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add comments, fix typo

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This commit is contained in:
bert hubert 2018-10-16 17:49:42 +02:00
parent 2eb35588e0
commit f0866a77c4
1 changed files with 41 additions and 25 deletions
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66
tdns/tres.cc
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@ -21,7 +21,7 @@ bool g_skipIPv6{false}; //!< set this if you have no functioning IPv6
/** Helper function that extracts a useable IP address from an
A or AAAA resource record. Returns sin_family == 0 if it didn't work */
ComboAddress getIP(const std::unique_ptr<RRGen>& rr)
static ComboAddress getIP(const std::unique_ptr<RRGen>& rr)
{
ComboAddress ret;
ret.sin4.sin_family = 0;
@ -60,7 +60,7 @@ DNSMessageReader getResponse(const ComboAddress& server, const DNSName& dn, cons
dmw.dh.rd = false;
dmw.randomizeID();
if(doEDNS)
dmw.setEDNS(1500, false); // no DNSSEC for now
dmw.setEDNS(1500, false); // no DNSSEC for now, 1500 byte buffer size
string resp;
double timeout=1.0;
if(doTCP) {
@ -134,16 +134,19 @@ struct NxdomainException{};
//! Or if your type does not exist
struct NodataException{};
//! This describes a single resource record
struct ResolveRR
{
DNSName name;
uint32_t ttl;
std::unique_ptr<RRGen> rr;
};
//! This is the end result of our resolving work
struct ResolveResult
{
vector<ResolveRR> res;
vector<ResolveRR> intermediate;
vector<ResolveRR> res; //!< what you asked for
vector<ResolveRR> intermediate; //!< a CNAME chain that gets you there
void clear()
{
res.clear();
@ -151,6 +154,22 @@ struct ResolveResult
}
};
/** This takes a list of servers (in a specific order) and shuffles them to a vector.
This is to spread the load across nameservers
*/
static auto randomizeServers(const multimap<DNSName, ComboAddress>& mservers)
{
vector<pair<DNSName, ComboAddress> > servers;
for(auto& sp : mservers)
servers.push_back(sp);
std::random_device rd;
std::mt19937 g(rd());
std::shuffle(servers.begin(), servers.end(), g);
return servers;
}
/** This attempts to look up the name dn with type dt. The depth parameter is for
trace output.
the 'auth' field describes the authority of the servers we will be talking to. Defaults to root ('believe everything')
@ -167,19 +186,13 @@ ResolveResult resolveAt(const DNSName& dn, const DNSType& dt, int depth=0, const
// it is good form to sort the servers in order of response time
// for tres, this is not done (since we have no memory), but we do randomize:
vector<pair<DNSName, ComboAddress> > servers;
for(auto& sp : mservers)
servers.push_back(sp);
std::random_device rd;
std::mt19937 g(rd());
std::shuffle(servers.begin(), servers.end(), g);
auto servers = randomizeServers(mservers);
ResolveResult ret;
for(auto& sp : servers) {
ret.clear();
ComboAddress server=sp.second;
server.sin4.sin_port = htons(53);
server.sin4.sin_port = htons(53); // just to be sure
if(g_skipIPv6 && server.sin4.sin_family == AF_INET6)
continue;
@ -192,7 +205,7 @@ ResolveResult resolveAt(const DNSName& dn, const DNSType& dt, int depth=0, const
DNSName rrdn, newAuth;
DNSType rrdt;
dmr.getQuestion(rrdn, rrdt); // parse
dmr.getQuestion(rrdn, rrdt); // parse into rrdn and rrdt
cout << prefix<<"Received response with RCode "<<(RCode)dmr.dh.rcode<<", qname " <<dn<<", qtype "<<dt<<", aa: "<<dmr.dh.aa << endl;
if(rrdn != dn || dt != rrdt) {
@ -222,13 +235,12 @@ ResolveResult resolveAt(const DNSName& dn, const DNSType& dt, int depth=0, const
while(dmr.getRR(rrsection, rrdn, rrdt, ttl, rr)) {
cout << prefix << rrsection<<" "<<rrdn<< " IN " << rrdt << " " << ttl << " " <<rr->toString()<<endl;
if(dmr.dh.aa==1) {
if(dn == rrdn && dt == rrdt) {
if(dmr.dh.aa==1) { // authoritative answer. We trust this.
