Internet DRAFT - draft-boucadair-tcpm-rst-diagnostic-payload
draft-boucadair-tcpm-rst-diagnostic-payload
tcpm M. Boucadair
Internet-Draft Orange
Intended status: Standards Track T. Reddy
Expires: 6 September 2023 Nokia
5 March 2023
TCP RST Diagnostic Payload
draft-boucadair-tcpm-rst-diagnostic-payload-06
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
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 September 2023.
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.
Boucadair & Reddy Expires 6 September 2023 [Page 1]
Internet-Draft RST Diagnostic Payload March 2023
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. RST Diagnostic Payload . . . . . . . . . . . . . . . . . . . 3
4. Some Examples . . . . . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5.1. RST Diagnostic Payload CBOR Key Values . . . . . . . . . 6
5.2. New Registry for TCP Failure Causes . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
A TCP connection [RFC9293] 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], or firewall)
for several reasons. Typically, a Network Address Translator (NAT)
function can generate an RST segment to notify the endpoints 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 the 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
[RFC9293] for RST segments, especially:
"TCP implementations SHOULD allow a received RST segment to
include data (SHLD-2)."
This document does not change the conditions under which an RST
segment is generated (Section 3.5.2 of [RFC9293]).
Boucadair & Reddy Expires 6 September 2023 [Page 2]
Internet-Draft RST Diagnostic Payload March 2023
The generic procedure for processing an RST segment is specified in
Section 3.5.3 of [RFC9293]. 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.
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.
Preliminary investigation based on some major CGN vendors revealed
that RSTs with data are not discarded and are translated according to
any matching mapping entry.
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
[RFC9293].
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. There is exactly one occurrence.
diagnostic-payload = [magic-cookie, reason]
; Magic cookie to identify a payload that follows this specification
magic-cookie = 12345
; Reset reason details:
reason= {
? reason-code: uint,
? pen:uint,
? reason-description: tstr,
}
Figure 1: Structure of the RST Diagnostic Payload
Boucadair & Reddy Expires 6 September 2023 [Page 3]
Internet-Draft RST Diagnostic Payload March 2023
The RST diagnostic payload comprises a magic cookie 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.
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 MAY be included when
the reason code is not taken from the IANA-maintained registry
(Section 5.2), but from a vendor-specific registry.
reason-description: Includes a brief description of the reset reason
encoded as UTF-8 [RFC3629]. 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 reset reasons.
At least one of "reason-code" and "reason-description" parameters
MUST be included in an RST diagnostic payload. The "pen" parameter
MUST be omitted 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
cookie 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 [RFC9293]. 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.
As per Section 3.6 of [RFC9293], one or more RST segments can be sent
to reset a connection. Whether a TCP endpoint elects to send more
than one RST with only a subset of them that include the diagnostic
payload is implementation specific.
Boucadair & Reddy Expires 6 September 2023 [Page 4]
Internet-Draft RST Diagnostic Payload March 2023
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 the 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 [RFC9293]).
19 3039 # unsigned(12345)
A1 # map(1)
01 # unsigned(1)
02 # unsigned(2)
Figure 2: Example of 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 CBOR diagnostic notation.
[
12345,
{
"reason-code": 2
}
]
Figure 3: Example of an RST Diagnostic Payload with Reason Code
(Diagnostic Notation)
Figure 4 shows an example of an RST diagnostic payload that includes
a free description to report a case that is not covered by an
appropriate code from the IANA-maintained registry (Section 5.2).
[
12345,
{
"reason-description": "brief human-readable description"
}
]
Figure 4: Example of an RST Diagnostic Payload with Reason
Description (Diagnostic Notation)
Boucadair & Reddy Expires 6 September 2023 [Page 5]
Internet-Draft RST Diagnostic Payload March 2023
An RST diagnostic payload may also be sent 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: Example of 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.
[
12345,
{
"reason-code": 1234,
"pen": 32473
}
]
Figure 6: Example of 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 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]).
Boucadair & Reddy Expires 6 September 2023 [Page 6]
Internet-Draft RST Diagnostic Payload March 2023
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]|
+====================+======+===============+==============+
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.
