ares_create_query(3) [centos man page]
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_GETHOSTBYNAME(3) Library Functions Manual ARES_GETHOSTBYNAME(3) NAME
ares_gethostbyname - Initiate a host query by name SYNOPSIS
#include <ares.h> typedef void (*ares_host_callback)(void *arg, int status, int timeouts, struct hostent *hostent) void ares_gethostbyname(ares_channel channel, const char *name, int family, ares_host_callback callback, void *arg) DESCRIPTION
The ares_gethostbyname function initiates a host query by name on the name service channel identified by channel. The parameter name gives the hostname as a NUL-terminated C string, and family gives the desired type of address for the resulting host entry. 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_gethostbyname 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 find addresses of type family. ARES_EBADNAME The hostname name is composed entirely of numbers and periods, but is not a valid representation of an Internet address. ARES_ENOTFOUND The address addr was not found. 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. 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_gethostbyaddr(3) AUTHOR
Greg Hudson, MIT Information Systems Copyright 1998 by the Massachusetts Institute of Technology. 25 July 1998 ARES_GETHOSTBYNAME(3)