получить информацию об имени (get name information)
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)
getnameinfo — get name information
Синопсис (Synopsis)
#include <sys/socket.h>
#include <netdb.h>
int getnameinfo(const struct sockaddr *restrict sa, socklen_t salen,
char *restrict node, socklen_t nodelen, char *restrict service,
socklen_t servicelen, int flags);
Описание (Description)
The getnameinfo() function shall translate a socket address to a
node name and service location, all of which are defined as in
freeaddrinfo(3p).
The sa argument points to a socket address structure to be
translated. The salen argument contains the length of the address
pointed to by sa.
If the socket address structure contains an IPv4-mapped IPv6
address or an IPv4-compatible IPv6 address, the implementation
shall extract the embedded IPv4 address and lookup the node name
for that IPv4 address.
If the address is the IPv6 unspecified address ("::"), a lookup
shall not be performed and the behavior shall be the same as when
the node's name cannot be located.
If the node argument is non-NULL and the nodelen argument is non-
zero, then the node argument points to a buffer able to contain
up to nodelen bytes that receives the node name as a null-
terminated string. If the node argument is NULL or the nodelen
argument is zero, the node name shall not be returned. If the
node's name cannot be located, the numeric form of the address
contained in the socket address structure pointed to by the sa
argument is returned instead of its name.
If the service argument is non-NULL and the servicelen argument
is non-zero, then the service argument points to a buffer able to
contain up to servicelen bytes that receives the service name as
a null-terminated string. If the service argument is NULL or the
servicelen argument is zero, the service name shall not be
returned. If the service's name cannot be located, the numeric
form of the service address (for example, its port number) shall
be returned instead of its name.
The flags argument is a flag that changes the default actions of
the function. By default the fully-qualified domain name (FQDN)
for the host shall be returned, but:
* If the flag bit NI_NOFQDN is set, only the node name portion
of the FQDN shall be returned for local hosts.
* If the flag bit NI_NUMERICHOST is set, the numeric form of
the address contained in the socket address structure pointed
to by the sa argument shall be returned instead of its name.
* If the flag bit NI_NAMEREQD is set, an error shall be
returned if the host's name cannot be located.
* If the flag bit NI_NUMERICSERV is set, the numeric form of
the service address shall be returned (for example, its port
number) instead of its name.
* If the flag bit NI_NUMERICSCOPE is set, the numeric form of
the scope identifier shall be returned (for example,
interface index) instead of its name. This flag shall be
ignored if the sa argument is not an IPv6 address.
* If the flag bit NI_DGRAM is set, this indicates that the
service is a datagram service (SOCK_DGRAM). The default
behavior shall assume that the service is a stream service
(SOCK_STREAM).
Notes:
1. The two NI_NUMERICxxx flags are required to support
the -n flag that many commands provide.
2. The NI_DGRAM flag is required for the few AF_INET
and AF_INET6 port numbers (for example, [512,514])
that represent different services for UDP and TCP.
The getnameinfo() function shall be thread-safe.
Возвращаемое значение (Return value)
A zero return value for getnameinfo() indicates successful
completion; a non-zero return value indicates failure. The
possible values for the failures are listed in the ERRORS
section.
Upon successful completion, getnameinfo() shall return the node
and service names, if requested, in the buffers provided. The
returned names are always null-terminated strings.
Ошибки (Error)
The getnameinfo() function shall fail and return the
corresponding value if:
[EAI_AGAIN] The name could not be resolved at this time. Future
attempts may succeed.
[EAI_BADFLAGS]
The flags had an invalid value.
[EAI_FAIL] A non-recoverable error occurred.
[EAI_FAMILY]
The address family was not recognized or the address
length was invalid for the specified family.
[EAI_MEMORY]
There was a memory allocation failure.
[EAI_NONAME]
The name does not resolve for the supplied
parameters.
NI_NAMEREQD is set and the host's name cannot be
located, or both nodename and servname were null.
[EAI_OVERFLOW]
An argument buffer overflowed. The buffer pointed to
by the node argument or the service argument was too
small.
[EAI_SYSTEM]
A system error occurred. The error code can be found
in errno.
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
If the returned values are to be used as part of any further name
resolution (for example, passed to getaddrinfo()), applications
should provide buffers large enough to store any result possible
on the system.
Given the IPv4-mapped IPv6 address "::ffff:1.2.3.4", the
implementation performs a lookup as if the socket address
structure contains the IPv4 address "1.2.3.4".
The IPv6 unspecified address ("::") and the IPv6 loopback address
("::1") are not IPv4-compatible addresses.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
endservent(3p), freeaddrinfo(3p), gai_strerror(3p),
inet_ntop(3p), socket(3p)
The Base Definitions volume of POSIX.1‐2017, netdb.h(0p),
sys_socket.h(0p)
