Skip to main content

DNS Multiple QTYPEs
draft-ietf-dnssd-multi-qtypes-00

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft whose latest revision state is "Active".
Author Ray Bellis
Last updated 2023-12-04
Replaces draft-bellis-dnsext-multi-qtypes
RFC stream Internet Engineering Task Force (IETF)
Formats
Additional resources Mailing list discussion
Stream WG state WG Document
Document shepherd (None)
IESG IESG state I-D Exists
Consensus boilerplate Unknown
Telechat date (None)
Responsible AD (None)
Send notices to (None)
draft-ietf-dnssd-multi-qtypes-00
DNSSD Working Group                                            R. Bellis
Internet-Draft                                                       ISC
Intended status: Standards Track                         4 December 2023
Expires: 6 June 2024

                          DNS Multiple QTYPEs
                    draft-ietf-dnssd-multi-qtypes-00

Abstract

   This document specifies a method for a DNS client to request
   additional DNS record types to be delivered alongside the primary
   record type specified in the question section of a DNS query.

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 6 June 2024.

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
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Bellis                     Expires 6 June 2024                  [Page 1]
Internet-Draft             DNS Multiple QTYPEs             December 2023

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology used in this document . . . . . . . . . . . . . .   3
   3.  Description . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Multiple QTYPE EDNS Option Format . . . . . . . . . . . .   3
     3.2.  Response Generation . . . . . . . . . . . . . . . . . . .   4
       3.2.1.  Server Side Processing  . . . . . . . . . . . . . . .   4
       3.2.2.  Client Side Processing  . . . . . . . . . . . . . . .   5
       3.2.3.  DNSSEC  . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   RFC EDITOR: PLEASE REMOVE THE FOLLOWING PARAGRAPH BEFORE PUBLISHING:
   The source for this draft is maintained in GitHub at:
   https://github.com/raybellis/draft-ietf-dnssd-multi-qtypes Please
   submit suggested changes as issues or pull requests there.

   A commonly requested DNS [RFC1035] feature is the ability to receive
   multiple related resource records (RRs) in a single DNS response.

   For example, it may be desirable to receive both the A and AAAA
   records for a domain name together, rather than having to issue
   multiple queries.

   The DNS wire protocol in theory supports having multiple questions in
   a single packet, but in practise this does not work:

   *  Each question consists of the tuple (QNAME, QTYPE, QCLASS).  Since
      each question has its own QNAME field it would be possible for one
      name to exist and another to not exist, resulting in an
      inconsistent response code.

   *  [RFC1035] says that QDCOUNT is "usually 1" but the only documented
      exceptions relate to the IQuery OpCode which was obsoleted in
      [RFC3425].  Other text in [RFC1035] strongly implies a singular
      question.

Bellis                     Expires 6 June 2024                  [Page 2]
Internet-Draft             DNS Multiple QTYPEs             December 2023

   *  The idea that only a single question is allowed is sufficiently
      entrenched that many DNS servers will simply return an error (or
      fail to response at all) if they receive a query with a question
      count (QDCOUNT) of more than one.

   To mitigate these issues, this document constrains the problem to
   those cases where only the QTYPE varies by specifying a new option
   for the Extension Mechanisms for DNS (EDNS [RFC6891]) that contains
   an additional list of QTYPE values that the client wishes to receive
   in addition to the single QTYPE appearing in the question section.

   TODO: why not "ANY" ?

2.  Terminology used in this document

   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.  Description

3.1.  Multiple QTYPE EDNS Option Format

   The overall format of an EDNS option is shown for reference below,
   per [RFC6891], followed by the option specific data:

      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   0: |                          OPTION-CODE                          |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   2: |                         OPTION-LENGTH                         |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   4: |                                                               |
      /                          OPTION-DATA                          /
      /                                                               /
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

   OPTION-CODE: TBD by IANA

   OPTION-LENGTH: Size (in octets) of OPTION-DATA.

   OPTION-DATA: Option specific, as below:

Bellis                     Expires 6 June 2024                  [Page 3]
Internet-Draft             DNS Multiple QTYPEs             December 2023

                   +0 (MSB)                            +1 (LSB)
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   0: |QTD|   reserved    |  QTCOUNT  |           QT1 (MSB)           |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   2: |           QT1 (LSB)           |              ...              |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
      |              ...             ///          QTn (MSB)           |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
      |           QTn (LSB)           |
      +---+---+---+---+---+---+---+---+

   QTD: this bit indicates the direction of the packet.  It MUST be
   clear (0) in a request and set (1) in a response.

   QTCOUNT: a 3 bit field with range 0 .. 7 specifying the number of QT
   fields to follow.  NB: Whilst the QTCOUNT could in theory be
   calculated based on the OPTION-LENGTH field, having it explicitly
   specified ensures a sensible constraint on its range of values.

