ares_gethostbyaddr(3) Library Functions Manual ares_gethostbyaddr(3)
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_t *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.
When the associated callback is called, it is called with a channel
lock so care must be taken to ensure any processing is minimal to
prevent DNS channel stalls.
The callback may be triggered from a different thread than the one
which called ares_gethostbyaddr(3).
For integrators running their own event loops and not using
ARES_OPT_EVENT_THREAD, care needs to be taken to ensure any file
descriptor lists are updated immediately within the eventloop when
notified.
SEE ALSO
ares_process(3), ares_gethostbyname(3)
24 July 1998 ares_gethostbyaddr(3)
c-ares 1.30.0 - Generated Thu Jun 13 11:48:39 CDT 2024