IP Proxying Support for HTTP
draft-age-masque-connect-ip-01

Document Type Active Internet-Draft (candidate for masque WG)
Authors Tommy Pauly  , David Schinazi  , Alex Chernyakhovsky  , Mirja K├╝hlewind  , Magnus Westerlund 
Last updated 2021-11-08 (latest revision 2021-10-25)
Replaces draft-tbd-masque-connect-ip-ext-flow, draft-kuehlewind-masque-connect-ip, draft-cms-masque-connect-ip-ext-routes, draft-cms-masque-connect-ip
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MASQUE                                                     T. Pauly, Ed.
Internet-Draft                                                Apple Inc.
Intended status: Standards Track                             D. Schinazi
Expires: 28 April 2022                                 A. Chernyakhovsky
                                                              Google LLC
                                                           M. Kuehlewind
                                                           M. Westerlund
                                                                Ericsson
                                                         25 October 2021

                      IP Proxying Support for HTTP
                     draft-age-masque-connect-ip-01

Abstract

   This document describes a method of proxying IP packets over HTTP.
   This protocol is similar to CONNECT-UDP, but allows transmitting
   arbitrary IP packets, without being limited to just TCP like CONNECT
   or UDP like CONNECT-UDP.

Discussion Venues

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

   Discussion of this document takes place on the Multiplexed
   Application Substrate over QUIC Encryption Working Group mailing list
   (masque@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/masque/.

   Source for this draft and an issue tracker can be found at
   https://github.com/tfpauly/draft-age-masque-connect-ip.

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."

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   This Internet-Draft will expire on 28 April 2022.

Copyright Notice

   Copyright (c) 2021 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 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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   3
   3.  Configuration of Clients  . . . . . . . . . . . . . . . . . .   3
   4.  The CONNECT-IP Protocol . . . . . . . . . . . . . . . . . . .   4
     4.1.  Limiting Request Scope  . . . . . . . . . . . . . . . . .   5
     4.2.  Capsules  . . . . . . . . . . . . . . . . . . . . . . . .   5
       4.2.1.  ADDRESS_ASSIGN Capsule  . . . . . . . . . . . . . . .   6
       4.2.2.  ADDRESS_REQUEST Capsule . . . . . . . . . . . . . . .   7
       4.2.3.  ROUTE_ADVERTISEMENT Capsule . . . . . . . . . . . . .   7
   5.  Transmitting IP Packets using HTTP Datagrams  . . . . . . . .   9
   6.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  10
     6.1.  Remote Access VPN . . . . . . . . . . . . . . . . . . . .  10
     6.2.  IP Flow Forwarding  . . . . . . . . . . . . . . . . . . .  12
     6.3.  Proxied Connection Racing . . . . . . . . . . . . . . . .  15
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
     8.1.  CONNECT-IP HTTP Upgrade Token . . . . . . . . . . . . . .  17
     8.2.  Datagram Format Type  . . . . . . . . . . . . . . . . . .  17
     8.3.  Capsule Type Registrations  . . . . . . . . . . . . . . .  17
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  18
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  19
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  20

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1.  Introduction

   This document describes a method of proxying IP packets over HTTP.
   When using HTTP/2 or HTTP/3, IP proxying uses HTTP Extended CONNECT
   as described in [EXT-CONNECT2] and [EXT-CONNECT3].  When using
   HTTP/1.x, IP proxying uses HTTP Upgrade as defined in Section 7.8 of
   [SEMANTICS].  This protocol is similar to CONNECT-UDP [CONNECT-UDP],
   but allows transmitting arbitrary IP packets, without being limited
   to just TCP like CONNECT [SEMANTICS] or UDP like CONNECT-UDP.

   The HTTP Upgrade Token defined for this mechanism is "connect-ip",
   which is also referred to as CONNECT-IP in this document.

   The CONNECT-IP protocol allows endpoints to set up a tunnel for
   proxying IP packets using an HTTP proxy.  This can be used for
   various solutions that include general-purpose packet tunnelling,
   such as for a point-to-point or point-to-network VPN, or for limited
   forwarding of packets to specific hosts.

