On Mon, 4 Oct 2004 23:11:58 +0200
Harald Welte [off-list ref] wrote:

yes, I remember that email.  I didn't think further about it, since I
got the feeling that there is significant movement to get rid of the
neighbour cache at some point (if/when there is some fast lookup
algorithm implemented) - and if we look at ipv6, there is no routing
cache.

Another idea is to dynamically grow the thresholds based upon usage
just as we do for the hash tables.  For example, if we find say %90
of neighbour entries in-use at forced GC time, we increment the
thresholds by some factor.

Note that the "in-use" part is very important, it prevents a DoS
spam from growing the neighbour cache since such traffic causes
neighbour entries to quickly become unused.