6MAN B. Carpenter Internet-Draft Univ. of Auckland Obsoletes: 6874 (if approved) R. Hinden Updates: 7622, 8089 (if approved) Check Point Software Intended status: Standards Track 8 September 2024 Expires: 12 March 2025 Entering IPv6 Zone Identifiers in User Interfaces draft-ietf-6man-zone-ui-03 Abstract This document describes how the zone identifier of an IPv6 scoped address, defined in the IPv6 Scoped Address Architecture (RFC 4007), should be entered into a user interface. It obsoletes RFC 6874 and updates RFC 7622 and RFC 8089. Discussion Venue This note is to be removed before publishing as an RFC. Discussion of this document takes place on the 6MAN mailing list (ipv6@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/ipv6/ (https://mailarchive.ietf.org/arch/browse/ipv6/). 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 12 March 2025. Copyright Notice Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved. Carpenter & Hinden Expires 12 March 2025 [Page 1] Internet-Draft IPv6 Zone IDs in UIs September 2024 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Open Issue . . . . . . . . . . . . . . . . . . . . . . . 5 2. Normative Terminology . . . . . . . . . . . . . . . . . . . . 5 3. Specification . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 6.1. Normative References . . . . . . . . . . . . . . . . . . 7 6.2. Informative References . . . . . . . . . . . . . . . . . 7 Appendix A. Change log . . . . . . . . . . . . . . . . . . . . . 9 Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction A number of software tools require or permit the user to enter an IPv6 address via a user interface (UI). The standard literal text format for an IPv6 address is defined by [RFC4291] and [RFC5952]. The IPv6 Scoped Address Architecture specification [RFC4007] extends the text representation of limited-scope IPv6 addresses, in particular link-local unicast addresses and multicast addresses with less than global scope, such that a zone identifier may be concatenated to an address, for purposes described in that specification. Note that RFC 5952 does not mention this extension. Zone identifiers are especially useful in contexts in which literal addresses are typically used, for example during fault diagnosis or device configuration, when it may be essential to specify which interface is used for sending to a link-local address. It should be noted that zone identifiers have purely local meaning within the node in which they are defined, usually being the same as IPv6 interface names. They are completely meaningless for any other node. Today, they are meaningful only when attached to link-local unicast and scoped multicast addresses, but it is possible that other uses might be defined in the future. Carpenter & Hinden Expires 12 March 2025 [Page 2] Internet-Draft IPv6 Zone IDs in UIs September 2024 Examples of a link-local unicast address qualified by a zone identifier are "fe80::1234%eth0" on a Linux host, or "fe80::4321%7" on a Windows host. Such addresses are directly supported by socket API calls including "getaddrinfo()" [RFC3493]. Devices whose network stack does not support the RFC 4007 model of a human-readable zone identifier are out of scope for this document. Some examples of use cases for entering such an address in a UI are as follows: 1. A software tool may be used for simple debugging actions involving link-local addresses on a host with more than one active link interface. For example, the functioning of an interface and the existence of a device may today be checked via "ping fe80::1234%eth0". If this succeeds, the user learns that the remote device is reachable via the interface named "eth0". 2. A software tool must sometimes be used to configure or reconfigure a device which only has a link-local address, again in a host with more than one active link interface. For example, a typical home router may today be configured via "192.168.178.1" but not via "fe80::1%eth0", if the tool in use does not support the input of zone identifiers. 3. Using a monitoring tool such as Wireshark, the user may need to specify a given link-local address on a given interface whose traffic is of interest. (At the time of writing, Wireshark supports capture from multiple interfaces, but does not appear to support the zone identifier in a display filter.) 4. The Microsoft Web Services for Devices (WSD) virtual printer port mechanism can present the user with an IPv6 link-local address such as "fe80::823b:f9ff:fe7b:d9dc%10" in which the zone identifier is present, but is not recognized by appropriate software. 