tcpdump  4.99.1
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print-gre.c
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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  *
16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
18  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
19  * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
20  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
21  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
22  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
24  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
25  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26  * POSSIBILITY OF SUCH DAMAGE.
27  */
28 
29 /* \summary: Generic Routing Encapsulation (GRE) printer */
30 
31 /*
32  * netdissect printer for GRE - Generic Routing Encapsulation
33  * RFC1701 (GRE), RFC1702 (GRE IPv4), and RFC2637 (Enhanced GRE)
34  */
35 
36 #ifdef HAVE_CONFIG_H
37 #include <config.h>
38 #endif
39 
40 #include "netdissect-stdinc.h"
41 
42 #include "netdissect.h"
43 #include "addrtostr.h"
44 #include "extract.h"
45 #include "ethertype.h"
46 
47 
48 #define GRE_CP 0x8000 /* checksum present */
49 #define GRE_RP 0x4000 /* routing present */
50 #define GRE_KP 0x2000 /* key present */
51 #define GRE_SP 0x1000 /* sequence# present */
52 #define GRE_sP 0x0800 /* source routing */
53 #define GRE_AP 0x0080 /* acknowledgment# present */
54 
55 static const struct tok gre_flag_values[] = {
56  { GRE_CP, "checksum present"},
57  { GRE_RP, "routing present"},
58  { GRE_KP, "key present"},
59  { GRE_SP, "sequence# present"},
60  { GRE_sP, "source routing present"},
61  { GRE_AP, "ack present"},
62  { 0, NULL }
63 };
64 
65 #define GRE_RECRS_MASK 0x0700 /* recursion count */
66 #define GRE_VERS_MASK 0x0007 /* protocol version */
67 
68 /* source route entry types */
69 #define GRESRE_IP 0x0800 /* IP */
70 #define GRESRE_ASN 0xfffe /* ASN */
71 
72 static void gre_print_0(netdissect_options *, const u_char *, u_int);
73 static void gre_print_1(netdissect_options *, const u_char *, u_int);
74 static int gre_sre_print(netdissect_options *, uint16_t, uint8_t, uint8_t, const u_char *, u_int);
75 static int gre_sre_ip_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
76 static int gre_sre_asn_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);
77 
78 void
79 gre_print(netdissect_options *ndo, const u_char *bp, u_int length)
80 {
81  u_int len = length, vers;
82 
83  ndo->ndo_protocol = "gre";
84  ND_TCHECK_2(bp);
85  if (len < 2)
86  goto trunc;
87  vers = GET_BE_U_2(bp) & GRE_VERS_MASK;
88  ND_PRINT("GREv%u",vers);
89 
90  switch(vers) {
91  case 0:
92  gre_print_0(ndo, bp, len);
93  break;
94  case 1:
95  gre_print_1(ndo, bp, len);
96  break;
97  default:
98  ND_PRINT(" ERROR: unknown-version");
99  break;
100  }
101  return;
102 
103 trunc:
104  nd_print_trunc(ndo);
105 }
106 
107 static void
108 gre_print_0(netdissect_options *ndo, const u_char *bp, u_int length)
109 {
110  u_int len = length;
111  uint16_t flags, prot;
112 
113  /* 16 bits ND_TCHECKed in gre_print() */
114  flags = GET_BE_U_2(bp);
