HEADSUP! netgraph Metadata changing.

If you don't know or care about netgraph metadata (e.g. packet priority)
then this shouldn't worry you.

We are changing the netgraph metadata facility (in which arbitrary
metadata can be sent with a packet through processing) to use
the mbuf TAG facility that has been imported by sam.

Netgraph tags will use different cookies to the standard set of 
tags imported with the code, so they will live in a separate namespace,
however they will be handled during GC and manipulation by the standard
tag handling code (Thanks to Sam for giving us the cookie facility).

In the checked in code there are only a couple of users of metadata, but
there may be 3rd parties out there that use it. If so the authors should
contact me as soon as possible to co-ordinate the changeover.

For example the BW_MAN bandwith manager uses metadata to tag
packets selected by its ipfw netgraph node.

Currently the biggest user of metadata is the frame relay LMI
node that tags LMI packets with a higher priority in order to meet
timing constraints given by the standards.

In addition the ng_ksocket node adds info into metadata and I suspect
there are people using that.


julian