Re: notion of a local address [was: Re: ioctl SIOCGIFNETMASK: ip

dean gaudet (dean-list-linux-kernel@arctic.org)
Thu, 6 Sep 2001 12:15:56 -0700 (PDT)


On Thu, 6 Sep 2001, Wietse Venema wrote:

> Andrey Savochkin:
> > > That is not practical. Surely there is an API to find out if an IP
> > > address connects to the machine itself. If every UNIX system on
> > > this planet can do it, then surely Linux can do it.
> >
> > Let me correct you: you need to recognize not addresses that result in
> > connecting to the _machine_ itself, but connecting to the same _MTA_.
>
> The SMTP RFC requires that user@[ip.address] is correctly recognized
> as a final destination. This requires that Linux provides the MTA
> with information about IP addresses that correspond with INADDR_ANY.
>
> I am susprised that it is not possible to ask such information up
> front (same with netmasks), and that an application has to actually
> query a complex oracle, again and again, for every IP address.

how does your MTA figure out that it's behind a NAT? it doesn't matter
what unix it's running on, there's no standard way for it to know that an
address translation has occured before getting to its front-door.

i've dealt with almost the exact same problem you're dealing with now when
i was correcting apache's virtual hosting mechanism. the only solution
which i found to work *always* was to force the administrator to
explicitly list the addresses.

-dean

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