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Annotation of embedaddon/libnet/src/libnet_build_dns.c, revision 1.1.1.3

1.1       misho       1: /*
1.1.1.2   misho       2:  *  $Id: libnet_build_dns.c,v 1.10 2004/04/13 17:32:28 mike Exp $
1.1       misho       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: 
1.1.1.3 ! misho      33: #include "common.h"
1.1       misho      34: 
                     35: 
                     36: libnet_ptag_t
1.1.1.2   misho      37: libnet_build_dnsv4(uint16_t h_len, uint16_t id, uint16_t flags,
                     38:             uint16_t num_q, uint16_t num_anws_rr, uint16_t num_auth_rr,
                     39:             uint16_t num_addi_rr, const uint8_t *payload, uint32_t payload_s,
1.1       misho      40:             libnet_t *l, libnet_ptag_t ptag)
                     41: {
                     42: 
1.1.1.2   misho      43:     uint32_t n, h;
1.1.1.3 ! misho      44:     uint32_t offset;
1.1       misho      45:     libnet_pblock_t *p;
                     46:     struct libnet_dnsv4_hdr dns_hdr;
                     47: 
                     48:     if (l == NULL)
                     49:     { 
                     50:         return (-1);
                     51:     } 
                     52: 
                     53:     if (h_len != LIBNET_UDP_DNSV4_H && h_len != LIBNET_TCP_DNSV4_H)
                     54:     {
                     55:         snprintf(l->err_buf, LIBNET_ERRBUF_SIZE,
                     56:                 "%s(): invalid header length: %d", __func__, h_len);
                     57:        return (-1);
                     58:     }
                     59:     offset = (h_len == LIBNET_UDP_DNSV4_H ? sizeof(dns_hdr.h_len) : 0);
                     60:     n = h_len + payload_s;
                     61:     h = 0;          /* no checksum */
                     62: 
                     63:     /*
                     64:      *  Find the existing protocol block if a ptag is specified, or create
                     65:      *  a new one.
                     66:      */
                     67:     p = libnet_pblock_probe(l, ptag, n, LIBNET_PBLOCK_DNSV4_H);
                     68:     if (p == NULL)
                     69:     {
                     70:         return (-1);
                     71:     }
1.1.1.2   misho      72: 
1.1       misho      73:     /*
                     74:      * The sizeof(dns_hdr.h_len) is not counted is the packet size
                     75:      * for TCP packet.
                     76:      * And since this will be ignored for udp packets, let's compute it 
                     77:      * anyway.
                     78:      */
1.1.1.2   misho      79:     memset(&dns_hdr, 0, sizeof(dns_hdr));
1.1.1.3 ! misho      80:     dns_hdr.h_len       = htons((u_short)(n - sizeof (dns_hdr.h_len)));
1.1       misho      81:     dns_hdr.id          = htons(id);
                     82:     dns_hdr.flags       = htons(flags);
                     83:     dns_hdr.num_q       = htons(num_q);
                     84:     dns_hdr.num_answ_rr = htons(num_anws_rr);
                     85:     dns_hdr.num_auth_rr = htons(num_auth_rr);
                     86:     dns_hdr.num_addi_rr = htons(num_addi_rr);
                     87: 
                     88:     /*
                     89:      * A dirty trick: DNS can be either TCP or UDP based, and depending on
                     90:      * that, the header changes. A 'length' field is present in TCP packets,
                     91:      * but not in UDP packets. As they are the first 2 bytes of the header,
                     92:      * they are skipped if the packet is UDP...
                     93:      */
1.1.1.2   misho      94:     n = libnet_pblock_append(l, p, ((uint8_t *)&dns_hdr) + offset, h_len);
1.1       misho      95:     if (n == -1)
                     96:     {
                     97:         goto bad;
                     98:     }
                     99: 
1.1.1.2   misho     100:     /* boilerplate payload sanity check / append macro */
                    101:     LIBNET_DO_PAYLOAD(l, p);
1.1       misho     102:  
                    103:     return (ptag ? ptag : libnet_pblock_update(l, p, h, LIBNET_PBLOCK_DNSV4_H));
                    104: bad:
                    105:     libnet_pblock_delete(l, p);
                    106:     return (-1);
                    107: }
                    108: 
1.1.1.3 ! misho     109: /**
        !           110:  * Local Variables:
        !           111:  *  indent-tabs-mode: nil
        !           112:  *  c-file-style: "stroustrup"
        !           113:  * End:
        !           114:  */