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:
Boucadair & Reddy Expires 6 September 2023 [Page 7]
Internet-Draft RST Diagnostic Payload March 2023
+=======+===================================+=======================+
| Value | Description | Specification (if |
| | | available) |
+=======+===================================+=======================+
| 1 | New data is received | Sections 3.6.1 and |
| | after CLOSE is called | 3.10.7.1 of [RFC9293] |
+-------+-----------------------------------+-----------------------+
| 2 | Received ACK while the | Section 3.10.7.2 of |
| | connection is still in | [RFC9293] |
| | the LISTEN state | |
+-------+-----------------------------------+-----------------------+
| 3 | Illegal Option | Section 3.1 of |
| | | [RFC9293] |
+-------+-----------------------------------+-----------------------+
| 4 | Malformed Message | [ThisDocument] |
+-------+-----------------------------------+-----------------------+
| 5 | Not Authorized | [ThisDocument] |
+-------+-----------------------------------+-----------------------+
| 6 | Resource Exceeded | [ThisDocument] |
+-------+-----------------------------------+-----------------------+
| 7 | Network Failure | [ThisDocument] |
+-------+-----------------------------------+-----------------------+
| 8 | Reset received from | [ThisDocument] |
| | the peer | |
+-------+-----------------------------------+-----------------------+
| 9 | Destination | [ThisDocument] |
| | Unreachable | |
+-------+-----------------------------------+-----------------------+
| 10 | Connection Timeout. | [ThisDocument] |
+-------+-----------------------------------+-----------------------+
| 11 | Too much outstanding | Section 3.6 of |
| | data | [RFC8684] |
+-------+-----------------------------------+-----------------------+
| 12 | Unacceptable | Section 3.6 of |
| | performance | [RFC8684] |
+-------+-----------------------------------+-----------------------+
| 12 | Middlebox interference | Section 3.6 of |
| | | [RFC8684] |
+-------+-----------------------------------+-----------------------+
Table 1: Initial TCP Failure Causes
Note that codes in the 6-10 range can be used by service functions
such as translators.
Boucadair & Reddy Expires 6 September 2023 [Page 8]
Internet-Draft RST Diagnostic Payload March 2023
6. Security Considerations
[RFC9293] discusses TCP-related security considerations. In
particular, RST-specific attacks and their mitigations are discussed
in Section 3.10.7.3 of [RFC9293].
In addition to these considerations, it is RECOMMENDED to control the
size of acceptable diagnostic payload and keep it as brief as
possible. The RECOMMENDED acceptable maximum size of the RST
diagnostic payload is 255 octets.
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 "reason-description" string, when present, should not include any
private information that an observer would not otherwise have access
to.
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.
The reason description, when present, is not intended to be displayed
to end users, but to be consumed by applications. Such a description
may carry a malicious message to mislead the end-user.
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 Shallow for the comments.
8. References
8.1. Normative References
[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>.
Boucadair & Reddy Expires 6 September 2023 [Page 9]
Internet-Draft RST Diagnostic Payload March 2023
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <https://www.rfc-editor.org/info/rfc3629>.
[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>.
[RFC8684] Ford, A., Raiciu, C., Handley, M., Bonaventure, O., and C.
Paasch, "TCP Extensions for Multipath Operation with
Multiple Addresses", RFC 8684, DOI 10.17487/RFC8684, March
2020, <https://www.rfc-editor.org/info/rfc8684>.
[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>.
[RFC9293] Eddy, W., Ed., "Transmission Control Protocol (TCP)",
STD 7, RFC 9293, DOI 10.17487/RFC9293, August 2022,
<https://www.rfc-editor.org/info/rfc9293>.
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>.
Boucadair & Reddy Expires 6 September 2023 [Page 10]
Internet-Draft RST Diagnostic Payload March 2023
[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>.
Authors' Addresses
Mohamed Boucadair
Orange
35000 Rennes
France
Email: mohamed.boucadair@orange.com
Tirumaleswar Reddy
Nokia
India
Email: kondtir@gmail.com
Boucadair & Reddy Expires 6 September 2023 [Page 11]
