1 /*
2 * Copyright (c) 2014 The TCPDUMP project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
15 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
16 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
17 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
18 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
20 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
21 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
22 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
24 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
25 * POSSIBILITY OF SUCH DAMAGE.
26 */
27
28 /* \summary: Loopback Protocol printer */
29
30 /*
31 * originally defined as the Ethernet Configuration Testing Protocol.
32 * specification:
33 * https://web.archive.org/web/20060919181108/http://www.mit.edu/people/jhawk/ctp.pdf
34 */
35
36 #include <config.h>
37
38 #include "netdissect-stdinc.h"
39
40 #define ND_LONGJMP_FROM_TCHECK
41 #include "netdissect.h"
42 #include "extract.h"
43 #include "addrtoname.h"
44
45
46 #define LOOPBACK_REPLY 1
47 #define LOOPBACK_FWDDATA 2
48
49 static const struct tok fcode_str[] = {
50 { LOOPBACK_REPLY, "Reply" },
51 { LOOPBACK_FWDDATA, "Forward Data" },
52 { 0, NULL }
53 };
54
55 static void
loopback_message_print(netdissect_options * ndo,const u_char * cp,u_int len)56 loopback_message_print(netdissect_options *ndo,
57 const u_char *cp, u_int len)
58 {
59 uint16_t function;
60
61 if (len < 2)
62 goto invalid;
63 /* function */
64 function = GET_LE_U_2(cp);
65 cp += 2;
66 len -= 2;
67 ND_PRINT(", %s", tok2str(fcode_str, " invalid (%u)", function));
68
69 switch (function) {
70 case LOOPBACK_REPLY:
71 if (len < 2)
72 goto invalid;
73 /* receipt number */
74 ND_PRINT(", receipt number %u", GET_LE_U_2(cp));
75 cp += 2;
76 len -= 2;
77 /* data */
78 ND_PRINT(", data (%u octets)", len);
79 ND_TCHECK_LEN(cp, len);
80 break;
81 case LOOPBACK_FWDDATA:
82 if (len < MAC_ADDR_LEN)
83 goto invalid;
84 /* forwarding address */
85 ND_PRINT(", forwarding address %s", GET_ETHERADDR_STRING(cp));
86 cp += MAC_ADDR_LEN;
87 len -= MAC_ADDR_LEN;
88 /* data */
89 ND_PRINT(", data (%u octets)", len);
90 ND_TCHECK_LEN(cp, len);
91 break;
92 default:
93 ND_TCHECK_LEN(cp, len);
94 break;
95 }
96 return;
97
98 invalid:
99 nd_print_invalid(ndo);
100 ND_TCHECK_LEN(cp, len);
101 }
102
103 void
loopback_print(netdissect_options * ndo,const u_char * cp,u_int len)104 loopback_print(netdissect_options *ndo,
105 const u_char *cp, u_int len)
106 {
107 uint16_t skipCount;
108
109 ndo->ndo_protocol = "loopback";
110 ND_PRINT("Loopback");
111 if (len < 2)
112 goto invalid;
113 /* skipCount */
114 skipCount = GET_LE_U_2(cp);
115 cp += 2;
116 len -= 2;
117 ND_PRINT(", skipCount %u", skipCount);
118 if (skipCount % 8)
119 ND_PRINT(" (bogus)");
120 if (skipCount > len)
121 goto invalid;
122 /* the octets to skip */
123 ND_TCHECK_LEN(cp, skipCount);
124 cp += skipCount;
125 len -= skipCount;
126 /* the first message to decode */
127 loopback_message_print(ndo, cp, len);
128 return;
129
130 invalid:
131 nd_print_invalid(ndo);
132 ND_TCHECK_LEN(cp, len);
133 }
134
135