From f9f2ae96111b91e458a7be7a9f03cbdf9b3ad711 Mon Sep 17 00:00:00 2001
From: Bert Hubert <bert.hubert@netherlabs.nl>
Date: Tue, 3 Jun 2008 21:21:55 +0000
Subject: [PATCH] fix for the 'self-renewing NS record' as spotted by Darren
 Gamble

git-svn-id: svn://svn.powerdns.com/pdns/trunk/pdns@1182 d19b8d6e-7fed-0310-83ef-9ca221ded41b
---
 pdns/recursor_cache.cc | 30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/pdns/recursor_cache.cc b/pdns/recursor_cache.cc
index b91b4e266..815f85c9d 100644
--- a/pdns/recursor_cache.cc
+++ b/pdns/recursor_cache.cc
@@ -228,6 +228,34 @@ int MemRecursorCache::get(time_t now, const string &qname, const QType& qt, set<
   return -1;
 }
  
+bool MemRecursorCache::attemptToRefreshNSTTL(const QType& qt, const set<DNSResourceRecord>& content, const CacheEntry& stored)
+{
+  if(!stored.d_auth) {
+//    cerr<<"feel free to scribble non-auth data!"<<endl;
+    return false;
+  }
+
+  if(qt.getCode()!=QType::NS) {
+  //  cerr<<"Not NS record"<<endl;
+    return false;
+  }
+  if(content.size()!=stored.d_records.size()) {
+  //  cerr<<"Not equal number of records"<<endl;
+    return false;
+  }
+  if(stored.d_records.empty())
+    return false;
+
+  if(stored.d_records.begin()->d_ttd > content.begin()->ttl) {
+    // cerr<<"attempt to LOWER TTL - fine by us"<<endl;
+    return false;
+  }
+
+
+ // cerr<<"Returning true - update attempt!\n";
+  return true;
+}
+
 /* the code below is rather tricky - it basically replaces the stuff cached for qname by content, but it is special
    cased for when inserting identical records with only differing ttls, in which case the entry is not
    touched, but only given a new ttd */
@@ -253,7 +281,7 @@ void MemRecursorCache::replace(time_t now, const string &qname, const QType& qt,
   if(qt.getCode()==QType::SOA || qt.getCode()==QType::CNAME)  // you can only have one (1) each of these
     ce.d_records.clear();
 
-  if(auth /* && !ce.d_auth */ ) {
+  if(auth && !attemptToRefreshNSTTL(qt, content, ce) ) {
     ce.d_records.clear(); // clear non-auth data
     ce.d_auth = true;
     isNew=true;           // data should be sorted again
-- 
2.40.0