Subject: Flag to exclude an interface from INADDR_ANY?
To: None <>
From: Jim Wise <>
List: tech-net
Date: 01/02/2002 10:04:10
Hash: SHA1

Please note:  this is *not* a strong-vs-weak host model post.  I
strongly believe a sysctl to choose strong or weak host model is in
order, but this is a separate question, specifically:

What do people think of the idea of adding a per-interface flag,
settable with ifconfig, to indicate that an interface should not be
included in INADDR_ANY?

Such a flag would be especially useful in a strong host model of course,
but even in the current model, there are many instances of hosts which
have one or more interfaces on which it is not desirable to have daemons
listening (think a management-lan interface, or the outside interface
of a NAT or proxy gateway).

As many daemons, (in particular all current RPC services) provide no way
to limit the daemon to listening on a particular subset of interfaces on
the system, it seems to me valuable to have the ability to indicate that
an interface is _not_ intended to be listened on by general services.

(And yes, of course this can be done with ipf, but let's face it, having
a daemon actually listening on the undesired port and then blocking
access with ipf in a way designed not to be picked up by port scanners
is error-prone at best, and worse, subject to race conditions, such as
connections in the brief interval between ipf stopping and starting when
invoking /etc/rc.d/ipfilter reload).

- -- 
				Jim Wise
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