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: https://www.mit.edu/people/jhawk/ctp.pdf
33 */
34
35#ifdef HAVE_CONFIG_H
36#include <config.h>
37#endif
38
39#include "netdissect-stdinc.h"
40
41#define ND_LONGJMP_FROM_TCHECK
42#include "netdissect.h"
43#include "extract.h"
44#include "addrtoname.h"
45
46
47#define LOOPBACK_REPLY   1
48#define LOOPBACK_FWDDATA 2
49
50static const struct tok fcode_str[] = {
51	{ LOOPBACK_REPLY,   "Reply"        },
52	{ LOOPBACK_FWDDATA, "Forward Data" },
53	{ 0, NULL }
54};
55
56static void
57loopback_message_print(netdissect_options *ndo,
58                       const u_char *cp, u_int len)
59{
60	uint16_t function;
61
62	if (len < 2)
63		goto invalid;
64	/* function */
65	function = GET_LE_U_2(cp);
66	cp += 2;
67	len -= 2;
68	ND_PRINT(", %s", tok2str(fcode_str, " invalid (%u)", function));
69
70	switch (function) {
71		case LOOPBACK_REPLY:
72			if (len < 2)
73				goto invalid;
74			/* receipt number */
75			ND_PRINT(", receipt number %u", GET_LE_U_2(cp));
76			cp += 2;
77			len -= 2;
78			/* data */
79			ND_PRINT(", data (%u octets)", len);
80			ND_TCHECK_LEN(cp, len);
81			break;
82		case LOOPBACK_FWDDATA:
83			if (len < MAC_ADDR_LEN)
84				goto invalid;
85			/* forwarding address */
86			ND_PRINT(", forwarding address %s", GET_ETHERADDR_STRING(cp));
87			cp += MAC_ADDR_LEN;
88			len -= MAC_ADDR_LEN;
89			/* data */
90			ND_PRINT(", data (%u octets)", len);
91			ND_TCHECK_LEN(cp, len);
92			break;
93		default:
94			ND_TCHECK_LEN(cp, len);
95			break;
96	}
97	return;
98
99invalid:
100	nd_print_invalid(ndo);
101	ND_TCHECK_LEN(cp, len);
102}
103
104void
105loopback_print(netdissect_options *ndo,
106               const u_char *cp, u_int len)
107{
108	uint16_t skipCount;
109
110	ndo->ndo_protocol = "loopback";
111	ND_PRINT("Loopback");
112	if (len < 2)
113		goto invalid;
114	/* skipCount */
115	skipCount = GET_LE_U_2(cp);
116	cp += 2;
117	len -= 2;
118	ND_PRINT(", skipCount %u", skipCount);
119	if (skipCount % 8)
120		ND_PRINT(" (bogus)");
121	if (skipCount > len)
122		goto invalid;
123	/* the octets to skip */
124	ND_TCHECK_LEN(cp, skipCount);
125	cp += skipCount;
126	len -= skipCount;
127	/* the first message to decode */
128	loopback_message_print(ndo, cp, len);
129	return;
130
131invalid:
132	nd_print_invalid(ndo);
133	ND_TCHECK_LEN(cp, len);
134}
135
136