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https://github.com/jamesits/snd
Minimal authoritative PTR (rDNS, reverse DNS) resolver with automatic generation of records.
https://github.com/jamesits/snd
Last synced: 16 days ago
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Minimal authoritative PTR (rDNS, reverse DNS) resolver with automatic generation of records.
- Host: GitHub
- URL: https://github.com/jamesits/snd
- Owner: Jamesits
- License: mit
- Created: 2019-12-07T16:59:48.000Z (almost 5 years ago)
- Default Branch: master
- Last Pushed: 2024-04-19T13:25:21.000Z (7 months ago)
- Last Synced: 2024-10-16T13:37:28.138Z (28 days ago)
- Language: Go
- Homepage:
- Size: 95.7 KB
- Stars: 20
- Watchers: 3
- Forks: 8
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# SND
Minimal authoritative PTR (rDNS, reverse DNS) resolver with automatic generation of records.
[](https://dev.azure.com/nekomimiswitch/General/_build/latest?definitionId=71&branchName=master)
[](https://microbadger.com/images/jamesits/snd "Get your own image badge on microbadger.com")
## Motivation
Say you have a large collection of IP addresses (thousands of IPv4 /24 blocks, or one IPv6 /32 block), and you want to have PTR records on all of your IPs. Writing a zonefile and hosting it using any traditional authoritative DNS server is unrealistic: the zonefile will be of multiple GBs and you need an enormous amount of memory to even load it.
SND provides you a simple alternative option: you name a base domain, and SND generates PTR records for you on the fly based on a set of pre-defined rules.
```
1.1.168.192.in-addr.arpa. 1000 IN PTR 192.168.1.1.ptr.example.com.
1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.0.0.0.d.f.ip6.arpa. 1000 IN PTR fd00.1.0.0.0.0.0.1.ptr.example.com.
```
## Requirements
### Hardware
SND can run on very little processing power (Raspberry Pis are fine) and a very small memory footprint (a few MBs) although the performance will be not optimal.
As of version 0.1.2, on a 4-core Intel E5-2670 VM with more than 2GiB memory, SND can process around 25K RPS.
### Software
Officially supported OS:
* Linux (kernel 4.19+ with glibc)
* Windows (Windows Server 2016 or later, Windows 10 Desktop 1809 or later)
Other OSes are not currently tested because of the lack of resources available to me.
## Usage
### Configure SND
Copy over the self-documented [example config](contrib/config/config.toml) and tweak it for your own need. Please do not
leave any `example.com` things in your own config. Remove what you don't need.
Currently no strict config file format checking is implemented -- you might crash the program if some important keys are
missing.
### Set up SND
In most cases you are going to need 2 servers (or one server with 2 different IP addresses if you don't care about availability issues). Copy the exact same config file to both servers and launch SND on both of them:
Download the pre-compiled binary from [releases](https://github.com/Jamesits/SND/releases) to your server and run it:
```shell
chmod +x ./snd
./snd -config path/to/config.toml
```
Or, if you prefer Docker:
```shell
docker run --rm -p 53:53 -p 53:53/udp -v path/to/config.toml:/etc/snd/config.toml:ro snd:latest
```
Run a simple test using dig:
```shell
$ dig @localhost -x 192.0.2.1
; <<>> DiG 9.11.5-P4-5.1-Debian <<>> @localhost -x 192.0.2.1
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 50924
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; WARNING: recursion requested but not available
;; QUESTION SECTION:
;1.2.0.192.in-addr.arpa. IN PTR
;; ANSWER SECTION:
1.2.0.192.in-addr.arpa. 3600 IN PTR 192.0.2.1.example.com.
```
### Set up DNS records
You need at least 2 `A` or `AAAA` records pointing to each of your SND servers. You might need to set them up as glue records based on your actual config.
```
ns1.example.com. 3600 IN A 192.0.2.1
ns2.example.com. 3600 IN A 192.0.2.2
```
### Set up PTR record delegation
Set up a `domain` object at your RIR like this.
```
domain:
descr:
admin-c:
tech-c:
zone-c:
nserver: ns1.example.com
nserver: ns2.example.com
mnt-by:
```
Detailed instructions are provided per RIR:
* [AfriNIC](https://afrinic.net/support/requesting-reverse-delegation)
* [ARIN](https://www.arin.net/resources/manage/reverse/)
* [APNIC](https://www.apnic.net/manage-ip/manage-resources/reverse-dns/)
* [LACNIC](https://www.lacnic.net/685/2/lacnic/5-delegation-of-reverse-resolution)
* [RIPE NCC](https://www.ripe.net/manage-ips-and-asns/db/support/configuring-reverse-dns)
Notes:
* The smallest IP block sizes available for delegation differ
* Only RIPE NCC is currently tested because I cannot afford IP blocks from the other RIRs
## Compilation
Golang 1.22 or later is officially supported. Before starting, make sure the `GOROOT` and `GOPATH` environment
variables are set correctly and there is a `go` binary is in your `PATH`.
```shell
git clone https://github.com/Jamesits/SND.git
cd SND
go build github.com/jamesits/snd/cmd/snd
```