tcpm                                                        M. Boucadair
Internet-Draft                                                    Orange
Intended status: Standards Track                            4 April 2022
Expires: 6 October 2022


                       TCP RST Diagnostic Payload
             draft-boucadair-tcpm-rst-diagnostic-payload-02

Abstract

   This document specifies a diagnostic payload format to be returned in
   TCP RST segments.  Such payloads are used to share with the endpoints
   the reasons for which a TCP connection has been reset.  This is meant
   to ease diagnostic and troubleshooting.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   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 October 2022.

Copyright Notice

   Copyright (c) 2022 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
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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Revised BSD License.





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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  RST Diagnostic Payload  . . . . . . . . . . . . . . . . . . .   3
   4.  Some Examples . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     5.1.  RST Diagnostic Payload CBOR Key Values  . . . . . . . . .   6
     5.2.  New Registry for TCP Failure Causes . . . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   A TCP connection [I-D.ietf-tcpm-rfc793bis] can be reset by a peer for
   various reasons, e.g., received data does not correspond to an active
   connection.  Also, a TCP connection can be reset by an on-path
   service function (e.g., CGN [RFC6888], NAT64 [RFC6146], firewall) for
   several reasons.  Typically, a NAT function can generate an RST
   segment to notify the peers upon the expiry of the lifetime of the
   corresponding mapping entry or because an RST segment was received
   from a peer (Section 2.2 of [RFC7857]).  A TCP connection can also be
   closed by a user or an application at any time.  However, the peer
   that receives an RST segment does not have any hint about the reason
   that led to terminating the connection.  Likewise, the application
   that relies upon such a TCP connection may not easily identify the
   reason for a connection closure.  Troubleshooting such events at the
   remote side of the connection that receives the RST segment may not
   be trivial.

   This document fills this void by specifying a format of the
   diagnostic payload that is returned in an RST segment.  Returning
   such data is consistent with the provision in Section 3.5.3 of
   [I-D.ietf-tcpm-rfc793bis] for RST segments.

   This document does not change the conditions under which an RST
   segment is generated (Section 3.5.2 of [I-D.ietf-tcpm-rfc793bis]).

   The generic procedure for processing an RST segment is specified in
   Section 3.5.3 of [I-D.ietf-tcpm-rfc793bis].  Only the deviations from
   that procedure to insert and validate an enclosed diagnostic payload
   is provided in Section 3.  Section 4 provides a set of examples to
   illustrate the use of TCP RST diagnostic payloads.




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   This document specifies the format and the overall approach to ease
   maintaining the list of codes while allowing for adding new codes as
   needed in the future and accommodating any existing vendor-specific
   codes.  An initial version of error codes is available in Table 1.
   However, the authoritative source to retrieve the full list of error
   codes is the IANA-maintained registry Section 5.2.

2.  Terminology

   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.

   This document makes use of the terms defined in Section 4 of
   [I-D.ietf-tcpm-rfc793bis].

3.  RST Diagnostic Payload

   The RST diagnostic payload MUST be encoded using Concise Binary
   Object Representation (CBOR) Sequence [RFC8742].  The Concise Data
   Definition Language (CDDL) [RFC8610] for the diagnostic payload is as
   follows:

      ; This defines an array, the elements of which are to be used
      ; in a CBOR Sequence:
      diagnostic-payload = [magic-word, reason]
      ; Magic word to identify a payload that follows this specification
      magic-word = 12345
      ; Reset reason details:
      reason= {
        ? reason-code: uint,
        ? pen:uint,
        ? reason-description: tstr,
      }

             Figure 1: Structure of the RST Diagnostic Payload

   The RST diagnostic payload comprises a magic word that is used to
   unambiguously identify an RST payload that follows this
   specification.  It MUST be set to the RFC number to be assigned to
   this document.

      Note to the RFC Editor: Please replace "12345" with the RFC number
      assigned to this document.





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   All parameters in the reason component of an RST diagnostic payload
   are mapped to their CBOR key values as specified in Section 5.1.  The
   description of these parameters is as follows:

   reason-code:  This parameter takes a value from an available registry
      such as the "TCP Failure Causes" registry (Section 5.2).

   pen:  Includes a Private Enterprise Number
      [Private-Enterprise-Numbers].  This parameter is included when the
      reason code is not taken from the IANA-maintained registry
      (Section 5.2), but from a vendor-specific registry.

   reason-description:  It includes a brief description of the reset
      reason.  This parameter SHOULD NOT be included if a reason code is
      supplied.  This parameter is useful only for reset reasons that
      are not yet registered or for application-specific reasons.

   At least one of "reason-code" and "reason-description" parameters
   MUST be included in an RST diagnostic payload.  It is RECOMMENDED to
   omit "pen" if a reason code from the IANA-maintained registry
   (Section 5.2) fits the reset case.

   Malformed RST diagnostic payload messages that include the magic
   number MUST be silently ignored by the receiver.

