From fba6769fcd649dd7ca82db0456162d563c3dd8b2 Mon Sep 17 00:00:00 2001
From: Kees Monshouwer <mind04@monshouwer.org>
Date: Thu, 29 Oct 2015 15:02:15 +0100
Subject: [PATCH] remove 'reverse backend' from core. the logic in this class
 was backend specific and doe not belong here.

---
 pdns/dnsbackend.cc | 146 ---------------------------------------------
 pdns/dnsbackend.hh |  31 ----------
 2 files changed, 177 deletions(-)

diff --git a/pdns/dnsbackend.cc b/pdns/dnsbackend.cc
index fa4f270bf..3e96807a0 100644
--- a/pdns/dnsbackend.cc
+++ b/pdns/dnsbackend.cc
@@ -332,152 +332,6 @@ bool DNSBackend::calculateSOASerial(const DNSName& domain, const SOAData& sd, ti
     return true;
 }
 
-/* This is a subclass of DNSBackend that, assuming you have your zones reversed
- * and stored in an ordered fashion, will be able to look up SOA's much quicker
- * than the DNSBackend code. The normal case for a SOA that exists is 1 backend
- * query no matter how much the depth (although if there are sub-SOA's then
- * this could require one or two more queries). The normal case for an SOA that
- * does not exist is 2 or 3 queries depending on the system, although this will
- * be reduced if the negative cache is active.
- *
- * The subclass MUST implement bool getAuthZone(string &reversed_zone_name)
- * which, given a reversed zone name will return false if there was some sort
- * of error (eg no record found as top of database was hit, lookup issues),
- * otherwise returns true and sets reversed_zone_name to be the exact entry
- * found, otherwise the entry directly preceding where it would be.
- *
- * The subclass MUST implement getAuthData( const string &rev_zone_name, SOAData *soa )
- * which is basically the same as getSOA() but is called with the reversed zone name
- */
-enum {
-    GET_AUTH_NEG_DONTCACHE, // not found but don't cache this fact
-    GET_AUTH_NEG_CACHE,     // not found and negcache this
-    GET_AUTH_SUCCESS,       // entry found
-};
-
-#undef PC
-extern PacketCache PC;
-
-#if 0
-#undef DLOG
-#define DLOG(x) x
-#endif
-
-// XXX DNSName pain, should be DNSName native. 
-static bool add_to_negcache( const string &zone ) {
-    static int negqueryttl=::arg().asNum("negquery-cache-ttl");
-    // add the zone to the negative query cache and return false
-    if(negqueryttl) {
-        DLOG(L<<Logger::Error<<"Adding to neg qcache: " << zone<<endl);
-        PC.insert(DNSName(zone), QType(QType::SOA), PacketCache::QUERYCACHE, "", negqueryttl, 0);
-    }
-    return false;
-}
-
-// XXX DNSName Pain, this should be DNSName native!                     vvvvvvvvvvvvvv
-inline int DNSReversedBackend::_getAuth(DNSPacket *p, SOAData *soa, const string &inZone, const string &querykey, const int best_match_len) {
-    static int negqueryttl=::arg().asNum("negquery-cache-ttl");
-
-    DLOG(L<<Logger::Error<<"SOA Query: " <<querykey<<endl);
-
-    /* Got a match from a previous backend that was longer than this - no need
-     * to continue. This is something of an optimization as we would hit the
-     * similar test below in any cases that this was hit, although we would run
-     * the risk of something being added to the neg-querycache that may
-     * interfear with future queries
-     */
-    if( best_match_len >= (int)querykey.length() ) {
-        DLOG(L<<Logger::Error<<"Best match was better from a different client"<<endl);
-        return GET_AUTH_NEG_DONTCACHE;
-    }
-
-    /* Look up in the negative querycache to see if we have already tried and
-     * failed to look up this zone */
-    if( negqueryttl ) {
-        string content;
-        bool ret = PC.getEntry( DNSName(inZone), QType(QType::SOA), PacketCache::QUERYCACHE, content, 0 );
-        if( ret && content.empty() ) {
-            DLOG(L<<Logger::Error<<"Found in neg qcache: " << inZone << ":" << content << ":" << ret << ":"<<endl);
-            return GET_AUTH_NEG_DONTCACHE;
-        }
-    }
-
-    /* Find the SOA entry on- or before- the position that we want in the b-tree */
-    string foundkey = querykey;
-    if( !getAuthZone( foundkey ) )
-        return GET_AUTH_NEG_CACHE;
-
-    DLOG(L<<Logger::Error<<"Queried: " << querykey << " and found record: " <<foundkey<<endl);
-
-    // Got a match from a previous backend that was longer than this - no need
-    // to continue.
-    if( best_match_len && best_match_len >= (int) foundkey.length() ) {
-        DLOG(L<<Logger::Error<<"Best match was better from a different client"<<endl);
-        return GET_AUTH_NEG_DONTCACHE;
-    }
-
-    // Found record successfully now, fill in the data.
-    if( getAuthData( *soa, p ) ) {
-        /* all the keys are reversed. rather than reversing them again it is
-         * presumably quicker to just substring the zone down to size */
-      soa->qname = DNSName(inZone.substr( inZone.length() - foundkey.length(), string::npos ));
-
-      DLOG(L<<Logger::Error<<"Successfully got record: " <<foundkey << " : " << querykey.substr( 0, foundkey.length() ) << " : " << soa->qname<<endl);
-
-      return GET_AUTH_SUCCESS;
-    }
-
-    return GET_AUTH_NEG_CACHE;
-}
-
-bool DNSReversedBackend::getAuth(DNSPacket *p, SOAData *soa, const DNSName &inZone, const int best_match_len) {
-    // Reverse the lowercased query string
-    string zone = toLower(inZone.toStringNoDot());
-    string querykey = labelReverse(zone);
-
-    int ret = _getAuth( p, soa, inZone.toStringNoDot(), querykey, best_match_len );
-
-    /* If this is disabled then we would just cache the tree structure not the
-     * leaves which should give the best performance and a nice small negcache
-     * size
-     */
-    if( ret == GET_AUTH_NEG_CACHE )
-      add_to_negcache( inZone.toStringNoDot() );
-
-    return ret == GET_AUTH_SUCCESS;
-}
-
-/* getAuthData() is very similar to getSOA() so implement a default getSOA
- * based on that. This will only be called very occasionally for example during
- * an AXFR */
-bool DNSReversedBackend::_getSOA(const string &querykey, SOAData &soa, DNSPacket *p)
-{
-    string searchkey( querykey );
-
-    if( !getAuthZone( searchkey ) )
-        return false;
-
-    DLOG(L<<Logger::Error<<"search key " << searchkey << " query key " << querykey<<endl);
-
-    if( querykey.compare( searchkey ) != 0 )
-        return false;
-
-    return getAuthData( soa, p );
-}
-
-bool DNSReversedBackend::getSOA(const DNSName &inZone, SOAData &soa, DNSPacket *p)
-{
-    // prepare the query string
-    string zone = toLower( inZone.toStringNoDot() );
-    string querykey = labelReverse( zone );
-
-    if( !_getSOA( querykey, soa, p ) )
-        return false;
-
-    soa.qname = inZone;
-    return true;
-}
-
 void fillSOAData(const string &content, SOAData &data)
 {
   // content consists of fields separated by spaces:
diff --git a/pdns/dnsbackend.hh b/pdns/dnsbackend.hh
index fb9cf4792..5bc2fc11d 100644
--- a/pdns/dnsbackend.hh
+++ b/pdns/dnsbackend.hh
@@ -393,37 +393,6 @@ private:
   string d_prefix;
 };
 
