TCP relay(2)

Precondition
IPv6 site has also small number of IPv4 addresses
Both fake DNS and TCP relay are dual stack
A special prefix is installed on them statically

Connection from v6.com to v4.org
v6.com asks faked DNS to resolve AAAA record of v4.org
Faked DNS asks DNS to resolve A record of v4.org
DNS returns 1.2.3.4
Faked DNS embeds 1.2.3.4 into special prefix and tells v6.com it
v6.com tries to make a TCP/IPv6 connection to prefix::1.2.3.4
TCP relay catches the connection
TCP relay also makes a TCP/IPv4 connection to 1.2.3.4