   Forwarded IP packets can be sent efficiently via the proxy using HTTP
   Datagram support [HTTP-DGRAM].

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.

   In this document, we use the term "proxy" to refer to the HTTP server
   that responds to the CONNECT-IP request.  If there are HTTP
   intermediaries (as defined in Section 3.7 of [SEMANTICS]) between the
   client and the proxy, those are referred to as "intermediaries" in
   this document.

3.  Configuration of Clients

   Clients are configured to use IP Proxying over HTTP via an URI
   Template [TEMPLATE].  The URI template MAY contain two variables:
   "target" and "ip_proto".  Examples are shown below:

   https://masque.example.org/{target}/{ip_proto}/
   https://proxy.example.org:4443/masque?t={target}&p={ip_proto}
   https://proxy.example.org:4443/masque{?target,ip_proto}
   https://masque.example.org/?user=bob

                      Figure 1: URI Template Examples

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4.  The CONNECT-IP Protocol

   This document defines the "connect-ip" HTTP Upgrade Token. "connect-
   ip" uses the Capsule Protocol as defined in [HTTP-DGRAM].

   When sending its IP proxying request, the client SHALL perform URI
   template expansion to determine the path and query of its request,
   see Section 3.

   When using HTTP/2 or HTTP/3, the following requirements apply to
   requests:

   *  The ":method" pseudo-header field SHALL be set to "CONNECT".

   *  The ":protocol" pseudo-header field SHALL be set to "connect-ip".

   *  The ":authority" pseudo-header field SHALL contain the host and
      port of the proxy, not an individual endpoint with which a
      connection is desired.

   *  The contents of the ":path" pseudo-header SHALL be determined by
      the URI template expansion, see Section 3.  Variables in the URI
      template can determine the scope of the request, such as
      requesting full-tunnel IP packet forwarding, or a specific proxied
      flow, see Section 4.1.

   Along with a request, the client can send a REGISTER_DATAGRAM_CONTEXT
   capsule [HTTP-DGRAM] to negotiate support for sending IP packets in
   HTTP Datagrams (Section 5).

   Any 2xx (Successful) response indicates that the proxy is willing to
   open an IP forwarding tunnel between it and the client.  Any response
   other than a successful response indicates that the tunnel has not
   been formed.

   A proxy MUST NOT send any Transfer-Encoding or Content-Length header
   fields in a 2xx (Successful) response to the IP Proxying request.  A
   client MUST treat a successful response containing any Content-Length
   or Transfer-Encoding header fields as malformed.

   The lifetime of the forwarding tunnel is tied to the CONNECT stream.
   Closing the stream (in HTTP/3 via the FIN bit on a QUIC STREAM frame,
   or a QUIC RESET_STREAM frame) closes the associated forwarding
   tunnel.

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   Along with a successful response, the proxy can send capsules to
   assign addresses and advertise routes to the client (Section 4.2).
   The client can also assign addresses and advertise routes to the
   proxy for network-to-network routing.

4.1.  Limiting Request Scope

   Unlike CONNECT-UDP requests, which require specifying a target host,
   CONNECT-IP requests can allow endpoints to send arbitrary IP packets
   to any host.  The client can choose to restrict a given request to a
   specific host or IP protocol by adding parameters to its request.
   When the server knows that a request is scoped to a target host or
   protocol, it can leverage this information to optimize its resource
   allocation; for example, the server can assign the same public IP
   address to two CONNECT-IP requests that are scoped to different hosts
   and/or different protocols.

   CONNECT-IP uses URI template variables (Section 3) to determine the
   scope of the request for packet proxying.  All variables defined here
   are optional, and have default values if not included.

   The defined variables are:

   target:  The variable "target" contains a hostname or IP address of a
      specific host to which the client wants to proxy packets.  If the
      "target" variable is not specified, the client is requesting to
      communicate with any allowable host.  If the target is an IP
      address, the request will only support a single IP version.  If
      the target is a hostname, the server is expected to perform DNS
      resolution to determine which route(s) to advertise to the client.
      The server SHOULD send a ROUTE_ADVERTISEMENT capsule that includes
      routes for all usable resolved addresses for the requested
      hostname.

   ipproto:  The variable "ipproto" contains an IP protocol number, as
      defined in the "Assigned Internet Protocol Numbers" IANA registry.
      If present, it specifies that a client only wants to proxy a
      specific IP protocol for this request.  If the value is 0, or the
      variable is not included, the client is requesting to use any IP
      protocol.

