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Implementation Status

This table lists the best understanding of the current status of DNS-over-TLS related features in the latest stable releases of a selection of commonly used open source DNS software.

If there are errors or glaring omission please email sara@sinodun.com 

...

Client - Stub 

...

Client - Recursive

...

Info

Also see guides on how to use NGINX and other proxies to provide DNS-over-TLS, also see here

This works with a couple of provisos:

  • Be aware that a client will think it is talking to a DNS-over-TLS server and so may keep connections open when idle even when not using EDNS0 Keepalive (as allowed by RFC7858 ). The nameserver will see only TCP connections which were historically used just for one-shot TCP and may not be robust to many long-lived connections.
  • Therefore this will work much better if the nameserver has robust TCP capabilities (as described in Sections 6.2.2 and 10 of RFC7766), and would be required for production level service. Any server that fully implements EDNS0 Keepalive (RFC7828) should meet this criteria.

See the DNS Privacy reference material page for more details on the individual features. 

Clients

Mode

Stub 

Recursive resolver

Software

ldns

(drill)

digit

getdns

(Stubby)

BIND

(dig)

getdns*
Go
Unbound
DNS 
BIND

Knot

(kdig)

getdns(a)

UnboundBIND
NSD

Knot

BIND

Res

Port based



TCP/TLS

 

Features

TCP fast open(b)
(tick)

(tick)

2016



P



(tick)
Connection reuse (Q/R, Q/R, Q/R)
(tick)
 

(tick)

(tick)
2016
(tick)
 
(tick)
 TCP fast open** 


(tick)(tick)

Pipelining of queries(Q,Q,Q,R,R,R)

n/a(tick)

(tick)

2016
(tick)
P
(tick)
 
(tick)
 Connection reuse 


(tick)
 2016  
(tick)
Process OOOR (Q1,Q2,R2,R1)n/a (tick)

(tick)

(tick)



(tick)(tick)
EDNS0 Keepalive(c)

(tick)
WIPWIP n/a









TLS Features

TLS encryption (Port 853)
(tick)(tick)
(tick)(tick)(tick)

Pipelining***

(tick)

TLS authentication

(tick)






EDNS0 Padding
(tick)(tick)

(tick)



Servers

ModeRecursiveAuth
Software

Unbound

BIND

Knot

Res

NSDBIND

Knot

Auth


TCP/TLS Features

TCP fast open**(tick)(tick)(tick)
n/a20162016 n/a


(tick)

Process Pipelined queries

(tick)(tick)(tick)(tick)(tick)(tick)
OOOP***
Provide OOORWIP(tick)(tick)n/a
       

 

n/an/a
EDNS0 Keepalive***WIP






TLS Features

TLS encryption (Port 853)(tick)(d)(tick)


Provide TLS auth credentials(tick)(d)(tick)


TLS DNSSEC Chain Extension





EDNS0 Padding (basic)

(tick)



KEY:

  • Green square (tick) - indicates latest release already supports this functionality
  • Blue square - indicates that a patch is available in our git repo. See here for details: DNS-over-TLS patches
  • Yellow square - indicates work in progress
  • 2016 - indicates patches planned for 2016
  • , or availabe in next release
  • P - Requires building against a patched version of libunbound

* (a)    getdns uses libunbound in recursive mode
**  not (b)    not yet available on Windows 
***  Pipelining and (c)    Implies robust TCP connection management (see RFC7828 and RFC7766)
(d)   See this article for how to use stunnel with BIND to provide DNS-over-TLS - thanks Francis Dupont!

Note pipelining and OOOP are not applicable for synchronous applications.