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1 | /* |
2 | * $Id: libnet_build_dns.c,v 1.20 2005/11/29 22:29:57 carlosc 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(u_int16_t h_len, u_int16_t id, u_int16_t flags, | |
45 | u_int16_t num_q, u_int16_t num_anws_rr, u_int16_t num_auth_rr, | |
46 | u_int16_t num_addi_rr, u_int8_t *payload, u_int32_t payload_s, | |
47 | libnet_t *l, libnet_ptag_t ptag) | |
48 | { | |
49 | ||
50 | u_int32_t n, h; | |
51 | u_int 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 | * The sizeof(dns_hdr.h_len) is not counted is the packet size | |
81 | * for TCP packet. | |
82 | * And since this will be ignored for udp packets, let's compute it | |
83 | * anyway. | |
84 | */ | |
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, ((u_int8_t *)&dns_hdr)+ offset, h_len); | |
102 | if (n == -1) | |
103 | { | |
104 | goto bad; | |
105 | } | |
106 | ||
107 | if ((payload && !payload_s) || (!payload && payload_s)) | |
108 | { | |
109 | snprintf(l->err_buf, LIBNET_ERRBUF_SIZE, | |
110 | "%s(): payload inconsistency\n", __func__); | |
111 | goto bad; | |
112 | } | |
113 | ||
114 | if (payload && payload_s) | |
115 | { | |
116 | n = libnet_pblock_append(l, p, payload, payload_s); | |
117 | if (n == -1) | |
118 | { | |
119 | goto bad; | |
120 | } | |
121 | } | |
122 | ||
123 | return (ptag ? ptag : libnet_pblock_update(l, p, h, LIBNET_PBLOCK_DNSV4_H)); | |
124 | bad: | |
125 | libnet_pblock_delete(l, p); | |
126 | return (-1); | |
127 | } | |
128 | ||
129 | /* EOF */ |