remaining code to write

[Francis Dupont]

The on-link CRA works too well: I'll add a flag constrainting a CRA
to forward only queries/responses from/to a colocated client
(BTW this implies the CVS images will have to be updated).

I have not yet an opinion about the default: according to the spec
it should be constrainted by default but it is not very natural.

The other code is an ICMP listen:
 - filter on type = unreachable code = admin prohib
 - the source must be the shared address
 - in the code itself: check the error triger for sanity
 - action: send a message (should be reboot :-)

Regards

Francis Dupont <fdupont at isc.org>