ARES_CREATE_QUERY(3) Library Functions Manual ARES_CREATE_QUERY(3)NAME
ares_create_query - Compose a single-question DNS query buffer
SYNOPSIS
#include <ares.h>
int ares_create_query(const char *name, int dnsclass, int type,
unsigned short id, int rd, unsigned char **buf,
int *buflen, int max_udp_size)
DESCRIPTION
The ares_create_query function composes a DNS query with a single question. The parameter name gives the query name as a NUL-terminated C
string of period-separated labels optionally ending with a period; periods and backslashes within a label must be escaped with a backlash.
The parameters dnsclass and type give the class and type of the query using the values defined in <arpa/nameser.h>. The parameter id gives
a 16-bit identifier for the query. The parameter rd should be nonzero if recursion is desired, zero if not. The query will be placed in
an allocated buffer, a pointer to which will be stored in the variable pointed to by buf, and the length of which will be stored in the
variable pointed to by buflen. It is the caller's responsibility to free this buffer using ares_free_string(3) when it is no longer
needed. The parameter max_udp_size should be nonzero to activate EDNS. Usage of ares_create_query(3) with max_udp_size set to zero is
equivalent to ares_mkquery(3).
RETURN VALUES
ares_create_query can return any of the following values:
ARES_SUCCESS Construction of the DNS query succeeded.
ARES_EBADNAME The query name name could not be encoded as a domain name, either because it contained a zero-length label or because it
contained a label of more than 63 characters.
ARES_ENOMEM Memory was exhausted.
AVAILABILITY
Added in c-ares 1.10.0
SEE ALSO ares_expand_name(3), ares_free_string(3)AUTHOR
17 Aug 2012 ARES_CREATE_QUERY(3)
Check Out this Related Man Page
ARES_SEARCH(3) Library Functions Manual ARES_SEARCH(3)NAME
ares_search - Initiate a DNS query with domain search
SYNOPSIS
#include <ares.h>
typedef void (*ares_callback)(void *arg, int status,
int timeouts, 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 initializa-
tion 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.
The callback argument timeouts reports how many times a query timed out during the execution of the given request.
If a query completed successfully, the callback argument abuf points to a result buffer of length alen. If the query did not complete suc-
cessfully, 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 ARES_SEARCH(3)