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: src/share/man/man4/ifmib.4,v 1.8.2.6 2002/10/10 18:21:41 johan Exp $ 29.\" 30.Dd May 20, 2019 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 . 82A count of interfaces (and thus rows 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. 93.Pp 94The generic interface information, common to all interfaces, 95can be accessed via the following procedure: 96.Bd -literal -offset indent 97int 98get_ifmib_general(int row, struct ifmibdata *ifmd) 99{ 100 int name[6]; 101 size_t len; 102 103 name[0] = CTL_NET; 104 name[1] = PF_LINK; 105 name[2] = NETLINK_GENERIC; 106 name[3] = IFMIB_IFDATA; 107 name[4] = row; 108 name[5] = IFDATA_GENERAL; 109 110 len = sizeof(*ifmd); 111 112 return sysctl(name, 6, ifmd, &len, NULL, 0); 113} 114.Ed 115.Pp 116The fields in 117.Li struct ifmibdata 118are as follows: 119.Bl -tag -width "ifmd_snd_drops" 120.It Li ifmd_name 121.Pq Li "char []" 122the name of the interface, including the unit number 123.It Li ifmd_pcount 124.Pq Li int 125the number of promiscuous listeners 126.It Li ifmd_flags 127.Pq Li int 128the interface's flags (defined in 129.In net/if.h ) 130.It Li ifmd_snd_len 131.Pq Li int 132the current instantaneous length of the send queue 133.It Li ifmd_snd_drops 134.Pq Li int 135the number of packets dropped at this interface because the send queue 136was full 137.It Li ifmd_data 138.Pq Li struct if_data 139more information from a structure defined in 140.In net/if.h 141(see 142.Xr if_data 9 ) 143.El 144.Pp 145Class-specific information can be retrieved by examining the 146.Dv IFDATA_LINKSPECIFIC 147column instead. 148Note that the form and length of the structure will 149depend on the class of interface. 150For 151.Dv IFT_ETHER , 152.Dv IFT_ISO88023 , 153and 154.Dv IFT_STARLAN 155interfaces, the structure is called 156.Dq Li struct ifmib_iso_8802_3 157(defined in 158.In net/if_mib.h ) , 159and implements a superset of the 160.Tn "RFC 1650" 161MIB for Ethernet-like networks. 162.\" This will eventually be defined in an ethermib(4) page. 163For 164.Dv IFT_SLIP , 165the structure is a 166.Dq Li struct sl_softc 167.Pq In net/sl/if_slvar.h . 168.Sh SEE ALSO 169.Xr sysctl 3 , 170.Xr intro 4 , 171.Xr ifnet 9 172.\" .Xr ethermib 4 , 173.Rs 174.%T "Definitions of Managed Objects for the Ethernet-like Interface Types Using SMIv2" 175.%A F. Kastenholz 176.%D August 1994 177.%O RFC 1650 178.Re 179.Sh HISTORY 180The 181.Nm 182interface first appeared in 183.Fx 2.2 . 184.Sh BUGS 185Many Ethernet-like interfaces do not yet support the Ethernet MIB; 186the interfaces known to support it include 187.Xr de 4 . 188Regardless, all interfaces automatically support the generic MIB. 189