I'm curious if anyone knows how to force or influence the default source address selection algorithm for ipv6 in linux. For manually assigned addresses I'm aware of the trick of setting "preferred_lft 0" on all the other addresses so that it avoids deprecated addresses. I've read a little bit about the addrlabel infrastructure but can't seem to get it to do what I want. Perhaps I'm missing something there. In brief my testing situation is this: - radvd sends 6to4 prefix router adverts. - The ipv4 address backing that is dynamic so the 6to4 prefix changes, so I can't use it for static addresses, only for external connectivity (ignoring dhcpv6). - So, I have a unique local address range (fded::/32) used for internal ipv6 connectivity where I can manually assign addresses to servers. - I want to use that same range for dynamic clients so I leave router adverts on. - I can't shutoff the sysctl autoconf on the interface else I'd lose the global connectivity. - The trouble is that for routing within the local address range the dynamically chosen address (eg: fded:2::5054:ff:fe10:eca8/64) is chosen over the statically assigned one (fded:2::2:1/64). This is a little convoluted I know, but more generally I'd like to know if/how to be able to force or at least strongly suggest a particular outgoing source address over another (subject to other routing rules). Basically I think this is given in the "implementation specific rules" note in rule 8 of the rfc 3484. The current situation is problematic for programs that key some authentication features off of the source address (eg: cfengine). It's also preferable to have a known address with PTR records for some connections for logging purposes and the like. It's not always possible to force the application to bind to a particular address and I'd like to know if it's possible to do it in a system wide way. I ran across this post [1] that claims that at least for opensolaris they might provide some way to prefer dhcp or manually assigned addresses over autoconfigured ones. Another question that just occurred to me is: can the stateless configuration algorithm be adjusted to do something like the following? - try the user's configured first choice host addr (subject to duplicate address detection) - failback to eui64, tempaddr, or whatever else Obviously I'm still working through some of the ipv6 implementation details. Let me know if you have any questions. Thanks for your thoughts/ideas, Brian [1] http://mail.opensolaris.org/pipermail/opensolaris-arc/2006-October/000728.html
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