make DNSMessageWriter variable length

tdns/README.md

@@ -4,7 +4,7 @@
 
 # teaching DNS
 Welcome to tdns, the teaching authoritative server, implementing all of
-basic DNS in 1000 lines of code.
+basic DNS in ~~1000~~ 1100 lines of code.
 
 The goals of tdns are:
 
@@ -25,9 +25,9 @@ Features are complete:
  * Wildcards
  * Delegations
  * Glue records
+ * Truncation
 
 Missing:
- * Truncation
  * Compression (may not fit in the 1000 lines!)
  * EDNS (not 'basic' DNS by our definition, but ok)
 

tdns/contents.cc

@@ -7,14 +7,15 @@ void loadZones(DNSNode& zones)
   auto newzone = zone->zone = new DNSNode(); // XXX ICK
   
   newzone->addRRs(SOAGen::make({"ns1", "powerdns", "org"}, {"admin", "powerdns", "org"}, 1));
-  newzone->rrsets[DNSType::MX].add(MXGen::make(25, {"server1", "powerdns", "org"}));
+  newzone->addRRs(MXGen::make(25, {"server1", "powerdns", "org"}));
     
-  newzone->rrsets[DNSType::A].add(AGen::make("1.2.3.4"));
+  newzone->addRRs(AGen::make("1.2.3.4"));
-  newzone->rrsets[DNSType::AAAA].add(AAAAGen::make("::1"));
+  newzone->addRRs(AAAAGen::make("::1"));
   newzone->rrsets[DNSType::AAAA].ttl= 900;
-  newzone->rrsets[DNSType::NS].add(NSGen::make({"ns1", "powerdns", "org"}));
+  newzone->addRRs(NSGen::make({"ns1", "powerdns", "org"}), NSGen::make({"ns2", "powerdns", "org"}));
-  newzone->addRRs(TXTGen::make("Proudly served by tdns " __DATE__ " " __TIME__));
+  newzone->addRRs(TXTGen::make("Proudly served by tdns compiled on " __DATE__ " " __TIME__),
-
+                  TXTGen::make("This is some more filler to make this packet exceed 512 bytes"));
+  
   newzone->add({"www"})->rrsets[DNSType::CNAME].add(CNAMEGen::make({"server1","powerdns","org"}));
   newzone->add({"www2"})->rrsets[DNSType::CNAME].add(CNAMEGen::make({"nosuchserver1","powerdns","org"}));
 
@@ -25,7 +26,7 @@ void loadZones(DNSNode& zones)
   newzone->add({"*", "fr"})->rrsets[DNSType::CNAME].add(CNAMEGen::make({"server2", "powerdns", "org"}));
 
   newzone->add({"fra"})->addRRs(NSGen::make({"ns1","fra","powerdns","org"}), NSGen::make({"ns1","fra","powerdns","org"}));
-
+  newzone->add({"ns1"})->addRRs(AGen::make("212.13.14.15"));
   newzone->add({"ns1", "fra"})->addRRs(AGen::make("12.13.14.15"));
   newzone->add({"NS2", "fra"})->addRRs(AGen::make("12.13.14.16"), AAAAGen::make("::1"));
   newzone->add({"something"})->addRRs(AAAAGen::make("::1"), AGen::make("12.13.14.15"));

tdns/dns-types.cc

@@ -7,7 +7,7 @@ std::unique_ptr<RRGen> AGen::make(const ComboAddress& ca)
 
 void AGen::toMessage(DNSMessageWriter& dmw)
 {
-  dmw.payload.putUInt32(d_ip);
+  dmw.putUInt32(d_ip);
 }
 
 std::unique_ptr<RRGen> AAAAGen::make(const ComboAddress& ca)
@@ -23,39 +23,39 @@ std::unique_ptr<RRGen> AAAAGen::make(const ComboAddress& ca)
 
 void AAAAGen::toMessage(DNSMessageWriter& dmw)
 {
-  dmw.payload.putBlob(d_ip, 16);
+  dmw.putBlob(d_ip, 16);
 }
 
 void SOAGen::toMessage(DNSMessageWriter& dmw)
 {
-  putName(dmw.payload, d_mname);    putName(dmw.payload, d_rname);
+  dmw.putName(d_mname);    dmw.putName(d_rname);
-  dmw.payload.putUInt32(d_serial);  dmw.payload.putUInt32(d_refresh);
+  dmw.putUInt32(d_serial);  dmw.putUInt32(d_refresh);
-  dmw.payload.putUInt32(d_retry);   dmw.payload.putUInt32(d_expire);
+  dmw.putUInt32(d_retry);   dmw.putUInt32(d_expire);
-  dmw.payload.putUInt32(d_minimum);
+  dmw.putUInt32(d_minimum);
 }
 
