Implications of Oversized IPv6 Header Chains
RFC 7112

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Internet Engineering Task Force (IETF)                           F. Gont
Request for Comments: 7112                           Huawei Technologies
Updates: 2460                                                  V. Manral
Category: Standards Track                                 Ionos Networks
ISSN: 2070-1721                                                R. Bonica
                                                        Juniper Networks
                                                            January 2014

              Implications of Oversized IPv6 Header Chains

Abstract

   The IPv6 specification allows IPv6 Header Chains of an arbitrary
   size.  The specification also allows options that can, in turn,
   extend each of the headers.  In those scenarios in which the IPv6
   Header Chain or options are unusually long and packets are
   fragmented, or scenarios in which the fragment size is very small,
   the First Fragment of a packet may fail to include the entire IPv6
   Header Chain.  This document discusses the interoperability and
   security problems of such traffic, and updates RFC 2460 such that the
   First Fragment of a packet is required to contain the entire IPv6
   Header Chain.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7112.

Gont, et al.                 Standards Track                    [Page 1]
RFC 7112         Implications of Oversized Header Chains    January 2014

Copyright Notice

   Copyright (c) 2014 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
   (http://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 Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................2
   2. Requirements Language ...........................................3
   3. Terminology .....................................................3
   4. Motivation ......................................................4
   5. Updates to RFC 2460 .............................................5
   6. IANA Considerations .............................................5
   7. Security Considerations .........................................6
   8. Acknowledgements ................................................6
   9. References ......................................................7
      9.1. Normative References .......................................7
      9.2. Informative References .....................................7

1.  Introduction

   With IPv6, optional internet-layer information is carried in one or
   more IPv6 Extension Headers [RFC2460].  Extension Headers are placed
   between the IPv6 header and the Upper-Layer Header in a packet.  The
   term "Header Chain" refers collectively to the IPv6 header, Extension
   Headers, and Upper-Layer Header occurring in a packet.  In those
   scenarios in which the IPv6 Header Chain is unusually long and
   packets are fragmented, or scenarios in which the fragment size is
   very small, the Header Chain may span multiple fragments.

   While IPv4 had a fixed maximum length for the set of all IPv4 options
   present in a single IPv4 packet, IPv6 does not have any equivalent
   maximum limit at present.  This document updates the set of IPv6
   specifications to create an overall limit on the size of the
   combination of IPv6 options and IPv6 Extension Headers that is
   allowed in a single IPv6 packet.  Namely, it updates RFC 2460 such
   that the First Fragment of a fragmented datagram is required to
   contain the entire IPv6 Header Chain.

Gont, et al.                 Standards Track                    [Page 2]
RFC 7112         Implications of Oversized Header Chains    January 2014

   It should be noted that this requirement does not preclude the use of
   large payloads but, instead, merely requires that all headers,
   starting from the IPv6 base header and continuing up to the Upper-
   Layer Header (e.g., TCP or the like) be present in the First