Re: SIIT/NAT64 is similar to RSIP

[Jun-ichiro itojun Hagino <itojun@iijlab.net>]

>>SIIT/NAT64 environment
>>
>>FTP client
>>========== AF_INET6 API
>>IPv6 only kernel		SIIT box	IPv4 FTP server
>>  |				 |   |		  |a.b.c.d
>>==+==============================+= =+============+==
>>	IPv6 traffic			IPv4 traffic
>>	(::ffff:a.b.c.d)

>I think I now understand your problem.
>What you say is true if and only if the ftp client has internal
>knowledge that ::ffff:a.b.c.d is a special address that is in fact an 
>IPv4 address.
>That is, FTP looks at it in a sockaddr_in/AF_INET and not a 
>sockaddr_in6/ AF_INET6
>structure.

	the internal knowledge is vital for SIIT/NAT64 to work.  it is
	not avoidable.

>This does not have to be the case. Remove that knowledge from the 
>application/kernel
>and then you do not need anymore PORT/PASV.

	if you remove the knowledge, FTP client on IPv6-only machine cannot
	transfer files from/to IPv4 FTP server (since IPv4 FTP server does not
	understand EPSV/EPRT, with protocol #2).

itojun