NAME¶
ares_gethostbyaddr - Initiate a host query by address
SYNOPSIS¶
#include <ares.h>
typedef void (*ares_host_callback)(void *arg, int status,
int timeouts, struct hostent *hostent)
void ares_gethostbyaddr(ares_channel channel, const void *addr,
int addrlen, int family, ares_host_callback callback,
void *arg)
DESCRIPTION¶
The
ares_gethostbyaddr function initiates a host query by address on the
name service channel identified by
channel. The parameters
addr
and
addrlen give the address as a series of bytes, and
family
gives the type of address. 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_gethostbyaddr
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.
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
hostent
points to a
struct hostent containing the name of the host returned by
the query. The callback need not and should not attempt to free the memory
pointed to by
hostent; the ares library will free it when the callback
returns. If the query did not complete successfully,
hostent will be
NULL.
SEE ALSO¶
ares_process(3),
ares_gethostbyname(3)
AUTHOR¶
Greg Hudson, MIT Information Systems
Copyright 1998 by the Massachusetts Institute of Technology.