 void CNAMEGen::toMessage(DNSMessageWriter& dmw)
 {
-  putName(dmw.payload, d_name);
+  dmw.putName(d_name);
 }
 
 void NSGen::toMessage(DNSMessageWriter& dmw)
 {
-  putName(dmw.payload, d_name);
+  dmw.putName(d_name);
 }
 
 
 void MXGen::toMessage(DNSMessageWriter& dmw) 
 {
-  dmw.payload.putUInt16(d_prio);
+  dmw.putUInt16(d_prio);
-  putName(dmw.payload, d_name);
+  dmw.putName(d_name);
 }
 
 void TXTGen::toMessage(DNSMessageWriter& dmw) 
 {
   // XXX should autosplit
-  dmw.payload.putUInt8(d_txt.length());
+  dmw.putUInt8(d_txt.length());
-  dmw.payload.putBlob(d_txt);
+  dmw.putBlob(d_txt);
 }
 
 void ClockTXTGen::toMessage(DNSMessageWriter& dmw) 
@@ -70,6 +70,6 @@ void ClockTXTGen::toMessage(DNSMessageWriter& dmw)
   else
     txt="Overflow";
   // XXX should autosplit
-  dmw.payload.putUInt8(txt.length());
+  dmw.putUInt8(txt.length());
-  dmw.payload.putBlob(txt);
+  dmw.putBlob(txt);
 }

tdns/dnsmessages.cc

@@ -27,17 +27,17 @@ void DNSMessageReader::getQuestion(dnsname& name, DNSType& type)
 
 void DNSMessageWriter::putRR(DNSSection section, const dnsname& name, DNSType type, uint32_t ttl, const std::unique_ptr<RRGen>& content)
 {
-  auto cursize = payload.payloadpos;
+  auto cursize = payloadpos;
   try {
-    putName(payload, name);
+    putName(name);
-    payload.putUInt16((int)type); payload.putUInt16(1);
+    putUInt16((int)type); putUInt16(1);
-    payload.putUInt32(ttl);
+    putUInt32(ttl);
-    auto pos = payload.putUInt16(0); // placeholder
+    auto pos = putUInt16(0); // placeholder
     content->toMessage(*this);
-    payload.putUInt16At(pos, payload.payloadpos-pos-2);
+    putUInt16At(pos, payloadpos-pos-2);
   }
   catch(...) {
-    payload.payloadpos = cursize;
+    payloadpos = cursize;
     throw;
   }
   switch(section) {
@@ -58,10 +58,10 @@ void DNSMessageWriter::putRR(DNSSection section, const dnsname& name, DNSType ty
 void DNSMessageWriter::setQuestion(const dnsname& name, DNSType type)
 {
   dh.ancount = dh.arcount = dh.nscount = 0;
-  payload.rewind();
+  payloadpos=0;
-  putName(payload, name);
+  putName(name);
-  payload.putUInt16((uint16_t)type);
+  putUInt16((uint16_t)type);
-  payload.putUInt16(1); // class
+  putUInt16(1); // class
 }
 
 string DNSMessageReader::serialize() const
@@ -70,7 +70,9 @@ string DNSMessageReader::serialize() const
 }
 string DNSMessageWriter::serialize() const
 {
-  return string((const char*)this, (const char*)this + sizeof(dnsheader) + payload.payloadpos);
+  std::string ret((const char*)this, (const char*)this + sizeof(dnsheader));
+  ret.append((const unsigned char*)&payload[0], (const unsigned char*)&payload[payloadpos]);
+  return ret;
 }
 
 static_assert(sizeof(DNSMessageReader) == 516, "dnsmessagereader size must be 516");

tdns/dnsmessages.hh

@@ -2,6 +2,7 @@
 #include "dns.hh"
 #include "safearray.hh"
 #include "dns-storage.hh"
+#include <vector>
 
