.\" $OpenBSD: inet.4,v 1.7 2000/12/21 21:01:16 aaron Exp $ .\" $NetBSD: inet.4,v 1.3 1994/11/30 16:22:18 jtc Exp $ .\" .\" Copyright (c) 1983, 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)inet.4 8.1 (Berkeley) 6/5/93 .\" .Dd June 5, 1993 .Dt INET 4 .Os .Sh NAME .Nm inet .Nd Internet protocol family .Sh SYNOPSIS .Fd #include .Fd #include .Sh DESCRIPTION The Internet protocol family is a collection of protocols layered atop the .Em Internet Protocol .Pq Tn IP transport layer, and utilizing the Internet address format. The Internet family provides protocol support for the .Dv SOCK_STREAM , .Dv SOCK_DGRAM , and .Dv SOCK_RAW socket types; the .Dv SOCK_RAW interface provides access to the .Tn IP protocol. .Sh ADDRESSING Internet addresses are four byte quantities, stored in network standard format (on the .Tn VAX these are word and byte reversed). The include file .Aq Pa netinet/in.h defines this address as a discriminated union. .Pp Sockets bound to the Internet protocol family utilize the following addressing structure, .Bd -literal -offset indent struct sockaddr_in { u_int8_t sin_len; sa_family_t sin_family; in_port_t sin_port; struct in_addr sin_addr; int8_t sin_zero[8]; }; .Ed .Pp Sockets may be created with the local address .Dv INADDR_ANY to effect .Dq wildcard matching on incoming messages. The address in a .Xr connect 2 or .Xr sendto 2 call may be given as .Dv INADDR_ANY to mean .Dq this host . The distinguished address .Dv INADDR_BROADCAST is allowed as a shorthand for the broadcast address on the primary network if the first network configured supports broadcast. .Sh PROTOCOLS The Internet protocol family is comprised of the .Tn IP transport protocol, Internet Control Message Protocol .Pq Tn ICMP , Transmission Control Protocol .Pq Tn TCP , and User Datagram Protocol .Pq Tn UDP . .Tn TCP is used to support the .Dv SOCK_STREAM abstraction while .Tn UDP is used to support the .Dv SOCK_DGRAM abstraction. A raw interface to .Tn IP is available by creating an Internet socket of type .Dv SOCK_RAW . The .Tn ICMP message protocol is accessible from a raw socket. .Pp The 32-bit Internet address contains both network and host parts. It is frequency-encoded; the most-significant bit is clear in Class A addresses, in which the high-order 8 bits are the network number. Class B addresses use the high-order 16 bits as the network field, and Class C addresses have a 24-bit network part. Sites with a cluster of local networks and a connection to the Internet may chose to use a single network number for the cluster; this is done by using subnet addressing. The local (host) portion of the address is further subdivided into subnet and host parts. Within a subnet, each subnet appears to be an individual network; externally, the entire cluster appears to be a single, uniform network requiring only a single routing entry. Subnet addressing is enabled and examined by the following .Xr ioctl 2 commands on a datagram socket in the Internet domain; they have the same form as the .Dv SIOCIFADDR command (see .Xr netintro 4 ) . .Pp .Bl -tag -width SIOCSIFNETMASK .It Dv SIOCSIFNETMASK Set interface network mask. The network mask defines the network part of the address; if it contains more of the address than the address type would indicate, then subnets are in use. .It Dv SIOCGIFNETMASK Get interface network mask. .El .Sh SEE ALSO .Xr ioctl 2 , .Xr socket 2 , .Xr icmp 4 , .Xr ip 4 , .Xr netintro 4 , .Xr tcp 4 , .Xr udp 4 .Rs .%T "An Introductory 4.3 BSD Interprocess Communication Tutorial" .%B PS1 .%N 7 .Re .Rs .%T "An Advanced 4.3 BSD Interprocess Communication Tutorial" .%B PS1 .%N 8 .Re .Sh CAVEAT The Internet protocol support is subject to change as the Internet protocols develop. Users should not depend on details of the current implementation, but rather the services exported. .Sh HISTORY The .Nm protocol interface appeared in .Bx 4.2 .