tcpm M. Boucadair Internet-Draft Orange Intended status: Standards Track 31 March 2022 Expires: 2 October 2022 TCP RST Diagnostic Paylaod draft-boucadair-tcpm-rst-diagnostic-payload-01 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 2 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/ 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 Expires 2 October 2022 [Page 1] Internet-Draft RST Diagnostic Payload March 2022 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. RST Diagnostic Payload . . . . . . . . . . . . . . . . . . . 3 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 4.1. New Registry for TCP Failure Causes . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 7.1. Normative References . . . . . . . . . . . . . . . . . . 7 7.2. Informative References . . . . . . . . . . . . . . . . . 8 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8 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. The first version of the specification is meant to discuss 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 Boucadair Expires 2 October 2022 [Page 2] Internet-Draft RST Diagnostic Payload March 2022 accommodating any existing vendor-specific codes. An initial version of error codes is available at Table 1. However, the authoritative source to retrieve the full list of error codes is the IANA- maintained registry Section 4.1. 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 In order to unambiguously identify an RST diagnostic payload that is compliant with the present specification, the payload MUST use the I-JSON message format [RFC7493]. The following parameters are defined: rc: Stands for "Reason Code". This parameter takes a value from an available registry such as the "TCP Failure Causes" registry (Section 4.1). pen: Includes a Private Enterprise Number [Private-Enterprise-Numbers]. This attribute is included when the reason code is not taken from the IANA-maintained registry (Section 4.1), but from a vendor-specific registry. rd: Stands for "Reason Description". It includes a brief description of the reason code. This parameter SHOULD NOT be included if a reason code is supplied. This parameter is useful only for codes that are not yet registered or for application- specific codes. At least "rc" and "rd" 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 4.1) fits the reset case. Malformed RST diagnostic payload messages MUST be silently ignored by the receiver. Boucadair Expires 2 October 2022 [Page 3] Internet-Draft RST Diagnostic Payload March 2022 A peer that receives a valid diagnostic payload may pass that 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. Figure 1 depicts an example of an RST diagnostic payload that is generated to inform the peer that the connection is reset because an ACK was received while the connection is still in the LISTEN state. { "rc": 2 } Figure 1: An RST Diagnostic Payload with Reason Code Figure 2 shows an example of an RST diagnostic payload that includes a free description to report a case that is not covered yet by the IANA-maintained registry (Section 4.1). { "rd": "brief human-readable description" } Figure 2: An RST Diagnostic Payload with Reason Description 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 uppon expiry of the mapping entry to which the TCP connection is bound (Figure 3). { "rc": 8 } Figure 3: An RST Diagnostic Payload to Report Connection Timeout Figure 4 illustrates the example of an 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. { "rc": 1234 "pen": 32473 } Figure 4: An RST Diagnostic Payload to Report Vendor-Specific Reason Code Boucadair Expires 2 October 2022 [Page 4] Internet-Draft RST Diagnostic Payload March 2022 Figure 4 uses the Enterprise Number 32473 defined for documentation use [RFC5612]. 4. IANA Considerations 4.1. 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 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 Expires 2 October 2022 [Page 5] Internet-Draft RST Diagnostic Payload March 2022 +=======+===============================+===========================+ | 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.This | [ThisDocument] | | | code can be used by | | | | service functions such | | | | as translators. | | +-------+-------------------------------+---------------------------+ Table 1: Initial TCP Failure Causes Boucadair Expires 2 October 2022 [Page 6] Internet-Draft RST Diagnostic Payload March 2022 5. 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). 6. Acknowledgements TBC. 7. References 7.1. 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, . [Private-Enterprise-Numbers] "Private Enterprise Numbers", 4 May 2020, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC7493] Bray, T., Ed., "The I-JSON Message Format", RFC 7493, DOI 10.17487/RFC7493, March 2015, . [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, . Boucadair Expires 2 October 2022 [Page 7] Internet-Draft RST Diagnostic Payload March 2022 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . 7.2. Informative References [IANA-TCP] IANA YANG, "Transmission Control Protocol (TCP) Parameters", . [RFC5612] Eronen, P. and D. Harrington, "Enterprise Number for Documentation Use", RFC 5612, DOI 10.17487/RFC5612, August 2009, . [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, . [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, . [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, . Author's Address Mohamed Boucadair Orange 35000 Rennes France Email: mohamed.boucadair@orange.com Boucadair Expires 2 October 2022 [Page 8]