 struct DNSMessageReader
 {
@@ -16,20 +17,63 @@ struct DNSMessageReader
 
 struct DNSMessageWriter
 {
+  explicit DNSMessageWriter(int maxsize=512)
+  {
+    payload.resize(maxsize);
+  }
   struct dnsheader dh=dnsheader{};
-  SafeArray<1500> payload;
+  std::vector<uint8_t> payload;
   void setQuestion(const dnsname& name, DNSType type);
   void putRR(DNSSection section, const dnsname& name, DNSType type, uint32_t ttl, const std::unique_ptr<RRGen>& rr);
   std::string serialize() const;
+
+  uint16_t payloadpos=0;
+  void putUInt8(uint8_t val)
+  {
+    payload.at(payloadpos++)=val;
+  }
+
+  uint16_t putUInt16(uint16_t val)
+  {
+    val = htons(val);
+    memcpy(&payload.at(payloadpos+2)-2, &val, 2);
+    payloadpos+=2;
+    return payloadpos - 2;
+  }
+
+  void putUInt16At(uint16_t pos, uint16_t val)
+  {
+    val = htons(val);
+    memcpy(&payload.at(pos+2)-2, &val, 2);
+  }
+
+  void putUInt32(uint32_t val)
+  {
+    val = htonl(val);
+    memcpy(&payload.at(payloadpos+sizeof(val)) - sizeof(val), &val, sizeof(val));
+    payloadpos += sizeof(val);
+  }
+
+  void putBlob(const std::string& blob)
+  {
+    memcpy(&payload.at(payloadpos+blob.size()) - blob.size(), blob.c_str(), blob.size());
+    payloadpos += blob.size();;
+  }
+
+  void putBlob(const unsigned char* blob, int size)
+  {
+    memcpy(&payload.at(payloadpos+size) - size, blob, size);
+    payloadpos += size;
+  }
+  void putName(const dnsname& name)
+  {
+    for(const auto& l : name) {
+      putUInt8(l.size());
+      putBlob(l.d_s);
+    }
+    putUInt8(0);
+  }
+
+  
 };
 
-inline void putName(SafeArray<1500>& payload, const dnsname& name)
-  {
-  for(const auto& l : name) {
-    if(l.size() > 63)
-      throw std::runtime_error("Can't emit a label larger than 63 characters");
-    payload.putUInt8(l.size());
-    payload.putBlob(l.d_s);
-  }
-  payload.putUInt8(0);
-}

tdns/safearray.hh

@@ -27,46 +27,8 @@ struct SafeArray
     memcpy(&ret, &payload.at(payloadpos+2)-2, 2);
     payloadpos+=2;
     return htons(ret);
-
   }
 
-  void putUInt8(uint8_t val)
-  {
-    payload.at(payloadpos++)=val;
-  }
-
-  uint16_t putUInt16(uint16_t val)
-  {
-    val = htons(val);
-    memcpy(&payload.at(payloadpos+2)-2, &val, 2);
-    payloadpos+=2;
-    return payloadpos - 2;
-  }
-
-  void putUInt16At(uint16_t pos, uint16_t val)
-  {
-    val = htons(val);
-    memcpy(&payload.at(pos+2)-2, &val, 2);
-  }
-
-  void putUInt32(uint32_t val)
-  {
-    val = htonl(val);
-    memcpy(&payload.at(payloadpos+sizeof(val)) - sizeof(val), &val, sizeof(val));
-    payloadpos += sizeof(val);
-  }
-
-  void putBlob(const std::string& blob)
-  {
-    memcpy(&payload.at(payloadpos+blob.size()) - blob.size(), blob.c_str(), blob.size());
-    payloadpos += blob.size();;
-  }
-
-  void putBlob(const unsigned char* blob, int size)
-  {
-    memcpy(&payload.at(payloadpos+size) - size, blob, size);
-    payloadpos += size;
-  }
   
   std::string getBlob(int size)
   {

tdns/tdns.cc

@@ -19,13 +19,12 @@ using namespace std;
 void addAdditional(const DNSNode* bestzone, const dnsname& zone, const vector<dnsname>& toresolve, DNSMessageWriter& response)
 {
   for(auto addname : toresolve ) {
-    cout<<"Doing additional or glue lookup for "<<addname<<endl;
+    cout<<"Doing additional or glue lookup for "<<addname<<" in "<<zone<<endl;
     if(!addname.makeRelative(zone)) {
       cout<<addname<<" is not within our zone, not doing glue"<<endl;
       continue;
     }
     dnsname wuh;
-    cout<<"Looking up glue record "<<addname<<" in zone "<<zone<<endl;
     auto addnode = bestzone->find(addname, wuh);
     if(!addnode || !addname.empty())  {
       cout<<"  Found nothing, continuing"<<endl;
@@ -44,136 +43,144 @@ void addAdditional(const DNSNode* bestzone, const dnsname& zone, const vector<dn
 }
 
