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GODNS

A simple and fast DNS cache server written in Go.

Similar to dnsmasq, but supports some difference features:

  • Keep hosts records in Redis and the local file /etc/hosts

  • Auto-Reloads when hosts configuration is changed. (Yes, dnsmasq needs to be reloaded)

Local Deployment

Start GoDNS:

docker-compose up

You may see the error:

Error starting userland proxy: listen udp 0.0.0.0:5321: bind: address already in use

It means there is another process on your server listening on the UDP port 5321. You can list the process listening on this port with:

sudo netstat -tulpn | grep 5321

DNS query to GoDNS:

dig @172.17.0.1 -p 5321 www.github.com

Use GoDNS

	$ sudo vi /etc/resolv.conf
	nameserver #the ip of godns running

Configuration

All the configuration in godns.conf is a TOML format config file.

resolv.conf

Upstream server can be configured by changing file from somewhere other than "/etc/resolv.conf"

[resolv]
resolv-file = "/etc/resolv.conf"

If multiple namerservers are set in resolv.conf, the upsteam server will try in a top to bottom order

server-list-file

Domain-specific nameservers configuration, formatting keep compatible with Dnsmasq.

server=/google.com/8.8.8.8

More cases please refererence dnsmasq-china-list

cache

Only the local memory storage backend is currently implemented. The redis backend is in the todo list

[cache]
backend = "memory"
expire = 600  # default expire time 10 minutes
maxcount = 100000

hosts

Force resolve domain to assigned ip, support two types hosts configuration:

  • locale hosts file
  • remote redis hosts

hosts file

can be assigned at godns.conf,default : /etc/hosts

[hosts]
host-file = "/etc/hosts"

Hosts file format is described in linux man pages. More than that , *. wildcard is supported additional.

redis hosts

This is a special requirment in our system. Must maintain a global hosts configuration, and support update the host records from other remote server. Therefore, while "redis-hosts" be enabled, will query the redis db when each dns request is reached.

The hosts record is organized with redis hash map. and the key of the map is configured.

[hosts]
redis-key = "godns:hosts"

Insert hosts records into redis

redis > hset godns:hosts www.test.com 1.1.1.1

Compared with file-backend records, redis-backend hosts support multiple A entries.

redis > hset godns:hosts www.test.com 1.1.1.1,2.2.2.2

Zone configuration

Specific configuration if you want your godns instance to only respond to one DNS Zone

zone = 'example.test.'
zone-ns = "ns-cloud-b1.googledomains.com."
zone-mbox = "cloud-dns-hostmaster.google.com."
zone-serial = 1
zone-refresh = 21600
zone-retry = 3600
zone-expire = 259200
zone-negcache-ttl = 30
zone-soa-ttl = 3600

If zone is set, all the other parameters should be set. These parameters are used when one domain is not found in the hosts (file or redis), we return a "NODATA" dns response. According to the RFC, it should contain the SOA entry in order to be cached correctly by other DNS servers.

If another domain than zone is queried, GoDNS will respond with rcode REFUSED since only the specified zone will be responded to.

Benchmark

Debug close

$ go test -bench=.

testing: warning: no tests to run
PASS
BenchmarkDig-8     50000             57945 ns/op
ok      _/usr/home/keqiang/godns        3.259s

The result : 15342 queries/per second

The test environment:

CentOS release 6.4

  • CPU: Intel Xeon 2.40GHZ 4 cores

  • MEM: 46G

Web console

Joke: A web console for godns

https://github.com/kenshinx/joke

screenshot

joke

Deployment

Deployment in productive supervisord highly recommended.


[program:godns]
command=/usr/local/bin/godns -c /etc/godns.conf
autostart=true
autorestart=true
user=root
stdout_logfile_maxbytes = 50MB
stdoiut_logfile_backups = 20
stdout_logfile = /var/log/godns.log

TODO

  • The redis cache backend
  • Update ttl

LICENSE

godns is under the MIT license. See the LICENSE file for details.