From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pekka Savola Subject: Re: Fw: [PATCH] IPv6: Allow 6to4 routes with SIT Date: Tue, 15 Jul 2003 09:28:11 +0300 (EEST) Sender: netdev-bounce@oss.sgi.com Message-ID: References: <200307142329.DAA06071@dub.inr.ac.ru> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: "David S. Miller" , , Return-path: To: kuznet@ms2.inr.ac.ru In-Reply-To: <200307142329.DAA06071@dub.inr.ac.ru> Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org On Tue, 15 Jul 2003 kuznet@ms2.inr.ac.ru wrote: > > Hey guys, even though yoshfuji is away I don't see any > > reason why I shouldn't apply the patch below to both > > 2.4.x and 2.5.x. It looks very uncontroversial to me. > > > > Any objections? > > I would wait for experts. > > Technically IPv6 does not allow use of non-link-local address > as nexthop address, because nexthop address is expected to be unique > for router. I think we have two choices here: 1) modify /sbin/ip and /sbin/route (and the rest if any) so that they'll parse global next-hop information and resolve it for the kernel, and report the resolved information to the kernel (see the other thread) 2) the kernel supports "must-resolve" next-hops. > Use of IPv4-COMPAT format for tunnels was a hack to make use of tunnel more > handly, it just a tricky way to encapsulate an IPv4 address inside > IPv6 one, it has nothing to do with _real_ IPv4-COMPAT addresses, > (though logically IPv4-COMPAT addresses _are_ really link-local > for 6over4 "network") it is just an element of our API. Use of 6of4 address > is very strange idea in this context, it does not contradict to anything, > of course, but it looks utterly stupid: 6to4 is a complicated format, where > information about nexthop is encoded in an inapproriate way. > The questions sort of: "What the hell? I do a route with nexthop > 2002:x:y::a:b and a:b disappears somewhere." And the question is right, > because plain logic requires to use a:b as meaningful part of nexthop, > it is the part which provides node _identity_, x:y is just routing information, > identifying particullar "6to4" network, it is meaningless when used > as a nexthop address. Apart from architectural purity (I agree it's messy), I think the practical situation is rather simple: for the case of a:b in 6to4, they're always irrelevant. They always refer to the same next-hop whatever information you'll put in there, the implementations won't care (because as a next-hop, it's just a way of saying "the router at address 2002:V4ADDR". Note that nothing _prevents_ you from treating a:b in 2002:x:y::a:b as a meaningful part of the nexthop. They'll just always refer to the same node for whatever a:b you use. Note that the prefix length of 2002:x:y::a:b is /16 -- you should really rewrite your next-hop considerations with s/a:b/x:y::a:b/. I think the problem for of implementation is that "6to4" technique has just been hacked in (but quite nicely). It's a bit, but not much, more special than that IMO. -- Pekka Savola "You each name yourselves king, yet the Netcore Oy kingdom bleeds." Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings