IPv4->6 application shim library

[Nick Sayer]

It's come to the point now that, applications willing, it is possible to 
configure a network without IPv4 and still experience the Internet fully 
(you do this with the Trick-or-Treat DNS proxy and a NAT/PT gateway like 
faith/faithd).

The only problem with this schema is that all of your applications have 
to be aware of IPv4.

My idea is an LD_PRELOAD shim that will transparently "massage" IPv4 apps.

It replaces gethostbyname() and gethostbyaddr(). It looks for IPv6 
addresses for the names presented and keeps a list in memory. It returns 
a phony IPv4 address that can be used later to find the IPv6 host 
desired. socket also gets intercepted and changes AF_INET to AF_?INET6, 
and connect changes the ersatz IPv4 sockaddr into the real IPv6 one 
before calling the real connect.

I'm writing to see if anyone has any comments on this idea, or perhaps 
someone has already done this...?