QUIC Address Discovery
draft-ietf-quic-address-discovery-01

QUIC                                                          M. Seemann
Internet-Draft                                                          
Intended status: Standards Track                              C. Huitema
Expires: 16 February 2027                           Private Octopus Inc.
                                                          15 August 2026

                         QUIC Address Discovery
                  draft-ietf-quic-address-discovery-01

Abstract

   Unless they have out-of-band knowledge, QUIC endpoints have no
   information about their network situation.  They neither know their
   external IP address and port, nor do they know if they are directly
   connected to the internet or if they are behind a NAT.  This QUIC
   extension allows nodes to determine their reflexive IP address and
   port for any QUIC path.

About This Document

   This note is to be removed before publishing as an RFC.

   The latest revision of this draft can be found at
   https://quicwg.github.io/address-discovery/draft-ietf-quic-address-
   discovery.html.  Status information for this document may be found at
   https://datatracker.ietf.org/doc/draft-ietf-quic-address-discovery/.

   Discussion of this document takes place on the QUIC Working Group
   mailing list (mailto:quic@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/quic/.  Subscribe at
   https://www.ietf.org/mailman/listinfo/quic/.

   Source for this draft and an issue tracker can be found at
   https://github.com/quicwg/address-discovery.

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/.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   3
   3.  Negotiating Extension Use . . . . . . . . . . . . . . . . . .   3
   4.  Frames  . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  OBSERVED_ADDRESS  . . . . . . . . . . . . . . . . . . . .   4
   5.  Address Discovery . . . . . . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
     6.1.  On the Requester Side . . . . . . . . . . . . . . . . . .   5
     6.2.  On the Responder Side . . . . . . . . . . . . . . . . . .   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   STUN ([RFC8489]) allows nodes to discover their reflexive transport
   address by asking a remote server to report the observed source
   address.  While the QUIC ([RFC9000]) packet header was designed to
   allow demultiplexing from STUN packets, moving address discovery into
   the QUIC layer has a number of advantages:

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   1.  STUN encryption relies on shared keys, which have to be
       provisioned.  Absent such provisioning, STUN traffic is
       unencrypted QUIC provides encryption by default, using TLS 1.3.

   2.  When unencrypted, STUN traffic can be observed and modified by
       on-path observers.  By moving address discovery into QUIC's
       encrypted envelope it becomes invisible to observers.

   3.  STUN packet format is designed to facilitate multiplexing STUN
       and other protocols on the same IP address and port number (see
       [RFC7983]).  That property can be used by observers to detect use
       of STUN and infer use of peer-to-peer communications.  In
       contrast, address discovery using QUIC does not "stick out".

   4.  When located behind a load balancer, QUIC packets may be routed
       based on the QUIC connection ID.  Depending on the architecture,
       not using STUN might simplify the routing logic.

   5.  If QUIC traffic doesn't need to be demultiplexed from STUN
       traffic, implementations can enable QUIC bit greasing
       ([RFC9287]).

2.  Conventions and Definitions

   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.

3.  Negotiating Extension Use

   Endpoints advertise their support of the extension by sending the
   address_discovery (0x9f81a176) transport parameter (Section 7.4 of
   [RFC9000]) with a variable-length integer value.  The value
   determines the behavior with respect to address discovery:

   *  0: The node is willing to provide address observations to its
      peer, but is not interested in receiving address observations
      itself.

   *  1: The node is interested in receiving address observations, but
      it is not willing to provide address observations.

   *  2: The node is interested in receiving address observations, and
      it is willing to provide address observations.

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   Implementations that understand this transport parameter MUST treat
   the receipt of any other value than these as a connection error of
   type TRANSPORT_PARAMETER_ERROR.

   When using 0-RTT, both endpoints MUST remember the value of this
   transport parameter.  This allows sending the frame defined by this
   extension in 0-RTT packets.  If 0-RTT data is accepted by the server,
   the server MUST NOT disable this extension or change the value on the
   resumed connection.

4.  Frames

   This extension defines the OBSERVED_ADDRESS frame.

4.1.  OBSERVED_ADDRESS

   OBSERVED_ADDRESS Frame {
       Type (i) = 0x9f81a6..0x9f81a7,
       Sequence Number (i),
       [ IPv4 (32) ],
       [ IPv6 (128) ],
       Port (16),
   }

   The OBSERVED_ADDRESS frame contains the following fields:

   Sequence Number:  A variable-length integer specifying the sequence
      number assigned for this OBSERVED_ADDRESS frame.  The sequence
      number MUST be monotonically increasing for OBSERVED_ADDRESS
      frames in the same connection.  Frames may be received out of
      order.  A peer SHOULD ignore an incoming OBSERVED_ADDRESS frame if
      it previously received another OBSERVED_ADDRESS frame for the same
      path with a Sequence Number equal to or higher than the sequence
      number of the incoming frame.

   IPv4:  The IPv4 address.  Only present if the least significant bit
      of the frame type is 0.

   IPv6:  The IPv6 address.  Only present if the least significant bit
      of the frame type is 1.

   Port:  The port number, in network byte order.

