Routing issue: several interfaces with the same inet6 prefix

This is not an OpenBSD-only problem, but I'm facing it will trying to
configure an OpenBSD based router.

I have the followind network configuration:

          sis0 /-----------\ sis1
(outside) -----|OpenBSD box|------ (local wired net)
               \-----------/
                    rtw0 \.oOo. (local wireless net)

With this in sysctl.conf:
net.inet6.ip6.forwarding=1
net.inet6.ip6.accept_rtadv=1

sis0's IPv6 is configured via stateless autoconfiguration, with a /64
prefix but (first problem) doesn't get a default route (I suspect this
is due to net.inet6.ip6.forwarding).

The machine is then advertising the same prefix on sis1 and rtw0 to
autoconfigure the boxen behind the router. They properly get their
autoconf IP and default routes.

(second and main problem) The router correctly passes request from the
local net to the outside, but then doesn't know where to send them back.
The following type of packets is sent on sis0:

20:52:28.945616 (THE_ROUTERS_IPV6) > ff02::1:ff8b:234a: icmp6:
neighbor sol: who has (THE_CLIENT_ON_rtw0)

"8b:234a" is part of the client's autoconfigured IPv6.

How can I make the router send the packets to the correct interface ? Is
there a way to update the routing tables when receiving packets from the
hosts ?

I guess the same problem will arrise when trying to communicate from a
machine on rtw0's net to a machine on sis1's net.

Any ideas ?

--
Olivier Mehani <[email protected]>
PGP fingerprint: 3720 A1F7 1367 9FA3 C654  6DFB 6845 4071 E346 2FD1

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