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1 office 1 /* $OpenBSD: print-gre.c,v 1.6 2002/10/30 03:04:04 fgsch Exp $ */
2  
3 /*
4 * Copyright (c) 2002 Jason L. Wright (jason@thought.net)
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. All advertising materials mentioning features or use of this software
16 * must display the following acknowledgement:
17 * This product includes software developed by Jason L. Wright
18 * 4. The name of the author may not be used to endorse or promote products
19 * derived from this software without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
22 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
23 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
24 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
25 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
26 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
27 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
29 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
30 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
31 * POSSIBILITY OF SUCH DAMAGE.
32 */
33  
34 /*
35 * tcpdump filter for GRE - Generic Routing Encapsulation
36 * RFC1701 (GRE), RFC1702 (GRE IPv4), and RFC2637 (Enhanced GRE)
37 */
38  
39 #define NETDISSECT_REWORKED
40 #ifdef HAVE_CONFIG_H
41 #include "config.h"
42 #endif
43  
44 #include <tcpdump-stdinc.h>
45  
46 #include <string.h>
47  
48 #include "interface.h"
49 #include "extract.h"
50 #include "ethertype.h"
51  
52 static const char tstr[] = "[|gre]";
53  
54 #define GRE_CP 0x8000 /* checksum present */
55 #define GRE_RP 0x4000 /* routing present */
56 #define GRE_KP 0x2000 /* key present */
57 #define GRE_SP 0x1000 /* sequence# present */
58 #define GRE_sP 0x0800 /* source routing */
59 #define GRE_RECRS 0x0700 /* recursion count */
60 #define GRE_AP 0x0080 /* acknowledgment# present */
61  
62 static const struct tok gre_flag_values[] = {
63 { GRE_CP, "checksum present"},
64 { GRE_RP, "routing present"},
65 { GRE_KP, "key present"},
66 { GRE_SP, "sequence# present"},
67 { GRE_sP, "source routing present"},
68 { GRE_RECRS, "recursion count"},
69 { GRE_AP, "ack present"},
70 { 0, NULL }
71 };
72  
73 #define GRE_VERS_MASK 0x0007 /* protocol version */
74  
75 /* source route entry types */
76 #define GRESRE_IP 0x0800 /* IP */
77 #define GRESRE_ASN 0xfffe /* ASN */
78  
79 static void gre_print_0(netdissect_options *, const u_char *, u_int);
80 static void gre_print_1(netdissect_options *, const u_char *, u_int);
81 static void gre_sre_print(netdissect_options *, uint16_t, uint8_t, uint8_t, const u_char *, u_int);
82 static void gre_sre_ip_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
83 static void gre_sre_asn_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
84  
85 void
86 gre_print(netdissect_options *ndo, const u_char *bp, u_int length)
87 {
88 u_int len = length, vers;
89  
90 if (len < 2) {
91 ND_PRINT((ndo, "%s", tstr));
92 return;
93 }
94 vers = EXTRACT_16BITS(bp) & GRE_VERS_MASK;
95 ND_PRINT((ndo, "GREv%u",vers));
96  
97 switch(vers) {
98 case 0:
99 gre_print_0(ndo, bp, len);