4.2.  Capsules

   This document defines multiple new capsule types that allow endpoints
   to exchange IP configuration information.  Both endpoints MAY send
   any number of these new capsules.

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4.2.1.  ADDRESS_ASSIGN Capsule

   The ADDRESS_ASSIGN capsule (see Section 8.3 for the value of the
   capsule type) allows an endpoint to inform its peer that it has
   assigned an IP address or prefix to it.  The ADDRESS_ASSIGN capsule
   allows assigning a prefix which can contain multiple addresses.  Any
   of these addresses can be used as the source address on IP packets
   originated by the receiver of this capsule.

   ADDRESS_ASSIGN Capsule {
     Type (i) = ADDRESS_ASSIGN,
     Length (i),
     IP Version (8),
     IP Address (32..128),
     IP Prefix Length (8),
   }

                  Figure 2: ADDRESS_ASSIGN Capsule Format

   IP Version:  IP Version of this address assignment.  MUST be either 4
      or 6.

   IP Address:  Assigned IP address.  If the IP Version field has value
      4, the IP Address field SHALL have a length of 32 bits.  If the IP
      Version field has value 6, the IP Address field SHALL have a
      length of 128 bits.

   IP Prefix Length:  The number of bits in the IP Address that are used
      to define the prefix that is being assigned.  This MUST be less
      than or equal to the length of the IP Address field, in bits.  If
      the prefix length is equal to the length of the IP Address, the
      receiver of this capsule is only allowed to send packets from a
      single source address.  If the prefix length is less than the
      length of the IP address, the receiver of this capsule is allowed
      to send packets from any source address that falls within the
      prefix.

   If an endpoint receives multiple ADDRESS_ASSIGN capsules, all of the
   assigned addresses or prefixes can be used.  For example, multiple
   ADDRESS_ASSIGN capsules are necessary to assign both IPv4 and IPv6
   addresses.

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4.2.2.  ADDRESS_REQUEST Capsule

   The ADDRESS_REQUEST capsule (see Section 8.3 for the value of the
   capsule type) allows an endpoint to request assignment of an IP
   address from its peer.  This capsule is not required for simple
   client/proxy communication where the client only expects to receive
   one address from the proxy.  The capsule allows the endpoint to
   optionally indicate a preference for which address it would get
   assigned.

   ADDRESS_REQUEST Capsule {
     Type (i) = ADDRESS_REQUEST,
     Length (i),
     IP Version (8),
     IP Address (32..128),
     IP Prefix Length (8),
   }

                  Figure 3: ADDRESS_REQUEST Capsule Format

   IP Version:  IP Version of this address request.  MUST be either 4 or
      6.

   IP Address:  Requested IP address.  If the IP Version field has value
      4, the IP Address field SHALL have a length of 32 bits.  If the IP
      Version field has value 6, the IP Address field SHALL have a
      length of 128 bits.

   IP Prefix Length:  Length of the IP Prefix requested, in bits.  MUST
      be lesser or equal to the length of the IP Address field, in bits.

   Upon receiving the ADDRESS_REQUEST capsule, an endpoint SHOULD assign
   an IP address to its peer, and then respond with an ADDRESS_ASSIGN
   capsule to inform the peer of the assignment.

4.2.3.  ROUTE_ADVERTISEMENT Capsule

   The ROUTE_ADVERTISEMENT capsule (see Section 8.3 for the value of the
   capsule type) allows an endpoint to communicate to its peer that it
   is willing to route traffic to a set of IP address ranges.  This
   indicates that the sender has an existing route to each address
   range, and notifies its peer that if the receiver of the
   ROUTE_ADVERTISEMENT capsule sends IP packets for one of these ranges
   in HTTP Datagrams, the sender of the capsule will forward them along
   its preexisting route.  Any address which is in one of the address
   ranges can be used as the destination address on IP packets
   originated by the receiver of this capsule.

