1.\" $NetBSD: inet.4,v 1.12 2002/05/13 08:23:58 kleink 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. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" @(#)inet.4 8.1 (Berkeley) 6/5/93 35.\" 36.Dd June 5, 1993 37.Dt INET 4 38.Os 39.Sh NAME 40.Nm inet 41.Nd Internet protocol family 42.Sh SYNOPSIS 43.Fd #include \*[Lt]sys/types.h\*[Gt] 44.Fd #include \*[Lt]netinet/in.h\*[Gt] 45.Sh DESCRIPTION 46The Internet protocol family is a collection of protocols 47layered atop the 48.Em Internet Protocol 49.Pq Tn IP 50transport layer, and utilizing the Internet address format. 51The Internet family provides protocol support for the 52.Dv SOCK_STREAM , SOCK_DGRAM , 53and 54.Dv SOCK_RAW 55socket types; the 56.Dv SOCK_RAW 57interface provides access to the 58.Tn IP 59protocol. 60.Sh ADDRESSING 61Internet addresses are four byte quantities, stored in 62network standard format (on the 63.Tn VAX 64these are word and byte 65reversed). The include file 66.Aq Pa netinet/in.h 67defines this address 68as a discriminated union. 69.Pp 70Sockets bound to the Internet protocol family utilize 71the following addressing structure, 72.Bd -literal -offset indent 73struct sockaddr_in { 74 sa_family_t sin_family; 75 in_port_t sin_port; 76 struct in_addr sin_addr; 77 int8_t sin_zero[8]; 78}; 79.Ed 80.Pp 81Sockets may be created with the local address 82.Dv INADDR_ANY 83to effect 84.Dq wildcard 85matching on incoming messages. 86The address in a 87.Xr connect 2 88or 89.Xr sendto 2 90call may be given as 91.Dv INADDR_ANY 92to mean 93.Dq this host . 94The distinguished address 95.Dv INADDR_BROADCAST 96is allowed as a shorthand for the broadcast address on the primary 97network if the first network configured supports broadcast. 98.Sh PROTOCOLS 99The Internet protocol family comprises 100the 101.Tn IP 102transport protocol, Internet Control 103Message Protocol 104.Pq Tn ICMP , 105Transmission Control 106Protocol 107.Pq Tn TCP , 108and User Datagram Protocol 109.Pq Tn UDP . 110.Tn TCP 111is used to support the 112.Dv SOCK_STREAM 113abstraction while 114.Tn UDP 115is used to support the 116.Dv SOCK_DGRAM 117abstraction. A raw interface to 118.Tn IP 119is available 120by creating an Internet socket of type 121.Dv SOCK_RAW . 122The 123.Tn ICMP 124message protocol is accessible from a raw socket. 125.Pp 126The 32-bit Internet address contains both network and host parts. 127It is frequency-encoded; the most-significant bit is clear 128in Class A addresses, in which the high-order 8 bits are the network 129number. 130Class B addresses use the high-order 16 bits as the network field, 131and Class C addresses have a 24-bit network part. 132Sites with a cluster of local networks and a connection to the 133Internet may chose to use a single network number for the cluster; 134this is done by using subnet addressing. 135The local (host) portion of the address is further subdivided 136into subnet and host parts. 137Within a subnet, each subnet appears to be an individual network; 138externally, the entire cluster appears to be a single, uniform 139network requiring only a single routing entry. 140Subnet addressing is enabled and examined by the following 141.Xr ioctl 2 142commands on a datagram socket in the Internet domain; 143they have the same form as the 144.Dv SIOCIFADDR 145command (see 146.Xr netintro 4 ) . 147.Pp 148.Bl -tag -width SIOCSIFNETMASK 149.It Dv SIOCSIFNETMASK 150Set interface network mask. 151The network mask defines the network part of the address; 152if it contains more of the address than the address type would indicate, 153then subnets are in use. 154.It Dv SIOCGIFNETMASK 155Get interface network mask. 156.El 157.Sh SEE ALSO 158.Xr ioctl 2 , 159.Xr socket 2 , 160.Xr icmp 4 , 161.Xr intro 4 , 162.Xr ip 4 , 163.Xr netintro 4 , 164.Xr tcp 4 , 165.Xr udp 4 166.Rs 167.%T "An Introductory 4.3 BSD Interprocess Communication Tutorial" 168.%B PS1 169.%N 7 170.Re 171.Rs 172.%T "An Advanced 4.3 BSD Interprocess Communication Tutorial" 173.%B PS1 174.%N 8 175.Re 176.Sh HISTORY 177The 178.Nm 179protocol interface appeared in 180.Bx 4.2 . 181.Sh BUGS 182The Internet protocol support is subject to change as 183the Internet protocols develop. Users should not depend 184on details of the current implementation, but rather 185the services exported. 186