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/* Copyright (C) 2004 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2004.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#include <errno.h>
#include <netdb.h>
#include <resolv.h>
#include <stdlib.h>
#include <arpa/nameser.h>
#include <nsswitch.h>
#if PACKETSZ > 65536
# define MAXPACKET PACKETSZ
#else
# define MAXPACKET 65536
#endif
/* We need this time later. */
typedef union querybuf
{
HEADER hdr;
unsigned char buf[MAXPACKET];
} querybuf;
enum nss_status
_nss_dns_getcanonname_r (const char *name, char *buffer, size_t buflen,
char **result,int *errnop, int *h_errnop)
{
/* Just an alibi buffer, res_nquery will allocate a real buffer for
us. */
unsigned char buf[20];
union
{
querybuf *buf;
unsigned char *ptr;
} ansp = { .ptr = buf };
enum nss_status status;
int r = __libc_res_nquery (&_res, name, ns_c_in, ns_t_cname,
buf, sizeof (buf), &ansp.ptr);
if (r > 0)
{
/* We need to decode the response. Just one question record.
And if we got no answers we bail out, too. */
if (ansp.buf->hdr.qdcount != htons (1)
|| ansp.buf->hdr.ancount == 0)
goto unavail;
/* Beginning and end of the buffer with query, answer, and the
rest. */
unsigned char *ptr = &ansp.buf->buf[sizeof (HEADER)];
unsigned char *endptr = ansp.ptr + r;
/* Skip over the query. This is the name, type, and class. */
int s = __dn_skipname (ptr, endptr);
if (s < 0)
goto unavail;
/* Skip over the name and the two 16-bit values containing type
and class. */
ptr += s + 2 * sizeof (uint16_t);
/* Now the reply. First again the name from the query, then
type, class, TTL, and the length of the RDATA. */
s = __dn_skipname (ptr, endptr);
if (s < 0)
goto unavail;
ptr += s;
/* Check whether type and class match. */
if (*(uint16_t *) ptr != htons (ns_t_cname))
goto unavail;
ptr += sizeof (uint16_t);
if (*(uint16_t *) ptr != htons (ns_c_in))
goto unavail;
/* Also skip over the TTL and rdata length. */
ptr += sizeof (uint16_t) + sizeof (uint32_t) + sizeof (int16_t);
/* Now the name we are looking for. */
s = __dn_expand (ansp.buf->buf, endptr, ptr, buffer, buflen);
if (s < 0)
{
if (errno != EMSGSIZE)
goto unavail;
/* The buffer is too small. */
*errnop = ERANGE;
status = NSS_STATUS_TRYAGAIN;
h_errno = NETDB_INTERNAL;
}
else
{
/* Success. */
*result = buffer;
status = NSS_STATUS_SUCCESS;
}
}
else if (h_errno == TRY_AGAIN)
{
again:
status = NSS_STATUS_TRYAGAIN;
*errnop = errno;
}
else
{
unavail:
status = NSS_STATUS_UNAVAIL;
*errnop = errno;
}
*h_errnop = h_errno;
if (ansp.ptr != buf)
free (ansp.ptr);
return status;
}
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