/* packet-mndp.c

 * Routines for the disassembly of the Mikrotik Neighbor Discovery Protocol

 *

 * Copyright 2011 Joerg Mayer (see AUTHORS file)

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998 Gerald Combs

 *

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

 */

/*

  http://wiki.mikrotik.com/wiki/Manual:IP/Neighbor_discovery

  TODO:

  - Find out about first 4 bytes (are the first 2 simply part of the sequence number?)

  - Find out about additional TLVs

  - Find out about unpack values

 */

#include "config.h"

#include <epan/packet.h>

void proto_register_mndp(void);

void proto_reg_handoff_mndp(void);

static dissector_handle_t mndp_handle;

/* protocol handles */

static int proto_mndp;

/* ett handles */

static int ett_mndp;

static int ett_mndp_tlv_header;

/* hf elements */

/* tlv generic */

static int hf_mndp_tlv_type;

static int hf_mndp_tlv_length;

static int hf_mndp_tlv_data;

/* tunnel header */

static int hf_mndp_header_unknown;

static int hf_mndp_header_seqno;

/* tlvs */

static int hf_mndp_mac;

static int hf_mndp_softwareid;

static int hf_mndp_version;

static int hf_mndp_identity;

static int hf_mndp_uptime;

static int hf_mndp_platform;

static int hf_mndp_board;

static int hf_mndp_unpack;

static int hf_mndp_ipv6address;

static int hf_mndp_interfacename;

static int hf_mndp_ipv4address;

#define PROTO_SHORT_NAME "MNDP"

#define PROTO_LONG_NAME "Mikrotik Neighbor Discovery Protocol"

#define PORT_MNDP 5678 /* Not IANA registered */

/* ============= copy/paste/modify from value_string.[hc] ============== */

typedef struct _ext_value_string {

  uint32_t value;

  const char    *strptr;

  int* hf_element;

  int (*specialfunction)(tvbuff_t *, packet_info *, proto_tree *, uint32_t,

             uint32_t, const struct _ext_value_string *);

  const struct _ext_value_string *evs;

} ext_value_string;

static const char*

match_strextval_idx(uint32_t val, const ext_value_string *vs, int *idx) {

  int i = 0;

  if(vs) {

    while (vs[i].strptr) {

      if (vs[i].value == val) {

        if (idx)

          *idx = i;

        return vs[i].strptr;

      }

      i++;

    }

  }

  if (idx)

    *idx = -1;

  return NULL;

}

static const char*

extval_to_str_idx(wmem_allocator_t *pool, uint32_t val, const ext_value_string *vs, int *idx, const char *fmt) {

  const char *ret;

  if (!fmt)

    fmt="Unknown";

  ret = match_strextval_idx(val, vs, idx);

  if (ret != NULL)

    return ret;

  return wmem_strdup_printf(pool, fmt, val);

}

/* ============= end copy/paste/modify  ============== */

/* Forward decls needed by mndp_tunnel_tlv_vals et al */

static int dissect_tlv(tvbuff_t *tvb, packet_info *pinfo, proto_tree *mndp_tree,

  uint32_t offset, uint32_t length, const ext_value_string *value_array);

static const ext_value_string mndp_body_tlv_vals[] = {

  {  1, "MAC-Address",  &hf_mndp_mac,   NULL, NULL },

  {  5, "Identity", &hf_mndp_identity,  NULL, NULL },

  {  7, "Version",  &hf_mndp_version, NULL, NULL },

  {  8, "Platform", &hf_mndp_platform,  NULL, NULL },

  { 10, "Uptime",   &hf_mndp_uptime,  NULL, (ext_value_string *)true },

  { 11, "Software-ID",  &hf_mndp_softwareid,  NULL, NULL },

  { 12, "Board",    &hf_mndp_board,   NULL, NULL },

  { 14, "Unpack",   &hf_mndp_unpack,  NULL, NULL },

  { 15, "IPv6-Address", &hf_mndp_ipv6address, NULL, NULL },

  { 16, "Interface name", &hf_mndp_interfacename, NULL, NULL },

  { 17, "IPv4-Address", &hf_mndp_ipv4address, NULL, NULL },

  { 0, NULL, NULL, NULL, NULL }

};

static const value_string mndp_unpack_vals[] = {

  /* none|simple|uncompressed-headers|uncompressed-all */

  { 1,  "None" },

  { 0,  NULL }

};

static int

dissect_tlv(tvbuff_t *tvb, packet_info *pinfo, proto_tree *mndp_tree,

  uint32_t offset, uint32_t length _U_, const ext_value_string *value_array)

