/* packet-rlm.c

 * Routines for RLM dissection

 * Copyright 2004, Duncan Sargeant <dunc-ethereal@rcpt.to>

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998 Gerald Combs

 *

 * SPDX-License-Identifier: GPL-2.0-or-later

 */

/*

 * RLM is a proprietary Cisco protocol used for centralling managing

 * many redundant NASes.  I don't know much about the format, but you

 * can read about the feature here:

 *

 * http://www.cisco.com/en/US/docs/ios/12_0t/12_0t3/feature/guide/rlm_123.html

 *

 * RLM runs on a UDP port (default 3000) between the MGC and the NAS.

 * On port N+1 (default 3001), a Q.931/LAPD/UDP connection is maintained.

 * Both sides use the same local port number for the connection, so source

 * and dest port are always the same.

 *

 * In large networks, the links are typically split onto higher ports,

 * so anything up to 3015 (or higher) could either be RLM or Q.931 traffic,

 * although always the RLM has the one lower port number for that RLM group.

 *

 * Multiple RLM groups are possible on a single NAS.

 *

 * I haven't been able to find the protocol documented, so I've

 * guessed some of the fields based on the output of debug commands on

 * cisco NASes.

 *

 */

#include "config.h"

#include <epan/packet.h>

void proto_register_rlm(void);

void proto_reg_handoff_rlm(void);

/* Initialize the protocol and registered fields */

static int proto_rlm;

static int hf_rlm_version;

static int hf_rlm_type;

static int hf_rlm_unknown;

static int hf_rlm_tid;

static int hf_rlm_unknown2;

/* Initialize the subtree pointers */

static int ett_rlm;

/* RLM definitions - missing some! */

#define RLM_START_REQUEST 1

#define RLM_START_ACK   2

/* #define ???  3 */

/* #define ???  4 */

#define RLM_ECHO_REQUEST  5

#define RLM_ECHO_REPLY    6

/* #define ???  ?? */

/* Code to actually dissect the packets */

static bool

dissect_rlm(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)

{

  proto_item *ti;

  proto_tree *rlm_tree;

  uint8_t rlm_type, version;

  const char *type_str = NULL;

  if (pinfo->srcport < 3000 || pinfo->srcport > 3015

      || pinfo->destport < 3000 || pinfo->destport > 3015

      || pinfo->destport != pinfo->srcport)

    return false;

  if (tvb_captured_length(tvb) < 2)

    return false;

  version  = tvb_get_uint8(tvb, 0);

  rlm_type = tvb_get_uint8(tvb, 1);

  /* we only know about version 2, and I've only seen 8 byte packets */

  if (tvb_captured_length(tvb) != 8 || version != 2) {

    return false;

  }

  col_set_str(pinfo->cinfo, COL_PROTOCOL, "RLM");

  switch (rlm_type) {

    case RLM_START_REQUEST:

      type_str = "Start request";

      break;

    case RLM_START_ACK:

      type_str = "Start acknowledgement";

      break;

    case RLM_ECHO_REQUEST:

      type_str = "Echo request";

      break;

    case RLM_ECHO_REPLY:

      type_str = "Echo reply";

      break;

    default:

      type_str = "Unknown type";

      break;

  }

  col_set_str(pinfo->cinfo, COL_INFO, type_str);

  if (tree) {

    /* proto_tree_add_protocol_format(tree, proto_rlm, tvb, 0,

      16, "Cisco Session Management"); */

    ti = proto_tree_add_item(tree, proto_rlm, tvb, 0, 8, ENC_NA);

    rlm_tree = proto_item_add_subtree(ti, ett_rlm);

    proto_tree_add_item(rlm_tree, hf_rlm_version, tvb, 0, 1, ENC_BIG_ENDIAN);

    proto_tree_add_uint_format_value(rlm_tree, hf_rlm_type, tvb, 1, 1, rlm_type, "%u (%s)", rlm_type, type_str);

    proto_tree_add_item(rlm_tree, hf_rlm_unknown, tvb, 2, 2, ENC_BIG_ENDIAN);

    proto_tree_add_item(rlm_tree, hf_rlm_tid, tvb, 4, 2, ENC_BIG_ENDIAN);

    proto_tree_add_item(rlm_tree, hf_rlm_unknown2, tvb, 6, 2, ENC_BIG_ENDIAN);

  }

  return true;

}

/* Register the protocol with Wireshark */

/* this format is require because a script is used to build the C function

   that calls all the protocol registration.

*/

void

proto_reg_handoff_rlm(void)

{

  heur_dissector_add("udp", dissect_rlm, "Redundant Link Management over UDP", "rlm_udp", proto_rlm, HEURISTIC_ENABLE);

}

void

proto_register_rlm(void)

{

/* Setup list of header fields  See Section 1.6.1 for details*/

  static hf_register_info hf[] = {

    { &hf_rlm_version,

      { "Version",           "rlm.version",

      FT_UINT8, BASE_DEC, NULL, 0x0,

      NULL, HFILL }

    },

    { &hf_rlm_type,

      { "Type",           "rlm.type",

      FT_UINT8, BASE_DEC, NULL, 0x0,

      NULL, HFILL }

    },

    { &hf_rlm_unknown,

      { "Unknown",           "rlm.unknown",

      FT_UINT16, BASE_HEX, NULL, 0x0,

      NULL, HFILL }

    },

    { &hf_rlm_tid,

      { "Transaction ID",           "rlm.tid",

      FT_UINT16, BASE_DEC, NULL, 0x0,

      NULL, HFILL }

    },

    { &hf_rlm_unknown2,

      { "Unknown",           "rlm.unknown2",

      FT_UINT16, BASE_HEX, NULL, 0x0,

      NULL, HFILL }

    },

  };

/* Setup protocol subtree array */

  static int *ett[] = {

    &ett_rlm,

  };

/* Register the protocol name and description */

  proto_rlm = proto_register_protocol("Redundant Link Management Protocol",

      "RLM", "rlm");

/* Required function calls to register the header fields and subtrees used */

  proto_register_field_array(proto_rlm, hf, array_length(hf));

  proto_register_subtree_array(ett, array_length(ett));

}

/*

 * Editor modelines  -  https://www.wireshark.org/tools/modelines.html

 *

 * Local variables:

 * c-basic-offset: 8

 * tab-width: 8

 * indent-tabs-mode: t

 * End:

 *

 * vi: set shiftwidth=8 tabstop=8 noexpandtab:

 * :indentSize=8:tabSize=8:noTabs=false:

 */