On 2019-02-24 15:01, Jeremy Harris wrote:

> On 24/02/2019 07:47, Ian Zimmerman via Exim-dev wrote:
> > 
> > How are the IPv4-mapped IPv6 addresses written in Exim?
> > 
> > The straight translation to dots instead of colons would be ambiguous,
> > wouldn't it?   Say, ..ffff.1.2.3.4 could mean either the mapped address
> > or the normal IPv6 address 0:0:0:ffff:0001:0002:0003:0004 .
> 
> You can write them either way; both are acceptable and the number-base
> of the dotted-portion gets translated ( .234 does _not_ become :0234 ).

But that was not the question I asked.  It's not about one address
having multiple representations; it's that -- after a blind colon-dot
transliteration -- the same string representation may denote multiple
addresses.

> But that's ipv6 addresses given to exim, not how they are given to
> the place you're coding.  I think you need to check, given that a
> colon-to-dot translation has been done by the time it hits you.

Of course, that is why I'm asking.

> I'd expect conversion to unabbreviated form to have been done too.

Do you mean I can expect an IPv6 address (mapped or not) to have exactly
7 separators, whatever these might be?  If yes, there is no ambiguity.

I think I must keep in mind 2 cases:

1. Addresses coming from exim itself, for example $sender_host_address.
Unfortunately the spec doesn't say what format this is in (if it is
IPv6).  Can you enlighten me about this?

2. Addresses explicitly written into the configuration by user.  This
one is about what I can require from users.  I need to document that in
the experimental documentation file.

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