Erlang DNS Server
View SourceServe DNS authoritative responses... with Erlang.
Requirements
Erlang/OTP 27+
Building
To build:
make
To start fresh:
make fresh
make
Zones
Zones are loaded from JSON. Example JSON files are in the priv/
directory.
You can also write new systems to load zones by writing the zones directly to the zone cache using erldns_zone_cache:put_zone/1
.
Configuration
An example configuration file can be found in erldns.example.config
. Copy it to erldns.config
and modify as needed.
Running
Launch directly
overmind start
To get an interactive Erlang REPL
./rebar3 shell
Build a distribution with and run the release
./rebar3 release
./_build/default/rel/erldns/bin/erldns foreground
Querying
Here are some queries to try:
dig -p 8053 @127.0.0.1 example.com a
dig -p 8053 @127.0.0.1 example.com cname
dig -p 8053 @127.0.0.1 example.com ns
dig -p 8053 @127.0.0.1 example.com mx
dig -p 8053 @127.0.0.1 example.com spf
dig -p 8053 @127.0.0.1 example.com txt
dig -p 8053 @127.0.0.1 example.com sshfp
dig -p 8053 @127.0.0.1 example.com soa
dig -p 8053 @127.0.0.1 example.com naptr
dig -p 8053 @127.0.0.1 -x 127.0.0.1 ptr
Performance
In our environment (DNSimple) we are seeing 30 to 65 µs handoff times to retrieve a packet from the UDP port and give it to a worker for processing. Your performance may vary, but given those measurements erl-dns is capable of handling between 15k and 30k questions per second. Please note: You may need to configure the number of workers available to handle traffic at higher volumes.
If you want to perform some benchmarks, see BENCHMARKING.md
.
Design
The erldns_resolver
module will attempt to find zone data in the zone cache. If you're embedding erl-dns in your application the easiest thing to do is to load the zone cache once the zone cache gen_server
starts push an updated zone into the cache each time data changes.
To insert a zone, use erldns_zone_cache:put_zone({Name, Records})
where Name is a binary term such as <<"example.com">> and Records is a list of dns_rr
records (whose definitions can be found in deps/dns/include/dns_records.hrl
). The name of each record must be the fully qualified domain name (including the zone part).
Here's an example:
erldns_zone_cache:put_zone({
<<"example.com">>, [
#dns_rr{
name = <<"example.com">>,
type = ?DNS_TYPE_A,
ttl = 3600,
data = #dns_rrdata_a{ip = {1,2,3,4}}
},
#dns_rr{
name = <<"www.example.com">>,
type = ?DNS_TYPE_CNAME,
ttl = 3600,
data = #dns_rrdata_cname{dname = <<"example.com">>}
}
]}).
AXFR Support
AXFR zone transfers are not currently implemented. The current "implementation" is just a stub.
Instrumentation
Telemetry is used to instrument the code.
Admin
There is an administrative API for querying the current zone cache and for basic control.
You can read more about it at erldns_admin
.
Tests
To run automated tests:
make test