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packet-3com-xns.c

/* packet-xns-llc.c
 * Routines for 3Com's encapsulation of XNS over 802.2 LLC
 * (and other protocols using DSAP 80)
 *
 * $Id: packet-3com-xns.c 28273 2009-05-05 03:50:06Z guy $
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998 Gerald Combs
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <glib.h>
#include <epan/packet.h>
#include <epan/etypes.h>

static int proto_3com_xns = -1;

static int hf_3com_xns_type_ethertype = -1;
static int hf_3com_xns_type_retix_bpdu = -1;

static gint ett_3com_xns = -1;

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;
static dissector_handle_t data_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 void
dissect_3com_xns(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
      proto_tree *subtree = NULL;
      proto_tree *ti;
      guint16 type;
      tvbuff_t *next_tvb;

      if (check_col(pinfo->cinfo, COL_PROTOCOL))
            col_set_str(pinfo->cinfo, COL_PROTOCOL, "3Com XNS");
      if (check_col(pinfo->cinfo, COL_INFO))
            col_clear(pinfo->cinfo, COL_INFO);

      if (tree) {
            ti = proto_tree_add_item(tree, proto_3com_xns, tvb, 0, 4, FALSE);
            subtree = proto_item_add_subtree(ti, ett_3com_xns);
      }

      type = tvb_get_ntohs(tvb, 0);
      next_tvb = tvb_new_subset(tvb, 2, -1, -1);
      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_port(ethertype_subdissector_table,
                type, next_tvb, pinfo, tree))
                  call_dissector(data_handle, next_tvb, pinfo, tree);
      }
}

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, "", HFILL }},

            { &hf_3com_xns_type_retix_bpdu,
            { "Type", "3comxns.type", FT_UINT16, BASE_HEX,
                  VALS(retix_bpdu_type_vals), 0x0, "", HFILL }},
      };

      static gint *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));
}

void
proto_reg_handoff_3com_xns(void)
{
      dissector_handle_t our_xns_handle;

      retix_bpdu_handle = find_dissector("rbpdu");
      data_handle = find_dissector("data");

      ethertype_subdissector_table = find_dissector_table("ethertype");

      our_xns_handle = create_dissector_handle(dissect_3com_xns, proto_3com_xns);
      dissector_add("llc.dsap", 0x80, our_xns_handle);
}

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