nexmon – Rev 1
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/* $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;
case ETHERTYPE_IPV6:
ip6_print(ndo, bp, len);
break;
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;
}
}