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List:       postfix-users
Subject:    Re: DNS lookup for localhost
From:       wietse () porcupine ! org (Wietse Venema)
Date:       2008-09-23 14:58:35
Message-ID: 20080923145835.EBF661F3E99 () spike ! porcupine ! org
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Peter Rabbitson:
> Wietse Venema wrote:
> > Peter Rabbitson:
> >> Hi,
> >>
> >> I encountered a weird behavior with Postfix when specifying
> >> smtp:localhost as a transport destination. After long debugging, tcpdump
> >> revealed that postfix directly asks for 'localhost.<local dns suffix>',
> >> as specified in /etc/hosts:search without first asking for 'localhost'.
> >> Is this intended behavior, or is this an omission? I am using stock
> >> Debian Postfix 2.5.5-1.1
> > 
> > The Postfix SMTP client sets the RES_DEFNAMES flag when it invokes
> > the resolver(3) system library routines to look up the destination
> > host IP address.
> > 
> > According to my manual pages,
> > 
> >      RES_DEFNAMES   If set, res_search() will append the default domain name
> >                     to single-component names (those that do not contain a
> >                     dot).  This option is enabled by default.
> > 
> 
> As far as I can tell this is a flag set in dns_lookup.c, which can not
> be controlled by external methods. So short from recompiling postfix,
> one either has to use [127.0.0.1] in place of localhost, or remove
> search xxx from /etc/resolv.conf, correct?

or add a localhost A/AAAA record under the local DNS domain, and so on.

	Wietse
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