TCP RST Diagnostic Payload
draft-boucadair-tcpm-rst-diagnostic-payload-03
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| Author | Mohamed Boucadair | ||
| Last updated | 2022-04-12 (Latest revision 2022-04-04) | ||
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draft-boucadair-tcpm-rst-diagnostic-payload-03
tcpm M. Boucadair
Internet-Draft Orange
Intended status: Standards Track 12 April 2022
Expires: 14 October 2022
TCP RST Diagnostic Payload
draft-boucadair-tcpm-rst-diagnostic-payload-03
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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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 14 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
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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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).
The presence of vendor-specific reason codes (Section 3) may be used
to fingerprint hosts. Such a concern does not apply if the reason
codes are taken from the IANA-maintained registry. Implementers are,
thus, encouraged to register new codes within IANA instead of
maintaining specific registries.
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>.
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[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>.
[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>.
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[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>.
Author's Address
Mohamed Boucadair
Orange
35000 Rennes
France
Email: mohamed.boucadair@orange.com
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