SDNS 🚀

A high-performance, recursive DNS resolver server with DNSSEC support, focused on preserving privacy.

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Installation

Use the go get command to install sdns:

go get github.com/semihalev/sdns

Pre-build Binaries

You can download the latest release from the Github Repo.

Docker

• Docker Package (updated every release)
• Docker Hub (alternative)

$ docker run -d --name sdns -p 53:53 -p 53:53/udp sdns

Docker Compose

Install docker-compose and run from the root directory:

$ sudo apt install docker-compose
$ docker-compose up -d

Homebrew for macOS

Install and run as a service:

$ brew install sdns
$ brew install semihalev/tap/sdns (updated every release)
$ brew services start sdns

Snapcraft

$ snap install sdns

AUR for ArchLinux

$ yay -S sdns-git

Note: Pre-built binaries, Docker packages, brew taps, and snaps are automatically created by Github workflows.

Building from Source

Linux:

$ go build

$ # Cross compile to linux amd64
$ CGO_ENABLED=0  GOOS=linux  GOARCH=amd64 go build

Powershell:

$env:CGO_ENABLED=0
$env:GOOS="linux"
$env:GOARCH="amd64"
go build

Testing

$ make test

Flags

Flag	Desc
-c, --config PATH	Location of the config file. If it doesn't exist, a new one will be generated.
-v, --version	Show the version of the sdns.
-h, --help	Show this help and exit.

Debugging Environment

To debug your environment, execute the following command:

$ export SDNS_DEBUGNS=true && export SDNS_PPROF=true && ./sdns

The SDNS_DEBUGNS environment variable is beneficial for verifying the RTT (Round Trip Time) of authoritative servers. To use it, send an HINFO query for zones with chaos class.

Here's an example of the output you might receive:

$ dig chaos hinfo example.com

; <<>> DiG 9.17.1 <<>> chaos hinfo example.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 29636
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 4, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
; COOKIE: f27dbb995df5ac79e4fa37c07d131b5bd03aa1c5f802047a7c02fb228a886cb281ecc319323dea81 (good)
;; QUESTION SECTION:
;example.com.			CH	HINFO

;; AUTHORITY SECTION:
example.com.		0	CH	HINFO	"Host" "IPv4:199.43.135.53:53 rtt:142ms health:[GOOD]"
example.com.		0	CH	HINFO	"Host" "IPv4:199.43.133.53:53 rtt:145ms health:[GOOD]"
example.com.		0	CH	HINFO	"Host" "IPv6:[2001:500:8f::53]:53 rtt:147ms health:[GOOD]"
example.com.		0	CH	HINFO	"Host" "IPv6:[2001:500:8d::53]:53 rtt:148ms health:[GOOD]"

Configuration (v1.3.3)

Key	Description
version	Configuration version
directory	sdns working directory (must grant write access to sdns user)
bind	DNS server binding address Default: :53
bindtls	DNS-over-TLS server binding address Default: :853
binddoh	DNS-over-HTTPS server binding address Default: :8053
binddoq	DNS-over-QUIC server binding address Default: :853
tlscertificate	Path to the TLS certificate file
tlsprivatekey	Path to the TLS private key file
outboundips	Outbound IPv4 addresses (randomly chosen if multiple entries provided)
outboundip6s	Outbound IPv6 addresses (randomly chosen if multiple entries provided)
rootservers	DNS Root IPv4 servers
root6servers	DNS Root IPv6 servers
rootkeys	Trusted DNSSEC anchors
fallbackservers	Failover resolver IPv4 or IPv6 addresses with port (leave blank to disable) Example: "8.8.8.8:53"
forwarderservers	Forwarder resolver IPv4 or IPv6 addresses with port (leave blank to disable) Example: "8.8.8.8:53"
api	HTTP API server binding address (leave blank to disable)
blocklists	Remote blocklist address list (downloaded to the blocklist folder)
blocklistdir	[DEPRECATED] Directory creation is automated in the working directory
loglevel	Log verbosity level (crit, error, warn, info, debug)
accesslog	Location of the access log file (leave blank to disable) Default: Common Log Format
nullroute	IPv4 address for forwarding blocked queries
nullroutev6	IPv6 address for forwarding blocked queries
accesslist	Client whitelist for query permissions
querytimeout	Maximum wait duration for DNS query response Default: 10s
timeout	Network timeout duration for each DNS lookup Default: 2s
hostsfile	Enable serving zone data from a hosts file (leave blank to disable)
expire	Default error cache TTL (in seconds) Default: 600
cachesize	Cache size (total records in cache) Default: 256000
prefetch	Cache prefetch before expiry (threshold: 10%-90%, 0 to disable)
maxdepth	Maximum iteration depth per query Default: 30
ratelimit	Query-based rate limit per second (0 to disable) Default: 0
clientratelimit	Client IP address-based rate limit per minute (no limit if client supports EDNS cookie) Default: 0
blocklist	Manual blocklist entries
whitelist	Manual whitelist entries
cookiesecret	DNS cookie secret (RFC 7873) - auto-generated if not set
nsid	DNS server identifier (RFC 5001) - useful for operating multiple sdns instances (leave blank to disable)
chaos	Enable responses to version.server, version.bind, hostname.bind and id.server chaos txt queries
qname_min_level	Qname minimize level (0 to disable - higher values increase complexity and impact response performance)
emptyzones	Enable response to RFC 1918 zone queries. For details, see http://as112.net/

