/*
* 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.
*/

#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: print-loopback.c,v 1.6 2024/09/02 16:15:32 christos Exp $");
#endif

/* \summary: Loopback Protocol printer */

/*
* originally defined as the Ethernet Configuration Testing Protocol.
* specification:
* https://web.archive.org/web/20060919181108/http://www.mit.edu/people/jhawk/ctp.pdf
*/

#include <config.h>

#include "netdissect-stdinc.h"

#define ND_LONGJMP_FROM_TCHECK
#include "netdissect.h"
#include "extract.h"
#include "addrtoname.h"


#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, u_int len)
{
       uint16_t function;

       if (len < 2)
               goto invalid;
       /* function */
       function = GET_LE_U_2(cp);
       cp += 2;
       len -= 2;
       ND_PRINT(", %s", tok2str(fcode_str, " invalid (%u)", function));

       switch (function) {
               case LOOPBACK_REPLY:
                       if (len < 2)
                               goto invalid;
                       /* receipt number */
                       ND_PRINT(", receipt number %u", GET_LE_U_2(cp));
                       cp += 2;
                       len -= 2;
                       /* data */
                       ND_PRINT(", data (%u octets)", len);
                       ND_TCHECK_LEN(cp, len);
                       break;
               case LOOPBACK_FWDDATA:
                       if (len < MAC_ADDR_LEN)
                               goto invalid;
                       /* forwarding address */
                       ND_PRINT(", forwarding address %s", GET_ETHERADDR_STRING(cp));
                       cp += MAC_ADDR_LEN;
                       len -= MAC_ADDR_LEN;
                       /* data */
                       ND_PRINT(", data (%u octets)", len);
                       ND_TCHECK_LEN(cp, len);
                       break;
               default:
                       ND_TCHECK_LEN(cp, len);
                       break;
       }
       return;

invalid:
       nd_print_invalid(ndo);
       ND_TCHECK_LEN(cp, len);
}

void
loopback_print(netdissect_options *ndo,
              const u_char *cp, u_int len)
{
       uint16_t skipCount;

       ndo->ndo_protocol = "loopback";
       ND_PRINT("Loopback");
       if (len < 2)
               goto invalid;
       /* skipCount */
       skipCount = GET_LE_U_2(cp);
       cp += 2;
       len -= 2;
       ND_PRINT(", skipCount %u", skipCount);
       if (skipCount % 8)
               ND_PRINT(" (bogus)");
       if (skipCount > len)
               goto invalid;
       /* the octets to skip */
       ND_TCHECK_LEN(cp, skipCount);
       cp += skipCount;
       len -= skipCount;
       /* the first message to decode */
       loopback_message_print(ndo, cp, len);
       return;

invalid:
       nd_print_invalid(ndo);
       ND_TCHECK_LEN(cp, len);
}