Le 2013-04-24 11:54, S Moonesamy a écrit :
Hi Simon,
At 01:31 24-04-2013, Simon Perreault wrote:
I, for one, have no idea what a "client on IPv4-mapped IPv6 address"
might be. So the text doesn't look correct to me.
If you describe in a little bit more detail what the intent is, we can
help you reformulate.
Thanks for feedback.
For context the text is in the ninth paragraph of Section 5 of
draft-ietf-spfbis-4408bis-14. I'll rewrite the text as follows:
SPF implementations on IPv6 servers need to handle both "AAAA" and
"A" DNS records, for SMTP clients on IPv4 mapped IPv6 addresses
[RFC4291].
I'm sorry, I've read section 5 and that still doesn't make sense to me.
The intent seems to be about an IPv4 host (client) connecting to an IPv6
host (server).
How does that work? Is there a NAT46 in between?
The IPv6 host matches the source IP address of the TCP
connection against a list which may contain IPv4 mapped IPv6 addresses.
Does that make sense or it is easier to forget about "IPv4 mapped IPv6
addresses"?
As IPv4-mapped IPv6 addresses do not go on the wire, this still doesn't
make sense to me!
IPv4-mapped IPv6 addresses have two uses:
1) They are used internally on a single host, between a userland app and
the kernel, to represent IPv4 addresses using an IPv6-only socket. The
address never leaves the host. It can be considered an implementation
detail. They are most useful when porting an IPv4-only app to
dual-stack. Newer applications should never use IPv4-mapped IPv6
addresses, and it is good practice to disable them explicitly.
2) In various signalling protocols, to represent an IPv4 address in an
IPv6 address field. This is protocol-specific. It is used only for
signalling, never as actual addresses in IPv6 packet headers.
At this point, I'm guessing that it would be better to forget about
IPv4-mapped IPv6 addresses, although I still don't understand exactly
what your intent is.
Simon
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