unsigned int SyncRes::s_packetcacheservfailttl;
unsigned int SyncRes::s_queries;
unsigned int SyncRes::s_outgoingtimeouts;
unsigned int SyncRes::s_outqueries;
unsigned int SyncRes::s_tcpoutqueries;
unsigned int SyncRes::s_throttledqueries;
unsigned int SyncRes::s_nodelegated;
unsigned int SyncRes::s_unreachables;
bool SyncRes::s_doIPv6;
bool SyncRes::s_nopacketcache;

string SyncRes::s_serverID;
bool SyncRes::s_log;

#define LOG if(s_log) L<<Logger::Warning

bool SyncRes::s_noEDNSPing;
bool SyncRes::s_noEDNS;

SyncRes::SyncRes(const struct timeval& now) :  d_outqueries(0), d_tcpoutqueries(0), d_throttledqueries(0), d_timeouts(0), d_unreachables(0),
                                                 d_now(now),
                                                 d_cacheonly(false), d_nocache(false), d_doEDNS0(false) 
{ 
  if(!t_sstorage) {
    t_sstorage = new StaticStorage();
  }
}

/** everything begins here - this is the entry point just after receiving a packet */
int SyncRes::beginResolve(const string &qname, const QType &qtype, uint16_t qclass, vector<DNSResourceRecord>&ret)
{
  s_queries++;
  
  if( (qtype.getCode() == QType::AXFR)) 
    return -1;
  
  if( (qtype.getCode()==QType::PTR && pdns_iequals(qname, "1.0.0.127.in-addr.arpa.")) ||
      (qtype.getCode()==QType::A && qname.length()==10 && pdns_iequals(qname, "localhost."))) {
    ret.clear();
    DNSResourceRecord rr;
    rr.qname=qname;
    rr.qtype=qtype;
    rr.qclass=1;
    rr.ttl=86400;
    if(qtype.getCode()==QType::PTR)
      rr.content="localhost.";
    else
      rr.content="127.0.0.1";
    ret.push_back(rr);
    return 0;
  }

  if(qclass==3 && qtype.getCode()==QType::TXT && 
        (pdns_iequals(qname, "version.bind.") || pdns_iequals(qname, "id.server.") || pdns_iequals(qname, "version.pdns.") ) 
     ) {
    ret.clear();
    DNSResourceRecord rr;
    rr.qname=qname;
    rr.qtype=qtype;
    rr.qclass=qclass;
    rr.ttl=86400;
    if(pdns_iequals(qname,"version.bind.")  || pdns_iequals(qname,"version.pdns."))
      rr.content="\""+::arg()["version-string"]+"\"";
    else
      rr.content="\""+s_serverID+"\"";
    ret.push_back(rr);
    return 0;
  }
  
  if(qclass==0xff)
    qclass=1;
  else if(qclass!=1)
    return -1;
  
  set<GetBestNSAnswer> beenthere;
  int res=doResolve(qname, qtype, ret, 0, beenthere);
  if(!res)
    addCruft(qname, ret);
  return res;
}

//! This is the 'out of band resolver', in other words, the authoritative server
bool SyncRes::doOOBResolve(const string &qname, const QType &qtype, vector<DNSResourceRecord>&ret, int depth, int& res)
{
  string prefix;
  if(s_log) {
    prefix=d_prefix;
    prefix.append(depth, ' ');
  }

  LOG<<prefix<<qname<<": checking auth storage for '"<<qname<<"|"<<qtype.getName()<<"'"<<endl;
  string authdomain(qname);

  domainmap_t::const_iterator iter=getBestAuthZone(&authdomain);
  if(iter==t_sstorage->domainmap->end()) {
    LOG<<prefix<<qname<<": auth storage has no zone for this query!"<<endl;
    return false;
  }
  LOG<<prefix<<qname<<": auth storage has data, zone='"<<authdomain<<"'"<<endl;
  pair<AuthDomain::records_t::const_iterator, AuthDomain::records_t::const_iterator> range;

  range=iter->second.d_records.equal_range(tie(qname)); // partial lookup

  ret.clear();
  AuthDomain::records_t::const_iterator ziter;
  bool somedata=false;
  for(ziter=range.first; ziter!=range.second; ++ziter) {
    somedata=true;
    if(qtype.getCode()==QType::ANY || ziter->qtype==qtype || ziter->qtype.getCode()==QType::CNAME)  // let rest of nameserver do the legwork on this one
      ret.push_back(*ziter);
  }
  if(!ret.empty()) {
    LOG<<prefix<<qname<<": exact match in zone '"<<authdomain<<"'"<<endl;
    res=0;
    return true;
  }
  if(somedata) {
    LOG<<prefix<<qname<<": found record in '"<<authdomain<<"', but nothing of the right type, sending SOA"<<endl;
    ziter=iter->second.d_records.find(make_tuple(authdomain, QType(QType::SOA)));
    if(ziter!=iter->second.d_records.end()) {
      DNSResourceRecord rr=*ziter;
      rr.d_place=DNSResourceRecord::AUTHORITY;
      ret.push_back(rr);
    }
    else
      LOG<<prefix<<qname<<": can't find SOA record '"<<authdomain<<"' in our zone!"<<endl;
    res=RCode::NoError;
    return true;
  }

  string nsdomain(qname);

  while(chopOffDotted(nsdomain) && !pdns_iequals(nsdomain, iter->first)) {
    range=iter->second.d_records.equal_range(make_tuple(nsdomain,QType(QType::NS))); 
    if(range.first==range.second)
      continue;

    for(ziter=range.first; ziter!=range.second; ++ziter) {
      DNSResourceRecord rr=*ziter;
      rr.d_place=DNSResourceRecord::AUTHORITY;
      ret.push_back(rr);
    }
  }
  if(ret.empty()) { 
    LOG<<prefix<<qname<<": no NS match in zone '"<<authdomain<<"' either, handing out SOA"<<endl;
    ziter=iter->second.d_records.find(make_tuple(authdomain, QType(QType::SOA)));
    if(ziter!=iter->second.d_records.end()) {
      DNSResourceRecord rr=*ziter;
      rr.d_place=DNSResourceRecord::AUTHORITY;
      ret.push_back(rr);
    }
    else
      LOG<<prefix<<qname<<": can't find SOA record '"<<authdomain<<"' in our zone!"<<endl;
    res=RCode::NXDomain;
  }
  else 
    res=0;

