/* $OpenBSD: print-gre.c,v 1.6 2002/10/30 03:04:04 fgsch Exp $ */

/*

* Copyright (c) 2002 Jason L. Wright (jason@thought.net)

* All rights reserved.

*

* Redistribution and use in source and binary forms, with or without

* modification, are permitted provided that the following conditions

* are met:

* 1. Redistributions of source code must retain the above copyright

* notice, this list of conditions and the following disclaimer.

* 2. Redistributions in binary form must reproduce the above copyright

* notice, this list of conditions and the following disclaimer in the

* documentation and/or other materials provided with the distribution.

* 3. All advertising materials mentioning features or use of this software

* must display the following acknowledgement:

* This product includes software developed by Jason L. Wright

* 4. The name of the author may not be used to endorse or promote products

* derived from this software without specific prior written permission.

*

* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR

* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,

* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR

* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,

* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN

* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

* POSSIBILITY OF SUCH DAMAGE.

*/

/*

* tcpdump filter for GRE - Generic Routing Encapsulation

* RFC1701 (GRE), RFC1702 (GRE IPv4), and RFC2637 (Enhanced GRE)

*/

#define NETDISSECT_REWORKED

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include <tcpdump-stdinc.h>

#include <string.h>

#include "interface.h"

#include "extract.h"

#include "ethertype.h"

static const char tstr[] = "[|gre]";

#define GRE_CP 0x8000 /* checksum present */

#define GRE_RP 0x4000 /* routing present */

#define GRE_KP 0x2000 /* key present */

#define GRE_SP 0x1000 /* sequence# present */

#define GRE_sP 0x0800 /* source routing */

#define GRE_RECRS 0x0700 /* recursion count */

#define GRE_AP 0x0080 /* acknowledgment# present */

static const struct tok gre_flag_values[] = {

{ GRE_CP, "checksum present"},

{ GRE_RP, "routing present"},

{ GRE_KP, "key present"},

{ GRE_SP, "sequence# present"},

{ GRE_sP, "source routing present"},

{ GRE_RECRS, "recursion count"},

{ GRE_AP, "ack present"},

{ 0, NULL }

};

#define GRE_VERS_MASK 0x0007 /* protocol version */

/* source route entry types */

#define GRESRE_IP 0x0800 /* IP */

#define GRESRE_ASN 0xfffe /* ASN */

static void gre_print_0(netdissect_options *, const u_char *, u_int);

static void gre_print_1(netdissect_options *, const u_char *, u_int);

static void gre_sre_print(netdissect_options *, uint16_t, uint8_t, uint8_t, const u_char *, u_int);

static void gre_sre_ip_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);

static void gre_sre_asn_print(netdissect_options *, uint8_t, uint8_t, const u_char *, u_int);

void

gre_print(netdissect_options *ndo, const u_char *bp, u_int length)

{

u_int len = length, vers;

if (len < 2) {

ND_PRINT((ndo, "%s", tstr));

return;

}

vers = EXTRACT_16BITS(bp) & GRE_VERS_MASK;

ND_PRINT((ndo, "GREv%u",vers));

switch(vers) {

case 0:

gre_print_0(ndo, bp, len);

break;

case 1:

gre_print_1(ndo, bp, len);

break;

default:

ND_PRINT((ndo, " ERROR: unknown-version"));

break;

}

}

static void

gre_print_0(netdissect_options *ndo, const u_char *bp, u_int length)

{

u_int len = length;

uint16_t flags, prot;

flags = EXTRACT_16BITS(bp);

if (ndo->ndo_vflag)

ND_PRINT((ndo, ", Flags [%s]",

bittok2str(gre_flag_values,"none",flags)));

len -= 2;

bp += 2;

if (len < 2)

goto trunc;

prot = EXTRACT_16BITS(bp);

len -= 2;

bp += 2;

if ((flags & GRE_CP) | (flags & GRE_RP)) {

if (len < 2)

goto trunc;

if (ndo->ndo_vflag)

ND_PRINT((ndo, ", sum 0x%x", EXTRACT_16BITS(bp)));

bp += 2;

len -= 2;

if (len < 2)

goto trunc;

ND_PRINT((ndo, ", off 0x%x", EXTRACT_16BITS(bp)));

bp += 2;

len -= 2;

}

if (flags & GRE_KP) {

if (len < 4)

goto trunc;

ND_PRINT((ndo, ", key=0x%x", EXTRACT_32BITS(bp)));

bp += 4;

len -= 4;

}

if (flags & GRE_SP) {

if (len < 4)

goto trunc;

ND_PRINT((ndo, ", seq %u", EXTRACT_32BITS(bp)));

bp += 4;

len -= 4;

}

if (flags & GRE_RP) {

for (;;) {

uint16_t af;

uint8_t sreoff;

uint8_t srelen;

if (len < 4)

goto trunc;

af = EXTRACT_16BITS(bp);

sreoff = *(bp + 2);

srelen = *(bp + 3);

bp += 4;

len -= 4;

if (af == 0 && srelen == 0)

break;

gre_sre_print(ndo, af, sreoff, srelen, bp, len);

if (len < srelen)

goto trunc;

bp += srelen;

len -= srelen;

}

}

if (ndo->ndo_eflag)

ND_PRINT((ndo, ", proto %s (0x%04x)",

tok2str(ethertype_values,"unknown",prot),

prot));