 bool processQuestion(const DNSNode& zones, DNSMessageReader& dm, const ComboAddress& local, const ComboAddress& remote, DNSMessageWriter& response)
-try
 {
-  dnsname name;
+  dnsname name, origname;
   DNSType type;
   dm.getQuestion(name, type);
+  origname=name; // we munch on this below
   cout<<"Received a query from "<<remote.toStringWithPort()<<" for "<<name<<" and type "<<type<<endl;
-  
-  response.dh = dm.dh;
-  response.dh.ad = response.dh.ra = response.dh.aa = 0;
-  response.dh.qr = 1;
-  response.setQuestion(name, type);
-  
-  if(type == DNSType::AXFR || type == DNSType::IXFR)  {
-    cout<<"Query was for AXFR or IXFR over UDP, can't do that"<<endl;
-    response.dh.rcode = (int)RCode::Servfail;
-    return true;
-  }
 
-  if(dm.dh.opcode != 0) {
+  try {
-    cout<<"Query had non-zero opcode "<<dm.dh.opcode<<", sending NOTIMP"<<endl;
+    response.dh = dm.dh;
-    response.dh.rcode = (int)RCode::Notimp;
+    response.dh.ad = response.dh.ra = response.dh.aa = 0;
-    return true;
+    response.dh.qr = 1;
-  }
+    response.setQuestion(name, type);
     