115  if (ndo->ndo_vflag)
116  ND_PRINT(", Flags [%s]",
117  bittok2str(gre_flag_values,"none",flags));
118 
119  len -= 2;
120  bp += 2;
121 
122  ND_TCHECK_2(bp);
123  if (len < 2)
124  goto trunc;
125  prot = GET_BE_U_2(bp);
126  len -= 2;
127  bp += 2;
128 
129  if ((flags & GRE_CP) | (flags & GRE_RP)) {
130  ND_TCHECK_2(bp);
131  if (len < 2)
132  goto trunc;
133  if (ndo->ndo_vflag)
134  ND_PRINT(", sum 0x%x", GET_BE_U_2(bp));
135  bp += 2;
136  len -= 2;
137 
138  ND_TCHECK_2(bp);
139  if (len < 2)
140  goto trunc;
141  ND_PRINT(", off 0x%x", GET_BE_U_2(bp));
142  bp += 2;
143  len -= 2;
144  }
145 
146  if (flags & GRE_KP) {
147  ND_TCHECK_4(bp);
148  if (len < 4)
149  goto trunc;
150  ND_PRINT(", key=0x%x", GET_BE_U_4(bp));
151  bp += 4;
152  len -= 4;
153  }
154 
155  if (flags & GRE_SP) {
156  ND_TCHECK_4(bp);
157  if (len < 4)
158  goto trunc;
159  ND_PRINT(", seq %u", GET_BE_U_4(bp));
160  bp += 4;
161  len -= 4;
162  }
163 
164  if (flags & GRE_RP) {
165  for (;;) {
166  uint16_t af;
167  uint8_t sreoff;
168  uint8_t srelen;
169 
170  ND_TCHECK_4(bp);
171  if (len < 4)
172  goto trunc;
173  af = GET_BE_U_2(bp);
174  sreoff = GET_U_1(bp + 2);
175  srelen = GET_U_1(bp + 3);
176  bp += 4;
177  len -= 4;
178 
179  if (af == 0 && srelen == 0)
180  break;
181 
182  if (!gre_sre_print(ndo, af, sreoff, srelen, bp, len))
183  goto trunc;
184 
185  if (len < srelen)
186  goto trunc;
187  bp += srelen;
188  len -= srelen;
189  }
190  }
191 
192  if (ndo->ndo_eflag)
193  ND_PRINT(", proto %s (0x%04x)",
194  tok2str(ethertype_values,"unknown",prot), prot);
195 
196  ND_PRINT(", length %u",length);
197 
198  if (ndo->ndo_vflag < 1)
199  ND_PRINT(": "); /* put in a colon as protocol demarc */
200  else
201  ND_PRINT("\n\t"); /* if verbose go multiline */
202 
203  switch (prot) {
204  case ETHERTYPE_IP:
205  ip_print(ndo, bp, len);
206  break;
207  case ETHERTYPE_IPV6:
208  ip6_print(ndo, bp, len);
209  break;
210  case ETHERTYPE_MPLS:
211  mpls_print(ndo, bp, len);
212  break;
213  case ETHERTYPE_IPX:
214  ipx_print(ndo, bp, len);
215  break;
216  case ETHERTYPE_ATALK:
217  atalk_print(ndo, bp, len);
218  break;
219  case ETHERTYPE_GRE_ISO:
220  isoclns_print(ndo, bp, len);
221  break;
222  case ETHERTYPE_TEB:
223  ether_print(ndo, bp, len, ND_BYTES_AVAILABLE_AFTER(bp), NULL, NULL);
224  break;
225  default:
226  ND_PRINT("gre-proto-0x%x", prot);
227  }
228  return;
229 
230 trunc:
231  nd_print_trunc(ndo);
232 }
233 
234 static void
235 gre_print_1(netdissect_options *ndo, const u_char *bp, u_int length)
236 {
237  u_int len = length;
238  uint16_t flags, prot;
239 
240  /* 16 bits ND_TCHECKed in gre_print() */
241  flags = GET_BE_U_2(bp);
242  len -= 2;
243  bp += 2;
244 
245  if (ndo->ndo_vflag)
246  ND_PRINT(", Flags [%s]",
247  bittok2str(gre_flag_values,"none",flags));
248 
249  ND_TCHECK_2(bp);
250  if (len < 2)
251  goto trunc;
252  prot = GET_BE_U_2(bp);
253  len -= 2;
254  bp += 2;
255 
256 
257  if (flags & GRE_KP) {
258  uint32_t k;
259 
260  ND_TCHECK_4(bp);
261  if (len < 4)
262  goto trunc;
263  k = GET_BE_U_4(bp);
