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 #include <sys/cdefs.h>
34 #ifndef lint
35 __RCSID("$NetBSD: print-loopback.c,v 1.2 2014/11/20 03:05:03 christos Exp $");
36 #endif
37
38 #define NETDISSECT_REWORKED
39 #ifdef HAVE_CONFIG_H
40 #include "config.h"
41 #endif
42
43 #include <tcpdump-stdinc.h>
44
45 #include "interface.h"
46 #include "extract.h"
47 #include "ether.h"
48 #include "addrtoname.h"
49
50 static const char tstr[] = " [|loopback]";
51 static const char cstr[] = " (corrupt)";
52
53 #define LOOPBACK_REPLY 1
54 #define LOOPBACK_FWDDATA 2
55
56 static const struct tok fcode_str[] = {
57 { LOOPBACK_REPLY, "Reply" },
58 { LOOPBACK_FWDDATA, "Forward Data" },
59 { 0, NULL }
60 };
61
62 static void
loopback_message_print(netdissect_options * ndo,const u_char * cp,const u_int len)63 loopback_message_print(netdissect_options *ndo, const u_char *cp, const u_int len)
64 {
65 const u_char *ep = cp + len;
66 uint16_t function;
67
68 if (len < 2)
69 goto corrupt;
70 /* function */
71 ND_TCHECK2(*cp, 2);
72 function = EXTRACT_LE_16BITS(cp);
73 cp += 2;
74 ND_PRINT((ndo, ", %s", tok2str(fcode_str, " invalid (%u)", function)));
75
76 switch (function) {
77 case LOOPBACK_REPLY:
78 if (len < 4)
79 goto corrupt;
80 /* receipt number */
81 ND_TCHECK2(*cp, 2);
82 ND_PRINT((ndo, ", receipt number %u", EXTRACT_LE_16BITS(cp)));
83 cp += 2;
84 /* data */
85 ND_PRINT((ndo, ", data (%u octets)", len - 4));
86 ND_TCHECK2(*cp, len - 4);
87 break;
88 case LOOPBACK_FWDDATA:
89 if (len < 8)
90 goto corrupt;
91 /* forwarding address */
92 ND_TCHECK2(*cp, ETHER_ADDR_LEN);
93 ND_PRINT((ndo, ", forwarding address %s", etheraddr_string(ndo, cp)));
94 cp += ETHER_ADDR_LEN;
95 /* data */
96 ND_PRINT((ndo, ", data (%u octets)", len - 8));
97 ND_TCHECK2(*cp, len - 8);
98 break;
99 default:
100 ND_TCHECK2(*cp, len - 2);
101 break;
102 }
103 return;
104
105 corrupt:
106 ND_PRINT((ndo, "%s", cstr));
107 ND_TCHECK2(*cp, ep - cp);
108 return;
109 trunc:
110 ND_PRINT((ndo, "%s", tstr));
111 }
112
113 void
loopback_print(netdissect_options * ndo,const u_char * cp,const u_int len)114 loopback_print(netdissect_options *ndo, const u_char *cp, const u_int len)
115 {
116 const u_char *ep = cp + len;
117 uint16_t skipCount;
118
119 ND_PRINT((ndo, "Loopback"));
120 if (len < 2)
121 goto corrupt;
122 /* skipCount */
123 ND_TCHECK2(*cp, 2);
124 skipCount = EXTRACT_LE_16BITS(cp);
125 cp += 2;
126 ND_PRINT((ndo, ", skipCount %u", skipCount));
127 if (skipCount % 8)
128 ND_PRINT((ndo, " (bogus)"));
129 if (skipCount > len - 2)
130 goto corrupt;
131 loopback_message_print(ndo, cp + skipCount, len - 2 - skipCount);
132 return;
133
134 corrupt:
135 ND_PRINT((ndo, "%s", cstr));
136 ND_TCHECK2(*cp, ep - cp);
137 return;
138 trunc:
139 ND_PRINT((ndo, "%s", tstr));
140 }
141
142