dropped routing socket messages...

[jtc%acorntoolworks.com@localhost (J.T. Conklin)]

I have a system that uses a user-space routing table implementation.
It uses the kernel routing table as a forwarding table, and installs
and removes routes as needed by the higher level routing policy.  It
also opens a routing socket and monitors it for addresses being added
and deleted from interfaces, interface link state, etc.

Occasionally (less than 1% of system restarts), it seems that routing
table events are being lost which results in my user-space routing
table getting out of sync with reality.

Under what circumstances would this happen? My initial hypotheses were
that the either kernel couldn't allocate an mbuf for the event, or the
routing socket receive buffer wasn't large enough and the even was
dropped then.  But I don't see any "requests for memory denied" in 
the mbuf stats (netstat -m); and I've set the socket buffer size to
128K, and the total number of events is way lower than that.

Is there any other likely reasons where routing socket events would 
be dropped?  FWIW, this is a NetBSD-4 kernel.

    --jtc

-- 
J.T. Conklin