/* 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 "ares_setup.h"

#ifdef HAVE_NETINET_IN_H

#  include <netinet/in.h>

#endif

#ifdef HAVE_ARPA_NAMESER_H

#  include <arpa/nameser.h>

#else

#  include "nameser.h"

#endif

#ifdef HAVE_ARPA_NAMESER_COMPAT_H

#  include <arpa/nameser_compat.h>

#endif

#include "ares.h"

#include "ares_dns.h"

#include "ares_private.h"

#ifndef T_OPT

#  define T_OPT  41 /* EDNS0 option (meta-RR) */

#endif

/* Header format, from RFC 1035:

 *                                  1  1  1  1  1  1

 *    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5

 *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

 *  |                      ID                       |

 *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

 *  |QR|   Opcode  |AA|TC|RD|RA|   Z    |   RCODE   |

 *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

 *  |                    QDCOUNT                    |

 *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

 *  |                    ANCOUNT                    |

 *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

 *  |                    NSCOUNT                    |

 *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

 *  |                    ARCOUNT                    |

 *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

 *

 * AA, TC, RA, and RCODE are only set in responses.  Brief description

 * of the remaining fields:

 *      ID      Identifier to match responses with queries

 *      QR      Query (0) or response (1)

 *      Opcode  For our purposes, always QUERY

 *      RD      Recursion desired

 *      Z       Reserved (zero)

 *      QDCOUNT Number of queries

 *      ANCOUNT Number of answers

 *      NSCOUNT Number of name server records

 *      ARCOUNT Number of additional records

 *

 * Question format, from RFC 1035:

 *                                  1  1  1  1  1  1

 *    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5

 *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

 *  |                                               |

 *  /                     QNAME                     /

 *  /                                               /

 *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

 *  |                     QTYPE                     |

 *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

 *  |                     QCLASS                    |

 *  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

 *

 * The query name is encoded as a series of labels, each represented

 * as a one-byte length (maximum 63) followed by the text of the

 * label.  The list is terminated by a label of length zero (which can

 * be thought of as the root domain).

 */

int ares_create_query(const char *name, int dnsclass, int type,

                      unsigned short id, int rd, unsigned char **bufp,

                      int *buflenp, int max_udp_size)

{

  size_t len;

  unsigned char *q;

  const char *p;

  size_t buflen;

  unsigned char *buf;

  /* Set our results early, in case we bail out early with an error. */

  *buflenp = 0;

  *bufp = NULL;

  /* Allocate a memory area for the maximum size this packet might need. +2

   * is for the length byte and zero termination if no dots or ecscaping is

   * used.

   */

  len = strlen(name) + 2 + HFIXEDSZ + QFIXEDSZ +

    (max_udp_size ? EDNSFIXEDSZ : 0);

  buf = ares_malloc(len);

  if (!buf)

    return ARES_ENOMEM;

  /* Set up the header. */

  q = buf;

  memset(q, 0, HFIXEDSZ);

  DNS_HEADER_SET_QID(q, id);

  DNS_HEADER_SET_OPCODE(q, QUERY);

  if (rd) {

    DNS_HEADER_SET_RD(q, 1);

  }

  else {

    DNS_HEADER_SET_RD(q, 0);

  }

  DNS_HEADER_SET_QDCOUNT(q, 1);

  if (max_udp_size) {

      DNS_HEADER_SET_ARCOUNT(q, 1);

  }

  /* A name of "." is a screw case for the loop below, so adjust it. */

  if (strcmp(name, ".") == 0)

    name++;

  /* Start writing out the name after the header. */

  q += HFIXEDSZ;

  while (*name)

    {

      if (*name == '.') {

        ares_free (buf);

        return ARES_EBADNAME;

      }

      /* Count the number of bytes in this label. */

      len = 0;

      for (p = name; *p && *p != '.'; p++)

        {

          if (*p == '\\' && *(p + 1) != 0)

            p++;

          len++;

        }

      if (len > MAXLABEL) {

        ares_free (buf);

        return ARES_EBADNAME;

      }

      /* Encode the length and copy the data. */

      *q++ = (unsigned char)len;

      for (p = name; *p && *p != '.'; p++)

        {

          if (*p == '\\' && *(p + 1) != 0)

            p++;

          *q++ = *p;

        }

      /* Go to the next label and repeat, unless we hit the end. */

      if (!*p)

        break;

      name = p + 1;

    }

  /* Add the zero-length label at the end. */

  *q++ = 0;

  /* Finish off the question with the type and class. */

  DNS_QUESTION_SET_TYPE(q, type);

  DNS_QUESTION_SET_CLASS(q, dnsclass);

  q += QFIXEDSZ;

  if (max_udp_size)

  {

      memset(q, 0, EDNSFIXEDSZ);

      q++;

      DNS_RR_SET_TYPE(q, T_OPT);

      DNS_RR_SET_CLASS(q, max_udp_size);

      q += (EDNSFIXEDSZ-1);

  }

  buflen = (q - buf);

  /* Reject names that are longer than the maximum of 255 bytes that's

   * specified in RFC 1035 ("To simplify implementations, the total length of

   * a domain name (i.e., label octets and label length octets) is restricted

   * to 255 octets or less."). */

  if (buflen > (MAXCDNAME + HFIXEDSZ + QFIXEDSZ +

                (max_udp_size ? EDNSFIXEDSZ : 0))) {

    ares_free (buf);

    return ARES_EBADNAME;

  }

  /* we know this fits in an int at this point */

  *buflenp = (int) buflen;

  *bufp = buf;

  return ARES_SUCCESS;

}