Handlers

atomdns links handlers together, each handler performs a single task. Together these make up the functionality of the DNS server. This kind of architecture is called server middleware. atomdns’ configuration mostly exists out of picking what handlers you want to run. The order of the handlers in the configuration file determines that order in which they are called in the server.

Each handler has its own documentation in the README.md.

There are several types of handlers:

• handlers that return a response, i.e. dbhost in one.
• handlers that observe, and hand the DNS message over to the next handler, metrics for instance.
• handlers that change the in-transit message and call the next handler. Currently these are not implemented.
• hanlders that add data to the context, geoip adds geographical data to it. This allows handlers up-to-chain to make use of that data, acl uses this data.

• acl

  acl - enforces access control policies
• any

  any - give a minimal response to ANY queries
• as112

  as112 - an AS112 black hole server
• chaos

  chaos - respond to TXT queries in the CH class
• cookie

  cookie - adds an DNS cookie of this server to each reply
• dbfile

  dbfile - serve zone data from an RFC 1035-style file
• dbhost

  dbhosts - serve data from /etc/hosts
• dbsqlite

  dbsqilte - serve zone data from a SQLite database
• drunk

  drunk - test client behavior
• geoip

  geoip - add geographical location data
• log

  log - log queries
• metrics

  metrics - enable prometheus metrics
• msgcache

  msgcache - cache DNS messages
• nsid

  nsid - adds an identifier of this server to each reply
• refuse

  refuse - refuse queries
• sign

  sign - add DNSSEC records to zone files
• template

  template - use Go templates to reply
• unpack

  unpack - unpack the initial query
• url

  url - serve zone data from an URL
• whoami

  whoami - return your resolver’s local IP address, port and transport
• yes

  yes - always respond to positively to queries