Internet DRAFT - draft-grubto-dnsop-dns-out-of-protocol-signalling
draft-grubto-dnsop-dns-out-of-protocol-signalling
DNSOP Working Group C. Almond
Internet-Draft ISC
Intended status: Standards Track P. van Dijk
Expires: 11 January 2024 PowerDNS
M.W. Groeneweg
S.W.J. Ubbink
SIDN
D. Salzman
CZ.NIC
W. Toorop
NLnet Labs
10 July 2023
DNS Out Of Protocol Signalling
draft-grubto-dnsop-dns-out-of-protocol-signalling-03
Abstract
This document seeks to specify a method for DNS servers to signal
programs outside of the server software, and which are not
necessarily involved with the DNS protocol, about conditions that can
arise within the server. These signals can be used to invoke actions
in areas that help provide the DNS service, such as routing.
Currently this document serves as a requirements document to come to
a signalling mechanism that will suit the use cases best. Part of
that effort is to assemble a list of conditions with potential
associated out of DNS protocol actions, as well as inventory and
assess existing signalling mechanisms for suitability.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 11 January 2024.
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Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology and Definitions . . . . . . . . . . . . . . . . . 3
3. Conditions to be signalled . . . . . . . . . . . . . . . . . 3
3.1. The DNS server is running and can respond to queries . . 4
3.2. Shutting down . . . . . . . . . . . . . . . . . . . . . . 4
3.3. The nameserver has crashed . . . . . . . . . . . . . . . 4
3.4. A zone is loaded and ready to serve . . . . . . . . . . . 5
3.5. All zones are loaded and ready to serve . . . . . . . . . 5
3.6. A zone is updated to a new version . . . . . . . . . . . 5
3.7. A zone is (about to) expire . . . . . . . . . . . . . . . 6
3.8. DNSSEC signatures are (about to) expire . . . . . . . . . 6
3.9. Query rate is exceeding a threshold . . . . . . . . . . . 6
3.10. Query rate increase is exceeding a threshold . . . . . . 7
3.11. Extended DNS Error conditions . . . . . . . . . . . . . . 7
4. Requirements for signalling mechanisms and channels . . . . . 7
5. Existing signalling mechanisms and channels . . . . . . . . . 7
5.1. Notify . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.2. D-Bus as publication channel . . . . . . . . . . . . . . 8
5.3. DDoS Open Threat Signaling . . . . . . . . . . . . . . . 8
5.4. MQTT . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.5. Observations and comparison . . . . . . . . . . . . . . . 9
6. Security and Privacy Considerations . . . . . . . . . . . . . 10
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 10
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
10. Normative References . . . . . . . . . . . . . . . . . . . . 10
11. Informative References . . . . . . . . . . . . . . . . . . . 11
Appendix A. Implementation Status . . . . . . . . . . . . . . . 11
Appendix B. Change History . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
Operators of DNS servers can benefit from automatically taking action
upon certain conditions in the name server software. Some conditions
can be monitored from outside the server software, but for adequate
and immediate action, the server software itself should signal about
the condition immediately when it occurs to invoke action by a
listener for these signals.
An example of such a condition is when all zones, from a set served
from an anycasted prefix, are loaded and ready to be served. An
associated action may be to start announcing a prefix route from the
point-of-presence where the name server is running and to withdraw
the prefix route if one of the zones cannot be served anymore. This
way queries for zones will only reach the point-of-presence if the
name server software can answer those queries.
Another example condition may be if an recursive resolver served from
an anycasted prefix, is started and ready to serve, with the same
associated action of only announcing the anycasted prefix when the
recursive resolver can serve queries.
All anycasted DNS services can benefit from the mechanism alone, by
the increased adequacy and reduced resources of not having to poll
for a server's state. DNS services with diverse implementations will
benefit from standardizing of the name server signalling.
Before coming to a specification for the mechanism, this document
will serve to inventorise the already available standardized and non-
standardized signalling channels and assess them for usability for
out of protocol signalling.
2. Terminology and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Conditions to be signalled
This section served to collect a list of conditions for which actions
outside of the DNS protocol may be interesting. A signal will be
sent if the condition is met, and also when the condition is no
longer met. Some conditions take configuration parameters
influencing when the conditions are met. Some conditions may contain
arguments when signalled. When applicable, the parameters and
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arguments are given with each condition.
Some conditions may be identified from outside of the DNS server by
polling for the condition. This is more resource intensive that
listening for a signal, but may also be more robust. When this is
the case, how the condition can be identified is provided with the
condition.
3.1. The DNS server is running and can respond to queries
How to identify:
* check if the DNS server is running by doing a query to see if it
responds
Action:
* Start announcing the prefix on which this zone is served with BGP
A announcement may be withdrawn when the condition is no longer
met.
3.2. Shutting down
How to identify:
* Maintenance, before shutting down the name server, initiate at
least the BGP withdrawl
Action:
* Stop the BGP announcement of the prefix
3.3. The nameserver has crashed
How to identify:
* The name server is no longer running (or does not respond to
queries, although that might also be the case when it is under an
attack)
Action:
- Stop the BGP announcement of the prefix
This condition maybe only detected from outside of the DNS server.