-  dnsname zone;
+    if(type == DNSType::AXFR || type == DNSType::IXFR)  {
-  auto fnd = zones.find(name, zone);
+      cout<<"Query was for AXFR or IXFR over UDP, can't do that"<<endl;
-  if(fnd && fnd->zone) {
+      response.dh.rcode = (int)RCode::Servfail;
-    cout<<"---\nBest zone: "<<zone<<", name now "<<name<<", loaded: "<<(void*)fnd->zone<<endl;
+      return true;
-
-    response.dh.aa = 1; 
-    
-    auto bestzone = fnd->zone;
-    dnsname searchname(name), lastnode, zonecutname;
-    const DNSNode* passedZonecut=0;
-    int CNAMELoopCount = 0;
-    
-  loopCNAME:;
-    lastnode.clear();
-    zonecutname.clear();
-    auto node = bestzone->find(searchname, lastnode, &passedZonecut, &zonecutname);
-
-    if(!node) {
-      cout<<"Found nothing in zone '"<<zone<<"' for lhs '"<<name<<"'"<<endl;
     }
-    else if(passedZonecut) {
+
-      response.dh.aa = false;
+    if(dm.dh.opcode != 0) {
-      cout<<"This is a delegation, zonecutname: '"<<zonecutname<<"'"<<endl;
+      cout<<"Query had non-zero opcode "<<dm.dh.opcode<<", sending NOTIMP"<<endl;
-      
+      response.dh.rcode = (int)RCode::Notimp;
-      for(const auto& rr: passedZonecut->rrsets) {
+      return true;
-        cout<<"  Have type "<<rr.first<<endl;
+    }
+    
+    dnsname zone;
+    auto fnd = zones.find(name, zone);
+    if(fnd && fnd->zone) {
+      cout<<"---\nBest zone: "<<zone<<", name now "<<name<<", loaded: "<<(void*)fnd->zone<<endl;
+
+      response.dh.aa = 1; 
+    
+      auto bestzone = fnd->zone;
+      dnsname searchname(name), lastnode, zonecutname;
+      const DNSNode* passedZonecut=0;
+      int CNAMELoopCount = 0;
+    
+    loopCNAME:;
+      auto node = bestzone->find(searchname, lastnode, &passedZonecut, &zonecutname);
+
+      if(!node) {
+        cout<<"Found nothing in zone '"<<zone<<"' for lhs '"<<name<<"'"<<endl;
       }
-      auto iter = passedZonecut->rrsets.find(DNSType::NS);
+      else if(passedZonecut) {
-      if(iter != passedZonecut->rrsets.end()) {
+        response.dh.aa = false;
-        const auto& rrset = iter->second;
+        cout<<"This is a delegation, zonecutname: '"<<zonecutname<<"'"<<endl;
-        vector<dnsname> toresolve;
+      
-        for(const auto& rr : rrset.contents) {
+        for(const auto& rr: passedZonecut->rrsets) {
-          response.putRR(DNSSection::Authority, zonecutname+zone, DNSType::NS, rrset.ttl, rr);
+          cout<<"  Have type "<<rr.first<<endl;
-          toresolve.push_back(dynamic_cast<NSGen*>(rr.get())->d_name);
         }
-
+        auto iter = passedZonecut->rrsets.find(DNSType::NS);
-        addAdditional(bestzone, zone, toresolve, response);
+        if(iter != passedZonecut->rrsets.end()) {
-      }
+          const auto& rrset = iter->second;
-    }
+          vector<dnsname> toresolve;
-    else if(!searchname.empty()) {
-      cout<<"This is an NXDOMAIN situation"<<endl;
-      const auto& rrset = fnd->zone->rrsets[DNSType::SOA];
-      response.dh.rcode = (int)RCode::Nxdomain;
-      response.putRR(DNSSection::Authority, zone, DNSType::SOA, rrset.ttl, rrset.contents[0]);
-    }
-    else {
-      cout<<"Found something in zone '"<<zone<<"' for lhs '"<<name<<"', searchname now '"<<searchname<<"', lastnode '"<<lastnode<<"', passedZonecut="<<passedZonecut<<endl;
-      
-      auto iter = node->rrsets.cbegin();
-      vector<dnsname> additional;
-      if(type == DNSType::ANY) {
-        for(const auto& t : node->rrsets) {
-          const auto& rrset = t.second;
           for(const auto& rr : rrset.contents) {
-            response.putRR(DNSSection::Answer, lastnode+zone, t.first, rrset.ttl, rr);
+            response.putRR(DNSSection::Authority, zonecutname+zone, DNSType::NS, rrset.ttl, rr);
-            if(t.first == DNSType::MX)
+            toresolve.push_back(dynamic_cast<NSGen*>(rr.get())->d_name);
-              additional.push_back(dynamic_cast<MXGen*>(rr.get())->d_name);
-
           }
+          addAdditional(bestzone, zone, toresolve, response);
         }
       }
-      else if(iter = node->rrsets.find(type), iter != node->rrsets.end()) {
+      else if(!searchname.empty()) {
-        const auto& rrset = iter->second;
+        cout<<"This is an NXDOMAIN situation"<<endl;
-        for(const auto& rr : rrset.contents) {
+        const auto& rrset = fnd->zone->rrsets[DNSType::SOA];
-          response.putRR(DNSSection::Answer, lastnode+zone, type, rrset.ttl, rr);
+        response.dh.rcode = (int)RCode::Nxdomain;
-          if(type == DNSType::MX)
+        response.putRR(DNSSection::Authority, zone, DNSType::SOA, rrset.ttl, rrset.contents[0]);
-            additional.push_back(dynamic_cast<MXGen*>(rr.get())->d_name);
-        }
-
-      }
-      else if(iter = node->rrsets.find(DNSType::CNAME), iter != node->rrsets.end()) {
-        cout<<"We do have a CNAME!"<<endl;
-        const auto& rrset = iter->second;
-        dnsname target;
-        for(const auto& rr : rrset.contents) {
-          response.putRR(DNSSection::Answer, lastnode+zone, DNSType::CNAME, rrset.ttl, rr);
-          target=dynamic_cast<CNAMEGen*>(rr.get())->d_name;
-        }
-        if(target.makeRelative(zone)) {
-          cout<<"  Should follow CNAME to "<<target<<" within our zone"<<endl;
-          // XXX we need to change our behaviour on NXDOMAIN I think depending on if you've followed a CNAME
-          searchname = target; 
-          if(CNAMELoopCount++ < 10)  
-            goto loopCNAME;
-        }
-        else
-          cout<<"  CNAME points to record "<<target<<" in other zone, good luck"<<endl;
       }
       else {
-        cout<<"Node exists, qtype doesn't, NOERROR situation, inserting SOA"<<endl;
+        cout<<"Found something in zone '"<<zone<<"' for lhs '"<<name<<"', searchname now '"<<searchname<<"', lastnode '"<<lastnode<<"', passedZonecut="<<passedZonecut<<endl;
-        const auto& rrset = fnd->zone->rrsets[DNSType::SOA];
-        response.putRR(DNSSection::Answer, zone, DNSType::SOA, rrset.ttl, rrset.contents[0]);
-      }
-      addAdditional(bestzone, zone, additional, response);
       
