семейство интернет-адресов (Internet address family)
Пролог (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.
Имя (Name)
netinet/in.h — Internet address family
Синопсис (Synopsis)
#include <netinet/in.h>
Описание (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.
Prior to calling a function in this standard which reads values
from a sockaddr_in6 structure (for example, bind() or connect()),
the application shall ensure that all members of the structure,
including any additional non-standard members, if any, are
initialized. If the sockaddr_in6 structure has a non-standard
member, and that member has a value other than the value that
would result from default initialization, the behavior of any
function in this standard that reads values from the sockaddr_in6
structure is implementation-defined. All functions in this
standard that return data in a sockaddr_in6 structure (for
example, getaddrinfo() or accept()) shall initialize the
structure in a way that meets the above requirements, and shall
ensure that each non-standard member, if any, has a value that
produces the same behavior as default initialization would in all
functions in this standard which read values from a sockaddr_in6
structure.
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
constant for use as a local address in the structure passed to
bind():
INADDR_ANY IPv4 wildcard address.
The <netinet/in.h> header shall define the following symbolic
constant for use as a destination address in the structures
passed to connect(), sendmsg(), and sendto():
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.
Использование в приложениях (Application usage)
Although applications are required to initialize all members
(including any non-standard ones) of a sockaddr_in6 structure,
the same is not required for the sockaddr_in structure, since
historically many applications only initialized the standard
members. Despite this, applications are encouraged to initialize
sockaddr_in structures in a manner similar to the required
initialization of sockaddr_in6 structures.
Although it is common practice to initialize a sockaddr_in6
structure using:
struct sockaddr_in6 sa;
memset(&sa, 0, sizeof sa);
this method is not portable according to this standard, because
the structure can contain pointer or floating-point members that
are not required to have an all-bits-zero representation after
default initialization. Portable methods make use of default
initialization; for example:
struct sockaddr_in6 sa = { 0 };
or:
static struct sockaddr_in6 sa_init;
struct sockaddr_in6 sa = sa_init;
A future version of this standard may require that a pointer
object with an all-bits-zero representation is a null pointer,
and that sockaddr_in6 does not have any floating-point members if
a floating-point object with an all-bits-zero representation does
not have the value 0.0.
Обоснование (Rationale)
The INADDR_ANY and INADDR_BROADCAST values are byte-order-neutral
and thus their byte order is not specified. Many implementations
have additional constants as extensions, such as INADDR_LOOPBACK,
that are not byte-order-neutral. Traditionally, these constants
are in host byte order, requiring the use of htonl() when using
them in a sockaddr_in structure.
Будущие направления (Future directions)
None.
Смотри также (See also)
Section 4.10, Host and Network Byte Orders, arpa_inet.h(0p),
inttypes.h(0p), sys_socket.h(0p)
The System Interfaces volume of POSIX.1‐2017, connect(3p),
getsockopt(3p), htonl(3p), sendmsg(3p), sendto(3p),
setsockopt(3p)
