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SPF IPv6 nit: A and MX mechanisms

2004-01-09 10:51:27
The `mx' and `a' mechanisms use A records to match the connecting host.
There's no IPv6 equivalent that uses AAAA, because these SPF methods permit
a CIDR length with the assumption that the host lookup is IPv4.  (Such
netmasks would be improper for an IPv6 address found via AAAA.)

I recommend adding equivalent but separate mechanisms `a6' and `mx6' which
use AAAA records rather than A.  By keeping them separate, this allows `a6'
and `mx6' to have IPv6-sized prefix lengths.

Yes, this means two sets of entries even if you do something like
"mx:foo.bar.com mx6:foo.bar.com", but otherwise the `a' and `mx' mechanisms
would need to be contorted somehow to avoid confusing an IPv4 netmask as an
IPv6 netmask.

-- 
-- Todd Vierling <tv(_at_)duh(_dot_)org> <tv(_at_)pobox(_dot_)com>

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