The ip64 module lets an IPv6 Contiki network be connected to an IPv4
network without any additional configuration or outside software. The
ip64 module runs on the RPL root node and translates outgoing IPv6
packets into IPv4 packets nd incoming IPv4 packets to IPv6 packets.
The ip64 module uses stateful NAT64 (RFC6164) to do the packet
translation and DNS64 (RFC6147) to catch DNS requests for IPv6
addresses, turn them into requests for IPv4 addresses, and turn the
replies into responses for IPv6 addresses. This allows devices on the
inside IPv6 network to connect to named servers on the outside IPv4
network.
The ip64 module hooks into the IPv6 stack via a fallback
interface. Any packet that can not be routed into the local RPL mesh
will be sent over the fallback interface, where ip64 picks it up,
translates it into an IPv4 packet, and sends it over its outgoing
interface.
In addition to providing NAT64 and DNS64 services, the ip64 module
also performs DHCPv4 to request IPv4 address for devices connected to
a medium such as Ethernet. The ip64 module also performs ARP
processing to communicate over the Ethernet.
The ip64 module uses a configuration file called ip64-conf.h that
specifies what device to use for the IPv4 network. This file is
intended to be placed in the platform directory. An example
configuration file called ip64-conf-example.h is provided in this
directory.