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3.4. A zone is loaded and ready to serve
How to identify:
* Query the zone to see if it responds
Argument:
* The zone that was loaded
Action:
* Start announcing the prefix on which these zones are served with
BGP. A announcement may be withdrawn when the condition is no
longer met.
Some name servers, when configured to notify targets when a zone is
updated [RFC1996], will also notify those targets when a zone is just
loaded. The notify itself may be considered an appropriate signal,
although it will not be emitted when the zone is no longer served.
3.5. All zones are loaded and ready to serve
Action:
* Start announcing the prefix on which these zones are served with
BGP. A announcement may be withdrawn when the condition is no
longer met.
This condition may be derived from one or more "A zone is loaded and
ready to serve" (Section 3.4) signals when a list of all zones served
is available.
3.6. A zone is updated to a new version
How to identify:
* Query the zone's SOA record, register value and then compare to
expected version
Argument:
* The zone that was updated
Action:
* Verify the zone content. Is it DNSSEC valid, does the ZONEMD
validate.
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Name servers can usually already signal this with NOTIFY [RFC1996]
3.7. A zone is (about to) expire
Parameter:
* The period before expiration. A value of 0 will emit the signal
the moment the zone expires.
Argument:
* The zone that is (about to) expire
Action:
* Stop the BGP announcement of the prefix on which the zone is
served. It may be reannounced when the zone becomes available
again (See Section 3.4).
3.8. DNSSEC signatures are (about to) expire
Parameter:
* The period before expiration. A value of 0 will emit the signal
the DNSSEC signature expires.
Argument:
* The zone that contains the signature
* The resource record set owner name and type with the signature
that will soon expire
Action:
* Stop the BGP announcement of the prefix on which the zone is
served. It may be reannounced when the zone becomes DNSSEC valid
again.
3.9. Query rate is exceeding a threshold
Parameter:
* The number of queries per second threshold.
Action:
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* Lengthen the AS path for the BGP announcement for a prefix, to
demotivate the anycast node that receives all the queries.
* Or if the query rate is indicating a denial of service attack,
keep the BGP AS path short, to absorb the attack.
* Signal to Security Information and Event Management SIEM and
logging that problem has been observed.
3.10. Query rate increase is exceeding a threshold
Parameter:
* The number of queries per second increase per second threshold.
Action:
* The same actions as for "Query rate is exceeding a threshold"
(Section 3.9) apply.
3.11. Extended DNS Error conditions
Parameter:
* The Extended DNS Error conditions for which to signal [RFC8914]
Argument:
* The Extended DNS Error condition that occurred.
Action:
* Dependent on the DNS Error condition
4. Requirements for signalling mechanisms and channels
* All conditions are sensitive information and should be stay either
in the administered domain (for example on the local machine that
is under control of the operator), or needs to be authenticated.
5. Existing signalling mechanisms and channels
What follows is a list of existing signalling mechanisms and a
comparison of those channels in Section 5.5.
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5.1. Notify
DNS NOTIFY [RFC1996] is an existing ubiquitous mechanism to signal
zones. It is intended to target name servers, but tooling exists to
listen for NOTIFY messages and trigger execution of a command when a
zone is updated (See [nsnotifyd]).
Advantages:
* Native signalling for zone updates present right now (See
Section 3.6)
* Indirect support for zone loaded (See Section 3.4)
Disadvantages:
* One available Open Source Software which lacks authentication
support and is therefore only suitable for local usage
* Only two conditions are signalled.
* Does not signal when the conditions are no longer met.
5.2. D-Bus as publication channel
D-Bus is a mechanism for exchanging messages between processes local
on the same machine (See [D-Bus]). The D-BUS protocol is a one-to-
one protocol, but distribution of messages (or signals) to multiple
other applications is carried out by a program intended for this
purpose: the D-Bus _message bus_.
Advantages:
* Implementation already exists (See [Knot-DNS-3.1.6])
* Good Open Source Software library support [TODO references]
Disadvantages:
* Server needs to be started before clients making it less robust.
* Is only communicated locally to the machine
5.3. DDoS Open Threat Signaling
DDoS Open Threat Signaling (DOTS) [RFC9132] is a set of protocols for
real-time signaling of threat-mitigation requests within and between
different operational domains.
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Advantages:
* Publish / Subscribe mechanism
* Inter-operator communications
* Authenticated
* Open Source server software exists [TODO reference go-dots]
Disadvantages:
* No Open Source client library exists? We need to get information
during the upcoming hackathon at the IETF117. Current DOTS builds
upon CoAP [RFC7252] for which many client library implementations
exist.
5.4. MQTT
MQTT (see [MQTT-OASIS-Standard-v5]) is a lightweight publish-
subscribe network protocol for messages.