5. The National Marine Electronics Association (NMEA) has recently defined the "OneNet Marine IPv6 Ethernet Networking Standard" [ONE-NET], which uses IPv6 link local addresses exclusively. Desired improvements to the standard include a web page for device configuration using link-local addresses. Such requirements have already spawned hacks to work around current limitations, e.g., [LL-HACK]. Carpenter & Hinden Expires 12 March 2025 [Page 3] Internet-Draft IPv6 Zone IDs in UIs September 2024 For all such use cases, it is highly desirable that a complete IPv6 link-local address can be cut and pasted from one UI (such as the output from a system command) to another. Since such addresses may include quite long hexadecimal strings, for example "fe80::8d0f:7f26:f5c8:780b%enx525400d5e0fb", any solution except cut- and-paste is highly error prone. The use cases listed above apply to relatively simple actions on end systems. The zone identifiers that can be used are limited by the host operating system, since RFC 4007 only specifies that they are coded in ASCII, without specifying a maximum length. It should be noted that whereas some operating systems and network APIs support a default zone identifier as recommended by RFC 4007, others, including Linux, do not, and for them a solution is particularly important, since a link-local address without a zone index cannot be used in the Linux socket API. The RFC 4007 model assumes that the human-readable zone identifier is mapped by the operating system into a numeric interface index. Typically this mapping is performed by the socket API, e.g. by "getaddrinfo()". The mapping between the human-readable zone identifier string and the numeric value is a host-specific function that varies between operating systems. The present document is concerned only with the human-readable string that is typically displayed in an operating system's user interface. However, in most operating systems it is possible to use the underlying interface number, represented as a decimal integer, as an equivalent to the human-readable string. This is recommended by Section 11.2 of RFC 4007, but not required. This possibility does not affect the UI requirement given below. As IPv6 deployment becomes more widespread, the lack of a solution for handling complete link-local addresses in all tools is becoming an acute problem for increasing numbers of operational and support personnel. It will become critical as IPv6-only or IPv6-mostly networks [RFC8925] [I-D.link-v6ops-6mops], with nodes lacking native IPv4 support, appear. For example, the NMEA use case mentioned above is an immediate requirement. This is the principal reason for documenting this requirement now. Carpenter & Hinden Expires 12 March 2025 [Page 4] Internet-Draft IPv6 Zone IDs in UIs September 2024 This document obsoletes [RFC6874], which implementors of web browsers have determined is impracticable to support [I-D.schinazi-httpbis-link-local-uri-bcp], and replaces it by a generic UI requirement described below. Note that obsoleting RFC 6874 reverts the change that it made to the URI syntax defined by [RFC3986], so RFC 3986 is no longer updated by RFC 6874. This document also updates [RFC7622] and [RFC8089] by deleting their references to RFC 6874. 1.1. Open Issue This section is to be removed before publishing as an RFC. This document effectively extends RFC 4007. Should this be recorded as a formal update to RFC 4007? 2. Normative 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 [BCP14] when, and only when, they appear in all capitals, as shown here. 3. Specification A user interface (UI) that allows or requires the user to enter an IPv6 address *SHOULD* provide a means for entering a link-local address or a scoped multicast address and selecting a zone identifer as specified by [RFC4007] (typically, an interface identifier as defined by the operating system). Ideally, the UI will support the complete format specified by RFC 4007 (e.g., "fe80::1%eth0"). If this is impossible for practical reasons, the UI could support an alternative delimiter in place of "%". The hyphen ("-") is suggested (e.g., "fe80::1-eth0"). If this too is impossible for practical reasons, the UI could support two separate input fields (e.g., "fe80::1" in one box, "eth0" in another), or selection from a list of active zone identifiers. Carpenter & Hinden Expires 12 March 2025 [Page 5] Internet-Draft IPv6 Zone IDs in UIs September 2024 The program providing the UI will then store the address and the zone identifier, converting the latter to an interface index (typically via the socket API). A faulty zone identifier will be detected when attempting to convert it and this should be reported to the user as an error. The resulting interface index will be used for any subsequent socket calls using the link-local address. Note that an address string such as "fe80::1%eth0" cannot be converted to binary by the POSIX socket API function "inet_pton()". It must either be converted using "getaddrinfo()", or by splitting it into two strings and using "inet_pton()" and "if_nametoindex()" successively, in order to obtain the required interface index value. In this model, the zone identifier is considered independently of the IPv6 address itself. However, this does not in itself resolve the difficulties in considering the zone identifier as part of the HTTP origin model [RFC6454]. Therefore, this approach does not resolve the issue of how browsers should support link-local addresses, discussed further in [I-D.schinazi-httpbis-link-local-uri-bcp]. Because of this, the recommendations and normative statements in this document do not apply to web browsers. 