1.\" $NetBSD: inet.4,v 1.16 2003/08/07 10:31:02 agc Exp $ 2.\" 3.\" Copyright (c) 1983, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)inet.4 8.1 (Berkeley) 6/5/93 31.\" 32.Dd May 15, 2003 33.Dt INET 4 34.Os 35.Sh NAME 36.Nm inet 37.Nd Internet protocol family 38.Sh SYNOPSIS 39.In sys/types.h 40.In netinet/in.h 41.Sh DESCRIPTION 42The Internet protocol family is a collection of protocols 43layered atop the 44.Em Internet Protocol 45.Pq Tn IP 46transport layer, and using the Internet address format. 47The Internet family provides protocol support for the 48.Dv SOCK_STREAM , SOCK_DGRAM , 49and 50.Dv SOCK_RAW 51socket types; the 52.Dv SOCK_RAW 53interface provides access to the 54.Tn IP 55protocol. 56.Sh ADDRESSING 57Internet addresses are four byte quantities, stored in 58network standard format (on the 59.Tn VAX 60these are word and byte 61reversed). The include file 62.Aq Pa netinet/in.h 63defines this address 64as a discriminated union. 65.Pp 66Sockets bound to the Internet protocol family use 67the following addressing structure, 68.Bd -literal -offset indent 69struct sockaddr_in { 70 sa_family_t sin_family; 71 in_port_t sin_port; 72 struct in_addr sin_addr; 73 int8_t sin_zero[8]; 74}; 75.Ed 76.Pp 77Sockets may be created with the local address 78.Dv INADDR_ANY 79to effect 80.Dq wildcard 81matching on incoming messages. 82The address in a 83.Xr connect 2 84or 85.Xr sendto 2 86call may be given as 87.Dv INADDR_ANY 88to mean 89.Dq this host . 90The distinguished address 91.Dv INADDR_BROADCAST 92is allowed as a shorthand for the broadcast address on the primary 93network if the first network configured supports broadcast. 94.Sh PROTOCOLS 95The Internet protocol family comprises 96the 97.Tn IP 98transport protocol, Internet Control 99Message Protocol 100.Pq Tn ICMP , 101Transmission Control 102Protocol 103.Pq Tn TCP , 104and User Datagram Protocol 105.Pq Tn UDP . 106.Tn TCP 107is used to support the 108.Dv SOCK_STREAM 109abstraction while 110.Tn UDP 111is used to support the 112.Dv SOCK_DGRAM 113abstraction. A raw interface to 114.Tn IP 115is available 116by creating an Internet socket of type 117.Dv SOCK_RAW . 118The 119.Tn ICMP 120message protocol is accessible from a raw socket. 121.Pp 122The 32-bit Internet address contains both network and host parts. 123It is frequency-encoded; the most-significant bit is clear 124in Class A addresses, in which the high-order 8 bits are the network 125number. 126Class B addresses use the high-order 16 bits as the network field, 127and Class C addresses have a 24-bit network part. 128Sites with a cluster of local networks and a connection to the 129Internet may chose to use a single network number for the cluster; 130this is done by using subnet addressing. 131The local (host) portion of the address is further subdivided 132into subnet and host parts. 133Within a subnet, each subnet appears to be an individual network; 134externally, the entire cluster appears to be a single, uniform 135network requiring only a single routing entry. 136Subnet addressing is enabled and examined by the following 137.Xr ioctl 2 138commands on a datagram socket in the Internet domain; 139they have the same form as the 140.Dv SIOCIFADDR 141command (see 142.Xr netintro 4 ) . 143.Pp 144.Bl -tag -width SIOCSIFNETMASK 145.It Dv SIOCSIFNETMASK 146Set interface network mask. 147The network mask defines the network part of the address; 148if it contains more of the address than the address type would indicate, 149then subnets are in use. 150.It Dv SIOCGIFNETMASK 151Get interface network mask. 152.El 153.Sh SEE ALSO 154.Xr ioctl 2 , 155.Xr socket 2 , 156.Xr icmp 4 , 157.Xr intro 4 , 158.Xr ip 4 , 159.Xr netintro 4 , 160.Xr tcp 4 , 161.Xr udp 4 162.Rs 163.%T "An Introductory 4.4BSD Interprocess Communication Tutorial" 164.%A Stuart Sechrest 165.Re 166.Pq see Pa /usr/share/doc/psd/20.ipctut 167.Rs 168.%T "Advanced 4.4BSD IPC Tutorial" 169.%A Samuel J. Leffler 170.%A Robert S. Fabry 171.%A William N. Joy 172.%A Phil Lapsley 173.%A Steve Miller 174.%A Chris Torek 175.Re 176.Pq see Pa /usr/share/doc/psd/21.ipc 177.Sh HISTORY 178The 179.Nm 180protocol interface appeared in 181.Bx 4.2 . 182.Sh BUGS 183The Internet protocol support is subject to change as 184the Internet protocols develop. Users should not depend 185on details of the current implementation, but rather 186the services exported. 187