  return true;
}



void SyncRes::doEDNSDumpAndClose(int fd)
{
  FILE* fp=fdopen(fd, "w");
  fprintf(fp,"IP Address\tMode\tMode last updated at\n");

  for(ednsstatus_t::const_iterator iter = t_sstorage->ednsstatus.begin(); iter != t_sstorage->ednsstatus.end(); ++iter) {
    fprintf(fp, "%s\t%d\t%s", iter->first.toString().c_str(), (int)iter->second.mode, ctime(&iter->second.modeSetAt));
  }

  fclose(fp);
}

int SyncRes::asyncresolveWrapper(const ComboAddress& ip, const string& domain, int type, bool doTCP, bool sendRDQuery, struct timeval* now, LWResult* res) 
{
  /* what is your QUEST?
     the goal is to get as many remotes as possible on the highest level of hipness: EDNS PING responders.
     The levels are:

     -1) CONFIRMEDPINGER: Confirmed pinger!
     0) UNKNOWN Unknown state 
     1) EDNSNOPING: Honors EDNS0 if no PING is included
     2) EDNSPINGOK: Ignores EDNS0+PING, but does generate EDNS0 response
     3) EDNSIGNORANT: Ignores EDNS0+PING, gives replies without EDNS0 nor PING
     4) NOEDNS: Generates FORMERR on EDNS queries

     Everybody starts out assumed to be '0'.
     If '-1', send out EDNS0+Ping
        If we get a FormErr, ignore
        If we get a incorrect PING, ignore
        If we get no PING, ignore
     If '0', send out EDNS0+Ping
        If we get a pure EDNS response, you are downgraded to '2'. 
        If you FORMERR us, go to '1', 
        If no EDNS in response, go to '3' - 3 and 0 are really identical, except confirmed
        If with correct PING, upgrade to -1
     If '1', send out EDNS0, no PING
        If FORMERR, downgrade to 4
     If '2', keep on including EDNS0+PING, just don't expect PING to be correct
        If PING correct, move to '0', and cheer in the log file!
     If '3', keep on including EDNS0+PING, see what happens
        Same behaviour as 0 
     If '4', send bare queries
  */

  if(s_noEDNS) {
    g_stats.noEdnsOutQueries++;
    return asyncresolve(ip, domain, type, doTCP, sendRDQuery, 0, now, res);
  }

  SyncRes::EDNSStatus* ednsstatus;
  ednsstatus = &t_sstorage->ednsstatus[ip];

  if(ednsstatus->modeSetAt && ednsstatus->modeSetAt + 3600 < d_now.tv_sec) {
    *ednsstatus=SyncRes::EDNSStatus();
    //    cerr<<"Resetting EDNS Status for "<<ip.toString()<<endl;
  }

  if(s_noEDNSPing && ednsstatus->mode == EDNSStatus::UNKNOWN)
    ednsstatus->mode = EDNSStatus::EDNSNOPING;

  SyncRes::EDNSStatus::EDNSMode& mode=ednsstatus->mode;
  SyncRes::EDNSStatus::EDNSMode oldmode = mode;
  int EDNSLevel=0;

  int ret;
  for(int tries = 0; tries < 3; ++tries) {
    //    cerr<<"Remote '"<<ip.toString()<<"' currently in mode "<<mode<<endl;

    if(mode==EDNSStatus::CONFIRMEDPINGER || mode==EDNSStatus::UNKNOWN || mode==EDNSStatus::EDNSPINGOK || mode==EDNSStatus::EDNSIGNORANT)
      EDNSLevel = 2;
    else if(mode==EDNSStatus::EDNSNOPING) {
      EDNSLevel = 1;
      g_stats.noPingOutQueries++;
    }
    else if(mode==EDNSStatus::NOEDNS) {
      g_stats.noEdnsOutQueries++;
      EDNSLevel = 0;
    }

    ret=asyncresolve(ip, domain, type, doTCP, sendRDQuery, EDNSLevel, now, res);
    if(ret == 0 || ret < 0) {
      //      cerr<<"Transport error or timeout (ret="<<ret<<"), no change in mode"<<endl;
      return ret;
    }

    if(mode== EDNSStatus::CONFIRMEDPINGER) {  // confirmed pinger!
      if(!res->d_pingCorrect) {
        L<<Logger::Error<<"Confirmed EDNS-PING enabled host "<<ip.toString()<<" did not send back correct ping"<<endl;
        //      perhaps lower some kind of count here, don't want to punnish a downgrader too long!
        ret = 0;
        res->d_rcode = RCode::ServFail;
        g_stats.ednsPingMismatches++;
      }
      else {
        g_stats.ednsPingMatches++;
        ednsstatus->modeSetAt=d_now.tv_sec; // only the very best mode self-perpetuates
      }
    }
    else if(mode==EDNSStatus::UNKNOWN || mode==EDNSStatus::EDNSPINGOK || mode == EDNSStatus::EDNSIGNORANT ) {
      if(res->d_rcode == RCode::FormErr)  {
        //      cerr<<"Downgrading to EDNSNOPING because of FORMERR!"<<endl;
        mode = EDNSStatus::EDNSNOPING;
        continue;
      }
      else if(mode==EDNSStatus::UNKNOWN && (res->d_rcode == RCode::Refused || res->d_rcode == RCode::NotImp) ) { // this "fixes" F5
        //      cerr<<"Downgrading an unknown status to EDNSNOPING because of RCODE="<<res->d_rcode<<endl;
        mode = EDNSStatus::EDNSNOPING;
        continue;
      }
      else if(!res->d_pingCorrect && res->d_haveEDNS) 
        mode = EDNSStatus::EDNSPINGOK;
      else if(res->d_pingCorrect) {
        L<<Logger::Warning<<"We welcome "<<ip.toString()<<" to the land of EDNS-PING!"<<endl;
        mode = EDNSStatus::CONFIRMEDPINGER;
        g_stats.ednsPingMatches++;
      }
      else if(!res->d_haveEDNS) {
        if(mode != EDNSStatus::EDNSIGNORANT) {
          mode = EDNSStatus::EDNSIGNORANT;
          //      cerr<<"We find that "<<ip.toString()<<" is an EDNS-ignorer, moving to mode 3"<<endl;
        }
      }
    }
    else if(mode==EDNSStatus::EDNSNOPING) {
      if(res->d_rcode == RCode::FormErr) {
        //              cerr<<"Downgrading to mode 4, FORMERR!"<<endl;
        mode = EDNSStatus::NOEDNS;
        continue;
      }
    }
    else if(mode==EDNSStatus::EDNSPINGOK) {
      if(res->d_pingCorrect) {
        // an upgrade!
        L<<Logger::Warning<<"We welcome "<<ip.toString()<<" to the land of EDNS-PING!"<<endl;
        mode = EDNSStatus::CONFIRMEDPINGER;
      }
    }
    if(oldmode != mode)
      ednsstatus->modeSetAt=d_now.tv_sec;
    //        cerr<<"Result: ret="<<ret<<", EDNS-level: "<<EDNSLevel<<", haveEDNS: "<<res->d_haveEDNS<<", EDNS-PING correct: "<<res->d_pingCorrect<<", new mode: "<<mode<<endl;  
    
