lresolver

lresolver is a simple local DNS resolver. It try to solve a very specific problem when you need to deal with more than one internal DNS server.

Some features:

• Load balancing using round-robin
• Try to resolve on all servers (in parallel, if not found on first attempt)
• No limit on the number of DNS servers
• In-memory cache

Credits

This projects uses the great DNS library miekg/dns by Miek Gieben. The first version of this code was based on StalkR/dns-reverse-proxy.

Install & Config

Download the static binary here: lresolver/releases.

To complie from sources (you need Go installed):

go get github.com/lucindo/lresolver

Configuration

The supported formats for configuration are: YAML, JSON, TOML and HCL. On starting up lresolver will try to find the file lresolver.{yml,yaml,json,toml,hcl} in /etc/lresolver/ or in the current directory. You can also specify the configuration file with the -config flag.

Configuration directives:

Directive	Required	Default	Description
bind	Yes	-	Address to bind the server, e.g 127.0.0.1
nameservers	Yes	-	List of DNS servers
cache	No	true	Turn on/off internal caching
negative_cache	No	true	Cache non-NOERROR responses
max_cache_ttl	No	300	Internal cache TTL in seconds
tcp	No	true	Listen to TCP as well

Sample Configuration:

bind: 127.0.0.1
cache: true
negative_cache: true
max_cache_ttl: 300
tcp: true
nameservers:
- 8.8.8.8
- 8.8.4.4

Running

Point /etc/resolv.conf to 127.0.0.1:

# /etc/resolv.conf
nameserver 127.0.0.1

You can leave your other resolv.conf directives (search, domain, etc) unchanged.

In my production systems I put the lresolver.yml in /etc/lresolver/ directory and run the server this way:

/sbin/lresolver -log_dir /var/log/lresolver/

You can clear the cache by sending an USR1 signal to the running server.

To Do

• Update expired entries in background
• Packages for popular Linux distros (deb and rpm)
• Statistics on requests and nameservers
• Option to replace round-robin to dynamic weighted round-robin based on server's response time
• External configuration on etcd
• Suffix-based request routing
• Automatic configuration reload

Contributing

1. Fork it
2. Create your feature branch: git checkout -b my-awesome-new-feature
3. Commit your changes: git commit -m 'Add some awesome feature'
4. Push to the branch: git push origin my-awesome-new-feature
5. Submit a pull request