if(rrsection == DNSSection::Answer && dn == rrdn && dt == rrdt) {
cout << prefix<<"We got an answer to our question!"<<endl;
ret.res.push_back({dn, ttl, std::move(rr)});
}
if(dn == rrdn && rrdt == DNSType::CNAME) {
DNSName target = dynamic_cast<CNAMEGen*>(rr.get())->d_name;
ret.intermediate.push_back({dn, ttl, std::move(rr)}); // rr is DEAD now!
cout << prefix<<"We got a CNAME to " << target <<", chasing"<<endl;
@ -252,7 +264,7 @@ ResolveResult resolveAt(const DNSName& dn, const DNSType& dt, int depth=0, const
auto chaseres=resolveAt(target, dt, depth + 1);
ret.res = std::move(chaseres.res);
for(auto& rr : chaseres.intermediate) // add up their intermediates
for(auto& rr : chaseres.intermediate) // add up their intermediates to ours
ret.intermediate.push_back(std::move(rr));
return ret;
}
@ -302,7 +314,7 @@ ResolveResult resolveAt(const DNSName& dn, const DNSType& dt, int depth=0, const
// well we could not make it work using the servers we had addresses for. Let's try
// to get addresses for the rest
cout << prefix<<"Don't have a resolved nameserver to ask anymore, trying to resolve "<<nsses.size()<<" names"<<endl;
cout << prefix<<"Don't have a resolved nameserver to ask anymore, trying from "<<nsses.size()<<" unresolved names"<<endl;
for(const auto& name: nsses) {
multimap<DNSName, ComboAddress> newns;
@ -310,7 +322,7 @@ ResolveResult resolveAt(const DNSName& dn, const DNSType& dt, int depth=0, const
for(const DNSType& qtype : {DNSType::A, DNSType::AAAA}) {
try {
auto result = resolveAt(name, qtype, depth+1);
cout << prefix<<"Got "<<result.res.size()<<" nameserver IPv4 addresses, adding to list"<<endl;
cout << prefix<<"Got "<<result.res.size()<<" nameserver " << qtype <<" addresses, adding to list"<<endl;
for(const auto& res : result.res)
newns.insert({name, getIP(res.rr)});
}
@ -338,6 +350,7 @@ ResolveResult resolveAt(const DNSName& dn, const DNSType& dt, int depth=0, const
return ret;
}
//! This is a thread that will create an answer to the query in `dmr`
void processQuery(int sock, ComboAddress client, DNSMessageReader dmr)
try
{
@ -355,7 +368,8 @@ try
ResolveResult res;
try {
res = resolveAt(dn, dt);
cout<<"Result or query for "<< dn <<"|"<<toString(dt)<<endl;
cout<<"Result of query for "<< dn <<"|"<<toString(dt)<<endl;
for(const auto& r : res.intermediate) {
cout<<r.name <<" "<<r.ttl<<" "<<r.rr->getType()<<" " << r.rr->toString()<<endl;
}
@ -375,12 +389,13 @@ try
SSendto(sock, dmw.serialize(), client);
return;
}
// Put in the CNAME chain
for(const auto& rr : res.intermediate)
dmw.putRR(DNSSection::Answer, rr.name, rr.ttl, rr.rr);
for(const auto& rr : res.res)
for(const auto& rr : res.res) // and the actual answer
dmw.putRR(DNSSection::Answer, rr.name, rr.ttl, rr.rr);
string resp = dmw.serialize();
SSendto(sock, resp, client);
SSendto(sock, resp, client); // and send it!
}
catch(exception& e)
{
@ -411,6 +426,8 @@ try
DNSType rrdt;
uint32_t ttl;
std::unique_ptr<RRGen> rr;
// XXX should check if response name and type match query
// this assumes the root will only send us relevant NS records
// we could check with the NS records if we wanted
// but if a root wants to mess with us, it can
@ -425,9 +442,8 @@ try
cout<<"Retrieved . NSSET from hints, have "<<g_root.size()<<" addresses"<<endl;
if(argc == 2) {
ComboAddress local(argv[1]);
if(argc == 2) { // be a server
ComboAddress local(argv[1], 53);
Socket sock(local.sin4.sin_family, SOCK_DGRAM);
SBind(sock, local);
string packet;