    return ret;
  }
  return ret;
}

int SyncRes::doResolve(const string &qname, const QType &qtype, vector<DNSResourceRecord>&ret, int depth, set<GetBestNSAnswer>& beenthere)
{
  string prefix;
  if(s_log) {
    prefix=d_prefix;
    prefix.append(depth, ' ');
  }
  
  int res=0;
  if(!(d_nocache && qtype.getCode()==QType::NS && qname==".")) {
    if(d_cacheonly) { // very limited OOB support
      LWResult lwr;
      LOG<<prefix<<qname<<": Recursion not requested for '"<<qname<<"|"<<qtype.getName()<<"', peeking at auth/forward zones"<<endl;
      string authname(qname);
      domainmap_t::const_iterator iter=getBestAuthZone(&authname);
      if(iter != t_sstorage->domainmap->end()) {
        const vector<ComboAddress>& servers = iter->second.d_servers;
        if(servers.empty()) {
          ret.clear();
          doOOBResolve(qname, qtype, ret, depth, res);
          return res;
        }
        else {
          const ComboAddress remoteIP = servers.front();
          LOG<<prefix<<qname<<": forwarding query to hardcoded nameserver '"<< remoteIP.toStringWithPort()<<"' for zone '"<<authname<<"'"<<endl;

          res=asyncresolveWrapper(remoteIP, qname, qtype.getCode(), false, false, &d_now, &lwr);    
          // filter out the good stuff from lwr.result()

          for(LWResult::res_t::const_iterator i=lwr.d_result.begin();i!=lwr.d_result.end();++i) {
            if(i->d_place == DNSResourceRecord::ANSWER)
              ret.push_back(*i);
          }
          return res;
        }
      }
    }

    if(doCNAMECacheCheck(qname,qtype,ret,depth,res)) // will reroute us if needed
      return res;
    
    if(doCacheCheck(qname,qtype,ret,depth,res)) // we done
      return res;
  }

  if(d_cacheonly)
    return 0;
    
  LOG<<prefix<<qname<<": No cache hit for '"<<qname<<"|"<<qtype.getName()<<"', trying to find an appropriate NS record"<<endl;

  string subdomain(qname);

  set<string, CIStringCompare> nsset;
  bool flawedNSSet=false;
  for(int tries=0;tries<2 && nsset.empty();++tries) {
    subdomain=getBestNSNamesFromCache(subdomain, nsset, &flawedNSSet, depth, beenthere); //  pass beenthere to both occasions

    if(nsset.empty()) { // must've lost root records
      set<DNSResourceRecord> rootset;
      /* this additional test is needed since getBestNSNamesFromCache sometimes returns that no
         useful NS records were found, even without the root being expired. This might for example
         be the case when the . records are not acceptable because they are part of a loop, a loop
         caused by the invalidation of an nsset during the resolution algorithm */
      if(t_RC->get(d_now.tv_sec, ".", QType(QType::NS), &rootset) <= 0) {
        L<<Logger::Warning<<prefix<<qname<<": our root expired, repriming from hints and retrying"<<endl;
        primeHints();
      }
    }
  }

  if(!(res=doResolveAt(nsset, subdomain, flawedNSSet, qname, qtype, ret, depth, beenthere)))
    return 0;
  
  LOG<<prefix<<qname<<": failed (res="<<res<<")"<<endl;
  return res<0 ? RCode::ServFail : res;
}

// for testing purpoises
static bool ipv6First(const ComboAddress& a, const ComboAddress& b)
{
  return !(a.sin4.sin_family < a.sin4.sin_family);
}

/** This function explicitly goes out for A addresses, but if configured to use IPv6 as well, will also return any IPv6 addresses in the cache
    Additionally, it will return the 'best' address up front, and the rest shufled
*/
vector<ComboAddress> SyncRes::getAs(const string &qname, int depth, set<GetBestNSAnswer>& beenthere)
{
  typedef vector<DNSResourceRecord> res_t;
  res_t res;

  typedef vector<ComboAddress> ret_t;
  ret_t ret;

  if(!doResolve(qname, s_doIPv6 ? QType(QType::ADDR) : QType(QType::A), res,depth+1,beenthere) && !res.empty()) {  // this consults cache, OR goes out
    for(res_t::const_iterator i=res.begin(); i!= res.end(); ++i) {
      if(i->qtype.getCode()==QType::A || i->qtype.getCode()==QType::AAAA) {
        ret.push_back(ComboAddress(i->content, 53));
      }
    }
  }
  
  if(ret.size() > 1) {
    random_shuffle(ret.begin(), ret.end(), dns_random);

