Date: Sat, 18 Oct 2008 19:18:52 +0200 From: Hartmut Brandt <hartmut.brandt@dlr.de> To: Eugene Grosbein <eugen@kuzbass.ru> Cc: net@freebsd.org Subject: Re: SNMP High Capacity Counters Message-ID: <48FA1A7C.5060801@dlr.de> In-Reply-To: <20081018092405.GA91929@svzserv.kemerovo.su>
index | next in thread | previous in thread | raw e-mail
Eugene Grosbein wrote: > Hi! > > I've just found that ports/net-snmp (version 5.4) built > WITH_MFD_REWRITES=yes supports IF-MIB, and in theory should show 64-bit > ifHC* counters but it does not. > > It seems agent/mibgroup/if-mib/data_access/interface_sysctl.c that obtains > interface statistics from the kernel. > The function netsnmp_arch_interface_container_load() has the following code: > > /* get counters */ > entry->stats.ibytes.low = ifp->ifm_data.ifi_ibytes; > entry->stats.ibytes.high = 0; > entry->stats.iucast.low = ifp->ifm_data.ifi_ipackets; > entry->stats.iucast.high = 0; > entry->stats.imcast.low = ifp->ifm_data.ifi_imcasts; > entry->stats.imcast.high = 0; > > So, it always produce 32-bit quantities. My question is: > does FreeBSD/i386 kernel maintain 64-bit counters for interface statictics > these days? If yes, since what version? It does not, because not all architectures have atomic 64-bit increments and adds. Implementing 64-bit counters on these architectures would require some kind of locking. This was discussed in the past. You might look at the IF-MIB implementation of bsnmp (it is in the base system). It uses periodic polling to detect wraps of the 32-bit counters. The poll interval is tuned to the fastest interface in the system (given that all interfaces reported the correct speed). Note, that the netsnmp implementation is plain wrong - if the daemon does not support the HC counters it should never pretend to do. This is explicitely stated somewhere in the RFCs. hartihome | help
Want to link to this message? Use this
URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?48FA1A7C.5060801>