epan/dissectors/packet-3com-xns.c

   1 /* packet-xns-llc.c
   2  * Routines for 3Com's encapsulation of XNS over 802.2 LLC
   3  * (and other protocols using DSAP 80)
   4  *
   5  * Wireshark - Network traffic analyzer
   6  * By Gerald Combs <gerald@wireshark.org>
   7  * Copyright 1998 Gerald Combs
   8  *
   9  * SPDX-License-Identifier: GPL-2.0-or-later
  10  */
  11
  12 #include "config.h"
  13
  14 #include <epan/packet.h>
  15 #include <epan/etypes.h>
  16
  17 /* Forward declarations */
  18 void proto_register_3com_xns(void);
  19 void proto_reg_handoff_3com_xns(void);
  20
  21 static dissector_handle_t our_xns_handle;
  22
  23 static int proto_3com_xns;
  24
  25 static int hf_3com_xns_type_ethertype;
  26 static int hf_3com_xns_type_retix_bpdu;
  27
  28 static int ett_3com_xns;
  29
  30 static const value_string retix_bpdu_type_vals[] = {
  31         { 0x0004, "Retix Spanning Tree" },
  32         { 0, NULL }
  33 };
  34
  35 static dissector_table_t ethertype_subdissector_table;
  36
  37 static dissector_handle_t retix_bpdu_handle;
  38
  39 /*
  40  * Apparently 3Com had some scheme for encapsulating XNS in 802.2 LLC,
  41  * using a DSAP and SSAP of 0x80, and putting a 2-byte field that appeared
  42  * to contain, at least for IPP, the Ethertype value for IPP.
  43  *
  44  * We assume that the value there is an Ethertype value, except for
  45  * the Retix spanning tree protocol, which also uses a DSAP and SSAP
  46  * of 0x80 but has, at least in one capture, 0x0004 as the type
  47  * field.  We handle that specially.
  48  *
  49  * XXX - I've also seen packets on 802.11 with a DSAP and SSAP of 0x80,
  50  * but with random stuff that appears neither to be XNS nor Retix
  51  * spanning tree.
  52  */
  53 static int
  54 dissect_3com_xns(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
  55 {
  56         proto_tree *subtree;
  57         proto_tree *ti;
  58         uint16_t type;
  59         tvbuff_t *next_tvb;
  60
  61         col_set_str(pinfo->cinfo, COL_PROTOCOL, "3Com XNS");
  62         col_clear(pinfo->cinfo, COL_INFO);
  63
  64         ti = proto_tree_add_item(tree, proto_3com_xns, tvb, 0, 4, ENC_NA);
  65         subtree = proto_item_add_subtree(ti, ett_3com_xns);
  66
  67         type = tvb_get_ntohs(tvb, 0);
  68         next_tvb = tvb_new_subset_remaining(tvb, 2);
  69         if (type == 0x0004) {
  70                 proto_tree_add_uint(subtree, hf_3com_xns_type_retix_bpdu,
  71                     tvb, 0, 2, type);
  72                 call_dissector(retix_bpdu_handle, next_tvb, pinfo, tree);
  73         } else {
  74                 proto_tree_add_uint(subtree, hf_3com_xns_type_ethertype,
  75                     tvb, 0, 2, type);
  76                 if (!dissector_try_uint(ethertype_subdissector_table,
  77                     type, next_tvb, pinfo, tree))
  78                         call_data_dissector(next_tvb, pinfo, tree);
  79         }
  80         return tvb_captured_length(tvb);
  81 }
  82
  83 void
  84 proto_register_3com_xns(void)
  85 {
  86         static hf_register_info hf[] = {
  87                 /* registered here but handled in ethertype.c */
  88                 { &hf_3com_xns_type_ethertype,
  89                 { "Type", "3comxns.type", FT_UINT16, BASE_HEX,
  90                         VALS(etype_vals), 0x0, NULL, HFILL }},
  91
  92                 { &hf_3com_xns_type_retix_bpdu,
  93                 { "Type", "3comxns.type", FT_UINT16, BASE_HEX,
  94                         VALS(retix_bpdu_type_vals), 0x0, NULL, HFILL }},
  95         };
  96
  97         static int *ett[] ={
  98                 &ett_3com_xns,
  99         };
 100
 101         proto_3com_xns = proto_register_protocol("3Com XNS Encapsulation", "3COMXNS", "3comxns");
 102         proto_register_field_array(proto_3com_xns, hf, array_length(hf));
 103         proto_register_subtree_array(ett, array_length(ett));
 104
 105         our_xns_handle = register_dissector("3comxns", dissect_3com_xns, proto_3com_xns);
 106 }
 107
 108 void
 109 proto_reg_handoff_3com_xns(void)
 110 {
 111         retix_bpdu_handle = find_dissector_add_dependency("rbpdu", proto_3com_xns);
 112         ethertype_subdissector_table = find_dissector_table("ethertype");
 113         dissector_add_uint("llc.dsap", 0x80, our_xns_handle);
 114 }
 115
 116 /*
 117  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 118  *
 119  * Local variables:
 120  * c-basic-offset: 8
 121  * tab-width: 8
 122  * indent-tabs-mode: t
 123  * End:
 124  *
 125  * vi: set shiftwidth=8 tabstop=8 noexpandtab:
 126  * :indentSize=8:tabSize=8:noTabs=false:
 127  */