100 break;
101 case 1:
102 gre_print_1(ndo, bp, len);
103 break;
104 default:
105 ND_PRINT((ndo, " ERROR: unknown-version"));
106 break;
107 }
108 }
109  
110 static void
111 gre_print_0(netdissect_options *ndo, const u_char *bp, u_int length)
112 {
113 u_int len = length;
114 uint16_t flags, prot;
115  
116 flags = EXTRACT_16BITS(bp);
117 if (ndo->ndo_vflag)
118 ND_PRINT((ndo, ", Flags [%s]",
119 bittok2str(gre_flag_values,"none",flags)));
120  
121 len -= 2;
122 bp += 2;
123  
124 if (len < 2)
125 goto trunc;
126 prot = EXTRACT_16BITS(bp);
127 len -= 2;
128 bp += 2;
129  
130 if ((flags & GRE_CP) | (flags & GRE_RP)) {
131 if (len < 2)
132 goto trunc;
133 if (ndo->ndo_vflag)
134 ND_PRINT((ndo, ", sum 0x%x", EXTRACT_16BITS(bp)));
135 bp += 2;
136 len -= 2;
137  
138 if (len < 2)
139 goto trunc;
140 ND_PRINT((ndo, ", off 0x%x", EXTRACT_16BITS(bp)));
141 bp += 2;
142 len -= 2;
143 }
144  
145 if (flags & GRE_KP) {
146 if (len < 4)
147 goto trunc;
148 ND_PRINT((ndo, ", key=0x%x", EXTRACT_32BITS(bp)));
149 bp += 4;
150 len -= 4;
151 }
152  
153 if (flags & GRE_SP) {
154 if (len < 4)
155 goto trunc;
156 ND_PRINT((ndo, ", seq %u", EXTRACT_32BITS(bp)));
157 bp += 4;
158 len -= 4;
159 }
160  
161 if (flags & GRE_RP) {
162 for (;;) {
163 uint16_t af;
164 uint8_t sreoff;
165 uint8_t srelen;
166  
167 if (len < 4)
168 goto trunc;
169 af = EXTRACT_16BITS(bp);
170 sreoff = *(bp + 2);
171 srelen = *(bp + 3);
172 bp += 4;
173 len -= 4;
174  
175 if (af == 0 && srelen == 0)
176 break;
177  
178 gre_sre_print(ndo, af, sreoff, srelen, bp, len);
179  
180 if (len < srelen)
181 goto trunc;
182 bp += srelen;
183 len -= srelen;
184 }
185 }
186  
187 if (ndo->ndo_eflag)
188 ND_PRINT((ndo, ", proto %s (0x%04x)",
189 tok2str(ethertype_values,"unknown",prot),
190 prot));
191  
192 ND_PRINT((ndo, ", length %u",length));
193  
194 if (ndo->ndo_vflag < 1)
195 ND_PRINT((ndo, ": ")); /* put in a colon as protocol demarc */
196 else
197 ND_PRINT((ndo, "\n\t")); /* if verbose go multiline */
198  
199 switch (prot) {
200 case ETHERTYPE_IP:
201 ip_print(ndo, bp, len);
202 break;
203 case ETHERTYPE_IPV6:
204 ip6_print(ndo, bp, len);
205 break;
206 case ETHERTYPE_MPLS:
207 mpls_print(ndo, bp, len);
208 break;
209 case ETHERTYPE_IPX:
210 ipx_print(ndo, bp, len);
211 break;
212 case ETHERTYPE_ATALK:
213 atalk_print(ndo, bp, len);
214 break;
215 case ETHERTYPE_GRE_ISO:
216 isoclns_print(ndo, bp, len, len);
217 break;
218 case ETHERTYPE_TEB:
219 ether_print(ndo, bp, len, len, NULL, NULL);
220 break;
221 default:
222 ND_PRINT((ndo, "gre-proto-0x%x", prot));
223 }
224 return;
225  
226 trunc:
227 ND_PRINT((ndo, "%s", tstr));
228 }
229  
230 static void
231 gre_print_1(netdissect_options *ndo, const u_char *bp, u_int length)
232 {
233 u_int len = length;
234 uint16_t flags, prot;
235  
236 flags = EXTRACT_16BITS(bp);
237 len -= 2;
238 bp += 2;
239  
240 if (ndo->ndo_vflag)
241 ND_PRINT((ndo, ", Flags [%s]",
242 bittok2str(gre_flag_values,"none",flags)));
243  
244 if (len < 2)
245 goto trunc;
246 prot = EXTRACT_16BITS(bp);
247 len -= 2;
248 bp += 2;
249  
250  