Plugin Configuration

In sdns, you have the ability to add custom plugins. The sequence of the plugins and the middlewares has a mutual impact on their execution. Config keys must be strings, and values can be of any type. Plugins are loaded before the cache middleware in the specified order.

The plugin interface is straightforward. For additional information, please refer to the example plugin.

Example Configuration

[plugins]
     [plugins.example]
     path = "/path/to/exampleplugin.so"
     config = {key_1 = "value_1", intkey = 2, boolkey = true, keyN = "nnn"}
     [plugins.another]
     path = "/path/to/anotherplugin.so"

Server Configuration Checklist

• Increase the file descriptor limit on your server

Features

• Linux/BSD/Darwin/Windows supported
• DNS RFC compatibility
• DNS lookups within listed ipv4 and ipv6 auth servers
• DNS caching with prefetch support
• DNSSEC validation
• DNS over TLS support (DoT)
• DNS over HTTPS support (DoH) with HTTP/3 support
• DNS over QUIC support (DoQ)
• Outbound IP selection
• Middleware Support, you can add, your own middleware
• RTT priority within listed servers
• Failover forwarders while returning failured responses
• Forwarder support
• EDNS Cookie Support (client<->server)
• EDNS NSID Support
• Full IPv6 support (client<->server, server<->server)
• Query based ratelimit
• IP based ratelimit
• Access list
• Access log
• Prometheus basic query metrics
• Black-hole for malware responses
• HTTP API support
• Cache Purge API and query support
• Answer chaos txt queries for version.bind and hostname.bind
• Empty zones support described at RFC 1918
• External plugins supported

TODO

• More tests
• Try lookup NS address better way
• DNS over TLS support
• DNS over HTTPS support
• Full DNSSEC support
• RTT optimization
• Access list
• Periodic priming queries described at RFC 8109
• Full IPv6 support (server<->server communication)
• Query name minimization to improve privacy described at RFC 7816
• DNAME Redirection in the DNS described at RFC 6672
• Automated Updates DNSSEC Trust Anchors described at RFC 5011
• DNS64 DNS Extensions for NAT from IPv6 Clients to IPv4 Servers described at RFC 6147
• DNS over QUIC support described at RFC 9250

Performance

Benchmark Environment

• Server Specifications:
  • Processor: Intel Xeon E5-2609 v4 CPU
  • Memory: 32GB

Benchmarking Tool

• Tool Name: DNS-OARC dnsperf
• Benchmark Configuration:
  • Query Data Volume: 50,000 sample queries

Benchmark Comparisons

Benchmarks were performed on the following DNS resolvers: sdns-1.3.3, pdns-recursor-4.8.4, bind-9.19.12, unbound-1.17.1.

Benchmark Results

Resolver	RESPONSE	LOST	NOERROR	SERVFAIL	NXDOMAIN	Run Time	QPS
SDNS	100%	1	35,164	866	13,969	87s47ms	571/s
PowerDNS	99.99%	6	35,140	893	13,961	88s83ms	563/s
Bind	99.74%	132	35,024	885	13,959	127s64ms	390/s
Unbound	99.49%	253	35,152	624	13,971	174s64ms	284/s

Contributing

We welcome pull requests. If you're considering significant changes, please start a discussion by opening an issue first.

Before submitting patches, please review our CONTRIBUTING guidelines.

♥️ Made With

• miekg/dns - Alternative (more granular) approach to a DNS library

Inspired by

• coredns/coredns
• looterz/grimd

License

MIT