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   ROUTE_ADVERTISEMENT Capsule {
     Type (i) = ROUTE_ADVERTISEMENT,
     Length (i),
     IP Address Range (..) ...,
   }

                Figure 4: ROUTE_ADVERTISEMENT Capsule Format

   The ROUTE_ADVERTISEMENT capsule contains a sequence of IP Address
   Ranges.

   IP Address Range {
     IP Version (8),
     Start IP Address (32..128),
     End IP Address (32..128),
     IP Protocol (8),
   }

                     Figure 5: IP Address Range Format

   IP Version:  IP Version of this range.  MUST be either 4 or 6.

   Start IP Address and End IP Address:  Inclusive start and end IP
      address of the advertised range.  If the IP Version field has
      value 4, these fields SHALL have a length of 32 bits.  If the IP
      Version field has value 6, these fields SHALL have a length of 128
      bits.  The Start IP Address MUST be lesser or equal to the End IP
      Address.

   IP Protocol:  The Internet Protocol Number for traffic that can be
      sent to this range.  If the value is 0, all protocols are allowed.

   Upon receiving the ROUTE_ADVERTISEMENT capsule, an endpoint MAY start
   routing IP packets in these ranges to its peer.

   Each ROUTE_ADVERTISEMENT contains the full list of address ranges.
   If multiple ROUTE_ADVERTISEMENT capsules are sent in one direction,
   each ROUTE_ADVERTISEMENT capsule supersedes prior ones.  In other
   words, if a given address range was present in a prior capsule but
   the most recently received ROUTE_ADVERTISEMENT capsule does not
   contain it, the receiver will consider that range withdrawn.

   If multiple ranges using the same IP protocol were to overlap, some
   routing table implementations might reject them.  To prevent overlap,
   the ranges are ordered; this places the burden on the sender and
   makes verification by the receiver much simpler.  If an IP Address
   Range A precedes an IP address range B in the same
   ROUTE_ADVERTISEMENT capsule, they MUST follow these requirements:

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   *  IP Version of A MUST be lesser or equal than IP Version of B

   *  If the IP Version of A and B are equal, the IP Protocol of A MUST
      be lesser or equal than IP Protocol of B.

   *  If the IP Version and IP Protocol of A and B are both equal, the
      End IP Address of A MUST be strictly lesser than the Start IP
      Address of B.

   If an endpoint received a ROUTE_ADVERTISEMENT capsule that does not
   meet these requirements, it MUST abort the stream.

5.  Transmitting IP Packets using HTTP Datagrams

   IP packets are encoded using HTTP Datagrams [HTTP-DGRAM] with the
   IP_PACKET HTTP Datagram Format Type (see value in Section 8.2).  When
   using the IP_PACKET HTTP Datagram Format Type, full IP packets (from
   the IP Version field until the last byte of the IP Payload) are sent
   unmodified in the "HTTP Datagram Payload" field of an HTTP Datagram.

   In order to use HTTP Datagrams, the client will first decide whether
   or not it will attempt to use HTTP Datagram Contexts and then
   register its context ID (or lack thereof) using the corresponding
   registration capsule, see [HTTP-DGRAM].

   When sending a registration capsule using the "Datagram Format Type"
   set to IP_PACKET, the "Datagram Format Additional Data" field SHALL
   be empty.  Servers MUST NOT register contexts using the IP_PACKET
   HTTP Datagram Format Type.  Clients MUST NOT register more than one
   context using the IP_PACKET HTTP Datagram Format Type.  Endpoints
   MUST NOT close contexts using the IP_PACKET HTTP Datagram Format
   Type.  If an endpoint detects a violation of any of these
   requirements, it MUST abort the stream.

   Clients MAY optimistically start sending proxied IP packets before
   receiving the response to its IP proxying request, noting however
   that those may not be processed by the proxy if it responds to the
   request with a failure, or if the datagrams are received by the proxy
   before the request.