264  ND_PRINT(", call %u", k & 0xffff);
265  len -= 4;
266  bp += 4;
267  }
268 
269  if (flags & GRE_SP) {
270  ND_TCHECK_4(bp);
271  if (len < 4)
272  goto trunc;
273  ND_PRINT(", seq %u", GET_BE_U_4(bp));
274  bp += 4;
275  len -= 4;
276  }
277 
278  if (flags & GRE_AP) {
279  ND_TCHECK_4(bp);
280  if (len < 4)
281  goto trunc;
282  ND_PRINT(", ack %u", GET_BE_U_4(bp));
283  bp += 4;
284  len -= 4;
285  }
286 
287  if ((flags & GRE_SP) == 0)
288  ND_PRINT(", no-payload");
289 
290  if (ndo->ndo_eflag)
291  ND_PRINT(", proto %s (0x%04x)",
292  tok2str(ethertype_values,"unknown",prot), prot);
293 
294  ND_PRINT(", length %u",length);
295 
296  if ((flags & GRE_SP) == 0)
297  return;
298 
299  if (ndo->ndo_vflag < 1)
300  ND_PRINT(": "); /* put in a colon as protocol demarc */
301  else
302  ND_PRINT("\n\t"); /* if verbose go multiline */
303 
304  switch (prot) {
305  case ETHERTYPE_PPP:
306  ppp_print(ndo, bp, len);
307  break;
308  default:
309  ND_PRINT("gre-proto-0x%x", prot);
310  break;
311  }
312  return;
313 
314 trunc:
315  nd_print_trunc(ndo);
316 }
317 
318 static int
319 gre_sre_print(netdissect_options *ndo, uint16_t af, uint8_t sreoff,
320  uint8_t srelen, const u_char *bp, u_int len)
321 {
322  int ret;
323 
324  switch (af) {
325  case GRESRE_IP:
326  ND_PRINT(", (rtaf=ip");
327  ret = gre_sre_ip_print(ndo, sreoff, srelen, bp, len);
328  ND_PRINT(")");
329  break;
330  case GRESRE_ASN:
331  ND_PRINT(", (rtaf=asn");
332  ret = gre_sre_asn_print(ndo, sreoff, srelen, bp, len);
333  ND_PRINT(")");
334  break;
335  default:
336  ND_PRINT(", (rtaf=0x%x)", af);
337  ret = 1;
338  }
339  return (ret);
340 }
341 
342 static int
343 gre_sre_ip_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
344  const u_char *bp, u_int len)
345 {
346  const u_char *up = bp;
347  char buf[INET_ADDRSTRLEN];
348 
349  if (sreoff & 3) {
350  ND_PRINT(", badoffset=%u", sreoff);
351  return (1);
352  }
353  if (srelen & 3) {
354  ND_PRINT(", badlength=%u", srelen);
355  return (1);
356  }
357  if (sreoff >= srelen) {
358  ND_PRINT(", badoff/len=%u/%u", sreoff, srelen);
359  return (1);
360  }
361 
362  while (srelen != 0) {
363  ND_TCHECK_4(bp);
364  if (len < 4)
365  return (0);
366 
367  addrtostr(bp, buf, sizeof(buf));
368  ND_PRINT(" %s%s",
369  ((bp - up) == sreoff) ? "*" : "", buf);
370 
371  bp += 4;
372  len -= 4;
373  srelen -= 4;
374  }
375  return (1);
376 trunc:
377  return 0;
378 }
379 
380 static int
381 gre_sre_asn_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,
382  const u_char *bp, u_int len)
383 {
384  const u_char *up = bp;
385 
386  if (sreoff & 1) {
387  ND_PRINT(", badoffset=%u", sreoff);
388  return (1);
389  }
390  if (srelen & 1) {
391  ND_PRINT(", badlength=%u", srelen);
392  return (1);
393  }
394  if (sreoff >= srelen) {
395  ND_PRINT(", badoff/len=%u/%u", sreoff, srelen);
396  return (1);
397  }
398 
399  while (srelen != 0) {
400  ND_TCHECK_2(bp);
401  if (len < 2)
402  return (0);
403 
404  ND_PRINT(" %s%x",
405  ((bp - up) == sreoff) ? "*" : "", GET_BE_U_2(bp));
406 
407  bp += 2;
408  len -= 2;
409  srelen -= 2;
410  }
411  return (1);