   A peer that receives a valid diagnostic payload may pass the reset
   reason information to the local application in addition to the
   information (MUST-12) described in Section 3.6 of
   [I-D.ietf-tcpm-rfc793bis].  That information may also be logged
   locally, unless a local policy specifies otherwise.  How the
   information is passed to an application and how it is stored locally
   is implementation specific.

4.  Some Examples

   To ease readability, the CBOR diagnostic notation (Section 8 of
   [RFC8949]) with the parameter names rather than their CBOR key values
   in Section 5.1 is used in Figures 3, 4, 5, and 6.

   Figure 2 depicts an example of RST diagnostic payload that is
   generated to inform the peer that the TCP connection is reset because
   an ACK was received from that peer while the connection is still in
   the LISTEN state (Section 3.10.7.2 of [I-D.ietf-tcpm-rfc793bis]).

   19 3039 # unsigned(12345)
   A1    # map(1)
      01 # unsigned(1)
      02 # unsigned(2)



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    Figure 2: An RST Diagnostic Payload with Reason Code (CBOR Encoding)

   Figure 3 depicts the same RST diagnostic payload as the one shown in
   Figure 2 but following the diagnostic notation.

   [
     12345,
     {
       "reason-code": 2
     }
   ]

      Figure 3: An RST Diagnostic Payload with Reason Code (Diagnostic
                                 Notation)

   Figure 4 shows an example of RST diagnostic payload that includes a
   free description to report a case that is not covered yet by the
   IANA-maintained registry (Section 5.2).

   [
     12345,
     {
       "reason-description": "brief human-readable description"
     }
   ]

        Figure 4: An RST Diagnostic Payload with Reason Description
                           (Diagnostic Notation)

   An RST diagnostic payload may also be reset by an on-path service
   function.  For example, the following diagnostic payload is returned
   by a NAT upon expiry of the mapping entry to which the TCP connection
   is bound (Figure 5).

   [
     12345,
     {
       "reason-code": 8
     }
   ]

      Figure 5: An RST Diagnostic Payload to Report Connection Timeout
                           (Diagnostic Notation)

   Figure 6 illustrates the RST diagnostic payload that is returned by a
   peer that resets a TCP connection for a reason code 1234 defined by a
   vendor with the private enterprise number 32473.




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   [
     12345,
     {
       "reason-code": 1234,
       "pen": 32473
     }
   ]

       Figure 6: An RST Diagnostic Payload to Report Vendor-Specific
                     Reason Code (Diagnostic Notation)

   Figure 6 uses the Enterprise Number 32473 defined for documentation
   use [RFC5612].

5.  IANA Considerations


5.1.  RST Diagnostic Payload CBOR Key Values

   IANA is requested to create a new subregistry titled "RST Diagnostic
   Payload CBOR Key Values" under the "Transmission Control Protocol
   (TCP) Parameters" registry [IANA-TCP].

   The structure of this subregistry and the initial values are provided
   below:

       +--------------------+------+---------------+--------------+
       | Parameter Name     | CBOR | CBOR Major    | Reference    |
       |                    | Key  |    Type &     |              |
       |                    |      | Information   |              |
       +====================+======+===============+==============+
       | reason-code        |   1  | 0 unsigned    |[ThisDocument]|
       | pen                |   2  | 0 unsigned    |[ThisDocument]|
       | reason-description |   3  | 3 text string |[ThisDocument]|
       +====================+======+===============+==============+

   The key value MUST be an integer in the 1-255 range.

   The assignment policy for this registry is "IETF Review" (Section 4.8
   of [RFC8126]).

5.2.  New Registry for TCP Failure Causes

   This document requests IANA to create a new subregistry entitled "TCP
   Failure Causes" under the "Transmission Control Protocol (TCP)
   Parameters" registry [IANA-TCP].

   Values are taken from the 1-65535 range.



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   The assignment policy for this registry is "Expert Review"
   (Section 4.5 of [RFC8126]).

   The designated experts may approve registration once they checked
   that the new requested code is not covered by an existing code and if
   the provided reasoning to register the new code is acceptable.  A
   registration request may supply a pointer to a specification where
   that code is defined.  However, a registration may be accepted even
   if no permanent and readily available public specification is
   available.

