| Internet-Draft | CONNECT-IP Routes | August 2021 |
| Chernyakhovsky, et al. | Expires 28 February 2022 | [Page] |
This document describes an extension to the CONNECT-IP HTTP method. This extension allows both endpoints to negotiate routes. This enables split-tunnel VPN services, and network-to-network VPNs.¶
This note is to be removed before publishing as an RFC.¶
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This document describes an extension to the CONNECT-IP HTTP method [CONNECT-IP]. This extension allows both endpoints to negotiate routes. This enables split-tunnel VPN services, and network-to-network VPNs.¶
CONNECT-IP allows endpoints to set up an IP tunnel between one another but does not allow exchanging which routes are supported though the tunnel. This extension can be used to connect an endpoint or network to another network without changing default routes.¶
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 2.3 of [RFC7230]) between the client and the proxy, those are referred to as "intermediaries" in this document.¶
Endpoints have the ability to advertise and reject routes using the ROUTE_ADVERTISEMENT (Section 3.1) and ROUTE_REJECTION (Section 3.1) capsule. Note that these capsules are purely informational: receipt of a ROUTE_ADVERTISEMENT capsule does not require the recipient to start routing traffic to its peer. Additionally, if an endpoint receives a ROUTE_REJECTION for a given prefix that it had previously received a ROUTE_ADVERTISEMENT capsule for, then the two cancel out and the endpoint MUST remove its state from the ROUTE_ADVERTISEMENT capsule instead of installing new state for the ROUTE_REJECTION capsule. Conversely, the same is true of a ROUTE_ADVERTISEMENT that matches a previous ROUTE_REJECTION. Routes are handled via longest-prefix-first preference, meaning that if a given IP prefix is covered by multiple route advertisement and route rejections, the one with the longest prefix is used.¶
When processing ROUTE_ADVERTISEMENT capsules, endpoints MUST check their local policy before deciding whether to forward packets to their peer. Since ignoring these capsules is allowed by the protocol, such policy decisions will not prevent interoperability.¶
The ROUTE_ADVERTISEMENT capsule allows an endpoint to communicate to its peer that it is willing to route traffic to a given prefix. This indicates that the sender has an existing route to the prefix, and notifies its peer that if the receiver of the ROUTE_ADVERTISEMENT capsule sends IP packets for this prefix in HTTP Datagrams, the sender of the capsule will forward them along its preexisting route. This capsule uses a Capsule Type of 0xfff102. Its value uses the following format:¶
ROUTE_ADVERTISEMENT Capsule {
IP Version (8),
IP Address (32..128),
IP Prefix Length (8),
}
IP Version of this route advertisement. MUST be either 4 or 6.¶
IP address of the advertised route. 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.¶
Length of the IP Prefix of the advertised route, in bits. MUST be lesser or equal to the length of the IP Address field, in bits.¶
Upon receiving the ROUTE_ADVERTISEMENT capsule, an endpoint MAY start routing IP packets in that prefix to its peer.¶
The ROUTE_REJECTION capsule allows an endpoint to communicate to its peer that it is not willing to route traffic to a given prefix. This capsule uses a Capsule Type of 0xfff103. Its value uses the following format:¶
ROUTE_REJECTION Capsule {
IP Version (8),
IP Address (32..128),
IP Prefix Length (8),
}
IP Version of this route rejection. MUST be either 4 or 6.¶
IP address of the rejected route. 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.¶
Length of the IP Prefix of the advertised route, in bits. MUST be lesser or equal to the length of the IP Address field, in bits.¶
Upon receiving the ROUTE_REJECTION capsule, an endpoint MUST stop routing IP packets in that prefix to its peer. Note that this capsule can be reordered with DATAGRAM frames, and therefore an endpoint that receives packets for routes it has rejected MUST NOT treat that as an error.¶
