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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;
}
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