Welcome to tdns

Introduction

tdns is a simple authoritative nameserver that is fully faithful to the DNS storage model as outlined in RFC 1034.

An introduction can be found on https://powerdns.org/hello-dns/tdns/intro.md.html

Object relations

DNSMessageReader is used to read DNS messages. A UDP DNS Packet is also a DNS message. DNSMessageWriter is used to create DNS messages.

A DNS name is stored in a DNSName object and internally consists of DNSLabel's.

DNS messages also mostly have a query name, which is a DNSName and a query type which is a DNSType. They also have a DNSClass but we don't do much with that.

To insert resource records into DNSMessageWriter, use DNSMessageWriter::putRR, to read them from DNSMessageReader, use DNSMessageReader::getRR.

Resource records are stored as RRGen instances. The RRGen object is able to serialize itself to/from a DNSMessageWriter or DNSMessageReader. In addition, this object has a RRGen::toString method for 'human consumption' output.

Next steps in understanding tdns

The basics of tdns can best be understood by first reading tdig.cc

Details of how DNSMessageReader/DNSMessageWriter and the RRGen objects interact are in record-types.hh

DNS Tree

Key to understanding tdns (or in fact, dns) is understanding the DNS Tree, which is hosted by the DNSNode class, for which see dns-storage.hh