Date: Thu, 24 Aug 2006 14:36:58 -0400 From: Pat Lashley <patl@volant.org> To: Brooks Davis <brooks@one-eyed-alien.net> Cc: freebsd-net@freebsd.org, Doug Barton <dougb@freebsd.org>, Fredrik Lindberg <fli+freebsd-net@shapeshifter.se> Subject: Re: Zeroconfig and Multicast DNS Message-ID: <806B67472BBA47707142E56E@garrett.local> In-Reply-To: <20060824193127.GA38855@lor.one-eyed-alien.net> References: <44ED3BD1.3030206@shapeshifter.se> <AC5769F16F9730CABCCC4E61@garrett.local> <44EDA9A5.2050108@shapeshifter.se> <BE1059C6974AD43BC382E107@garrett.local> <44EDBDD0.4050000@shapeshifter.se> <7CC9AC69410B69EBD31122E4@garrett.local> <44EDDB8C.9090504@shapeshifter.se> <0EC404BA0CA363942D250766@garrett.local> <20060824182640.GA37561@lor.one-eyed-alien.net> <B69C016E0D5F0C26B40BE4C0@garrett.local> <20060824193127.GA38855@lor.one-eyed-alien.net>
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> > Actually, it is quite possible for multiple interfaces to be on the same > > LLA link/subnet; so we can't make any assumptions either way. We -do- need > > to be able to handle the case where they are on different links. That > > really isn't an 'unless', it's a 'when'. > > I can't see how it's worth worrying about the case they are on the same > network. I'm pretty sure that if you act as though they are on separate > networks things will work just as well weather they are or not. I'd have to go dig through the RFCs. I suspect that it wouldn't make any difference to the normal interface usage; but might be significant to the LLA and/or mDNS protocol handling. And we most certainly don't want to allow bridging to be enabled between the interfaces if they -are- on the same segment. > > We also need to be able to handle the case where they are on physically > > different links; but the host is acting as a bridge between them to make > > one logical link sharing a single LLA subnet. (We don't need to explicitly > > handle the case where the bridging is being handled externally because that > > should be virtually indistinguishable from a single physical link.) > > If there's a bridge (only considering if_bridge here) then the bridge > interface should have the LLA. Configuring LLAs on the physical > interfaces would be wrong and isn't worth supporting. It's been a long time since I've set up a bridge; so I'm a bit rusty on all of the details. But from the if_bridge man page, it doesn't look like the bridge interface has an IP address of its own. (And I can't see why it would want one.) Also, I was using 'bridge' as a short-hand which would include any sort of proxying or routing that would make two physical segments operate as one local link for address negotiation. Overall, I don't really expect that to be a big issue; just one of those less common setups that we need to ensure does something reasonable by default. > The right way to deal with this is almost certainly to adopt the KAME > %interface decoration for link local addresses. LLAs are meaningless > outside the context of an interface. Unless you only have one interface > with an LLA, you must know which interface you are addressing to know > where to send the packet. While you can hack around this in some cases > by trying all of them and hoping there aren't any collisions, I think > that's the wrong way to go. Except in the case where multiple interfaces are on the same segment for redundancy. But in general, I suspect that you are right that using a %interface notation is the way to go. Now, how do we handle the problem in DNS-SD ? The service records just have a domain name. -Pat
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