ares_parse_caa_reply - Parse a reply to a DNS query of type CAA

NAME  SYNOPSIS  DESCRIPTION  RETURN VALUES  EXAMPLE  AVAILABILITY  SEE ALSO  AUTHOR 

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NAME

ares_parse_caa_reply − Parse a reply to a DNS query of type CAA

SYNOPSIS

#include <ares.h>

int ares_parse_caa_reply(const unsigned char* abuf, int alen,
struct ares_caa_reply **caa_out);

DESCRIPTION

The ares_parse_caa_reply function parses the response to a query of type CAA into a linked list (one element per sub-string) of struct ares_caa_reply The parameters abuf and alen give the contents of the response. The result is stored in allocated memory and a pointer to it stored into the variable pointed to by caa_out. It is the caller’s responsibility to free the resulting caa_out structure when it is no longer needed using the function ares_free_data(3)

The structure ares_caa_reply(3) contains the following fields:

struct ares_caa_reply {
struct ares_caa_reply *next;
int critical;
unsigned char *property;
size_t plength; /* plength excludes null */
unsigned char *value;
size_t length; /* length excludes null */
};

RETURN VALUES

ares_parse_caa_reply can return any of the following values:

	ARES_SUCCESS		The response was successfully parsed.
	ARES_EBADRESP		The response was malformatted.
	ARES_ENODATA		The response did not contain an answer to the query.
	ARES_ENOMEM		Memory was exhausted.

EXAMPLE

#include <arpa/inet.h>
#include <time.h>
#include <sys/time.h>
#include <netdb.h>

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

#include "ares.h"

static void dns_callback(void *arg,
int status,
int timeouts,
unsigned char *abuf,
int alen)
{
struct ares_caa_reply *caa_out;
int err;

err = ares_parse_caa_reply (abuf, alen, &caa_out);
if (err == ARES_SUCCESS)
{
struct ares_caa_reply *caa_curr;
for (caa_curr=caa_out; caa_curr; caa_curr=caa_curr->next)
printf ("%s. CAA %i %s \"%s\"\n", arg,
caa_curr->critical,
caa_curr->property,
caa_curr->value);
}
else
{
printf ("err=%i\n", err);
}
ares_free_data (caa_out);
}

static void main_loop(ares_channel_t **channel)
{
int nfds, count;
fd_set readers, writers;
struct timeval tv, *tvp;
while (1)
{
FD_ZERO (&readers);
FD_ZERO (&writers);
nfds = ares_fds (*channel, &readers, &writers);
if (nfds == 0)
break;
tvp = ares_timeout (*channel, NULL, &tv);
count = select (nfds, &readers, &writers, NULL, tvp);
ares_process (*channel, &readers, &writers);
}
}

int main(int argc, char **argv)
{
const char *sversion;
int iversion;
int err;

sversion = ares_version (&iversion);
printf ("c-ares version %s\n", sversion);

char *domain = "wikipedia.org";
if (argc > 1)
domain = argv[1];

ares_channel_t *channel;
if ((err = ares_init (&channel)) != ARES_SUCCESS)
{
printf ("ares_init() failed (%i)\n", err);
exit (EXIT_FAILURE);
}

ares_query (channel, domain,
1, /* ns_c_in */
257, /* T_CAA */
dns_callback, domain);

main_loop (&channel);

ares_destroy (channel);

exit (EXIT_SUCCESS);
}

AVAILABILITY

This function was first introduced in c-ares version 1.17.0.

SEE ALSO

ares_query(3) ares_free_data(3)

AUTHOR

Written by Danny Sonnenschein <[email protected]>, on behalf of platynum, https://platynum.ch

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