[handle PRU_PURGEIF in all protocols]

  I think that is perfectly reasonable. What is the alternative? To have
  the last interface address removal code handle it?

I can see either:

  Purge on last address removal.  This seems like it has to happen on
  all protocols in a domain, so it has the same issue.  (I don't
  understand why the panic I got doesn't happen without my change,
  since I thought all protocols in the domain were called if there was
  an address in the domain.)  Has a touch of elegance, but I'm not
  optimistic that such a complicated invariant can be maintained over
  time as code changes.

  Have a per-protocol NEEDS_PURGEIF flag, and only invoke the method
  on such protocols.  But this seems inelegant to me.


So, I'll start down the path of (not) handling PRU_PURGEIF in \forall
foo \in protocols: foo_usrreq, and submit a patch with that and the
new for loop I just sent.

-- 
        Greg Troxel <gdt@ir.bbn.com>