PROLOG¶

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME¶

netinet/in.h — Internet address family

SYNOPSIS¶

#include <netinet/in.h>

DESCRIPTION¶

The <netinet/in.h> header shall define the following types:

in_port_t

Equivalent to the type uint16_t as described in <inttypes.h>.

in_addr_t

Equivalent to the type uint32_t as described in <inttypes.h>.

The <netinet_in.h> header shall define the sa_family_t type as described in <sys/socket.h>.

The <netinet_in.h> header shall define the uint8_t and uint32_t types as described in <inttypes.h>. Inclusion of the <netinet/in.h> header may also make visible all symbols from <inttypes.h> and <sys/socket.h>.

The <netinet/in.h> header shall define the in_addr structure, which shall include at least the following member:

in_addr_t  s_addr

The <netinet/in.h> header shall define the sockaddr_in structure, which shall include at least the following members:

sa_family_t     sin_family   AF_INET.
in_port_t       sin_port     Port number.
struct in_addr  sin_addr     IP address.

The sin_port and sin_addr members shall be in network byte order.

The sockaddr_in structure is used to store addresses for the Internet address family. Pointers to this type shall be cast by applications to struct sockaddr * for use with socket functions.

The <netinet/in.h> header shall define the in6_addr structure, which shall include at least the following member:

uint8_t s6_addr[16]

This array is used to contain a 128-bit IPv6 address, stored in network byte order.

The <netinet/in.h> header shall define the sockaddr_in6 structure, which shall include at least the following members:

sa_family_t      sin6_family    AF_INET6.
in_port_t        sin6_port      Port number.
uint32_t         sin6_flowinfo  IPv6 traffic class and flow information.
struct in6_addr  sin6_addr      IPv6 address.
uint32_t         sin6_scope_id  Set of interfaces for a scope.

The sin6_port and sin6_addr members shall be in network byte order.

The sockaddr_in6 structure shall be set to zero by an application prior to using it, since implementations are free to have additional, implementation-defined fields in sockaddr_in6.

The sin6_scope_id field is a 32-bit integer that identifies a set of interfaces as appropriate for the scope of the address carried in the sin6_addr field. For a link scope sin6_addr, the application shall ensure that sin6_scope_id is a link index. For a site scope sin6_addr, the application shall ensure that sin6_scope_id is a site index. The mapping of sin6_scope_id to an interface or set of interfaces is implementation-defined.

The <netinet/in.h> header shall declare the following external variable:

const struct in6_addr in6addr_any

This variable is initialized by the system to contain the wildcard IPv6 address. The <netinet/in.h> header also defines the IN6ADDR_ANY_INIT macro. This macro must be constant at compile time and can be used to initialize a variable of type struct in6_addr to the IPv6 wildcard address.

The <netinet/in.h> header shall declare the following external variable:

const struct in6_addr in6addr_loopback

This variable is initialized by the system to contain the loopback IPv6 address. The <netinet/in.h> header also defines the IN6ADDR_LOOPBACK_INIT macro. This macro must be constant at compile time and can be used to initialize a variable of type struct in6_addr to the IPv6 loopback address.

The <netinet/in.h> header shall define the ipv6_mreq structure, which shall include at least the following members:

struct in6_addr  ipv6mr_multiaddr  IPv6 multicast address.
unsigned         ipv6mr_interface  Interface index.

The <netinet/in.h> header shall define the following symbolic constants for use as values of the level argument of getsockopt() and setsockopt():

IPPROTO_IP

Internet protocol.

IPPROTO_IPV6

Internet Protocol Version 6.

IPPROTO_ICMP

Control message protocol.

IPPROTO_RAW

Raw IP Packets Protocol.

IPPROTO_TCP

Transmission control protocol.

IPPROTO_UDP

User datagram protocol.

The <netinet/in.h> header shall define the following symbolic constants for use as destination addresses for connect(), sendmsg(), and sendto():

INADDR_ANY

IPv4 local host address.

INADDR_BROADCAST

IPv4 broadcast address.

The <netinet/in.h> header shall define the following symbolic constant, with the value specified, to help applications declare buffers of the proper size to store IPv4 addresses in string form:

INET_ADDRSTRLEN

16. Length of the string form for IP.

The htonl(), htons(), ntohl(), and ntohs() functions shall be available as described in <arpa/inet.h>. Inclusion of the <netinet/in.h> header may also make visible all symbols from <arpa/inet.h>.

The <netinet/in.h> header shall define the following symbolic constant, with the value specified, to help applications declare buffers of the proper size to store IPv6 addresses in string form:

INET6_ADDRSTRLEN

46. Length of the string form for IPv6.

The <netinet/in.h> header shall define the following symbolic constants, with distinct integer values, for use in the option_name argument in the getsockopt() or setsockopt() functions at protocol level IPPROTO_IPV6:

IPV6_JOIN_GROUP

Join a multicast group.

IPV6_LEAVE_GROUP

Quit a multicast group.

IPV6_MULTICAST_HOPS

Multicast hop limit.

IPV6_MULTICAST_IF

Interface to use for outgoing multicast packets.

IPV6_MULTICAST_LOOP

Multicast packets are delivered back to the local application.

IPV6_UNICAST_HOPS

Unicast hop limit.

IPV6_V6ONLY

Restrict AF_INET6 socket to IPv6 communications only.

The <netinet/in.h> header shall define the following macros that test for special IPv6 addresses. Each macro is of type int and takes a single argument of type const struct in6_addr *:

IN6_IS_ADDR_UNSPECIFIED

Unspecified address.

IN6_IS_ADDR_LOOPBACK

Loopback address.

IN6_IS_ADDR_MULTICAST

Multicast address.

IN6_IS_ADDR_LINKLOCAL

Unicast link-local address.

IN6_IS_ADDR_SITELOCAL

Unicast site-local address.

IN6_IS_ADDR_V4MAPPED

IPv4 mapped address.

IN6_IS_ADDR_V4COMPAT

IPv4-compatible address.

IN6_IS_ADDR_MC_NODELOCAL

Multicast node-local address.

IN6_IS_ADDR_MC_LINKLOCAL

Multicast link-local address.

IN6_IS_ADDR_MC_SITELOCAL

Multicast site-local address.

IN6_IS_ADDR_MC_ORGLOCAL

Multicast organization-local address.

IN6_IS_ADDR_MC_GLOBAL

Multicast global address.

The following sections are informative.

APPLICATION USAGE¶

None.

RATIONALE¶

None.

FUTURE DIRECTIONS¶

None.

SEE ALSO¶

Section 4.9, Host and Network Byte Orders, <arpa_inet.h>, <inttypes.h>, <sys_socket.h>

The System Interfaces volume of POSIX.1‐2008, connect(), getsockopt(), htonl(), sendmsg(), sendto(), setsockopt()

COPYRIGHT¶

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.unix.org/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .