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: http://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 #include "netdissect.h"
42 #include "extract.h"
43 #include "ether.h"
44 #include "addrtoname.h"
45
46 static const char tstr[] = " [|loopback]";
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
loopback_message_print(netdissect_options * ndo,const u_char * cp,const u_int len)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 invalid;
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 invalid;
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 invalid;
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 invalid:
101 ND_PRINT((ndo, "%s", istr));
102 ND_TCHECK2(*cp, ep - cp);
103 return;
104 trunc:
105 ND_PRINT((ndo, "%s", tstr));
106 }
107
108 void
loopback_print(netdissect_options * ndo,const u_char * cp,const u_int len)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 invalid;
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 invalid;
126 loopback_message_print(ndo, cp + skipCount, len - 2 - skipCount);
127 return;
128
129 invalid:
130 ND_PRINT((ndo, "%s", istr));
131 ND_TCHECK2(*cp, ep - cp);
132 return;
133 trunc:
134 ND_PRINT((ndo, "%s", tstr));
135 }
136
137