Change the definition of struct if_data's member ifi_epoch from wall

clock time to uptime because wall clock time may go backwards.

This is a change in the API which will impact SNMP agents who are using
ifi_epoch to set RFC2233's ifCounterDiscontinuityTime.  None are know to
exist today.  This will not impact applications that are using the
<index, epoch> tuple to verify interface uniqueness except that it
eliminates a race which could lead to a false assumption of uniqueness.

Because this is a behavior change, bump __FreeBSD_version.

Discussed with:	re (jhb, scottl)
MFC after:	3 days
Pointed out by:	pkh (way back at EuroBSDCon)
Pointy hat:	brooks

1 files changed, 8 insertions, 0 deletions

diff --git a/UPDATING b/UPDATING
index d7bf823..daa6f78 100644
--- a/UPDATING
+++ b/UPDATING
@@ -21,6 +21,14 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 6.x IS SLOW:
 	developers choose to disable these features on build machines
 	to maximize performance.
 
+20050225:
+	The ifi_epoch member of struct if_data has been changed to
+	contain the uptime at which the interface was created or the
+	statistics zeroed rather then the wall clock time because
+	wallclock time may go backwards.  This should have no impact
+	unless an snmp implementation is using this value (I know of
+	none at this point.)
+
 20050223:
 	The layout of struct image_params has changed. You have to
 	recompile all compatibility modules (linux, svr4, etc) for use