-class DNSReversedBackend : public DNSBackend {
-    public:
-        /* Given rev_zone (the reversed name of the zone we are looking for the
-         * SOA record for), return the equivalent of
-         *     SELECT name
-         *     FROM soa_records
-         *     WHERE name <= rev_zone
-         *     ORDER BY name DESC
-         *
-         * ie we want either an exact hit on the record, or the immediately
-         * preceding record when sorted lexographically.
-         *
-         * Return true if something has been found, false if not
-         */
-        virtual bool getAuthZone( string &rev_zone ) { return false; };  // Must be overridden
-
-        /* Once the record has been found, this will be called to get the data
-         * associated with the record so the backend can set up soa.
-         * soa->qname does not need to be set. Return false if
-         * there is a problem getting the data.
-         * */
-        virtual bool getAuthData( SOAData &soa, DNSPacket *p=0) { return false; };  // Must be overridden
-
-        virtual bool getAuth(DNSPacket *p, SOAData *soa, const DNSName &inZone, const int best_match_len) override;
-        inline int _getAuth(DNSPacket *p, SOAData *soa, const string &inZone, const string &querykey, const int best_match_len);
-
-        /* Only called for stuff like signing or AXFR transfers */
-        bool _getSOA(const string &rev_zone, SOAData &soa, DNSPacket *p);
-        virtual bool getSOA(const DNSName &inZone, SOAData &soa, DNSPacket *p) override;
-};
-
 class BackendFactory
 {
 public:
-- 
2.40.0