[krbdev.mit.edu #8164] git commit

[Greg Hudson via RT]

Avoid unnecessary iprop full resyncs after resets

When resetting the ulog header or initializing it from a dump file
kdb_last_t value, instead of setting kdb_num to 0, create a dummy
entry for the last_sno value so that we can remember its timestamp.
With this change, a slave no longer needs to perform two full resyncs
after an upstream header initialization.  Dummy entries are never
transmitted to downstream slaves because the iprop protocol never
transmits the kdb_first_sno update; if one is somehow transmitted, the
slave will ignore it because it doesn't have the kdb_commit flag set.

reset_header() is renamed to reset_ulog(), takes a kdb_log_context
parameter, and is responsible for syncing the header.  sync_update()
now returns void and aborts if msync() fails, just like sync_header().
A new helper set_dummy() writes a dummy entry and sets the ulog to
point to it.

Adjust kproplog to recognize and display dummy entries.  Adjust
t_ulog.c and t_iprop.py for the new behavior.  In t_iprop.py, remove a
kpropd -t test which became redundant with the previous test.

https://github.com/krb5/krb5/commit/0a8d39d8c4cbe0539343b44a9a1ebaebe9d1b363
Author: Greg Hudson <ghudson at mit.edu>
Commit: 0a8d39d8c4cbe0539343b44a9a1ebaebe9d1b363
Branch: master
 src/lib/kdb/kdb_log.c |   77 ++++++++++++++++---------
 src/lib/kdb/t_ulog.c  |    6 +-
 src/slave/kproplog.c  |   16 ++++--
 src/tests/t_iprop.py  |  153 ++++++++++++++++++++++--------------------------
 4 files changed, 133 insertions(+), 119 deletions(-)