1inet(7P) Protocols inet(7P)
2
6 inet - Internet protocol family
7
9 #include <sys/types.h>
10 #include <netinet/in.h>
13
16 The Internet protocol family implements a collection of protocols which
17 are centered around the Internet Protocol ("IP") and which share a com‐
18 mon address format. The Internet family protocols can be accessed using
19 the socket interface, where they support the SOCK_STREAM, SOCK_DGRAM,
20 and SOCK_RAW socket types, or the Transport Level Interface (TLI),
21 where they support the connectionless (T_CLTS) and connection oriented
22 (T_COTS_ORD) service types.
23
25 The Internet protocol family is comprised of the Internet Protocol
26 ("IP"), the Address Resolution Protocol ("ARP"), the Internet Control
27 Message Protocol ("ICMP"), the Transmission Control Protocol ("TCP"),
28 and the User Datagram Protocol ("UDP").
29 TCP supports the socket interface's SOCK_STREAM abstraction and TLI's
32 T_COTS_ORD service type. UDP supports the SOCK_DGRAM socket abstraction
33 and the TLI T_CLTS service type. See tcp(7P) and udp(7P). A direct
34 interface to IP is available using both TLI and the socket interface
35 (see ip(7P)). ICMP is used by the kernel to handle and report errors in
36 protocol processing. It is also accessible to user programs (see
37 icmp(7P)). ARP is used to translate 32-bit IP addresses into 48-bit
38 Ethernet addresses. See arp(7P).
39 The 32-bit IP address is divided into network number and host number
42 parts. It is frequency-encoded. The most-significant bit is zero in
43 Class A addresses, in which the high-order 8 bits represent the network
44 number. Class B addresses have their high order two bits set to 10 and
45 use the high-order 16 bits as the network number field. Class C
46 addresses have a 24-bit network number part of which the high order
47 three bits are 110. Sites with a cluster of IP networks may chose to
48 use a single network number for the cluster; this is done by using sub‐
49 net addressing. The host number portion of the address is further sub‐
50 divided into subnet number and host number parts. Within a subnet, each
51 subnet appears to be an individual network. Externally, the entire
52 cluster appears to be a single, uniform network requiring only a single
53 routing entry. Subnet addressing is enabled and examined by the follow‐
54 ing ioctl(2) commands. They have the same form as the SIOCSIFADDR com‐
55 mand.
56 SIOCSIFNETMASK Set interface network mask. The network mask defines
58 the network part of the address; if it contains more
59 of the address than the address type would indicate,
60 then subnets are in use.
61 SIOCGIFNETMASK Get interface network mask.
64
67 IP addresses are four byte quantities, stored in network byte order. IP
68 addresses should be manipulated using the byte order conversion rou‐
69 tines. See byteorder(3SOCKET).
70 Addresses in the Internet protocol family use the sockaddr_in struc‐
73 ture, which has that following members:
74 short sin_family;
76 ushort_t sin_port;
77 struct in_addr sin_addr;
78 char sin_zero[8];
79 Library routines are provided to manipulate structures of this form;
83 See inet(3SOCKET).
84 The sin_addr field of the sockaddr_in structure specifies a local or
87 remote IP address. Each network interface has its own unique IP
88 address. The special value INADDR_ANY may be used in this field to
89 effect "wildcard" matching. Given in a bind(3SOCKET) call, this value
90 leaves the local IP address of the socket unspecified, so that the
91 socket will receive connections or messages directed at any of the
92 valid IP addresses of the system. This can prove useful when a process
93 neither knows nor cares what the local IP address is or when a process
94 wishes to receive requests using all of its network interfaces. The
95 sockaddr_in structure given in the bind(3SOCKET) call must specify an
96 in_addr value of either INADDR_ANY or one of the system's valid IP
97 addresses. Requests to bind any other address will elicit the error
98 EADDRNOTAVAIL. When a connect(3SOCKET) call is made for a socket that
99 has a wildcard local address, the system sets the sin_addr field of the
100 socket to the IP address of the network interface that the packets for
101 that connection are routed through.
102 The sin_port field of the sockaddr_in structure specifies a port number
105 used by TCP or UDP. The local port address specified in a bind(3SOCKET)
106 call is restricted to be greater than IPPORT_RESERVED (defined in
107 <<netinet/in.h>>) unless the creating process is running as the supe‐
108 ruser, providing a space of protected port numbers. In addition, the
109 local port address must not be in use by any socket of same address
110 family and type. Requests to bind sockets to port numbers being used by
111 other sockets return the error EADDRINUSE. If the local port address is
112 specified as 0, then the system picks a unique port address greater
113 than IPPORT_RESERVED. A unique local port address is also picked when a
114 socket which is not bound is used in a connect(3SOCKET) or sendto (see
115 send(3SOCKET)) call. This allows programs which do not care which local
116 port number is used to set up TCP connections by simply calling
117 socket(3SOCKET) and then connect(3SOCKET), and to send UDP datagrams
118 with a socket(3SOCKET) call followed by a sendto() call.
119 Although this implementation restricts sockets to unique local port
122 numbers, TCP allows multiple simultaneous connections involving the
123 same local port number so long as the remote IP addresses or port num‐
124 bers are different for each connection. Programs may explicitly over‐
125 ride the socket restriction by setting the SO_REUSEADDR socket option
126 with setsockopt (see getsockopt(3SOCKET)).
127 TLI applies somewhat different semantics to the binding of local port
130 numbers. These semantics apply when Internet family protocols are used
131 using the TLI.
132
134 ioctl(2), bind(3SOCKET), byteorder(3SOCKET), connect(3SOCKET), gethost‐
135 byname(3NSL), getnetbyname(3SOCKET), getprotobyname(3SOCKET), get‐
136 servbyname(3SOCKET), getsockopt(3SOCKET), send(3SOCKET),
137 socket(3SOCKET), arp(7P), icmp(7P), ip(7P), tcp(7P), udp(7P)
138 Network Information Center, DDN Protocol Handbook (3 vols.), Network
141 Information Center, SRI International, Menlo Park, Calif., 1985.
142
144 The Internet protocol support is subject to change as the Internet pro‐
145 tocols develop. Users should not depend on details of the current
146 implementation, but rather the services exported.
147SunOS 5.11 3 Aug 2000 inet(7P)