ares_create_query - Compose a single-question DNS query buffer


#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)


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 when it is no longer needed. The parameter max_udp_size should be nonzero to activate EDNS. Usage of ares_create_query with max_udp_size set to zero is equivalent to using ares_mkquery.

Return values

ares_create_query can return any of the following values:

ARES_SUCCESS Construction of the DNS query succeeded.

ARES_ENOTFOUND The query name name refers to a .onion domain name. See RFC 7686.

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.


Added in c-ares 1.10.0

See also

ares_dns_record(3), ares_expand_name(3), ares_free_string(3), ares_mkquery(3)


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