Advantages:
* Network Publish / Subscribe mechanism
* Supports authentication
Disadvantages:
* Need to gain experience at the IETF117 hackathon
5.5. Observations and comparison
+=============================+========+=======+======+======+
| Method | NOTIFY | D-Bus | DOTS | MQTT |
+=============================+========+=======+======+======+
| Local to machine | + | ++ | + | + |
+-----------------------------+--------+-------+------+------+
| inter-machine | + | - | + | + |
+-----------------------------+--------+-------+------+------+
| inter-operator | + | - | ++ | - |
+-----------------------------+--------+-------+------+------+
| Publish Subscribe | - | - | ++ | ++ |
+-----------------------------+--------+-------+------+------+
| Authentication | +- | - | + | + |
+-----------------------------+--------+-------+------+------+
| Client library availability | NA | ++ | ? | ++ |
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+-----------------------------+--------+-------+------+------+
Table 1
6. Security and Privacy Considerations
Signalling MUST be performed in an authenticated and private manner.
7. Implementation Status
* Knot DNS has support for D-Bus notifications (See Section 5.2) for
significant server and zone events with the "dbus-event"
configuration parameter since version 3.1.6 [Knot-DNS-3.1.6]
* NSD has a feature branch [NSD-oops-branch] where work is being
done on the implementation
8. IANA Considerations
This document has no IANA actions
9. Acknowledgements
We would like to thank the people of the port53 hackathon in
Rotterdam for their contributions. Mainly Doris Hauser, Lars-Johan
Liman, Vilhelm Prytz and Henrik Kramselund
10. Normative References
[RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone
Changes (DNS NOTIFY)", RFC 1996, DOI 10.17487/RFC1996,
August 1996, <https://www.rfc-editor.org/info/rfc1996>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014,
<https://www.rfc-editor.org/info/rfc7252>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
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[RFC8914] Kumari, W., Hunt, E., Arends, R., Hardaker, W., and D.
Lawrence, "Extended DNS Errors", RFC 8914,
DOI 10.17487/RFC8914, October 2020,
<https://www.rfc-editor.org/info/rfc8914>.
[RFC9132] Boucadair, M., Ed., Shallow, J., and T. Reddy.K,
"Distributed Denial-of-Service Open Threat Signaling
(DOTS) Signal Channel Specification", RFC 9132,
DOI 10.17487/RFC9132, September 2021,
<https://www.rfc-editor.org/info/rfc9132>.
11. Informative References
[D-Bus] Pennington, H., Carlsson, A., Larsson, A., Herzberg, S.,
McVittie, S., and D. Zeuthen, "D-Bus Specification",
February 2023, <https://dbus.freedesktop.org/doc/dbus-
specification.html>.
[Knot-DNS-3.1.6]
CZ.NIC, "Knot DNS - Version 3.1.6", February 2022,
<https://www.knot-dns.cz/2022-02-08-version-316.html>.
[MQTT-OASIS-Standard-v5]
Banks, A., Briggs, E., Borgendale, K., and R. Gupta,
"OASIS Standard MQTT Version 5.0", 19 March 2019,
<https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-
v5.0-os.html>.
[NSD-oops-branch]
NLnet Labs, "NSD feature/oops branch", May 2023,
<https://github.com/NLnetLabs/nsd/tree/features/oops>.
[nsnotifyd]
Finch, T., "nsnotifyd: scripted DNS NOTIFY handler",
January 2022, <https://dotat.at/prog/nsnotifyd/>.
Appendix A. Implementation Status
*Note to the RFC Editor*: please remove this entire appendix before
publication.
Knot currently uses [D-Bus] for this.
Appendix B. Change History
*Note to the RFC Editor*: please remove this entire appendix before
publication.
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* draft-grubto-dnsop-dns-out-of-protocol-signalling-03
| Rename "name server" into "DNS server" when it also applies to
| recursive resolvers
|
| Make a single list of conditions with per condition indicated the
| parameters (how they can be influenced by configuration), the
| arguments (the signal payload) and "how to identify" if the
| condition can be identified from outside of the DNS server.
|
| Removing DNS Error reporting monitoring agent as a channel to
| evaluate
|
| Add DOTS and MQTT as a potential signal channels for our
| conditions
* draft-grubto-dnsop-dns-out-of-protocol-signalling-02
| Updates after discussion during the port53 hackathon in Rotterdam.
* draft-grubto-dnsop-dns-out-of-protocol-signalling-00
| Initial version
Authors' Addresses
Cathy Almond
Internet Systems Consortium, Inc.
PO Box 360
Newmarket, NH 03857
United States of America
Phone: +1 650 423 1300
Email: cathya@isc.org
Peter van Dijk
PowerDNS
Den Haag
Netherlands
Email: peter.van.dijk@powerdns.com
Marc Groeneweg
Stichting Internet Domeinregistratie Nederland
Postbus 5022
6802EA Arnhem
Netherlands
Email: marc.groeneweg@sidn.nl
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Stefan Ubbink
Stichting Internet Domeinregistratie Nederland
Postbus 5022
6802EA Arnhem
Netherlands
Email: stefan.ubbink@sidn.nl
Daniel Salzman
CZ.NIC
Czechia
Email: daniel.salzman@nic.cz
Willem Toorop
NLnet Labs
Science Park 400
1098 XH Amsterdam
Netherlands
Email: willem@nlnetlabs.nl
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