187 lines
5.2 KiB
Groff
187 lines
5.2 KiB
Groff
.\" Copyright 1996 Massachusetts Institute of Technology
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.\"
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.\" Permission to use, copy, modify, and distribute this software and
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.\" its documentation for any purpose and without fee is hereby
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.\" granted, provided that both the above copyright notice and this
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.\" permission notice appear in all copies, that both the above
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.\" copyright notice and this permission notice appear in all
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.\" supporting documentation, and that the name of M.I.T. not be used
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.\" in advertising or publicity pertaining to distribution of the
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.\" software without specific, written prior permission. M.I.T. makes
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.\" no representations about the suitability of this software for any
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.\" purpose. It is provided "as is" without express or implied
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.\" warranty.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''. M.I.T. DISCLAIMS
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.\" ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
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.\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
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.\" SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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.\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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.\" USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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.\" ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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.\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd December 26, 2020
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.Dt IFMIB 4
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.Os
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.Sh NAME
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.Nm ifmib
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.Nd Management Information Base for network interfaces
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.Sh SYNOPSIS
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.In sys/types.h
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.In sys/socket.h
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.In sys/sysctl.h
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.In sys/time.h
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.In net/if.h
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.In net/if_mib.h
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.Sh DESCRIPTION
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The
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.Nm
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facility is an application of the
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.Xr sysctl 3
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interface to provide management information about network interfaces
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to client applications such as
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.Xr netstat 1 ,
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.Xr slstat 8 ,
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and
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.Tn SNMP
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management agents.
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This information is structured as a table, where
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each row in the table represents a logical network interface (either a
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hardware device or a software pseudo-device like
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.Xr lo 4 ) .
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There are two columns in the table, each containing a single
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structure: one column contains generic information relevant to all
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interfaces, and the other contains information specific to the
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particular class of interface.
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(Generally the latter will implement
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the
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.Tn SNMP
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.Tn MIB
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defined for that particular interface class, if one exists and can be
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implemented in the kernel.)
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.Pp
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The
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.Nm
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facility is accessed via the
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.Dq Li net.link.generic
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branch of the
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.Xr sysctl 3
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MIB.
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The manifest constants for each level in the
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.Xr sysctl 3
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.Ar name
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are defined in
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.In net/if_mib.h .
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The index of the last row in the table is given by
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.Dq Li net.link.generic.system.ifcount
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(or, using the manifest constants,
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.Dv CTL_NET ,
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.Dv PF_LINK ,
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.Dv NETLINK_GENERIC ,
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.Dv IFMIB_SYSTEM ,
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.Dv IFMIB_IFCOUNT ) .
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A management application searching for a particular interface should
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start with row 1 and continue through the table row-by-row until the
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desired interface is found, or the interface count is reached.
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Note that the table may be sparse, i.e., a given row may not exist,
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indicated by an
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.Va errno
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of
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.Er ENOENT .
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Such an error should be ignored, and the next row should be checked.
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.Pp
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The generic interface information, common to all interfaces,
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can be accessed via the following procedure:
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.Bd -literal -offset indent
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int
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get_ifmib_general(int row, struct ifmibdata *ifmd)
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{
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int name[6];
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size_t len;
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name[0] = CTL_NET;
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name[1] = PF_LINK;
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name[2] = NETLINK_GENERIC;
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name[3] = IFMIB_IFDATA;
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name[4] = row;
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name[5] = IFDATA_GENERAL;
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len = sizeof(*ifmd);
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return sysctl(name, 6, ifmd, &len, (void *)0, 0);
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}
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.Ed
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.Pp
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The fields in
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.Li struct ifmibdata
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are as follows:
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.Bl -tag -width "ifmd_snd_drops"
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.It Li ifmd_name
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.Pq Li "char []"
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the name of the interface, including the unit number
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.It Li ifmd_pcount
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.Pq Li int
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the number of promiscuous listeners
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.It Li ifmd_flags
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.Pq Li int
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the interface's flags (defined in
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.In net/if.h )
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.It Li ifmd_snd_len
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.Pq Li int
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the current instantaneous length of the send queue
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.It Li ifmd_snd_drops
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.Pq Li int
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the number of packets dropped at this interface because the send queue
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was full
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.It Li ifmd_data
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.Pq Li struct if_data
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more information from a structure defined in
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.In net/if.h
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(see
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.Xr if_data 9 )
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.El
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.Pp
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Class-specific information can be retrieved by examining the
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.Dv IFDATA_LINKSPECIFIC
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column instead.
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Note that the form and length of the structure will
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depend on the class of interface.
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For
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.Dv IFT_ETHER ,
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.Dv IFT_ISO88023 ,
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and
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.Dv IFT_STARLAN
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interfaces, the structure is called
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.Dq Li struct ifmib_iso_8802_3
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(defined in
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.In net/if_mib.h ) ,
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and implements a superset of the
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.Tn "RFC 1650"
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MIB for Ethernet-like networks.
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.Sh SEE ALSO
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.Xr sysctl 3 ,
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.Xr intro 4 ,
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.Xr ifnet 9
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.\" .Xr ethermib 4 ,
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.Rs
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.%T "Definitions of Managed Objects for the Ethernet-like Interface Types Using SMIv2"
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.%A F. Kastenholz
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.%D August 1994
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.%O RFC 1650
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.Re
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.Sh HISTORY
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The
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.Nm
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interface first appeared in
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.Fx 2.2 .
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.Sh BUGS
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Many Ethernet-like interfaces do not yet support the Ethernet MIB.
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Regardless, all interfaces automatically support the generic MIB.
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