[dnsdist] packetcache::get make skipAging configurable

[opeter]

• Program: dnsdist
• Issue type:Feature request

Short description

Behavior of dnsdist in front of an auth dns with cache pool enabled is wrong as it counts down the cached TTL.

Usecase

Put dnsdist in front of an auth dns and activate a cache pool.

Description

We want to put dnsdist in front of our auth nameserver and also use it's cache functionality.
Current behavior caches the records from the auth nameserver but counts down the TTL like a resolver.
From an authoritative point of view this is incorrect so it would be nice to have a feature flag to disable aging of the records.

Quick & Dirty patch:

diff --git a/pdns/dnsdist-cache.cc b/pdns/dnsdist-cache.cc
index 9b5b48c..9f5abd0 100644
--- a/pdns/dnsdist-cache.cc
+++ b/pdns/dnsdist-cache.cc
@@ -209,9 +209,9 @@ bool DNSDistPacketCache::get(const DNSQuestion& dq, uint16_t consumed, uint16_t
     }
   }
 
-  if (!skipAging) {
-    ageDNSPacket(response, *responseLen, age);
-  }
+  //if (!skipAging) {
+  //  ageDNSPacket(response, *responseLen, age);
+  //}
 
   d_hits++;
   return true;

[rgacogne]

We should probably make that an optional parameter to newPacketCache(), although we could also easily make it configurable per query.