   The registry is initially populated with the following values:







































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   +=======+===============================+===========================+
   | Value | Description                   | Specification (if         |
   |       |                               | available)                |
   +=======+===============================+===========================+
   | 1     | Data lost.  New data is       | Sections 3.6.1 and        |
   |       | received after CLOSE is       | 3.10.7.1 of               |
   |       | called                        | [I-D.ietf-tcpm-rfc793bis] |
   +-------+-------------------------------+---------------------------+
   | 2     | Still in LISTEN.              | Section 3.10.7.2 of       |
   |       | Received ACK while the        | [I-D.ietf-tcpm-rfc793bis] |
   |       | connection still in the       |                           |
   |       | LISTEN state                  |                           |
   +-------+-------------------------------+---------------------------+
   | 3     | Malformed Message             | [ThisDocument]            |
   +-------+-------------------------------+---------------------------+
   | 4     | Not Authorized                | [ThisDocument]            |
   +-------+-------------------------------+---------------------------+
   | 5     | Resource Exceeded             | [ThisDocument]            |
   +-------+-------------------------------+---------------------------+
   | 6     | Network Failure.  This        | [ThisDocument]            |
   |       | code can be used by           |                           |
   |       | service functions such        |                           |
   |       | as translators.               |                           |
   +-------+-------------------------------+---------------------------+
   | 7     | Connection Reset              | [ThisDocument]            |
   |       | received from the peer.       |                           |
   |       | This code can be used         |                           |
   |       | by service functions          |                           |
   |       | such as translators.          |                           |
   +-------+-------------------------------+---------------------------+
   | 8     | Destination                   | [ThisDocument]            |
   |       | Unreachable.  This code       |                           |
   |       | can be used by service        |                           |
   |       | functions such as             |                           |
   |       | translators.                  |                           |
   +-------+-------------------------------+---------------------------+
   | 9     | Connection Timeout.           | [ThisDocument]            |
   |       | This code can be used         |                           |
   |       | by service functions          |                           |
   |       | such as translators.          |                           |
   +-------+-------------------------------+---------------------------+

                    Table 1: Initial TCP Failure Causes








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6.  Security Considerations

   [I-D.ietf-tcpm-rfc793bis] discusses TCP-related security
   considerations.  RST-specific attacks and their mitigations are
   discussed in Section 3.10.7.3 of [I-D.ietf-tcpm-rfc793bis].

   In addition to these considerations, it is RECOMMENDED to control the
   size of acceptable diagnostic payload and keep it as brief as
   possible.  Also, it is RECOMMENDED to avoid leaking privacy-related
   information as part of the diagnostic payload (e.g., including a
   description such as "user X resets explicitly the connection" is not
   recommended).

7.  Acknowledgements

   The "diagnostic payload" name is inspired by Section 5.5.2 of
   [RFC7252] that was cited by Carsten Bormann in the tcpm mailing list.

   Thanks to Jon Jon Shallow for the comments.

8.  References

8.1.  Normative References

   [I-D.ietf-tcpm-rfc793bis]
              Eddy, W. M., "Transmission Control Protocol (TCP)
              Specification", Work in Progress, Internet-Draft, draft-
              ietf-tcpm-rfc793bis-28, 7 March 2022,
              <https://www.ietf.org/archive/id/draft-ietf-tcpm-
              rfc793bis-28.txt>.

   [Private-Enterprise-Numbers]
              "Private Enterprise Numbers", 4 May 2020,
              <https://www.iana.org/assignments/enterprise-numbers>.

   [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>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [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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   [RFC8610]  Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
              Definition Language (CDDL): A Notational Convention to
              Express Concise Binary Object Representation (CBOR) and
              JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
              June 2019, <https://www.rfc-editor.org/info/rfc8610>.

   [RFC8742]  Bormann, C., "Concise Binary Object Representation (CBOR)
              Sequences", RFC 8742, DOI 10.17487/RFC8742, February 2020,
              <https://www.rfc-editor.org/info/rfc8742>.

   [RFC8949]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", STD 94, RFC 8949,
              DOI 10.17487/RFC8949, December 2020,
              <https://www.rfc-editor.org/info/rfc8949>.

8.2.  Informative References

   [IANA-TCP] IANA YANG, "Transmission Control Protocol (TCP)
              Parameters",
              <https://www.iana.org/assignments/tcp-parameters/tcp-
              parameters.xhtml>.

   [RFC5612]  Eronen, P. and D. Harrington, "Enterprise Number for
              Documentation Use", RFC 5612, DOI 10.17487/RFC5612, August
              2009, <https://www.rfc-editor.org/info/rfc5612>.

   [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
              NAT64: Network Address and Protocol Translation from IPv6
              Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
              April 2011, <https://www.rfc-editor.org/info/rfc6146>.

   [RFC6888]  Perreault, S., Ed., Yamagata, I., Miyakawa, S., Nakagawa,
              A., and H. Ashida, "Common Requirements for Carrier-Grade
              NATs (CGNs)", BCP 127, RFC 6888, DOI 10.17487/RFC6888,
              April 2013, <https://www.rfc-editor.org/info/rfc6888>.

   [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>.

   [RFC7857]  Penno, R., Perreault, S., Boucadair, M., Ed., Sivakumar,
              S., and K. Naito, "Updates to Network Address Translation
              (NAT) Behavioral Requirements", BCP 127, RFC 7857,
              DOI 10.17487/RFC7857, April 2016,
              <https://www.rfc-editor.org/info/rfc7857>.





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Author's Address

   Mohamed Boucadair
   Orange
   35000 Rennes
   France
   Email: mohamed.boucadair@orange.com












































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