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Subject: Re: how to bind smtp client to specific address?
From: Christopher E. Brown (cbrowndenalics.net)
Date: Wed Mar 29 2000 - 16:58:09 CST

On Wed, 29 Mar 2000, Wietse Venema wrote:

> Hmm. That behavior (ignoring the IP address given to bind() before
> calling connect()) should break other applications than Postfix.
>
> One example is IDENT lookups from a multi-homed host. These must
> be made with the proper source IP address or the lookup fails.
>
> Another example is paranoid FTP clients that reject DATA connections
> coming from the "wrong" server IP address.
>
> Wietse

        Hmmm, Linux should *only* be using the transmitting interface
IP in the case of an am binding to IN_ADDR_ANY. Any application than
binds to a specific IP (assuming IP is valid) should be using that IP
no matter which network interface the packets are transmitted via.

        You can get into fun with connect backs, or UDP where the
default route is via a different interface than the IP they connected
to. This can be handled by binding the daemon to a particular IP, or
adding a prefered src addr attribute to the default route.

 ---
As folks might have suspected, not much survives except roaches,
and they don't carry large enough packets fast enough...
        --About the Internet and nuclear war.