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

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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
This commit is contained in:
Brooks Davis 2005-02-25 19:46:41 +00:00
parent 960f641e6d
commit bc9d299133
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=142501
5 changed files with 12 additions and 4 deletions
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8
UPDATING
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@ -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

2
share/man/man9/ifnet.9
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@ -729,7 +729,7 @@ the current value of
.Va if_capenable .
.It ifi_epoch
.Pq Vt time_t
The time the interface was attached or the last time the statistics
The system uptime when interface was attached or the statistics
below were reset.
This is intended to be used to set the SNMP variable
.Va ifCounterDiscontinuityTime .

2
sys/net/if.c
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@ -392,7 +392,7 @@ if_attach(struct ifnet *ifp)
TAILQ_INIT(&ifp->if_multiaddrs);
knlist_init(&ifp->if_klist, NULL);
getmicrotime(&ifp->if_lastchange);
ifp->if_data.ifi_epoch = time_second;
ifp->if_data.ifi_epoch = time_uptime;
#ifdef MAC
mac_init_ifnet(ifp);

2
sys/net/if.h
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@ -102,7 +102,7 @@ struct if_data {
u_long ifi_iqdrops; /* dropped on input, this interface */
u_long ifi_noproto; /* destined for unsupported protocol */
u_long ifi_hwassist; /* HW offload capabilities */
time_t ifi_epoch; /* time of attach or stat reset */
time_t ifi_epoch; /* uptime at attach or stat reset */
#ifdef __alpha__
u_int ifi_timepad; /* time_t is int, not long on alpha */
#endif

2
sys/sys/param.h
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@ -57,7 +57,7 @@
* is created, otherwise 1.
*/
#undef __FreeBSD_version
#define __FreeBSD_version 600014 /* Master, propagated to newvers */
#define __FreeBSD_version 600015 /* Master, propagated to newvers */
#ifndef LOCORE
#include <sys/types.h>