    // move 'best' address for this nameserver name up front
    nsspeeds_t::iterator best = t_sstorage->nsSpeeds.find(qname);  

    if(best != t_sstorage->nsSpeeds.end())
      for(ret_t::iterator i=ret.begin(); i != ret.end(); ++i) {  
        if(*i==best->second.d_best) {  // got the fastest one
          if(i!=ret.begin()) {
            *i=*ret.begin();
            *ret.begin()=best->second.d_best;
          }
          break;
        }
      }
  }

  return ret;
}

void SyncRes::getBestNSFromCache(const string &qname, set<DNSResourceRecord>&bestns, bool* flawedNSSet, int depth, set<GetBestNSAnswer>& beenthere)
{
  string prefix, subdomain(qname);
  if(s_log) {
    prefix=d_prefix;
    prefix.append(depth, ' ');
  }
  bestns.clear();

  do {
    LOG<<prefix<<qname<<": Checking if we have NS in cache for '"<<subdomain<<"'"<<endl;
    set<DNSResourceRecord> ns;
    *flawedNSSet = false;
    if(t_RC->get(d_now.tv_sec, subdomain, QType(QType::NS), &ns) > 0) {
      for(set<DNSResourceRecord>::const_iterator k=ns.begin();k!=ns.end();++k) {
        if(k->ttl > (unsigned int)d_now.tv_sec ) { 
          set<DNSResourceRecord> aset;

          DNSResourceRecord rr=*k;
          rr.content=k->content;
          if(!dottedEndsOn(rr.content, subdomain) || t_RC->get(d_now.tv_sec, rr.content, s_doIPv6 ? QType(QType::ADDR) : QType(QType::A),
                                                            s_log ? &aset : 0) > 5) {
            bestns.insert(rr);
            LOG<<prefix<<qname<<": NS (with ip, or non-glue) in cache for '"<<subdomain<<"' -> '"<<rr.content<<"'"<<endl;
            LOG<<prefix<<qname<<": within bailiwick: "<<dottedEndsOn(rr.content, subdomain);
            if(!aset.empty()) {
              LOG<<",  in cache, ttl="<<(unsigned int)(((time_t)aset.begin()->ttl- d_now.tv_sec ))<<endl;
            }
            else {
              LOG<<", not in cache / did not look at cache"<<endl;
            }
          }
          else {
            *flawedNSSet=true;
            LOG<<prefix<<qname<<": NS in cache for '"<<subdomain<<"', but needs glue ("<<k->content<<") which we miss or is expired"<<endl;
          }
        }
      }
      if(!bestns.empty()) {
        GetBestNSAnswer answer;
        answer.qname=qname; answer.bestns=bestns;
        if(beenthere.count(answer)) {
          LOG<<prefix<<qname<<": We have NS in cache for '"<<subdomain<<"' but part of LOOP! Trying less specific NS"<<endl;
          if(s_log)
            for( set<GetBestNSAnswer>::const_iterator j=beenthere.begin();j!=beenthere.end();++j)
              LOG<<prefix<<qname<<": beenthere: "<<j->qname<<" ("<<(unsigned int)j->bestns.size()<<")"<<endl;
          bestns.clear();
        }
        else {
          beenthere.insert(answer);
          LOG<<prefix<<qname<<": We have NS in cache for '"<<subdomain<<"' (flawedNSSet="<<*flawedNSSet<<")"<<endl;
          return;
        }
      }
    }
    LOG<<prefix<<qname<<": no valid/useful NS in cache for '"<<subdomain<<"'"<<endl;
  }while(chopOffDotted(subdomain));
}

SyncRes::domainmap_t::const_iterator SyncRes::getBestAuthZone(string* qname)
{
  SyncRes::domainmap_t::const_iterator ret;
  do {
    ret=t_sstorage->domainmap->find(*qname);
    if(ret!=t_sstorage->domainmap->end()) 
      break;
  }while(chopOffDotted(*qname));
  return ret;
}

/** doesn't actually do the work, leaves that to getBestNSFromCache */
string SyncRes::getBestNSNamesFromCache(const string &qname, set<string, CIStringCompare>& nsset, bool* flawedNSSet, int depth, set<GetBestNSAnswer>&beenthere)
{
  string subdomain(qname);
  string authdomain(qname);
  
  domainmap_t::const_iterator iter=getBestAuthZone(&authdomain);
  if(iter!=t_sstorage->domainmap->end()) {
    if( iter->second.d_servers.empty() )
      nsset.insert(string()); // this gets picked up in doResolveAt, if empty it means "we are auth", otherwise it denotes a forward
    else {
      for(vector<ComboAddress>::const_iterator server=iter->second.d_servers.begin(); server != iter->second.d_servers.end(); ++server)
        nsset.insert((iter->second.d_rdForward ? "+" : "-") + server->toStringWithPort()); // add a '+' if the rd bit should be set
    }

    return authdomain;
  }

  set<DNSResourceRecord> bestns;
  getBestNSFromCache(subdomain, bestns, flawedNSSet, depth, beenthere);

  for(set<DNSResourceRecord>::const_iterator k=bestns.begin();k!=bestns.end();++k) {
    nsset.insert(k->content);
    if(k==bestns.begin())
      subdomain=k->qname;
  }
  return subdomain;
}

bool SyncRes::doCNAMECacheCheck(const string &qname, const QType &qtype, vector<DNSResourceRecord>&ret, int depth, int &res)
{
  string prefix;
  if(s_log) {
    prefix=d_prefix; 
    prefix.append(depth, ' ');
  }

  if(depth>10) {
    LOG<<prefix<<qname<<": CNAME loop too deep, depth="<<depth<<endl;
    res=RCode::ServFail;
    return true;
  }
  
  LOG<<prefix<<qname<<": Looking for CNAME cache hit of '"<<(qname+"|CNAME")<<"'"<<endl;
  set<DNSResourceRecord> cset;
  if(t_RC->get(d_now.tv_sec, qname,QType(QType::CNAME),&cset) > 0) {

    for(set<DNSResourceRecord>::const_iterator j=cset.begin();j!=cset.end();++j) {
      if(j->ttl>(unsigned int) d_now.tv_sec) {
        LOG<<prefix<<qname<<": Found cache CNAME hit for '"<< (qname+"|CNAME") <<"' to '"<<j->content<<"'"<<endl;    
        DNSResourceRecord rr=*j;
        rr.ttl-=d_now.tv_sec;
        ret.push_back(rr);
        if(!(qtype==QType(QType::CNAME))) { // perhaps they really wanted a CNAME!
          set<GetBestNSAnswer>beenthere;
          res=doResolve(j->content, qtype, ret, depth+1, beenthere);
        }
        else
          res=0;
        return true;
      }
    }
  }
  LOG<<prefix<<qname<<": No CNAME cache hit of '"<< (qname+"|CNAME") <<"' found"<<endl;
  return false;
}




