(usagi-users 03065) Neighbor Discovery on multihomed stateless autoconfigured host

["Casas, Sergi" <sergi.casas@xxxxxx>]

Hi.

This is a question on what is the expected behavior of the USAGI
implementation, and what would be the most correct behavior in this
case.

Scenario:
- a host with multiple IPv6 interfaces in physically separated links
- no routers in any of the links, no DHCPv6 servers (this is a home
networking or SMB scenario)
- the host using stateless autoconfiguration on the well-known
link-local prefix FE80::0 as per RFC2462
- all nodes connected to all the links are also only using link-local
addresses on the well-know prefix FE80::0

Problem:
- How does the Neighbor Discovery algorithm in the host find in which
one of the interfaces a certain link-local destination address is to be
found

Background:
- IBM AIX will send Neighbor Solicitation messages out on each interface
with a link-local address defined
- RFC2461 in Appendix A points to the problem, but offers no solution.
It suggests, though, "to perform address resolution on all interfaces"
- Browsing USAGI code at net/core/neighbour.c, I think it will only try
on one interface (probably selected from the routing table "a la IPv4")

Question:
- I believe the AIX implementation is the correct one to make this
scenario work, what does USAGI do in this case ?
- I think this use case should have a matching test case included in the
IPv6 test suites (TAHI and any other): is it there ? which one is it ?


Thanks,

Sergi Casas
Hewlett Packard