ARES_GETNAMEINFO
Section: C Library Functions (3)
Updated: 1 May 2009
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NAME
ares_getnameinfo - Address-to-nodename translation in protocol-independent manner
SYNOPSIS
#include <ares.h>
typedef void (*ares_nameinfo_callback)(void *arg, int status,
void ares_getnameinfo(ares_channel channel, const struct sockaddr *sa,
ares_socklen_t salen, int flags, ares_nameinfo_callback callback,
void *arg)
DESCRIPTION
The
ares_getnameinfo
function is defined for protocol-independent address translation. The function
is a combination of
ares_gethostbyaddr(3) and
getservbyport(3). The function will
translate the address either by executing a host query on the name service channel
identified by
channel
or it will attempt to resolve it locally if possible.
The parameters
sa
and
len
give the address as a sockaddr structure, and
flags
gives the options that the function will use. Valid flags are listed below:
- ARES_NI_NOFQDN
-
Only the nodename portion of the FQDN is returned for local hosts.
- ARES_NI_NUMERICHOST
-
The numeric form of the hostname is returned rather than the name.
- ARES_NI_NAMEREQD
-
An error is returned if the hostname cannot be found in the DNS.
- ARES_NI_NUMERICSERV
-
The numeric form of the service is returned rather than the name.
- ARES_NI_TCP
-
The service name is to be looked up for the TCP protocol.
- ARES_NI_UDP
-
The service name is to be looked up for the UDP protocol.
- ARES_NI_SCTP
-
The service name is to be looked up for the SCTP protocol.
- ARES_NI_DCCP
-
The service name is to be looked up for the DCCP protocol.
- ARES_NI_NUMERICSCOPE
-
The numeric form of the scope ID is returned rather than the name.
- ARES_NI_LOOKUPHOST
-
A hostname lookup is being requested.
- ARES_NI_LOOKUPSERVICE
-
A service name lookup is being requested.
When the query
is complete or has
failed, the ares library will invoke callback. Completion or failure of
the query may happen immediately, or may happen during a later call to
ares_process(3), ares_destroy(3) or ares_cancel(3).
The callback argument
arg
is copied from the
ares_getnameinfo
argument
arg.
The callback argument
status
indicates whether the query succeeded and, if not, how it failed. It
may have any of the following values:
- ARES_SUCCESS
-
The host lookup completed successfully.
- ARES_ENOTIMP
-
The ares library does not know how to look up addresses of type
family.
- ARES_ENOTFOUND
-
The address
addr
was not found.
- ARES_ENOMEM
-
Memory was exhausted.
- ARES_ECANCELLED
-
The query was cancelled.
- ARES_EDESTRUCTION
-
The name service channel
channel
is being destroyed; the query will not be completed.
- ARES_EBADFLAGS
-
The
flags
parameter contains an illegal value.
The callback argument
timeouts
reports how many times a query timed out during the execution of the
given request.
On successful completion of the query, the callback argument
node
contains a string representing the hostname (assuming
ARES_NI_LOOKUPHOST
was specified). Additionally,
service
contains a string representing the service name (assuming
ARES_NI_LOOKUPSERVICE
was specified).
If the query did not complete successfully, or one of the values
was not requested,
node
or
service
will be
NULL.
SEE ALSO
ares_process(3),
AUTHOR
Dominick Meglio
Copyright 2005 by Dominick Meglio.