ND_PRINT((ndo, ", length %u",length));

if (ndo->ndo_vflag < 1)

ND_PRINT((ndo, ": ")); /* put in a colon as protocol demarc */

else

ND_PRINT((ndo, "\n\t")); /* if verbose go multiline */

switch (prot) {

case ETHERTYPE_IP:

ip_print(ndo, bp, len);

break;

#ifdef INET6

case ETHERTYPE_IPV6:

ip6_print(ndo, bp, len);

break;

#endif

case ETHERTYPE_MPLS:

mpls_print(ndo, bp, len);

break;

case ETHERTYPE_IPX:

ipx_print(ndo, bp, len);

break;

case ETHERTYPE_ATALK:

atalk_print(ndo, bp, len);

break;

case ETHERTYPE_GRE_ISO:

isoclns_print(ndo, bp, len, len);

break;

case ETHERTYPE_TEB:

ether_print(ndo, bp, len, len, NULL, NULL);

break;

default:

ND_PRINT((ndo, "gre-proto-0x%x", prot));

}

return;

trunc:

ND_PRINT((ndo, "%s", tstr));

}

static void

gre_print_1(netdissect_options *ndo, const u_char *bp, u_int length)

{

u_int len = length;

uint16_t flags, prot;

flags = EXTRACT_16BITS(bp);

len -= 2;

bp += 2;

if (ndo->ndo_vflag)

ND_PRINT((ndo, ", Flags [%s]",

bittok2str(gre_flag_values,"none",flags)));

if (len < 2)

goto trunc;

prot = EXTRACT_16BITS(bp);

len -= 2;

bp += 2;

if (flags & GRE_KP) {

uint32_t k;

if (len < 4)

goto trunc;

k = EXTRACT_32BITS(bp);

ND_PRINT((ndo, ", call %d", k & 0xffff));

len -= 4;

bp += 4;

}

if (flags & GRE_SP) {

if (len < 4)

goto trunc;

ND_PRINT((ndo, ", seq %u", EXTRACT_32BITS(bp)));

bp += 4;

len -= 4;

}

if (flags & GRE_AP) {

if (len < 4)

goto trunc;

ND_PRINT((ndo, ", ack %u", EXTRACT_32BITS(bp)));

bp += 4;

len -= 4;

}

if ((flags & GRE_SP) == 0)

ND_PRINT((ndo, ", no-payload"));

if (ndo->ndo_eflag)

ND_PRINT((ndo, ", proto %s (0x%04x)",

tok2str(ethertype_values,"unknown",prot),

prot));

ND_PRINT((ndo, ", length %u",length));

if ((flags & GRE_SP) == 0)

return;

if (ndo->ndo_vflag < 1)

ND_PRINT((ndo, ": ")); /* put in a colon as protocol demarc */

else

ND_PRINT((ndo, "\n\t")); /* if verbose go multiline */

switch (prot) {

case ETHERTYPE_PPP:

ppp_print(ndo, bp, len);

break;

default:

ND_PRINT((ndo, "gre-proto-0x%x", prot));

break;

}

return;

trunc:

ND_PRINT((ndo, "%s", tstr));

}

static void

gre_sre_print(netdissect_options *ndo, uint16_t af, uint8_t sreoff,

uint8_t srelen, const u_char *bp, u_int len)

{

switch (af) {

case GRESRE_IP:

ND_PRINT((ndo, ", (rtaf=ip"));

gre_sre_ip_print(ndo, sreoff, srelen, bp, len);

ND_PRINT((ndo, ") "));

break;

case GRESRE_ASN:

ND_PRINT((ndo, ", (rtaf=asn"));

gre_sre_asn_print(ndo, sreoff, srelen, bp, len);

ND_PRINT((ndo, ") "));

break;

default:

ND_PRINT((ndo, ", (rtaf=0x%x) ", af));

}

}

static void

gre_sre_ip_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,

const u_char *bp, u_int len)

{

struct in_addr a;

const u_char *up = bp;

if (sreoff & 3) {

ND_PRINT((ndo, ", badoffset=%u", sreoff));

return;

}

if (srelen & 3) {

ND_PRINT((ndo, ", badlength=%u", srelen));

return;

}

if (sreoff >= srelen) {

ND_PRINT((ndo, ", badoff/len=%u/%u", sreoff, srelen));

return;

}

for (;;) {

if (len < 4 || srelen == 0)

return;

memcpy(&a, bp, sizeof(a));

ND_PRINT((ndo, " %s%s",

((bp - up) == sreoff) ? "*" : "",

inet_ntoa(a)));

bp += 4;

len -= 4;

srelen -= 4;

}

}

static void

gre_sre_asn_print(netdissect_options *ndo, uint8_t sreoff, uint8_t srelen,

const u_char *bp, u_int len)

{

const u_char *up = bp;

if (sreoff & 1) {

ND_PRINT((ndo, ", badoffset=%u", sreoff));

return;

}

if (srelen & 1) {

ND_PRINT((ndo, ", badlength=%u", srelen));

return;

}

if (sreoff >= srelen) {

ND_PRINT((ndo, ", badoff/len=%u/%u", sreoff, srelen));

return;

}

for (;;) {

if (len < 2 || srelen == 0)

return;

ND_PRINT((ndo, " %s%x",

((bp - up) == sreoff) ? "*" : "",

EXTRACT_16BITS(bp)));

bp += 2;

len -= 2;

srelen -= 2;

}

}