[Pdns-users] Re: TCP Queries always go to the recursor?

[Augie Schwer]

On 12/13/06, Augie Schwer <augie.schwer at gmail.com> wrote:
> Is there a reason why TCP queries are always getting sent to the
> recursor (if available) for answers instead of checking for an
> authoritative answer first and then recursing if no authoritative
> answer was found?

I submitted a ticket for this:

http://wiki.powerdns.com/cgi-bin/trac.fcgi/ticket/118

The patch should look something like this; doing a packet cache and
backend check before passing along for recursion, but this is pretty
rudimentary and probably not totally correct:

[augie at augnix pdns]$ svn diff tcpreceiver.cc
Index: tcpreceiver.cc
===================================================================
--- tcpreceiver.cc      (revision 935)
+++ tcpreceiver.cc      (working copy)
@@ -169,32 +169,6 @@
        continue;
       }

-
-      if(packet->d.rd && arg().mustDo("recursor")) {
-       // now what
-       // this is a pretty rare event all in all, so we can afford to be slow
-
-       // this code SHOULD attempt to answer from the local cache first!
-       S.inc("recursing-questions");
-       Resolver res;
-       unsigned int len;
-        DLOG(L<<"About to hand query to recursor"<<endl);
-       ServiceTuple st;
-       st.port=53;
-       parseService(arg()["recursor"],st);
-
-       char *buffer=res.sendReceive(st.host,st.port,packet->getRaw(),packet->len,&len);
-        DLOG(L<<"got an answer from recursor: "<<len<<" bytes,
"<<(int)buffer<<endl);
-       if(buffer) {
-         sendData(buffer,len,fd);
-         DLOG(L<<"sent out to customer: "<<len<<" bytes"<<endl);
-         delete buffer;
-         S.inc("recursing-answers");
-         S.inc("tcp-answers");
-       }
-       continue;
-      }
-
       DNSPacket* cached=new DNSPacket;
       if(!packet->d.rd && (PC.get(packet, cached))) { // short
circuit - does the PacketCache recognize this question?
        cached->setRemote(&packet->remote);
@@ -217,15 +191,41 @@
        }
        reply=s_P->question(packet); // we really need to ask the backend :-)
       }
-
-      delete packet;
-      packet = NULL;

-      if(!reply)  // unable to write an answer?
+      if(!reply){  // unable to write an answer?
+       delete packet;
+       packet = NULL;
        break;
+      }

       S.inc("tcp-answers");
       sendDelPacket(reply, fd);
+
+      if(packet->d.rd && arg().mustDo("recursor")) {
+       // now what
+       // this is a pretty rare event all in all, so we can afford to be slow
+
+       // this code SHOULD attempt to answer from the local cache first!
+       S.inc("recursing-questions");
+       Resolver res;
+       unsigned int len;
+        DLOG(L<<"About to hand query to recursor"<<endl);
+       ServiceTuple st;
+       st.port=53;
+       parseService(arg()["recursor"],st);
+
+       char *buffer=res.sendReceive(st.host,st.port,packet->getRaw(),packet->len,&len);
+        DLOG(L<<"got an answer from recursor: "<<len<<" bytes,
"<<(int)buffer<<endl);
+        delete packet;
+       if(buffer) {
+         sendData(buffer,len,fd);
+         DLOG(L<<"sent out to customer: "<<len<<" bytes"<<endl);
+         delete buffer;
+         S.inc("recursing-answers");
+         S.inc("tcp-answers");
+       }
+       continue;
+      }
     }

   out:



-- 
Augie Schwer    -    Augie at Schwer.us    -    http://schwer.us
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