412 trunc:
413  return 0;
414 }
const char * addrtostr(const void *src, char *dst, size_t size)
Definition: addrtostr.c:62
#define ETHERTYPE_ATALK
Definition: ethertype.h:103
#define ETHERTYPE_MPLS
Definition: ethertype.h:147
#define ETHERTYPE_GRE_ISO
Definition: ethertype.h:46
const struct tok ethertype_values[]
Definition: print-ether.c:52
#define ETHERTYPE_TEB
Definition: ethertype.h:85
#define ETHERTYPE_PPP
Definition: ethertype.h:138
#define ETHERTYPE_IPV6
Definition: ethertype.h:135
#define ETHERTYPE_IPX
Definition: ethertype.h:132
#define ETHERTYPE_IP
Definition: ethertype.h:52
#define GET_BE_U_4(p)
Definition: extract.h:877
#define GET_BE_U_2(p)
Definition: extract.h:875
#define ND_TCHECK_2(p)
Definition: extract.h:555
#define GET_U_1(p)
Definition: extract.h:872
#define ND_TCHECK_4(p)
Definition: extract.h:561
#define INET_ADDRSTRLEN
void ip6_print(netdissect_options *, const u_char *, u_int)
Definition: print-ip6.c:226
const char * tok2str(const struct tok *, const char *, u_int)
Definition: util-print.c:485
void mpls_print(netdissect_options *, const u_char *, u_int)
Definition: print-mpls.c:61
void isoclns_print(netdissect_options *, const u_char *, u_int)
char * bittok2str(const struct tok *, const char *, u_int)
Definition: util-print.c:558
void nd_print_trunc(netdissect_options *)
Definition: util-print.c:409
void atalk_print(netdissect_options *, const u_char *, u_int)
Definition: print-atalk.c:187
void ip_print(netdissect_options *, const u_char *, u_int)
Definition: print-ip.c:319
u_int ether_print(netdissect_options *, const u_char *, u_int, u_int, void(*)(netdissect_options *, const u_char *), const u_char *)
#define ND_PRINT(...)
Definition: netdissect.h:385
u_int ppp_print(netdissect_options *, const u_char *, u_int)
Definition: print-ppp.c:1509
void ipx_print(netdissect_options *, const u_char *, u_int)
Definition: print-ipx.c:73
#define ND_BYTES_AVAILABLE_AFTER(p)
Definition: netdissect.h:383
#define GRE_CP
Definition: print-gre.c:48
static int gre_sre_asn_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int)
Definition: print-gre.c:381
static const struct tok gre_flag_values[]
Definition: print-gre.c:55
#define GRE_VERS_MASK
Definition: print-gre.c:66
void gre_print(netdissect_options *ndo, const u_char *bp, u_int length)
Definition: print-gre.c:79
#define GRESRE_IP
Definition: print-gre.c:69
#define GRE_SP
Definition: print-gre.c:51
static int gre_sre_print(netdissect_options *, uint16_t, uint8_t, uint8_t, const u_char *, u_int)
Definition: print-gre.c:319
static void gre_print_0(netdissect_options *, const u_char *, u_int)
Definition: print-gre.c:108
#define GRE_sP
Definition: print-gre.c:52
#define GRESRE_ASN
Definition: print-gre.c:70
static int gre_sre_ip_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int)
Definition: print-gre.c:343
static void gre_print_1(netdissect_options *, const u_char *, u_int)
Definition: print-gre.c:235
#define GRE_KP
Definition: print-gre.c:50
#define GRE_RP
Definition: print-gre.c:49
#define GRE_AP
Definition: print-gre.c:53
const char * ndo_protocol
Definition: netdissect.h:218