1.\" Copyright 1996 Massachusetts Institute of Technology 2.\" 3.\" Permission to use, copy, modify, and distribute this software and 4.\" its documentation for any purpose and without fee is hereby 5.\" granted, provided that both the above copyright notice and this 6.\" permission notice appear in all copies, that both the above 7.\" copyright notice and this permission notice appear in all 8.\" supporting documentation, and that the name of M.I.T. not be used 9.\" in advertising or publicity pertaining to distribution of the 10.\" software without specific, written prior permission. M.I.T. makes 11.\" no representations about the suitability of this software for any 12.\" purpose. It is provided "as is" without express or implied 13.\" warranty. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''. M.I.T. DISCLAIMS 16.\" ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE, 17.\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 18.\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT 19.\" SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 20.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 21.\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF 22.\" USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 23.\" ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 24.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 25.\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" $FreeBSD$ 29.\" 30.Dd November 15, 1996 31.Dt IFMIB 4 32.Os 33.Sh NAME 34.Nm ifmib 35.Nd Management Information Base for network interfaces 36.Sh SYNOPSIS 37.In sys/types.h 38.In sys/socket.h 39.In sys/sysctl.h 40.In sys/time.h 41.In net/if.h 42.In net/if_mib.h 43.Sh DESCRIPTION 44The 45.Nm 46facility is an application of the 47.Xr sysctl 3 48interface to provide management information about network interfaces 49to client applications such as 50.Xr netstat 1 , 51.Xr slstat 8 , 52and 53.Tn SNMP 54management agents. 55This information is structured as a table, where 56each row in the table represents a logical network interface (either a 57hardware device or a software pseudo-device like 58.Xr lo 4 ) . 59There are two columns in the table, each containing a single 60structure: one column contains generic information relevant to all 61interfaces, and the other contains information specific to the 62particular class of interface. 63(Generally the latter will implement 64the 65.Tn SNMP 66.Tn MIB 67defined for that particular interface class, if one exists and can be 68implemented in the kernel.) 69.Pp 70The 71.Nm 72facility is accessed via the 73.Dq Li net.link.generic 74branch of the 75.Xr sysctl 3 76MIB. 77The manifest constants for each level in the 78.Xr sysctl 3 79.Ar name 80are defined in 81.In net/if_mib.h . 82The index of the last row in the table is given by 83.Dq Li net.link.generic.system.ifcount 84(or, using the manifest constants, 85.Dv CTL_NET , 86.Dv PF_LINK , 87.Dv NETLINK_GENERIC , 88.Dv IFMIB_SYSTEM , 89.Dv IFMIB_IFCOUNT ) . 90A management application searching for a particular interface should 91start with row 1 and continue through the table row-by-row until the 92desired interface is found, or the interface count is reached. 93Note that the table may be sparse, i.e., a given row may not exist, 94indicated by an 95.Va errno 96of 97.Er ENOENT . 98Such an error should be ignored, and the next row should be checked. 99.Pp 100The generic interface information, common to all interfaces, 101can be accessed via the following procedure: 102.Bd -literal -offset indent 103int 104get_ifmib_general(int row, struct ifmibdata *ifmd) 105{ 106 int name[6]; 107 size_t len; 108 109 name[0] = CTL_NET; 110 name[1] = PF_LINK; 111 name[2] = NETLINK_GENERIC; 112 name[3] = IFMIB_IFDATA; 113 name[4] = row; 114 name[5] = IFDATA_GENERAL; 115 116 len = sizeof(*ifmd); 117 118 return sysctl(name, 6, ifmd, &len, (void *)0, 0); 119} 120.Ed 121.Pp 122The fields in 123.Li struct ifmibdata 124are as follows: 125.Bl -tag -width "ifmd_snd_drops" 126.It Li ifmd_name 127.Pq Li "char []" 128the name of the interface, including the unit number 129.It Li ifmd_pcount 130.Pq Li int 131the number of promiscuous listeners 132.It Li ifmd_flags 133.Pq Li int 134the interface's flags (defined in 135.In net/if.h ) 136.It Li ifmd_snd_len 137.Pq Li int 138the current instantaneous length of the send queue 139.It Li ifmd_snd_drops 140.Pq Li int 141the number of packets dropped at this interface because the send queue 142was full 143.It Li ifmd_data 144.Pq Li struct if_data 145more information from a structure defined in 146.In net/if.h 147(see 148.Xr if_data 9 ) 149.El 150.Pp 151Class-specific information can be retrieved by examining the 152.Dv IFDATA_LINKSPECIFIC 153column instead. 154Note that the form and length of the structure will 155depend on the class of interface. 156For 157.Dv IFT_ETHER , 158.Dv IFT_ISO88023 , 159and 160.Dv IFT_STARLAN 161interfaces, the structure is called 162.Dq Li struct ifmib_iso_8802_3 163(defined in 164.In net/if_mib.h ) , 165and implements a superset of the 166.Tn "RFC 1650" 167MIB for Ethernet-like networks. 168.\" This will eventually be defined in an ethermib(4) page. 169For 170.Dv IFT_SLIP , 171the structure is a 172.Dq Li struct sl_softc 173.Pq In net/if_slvar.h . 174.Sh SEE ALSO 175.Xr sysctl 3 , 176.Xr intro 4 , 177.Xr ifnet 9 178.\" .Xr ethermib 4 , 179.Rs 180.%T "Definitions of Managed Objects for the Ethernet-like Interface Types Using SMIv2" 181.%A F. Kastenholz 182.%D August 1994 183.%O RFC 1650 184.Re 185.Sh HISTORY 186The 187.Nm 188interface first appeared in 189.Fx 2.2 . 190.Sh BUGS 191Many Ethernet-like interfaces do not yet support the Ethernet MIB; 192the interfaces known to support it include 193.Xr ed 4 194and 195.Xr de 4 . 196Regardless, all interfaces automatically support the generic MIB. 197