NAME
ares_search - Initiate a DNS query with domain search
SYNOPSIS
#include <ares.h>
typedef void (*ares_callback)(void *arg, int status,
unsigned char *abuf, int alen)
void ares_search(ares_channel channel, const char *name,
int dnsclass, int type, ares_callback callback,
void *arg)
DESCRIPTION
The ares_search function initiates a series of single-question DNS
queries on the name service channel identified by channel, using the
channel’s search domains as well as a host alias file given by the
HOSTALIAS environment variable. The parameter name gives the alias
name or the base of the query name as a NUL-terminated C string of
period-separated labels; if it ends with a period, the channel’s search
domains will not be used. Periods and backslashes within a label must
be escaped with a backslash. The parameters dnsclass and type give the
class and type of the query using the values defined in
<arpa/nameser.h>. When the query sequence is complete or has failed,
the ares library will invoke callback. Completion or failure of the
query sequence may happen immediately, or may happen during a later
call to ares_process(3) or ares_destroy(3).
The callback argument arg is copied from the ares_search argument arg.
The callback argument status indicates whether the query sequence ended
with a successful query and, if not, how the query sequence failed. It
may have any of the following values:
ARES_SUCCESS A query completed successfully.
ARES_ENODATA No query completed successfully; when the query was
tried without a search domain appended, a response
was returned with no answers.
ARES_EFORMERR A query completed but the server claimed that the
query was malformatted.
ARES_ESERVFAIL No query completed successfully; when the query was
tried without a search domain appended, the server
claimed to have experienced a failure. (This code
can only occur if the ARES_FLAG_NOCHECKRESP flag was
specified at channel initialization time; otherwise,
such responses are ignored at the ares_send(3)
level.)
ARES_ENOTFOUND No query completed successfully; when the query was
tried without a search domain appended, the server
reported that the queried-for domain name was not
found.
ARES_ENOTIMP A query completed but the server does not implement
the operation requested by the query. (This code
can only occur if the ARES_FLAG_NOCHECKRESP flag was
specified at channel initialization time; otherwise,
such responses are ignored at the ares_send(3)
level.)
ARES_EREFUSED A query completed but the server refused the query.
(This code can only occur returned if the
ARES_FLAG_NOCHECKRESP flag was specified at channel
initialization time; otherwise, such responses are
ignored at the ares_send(3) level.)
ARES_TIMEOUT No name servers responded to a query within the
timeout period.
ARES_ECONNREFUSED No name servers could be contacted.
ARES_ENOMEM Memory was exhausted.
ARES_EDESTRUCTION The name service channel channel is being destroyed;
the query will not be completed.
If a query completed successfully, the callback argument abuf points to
a result buffer of length alen. If the query did not complete
successfully, abuf will usually be NULL and alen will usually be 0, but
in some cases an unsuccessful query result may be placed in abuf.
SEE ALSO
ares_process(3)
AUTHOR
Greg Hudson, MIT Information Systems
Copyright 1998 by the Massachusetts Institute of Technology.
24 July 1998