Re: exim, local resolver, host name lookups and IPv6

[Vincent Danjean <vdanjean.ml@free.fr>]

Marc Haber wrote:
> On Sat, 12 Apr 2008 14:58:24 +0000, The Fungi <fungi@yuggoth.org>
> wrote:
>> On Sat, Apr 12, 2008 at 10:41:54AM +0200, Marc Haber wrote:
>> [...]
>>> Where can I obtain the FQDN of the system instead?
>> [...]
>>
>> You can't, necessarily.
> 
> So it needs to be in /etc/hosts.

This would lead to broken config for a lots of *DSL box.
When the machine is running on RFC 1918 addresses behind a NAT (made by
the router), what you need is the external FQDN hostname of the router
(which must be configured to forward the port 25) to answer to the EHLO
greating.
And adding the router fqdn in the machine /etc/hosts seems really wrong
to me in that case: the machine is not the router and must not be reached
when trying to reach the router.

>> Is there any way to simply
>> *insist* the FQDN be present in the config (provided by the
>> administrator via debconf or by manual editing after installation)
>> and just be done with all the guessing?

This seems a good tip. The FQDN for mail must be in a config file.

> I'd rather avoid this and guess the name from a central point created
> during installation.

This value can, indeed, be guested at installation time with any heuristic
(/etc/mailname, gethostby*(), debconf, ...)

>> Maybe even refuse to start
>> the daemon until this is provided, with a clear error message to
>> that effect?
> 
> Nosireebob, people do not read error messages but post bug reports
> instead. I am not prepared to handle these.

So, in case the user REMOVE the config value, you can failback to these
guesses (with a warning in the logs ?). But the normal (enforced at
installation/upgrade time) way should be a documented value in a config
file.

  Best regards,
    Vincent
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