bool SyncRes::doCacheCheck(const string &qname, const QType &qtype, vector<DNSResourceRecord>&ret, int depth, int &res)
{
  bool giveNegative=false;
  
  string prefix;
  if(s_log) {
    prefix=d_prefix;
    prefix.append(depth, ' ');
  }

  string sqname(qname);
  QType sqt(qtype);
  uint32_t sttl=0;
  //  cout<<"Lookup for '"<<qname<<"|"<<qtype.getName()<<"'\n";
  
  pair<negcache_t::const_iterator, negcache_t::const_iterator> range=t_sstorage->negcache.equal_range(tie(qname));
  negcache_t::iterator ni;
  for(ni=range.first; ni != range.second; ni++) {
    // we have something
    if(ni->d_qtype.getCode() == 0 || ni->d_qtype == qtype) {
      res=0;
      if((uint32_t)d_now.tv_sec < ni->d_ttd) {
        sttl=ni->d_ttd - d_now.tv_sec;
        if(ni->d_qtype.getCode()) {
          LOG<<prefix<<qname<<": "<<qtype.getName()<<" is negatively cached via '"<<ni->d_qname<<"' for another "<<sttl<<" seconds"<<endl;
          res = RCode::NoError;
        }
        else {
          LOG<<prefix<<qname<<": Entire record '"<<qname<<"', is negatively cached via '"<<ni->d_qname<<"' for another "<<sttl<<" seconds"<<endl;
          res= RCode::NXDomain; 
        }
        giveNegative=true;
        sqname=ni->d_qname;
        sqt=QType::SOA;
        break;
      }
      else {
        LOG<<prefix<<qname<<": Entire record '"<<qname<<"' was negatively cached, but entry expired"<<endl;
      }
    }
  }


  set<DNSResourceRecord> cset;
  bool found=false, expired=false;

  if(t_RC->get(d_now.tv_sec, sqname, sqt, &cset) > 0) {
    LOG<<prefix<<sqname<<": Found cache hit for "<<sqt.getName()<<": ";
    for(set<DNSResourceRecord>::const_iterator j=cset.begin();j!=cset.end();++j) {
      LOG<<j->content;
      if(j->ttl>(unsigned int) d_now.tv_sec) {
        DNSResourceRecord rr=*j;
        rr.ttl-=d_now.tv_sec;
        if(giveNegative) {
          rr.d_place=DNSResourceRecord::AUTHORITY;
          rr.ttl=sttl;
        }
        ret.push_back(rr);
        LOG<<"[ttl="<<rr.ttl<<"] ";
        found=true;
      }
      else {
        LOG<<"[expired] ";
        expired=true;
      }
    }
  
    LOG<<endl;
    if(found && !expired) {
      if(!giveNegative)
        res=0;
      return true;
    }
    else
      LOG<<prefix<<qname<<": cache had only stale entries"<<endl;
  }

  return false;
}

bool SyncRes::moreSpecificThan(const string& a, const string &b)
{
  static string dot(".");
  int counta=(a!=dot), countb=(b!=dot);
  
  for(string::size_type n=0;n<a.size();++n)
    if(a[n]=='.')
      counta++;
  for(string::size_type n=0;n<b.size();++n)
    if(b[n]=='.')
      countb++;
  return counta>countb;
}

struct speedOrder
{
  speedOrder(map<string,double> &speeds) : d_speeds(speeds) {}
  bool operator()(const string &a, const string &b) const
  {
    return d_speeds[a] < d_speeds[b];
  }
  map<string,double>& d_speeds;
};

inline vector<string> SyncRes::shuffleInSpeedOrder(set<string, CIStringCompare> &nameservers, const string &prefix)
{
  vector<string> rnameservers;
  rnameservers.reserve(nameservers.size());
  map<string,double> speeds;

  for(set<string, CIStringCompare>::const_iterator i=nameservers.begin();i!=nameservers.end();++i) {
    rnameservers.push_back(*i);
    double speed;
    speed=t_sstorage->nsSpeeds[*i].get(&d_now);
    speeds[*i]=speed;
  }
  random_shuffle(rnameservers.begin(),rnameservers.end(), dns_random);
  speedOrder so(speeds);
  stable_sort(rnameservers.begin(),rnameservers.end(), so);
  
  if(s_log) {
    L<<Logger::Warning<<prefix<<"Nameservers: ";
    for(vector<string>::const_iterator i=rnameservers.begin();i!=rnameservers.end();++i) {
      if(i!=rnameservers.begin()) {
        L<<", ";
        if(!((i-rnameservers.begin())%3))
          L<<endl<<Logger::Warning<<prefix<<"             ";
      }
      L<<*i<<"(" << (int)(speeds[*i]/1000.0) <<"ms)";
    }
    L<<endl;
  }
  return rnameservers;
}

struct TCacheComp
{
  bool operator()(const pair<string, QType>& a, const pair<string, QType>& b) const
  {
    if(pdns_ilexicographical_compare(a.first, b.first))
      return true;
    if(pdns_ilexicographical_compare(b.first, a.first))   
      return false;
      
    return a.second < b.second;
  }
};

static bool magicAddrMatch(const QType& query, const QType& answer)
{
  if(query.getCode() != QType::ADDR)
    return false;
  return answer.getCode() == QType::A || answer.getCode() == QType::AAAA;
}

double g_avgLatency;

/** returns -1 in case of no results, rcode otherwise */
int SyncRes::doResolveAt(set<string, CIStringCompare> nameservers, string auth, bool flawedNSSet, const string &qname, const QType &qtype, 
                         vector<DNSResourceRecord>&ret, 
                         int depth, set<GetBestNSAnswer>&beenthere)
{
  string prefix;
  if(s_log) {
    prefix=d_prefix;
    prefix.append(depth, ' ');
  }
  
