Internet DRAFT - draft-salgado-dnsop-rrserial
draft-salgado-dnsop-rrserial
Internet Engineering Task Force H. Salgado
Internet-Draft NIC Chile
Intended status: Informational M. Vergara Ereche
Expires: 5 December 2021 ICANN
3 June 2021
The "RRSERIAL" EDNS option for the SOA serial of a RR's zone
draft-salgado-dnsop-rrserial-01
Abstract
The "RRSERIAL" EDNS option allows a DNS querier to request a DNS
authoritative server to add an EDNS option in the answer of such
query with the SOA serial number field of the origin zone which
contains the answered Resource Record.
This "RRSERIAL" data allows to debug and diagnose problems by helping
to recognize the data source of an answer in an atomic single query,
by associating the response with a respective zone version.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. The RRSERIAL Option . . . . . . . . . . . . . . . . . . . . . 3
3. RRSERIAL Processing . . . . . . . . . . . . . . . . . . . . . 3
3.1. Initiator . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. Responder . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Example usage . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6.1. DNS EDNS0 Option Code Registration . . . . . . . . . . . 4
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. Normative References . . . . . . . . . . . . . . . . . . . . 5
9. Informative References . . . . . . . . . . . . . . . . . . . 5
Appendix A. Implementation References . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
The "RRSERIAL" EDNS option [RFC6891] allows a DNS querier to request
to a DNS authoritative server to add an EDNS option in the answer of
such query with the SOA serial number field of the zone associated to
the answered Resource Record.
This "RRSERIAL" data allows to help debug by recognizing the data
source of an answer, associating this answer with a respective zone
version.
DNS data is of loose coherent nature, meaning that a record obtained
by a response could be out-of-sync with other authoritative sources
of the same data. This makes it difficult to debug responses,
because you'd need to couple an answer with the same version of the
zone used to obtain such data. Even when you could use a separate
query to ask for the SOA RR of the zone and therefore know its SOA
serial, such separate query is performed in a different time and
could arrive from another authoritative source (for example, in the
case the server is anycasted as described in Section 4.9 of
[RFC4786]), so it's not directly correlated with the original query.
This EDNS option is aimed to be used only on authoritative servers
for a zone. It's intended for hop-to-hop communication (not
transitive). Resolver and forwarder behavior is undefined.
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The RRSERIAL EDNS extension doesn't offer much relevance for zones
served by an Authoritative server that don't use the SOA serial
versioning as a meaning to its content. There are cases where
nameservers use different backends for its data sources, like
relational databases or by using a different off-DNS synchronicity.
In such cases this extension has no benefit or utility to use in
debugging or analysis of a response.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. The RRSERIAL Option
The OPTION-CODE for the RRSERIAL option is <TBD>.
The OPTION-DATA for the RRSERIAL option is an unsigned 32 bit version
number as defined in the SERIAL field of the "SOA RDATA Format" in
Section 3.3.13 of [RFC1035].
The OPTION-LENGTH for the RRSERIAL option MUST have a value of 0 for
queries, and MUST have a value of 4 for responses.
3. RRSERIAL Processing
3.1. Initiator
The EDNS RRSERIAL option MAY be included on any QUERY, by adding a
zero-length EDNS RRSERIAL option to the options field of the OPT
record when the query is made.
3.2. Responder
If an EDNS RRSERIAL option is sent to a server that is Authoritative
for the zone queried, and the RCODE for the answer is NOERROR, a name
server that understands the RRSERIAL option and chooses to honor a
particular RRSERIAL request, MUST put in the OPTION-DATA a copy of
the serial field from the SOA Resource Record of the zone which
contains the original QNAME of the reply (as per Section 4 of
[RFC8499]).
In the case of a SERVFAIL RCODE the responder MAY include the
RRSERIAL EDNS option if the QNAME still belongs to an authoritative
zone of the server, in which case that serial MUST be the one
included in the answer.
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Otherwise, the answer MUST NOT add an EDNS RRSERIAL option to the
response.
Note that a NODATA response code as defined in Section 3 of [RFC8499]
MUST also include the RRSERIAL answer as declared before even when
there's no ANSWER data for the QNAME, as the RCODE corresponds to
NOERROR.
4. Example usage
$ dig @ns.example.com www.example.com AAAA +rrserial +norec +nocmd
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 16429
;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
; RRSERIAL: 2019073001
;; QUESTION SECTION:
;www.example.com. IN AAAA
;; ANSWER SECTION:
www.example.com. 900 IN AAAA
;; Query time: 53 msec
;; SERVER: ns.example.com#53(2001:DB8::53)
;; WHEN: Tue Aug 07 16:54:05 -04 2018
;; MSG SIZE rcvd: 71
Figure 1
5. Acknowledgements
The authors thanks all the comments and support made in the DNSOPS
mailing list, chats and discussions.
6. IANA Considerations
6.1. DNS EDNS0 Option Code Registration
Request to IANA for a code point registration for "RRSERIAL" option.
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7. Security Considerations
The EDNS extension data it's not covered by RRSIG records, so there's
no way to verify its authenticity nor integrity using DNSSEC and
could theoricatelly be tampered by a person-in-the-middle if the
transport is made by unsecure means. Caution should be taken to use
the EDNS RRSERIAL data for any means besides troubleshooting and
debugging. If there's a need to certify the RRSERIAL trustwortiness,
it will be necessary to use an encrypted and authenticated DNS
transport. If there's a need to authenticate data origin for the
RRSERIAL value, it should be compared to a separate regular SOA query
with DO flag, whose answer shall be DNSSEC signed, with the cautions
about Anycast and others as already stated in Introduction.
There's no risk on disclosure of private information, as the SERIAL
of the SOA record is already publicly available.
8. Normative References
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[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>.
[RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
for DNS (EDNS(0))", STD 75, RFC 6891,
DOI 10.17487/RFC6891, April 2013,
<https://www.rfc-editor.org/info/rfc6891>.
9. Informative References
[RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast
Services", BCP 126, RFC 4786, DOI 10.17487/RFC4786,
December 2006, <https://www.rfc-editor.org/info/rfc4786>.
[RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
January 2019, <https://www.rfc-editor.org/info/rfc8499>.
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Appendix A. Implementation References
There's a patched NSD server 4.1.23 with support for RRSERIAL with
the experimental opcode 65024 maintained in
https://github.com/huguei/nsd/tree/rrserial , and installed for live
testing in 200.1.122.30 address with configured zones
dateserial.example.com. and incserial.example.com.; with MX, TXT and
AAAA apex records.
Authors' Addresses
Hugo Salgado
NIC Chile
Miraflores 222, piso 14
CP 8320198 Santiago
Chile
Phone: +56 2 29407700
Email: hsalgado@nic.cl
Mauricio Vergara Ereche
ICANN
Email: mauricio.vergara@icann.org
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