dnsreplay had odd race conditions in sending/reseinding packets

We had logic to pre-read the first packet for better error reporting, and then not read it at the top of the while loop,
but process the pre-read packet. However, this logic kept engaging, causing us to retransmit the previous packet a lot, depending
on the size of our retransmit window, which in turn depended on the receiver characteristic. Horrible.
dnsreplay may previously have overstated the number of duplicate packets because of this.

diff --git a/pdns/dnsreplay.cc b/pdns/dnsreplay.cc
index 4a358a4b78bab37e96d6b7e02f14b7518d5e04fe..9e81356170103a9c5dd772e46ec31b4c989b28a1 100644 (file)
--- a/pdns/dnsreplay.cc
+++ b/pdns/dnsreplay.cc
@@ -549,6 +549,7 @@ bool sendPacketFromPR(PcapPacketReader& pr, const ComboAddress& remote)
   try {
     // yes, we send out ALWAYS. Even if we don't do anything with it later, 
     if(!dh->qr) { // this is to stress out the reference server with all the pain
+      s_questions++;
       qd.d_assignedID = s_idmanager.getID();
       uint16_t tmp=dh->id;
       dh->id=htons(qd.d_assignedID);
@@ -560,7 +561,7 @@ bool sendPacketFromPR(PcapPacketReader& pr, const ComboAddress& remote)
     QuestionIdentifier qi=QuestionIdentifier::create(pr.getSource(), pr.getDest(), mdp);
 
     if(!mdp.d_header.qr) {
-      s_questions++;
+
       if(qids.count(qi)) {
         if(!g_quiet)
           cout<<"Saw an exact duplicate question in PCAP "<<qi<< endl;
@@ -608,8 +609,7 @@ bool sendPacketFromPR(PcapPacketReader& pr, const ComboAddress& remote)
   catch(std::out_of_range &e)
   {
     s_idmanager.releaseID(qd.d_assignedID);  // not added to qids for cleanup
-    s_origdnserrors++;
-    
+    s_origdnserrors++;    
   }
 
   return sent;
@@ -687,7 +687,7 @@ try
   if(!pr.getUDPPacket()) // we do this here so we error out more cleanly on no packets
     return 0;
   unsigned int count=0;
-
+  bool first = true;
   for(;;) {
     if(g_pleaseQuit) {
       cerr<<"Interrupted from terminal"<<endl;
@@ -699,7 +699,7 @@ try
     struct timeval packet_ts;
     packet_ts.tv_sec = 0; 
     packet_ts.tv_usec = 0; 
-    bool first = true;
+
     while(packet_ts < mental_time) {
       if(!first && !pr.getUDPPacket()) // otherwise we miss the first packet
         goto out;