  LOG<<prefix<<qname<<": Cache consultations done, have "<<(unsigned int)nameservers.size()<<" NS to contact"<<endl;

  for(;;) { // we may get more specific nameservers
    vector<string> rnameservers=shuffleInSpeedOrder(nameservers, s_log ? (prefix+qname+": ") : string() );

    for(vector<string>::const_iterator tns=rnameservers.begin();;++tns) { 
      if(tns==rnameservers.end()) {
        LOG<<prefix<<qname<<": Failed to resolve via any of the "<<(unsigned int)rnameservers.size()<<" offered NS at level '"<<auth<<"'"<<endl;
        if(auth!="." && flawedNSSet) {
          LOG<<prefix<<qname<<": Ageing nameservers for level '"<<auth<<"', next query might succeed"<<endl;
          if(t_RC->doAgeCache(d_now.tv_sec, auth, QType::NS, 10))
            g_stats.nsSetInvalidations++;
        }
        return -1;
      }
      if(qname==*tns && qtype.getCode()==QType::A) {
        LOG<<prefix<<qname<<": Not using NS to resolve itself!"<<endl;
        continue;
      }

      typedef vector<ComboAddress> remoteIPs_t;
      remoteIPs_t remoteIPs;
      remoteIPs_t::const_iterator remoteIP;
      bool doTCP=false;
      int resolveret;
      bool pierceDontQuery=false;
      bool sendRDQuery=false;
      LWResult lwr;
      if(tns->empty()) {
        LOG<<prefix<<qname<<": Domain is out-of-band"<<endl;
        doOOBResolve(qname, qtype, lwr.d_result, depth, lwr.d_rcode);
        lwr.d_tcbit=false;
        lwr.d_aabit=true;
      }
      else {
        LOG<<prefix<<qname<<": Trying to resolve NS '"<<*tns<<"' ("<<1+tns-rnameservers.begin()<<"/"<<(unsigned int)rnameservers.size()<<")"<<endl;

        if(!isCanonical(*tns)) {
          LOG<<prefix<<qname<<": Domain has hardcoded nameserver(s)"<<endl;

          string txtAddr = *tns;
          if(!tns->empty()) {
            sendRDQuery = txtAddr[0] == '+';
            txtAddr=txtAddr.c_str()+1;
          }
          ComboAddress addr=parseIPAndPort(txtAddr, 53);
          
          remoteIPs.push_back(addr);
          pierceDontQuery=true;
        }
        else {
          remoteIPs=getAs(*tns, depth+1, beenthere);
          pierceDontQuery=false;
        }

        if(remoteIPs.empty()) {
          LOG<<prefix<<qname<<": Failed to get IP for NS "<<*tns<<", trying next if available"<<endl;
          flawedNSSet=true;
          continue;
        }
        else {
          LOG<<prefix<<qname<<": Resolved '"+auth+"' NS "<<*tns<<" to: ";
          for(remoteIP = remoteIPs.begin(); remoteIP != remoteIPs.end(); ++remoteIP) {
            if(remoteIP != remoteIPs.begin())
              LOG<<", ";
            LOG<<remoteIP->toString();
          }
          LOG<<endl;

        }

        for(remoteIP = remoteIPs.begin(); remoteIP != remoteIPs.end(); ++remoteIP) {
          LOG<<prefix<<qname<<": Trying IP "<< remoteIP->toStringWithPort() <<", asking '"<<qname<<"|"<<qtype.getName()<<"'"<<endl;
          extern NetmaskGroup* g_dontQuery;
          
          if(t_sstorage->throttle.shouldThrottle(d_now.tv_sec, make_tuple(*remoteIP, qname, qtype.getCode()))) {
            LOG<<prefix<<qname<<": query throttled "<<endl;
            s_throttledqueries++; d_throttledqueries++;
            continue;
          } 
          else if(!pierceDontQuery && g_dontQuery && g_dontQuery->match(&*remoteIP)) {
            LOG<<prefix<<qname<<": not sending query to " << remoteIP->toString() << ", blocked by 'dont-query' setting" << endl;
            continue;
          }
          else {
            s_outqueries++; d_outqueries++;
          TryTCP:
            if(doTCP) {
              LOG<<prefix<<qname<<": using TCP with "<< remoteIP->toStringWithPort() <<endl;
              s_tcpoutqueries++; d_tcpoutqueries++;
            }
            
            resolveret=asyncresolveWrapper(*remoteIP, qname, 
                                    (qtype.getCode() == QType::ADDR ? QType::ANY : qtype.getCode()), 
                                           doTCP, sendRDQuery, &d_now, &lwr);    // <- we go out on the wire!
            if(resolveret != 1) {
              if(resolveret==0) {
                LOG<<prefix<<qname<<": timeout resolving "<< (doTCP ? "over TCP" : "")<<endl;
                d_timeouts++;
                s_outgoingtimeouts++;
              }
              else if(resolveret==-2) {
                LOG<<prefix<<qname<<": hit a local resource limit resolving"<< (doTCP ? " over TCP" : "")<<", probable error: "<<stringerror()<<endl;
                g_stats.resourceLimits++;
              }
              else {
                s_unreachables++; d_unreachables++;
                LOG<<prefix<<qname<<": error resolving"<< (doTCP ? " over TCP" : "") <<", possible error: "<<strerror(errno)<< endl;
              }
              
              if(resolveret!=-2) { // don't account for resource limits, they are our own fault
                {
                  
                  t_sstorage->nsSpeeds[*tns].submit(*remoteIP, 1000000, &d_now); // 1 sec
                }
                if(resolveret==-1)
                  t_sstorage->throttle.throttle(d_now.tv_sec, make_tuple(*remoteIP, qname, qtype.getCode()), 60, 100); // unreachable
                else
                  t_sstorage->throttle.throttle(d_now.tv_sec, make_tuple(*remoteIP, qname, qtype.getCode()), 20, 5);  // timeout
              }
              continue;
            }
            
            break;  // this IP address worked!
          wasLame:; // well, it didn't
            LOG<<prefix<<qname<<": status=NS "<<*tns<<" ("<< remoteIP->toString() <<") is lame for '"<<auth<<"', trying sibling IP or NS"<<endl;
            t_sstorage->throttle.throttle(d_now.tv_sec, make_tuple(*remoteIP, qname, qtype.getCode()), 60, 100);
          }
        }
        
        if(remoteIP == remoteIPs.end())  // we tried all IP addresses, none worked
          continue; 
        
        if(lwr.d_tcbit) {
          if(!doTCP) {
            doTCP=true;
            LOG<<prefix<<qname<<": truncated bit set, retrying via TCP"<<endl;
            goto TryTCP;
          }
          LOG<<prefix<<qname<<": truncated bit set, over TCP?"<<endl;
          return RCode::ServFail;
        }
        
        if(lwr.d_rcode==RCode::ServFail) {
          LOG<<prefix<<qname<<": "<<*tns<<" returned a ServFail, trying sibling IP or NS"<<endl;
          t_sstorage->throttle.throttle(d_now.tv_sec,make_tuple(*remoteIP, qname, qtype.getCode()),60,3);
          continue;
        }
        LOG<<prefix<<qname<<": Got "<<(unsigned int)lwr.d_result.size()<<" answers from "<<*tns<<" ("<< remoteIP->toString() <<"), rcode="<<lwr.d_rcode<<", in "<<lwr.d_usec/1000<<"ms"<<endl;

