Hierarchical iprop project review

[Greg Hudson]

Some time ago, Richard Basch submitted code to support a hierarchical
arrangement of slaves for incremental propagation--an intermediate slave
can run "kadmind -proponly" to serve incremental updates to other
slaves, and a downstream slave can run "kpropd -A upstreamslave" to
point at an intermediate slave instead of the master.  This feature can
be useful in environments where either performance or network topology
makes it undesirable to serve incremental updates to every slave from a
single master.

I have finished reworking the code and have written up a detailed
project page summarizing the design changes.  The project page is at:

    http://k5wiki.kerberos.org/wiki/Projects/Hierarchical_iprop

It takes a while to wrap one's head around the ulog design, but if
anyone is sufficiently interested, comments are welcome.

This project does not include the automatic notification work that
Richard did more recently; integrating that will come later.  The
project page also notes some ancillary performance improvement
opportunities.

The code is currently in the hieriprop branch on my github fork:

    https://github.com/greghudson/krb5/commits/ipropbug

It rests on top of two other branches, ipropbug and ipropcleanup, which
are not specifically related to hierarchical iprop.  In total there are
17 commits.  I expect to push these branches over the next couple of
weeks.