   Extensions to this mechanism MAY define new HTTP Datagram Format
   Types in order to use different semantics or encodings for IP
   payloads.  For example, an extension could define a new HTTP Datagram
   Format Type which enables compression of IP header fields.

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   When a CONNECT-IP endpoint receives an HTTP Datagram containing an IP
   packet, it will parse the packet's IP header, perform any local
   policy checks (e.g., source address validation), check their routing
   table to pick an outbound interface, and then send the IP packet on
   that interface.

   In the other direction, when a CONNECT-IP endpoint receives an IP
   packet, it checks to see if the packet matches the routes mapped for
   a CONNECT-IP forwarding tunnel, and performs the same forwarding
   checks as above before transmitting the packet over HTTP Datagrams.

   Note that CONNECT-IP endpoints will decrement the IP Hop Count (or
   TTL) upon encapsulation but not decapsulation.  In other words, the
   Hop Count is decremented right before an IP packet is transmitted in
   an HTTP Datagram.  This prevents infinite loops in the presence of
   routing loops, and matches the choices in IPsec [IPSEC].

   Endpoints MAY implement additional filtering policies on the IP
   packets they forward.

6.  Examples

   CONNECT-IP enables many different use cases that can benefit from IP
   packet proxying and tunnelling.  These examples are provided to help
   illustrate some of the ways in which CONNECT-IP can be used.

6.1.  Remote Access VPN

   The following example shows a point-to-network VPN setup, where a
   client receives a set of local addresses, and can send to any remote
   server through the proxy.  Such VPN setups can be either full-tunnel
   or split-tunnel.

   +--------+ IP A         IP B +--------+              +---> IP D
   |        |-------------------|        | IP C         |
   | Client | IP Subnet C <-> * | Server |--------------+---> IP E
   |        |-------------------|        |              |
   +--------+                   +--------+              +---> IP ...

                         Figure 6: VPN Tunnel Setup

   In this case, the client does not specify any scope in its request.
   The server assigns the client an IPv4 address to the client
   (192.0.2.11) and a full-tunnel route of all IPv4 addresses
   (0.0.0.0/0).  The client can then send to any IPv4 host using a
   source address in its assigned prefix.

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   [[ From Client ]]             [[ From Server ]]

   SETTINGS
   H3_DATAGRAM = 1

                                 SETTINGS
                                 SETTINGS_ENABLE_CONNECT_PROTOCOL = 1
                                 H3_DATAGRAM = 1

   STREAM(44): HEADERS
   :method = CONNECT
   :protocol = connect-ip
   :scheme = https
   :path = /vpn
   :authority = server.example.com

   STREAM(44): CAPSULE
   Capsule Type = REGISTER_DATAGRAM_CONTEXT
   Context ID = 0
   Context Extension = {}

                                 STREAM(44): HEADERS
                                 :status = 200

                                 STREAM(44): CAPSULE
                                 Capsule Type = ADDRESS_ASSIGN
                                 IP Version = 4
                                 IP Address = 192.0.2.11
                                 IP Prefix Length = 32

                                 STREAM(44): CAPSULE
                                 Capsule Type = ROUTE_ADVERTISEMENT
                                 IP Version = 4
                                 Start IP Address = 0.0.0.0
                                 End IP Address = 255.255.255.255
                                 IP Protocol = 0 // Any

   DATAGRAM
   Quarter Stream ID = 11
   Context ID = 0
   Payload = Encapsulated IP Packet

                                 DATAGRAM
                                 Quarter Stream ID = 11
                                 Context ID = 0
                                 Payload = Encapsulated IP Packet

                     Figure 7: VPN Full-Tunnel Example

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   A setup for a split-tunnel VPN (the case where the client can only
   access a specific set of private subnets) is quite similar.  In this
   case, the advertised route is restricted to 192.0.2.0/24, rather than
   0.0.0.0/0.

