Date: Sat, 11 Dec 2004 11:28:25 +0100 From: Andrea Campi <andrea+freebsd_net@webcom.it> To: Chuck Swiger <cswiger@mac.com> Cc: net@freebsd.org Subject: Re: Working on howl port Message-ID: <20041211102825.GB12803@webcom.it> In-Reply-To: <41BAC0BD.7000706@mac.com> References: <20041211090235.GD11190@webcom.it> <41BAC0BD.7000706@mac.com>
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On Sat, Dec 11, 2004 at 04:41:17AM -0500, Chuck Swiger wrote: > Andrea Campi wrote: > [ ... ] > >The way I'm addressing this is to have autoipd use SIOCAIFADDR > >and manage exactly one address in the 169.254/16 block. This > >means you will ALWAYS have an IP address in that range; if you > >also run dhclient, you might have an additional IP and a default > >route. > > > >Thoughts? > > See http://files.zeroconf.org/draft-ietf-zeroconf-ipv4-linklocal.txt: > > 1.9. When to configure an IPv4 Link-Local address > > Having addresses of multiple different scopes assigned to an > interface, with no adequate way to determine in what circumstances > each address should be used, leads to complexity for applications and > confusion for users. A host with an address on a link can > communicate with all other devices on that link, whether those > devices use Link- Local addresses, or routable addresses. For these > reasons, a host SHOULD NOT have both an operable routable address and > an IPv4 Link-Local address configured on the same interface. > > ...but there is more there to read. It's fine to let an interface have a > 169.254/16 IP and a "real" IP (assigned by DHCP, the user, etc) for a > little while during transitions, but not forever. Uhm. Yes, I can see the point about added complexity, and that was my main concern as well. I forgot that the RFC explicitely mentioned this however. Still, what's worse, having two correct but potentially confusing addresses, and everything still working; or having DHCP and autoipd fighting over which one determines the one and only IP address? I'll have to check how Mac OS X handles this, but unless we merge zeroconf in dhclient (ugh!) or vice versa, I don't see an alternative which is as convenient for the user. Do you? Bye, Andrea -- Give a man a fish and you feed him for a day; teach him to use the Net and he won't bother you for weeks.
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