Man page - ares_parse_caa_reply(3)

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Package: libc-ares-dev
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Manual

ARES_PARSE_CAA_REPLY(3)

Library Functions Manual

ARES_PARSE_CAA_REPLY(3)

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.