/* packet-xns-llc.c

 * Routines for 3Com's encapsulation of XNS over 802.2 LLC

 * (and other protocols using DSAP 80)

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998 Gerald Combs

 *

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

 */

#include "config.h"

#include <epan/packet.h>

#include <epan/etypes.h>

/* Forward declarations */

void proto_register_3com_xns(void);

void proto_reg_handoff_3com_xns(void);

static dissector_handle_t our_xns_handle;

static int proto_3com_xns;

static int hf_3com_xns_type_ethertype;

static int hf_3com_xns_type_retix_bpdu;

static int ett_3com_xns;

static const value_string retix_bpdu_type_vals[] = {

  { 0x0004, "Retix Spanning Tree" },

  { 0, NULL }

};

static dissector_table_t ethertype_subdissector_table;

static dissector_handle_t retix_bpdu_handle;

/*

 * Apparently 3Com had some scheme for encapsulating XNS in 802.2 LLC,

 * using a DSAP and SSAP of 0x80, and putting a 2-byte field that appeared

 * to contain, at least for IPP, the Ethertype value for IPP.

 *

 * We assume that the value there is an Ethertype value, except for

 * the Retix spanning tree protocol, which also uses a DSAP and SSAP

 * of 0x80 but has, at least in one capture, 0x0004 as the type

 * field.  We handle that specially.

 *

 * XXX - I've also seen packets on 802.11 with a DSAP and SSAP of 0x80,

 * but with random stuff that appears neither to be XNS nor Retix

 * spanning tree.

 */

static int

dissect_3com_xns(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)

{

  proto_tree *subtree;

  proto_tree *ti;

  uint16_t type;

  tvbuff_t *next_tvb;

  col_set_str(pinfo->cinfo, COL_PROTOCOL, "3Com XNS");

  col_clear(pinfo->cinfo, COL_INFO);

  ti = proto_tree_add_item(tree, proto_3com_xns, tvb, 0, 4, ENC_NA);

  subtree = proto_item_add_subtree(ti, ett_3com_xns);

  type = tvb_get_ntohs(tvb, 0);

  next_tvb = tvb_new_subset_remaining(tvb, 2);

  if (type == 0x0004) {

    proto_tree_add_uint(subtree, hf_3com_xns_type_retix_bpdu,

        tvb, 0, 2, type);

    call_dissector(retix_bpdu_handle, next_tvb, pinfo, tree);

  } else {

    proto_tree_add_uint(subtree, hf_3com_xns_type_ethertype,

        tvb, 0, 2, type);

    if (!dissector_try_uint(ethertype_subdissector_table,

        type, next_tvb, pinfo, tree))

      call_data_dissector(next_tvb, pinfo, tree);

  }

  return tvb_captured_length(tvb);

}

void

proto_register_3com_xns(void)

{

  static hf_register_info hf[] = {

    /* registered here but handled in ethertype.c */

    { &hf_3com_xns_type_ethertype,

    { "Type", "3comxns.type", FT_UINT16, BASE_HEX,

      VALS(etype_vals), 0x0, NULL, HFILL }},

    { &hf_3com_xns_type_retix_bpdu,

    { "Type", "3comxns.type", FT_UINT16, BASE_HEX,

      VALS(retix_bpdu_type_vals), 0x0, NULL, HFILL }},

  };

  static int *ett[] ={

    &ett_3com_xns,

  };

  proto_3com_xns = proto_register_protocol("3Com XNS Encapsulation", "3COMXNS", "3comxns");

  proto_register_field_array(proto_3com_xns, hf, array_length(hf));

  proto_register_subtree_array(ett, array_length(ett));

  our_xns_handle = register_dissector("3comxns", dissect_3com_xns, proto_3com_xns);

}

void

proto_reg_handoff_3com_xns(void)

{

  retix_bpdu_handle = find_dissector_add_dependency("rbpdu", proto_3com_xns);

  ethertype_subdissector_table = find_dissector_table("ethertype");

  dissector_add_uint("llc.dsap", 0x80, our_xns_handle);

}

/*

 * 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:

 */