   QTn: a 2 byte field (MSB first) specifying a DNS RR type.  The RR
   type MUST be for a real resource record, and MUST NOT refer to a
   pseudo RR type such as "OPT", "IXFR", "TSIG", "*", etc.

3.2.  Response Generation

3.2.1.  Server Side Processing

   A conforming server that receives a Multiple QTYPE Option in a query
   MUST return a Multiple QTYPE Option in its response.

   The QTD bit in that response MUST be set (1) as protection against
   servers which simply echo unknown EDNS options verbatim.  If the QTD
   bit in a response is zero the client MUST treat the response as if
   this option is unsupported.

   The server SHOULD attempt to return any resource records known to it
   that match the additional (QNAME, QTn, QCLASS) tuples.  These records
   MUST be returned in the Answer Section of the response, but the
   answer for the primary QTYPE from the Question Section MUST be
   included first.

   For any particular QTn in the query, if the server provides
   additional answers, or has knowledge that the RR type type does not
   exist for that QNAME (a "negative answer"), it must include that QTn
   value in the Multiple QTYPE Option of its response.

Bellis                     Expires 6 June 2024                  [Page 4]
Internet-Draft             DNS Multiple QTYPEs             December 2023

   A negative answer is therefore indicated by the combination of the
   presence of a QTn value in the Multiple QTYPE Option and the absence
   of a matching record in the Answer Section.  This is necessary (in
   the absence of DNSSEC) to differentiate between absence of the record
   from the zone and absence of the record from the response.

   A server that is authoritative for the specified QNAME on receipt of
   a Multiple QTYPE Option MUST attempt to return all specified RR types
   except where that would result in truncation in which case it may
   omit some (or all) of the records for the additional RR types.  Those
   RR types MUST then also be omitted from the Multiple QTYPE Option in
   the response.

   A caching recursive server receiving a Multiple QTYPE Option SHOULD
   attempt to fill its positive and negative caches with all of the
   specified RR types before returning its response to the client.

   TODO: is there a case for mandatory answers, i.e. the client saying I
   _really_ want all these?

3.2.2.  Client Side Processing

   Recursive resolvers MAY use this method to obtain multiple records
   from an authoritative server.  For the purposes of Section 5.4.1 of
   [RFC2181] any authoritative answers received MUST be ranked the same
   as the answer for the primary question.

3.2.3.  DNSSEC

   If the DNS client sets the "DNSSEC OK" (DO) bit in the query then the
   server MUST also return the related DNSSEC records that would have
   been returned in a standalone query for the same QTYPE.

   A negative answer from a signed zone MUST contain the appropriate
   authenticated denial of existence records, per [RFC4034] and
   [RFC5155].

   In a signed zone there is a theoretical risk of valid signatures for
   one RR type and invalid signatures for another.  This is the only
   case known to the author where the response code for any particular
   QNAME may be inconsistent across different RR types.

   Should a validating resolver produce NOERROR for some RR types and
   SERVFAIL for others it MUST omit the RR types that failed to validate
   from its response and from the QTn fields on the Multiple QTYPE
   option.  The client MAY then initiate standalone queries for those RR
   types.

Bellis                     Expires 6 June 2024                  [Page 5]
Internet-Draft             DNS Multiple QTYPEs             December 2023

4.  Security Considerations

   The method documented here does not change any of the security
   properties of the DNS protocol itself.

   It should however be noted that this method does increase the
   potential amplification factor when the DNS protocol is used as a
   vector for a denial of service attack.

5.  IANA Considerations

   IANA is requested to assign a new value in the DNS EDNS0 Option Codes
   registry.

6.  Acknowledgements

   The author wishes to thank the following for their feedback and
   reviews during the initial development of this document: Michael
   Graff, Olafur Gudmundsson, Matthijs Mekking, Paul Vixie.

7.  References

7.1.  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>.

   [RFC2181]  Elz, R. and R. Bush, "Clarifications to the DNS
              Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997,
              <https://www.rfc-editor.org/info/rfc2181>.

   [RFC4034]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Resource Records for the DNS Security Extensions",
              RFC 4034, DOI 10.17487/RFC4034, March 2005,
              <https://www.rfc-editor.org/info/rfc4034>.

   [RFC5155]  Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS
              Security (DNSSEC) Hashed Authenticated Denial of
              Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008,
              <https://www.rfc-editor.org/info/rfc5155>.

Bellis                     Expires 6 June 2024                  [Page 6]
Internet-Draft             DNS Multiple QTYPEs             December 2023

   [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>.

   [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>.

7.2.  Informative References

   [RFC3425]  Lawrence, D., "Obsoleting IQUERY", RFC 3425,
              DOI 10.17487/RFC3425, November 2002,
              <https://www.rfc-editor.org/info/rfc3425>.

Author's Address

   Ray Bellis
   Internet Systems Consortium, Inc.
   PO Box 360
   Newmarket,  NH 03857
   United States of America
   Phone: +1 650 423 1300
   Email: ray@isc.org

Bellis                     Expires 6 June 2024                  [Page 7]