| known problems/assumptions: | |
| - does not handle protocols other than ICMP, UDP, TCP and GRE | |
| - assumes the handset has its own (routed) /64 ipv6 subnet | |
| - assumes the /128 ipv6 subnet it generates can use the nat64 gateway | |
| - assumes the nat64 gateway has the ipv4 address in the last 32 bits of the ipv6 address (that it uses a /96 plat subnet) |