bsd/man/man4/inet.4

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  34 .\"     @(#)inet.4      8.1 (Berkeley) 6/5/93
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  36 .Dd March 18, 2015
  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 .Xr connectx 2
  89 or
  90 .Xr sendto 2
  91 call may be given as
  92 .Dv INADDR_ANY
  93 to mean
  94 .Dq this host .
  95 The distinguished address
  96 .Dv INADDR_BROADCAST
  97 is allowed as a shorthand for the broadcast address on the primary
  98 network if the first network configured supports broadcast.
  99 .Sh PROTOCOLS
 100 The Internet protocol family is comprised of
 101 the
 102 .Tn IP
 103 transport protocol, Internet Control
 104 Message Protocol
 105 .Pq Tn ICMP ,
 106 Transmission Control
 107 Protocol
 108 .Pq Tn TCP ,
 109 and User Datagram Protocol
 110 .Pq Tn UDP .
 111 .Tn TCP
 112 is used to support the
 113 .Dv SOCK_STREAM
 114 abstraction while
 115 .Tn UDP
 116 is used to support the
 117 .Dv SOCK_DGRAM
 118 abstraction.  A raw interface to
 119 .Tn IP
 120 is available
 121 by creating an Internet socket of type
 122 .Dv SOCK_RAW .
 123 The
 124 .Tn ICMP
 125 message protocol is accessible from a raw socket.
 126 .Pp
 127 The 32-bit Internet address contains both network and host parts.
 128 It is frequency-encoded; the most-significant bit is clear
 129 in Class A addresses, in which the high-order 8 bits are the network
 130 number.
 131 Class B addresses use the high-order 16 bits as the network field,
 132 and Class C addresses have a 24-bit network part.
 133 Sites with a cluster of local networks and a connection to the
 134 Internet may chose to use a single network number for the cluster;
 135 this is done by using subnet addressing.
 136 The local (host) portion of the address is further subdivided
 137 into subnet and host parts.
 138 Within a subnet, each subnet appears to be an individual network;
 139 externally, the entire cluster appears to be a single, uniform
 140 network requiring only a single routing entry.
 141 Subnet addressing is enabled and examined by the following
 142 .Xr ioctl 2
 143 commands on a datagram socket in the Internet domain;
 144 they have the same form as the
 145 .Dv SIOCIFADDR
 146 command (see
 147 .Xr intro 4 ) .
 148 .Pp
 149 .Bl -tag -width SIOCSIFNETMASK
 150 .It Dv SIOCSIFNETMASK
 151 Set interface network mask.
 152 The network mask defines the network part of the address;
 153 if it contains more of the address than the address type would indicate,
 154 then subnets are in use.
 155 .It Dv SIOCGIFNETMASK
 156 Get interface network mask.
 157 .El
 158 .Sh SEE ALSO
 159 .Xr ioctl 2 ,
 160 .Xr socket 2 ,
 161 .Xr icmp 4 ,
 162 .Xr intro 4 ,
 163 .Xr ip 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 CAVEAT
 177 The Internet protocol support is subject to change as
 178 the Internet protocols develop.  Users should not depend
 179 on details of the current implementation, but rather
 180 the services exported.
 181 .Sh HISTORY
 182 The
 183 .Nm
 184 protocol interface appeared in
 185 .Bx 4.2 .