INET(4) | Device Drivers Manual | INET(4) |
inet
— Internet
protocol family
#include
<sys/types.h>
#include <netinet/in.h>
The Internet protocol family is a collection of protocols layered
atop the
Internet
Protocol (IP) transport layer, and utilizing the Internet address
format. The Internet family provides protocol support for the
SOCK_STREAM
, SOCK_DGRAM
, and
SOCK_RAW
socket types; the
SOCK_RAW
interface provides access to the IP
protocol.
Internet addresses are four byte quantities, stored in network standard format (on the VAX these are word and byte reversed). The include file ⟨netinet/in.h⟩ defines this address as a discriminated union.
Sockets bound to the Internet protocol family utilize the following addressing structure,
struct sockaddr_in { short sin_family; u_short sin_port; struct in_addr sin_addr; char sin_zero[8]; };
Sockets may be created with the local address
INADDR_ANY
to effect “wildcard”
matching on incoming messages. The address in a
connect(2),
connectx(2) or
sendto(2) call may be given as
INADDR_ANY
to mean “this host”. The
distinguished address INADDR_BROADCAST
is allowed as
a shorthand for the broadcast address on the primary network if the first
network configured supports broadcast.
The Internet protocol family is comprised of the IP transport
protocol, Internet Control Message Protocol (ICMP), Transmission Control
Protocol (TCP), and User Datagram Protocol (UDP). TCP is used to support the
SOCK_STREAM
abstraction while UDP is used to support
the SOCK_DGRAM
abstraction. A raw interface to IP is
available by creating an Internet socket of type
SOCK_RAW
. The ICMP message protocol is accessible
from a raw socket.
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 ioctl(2)
commands on a datagram socket in the Internet domain; they have the same
form as the SIOCIFADDR
command (see
intro(4)).
SIOCSIFNETMASK
SIOCGIFNETMASK
ioctl(2), socket(2), icmp(4), intro(4), ip(4), tcp(4), udp(4)
An Introductory 4.3 BSD Interprocess Communication Tutorial, PS1, 7.
An Advanced 4.3 BSD Interprocess Communication Tutorial, PS1, 8.
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.
The inet
protocol interface appeared in
4.2BSD.
March 18, 2015 | BSD 4.2 |