On Sat, Mar 14, 2015 at 3:29 AM, Sam Varshavchik <mr...@courier-mta.com>
wrote:
> Lindsay Haisley writes:
>
> > 3: Patch doesn't support IPv6. Which reminds me that I need to write
>> > some code to fix other IPv6 handling deficiencies with smtpaccess.
>>
>> That's very true. A couple of points on this, as regards ratelimit.py.
>> Courier on my servers is IPv6 enabled, and addresses are posted to the
>> log in the form "::ffff:a.b.c.d", a hybrid notation which I think is
>> deprecated at this point, although it works.
>>
>
> RFC 4291 documents this notation in section 2.2; it's from 2006. Section
> 2.2 is also referenced from RFC 6052, in 2010.
The notation used is, as I understand it, a consequence of IPv4-mapped IPv6
addresses, from this section of RFC 4038's dual stack handling:
Most implementations of dual stack allow IPv6-only applications to
interoperate with both IPv4 and IPv6 nodes. IPv4 packets going to
IPv6 applications on a dual-stack node reach their destination
because their addresses are mapped by using IPv4-mapped IPv6
addresses: the IPv6 address ::FFFF:x.y.z.w represents the IPv4
address x.y.z.w.
I wouldn't call it a hybrid notation per se.
If Courier had been using IPv4 APIs for the IPv4 stack, then it would be
natural to skip the ::FFFF:, but as I understand Sam, Courier is using the
IPv6 APIs also for IPv4.
--
Cheers,
Jan
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