[Mimedefang] [Patch] relay_is_* not ipv6 friendly

David F. Skoll dfs at roaringpenguin.com
Tue Feb 2 13:01:49 EST 2010

Michiel Brandenburg wrote:

> Is that a good approach btw ? Ipv6 mapped ipv4 address are ipv6 not ipv4
> addresses in the strictest terms, no?

In what way are they not?

In other words, what is the difference between an SMTP client coming
from "::ffff:" or "" ?

I made the C code recognize mapped IPv4 addresses and convert them to
plain IPv4 addresses to simplify the filter code.  If you get an IPv4
address, fine... you can handle it.  Similarly, if you get an IPv6
address, you don't need to worry about the (IMO hackish and ugly)
IPv4-mapped special case.

> Say you are on a ipv4 only network you would never receive those
> addresses while if you are on a ipv6 only network all of a sudden you
> might get data from an ipv4 address (but you are ipv6 only), that might
> throw a spanner in the works.

How so?

> For checking RBL lists it might be interesting to check both the ipv4
> and the ipv6 variant of the same address.  But to do that you would need
> the ipv6 variant :), dunno if it's worth changing or how much would
> break if it were changed.

I doubt any RBL would list the IPv6-variant without also listing the
IPv4 variant.



More information about the MIMEDefang mailing list