command module
Version: v1.0.0 Latest Latest

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Published: May 27, 2020 License: MIT Imports: 32 Imported by: 0


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🚀 Privacy important, fast, recursive dns resolver server with dnssec support


go get



or run with Docker image

docker run -d --name sdns -p 53:53 -p 53:53/udp -p 853:853 -p 8053:8053 -p 8080:8080 sdns
  • Port 53 DNS server
  • Port 853 DNS-over-TLS server
  • Port 8053 DNS-over-HTTPS server
  • Port 8080 HTTP API


$ go build


$ make test


Flag Desc
config Location of the config file, if config file not found, a config will generate
v Show version information

Debug Environment

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

SDNS_DEBUGNS enviroment useful when you want to check authoritive servers RTT times. Usage: send HINFO query for zones.

Example Output:

$ dig chaos hinfo

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

; EDNS: version: 0, flags:; udp: 1232
; COOKIE: f27dbb995df5ac79e4fa37c07d131b5bd03aa1c5f802047a7c02fb228a886cb281ecc319323dea81 (good)

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

Configuration (v1.0.0)

Key Desc
version Config version
blocklists List of remote blocklists address list. All lists will be download to blocklist folder.
blocklistdir List of locations to recursively read blocklists from (warning, every file found is assumed to be a hosts-file or domain list)
loglevel What kind of information should be logged, Log verbosity level crit,error,warn,info,debug
accesslog The location of access log file, left blank for disabled. SDNS uses Common Log Format by default.
bind Address to bind to for the DNS server. Default :53
bindtls Address to bind to for the DNS-over-TLS server. Default :853
binddoh Address to bind to for the DNS-over-HTTPS server. Default :8053
tlscertificate TLS certificate file path
tlsprivatekey TLS private key file path
outboundips Outbound ipv4 addresses, if you set multiple, sdns can use random outbound ipv4 address by request based
outboundip6s Outbound ipv6 addresses, if you set multiple, sdns can use random outbound ipv6 address by request based
rootservers DNS Root IPv4 servers
root6servers DNS Root IPv6 servers
rootkeys Trusted anchors for DNSSEC
fallbackservers Failover resolver ipv4 or ipv6 addresses with port, left blank for disabled: Example: ""
api Address to bind to for the http API server, left blank for disabled
nullroute IPv4 address to forward blocked queries to
nullroutev6 IPv6 address to forward blocked queries to
accesslist Which clients allowed to make queries
timeout Network timeout for each dns lookups in duration Default: 2s
hostsfile Enables serving zone data from a hosts file, left blank for disabled
expire Default error cache TTL for in seconds Default: 600
cachesize Cache size (total records in cache) Default: 256000
maxdepth Maximum iteration depth for a query Default: 30
ratelimit Query based ratelimit per second, 0 for disabled. Default: 0
clientratelimit Client ip address based ratelimit per minute, 0 for disable. if client support edns cookie no limit. Default: 0
blocklist Manual blocklist entries
whitelist Manual whitelist entries
cookiesecret DNS cookie secret (RFC 7873), if no cookiesecret set, it will be generate automatically
nsid DNS server identifier (RFC 5001), it's useful while operating multiple sdns. left blank for disabled
chaos Enable to answer version.server, version.bind, hostname.bind and id.server chaos txt queries.
qname_min_level Qname minimize level.If higher, it can be more complex and impact the response performance. If set 0, qname min will be disable

Server Configuration Checklist

  • Increase file descriptor on your server


  • Linux/BSD/Darwin/Windows supported
  • DNS RFC compatibility
  • DNS lookups within listed ipv4 and ipv6 auth servers
  • DNS caching
  • DNSSEC validation
  • DNS over TLS support (DoT)
  • DNS over HTTPS support (DoH)
  • Outbound IP selection
  • Middleware Support, you can add, your own middleware
  • RTT priority within listed servers
  • Failover forwarders while returning failured responses
  • 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


  • 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
  • Automated Updates DNSSEC Trust Anchors described at RFC 5011
  • DNAME Redirection in the DNS described at RFC 6672
  • DNS64 DNS Extensions for NAT from IPv6 Clients to IPv4 Servers described at RFC 6147

Who Used

CubeDNS public open resolver project using sdns on multi location. The project supported both UDP and TCP also DoT and DoH.

Proto Servers
IPv6 2a0a:be80::cbe:4444, 2a0a:be80::cbe:4445


Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

Please make sure to update tests as appropriate.

♥️ Made With

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

Inspired by





Privacy important, fast recursive dns resolver server with dnssec support. for more information.

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