> > The MIB also specifies tentative(6) and duplicate(7) as distinct
 > > values. So one solution (if we want to strictly adhere to rfc 4293)
 > > is to have libipadm return
 > >         preferred(1),      <-> default value (see CR 6832315)
 > >         deprecated(2),     <-> IFF_DEPRECATED
 > >         invalid(3),        <-> ~IFF_UP on the address (also covers DAD 
 > > failed)
 > 
 > I think either we need a new IFF_INVALID or we rely on in.ndpd deleting 
 > an address when it becomes invalid so we never return 3.
 > 
 > >         inaccessible(4),   <-> ~IFF_DOWN on the interface
 > 
 > But it would be good to have a separate flag for this, since it allows 
 > the case when the IP interface goes missing but we want to keep the 
 > address objects around. Thus IFF_INACCESSIBLE.
 > 
 > Note that it might make sense to have an IFF_MISSING for the IP 
 > interface, and in that case we could have IFF_MISSING on the addresses 
 > to mean inaccessible.

While I have no objection to introducing new IFF_* flags, we must assume
that no applications will bother to concern themselves with them.
(Another thing we learned in spades with the original IPMP implementation
via things like IFF_NOFAILOVER.)

Along those lines, there may be more application capture by having IFF_UP
mean "address is usable" and introducing a new flag such as "IFF_ADMUP" to
indicate the address is administratively up (which is irrelevant to most
applications, which instead just want to know whether an address they
found via SIOCG[L]IFCONF is usable).

-- 
meem
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