   [[ From Client ]]             [[ From Server ]]

                                 STREAM(44): CAPSULE
                                 Capsule Type = ADDRESS_ASSIGN
                                 IP Version = 4
                                 IP Address = 192.0.2.42
                                 IP Prefix Length = 32

                                 STREAM(44): CAPSULE
                                 Capsule Type = ROUTE_ADVERTISEMENT
                                 IP Version = 4
                                 Start IP Address = 192.0.2.0
                                 End IP Address = 192.0.2.255
                                 IP Protocol = 0 // Any

                 Figure 8: VPN Split-Tunnel Capsule Example

6.2.  IP Flow Forwarding

   The following example shows an IP flow forwarding setup, where a
   client requests to establish a forwarding tunnel to
   target.example.com using SCTP (IP protocol 132), and receives a
   single local address and remote address it can use for transmitting
   packets.  A similar approach could be used for any other IP protocol
   that isn't easily proxied with existing HTTP methods, such as ICMP,
   ESP, etc.

   +--------+ IP A         IP B +--------+
   |        |-------------------|        | IP C
   | Client |    IP C <-> D     | Server |---------> IP D
   |        |-------------------|        |
   +--------+                   +--------+

                        Figure 9: Proxied Flow Setup

   In this case, the client specfies both a target hostname and an IP
   protocol number in the scope of its request, indicating that it only
   needs to communicate with a single host.  The proxy server is able to
   perform DNS resolution on behalf of the client and allocate a
   specific outbound socket for the client instead of allocating an
   entire IP address to the client.  In this regard, the request is
   similar to a traditional CONNECT proxy request.

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   The server assigns a single IPv6 address to the client
   (2001:db8::1234:1234) and a route to a single IPv6 host
   (2001:db8::3456), scoped to SCTP.  The client can send and recieve
   SCTP IP packets to the remote host.

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   [[ From Client ]]             [[ From Server ]]

   SETTINGS
   H3_DATAGRAM = 1
                                 SETTINGS
                                 SETTINGS_ENABLE_CONNECT_PROTOCOL = 1
                                 H3_DATAGRAM = 1

   STREAM(52): HEADERS
   :method = CONNECT
   :protocol = connect-ip
   :scheme = https
   :path = /proxy?target=target.example.com&ipproto=132
   :authority = server.example.com

   STREAM(52): CAPSULE
   Capsule Type = REGISTER_DATAGRAM_CONTEXT
   Context ID = 0
   Context Extension = {}

                                 STREAM(52): HEADERS
                                 :status = 200

                                 STREAM(52): CAPSULE
                                 Capsule Type = ADDRESS_ASSIGN
                                 IP Version = 6
                                 IP Address = 2001:db8::1234:1234
                                 IP Prefix Length = 128

                                 STREAM(52): CAPSULE
                                 Capsule Type = ROUTE_ADVERTISEMENT
                                 IP Version = 6
                                 Start IP Address = 2001:db8::3456
                                 End IP Address = 2001:db8::3456
                                 IP Protocol = 132

   DATAGRAM
   Quarter Stream ID = 11
   Context ID = 0
   Payload = Encapsulated SCTP/IP Packet

                                 DATAGRAM
                                 Quarter Stream ID = 11
                                 Context ID = 0
                                 Payload = Encapsulated SCTP/IP Packet

                    Figure 10: Proxied SCTP Flow Example

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6.3.  Proxied Connection Racing

   The following example shows a setup where a client is proxying UDP
   packets through a CONNECT-IP proxy in order to control connection
   establishement racing through a proxy, as defined in Happy Eyeballs
   [HEv2].  This example is a variant of the proxied flow, but
   highlights how IP-level proxying can enable new capabilities even for
   TCP and UDP.

   +--------+ IP A         IP B +--------+ IP C
   |        |-------------------|        |<------------> IP E
   | Client |  IP C<->E, D<->F  | Server |
   |        |-------------------|        |<------------> IP F
   +--------+                   +--------+ IP D

                 Figure 11: Proxied Connection Racing Setup

   As with proxied flows, the client specfies both a target hostname and
   an IP protocol number in the scope of its request.  When the proxy
   server performs DNS resolution on behalf of the client, it can send
   the various remote address options to the client as separate routes.
   It can also ensure that the client has both IPv4 and IPv6 addresses
   assigned.

