On Fri, Jun 24, 2005 at 09:12:03AM +1200, Perry Lorier wrote: > > > No idea. Don't know if any implementations allow it, and how is > > implementation dependent. Would be quite interesting to know how > > much of 3484 is implemented in different systems, and also how > > to change policy if possible. > > Linux (as of 2.6.11) has a rather dumb source address selection policy > in the mainline kernel. From my reading of the code it selects the > first address on an interface that isn't tentative and has identical > scope. It also prefers non deprecated, non temporary (or temporary > addresses if configured to do so) addresses where possible. > > This however means it always uses the address that was added last, so if > you have a slow tunnel to somewhere that takes longer to setup, that > will be the source address it will prefer over any other one, much to my > dismay. > > The Linux community seem to have indicated that they want preferences > handled by having a preferred source address used per route. I was > looking at the source to Linux and the code appears to be there to use a > source address if one is specified in the routing table, however the > code to insert one somewhere seems broken (either in user space or > kernel space, I didn't figure it out). If there is no source address > specified in the routing table it falls back to the algorithm uses above. > > The code is in net/ipv6/addrconf.c in the function ipv6.*_get_saddr.* > functions.
Note it's not just source address selection; RFC3484 is address selection for source and destination. So really it's more a case of a preferred source address per destination address, then per route. I guess at present very few systems are multiaddressed for IPv6, so it's really 'just' a matter of picking the right source to use for a destination, but Iljitsch's example and Mark's survey shows the implementations are lacking. Whether there are improvements to make on 3484 based on experience is another question (like the ULA+global causing problems with multicast). -- Tim/::1 _______________________________________________ 6bone mailing list [email protected] http://mailman.isi.edu/mailman/listinfo/6bone
