.\"
.\" Copyright 2020 Danny Sonnenschein <my.card.god@web.de>
.\"
.\" Permission to use, copy, modify, and distribute this
.\" software and its documentation for any purpose and without
.\" fee is hereby granted, provided that the above copyright
.\" notice appear in all copies and that both that copyright
.\" notice and this permission notice appear in supporting
.\" documentation, and that the name of M.I.T. not be used in
.\" advertising or publicity pertaining to distribution of the
.\" software without specific, written prior permission.
.\" M.I.T. makes no representations about the suitability of
.\" this software for any purpose.  It is provided "as is"
.\" without express or implied warranty.
.\"
.\" SPDX-License-Identifier: MIT
.\"
.TH ARES_PARSE_CAA_REPLY 3 "16 September 2020"
.SH NAME
ares_parse_caa_reply \- Parse a reply to a DNS query of type CAA
.SH SYNOPSIS
.nf
#include <ares.h>

int ares_parse_caa_reply(const unsigned char* \fIabuf\fP, int \fIalen\fP,
                         struct ares_caa_reply **\fIcaa_out\fP);
.fi
.SH DESCRIPTION
The
.BR "ares_parse_caa_reply" 
function parses the response to a query of type CAA into a
linked list (one element per sub-string) of
.IR "struct ares_caa_reply"
The parameters
.I abuf
and
.I 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
.IR caa_out .
It is the caller's responsibility to free the resulting
.IR caa_out
structure when it is no longer needed using the function
.B ares_free_data(3)
.PP
The structure 
.I ares_caa_reply(3)
contains the following fields:
.sp
.in +4n
.nf
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 */
};
.fi
.in
.PP
.SH RETURN VALUES
.BR "ares_parse_caa_reply"
can return any of the following values:
.TP 15
.B ARES_SUCCESS
The response was successfully parsed.
.TP 15
.B ARES_EBADRESP
The response was malformatted.
.TP 15
.B ARES_ENODATA
The response did not contain an answer to the query.
.TP 15
.B ARES_ENOMEM
Memory was exhausted.
.SH EXAMPLE
.nf
#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 *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 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);
  }
.fi
.SH AVAILABILITY
This function was first introduced in c-ares version 1.17.0.
.SH SEE ALSO
.BR ares_query (3)
.BR ares_free_data (3)
.SH AUTHOR
Written by Danny Sonnenschein <my.card.god@web.de>, on behalf of platynum, https://platynum.ch