The ROUTE_RESET capsule allows an endpoint to cancel any routes it had previously advertised or denied. This capsule uses a Capsule Type of 0xfff104. Its value uses the following format:¶
ROUTE_RESET Capsule {
}
Upon receiving the ROUTE_RESET capsule, an endpoint MUST stop routing IP packets to its peer. Note that this capsule can be reordered with DATAGRAM frames, and therefore an endpoint that receives packets for routes it has rejected MUST NOT treat that as an error.¶
The main purpose of the ROUTE_RESET capsule is to allow endpoints to not have to remember the full list of routes they have shared with their peer. In practice, it is expected that ROUTE_RESET capsules will be closely followed by ROUTE_ADVERTISEMENT capsules that will refill the routing table that was just cleared.¶
The ATOMIC_START capsule allows an endpoint to create an atomic set of capsules. This capsule uses a Capsule Type of 0xfff106. Its value uses the following format:¶
ATOMIC_START Capsule {
}
Upon receiving an ATOMIC_START capsule, an endpoint MUST buffer all incoming known CONNECT-IP-specific capsules (i.e., capsules defined in this document) until it receives an ATOMIC_END capsule. Endpoints MUST NOT send two ATOMIC_START capsules without an ATOMIC_END capsule between them.¶
Endpoints MUST NOT buffer unknown capsules. Endpoints MAY choose to immediately process IP_PACKET and SHUTDOWN capsules instead of buffering them. Capsules defined in other documents are by default not buffered by ATOMIC_START. Extensions that register new capsule types MAY specify that these capsules should be buffered by ATOMIC_START, and whether it is allowed to skip buffering for them.¶
The purpose of this frame is to avoid timing issues where an endpoint installs a route before an important route rejection was received. Endpoints SHOULD group their initial configuration into an atomic block to allow their peer to mark the tunnel as operational once the whole block is parsed.¶
The ATOMIC_END capsule allows an endpoint to end an atomic set of capsules. This capsule uses a Capsule Type of 0xfff107. Its value uses the following format:¶
ATOMIC_END Capsule {
}
Upon receiving an ATOMIC_END capsule, an endpoint MUST parse all previously buffered capsules, in order of receipt. Endpoints MUST NOT send an ATOMIC_END capsule without a preceding ATOMIC_START capsule.¶
In theory, endpoints could use ROUTE_ADVERTISEMENT capsules to divert traffic from naive endpoints. To avoid this, receivers of ROUTE_ADVERTISEMENT capsules MUST check their local policy before acting on such capsules, see Section 2.¶
This document will request IANA to add the following values to the "HTTP Capsule Types" registry created by [HTTP-DGRAM]:¶
+----------+---------------------+---------------------+---------------+ | Value | Type | Description | Reference | +----------+---------------------+---------------------+---------------+ | 0xfff102 | ROUTE_ADVERTISEMENT | Route Advertisement | This document | | 0xfff103 | ROUTE_REJECTION | Route Rejection | This document | | 0xfff104 | ROUTE_RESET | Route Reset | This document | | 0xfff106 | ATOMIC_START | Atomic Start | This document | | 0xfff107 | ATOMIC_END | Atomic End | This document | +----------+---------------------+---------------------+---------------+¶
In this scenario, the client will typically receive a single IP address that the proxy has picked from a pool of addresses it maintains. The client will route all traffic through the tunnel. The exchange could look as follows:¶
Client Server
ADDRESS_REQUEST -------->
IP Version = 4
IP Address = 0.0.0.0
IP Prefix Length = 0
<-------- ADDRESS_ASSIGN
IP Version = 4
IP Address = 192.0.2.42
IP Prefix Length = 32
<-------- ROUTE_ADVERTISEMENT
IP Version = 4
IP Address = 0.0.0.0
IP Prefix Length = 0
¶
The design of CONNECT-IP was inspired by discussions in the MASQUE working group around [REQS]. The authors would like to thank participants in those discussions for their feedback.¶