{

  uint32_t    tlv_type;

  uint32_t    tlv_length;

  proto_item *tlv_tree;

  proto_item *type_item;

  int         type_index;

  uint32_t    tlv_end;

  unsigned    encoding_info;

  tlv_type = tvb_get_ntohs(tvb, offset);

  tlv_length = tvb_get_ntohs(tvb, offset + 2);

  tlv_tree = proto_tree_add_subtree_format(mndp_tree, tvb,

    offset, tlv_length+4, ett_mndp_tlv_header, NULL,

    "T %d, L %d: %s",

    tlv_type,

    tlv_length,

    extval_to_str_idx(pinfo->pool, tlv_type, value_array, NULL, "Unknown"));

  type_item = proto_tree_add_item(tlv_tree, hf_mndp_tlv_type,

    tvb, offset, 2, ENC_BIG_ENDIAN);

  proto_item_append_text(type_item, " = %s",

    extval_to_str_idx(pinfo->pool, tlv_type, value_array,

      &type_index, "Unknown"));

  offset += 2;

  proto_tree_add_item(tlv_tree, hf_mndp_tlv_length,

    tvb, offset, 2, ENC_BIG_ENDIAN);

  offset += 2;

  if (tlv_length == 0)

    return offset;

  tlv_end = offset + tlv_length;

  /* Make hf_ handling independent of specialfunction */

  /* FIXME: Properly handle encoding info */

  if ( type_index != -1

     && !value_array[type_index].specialfunction

     && value_array[type_index].evs != NULL

  ) {

    encoding_info = value_array[type_index].evs ? true : false;

  } else {

    encoding_info = false;

  }

  if ( type_index != -1 && value_array[type_index].hf_element) {

    proto_tree_add_item(tlv_tree,

      *(value_array[type_index].hf_element),

      tvb, offset, tlv_length, encoding_info);

  } else {

    proto_tree_add_item(tlv_tree, hf_mndp_tlv_data,

      tvb, offset, tlv_length, ENC_NA);

  }

  if ( type_index != -1 && value_array[type_index].specialfunction ) {

    uint32_t newoffset;

    while (offset < tlv_end) {

      newoffset = value_array[type_index].specialfunction (

        tvb, pinfo, tlv_tree, offset, tlv_length,

        value_array[type_index].evs);

      DISSECTOR_ASSERT(newoffset > offset);

      offset = newoffset;

    }

  }

  return tlv_end;

}

static int

dissect_mndp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)

{

  proto_item *ti;

  proto_tree *mndp_tree;

  uint32_t    offset = 0;

  uint32_t    packet_length;

  col_set_str(pinfo->cinfo, COL_PROTOCOL, PROTO_SHORT_NAME);

  packet_length = tvb_reported_length(tvb);

  /* Header dissection */

  ti = proto_tree_add_item(tree, proto_mndp, tvb, offset, -1,

         ENC_NA);

  mndp_tree = proto_item_add_subtree(ti, ett_mndp);

  proto_tree_add_item(mndp_tree, hf_mndp_header_unknown, tvb, offset, 2,

          ENC_NA);

  offset += 2;

  proto_tree_add_item(mndp_tree, hf_mndp_header_seqno, tvb, offset, 2,

          ENC_BIG_ENDIAN);

  offset += 2;

  while (offset < packet_length) {

    offset = dissect_tlv(tvb, pinfo, mndp_tree,

             offset, 0, mndp_body_tlv_vals);

  }

  return offset;

}

static bool

test_mndp(tvbuff_t *tvb)

{

  /* Observed captures of MNDP always seem to have port 5678 as both

   * the source and destination port, and have a broadcast destination IP

   * and destination MAC address (if we have those layers.)

   * The TLVs are also transmitted in increasing type order.

   * TLV type 1 (MAC-Address) appears to be mandatory (and thus first),

   * and always has length 6.

   * We could also step through all the TLVs to see if the types and

   * lengths are reasonable.

   * Any of these could be used to strengthen the heuristic further.

