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/*
SSSD
Async resolver - SRV records parsing
Authors:
Jakub Hrozek <jhrozek@redhat.com>
Copyright (C) Red Hat, Inc 2009
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
* This code is based on other c-ares parsing licensed as follows:
* Copyright 1998 by the Massachusetts Institute of Technology.
*
* 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.
*/
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <arpa/nameser.h>
#include <stdlib.h>
#include <string.h>
#include "ares.h"
/* this drags in some private macros c-ares uses */
#include "ares_dns.h"
#include "ares_parse_srv_reply.h"
int _ares_parse_srv_reply (const unsigned char *abuf, int alen,
struct srv_reply **srv_out, int *nsrvreply)
{
unsigned int qdcount, ancount;
const unsigned char *aptr;
int status, i, rr_type, rr_class, rr_len;
long len;
char *hostname = NULL, *rr_name = NULL;
struct srv_reply *srv = NULL;
/* Set *srv_out to NULL for all failure cases. */
if (srv_out)
*srv_out = NULL;
/* Same with *nsrvreply. */
if (nsrvreply)
*nsrvreply = 0;
/* Give up if abuf doesn't have room for a header. */
if (alen < HFIXEDSZ)
return ARES_EBADRESP;
/* Fetch the question and answer count from the header. */
qdcount = DNS_HEADER_QDCOUNT (abuf);
ancount = DNS_HEADER_ANCOUNT (abuf);
if (qdcount != 1)
return ARES_EBADRESP;
if (ancount == 0)
return ARES_ENODATA;
/* Expand the name from the question, and skip past the question. */
aptr = abuf + HFIXEDSZ;
status = ares_expand_name (aptr, abuf, alen, &hostname, &len);
if (status != ARES_SUCCESS)
return status;
if (aptr + len + QFIXEDSZ > abuf + alen)
{
free (hostname);
return ARES_EBADRESP;
}
aptr += len + QFIXEDSZ;
/* Allocate srv_reply array; ancount gives an upper bound */
srv = malloc ((ancount) * sizeof (struct srv_reply));
if (!srv)
{
free (hostname);
return ARES_ENOMEM;
}
/* Examine each answer resource record (RR) in turn. */
for (i = 0; i < (int) ancount; i++)
{
/* Decode the RR up to the data field. */
status = ares_expand_name (aptr, abuf, alen, &rr_name, &len);
if (status != ARES_SUCCESS)
{
break;
}
aptr += len;
if (aptr + RRFIXEDSZ > abuf + alen)
{
status = ARES_EBADRESP;
break;
}
rr_type = DNS_RR_TYPE (aptr);
rr_class = DNS_RR_CLASS (aptr);
rr_len = DNS_RR_LEN (aptr);
aptr += RRFIXEDSZ;
/* Check if we are really looking at a SRV record */
if (rr_class == C_IN && rr_type == T_SRV)
{
/* parse the SRV record itself */
if (rr_len < 6)
{
status = ARES_EBADRESP;
break;
}
srv[i].priority = ntohs (*((const uint16_t *)aptr));
aptr += sizeof(uint16_t);
srv[i].weight = ntohs (*((const uint16_t *)aptr));
aptr += sizeof(uint16_t);
srv[i].port = ntohs (*((const uint16_t *)aptr));
aptr += sizeof(uint16_t);
status = ares_expand_name (aptr, abuf, alen, &srv[i].host, &len);
if (status != ARES_SUCCESS)
break;
/* Move on to the next record */
aptr += len;
/* Don't lose memory in the next iteration */
free (rr_name);
rr_name = NULL;
}
}
/* clean up on error */
if (status != ARES_SUCCESS)
{
free (srv);
free (hostname);
free (rr_name);
return status;
}
/* everything looks fine, return the data */
*srv_out = srv;
*nsrvreply = ancount;
free (hostname);
free (rr_name);
return status;
}
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