        /*  // for you IPv6 fanatics :-)
        if(remoteIP->sin4.sin_family==AF_INET6)
          lwr.d_usec/=3;
        */
        //      cout<<"msec: "<<lwr.d_usec/1000.0<<", "<<g_avgLatency/1000.0<<'\n';
        double fract = 0.001;
        g_avgLatency = (1-fract) * g_avgLatency + fract * lwr.d_usec;

        t_sstorage->nsSpeeds[*tns].submit(*remoteIP, lwr.d_usec, &d_now);
      }

      typedef map<pair<string, QType>, set<DNSResourceRecord>, TCacheComp > tcache_t;
      tcache_t tcache;

      // reap all answers from this packet that are acceptable
      for(LWResult::res_t::iterator i=lwr.d_result.begin();i != lwr.d_result.end();++i) {
        if(i->qtype.getCode() == QType::OPT) {
          LOG<<prefix<<qname<<": skipping OPT answer '"<<i->qname<<"' from '"<<auth<<"' nameservers" <<endl;
          continue;
        }
        LOG<<prefix<<qname<<": accept answer '"<<i->qname<<"|"<<i->qtype.getName()<<"|"<<i->content<<"' from '"<<auth<<"' nameservers? ";
        if(i->qtype.getCode()==QType::ANY) {
          LOG<<"NO! - we don't accept 'ANY' data"<<endl;
          continue;
        }
          
        if(dottedEndsOn(i->qname, auth)) {
          if(lwr.d_aabit && lwr.d_rcode==RCode::NoError && i->d_place==DNSResourceRecord::ANSWER && ::arg().contains("delegation-only",auth)) {
            LOG<<"NO! Is from delegation-only zone"<<endl;
            s_nodelegated++;
            return RCode::NXDomain;
          }
          else {
            LOG<<"YES!"<<endl;

            i->ttl=min(s_maxcachettl, i->ttl);
            
            DNSResourceRecord rr=*i;
            rr.d_place=DNSResourceRecord::ANSWER;

            rr.ttl += d_now.tv_sec;

            if(rr.qtype.getCode() == QType::NS) // people fiddle with the case
              rr.content=toLower(rr.content); // this must stay! (the cache can't be case-insensitive on the RHS of records)
            
            tcache[make_pair(i->qname,i->qtype)].insert(rr);
          }
        }         
        else
          LOG<<"NO!"<<endl;
      }
    
      // supplant
      for(tcache_t::iterator i=tcache.begin();i!=tcache.end();++i) {
        if(i->second.size() > 1) {  // need to group the ttl to be the minimum of the RRSET (RFC 2181, 5.2)
          uint32_t lowestTTL=numeric_limits<uint32_t>::max();
          for(tcache_t::value_type::second_type::iterator j=i->second.begin(); j != i->second.end(); ++j)
            lowestTTL=min(lowestTTL, j->ttl);
          
          for(tcache_t::value_type::second_type::iterator j=i->second.begin(); j != i->second.end(); ++j)
            ((tcache_t::value_type::second_type::value_type*)&(*j))->ttl=lowestTTL;
        }

        t_RC->replace(d_now.tv_sec, i->first.first, i->first.second, i->second, lwr.d_aabit);
      }
      set<string, CIStringCompare> nsset;  
      LOG<<prefix<<qname<<": determining status after receiving this packet"<<endl;

      bool done=false, realreferral=false, negindic=false;
      string newauth, soaname, newtarget;

      for(LWResult::res_t::const_iterator i=lwr.d_result.begin();i!=lwr.d_result.end();++i) {
        if(i->d_place==DNSResourceRecord::AUTHORITY && dottedEndsOn(qname,i->qname) && i->qtype.getCode()==QType::SOA && 
           lwr.d_rcode==RCode::NXDomain) {
          LOG<<prefix<<qname<<": got negative caching indication for RECORD '"<<qname+"'"<<endl;
          ret.push_back(*i);

          NegCacheEntry ne;

          ne.d_qname=i->qname;
          ne.d_ttd=d_now.tv_sec + min(i->ttl, s_maxnegttl); // controversial
          ne.d_name=qname;
          ne.d_qtype=QType(0); // this encodes 'whole record'
          
          replacing_insert(t_sstorage->negcache, ne);
          
          negindic=true;
        }
        else if(i->d_place==DNSResourceRecord::ANSWER && pdns_iequals(i->qname, qname) && i->qtype.getCode()==QType::CNAME && (!(qtype==QType(QType::CNAME)))) {
          ret.push_back(*i);
          newtarget=i->content;
        }
        // for ANY answers we *must* have an authoritive answer
        else if(i->d_place==DNSResourceRecord::ANSWER && pdns_iequals(i->qname, qname) && 
                (
                 i->qtype==qtype || (lwr.d_aabit && (qtype==QType(QType::ANY) || magicAddrMatch(qtype, i->qtype) ) )
                ) 
               )   
          {
          
