[Dnsmasq-discuss] [PATCH] Wrong DHCPv6 packet originated interface

[Lung-Pin Chang]

Hi Simon,

Sorry for the late reply.

> Is that a legal interface configuration? IPv6 seems to be capable of
> generating endless surprises like this!

IMO this is valid (at least) on a 6to4 router.

> I think that's fine. The only problem remaining is that
> lease_set_interface might be called with the wrong interface, before
> it's called with the right interface. I don't think that causes any
> serious problems, but it might be worth making the patch a bit more
> complex to avoid the problem, to save problems now or in the future.
> Determining the correct interface for each lease in a new_interface
> field in the lease structure,then calling lease_set_interface() on those
> values would do it.

Agreed, patch updated in [1].

> If the nested-prefixes condition can occur in IPv4, then the same thing
> will apply, and the same sort of fix would work. Note that this problem,
> if not fixed, will cause serious issues with the ra-names mode, which
> uses the interface to find the possible SLAAC addresses of host with a
> DHCPv4 lease.

Changes similar to nested prefix fix in IPv6 are also applied to IPv4
part in [1].

I'm not seeing any harm of this change to IPv4, as it picks at least
one interface for each lease, if any matches.

But, as I'm not using ra-names mode and currently I have no spare
resource for testing nested prefix in IPv4,

I'd like to request for a review on the IPv4 part of the patch.

Thanks.

[1]: https://github.com/iamben/dnsmasq/commit/dc8a1b1bcf1a4420063c3a708580fcd3277130c5

-- 
Lung-Pin Chang 張瓏繽

Wireless Internet Laboratory & Computer Center
Department of Computer Science
National Chiao Tung University