exim question

Jakob Hirsch jh@plonk.de
Wed Jul 14 11:29:38 UTC 2010


(CCing exim-dev)

Vernon Schryver, 2010-07-13 19:20:
> http://www.merit.edu/mail.archives/nanog/msg10375.html
> seems to imply that exim violates the SMTP standards by generating
> address literals in Received: headers without the required
> "IPv6:" tag.   That NANOG thread seems to say that exim generates
>     Received: from s0.nanog.org (s0.nanog.org [2001:48a8:6880:95::20]) ...
> instead of
>     Received: from s0.nanog.org (s0.nanog.org [IPv6:2001:48a8:6880:95::20]) ...
> Is that true?

uhm... yes, that's true:

Received: from calcite.rhyolite.com ([2001:4978:230::3]:30997)
	by ymmv.de with esmtps (TLSv1:AES256-SHA:256)
	(Exim 4.72)

I (and obviously others) wasn't aware that should be a "IPv6:" prefix.
Which "SMTP standards" say that?

> Should I modify the DCC client programs to recognize IPv6 address
> literals without the "IPv6;" tag?  It would cost some CPU cycles.
> It might be a little dodgy, because except for colons, IPv6 addresses
> can look like host names.

Parsing Received headers is always dodgy, because it was never intented
to be machine readable.
The Right Way[tm] to do this is to tell the MTA to add a header line
(X-Sender-IP or something).

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