   The server assigns the client both an IPv4 address (192.0.2.3) and an
   IPv6 address (2001:db8::1234:1234) to the client, as well as an IPv4
   route (198.51.100.2) and an IPv6 route (2001:db8::3456), which
   represent the resolved addresses of the target hostname, scoped to
   UDP.  The client can send and recieve UDP IP packets to the either of
   the server addresses to enable Happy Eyeballs through the proxy.

   [[ From Client ]]             [[ From Server ]]

   SETTINGS
   H3_DATAGRAM = 1

                                 SETTINGS
                                 SETTINGS_ENABLE_CONNECT_PROTOCOL = 1
                                 H3_DATAGRAM = 1

   STREAM(44): HEADERS
   :method = CONNECT
   :protocol = connect-ip
   :scheme = https
   :path = /proxy?ipproto=17
   :authority = server.example.com

   STREAM(44): CAPSULE

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   Capsule Type = REGISTER_DATAGRAM_CONTEXT
   Context ID = 0
   Context Extension = {}

                                 STREAM(44): HEADERS
                                 :status = 200

                                 STREAM(44): CAPSULE
                                 Capsule Type = ADDRESS_ASSIGN
                                 IP Version = 4
                                 IP Address = 192.0.2.3
                                 IP Prefix Length = 32

                                 STREAM(44): CAPSULE
                                 Capsule Type = ADDRESS_ASSIGN
                                 IP Version = 6
                                 IP Address = 2001:db8::1234:1234
                                 IP Prefix Length = 128

                                 STREAM(44): CAPSULE
                                 Capsule Type = ROUTE_ADVERTISEMENT
                                 IP Version = 4
                                 Start IP Address = 198.51.100.2
                                 End IP Address = 198.51.100.2
                                 IP Protocol = 17

                                 STREAM(44): CAPSULE
                                 Capsule Type = ROUTE_ADVERTISEMENT
                                 IP Version = 6
                                 Start IP Address = 2001:db8::3456
                                 End IP Address = 2001:db8::3456
                                 IP Protocol = 17
   ...

   DATAGRAM
   Quarter Stream ID = 11
   Context ID = 0
   Payload = Encapsulated IPv6 Packet

   DATAGRAM
   Quarter Stream ID = 11
   Context ID = 0
   Payload = Encapsulated IPv4 Packet

                Figure 12: Proxied Connection Racing Example

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7.  Security Considerations

   There are significant risks in allowing arbitrary clients to
   establish a tunnel to arbitrary servers, as that could allow bad
   actors to send traffic and have it attributed to the proxy.  Proxies
   that support CONNECT-IP SHOULD restrict its use to authenticated
   users.  The HTTP Authorization header [AUTH] MAY be used to
   authenticate clients.  More complex authentication schemes are out of
   scope for this document but can be implemented using CONNECT-IP
   extensions.

   Since CONNECT-IP endpoints can proxy IP packets send by their peer,
   they SHOULD follow the guidance in [BCP38] to help prevent denial of
   service attacks.

8.  IANA Considerations

8.1.  CONNECT-IP HTTP Upgrade Token

   This document will request IANA to register "connect-ip" in the HTTP
   Upgrade Token Registry maintained at
   <https://www.iana.org/assignments/http-upgrade-tokens>.

   Value:  connect-ip

   Description:  The CONNECT-IP Protocol

   Expected Version Tokens:  None

   References:  This document

8.2.  Datagram Format Type

   This document will request IANA to register IP_PACKET in the "HTTP
   Datagram Format Types" registry established by [HTTP-DGRAM].