   */

  int offset = 0;

  int type, length;

  /* Minimum of 8 bytes, 4 Bytes header + 1 TLV-header */

  if ( tvb_captured_length(tvb) < 8) {

    return false;

  }

  offset += 4;

  type = tvb_get_uint16(tvb, offset, ENC_BIG_ENDIAN);

  if (type != 1) {

    return false;

  }

  offset += 2;

  length = tvb_get_uint16(tvb, offset, ENC_BIG_ENDIAN);

  if (length != 6) {

    return false;

  }

  offset += 2;

  /* Length does *not* include the type and length fields. */

  if (tvb_reported_length_remaining(tvb, offset) < length) {

    return false;

  }

  offset += length;

  /* If there's more data left, it should be another TLV. */

  if (tvb_reported_length_remaining(tvb, offset) > 0 &&

      tvb_reported_length_remaining(tvb, offset) < 4) {

    return false;

  }

  return true;

}

static bool

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

{

  if ( !test_mndp(tvb) ) {

    return false;

  }

  dissect_mndp(tvb, pinfo, tree);

  return true;

}

static int

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

{

  if ( !test_mndp(tvb) ) {

    return 0;

  }

  return dissect_mndp(tvb, pinfo, tree);

}

void

proto_register_mndp(void)

{

  static hf_register_info hf[] = {

  /* TLV fields */

    { &hf_mndp_tlv_type,

    { "TlvType",  "mndp.tlv.type", FT_UINT16, BASE_DEC, NULL,

      0x0, NULL, HFILL }},

    { &hf_mndp_tlv_length,

    { "TlvLength",  "mndp.tlv.length", FT_UINT16, BASE_DEC, NULL,

      0x0, NULL, HFILL }},

    { &hf_mndp_tlv_data,

    { "TlvData",   "mndp.tlv.data", FT_BYTES, BASE_NONE, NULL,

      0x0, NULL, HFILL }},

  /* MNDP tunnel header */

    { &hf_mndp_header_unknown,

    { "Header Unknown", "mndp.header.unknown", FT_BYTES, BASE_NONE, NULL,

      0x0, NULL, HFILL }},

    { &hf_mndp_header_seqno,

    { "SeqNo",  "mndp.header.seqno", FT_UINT16, BASE_DEC, NULL,

      0x0, NULL, HFILL }},

  /* MNDP tunnel data */

    { &hf_mndp_mac,

    { "MAC-Address",  "mndp.mac", FT_ETHER, BASE_NONE, NULL,

      0x0, NULL, HFILL }},

    { &hf_mndp_softwareid,

    { "Software-ID", "mndp.softwareid", FT_STRING, BASE_NONE, NULL,

        0x0, NULL, HFILL }},

    { &hf_mndp_version,

    { "Version", "mndp.version", FT_STRING, BASE_NONE, NULL,

        0x0, NULL, HFILL }},

    { &hf_mndp_identity,

    { "Identity", "mndp.identity", FT_STRING, BASE_NONE, NULL,

        0x0, NULL, HFILL }},

    { &hf_mndp_uptime,

    { "Uptime", "mndp.uptime", FT_RELATIVE_TIME, BASE_NONE, NULL,

        0x0, NULL, HFILL }},

    { &hf_mndp_platform,

    { "Platform", "mndp.platform", FT_STRING, BASE_NONE, NULL,

        0x0, NULL, HFILL }},

    { &hf_mndp_board,

    { "Board", "mndp.board", FT_STRING, BASE_NONE, NULL,

        0x0, NULL, HFILL }},

    { &hf_mndp_unpack,

    { "Unpack", "mndp.unpack", FT_UINT8, BASE_DEC, VALS(mndp_unpack_vals),

        0x0, NULL, HFILL }},

    { &hf_mndp_ipv6address,

    { "IPv6-Address", "mndp.ipv6address", FT_IPv6, BASE_NONE, NULL,

        0x0, NULL, HFILL }},

    { &hf_mndp_interfacename,

    { "Interface name", "mndp.interfacename", FT_STRING, BASE_NONE, NULL,

        0x0, NULL, HFILL }},

    { &hf_mndp_ipv4address,

    { "IPv4-Address", "mndp.ipv4address", FT_IPv4, BASE_NONE, NULL,

        0x0, NULL, HFILL }},

  };

  static int *ett[] = {

    &ett_mndp,

    &ett_mndp_tlv_header,

  };

  proto_mndp = proto_register_protocol(PROTO_LONG_NAME, PROTO_SHORT_NAME, "mndp");

  proto_register_field_array(proto_mndp, hf, array_length(hf));

  proto_register_subtree_array(ett, array_length(ett));

  mndp_handle = register_dissector("mndp", dissect_mndp_static, proto_mndp);

}

void

proto_reg_handoff_mndp(void)

{

  dissector_add_uint_with_preference("udp.port", PORT_MNDP, mndp_handle);

  heur_dissector_add("udp", dissect_mndp_heur, "MNDP over UDP", "mndp_udp", proto_mndp, HEURISTIC_DISABLE);

}

/*

 * 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:

 */