In message <20050302044037.GA29385@che.ojctech.com>, David Young writes:
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>The IETF Zeroconf working group has introduced "link-local"
>IPv4 addresses (those in 169.254/16).  The "scope" of these IPv4
>addresses is the attached link (ethernet, PPP, whatever), only.  See
><http://files.zeroconf.org/draft-ietf-zeroconf-ipv4-linklocal.txt>, which
>describes the link-local addresses and a method for auto-configuration.
>Link-local IPv4 addresses are widely used in PC operating systems
>(Windows, MacOS 9, Mac0S X) and peripherals (printers).
>
>A host should not use a link-local source address to talk to non-link
>local destinations.  This breaks the scope rule.  Attached is a patch
>that makes sure a host selects non-link local source addresses for IPv4
>packets that have non-link local destinations.
>
>I would like to add this to the kernel, default disabled, enabled by
>'options IPV4_LINKLOCAL'.
>
>Please not that the ifa_getifa method is fairly versatile.  It could be
>used to implement preferred source addresses, for example.  There was
>a discussion about that a little while ago on tech-net@.
>

Hmm -- is there any reason this can't be done via a user-level daemon?

		--Prof. Steven M. Bellovin, http://www.cs.columbia.edu/~smb