DNS-over-TLS 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 open source DNS software.
If there are errors or glaring omission please email sara@sinodun.com
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/Forwarders
| Mode | Stub | Caching forwarder/proxy | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Software | (drill) | digit | (Stubby) | BIND (dig) | Go DNS | Knot (kdig) | Unbound | BIND | Knot Res | |
| General | Send ECS with SOURCE PREFIX-LENGTH value of 0 |  | | | ||||||
TCP/TLS Features | TCP fast open(b) | |
| | ||||||
| Connection reuse (Q/R, Q/R, Q/R) | |
| | | | | | |||
Pipelining of queries(Q,Q,Q,R,R,R) | n/a | |
| | | | | | ||
| Process OOOR (Q1,Q2,R2,R1) | n/a | |
| | | | ||||
| EDNS0 Keepalive(c) | | | (g) | |||||||
TLS Features | TLS encryption (Port 853) | | | | | | | |||
| TLS authentication | | | | |||||||
| EDNS0 Padding | | | | | | |||||
| TLS DNSSEC Chain Extension | ||||||||||
Servers
| Mode | Load Balancer | Recursive | Auth | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Software | dnsdist(d) | BIND | Knot Res | CoreDNS(f) | Tenta(f) | NSD | BIND | Knot Auth | ||
| General | QNAME minimisation | n/a | | | ||||||
TCP/TLS Features | TCP fast open(b) | | | | | | | |||
Process Pipelined queries | | | | | | | | |||
| Provide OOOR | (h) | | | n/a | n/a | n/a | ||||
| EDNS0 Keepalive(c) | | | ||||||||
TLS Features | TLS encryption (Port 853) | | | (e) | | | | |||
| Provide TLS auth credentials | | | (e) | | | | ||||
| EDNS0 Padding (basic) | | | | |||||||
| TLS DNSSEC Chain Extension | ||||||||||
KEY:
- Green square - 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, or availabe in next release
- P - Requires building against a patched version of libunbound
(a) getdns uses libunbound in recursive mode
(b) not yet available on Windows
(c) Implies robust TCP connection management (see RFC7828 and RFC7766)
(d) The current implementation is available in the github repo and development packages but is considered experimental pending further testing and feedback
(e) See this article for how to use stunnel with BIND to provide DNS-over-TLS - thanks Francis Dupont!
(f) Full list of supported features to be confirmed
(g) Can be added to queries but the response is currently ignored.
(h) Supports OOOR but could be limited by the nameserver or configuration used for recursion.
Note pipelining and OOOP are not applicable for synchronous applications.
Mobile
| Platform | Status |
|---|---|
| Android | Android supports DNS-over-TLS in the Android P Developer Preview. |
| iOS | Work in underway on an iOS app, however it is currently blocked by an implementation restriction. |
4 Comments
Anonymous
According to http://ftp.isc.org/isc/bind9/9.12.0b1/RELEASE-NOTES-bind-9.12.0b1.html Bind 9.12 should support EDNS0 Padding Option. Not market yellow with "9.12" in table bind in recursive mode.
Sara Dickinson
Thanks for spotting - fixed!
Anonymous
What do the asterisks on "TCP fast open**" and "EDNS0 Keepalive***" indicate?
Sara Dickinson
They should have been (b) and (c) as in the top table. Fixed and thanks.