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1 office 1 /*
2 * This module implements decoding of the Loopback Protocol, originally
3 * defined as the Configuration Testing Protocol. It is based on the following
4 * specification:
5 * http://www.mit.edu/people/jhawk/ctp.pdf
6 *
7 * Copyright (c) 2014 The TCPDUMP project
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 COPYRIGHT HOLDERS AND CONTRIBUTORS
20 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
22 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
23 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
24 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
25 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
26 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
27 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
29 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
30 * POSSIBILITY OF SUCH DAMAGE.
31 */
32  
33 #define NETDISSECT_REWORKED
34 #ifdef HAVE_CONFIG_H
35 #include "config.h"
36 #endif
37  
38 #include <tcpdump-stdinc.h>
39  
40 #include "interface.h"
41 #include "extract.h"
42 #include "ether.h"
43 #include "addrtoname.h"
44  
45 static const char tstr[] = " [|loopback]";
46 static const char cstr[] = " (corrupt)";
47  
48 #define LOOPBACK_REPLY 1
49 #define LOOPBACK_FWDDATA 2
50  
51 static const struct tok fcode_str[] = {
52 { LOOPBACK_REPLY, "Reply" },
53 { LOOPBACK_FWDDATA, "Forward Data" },
54 { 0, NULL }
55 };
56  
57 static void
58 loopback_message_print(netdissect_options *ndo, const u_char *cp, const u_int len)
59 {
60 const u_char *ep = cp + len;
61 uint16_t function;
62  
63 if (len < 2)
64 goto corrupt;
65 /* function */
66 ND_TCHECK2(*cp, 2);
67 function = EXTRACT_LE_16BITS(cp);
68 cp += 2;
69 ND_PRINT((ndo, ", %s", tok2str(fcode_str, " invalid (%u)", function)));
70  
71 switch (function) {
72 case LOOPBACK_REPLY:
73 if (len < 4)
74 goto corrupt;
75 /* receipt number */
76 ND_TCHECK2(*cp, 2);
77 ND_PRINT((ndo, ", receipt number %u", EXTRACT_LE_16BITS(cp)));
78 cp += 2;
79 /* data */
80 ND_PRINT((ndo, ", data (%u octets)", len - 4));
81 ND_TCHECK2(*cp, len - 4);
82 break;
83 case LOOPBACK_FWDDATA:
84 if (len < 8)
85 goto corrupt;
86 /* forwarding address */
87 ND_TCHECK2(*cp, ETHER_ADDR_LEN);
88 ND_PRINT((ndo, ", forwarding address %s", etheraddr_string(ndo, cp)));
89 cp += ETHER_ADDR_LEN;
90 /* data */
91 ND_PRINT((ndo, ", data (%u octets)", len - 8));
92 ND_TCHECK2(*cp, len - 8);
93 break;
94 default:
95 ND_TCHECK2(*cp, len - 2);
96 break;
97 }
98 return;
99  
100 corrupt:
101 ND_PRINT((ndo, "%s", cstr));
102 ND_TCHECK2(*cp, ep - cp);
103 return;
104 trunc:
105 ND_PRINT((ndo, "%s", tstr));
106 }
107  
108 void
109 loopback_print(netdissect_options *ndo, const u_char *cp, const u_int len)
110 {
111 const u_char *ep = cp + len;
112 uint16_t skipCount;
113  
114 ND_PRINT((ndo, "Loopback"));
115 if (len < 2)
116 goto corrupt;
117 /* skipCount */
118 ND_TCHECK2(*cp, 2);
119 skipCount = EXTRACT_LE_16BITS(cp);
120 cp += 2;
121 ND_PRINT((ndo, ", skipCount %u", skipCount));
122 if (skipCount % 8)
123 ND_PRINT((ndo, " (bogus)"));
124 if (skipCount > len - 2)
125 goto corrupt;
126 loopback_message_print(ndo, cp + skipCount, len - 2 - skipCount);
127 return;
128  
129 corrupt:
130 ND_PRINT((ndo, "%s", cstr));
131 ND_TCHECK2(*cp, ep - cp);
132 return;
133 trunc:
134 ND_PRINT((ndo, "%s", tstr));
135 }
136