Re: ocean: do not boil

[itojun@iijlab.net]

>Now the dual-stack problem: with NAT-PT, dual-stack will always be forced
>to use a IPv6-mapped address (translation path) that the DNS-ALG
>synthesized for a v4 destination. dual-stack could very well use IPv4 to
>talk to the destination, but is forced to use IPv6+NAT-PT because of
>DNS-ALG's current behavior. this is assuming dual-stack is sending AAAA
>first, and then A; but not true for other cases.

	site -> outside:
	- if the site uses private IPv4 addrss and IPv4 NAT, it doesn't really
	  matter if we use NAT-PT or IPv4 NAT.
	within site
	- DNS-ALG needs to be clever when returning synthesized AAAA address
	  for NAT-PT.  for instance, DNS-ALG could do the following when asked
	  for AAAA of foo.example.com:
		query AAAA for foo.example.com - it's not there
		query A for foo.example.com - it should be there (X)
		if X is within the site, return empty answer section with
			NOERROR (indicate that foo.example.com does not have
			AAAA, and invite client to use IPv4)
		if X is outside the site, return synthesized AAAA record
			for NAT-PT translation.

itojun