Re: forward DNS lookups in $mynetworks or check_client_access

[Magnus Bäck <magnus@xxxxxxxxxxx>]

On Monday, October 04, 2004 at 15:00 CEST,
     /dev/rob0 <rob0@xxxxxxxxx> wrote:

[...]

> access(5):
> ...
> DESCRIPTION
>        The  optional access table directs the Postfix SMTP server
>        to selectively  reject  or  accept  mail.  Access  can  be
>        allowed  or  denied for specific host names, domain names,
>        networks, host network addresses or mail addresses.
> ...
> HOST NAME/ADDRESS PATTERNS
>        With lookups from indexed files such as DB or DBM, or from
>        networked  tables  such as NIS, LDAP or SQL, the following
>        lookup patterns are examined in the order as listed:
> 
>        domain.tld
>               Matches domain.tld.
> ...
> 
> This does not say how the DNS resolution is done. My testing indicates
> that it's done in the same way as in $mynetworks, only acting on the
> hostname returned from the reverse DNS lookup.
> 
> Can postfix natively look up a record in forward DNS and apply access 
> rules to the resulting IP address? If so I don't see how.

Postfix cannot do this, because it is impossible. The only thing Postfix
knows about a connecting client is its IP address. To get a name from
that address, a PTR lookup is issued. If there is a resulting A record
that matches the client address, Postfix will use the looked-up hostname
in access map lookups (and log messages etc).

>From where would Postfix get the dynamically determined hostname you
wish to put in your access map?

-- 
Magnus Bäck
magnus@xxxxxxxxxxx