1.\" $OpenBSD: inet.4,v 1.9 2001/11/13 13:54:25 mpech Exp $ 2.\" $NetBSD: inet.4,v 1.3 1994/11/30 16:22:18 jtc Exp $ 3.\" 4.\" Copyright (c) 1983, 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. All advertising materials mentioning features or use of this software 16.\" must display the following acknowledgement: 17.\" This product includes software developed by the University of 18.\" California, Berkeley and its contributors. 19.\" 4. Neither the name of the University nor the names of its contributors 20.\" may be used to endorse or promote products derived from this software 21.\" without specific prior written permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" 35.\" @(#)inet.4 8.1 (Berkeley) 6/5/93 36.\" 37.Dd June 5, 1993 38.Dt INET 4 39.Os 40.Sh NAME 41.Nm inet 42.Nd Internet protocol family 43.Sh SYNOPSIS 44.Fd #include <sys/types.h> 45.Fd #include <netinet/in.h> 46.Sh DESCRIPTION 47The Internet protocol family is a collection of protocols 48layered atop the 49.Em Internet Protocol 50.Pq Tn IP 51transport layer, and utilizing the Internet address format. 52The Internet family provides protocol support for the 53.Dv SOCK_STREAM , 54.Dv SOCK_DGRAM , 55and 56.Dv SOCK_RAW 57socket types; the 58.Dv SOCK_RAW 59interface provides access to the 60.Tn IP 61protocol. 62.Sh ADDRESSING 63Internet addresses are four byte quantities, stored in 64network standard format (on the 65.Tn VAX 66these are word and byte 67reversed). 68The include file 69.Aq Pa netinet/in.h 70defines this address as a discriminated union. 71.Pp 72Sockets bound to the Internet protocol family utilize 73the following addressing structure, 74.Bd -literal -offset indent 75struct sockaddr_in { 76 u_int8_t sin_len; 77 sa_family_t sin_family; 78 in_port_t sin_port; 79 struct in_addr sin_addr; 80 int8_t sin_zero[8]; 81}; 82.Ed 83.Pp 84Sockets may be created with the local address 85.Dv INADDR_ANY 86to effect 87.Dq wildcard 88matching on incoming messages. 89The address in a 90.Xr connect 2 91or 92.Xr sendto 2 93call may be given as 94.Dv INADDR_ANY 95to mean 96.Dq this host . 97The distinguished address 98.Dv INADDR_BROADCAST 99is allowed as a shorthand for the broadcast address on the primary 100network if the first network configured supports broadcast. 101.Sh PROTOCOLS 102The Internet protocol family is comprised of 103the 104.Tn IP 105transport protocol, Internet Control 106Message Protocol 107.Pq Tn ICMP , 108Transmission Control 109Protocol 110.Pq Tn TCP , 111and User Datagram Protocol 112.Pq Tn UDP . 113.Tn TCP 114is used to support the 115.Dv SOCK_STREAM 116abstraction while 117.Tn UDP 118is used to support the 119.Dv SOCK_DGRAM 120abstraction. 121A raw interface to 122.Tn IP 123is available 124by creating an Internet socket of type 125.Dv SOCK_RAW . 126The 127.Tn ICMP 128message protocol is accessible from a raw socket. 129.Pp 130The 32-bit Internet address contains both network and host parts. 131It is frequency-encoded; the most-significant bit is clear 132in Class A addresses, in which the high-order 8 bits are the network 133number. 134Class B addresses use the high-order 16 bits as the network field, 135and Class C addresses have a 24-bit network part. 136Sites with a cluster of local networks and a connection to the 137Internet may chose to use a single network number for the cluster; 138this is done by using subnet addressing. 139The local (host) portion of the address is further subdivided 140into subnet and host parts. 141Within a subnet, each subnet appears to be an individual network; 142externally, the entire cluster appears to be a single, uniform 143network requiring only a single routing entry. 144Subnet addressing is enabled and examined by the following 145.Xr ioctl 2 146commands on a datagram socket in the Internet domain; 147they have the same form as the 148.Dv SIOCIFADDR 149command (see 150.Xr netintro 4 ) . 151.Pp 152.Bl -tag -width SIOCSIFNETMASK 153.It Dv SIOCSIFNETMASK 154Set interface network mask. 155The network mask defines the network part of the address; 156if it contains more of the address than the address type would indicate, 157then subnets are in use. 158.It Dv SIOCGIFNETMASK 159Get interface network mask. 160.El 161.Sh SEE ALSO 162.Xr ioctl 2 , 163.Xr socket 2 , 164.Xr icmp 4 , 165.Xr ip 4 , 166.Xr netintro 4 , 167.Xr tcp 4 , 168.Xr udp 4 169.Rs 170.%T "An Introductory 4.3 BSD Interprocess Communication Tutorial" 171.%B PS1 172.%N 7 173.Re 174.Rs 175.%T "An Advanced 4.3 BSD Interprocess Communication Tutorial" 176.%B PS1 177.%N 8 178.Re 179.Sh CAVEATS 180The Internet protocol support is subject to change as 181the Internet protocols develop. 182Users should not depend on details of the current implementation, but rather 183the services exported. 184.Sh HISTORY 185The 186.Nm 187protocol interface appeared in 188.Bx 4.2 . 189