/*

* This module implements decoding of the the Loopback Protocol, originally

* defined as the Configuration Testing Protocol. It is based on the following

* specification:

* http://www.mit.edu/people/jhawk/ctp.pdf

*

* Copyright (c) 2014 The TCPDUMP project

* 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.

*

* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

* "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

* COPYRIGHT HOLDER OR CONTRIBUTORS 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.

*/

#define NETDISSECT_REWORKED

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include <tcpdump-stdinc.h>

#include "interface.h"

#include "extract.h"

#include "ether.h"

#include "addrtoname.h"

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

static const char cstr[] = " (corrupt)";

#define LOOPBACK_REPLY 1

#define LOOPBACK_FWDDATA 2

static const struct tok fcode_str[] = {

{ LOOPBACK_REPLY, "Reply" },

{ LOOPBACK_FWDDATA, "Forward Data" },

{ 0, NULL }

};

static void

loopback_message_print(netdissect_options *ndo, const u_char *cp, const u_int len)

{

const u_char *ep = cp + len;

uint16_t function;

if (len < 2)

goto corrupt;

/* function */

ND_TCHECK2(*cp, 2);

function = EXTRACT_LE_16BITS(cp);

cp += 2;

ND_PRINT((ndo, ", %s", tok2str(fcode_str, " invalid (%u)", function)));

switch (function) {

case LOOPBACK_REPLY:

if (len < 4)

goto corrupt;

/* receipt number */

ND_TCHECK2(*cp, 2);

ND_PRINT((ndo, ", receipt number %u", EXTRACT_LE_16BITS(cp)));

cp += 2;

/* data */

ND_PRINT((ndo, ", data (%u octets)", len - 4));

ND_TCHECK2(*cp, len - 4);

break;

case LOOPBACK_FWDDATA:

if (len < 8)

goto corrupt;

/* forwarding address */

ND_TCHECK2(*cp, ETHER_ADDR_LEN);

ND_PRINT((ndo, ", forwarding address %s", etheraddr_string(cp)));

cp += ETHER_ADDR_LEN;

/* data */

ND_PRINT((ndo, ", data (%u octets)", len - 8));

ND_TCHECK2(*cp, len - 8);

break;

default:

ND_TCHECK2(*cp, len - 2);

break;

}

return;

corrupt:

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

ND_TCHECK2(*cp, ep - cp);

return;

trunc:

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

}

void

loopback_print(netdissect_options *ndo, const u_char *cp, const u_int len)

{

const u_char *ep = cp + len;

uint16_t skipCount;

ND_PRINT((ndo, "Loopback"));

if (len < 2)

goto corrupt;

/* skipCount */

ND_TCHECK2(*cp, 2);

skipCount = EXTRACT_LE_16BITS(cp);

cp += 2;

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

if (skipCount % 8)

ND_PRINT((ndo, " (bogus)"));

if (skipCount > len - 2)

goto corrupt;

loopback_message_print(ndo, cp + skipCount, len - 2 - skipCount);

return;

corrupt:

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

ND_TCHECK2(*cp, ep - cp);

return;

trunc:

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

}