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#include <sys/cdefs.h>
29#ifndef lint
30__RCSID("$NetBSD: print-loopback.c,v 1.5 2023/08/17 20:19:40 christos Exp $");
31#endif
32
33/* \summary: Loopback Protocol printer */
34
35/*
36 * originally defined as the Ethernet Configuration Testing Protocol.
37 * specification: https://www.mit.edu/people/jhawk/ctp.pdf
38 */
39
40#ifdef HAVE_CONFIG_H
41#include <config.h>
42#endif
43
44#include "netdissect-stdinc.h"
45
46#define ND_LONGJMP_FROM_TCHECK
47#include "netdissect.h"
48#include "extract.h"
49#include "addrtoname.h"
50
51
52#define LOOPBACK_REPLY   1
53#define LOOPBACK_FWDDATA 2
54
55static const struct tok fcode_str[] = {
56	{ LOOPBACK_REPLY,   "Reply"        },
57	{ LOOPBACK_FWDDATA, "Forward Data" },
58	{ 0, NULL }
59};
60
61static void
62loopback_message_print(netdissect_options *ndo,
63                       const u_char *cp, u_int len)
64{
65	uint16_t function;
66
67	if (len < 2)
68		goto invalid;
69	/* function */
70	function = GET_LE_U_2(cp);
71	cp += 2;
72	len -= 2;
73	ND_PRINT(", %s", tok2str(fcode_str, " invalid (%u)", function));
74
75	switch (function) {
76		case LOOPBACK_REPLY:
77			if (len < 2)
78				goto invalid;
79			/* receipt number */
80			ND_PRINT(", receipt number %u", GET_LE_U_2(cp));
81			cp += 2;
82			len -= 2;
83			/* data */
84			ND_PRINT(", data (%u octets)", len);
85			ND_TCHECK_LEN(cp, len);
86			break;
87		case LOOPBACK_FWDDATA:
88			if (len < MAC_ADDR_LEN)
89				goto invalid;
90			/* forwarding address */
91			ND_PRINT(", forwarding address %s", GET_ETHERADDR_STRING(cp));
92			cp += MAC_ADDR_LEN;
93			len -= MAC_ADDR_LEN;
94			/* data */
95			ND_PRINT(", data (%u octets)", len);
96			ND_TCHECK_LEN(cp, len);
97			break;
98		default:
99			ND_TCHECK_LEN(cp, len);
100			break;
101	}
102	return;
103
104invalid:
105	nd_print_invalid(ndo);
106	ND_TCHECK_LEN(cp, len);
107}
108
109void
110loopback_print(netdissect_options *ndo,
111               const u_char *cp, u_int len)
112{
113	uint16_t skipCount;
114
115	ndo->ndo_protocol = "loopback";
116	ND_PRINT("Loopback");
117	if (len < 2)
118		goto invalid;
119	/* skipCount */
120	skipCount = GET_LE_U_2(cp);
121	cp += 2;
122	len -= 2;
123	ND_PRINT(", skipCount %u", skipCount);
124	if (skipCount % 8)
125		ND_PRINT(" (bogus)");
126	if (skipCount > len)
127		goto invalid;
128	/* the octets to skip */
129	ND_TCHECK_LEN(cp, skipCount);
130	cp += skipCount;
131	len -= skipCount;
132	/* the first message to decode */
133	loopback_message_print(ndo, cp, len);
134	return;
135
136invalid:
137	nd_print_invalid(ndo);
138	ND_TCHECK_LEN(cp, len);
139}
140
141