+        auto iter = node->rrsets.cbegin();
+        vector<dnsname> additional;
+        if(type == DNSType::ANY) {
+          for(const auto& t : node->rrsets) {
+            const auto& rrset = t.second;
+            for(const auto& rr : rrset.contents) {
+              response.putRR(DNSSection::Answer, lastnode+zone, t.first, rrset.ttl, rr);
+              if(t.first == DNSType::MX)
+                additional.push_back(dynamic_cast<MXGen*>(rr.get())->d_name);
+
+            }
+          }
+        }
+        else if(iter = node->rrsets.find(type), iter != node->rrsets.end()) {
+          const auto& rrset = iter->second;
+          for(const auto& rr : rrset.contents) {
+            response.putRR(DNSSection::Answer, lastnode+zone, type, rrset.ttl, rr);
+            if(type == DNSType::MX)
+              additional.push_back(dynamic_cast<MXGen*>(rr.get())->d_name);
+          }
+
+        }
+        else if(iter = node->rrsets.find(DNSType::CNAME), iter != node->rrsets.end()) {
+          cout<<"We do have a CNAME!"<<endl;
+          const auto& rrset = iter->second;
+          dnsname target;
+          for(const auto& rr : rrset.contents) {
+            response.putRR(DNSSection::Answer, lastnode+zone, DNSType::CNAME, rrset.ttl, rr);
+            target=dynamic_cast<CNAMEGen*>(rr.get())->d_name;
+          }
+          if(target.makeRelative(zone)) {
+            cout<<"  Should follow CNAME to "<<target<<" within our zone"<<endl;
+            // XXX we need to change our behaviour on NXDOMAIN I think depending on if you've followed a CNAME
+            searchname = target; 
+            if(CNAMELoopCount++ < 10) {
+              lastnode.clear();
+              zonecutname.clear();
+              goto loopCNAME;
+            }
+          }
+          else
+            cout<<"  CNAME points to record "<<target<<" in other zone, good luck"<<endl;
+        }
+        else {
+          cout<<"Node exists, qtype doesn't, NOERROR situation, inserting SOA"<<endl;
+          const auto& rrset = fnd->zone->rrsets[DNSType::SOA];
+          response.putRR(DNSSection::Answer, zone, DNSType::SOA, rrset.ttl, rrset.contents[0]);
+        }
+        addAdditional(bestzone, zone, additional, response);
+      
+      }
     }
+    else {
+      cout<<"No zone matched"<<endl;
+      response.dh.rcode = (uint8_t)RCode::Refused;
+    }
+    return true;
   }
-  else {
+  catch(std::out_of_range& e) { // exceeded packet size
-    cout<<"No zone matched"<<endl;
+    cout<<"Query for '"<<origname<<"'|"<<type<<" got truncated"<<endl;
-    response.dh.rcode = (uint8_t)RCode::Refused;
+    response.setQuestion(origname, type); // this resets the packet
+    response.dh.tc=1; response.dh.aa=0;
+    return true;
+  }
+  catch(std::exception& e) {
+    cout<<"Error processing query: "<<e.what()<<endl;
+    return false;
   }
-  return true;
-}
-catch(std::exception& e) {
-  cout<<"Error processing query: "<<e.what()<<endl;
-  return false;
 }
 
 void udpThread(ComboAddress local, Socket* sock, const DNSNode* zones)
@@ -246,7 +253,7 @@ void tcpClientThread(ComboAddress local, ComboAddress remote, int s, const DNSNo
     dnsname name;
     DNSType type;
     dm.getQuestion(name, type);
-    DNSMessageWriter response;
+    DNSMessageWriter response(std::numeric_limits<uint16_t>::max()-sizeof(dnsheader));
     
     if(type == DNSType::AXFR) {
       cout<<"Should do AXFR for "<<name<<endl;
@@ -281,7 +288,7 @@ void tcpClientThread(ComboAddress local, ComboAddress remote, int s, const DNSNo
               try {
                 response.putRR(DNSSection::Answer, nname, p.first, p.second.ttl, rr);
               }
-              catch(...) { // exceeded packet size
+              catch(std::out_of_range& e) { // exceeded packet size 
                 writeTCPResponse(sock, response);
                 response.setQuestion(zone, type);
                 goto retry;
@@ -311,14 +318,9 @@ void tcpClientThread(ComboAddress local, ComboAddress remote, int s, const DNSNo
   }
 }
 
-
 int main(int argc, char** argv)
 try
 {
-  cout<<sizeof(AGen)<<endl;
-  cout<<sizeof(MXGen)<<endl;
-  cout<<sizeof(RRGen)<<endl;
-
   if(argc != 2) {
     cerr<<"Syntax: tdns ipaddress:port"<<endl;
     return(EXIT_FAILURE);