                 +===========+==========+===============+
                 | Type      | Value    | Specification |
                 +===========+==========+===============+
                 | IP_PACKET | 0xff8b00 | This Document |
                 +-----------+----------+---------------+

                 Table 1: Registered Datagram Format Type

8.3.  Capsule Type Registrations

   This document will request IANA to add the following values to the
   "HTTP Capsule Types" registry created by [HTTP-DGRAM]:

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    +==========+=====================+====================+===========+
    | Value    | Type                | Description        | Reference |
    +==========+=====================+====================+===========+
    | 0xfff100 | ADDRESS_ASSIGN      | Address Assignment | This      |
    |          |                     |                    | Document  |
    +----------+---------------------+--------------------+-----------+
    | 0xfff101 | ADDRESS_REQUEST     | Address Request    | This      |
    |          |                     |                    | Document  |
    +----------+---------------------+--------------------+-----------+
    | 0xfff102 | ROUTE_ADVERTISEMENT | Route              | This      |
    |          |                     | Advertisement      | Document  |
    +----------+---------------------+--------------------+-----------+

                           Table 2: New Capsules

9.  References

9.1.  Normative References

   [BCP38]    Ferguson, P. and D. Senie, "Network Ingress Filtering:
              Defeating Denial of Service Attacks which employ IP Source
              Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827,
              May 2000, <https://www.rfc-editor.org/rfc/rfc2827>.

   [EXT-CONNECT2]
              McManus, P., "Bootstrapping WebSockets with HTTP/2",
              RFC 8441, DOI 10.17487/RFC8441, September 2018,
              <https://www.rfc-editor.org/rfc/rfc8441>.

   [EXT-CONNECT3]
              Hamilton, R., "Bootstrapping WebSockets with HTTP/3", Work
              in Progress, Internet-Draft, draft-ietf-httpbis-h3-
              websockets-00, 9 September 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
              h3-websockets-00>.

   [HTTP-DGRAM]
              Schinazi, D. and L. Pardue, "Using Datagrams with HTTP",
              Work in Progress, Internet-Draft, draft-ietf-masque-h3-
              datagram-04, 6 October 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-masque-
              h3-datagram-04>.

   [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>.

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   [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>.

   [SEMANTICS]
              Fielding, R. T., Nottingham, M., and J. Reschke, "HTTP
              Semantics", Work in Progress, Internet-Draft, draft-ietf-
              httpbis-semantics-19, 12 September 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
              semantics-19>.

   [TEMPLATE] Gregorio, J., Fielding, R., Hadley, M., Nottingham, M.,
              and D. Orchard, "URI Template", RFC 6570,
              DOI 10.17487/RFC6570, March 2012,
              <https://www.rfc-editor.org/rfc/rfc6570>.

9.2.  Informative References

   [AUTH]     Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Authentication", RFC 7235,
              DOI 10.17487/RFC7235, June 2014,
              <https://www.rfc-editor.org/rfc/rfc7235>.

   [CONNECT-UDP]
              Schinazi, D., "UDP Proxying Support for HTTP", Work in
              Progress, Internet-Draft, draft-ietf-masque-connect-udp-
              05, 6 October 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-masque-
              connect-udp-05>.

   [HEv2]     Schinazi, D. and T. Pauly, "Happy Eyeballs Version 2:
              Better Connectivity Using Concurrency", RFC 8305,
              DOI 10.17487/RFC8305, December 2017,
              <https://www.rfc-editor.org/rfc/rfc8305>.

   [IPSEC]    Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <https://www.rfc-editor.org/rfc/rfc4301>.

   [PROXY-REQS]
              Chernyakhovsky, A., McCall, D., and D. Schinazi,
              "Requirements for a MASQUE Protocol to Proxy IP Traffic",
              Work in Progress, Internet-Draft, draft-ietf-masque-ip-
              proxy-reqs-03, 27 August 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-masque-
              ip-proxy-reqs-03>.

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Acknowledgments

   The design of this method was inspired by discussions in the MASQUE
   working group around [PROXY-REQS].  The authors would like to thank
   participants in those discussions for their feedback.

Authors' Addresses

   Tommy Pauly (editor)
   Apple Inc.

   Email: tpauly@apple.com

   David Schinazi
   Google LLC

   Email: dschinazi.ietf@gmail.com

   Alex Chernyakhovsky
   Google LLC

   Email: achernya@google.com

   Mirja Kuehlewind
   Ericsson

   Email: mirja.kuehlewind@ericsson.com

   Magnus Westerlund
   Ericsson

   Email: magnus.westerlund@ericsson.com

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