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Cargo.toml
 
 
README.md
 
 
main.rs
 
 
nat64.toml
 
 
IPv6 to IPv4 network address translation example Overview Running the application Explanation 6-to-4 translation 4-to-6 translation

README.md

IPv6 to IPv4 network address translation example

NAT64 is a network address translation gateway that facilitates communitcation between a host on an IPv6 network to another host on an IPv4 network. This example is a simplified implementation of such gateway that can forward TCP traffic between the two networks. Non-TCP or fragmented TCP packets are dropped by the gateway.

Overview

A simple network topology may consist of a gateway with two interfaces connected to an IPv6 only network and an IPv4 only network, as illustrated by the following figure from IETF RFC 6146.

            +---------------------+         +---------------+
            |IPv6 network         |         |    IPv4       |
            |           |  +-------------+  |  network      |
            |           |--| Name server |--|               |
            |           |  | with DNS64  |  |  +----+       |
            |  +----+   |  +-------------+  |  | H2 |       |
            |  | H1 |---|         |         |  +----+       |
            |  +----+   |      +-------+    |  192.0.2.1    |
            |2001:db8::1|------| NAT64 |----|               |
            |           |      +-------+    |               |
            |           |         |         |               |
            +---------------------+         +---------------+

We will use the well-known prefix 64:ff9b::/96 as defined in IETF RFC 6052 to represent IPv4 addresses to the IPv6 network. Packets from the IPv6 network with a destination address within this prefix are routed to the NAT64 gateway.

The gateway also has the address 203.0.113.1 assigned to it on the IPv4 network.

Running the application

The example is located in the examples/nat64 sub-directory. To run the application,

/examples/nat64$ cargo run -- -f nat64.toml

Explanation

The NAT64 gateway is configured with two ports. eth1 is the port connected to the IPv6 network and eth2 is the port connected to the IPv4 network. Also both ports are assigned the same core, core 1.

[[ports]]
    name = "eth1"
    device = "0000:00:08.0"
    cores = [1]
    rxd = 512
    txd = 512

[[ports]]
    name = "eth2"
    device = "0000:00:09.0"
    cores = [1]
    rxd = 512
    txd = 512

Because they are assigned the same core, we can install pipelines that forward packets received on eth1 through eth2 and eth2 to eth1 by using add_pipeline_to_core.

6-to-4 translation

When the gateway receives an unfragmented IPv6 TCP packet, it will translate the destination address to the IPv4 counterpart by stripping away the 64:ff9b::/96 prefix. The source address will be replaced by the gateway's assigned IPv4 address and the source port will be replaced by a free port on the gateway. This address and port mapping is stored in the global PORT_MAP.

The IPv6 header is removed and replaced by an IPv4 header using the model outlined in IETF RFC 6145.

4-to-6 translation

When the gateway receives an unfragmented IPv4 TCP packet, it will translate the source address to the IPv6 counterpart by adding the 64:ff9b::/96 prefix. The TCP destination port is used as the lookup key to find the mapped destination address and port of the IPv6 host. This mapping is stored in the global ADDR_MAP.

The IPv4 header is removed and replaced by an IPv6 header using the model outlined in IETF RFC 6145.