4. Security Considerations As explained in [RFC4007], zone identifiers are of local significance and must not be sent on the wire. In particular, see the final security consideration of RFC 4007, which indicates that software should not trust packets that contain textual non-global addresses as data. Software that obtains a zone identifier through a UI should therefore not transmit it further. There is no formal limit on the length of the zone identifier string in RFC 4007. A UI implementation should apply a reasonable length limit when inputting a zone identifier, in order to minimize the risk of a buffer overrun. For example, a limit to 16 ASCII characters would correspond to the existing limit on Linux interface names. RFC 4007 does not specify the character set allowed in a zone identifier. An implementation should not allow ASCII NULL characters in a zone identifier string as this could cause inconsistencies in subsequent string processing. 5. IANA Considerations This document makes no request of IANA. 6. References Carpenter & Hinden Expires 12 March 2025 [Page 6] Internet-Draft IPv6 Zone IDs in UIs September 2024 6.1. Normative References [BCP14] Best Current Practice 14, . At the time of writing, this BCP comprises the following: Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC4007] Deering, S., Haberman, B., Jinmei, T., Nordmark, E., and B. Zill, "IPv6 Scoped Address Architecture", RFC 4007, DOI 10.17487/RFC4007, March 2005, . [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2006, . [RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6 Address Text Representation", RFC 5952, DOI 10.17487/RFC5952, August 2010, . 6.2. Informative References [I-D.ietf-6man-rfc6874bis] Carpenter, B. E., Cheshire, S., and R. M. Hinden, "Representing IPv6 Zone Identifiers in Address Literals and Uniform Resource Identifiers", Work in Progress, Internet-Draft, draft-ietf-6man-rfc6874bis-09, 2 July 2023, . [I-D.link-v6ops-6mops] Linkova, J. and N. Buraglio, "IPv6-Mostly Networks: Deployment and Operations Considerations", Work in Progress, Internet-Draft, draft-link-v6ops-6mops-01, 7 July 2024, . Carpenter & Hinden Expires 12 March 2025 [Page 7] Internet-Draft IPv6 Zone IDs in UIs September 2024 [I-D.schinazi-httpbis-link-local-uri-bcp] Schinazi, D., "Best Practices for Link-Local Connectivity in URI-Based Protocols", Work in Progress, Internet-Draft, draft-schinazi-httpbis-link-local-uri-bcp-03, 22 February 2024, . [LL-HACK] Jin, P., "Snippets: IPv6 link-local connect hack", 2021, . [ONE-NET] NMEA, "The OneNet Standard for IP Networking of Marine Electronic Devices", 2023, . [RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W. Stevens, "Basic Socket Interface Extensions for IPv6", RFC 3493, DOI 10.17487/RFC3493, February 2003, . [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005, . [RFC6454] Barth, A., "The Web Origin Concept", RFC 6454, DOI 10.17487/RFC6454, December 2011, . [RFC6874] Carpenter, B., Cheshire, S., and R. Hinden, "Representing IPv6 Zone Identifiers in Address Literals and Uniform Resource Identifiers", RFC 6874, DOI 10.17487/RFC6874, February 2013, . [RFC7622] Saint-Andre, P., "Extensible Messaging and Presence Protocol (XMPP): Address Format", RFC 7622, DOI 10.17487/RFC7622, September 2015, . [RFC8089] Kerwin, M., "The "file" URI Scheme", RFC 8089, DOI 10.17487/RFC8089, February 2017, . [RFC8925] Colitti, L., Linkova, J., Richardson, M., and T. Mrugalski, "IPv6-Only Preferred Option for DHCPv4", RFC 8925, DOI 10.17487/RFC8925, October 2020, . Carpenter & Hinden Expires 12 March 2025 [Page 8] Internet-Draft IPv6 Zone IDs in UIs September 2024 Appendix A. Change log This section is to be removed before publishing as an RFC. * draft-carpenter-6man-zone-ui-00, 2024-01-15: - Initial version * draft-carpenter-6man-zone-ui-01, 2024-02-17: - Weakened use of normative keywords to allow flexibility * draft-carpenter-6man-zone-ui-02, 2024-02-21: - Note that RFC 6874 was found unimplementable. - Note that HTTP "origin" issues are not resolved. - Cite new httpbis draft. - Open issue: Updates: 4007 ? * draft-carpenter-6man-zone-ui-03, 2024-03-01: - Small clarifications. - Updated some references. * draft-carpenter-6man-zone-ui-04, 2024-04-01: - Mentioned scoped multicast addresses. - Mentioned inet_pton() issue. - Added reference. * draft-ietf-6man-zone-ui-00, 2024-06-28: - Adopted by WG. - Clarified inapplicability to browsers. * draft-ietf-6man-zone-ui-01, 2024-08-05: - Clarified extensions of RFC 4007. - Clarified relationship with RFC 5952 Carpenter & Hinden Expires 12 March 2025 [Page 9] Internet-Draft IPv6 Zone IDs in UIs September 2024 * draft-ietf-6man-zone-ui-02, 2024-09-05: - Clarified non-impact on URI syntax. * draft-ietf-6man-zone-ui-03, 2024-09-09: - Update RFC 7622 and RFC 8089 to remove citations of RFC 6874. - Explicit mention of cancelled update to RFC 3986. Appendix B. Acknowledgements This document owes a lot to the previous discussions that led to RFC 6874 and to the abandoned draft [I-D.ietf-6man-rfc6874bis]. Useful comments were received from Nick Buraglio, Martin J. Dürst, Toerless Eckert, David Farmer, Brian Haberman, Nate Karstens, Jen Linkova, Eduard Metz, Gyan Mishra, Ole Troan, David Schinazi, Michael Sweet, Martin Thomson, Éric Vyncke, and other participants in the 6MAN WG. Authors' Addresses Brian Carpenter School of Computer Science University of Auckland PB 92019 Auckland 1142 New Zealand Email: brian.e.carpenter@gmail.com Robert M. Hinden Check Point Software 959 Skyway Road San Carlos, CA 94070 United States of America Email: bob.hinden@gmail.com Carpenter & Hinden Expires 12 March 2025 [Page 10]