Knot Resolver is a caching full resolver implementation written in C and LuaJIT, both a resolver library and a daemon. The core architecture is tiny and efficient, and provides a foundation and a state-machine like API for extensions. There are three modules built-in - iterator, validator, cache, and a few more are loaded by default. Most of the rich features are written in Lua(JIT) and C. Batteries are included, but optional.
The LuaJIT modules, support DNS privacy and DNSSEC, and persistent cache with low memory footprint make it a great personal DNS resolver or a research tool to tap into DNS data. TL;DR it's the OpenResty of DNS.
Strong filtering rules, and auto-configuration with etcd make it a great large-scale resolver solution.
The server adopts a different scaling strategy than the rest of the DNS recursors - no threading, shared-nothing architecture (except MVCC cache that may be shared) that allows you to pin instances on available CPU cores and grow by self-replication. You can start and stop additional nodes depending on the contention without downtime.
It also has strong support for DNS over TCP, notably TCP Fast-Open, query pipelining and deduplication, and response reordering.
Knot Resolver is also available from the following distributions' repositories.
Building from sources
This is simple and doesn't require any dependencies or system modifications, just run:
$ docker run -Pit cznic/knot-resolver
The images are meant as an easy way to try knot-resolver, and they're not designed for production use.
The project builds a resolver library in the
lib directory, and a daemon in the
daemon directory. It requires no configuration or parameters to run a server on localhost.
See the documentation at knot-resolver.readthedocs.io for more options.