Network Working Group T. Hain Internet-Draft Cisco Systems Intended status: Standards Track Oct 15, 2010 Expires: April 18, 2011 IPv6 Reverse Path Forwarding ICMP error message draft-hain-ipv6-rpf-icmp-00 Abstract This document specifies an icmp error message for use when the IPv6 source address has failed a reverse-path-forwarding (RPF) check. The draft is being discussed on the ipv6@ietf.org list. Legal This documents and the information contained therein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION THEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 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 http://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 April 18, 2011. Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. Hain Expires April 18, 2011 [Page 1] Internet-Draft IPv6 RPF ICMP Oct 2010 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. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Hain Expires April 18, 2011 [Page 2] Internet-Draft IPv6 RPF ICMP Oct 2010 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.2. ReversePathForwarding ICMP Error Message . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 7. Pending comments . . . . . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6 Hain Expires April 18, 2011 [Page 3] Internet-Draft IPv6 RPF ICMP Oct 2010 1. Introduction A form of ingress traffic filtering commonly known as reverse path forwarding check is discussed in RFC 2827 [RFC2827]While the specific discussion in that document is focused on protecting against source address spoofing attacks by silently dropping the packets, there are instances when multi-homed IPv6 nodes have a mismatch between the source address and the selected path where the desired action SHOULD be to inform and provide a hint. This document defines an icmp error message to inform a source that the packet is being dropped because the source address used would not work as a destination for packets returning over this path. To avoid the situation where this informational back channel could be used as a denial of service attack, these icmp error messages MUST be rate limited. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 3. Mechanisms 3.1. Overview 3.2. ReversePathForwarding ICMP Error Message Informing the origin that the source prefix is not appropriate for the next hop as a symmetric return path. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Prefix Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | Source Prefix for this Path | + + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MAC-type | MAC-length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Hain Expires April 18, 2011 [Page 4] Internet-Draft IPv6 RPF ICMP Oct 2010 | | + + | Message Authentication Code | + + | | + + IPv6 Fields: Destination Address Copied from the Source Address field of the invoking packet. ICMPv6 Fields: Type ???? --- 6 Code 0 - unsigned 1 - signed Reserved 32-bit reserved field. Initialized to zero for transmission; ignored on reception. MAC-type 0 - unused 1 - HMAC-SHA1 2 - AES-CMAC ... MAC-length Length of the message authentication option MAC Value of the message authenticator The optional authentication covers the source and destination address of this specific packet exchange, plus the return-via address. 4. IANA Considerations This specification registers an IPv6 ICMP error message type 5. Security Considerations The IPv6 ICMP RPF-error messages represents a potential denial of service attack vector, and therefore these messages MUST be rate limited by receivers. Hain Expires April 18, 2011 [Page 5] Internet-Draft IPv6 RPF ICMP Oct 2010 6. Acknowledgements The general need for some way to inform multi-homed IPv6 nodes about an RPF check failure has been discussed in multiple sessions at IETF 77 and 78. 7. Pending comments 8. References 8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 8.2. Informative References [RFC2827] Abley, J., "Deprecation of Type 0 Routing Headers in IPv6", RFC 5095, December 2007. Author's Address Tony Hain Cisco Systems 500 108th Ave NE Bellevue, WA 98004 USA Phone: +1 425 468-1061 Email: alh-ietf@tndh.net Hain Expires April 18, 2011 [Page 6]