   This frame MUST only appear in the application data packet number
   space.  It is a "probing frame" as defined in Section 9.1 of
   [RFC9000].  OBSERVED_ADDRESS frames are ack-eliciting, and SHOULD be
   retransmitted if lost.  Retransmissions MUST happen on the same path
   as the original frame was sent on.

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   An endpoint MUST NOT send an OBSERVED_ADDRESS frame to a node that
   did not request the receipt of address observations as described in
   Section 3.  A node that did not request the receipt of address
   observations MUST close the connection with a PROTOCOL_VIOLATION
   error if it receives an OBSERVED_ADDRESS frame.

5.  Address Discovery

   An endpoint that negotiated (see Section 3) this extension and
   offered to provide address observations to the peer MUST send an
   OBSERVED_ADDRESS frame on every new path.  This also applies to the
   path used for the QUIC handshake.  The OBSERVED_ADDRESS frame SHOULD
   be sent as early as possible.

   For paths used after completion of the handshake, endpoints SHOULD
   bundle the OBSERVED_ADDRESS frame with probing packets.  This is
   possible, since the frame is defined to be a probing frame
   (Section 8.2 of [RFC9000]).

   Additionally, the sender SHOULD send an OBSERVED_ADDRESS frame when
   it detects a change in the remote address on an existing path.  This
   could be indicative of a NAT rebinding.  However, the sender MAY
   limit the rate at which OBSERVED_ADDRESS frames are produced, to
   mitigate the spoofed packets attack described in Section 6.2.

6.  Security Considerations

6.1.  On the Requester Side

   In general, nodes cannot be trusted to report the correct address in
   OBSERVED_ADDRESS frames.  If possible, endpoints might decide to only
   request address observations when connecting to trusted peers, or if
   that is not possible, define some validation logic (e.g. by asking
   multiple untrusted peers and observing if the responses are
   consistent).  This logic is out of scope for this document.

6.2.  On the Responder Side

   Depending on the routing setup, a node might not be able to observe
   the peer's reflexive transport address, and attempts to do so might
   reveal details about the internal network.  In these cases, the node
   SHOULD NOT offer to provide address observations.

   On-path attackers could capture packets sent from the requester to
   the responder, and resend them from a spoofed source address.  If
   done repeatedly, these spoofed packets could trigger the sending of a
   large number of OBSERVED_ADDRESS frames.  The recommendation to only
   include OBSERVED_ADDRESS frames in packets sent on the same path over

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   which the address was observed ensures that the peer will not receive
   the OBSERVED_ADDRESS frames if the addresses are not valid, but this
   does not reduce the number of packets sent over the network.  The
   attack also has the effect of causing spurious detection of NAT
   rebinding, and is a variant of the replacement of addresses of
   packets mentioned in Section 21.1.1.3 of [RFC9000].  QUIC
   implementations are expected to have sufficient protection against
   spurious NAT rebinding to limit the incidental traffic caused by such
   attacks.  The same protection logic SHOULD be used to prevent sending
   of a large number of spurious OBSERVED_ADDRESS frames.

7.  IANA Considerations

   TODO: fill out registration request for the transport parameter and
   frame types

8.  References

8.1.  Normative References

   [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/rfc/rfc2119>.

   [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/rfc/rfc8174>.

   [RFC8489]  Petit-Huguenin, M., Salgueiro, G., Rosenberg, J., Wing,
              D., Mahy, R., and P. Matthews, "Session Traversal
              Utilities for NAT (STUN)", RFC 8489, DOI 10.17487/RFC8489,
              February 2020, <https://www.rfc-editor.org/rfc/rfc8489>.

   [RFC9000]  Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", RFC 9000,
              DOI 10.17487/RFC9000, May 2021,
              <https://www.rfc-editor.org/rfc/rfc9000>.

8.2.  Informative References

   [I-D.pauly-quic-address-extension]
              Pauly, T., Wood, C. A., and E. Kinnear, "QUIC Address
              Extension", Work in Progress, Internet-Draft, draft-pauly-
              quic-address-extension-00, 11 March 2019,
              <https://datatracker.ietf.org/doc/html/draft-pauly-quic-
              address-extension-00>.

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   [RFC7983]  Petit-Huguenin, M. and G. Salgueiro, "Multiplexing Scheme
              Updates for Secure Real-time Transport Protocol (SRTP)
              Extension for Datagram Transport Layer Security (DTLS)",
              RFC 7983, DOI 10.17487/RFC7983, September 2016,
              <https://www.rfc-editor.org/rfc/rfc7983>.

   [RFC9287]  Thomson, M., "Greasing the QUIC Bit", RFC 9287,
              DOI 10.17487/RFC9287, August 2022,
              <https://www.rfc-editor.org/rfc/rfc9287>.

Acknowledgments

   Unbeknownst to the authors, the idea of moving address discovery into
   QUIC was conceived of before in [I-D.pauly-quic-address-extension].

Authors' Addresses

   Marten Seemann
   Email: martenseemann@gmail.com

   Christian Huitema
   Private Octopus Inc.
   Email: huitema@huitema.net

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