251 if (flags & GRE_KP) {
252 uint32_t k;
253  
254 if (len < 4)
255 goto trunc;
256 k = EXTRACT_32BITS(bp);
257 ND_PRINT((ndo, ", call %d", k & 0xffff));
258 len -= 4;
259 bp += 4;
260 }
261  
262 if (flags & GRE_SP) {
263 if (len < 4)
264 goto trunc;
265 ND_PRINT((ndo, ", seq %u", EXTRACT_32BITS(bp)));
266 bp += 4;
267 len -= 4;
268 }
269  
270 if (flags & GRE_AP) {
271 if (len < 4)
272 goto trunc;
273 ND_PRINT((ndo, ", ack %u", EXTRACT_32BITS(bp)));
274 bp += 4;
275 len -= 4;
276 }
277  
278 if ((flags & GRE_SP) == 0)
279 ND_PRINT((ndo, ", no-payload"));
280  
281 if (ndo->ndo_eflag)
282 ND_PRINT((ndo, ", proto %s (0x%04x)",
283 tok2str(ethertype_values,"unknown",prot),
284 prot));
285  
286 ND_PRINT((ndo, ", length %u",length));
287  
288 if ((flags & GRE_SP) == 0)
289 return;
290  
291 if (ndo->ndo_vflag < 1)
292 ND_PRINT((ndo, ": ")); /* put in a colon as protocol demarc */
293 else
294 ND_PRINT((ndo, "\n\t")); /* if verbose go multiline */
295  
296 switch (prot) {
297 case ETHERTYPE_PPP:
298 ppp_print(ndo, bp, len);
299 break;
300 default:
301 ND_PRINT((ndo, "gre-proto-0x%x", prot));
302 break;
303 }
304 return;
305  
306 trunc:
307 ND_PRINT((ndo, "%s", tstr));
308 }
309  
310 static void
311 gre_sre_print(netdissect_options *ndo, uint16_t af, uint8_t sreoff,
312 uint8_t srelen, const u_char *bp, u_int len)
313 {
314 switch (af) {
315 case GRESRE_IP:
316 ND_PRINT((ndo, ", (rtaf=ip"));
317 gre_sre_ip_print(ndo, sreoff, srelen, bp, len);
318 ND_PRINT((ndo, ") "));
319 break;
320 case GRESRE_ASN:
321 ND_PRINT((ndo, ", (rtaf=asn"));
322 gre_sre_asn_print(ndo, sreoff, srelen, bp, len);
323 ND_PRINT((ndo, ") "));
324 break;
325 default:
326 ND_PRINT((ndo, ", (rtaf=0x%x) ", af));
327 }
328 }
329  
330 static void
331 gre_sre_ip_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
332 const u_char *bp, u_int len)
333 {
334 struct in_addr a;
335 const u_char *up = bp;
336  
337 if (sreoff & 3) {
338 ND_PRINT((ndo, ", badoffset=%u", sreoff));
339 return;
340 }
341 if (srelen & 3) {
342 ND_PRINT((ndo, ", badlength=%u", srelen));
343 return;
344 }
345 if (sreoff >= srelen) {
346 ND_PRINT((ndo, ", badoff/len=%u/%u", sreoff, srelen));
347 return;
348 }
349  
350 for (;;) {
351 if (len < 4 || srelen == 0)
352 return;
353  
354 memcpy(&a, bp, sizeof(a));
355 ND_PRINT((ndo, " %s%s",
356 ((bp - up) == sreoff) ? "*" : "",
357 inet_ntoa(a)));
358  
359 bp += 4;
360 len -= 4;
361 srelen -= 4;
362 }
363 }
364  
365 static void
366 gre_sre_asn_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
367 const u_char *bp, u_int len)
368 {
369 const u_char *up = bp;
370  
371 if (sreoff & 1) {
372 ND_PRINT((ndo, ", badoffset=%u", sreoff));
373 return;
374 }
375 if (srelen & 1) {
376 ND_PRINT((ndo, ", badlength=%u", srelen));
377 return;
378 }
379 if (sreoff >= srelen) {
380 ND_PRINT((ndo, ", badoff/len=%u/%u", sreoff, srelen));
381 return;
382 }
383  
384 for (;;) {
385 if (len < 2 || srelen == 0)
386 return;
387  
388 ND_PRINT((ndo, " %s%x",
389 ((bp - up) == sreoff) ? "*" : "",
390 EXTRACT_16BITS(bp)));
391  
392 bp += 2;
393 len -= 2;
394 srelen -= 2;
395 }
396 }