          LOG<<prefix<<qname<<": answer is in: resolved to '"<< i->content<<"|"<<i->qtype.getName()<<"'"<<endl;

          done=true;
          ret.push_back(*i);
        }
        else if(i->d_place==DNSResourceRecord::AUTHORITY && dottedEndsOn(qname,i->qname) && i->qtype.getCode()==QType::NS) { 
          if(moreSpecificThan(i->qname,auth)) {
            newauth=i->qname;
            LOG<<prefix<<qname<<": got NS record '"<<i->qname<<"' -> '"<<i->content<<"'"<<endl;
            realreferral=true;
          }
          else 
            LOG<<prefix<<qname<<": got upwards/level NS record '"<<i->qname<<"' -> '"<<i->content<<"', had '"<<auth<<"'"<<endl;
          nsset.insert(i->content);
        }
        else if(!done && i->d_place==DNSResourceRecord::AUTHORITY && dottedEndsOn(qname,i->qname) && i->qtype.getCode()==QType::SOA && 
           lwr.d_rcode==RCode::NoError) {
          LOG<<prefix<<qname<<": got negative caching indication for '"<< (qname+"|"+i->qtype.getName()+"'") <<endl;
          
          if(!newtarget.empty()) {
            LOG<<prefix<<qname<<": Hang on! Got a redirect to '"<<newtarget<<"' already"<<endl;
          }
          else {
            ret.push_back(*i);
            NegCacheEntry ne;
            ne.d_qname=i->qname;
            ne.d_ttd=d_now.tv_sec + min(s_maxnegttl, i->ttl);
            ne.d_name=qname;
            ne.d_qtype=qtype;
            if(qtype.getCode()) {  // prevents us from blacking out a whole domain
              replacing_insert(t_sstorage->negcache, ne);
            }
            negindic=true;
          }
        }
      }

      if(done){ 
        LOG<<prefix<<qname<<": status=got results, this level of recursion done"<<endl;
        return 0;
      }
      if(lwr.d_rcode==RCode::NXDomain) {
        LOG<<prefix<<qname<<": status=NXDOMAIN, we are done "<<(negindic ? "(have negative SOA)" : "")<<endl;
        return RCode::NXDomain;
      }
      if(!newtarget.empty()) {
        if(pdns_iequals(newtarget,qname)) {
          LOG<<prefix<<qname<<": status=got a CNAME referral to self, returning SERVFAIL"<<endl;
          return RCode::ServFail;
        }
        if(depth > 10) {
          LOG<<prefix<<qname<<": status=got a CNAME referral, but recursing too deep, returning SERVFAIL"<<endl;
          return RCode::ServFail;
        }
        LOG<<prefix<<qname<<": status=got a CNAME referral, starting over with "<<newtarget<<endl;

        set<GetBestNSAnswer> beenthere2;
        return doResolve(newtarget, qtype, ret, depth + 1, beenthere2);
      }
      if(nsset.empty() && !lwr.d_rcode) {
        LOG<<prefix<<qname<<": status=noerror, other types may exist, but we are done "<<(negindic ? "(have negative SOA)" : "")<<endl;
        return 0;
      }
      else if(realreferral) {
        LOG<<prefix<<qname<<": status=did not resolve, got "<<(unsigned int)nsset.size()<<" NS, looping to them"<<endl;
        auth=newauth;
        nameservers=nsset;
        break; 
      }
      else if(isCanonical(*tns)) {
        goto wasLame;
      }
    }
  }
  return -1;
}

static bool uniqueComp(const DNSResourceRecord& a, const DNSResourceRecord& b)
{
  return(a.qtype==b.qtype && a.qname==b.qname && a.content==b.content);
}

void SyncRes::addCruft(const string &qname, vector<DNSResourceRecord>& ret)
{
  for(vector<DNSResourceRecord>::const_iterator k=ret.begin();k!=ret.end();++k)  // don't add stuff to an NXDOMAIN!
    if(k->d_place==DNSResourceRecord::AUTHORITY && k->qtype==QType(QType::SOA))
      return;

  //  LOG<<qname<<": Adding best authority records from cache"<<endl;
  // addAuthorityRecords(qname,ret,0);
  // LOG<<qname<<": Done adding best authority records."<<endl;

  LOG<<d_prefix<<qname<<": Starting additional processing"<<endl;
  vector<DNSResourceRecord> addit;
  static optional<bool> l_doIPv6AP;
  if(!l_doIPv6AP)
    l_doIPv6AP=::arg().mustDo("aaaa-additional-processing");

  for(vector<DNSResourceRecord>::const_iterator k=ret.begin();k!=ret.end();++k) 
    if( (k->d_place==DNSResourceRecord::ANSWER && (k->qtype==QType(QType::MX) || k->qtype==QType(QType::SRV)))  || 
       ((k->d_place==DNSResourceRecord::AUTHORITY || k->d_place==DNSResourceRecord::ANSWER) && k->qtype==QType(QType::NS))) {
      LOG<<d_prefix<<qname<<": record '"<<k->content<<"|"<<k->qtype.getName()<<"' needs IP for additional processing"<<endl;
      set<GetBestNSAnswer> beenthere;
      vector<pair<string::size_type, string::size_type> > fields;
      vstringtok(fields, k->content, " ");
      string host;
      if(k->qtype==QType(QType::MX) && fields.size()==2)
        host=string(k->content.c_str() + fields[1].first, fields[1].second - fields[1].first);
      else if(k->qtype==QType(QType::NS))
        host=k->content;
      else if(k->qtype==QType(QType::SRV) && fields.size()==4)
        host=string(k->content.c_str() + fields[3].first, fields[3].second - fields[3].first);
      else 
        continue;
      doResolve(host, *l_doIPv6AP ? QType(QType::ADDR) : QType(QType::A), addit, 1, beenthere);
    }
  
  if(!addit.empty()) {
    sort(addit.begin(), addit.end());
    addit.erase(unique(addit.begin(), addit.end(), uniqueComp), addit.end());
    for(vector<DNSResourceRecord>::iterator k=addit.begin();k!=addit.end();++k) {
      if(k->qtype.getCode()==QType::A || k->qtype.getCode()==QType::AAAA) {
        k->d_place=DNSResourceRecord::ADDITIONAL;
        ret.push_back(*k);
      }
    }
  }
  LOG<<d_prefix<<qname<<": Done with additional processing"<<endl;
}

void SyncRes::addAuthorityRecords(const string& qname, vector<DNSResourceRecord>& ret, int depth)
{
  set<DNSResourceRecord> bestns;
  set<GetBestNSAnswer> beenthere;
  bool dontcare;
  getBestNSFromCache(qname, bestns, &dontcare, depth, beenthere);

  for(set<DNSResourceRecord>::const_iterator k=bestns.begin();k!=bestns.end();++k) {
    DNSResourceRecord ns=*k;
    ns.d_place=DNSResourceRecord::AUTHORITY;
    ns.ttl-=d_now.tv_sec;
    ret.push_back(ns);
  }
}