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1 /*
2  * Copyright (c) 1998-2007 The TCPDUMP project
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that: (1) source code
6  * distributions retain the above copyright notice and this paragraph
7  * in its entirety, and (2) distributions including binary code include
8  * the above copyright notice and this paragraph in its entirety in
9  * the documentation or other materials provided with the distribution.
10  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND
11  * WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT
12  * LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
13  * FOR A PARTICULAR PURPOSE.
14  *
15  * Original code by Carles Kishimoto <carles.kishimoto@gmail.com>
16  */
17 
18 /* \summary: Cisco UniDirectional Link Detection (UDLD) protocol printer */
19 
20 /* specification: RFC 5171 */
21 
22 #ifdef HAVE_CONFIG_H
23 #include "config.h"
24 #endif
25 
26 #include <netdissect-stdinc.h>
27 
28 #include "netdissect.h"
29 #include "extract.h"
30 
31 static const char tstr[] = " [|udld]";
32 
33 #define UDLD_HEADER_LEN			4
34 #define UDLD_DEVICE_ID_TLV		0x0001
35 #define UDLD_PORT_ID_TLV		0x0002
36 #define UDLD_ECHO_TLV			0x0003
37 #define UDLD_MESSAGE_INTERVAL_TLV	0x0004
38 #define UDLD_TIMEOUT_INTERVAL_TLV	0x0005
39 #define UDLD_DEVICE_NAME_TLV		0x0006
40 #define UDLD_SEQ_NUMBER_TLV		0x0007
41 
42 static const struct tok udld_tlv_values[] = {
43     { UDLD_DEVICE_ID_TLV, "Device-ID TLV"},
44     { UDLD_PORT_ID_TLV, "Port-ID TLV"},
45     { UDLD_ECHO_TLV, "Echo TLV"},
46     { UDLD_MESSAGE_INTERVAL_TLV, "Message Interval TLV"},
47     { UDLD_TIMEOUT_INTERVAL_TLV, "Timeout Interval TLV"},
48     { UDLD_DEVICE_NAME_TLV, "Device Name TLV"},
49     { UDLD_SEQ_NUMBER_TLV,"Sequence Number TLV"},
50     { 0, NULL}
51 };
52 
53 static const struct tok udld_code_values[] = {
54     { 0x00, "Reserved"},
55     { 0x01, "Probe message"},
56     { 0x02, "Echo message"},
57     { 0x03, "Flush message"},
58     { 0, NULL}
59 };
60 
61 static const struct tok udld_flags_values[] = {
62     { 0x00, "RT"},
63     { 0x01, "RSY"},
64     { 0, NULL}
65 };
66 
67 /*
68  * UDLD's Protocol Data Unit format:
69  *
70  *  0                   1                   2                   3
71  *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
72  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
73  * | Ver | Opcode  |     Flags     |           Checksum            |
74  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
75  * |               List of TLVs (variable length list)             |
76  * |                              ...                              |
77  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
78  *
79  * TLV format:
80  *
81  *  0                   1                   2                   3
82  *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
83  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
84  * |             TYPE              |            LENGTH             |
85  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
86  * |                             VALUE                             |
87  * |                              ...                              |
88  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
89  *
90  * LENGTH: Length in bytes of the Type, Length, and Value fields.
91  */
92 
93 #define	UDLD_EXTRACT_VERSION(x) (((x)&0xe0)>>5)
94 #define	UDLD_EXTRACT_OPCODE(x) ((x)&0x1f)
95 
96 void
udld_print(netdissect_options * ndo,const u_char * pptr,u_int length)97 udld_print (netdissect_options *ndo, const u_char *pptr, u_int length)
98 {
99     int code, type, len;
100     const u_char *tptr;
101 
102     if (length < UDLD_HEADER_LEN)
103         goto trunc;
104 
105     tptr = pptr;
106 
107     ND_TCHECK2(*tptr, UDLD_HEADER_LEN);
108 
109     code = UDLD_EXTRACT_OPCODE(*tptr);
110 
111     ND_PRINT((ndo, "UDLDv%u, Code %s (%x), Flags [%s] (0x%02x), length %u",
112            UDLD_EXTRACT_VERSION(*tptr),
113            tok2str(udld_code_values, "Reserved", code),
114            code,
115            bittok2str(udld_flags_values, "none", *(tptr+1)),
116            *(tptr+1),
117            length));
118 
119     /*
120      * In non-verbose mode, just print version and opcode type
121      */
122     if (ndo->ndo_vflag < 1) {
123 	return;
124     }
125 
126     ND_PRINT((ndo, "\n\tChecksum 0x%04x (unverified)", EXTRACT_16BITS(tptr+2)));
127 
128     tptr += UDLD_HEADER_LEN;
129 
130     while (tptr < (pptr+length)) {
131 
132         ND_TCHECK2(*tptr, 4);
133 	type = EXTRACT_16BITS(tptr);
134         len  = EXTRACT_16BITS(tptr+2);
135 
136         ND_PRINT((ndo, "\n\t%s (0x%04x) TLV, length %u",
137                tok2str(udld_tlv_values, "Unknown", type),
138                type, len));
139 
140         if (type == 0)
141             goto invalid;
142 
143         /* infinite loop check */
144         if (len <= 4)
145             goto invalid;
146 
147         len -= 4;
148         tptr += 4;
149 
150         ND_TCHECK2(*tptr, len);
151 
152         switch (type) {
153         case UDLD_DEVICE_ID_TLV:
154         case UDLD_PORT_ID_TLV:
155         case UDLD_DEVICE_NAME_TLV:
156             ND_PRINT((ndo, ", "));
157             fn_printzp(ndo, tptr, len, NULL);
158             break;
159 
160         case UDLD_ECHO_TLV:
161             ND_PRINT((ndo, ", "));
162             (void)fn_printn(ndo, tptr, len, NULL);
163             break;
164 
165         case UDLD_MESSAGE_INTERVAL_TLV:
166         case UDLD_TIMEOUT_INTERVAL_TLV:
167             if (len != 1)
168                 goto invalid;
169             ND_PRINT((ndo, ", %us", (*tptr)));
170             break;
171 
172         case UDLD_SEQ_NUMBER_TLV:
173             if (len != 4)
174                 goto invalid;
175             ND_PRINT((ndo, ", %u", EXTRACT_32BITS(tptr)));
176             break;
177 
178         default:
179             break;
180         }
181         tptr += len;
182     }
183 
184     return;
185 
186 invalid:
187     ND_PRINT((ndo, "%s", istr));
188     return;
189 trunc:
190     ND_PRINT((ndo, "%s", tstr));
191 }
192 
193 /*
194  * Local Variables:
195  * c-style: whitesmith
196  * c-basic-offset: 4
197  * End:
198  */
199