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1.1.6

    1: /*
    2:  *  $Id: libnet_build_dns.c,v 1.1.1.2 2013/07/22 11:54:42 misho Exp $
    3:  *
    4:  *  libnet
    5:  *  libnet_build_dns.c - DNS packet assembler
    6:  *
    7:  *  Copyright (c) 1998 - 2004 Mike D. Schiffman <mike@infonexus.com>
    8:  *  All rights reserved.
    9:  *
   10:  * Redistribution and use in source and binary forms, with or without
   11:  * modification, are permitted provided that the following conditions
   12:  * are met:
   13:  * 1. Redistributions of source code must retain the above copyright
   14:  *    notice, this list of conditions and the following disclaimer.
   15:  * 2. Redistributions in binary form must reproduce the above copyright
   16:  *    notice, this list of conditions and the following disclaimer in the
   17:  *    documentation and/or other materials provided with the distribution.
   18:  *
   19:  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   20:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   21:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   22:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   23:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   24:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   25:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   26:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   27:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   28:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   29:  * SUCH DAMAGE.
   30:  *
   31:  */
   32: 
   33: #if (HAVE_CONFIG_H)
   34: #include "../include/config.h"
   35: #endif
   36: #if (!(_WIN32) || (__CYGWIN__)) 
   37: #include "../include/libnet.h"
   38: #else
   39: #include "../include/win32/libnet.h"
   40: #endif
   41: 
   42: 
   43: libnet_ptag_t
   44: libnet_build_dnsv4(uint16_t h_len, uint16_t id, uint16_t flags,
   45:             uint16_t num_q, uint16_t num_anws_rr, uint16_t num_auth_rr,
   46:             uint16_t num_addi_rr, const uint8_t *payload, uint32_t payload_s,
   47:             libnet_t *l, libnet_ptag_t ptag)
   48: {
   49: 
   50:     uint32_t n, h;
   51:     uint offset;
   52:     libnet_pblock_t *p;
   53:     struct libnet_dnsv4_hdr dns_hdr;
   54: 
   55:     if (l == NULL)
   56:     { 
   57:         return (-1);
   58:     } 
   59: 
   60:     if (h_len != LIBNET_UDP_DNSV4_H && h_len != LIBNET_TCP_DNSV4_H)
   61:     {
   62:         snprintf(l->err_buf, LIBNET_ERRBUF_SIZE,
   63:                 "%s(): invalid header length: %d", __func__, h_len);
   64:        return (-1);
   65:     }
   66:     offset = (h_len == LIBNET_UDP_DNSV4_H ? sizeof(dns_hdr.h_len) : 0);
   67:     n = h_len + payload_s;
   68:     h = 0;          /* no checksum */
   69: 
   70:     /*
   71:      *  Find the existing protocol block if a ptag is specified, or create
   72:      *  a new one.
   73:      */
   74:     p = libnet_pblock_probe(l, ptag, n, LIBNET_PBLOCK_DNSV4_H);
   75:     if (p == NULL)
   76:     {
   77:         return (-1);
   78:     }
   79: 
   80:     /*
   81:      * The sizeof(dns_hdr.h_len) is not counted is the packet size
   82:      * for TCP packet.
   83:      * And since this will be ignored for udp packets, let's compute it 
   84:      * anyway.
   85:      */
   86:     memset(&dns_hdr, 0, sizeof(dns_hdr));
   87:     dns_hdr.h_len       = htons(n - sizeof (dns_hdr.h_len));
   88:     dns_hdr.id          = htons(id);
   89:     dns_hdr.flags       = htons(flags);
   90:     dns_hdr.num_q       = htons(num_q);
   91:     dns_hdr.num_answ_rr = htons(num_anws_rr);
   92:     dns_hdr.num_auth_rr = htons(num_auth_rr);
   93:     dns_hdr.num_addi_rr = htons(num_addi_rr);
   94: 
   95:     /*
   96:      * A dirty trick: DNS can be either TCP or UDP based, and depending on
   97:      * that, the header changes. A 'length' field is present in TCP packets,
   98:      * but not in UDP packets. As they are the first 2 bytes of the header,
   99:      * they are skipped if the packet is UDP...
  100:      */
  101:     n = libnet_pblock_append(l, p, ((uint8_t *)&dns_hdr) + offset, h_len);
  102:     if (n == -1)
  103:     {
  104:         goto bad;
  105:     }
  106: 
  107:     /* boilerplate payload sanity check / append macro */
  108:     LIBNET_DO_PAYLOAD(l, p);
  109:  
  110:     return (ptag ? ptag : libnet_pblock_update(l, p, h, LIBNET_PBLOCK_DNSV4_H));
  111: bad:
  112:     libnet_pblock_delete(l, p);
  113:     return (-1);
  114: }
  115: 
  116: /* EOF */