1 /*
2 * $Id: libnet_build_dns.c,v 1.10 2004/04/13 17:32:28 mike 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
libnet_build_dnsv4(uint16_t h_len,uint16_t id,uint16_t flags,uint16_t num_q,uint16_t num_anws_rr,uint16_t num_auth_rr,uint16_t num_addi_rr,const uint8_t * payload,uint32_t payload_s,libnet_t * l,libnet_ptag_t ptag)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 */
117