bsd/man/man4/inet.4

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  34 .\"     @(#)inet.4      8.1 (Berkeley) 6/5/93
  35 .\"
  36 .Dd June 5, 1993
  37 .Dt INET 4
  38 .Os BSD 4.2
  39 .Sh NAME
  40 .Nm inet
  41 .Nd Internet protocol family
  42 .Sh SYNOPSIS
  43 .Fd #include <sys/types.h>
  44 .Fd #include <netinet/in.h>
  45 .Sh DESCRIPTION
  46 The Internet protocol family is a collection of protocols
  47 layered atop the
  48 .Em Internet  Protocol
  49 .Pq Tn IP
  50 transport layer, and utilizing the Internet address format.
  51 The Internet family provides protocol support for the
  52 .Dv SOCK_STREAM , SOCK_DGRAM ,
  53 and
  54 .Dv SOCK_RAW
  55 socket types; the
  56 .Dv SOCK_RAW
  57 interface provides access to the
  58 .Tn IP
  59 protocol.
  60 .Sh ADDRESSING
  61 Internet addresses are four byte quantities, stored in
  62 network standard format (on the
  63 .Tn VAX
  64 these are word and byte
  65 reversed).  The include file
  66 .Aq Pa netinet/in.h
  67 defines this address
  68 as a discriminated union.
  69 .Pp
  70 Sockets bound to the Internet protocol family utilize
  71 the following addressing structure,
  72 .Bd -literal -offset indent
  73 struct sockaddr_in {
  74         short   sin_family;
  75         u_short sin_port;
  76         struct  in_addr sin_addr;
  77         char    sin_zero[8];
  78 };
  79 .Ed
  80 .Pp
  81 Sockets may be created with the local address
  82 .Dv INADDR_ANY
  83 to effect
  84 .Dq wildcard
  85 matching on incoming messages.
  86 The address in a
  87 .Xr connect 2
  88 or
  89 .Xr sendto 2
  90 call may be given as
  91 .Dv INADDR_ANY
  92 to mean
  93 .Dq this host .
  94 The distinguished address
  95 .Dv INADDR_BROADCAST
  96 is allowed as a shorthand for the broadcast address on the primary
  97 network if the first network configured supports broadcast.
  98 .Sh PROTOCOLS
  99 The Internet protocol family is comprised of
 100 the
 101 .Tn IP
 102 transport protocol, Internet Control
 103 Message Protocol
 104 .Pq Tn ICMP ,
 105 Transmission Control
 106 Protocol
 107 .Pq Tn TCP ,
 108 and User Datagram Protocol
 109 .Pq Tn UDP .
 110 .Tn TCP
 111 is used to support the
 112 .Dv SOCK_STREAM
 113 abstraction while
 114 .Tn UDP
 115 is used to support the
 116 .Dv SOCK_DGRAM
 117 abstraction.  A raw interface to
 118 .Tn IP
 119 is available
 120 by creating an Internet socket of type
 121 .Dv SOCK_RAW .
 122 The
 123 .Tn ICMP
 124 message protocol is accessible from a raw socket.
 125 .Pp
 126 The 32-bit Internet address contains both network and host parts.
 127 It is frequency-encoded; the most-significant bit is clear
 128 in Class A addresses, in which the high-order 8 bits are the network
 129 number.
 130 Class B addresses use the high-order 16 bits as the network field,
 131 and Class C addresses have a 24-bit network part.
 132 Sites with a cluster of local networks and a connection to the
 133 Internet may chose to use a single network number for the cluster;
 134 this is done by using subnet addressing.
 135 The local (host) portion of the address is further subdivided
 136 into subnet and host parts.
 137 Within a subnet, each subnet appears to be an individual network;
 138 externally, the entire cluster appears to be a single, uniform
 139 network requiring only a single routing entry.
 140 Subnet addressing is enabled and examined by the following
 141 .Xr ioctl 2
 142 commands on a datagram socket in the Internet domain;
 143 they have the same form as the
 144 .Dv SIOCIFADDR
 145 command (see
 146 .Xr intro 4 ) .
 147 .Pp
 148 .Bl -tag -width SIOCSIFNETMASK
 149 .It Dv SIOCSIFNETMASK
 150 Set interface network mask.
 151 The network mask defines the network part of the address;
 152 if it contains more of the address than the address type would indicate,
 153 then subnets are in use.
 154 .It Dv SIOCGIFNETMASK
 155 Get interface network mask.
 156 .El
 157 .Sh SEE ALSO
 158 .Xr ioctl 2 ,
 159 .Xr socket 2 ,
 160 .Xr intro 4 ,
 161 .Xr tcp 4 ,
 162 .Xr udp 4 ,
 163 .Xr ip 4 ,
 164 .Xr icmp 4
 165 .Rs
 166 .%T "An Introductory 4.3 BSD Interprocess Communication Tutorial"
 167 .%B PS1
 168 .%N 7
 169 .Re
 170 .Rs
 171 .%T "An Advanced 4.3 BSD Interprocess Communication Tutorial"
 172 .%B PS1
 173 .%N 8
 174 .Re
 175 .Sh CAVEAT
 176 The Internet protocol support is subject to change as
 177 the Internet protocols develop.  Users should not depend
 178 on details of the current implementation, but rather
 179 the services exported.
 180 .Sh HISTORY
 181 The
 182 .Nm
 183 protocol interface appeared in
 184 .Bx 4.2 .