exim question

Paul Vixie vixie@isc.org
Wed Jul 14 15:13:56 UTC 2010

> Date: Wed, 14 Jul 2010 13:29:38 +0200
> From: Jakob Hirsch <jh@plonk.de>
> > "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?

i think it's something sendmail just did, and that others have emulated.
(i hate it, and my own received:-header parsers strip out "ipv6:" if they
see it, before trying to use whatever's left as coloned-hex or dotted-dec).

> Parsing Received headers is always dodgy, because it was never intented
> to be machine readable.

that's what i thought too, but there is a grammar and they are indeed meant
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).

yes but using Received: is how most inbound procmail recipes work.

i think that anyone who depends on "ipv6:" and doesn't just strip it out and
throw it away, should have to cite RFC chapter and verse on the matter.

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