epan/dissectors/packet-ieee8021cb.c

   1 /* packet-ieee8021CB.c
   2  * Routines for 802.1CB R-tag ethernet header disassembly
   3  *
   4  * Copyright 2020, Rene Nielsen <rene.nielsen@microchip.com>
   5  * In association with Microchip Technology Inc.
   6  *
   7  * Wireshark - Network traffic analyzer
   8  * By Gerald Combs <gerald@wireshark.org>
   9  * Copyright 1998 Gerald Combs
  10  *
  11  * SPDX-License-Identifier: GPL-2.0-or-later
  12  */
  13
  14 #include "config.h"
  15
  16 #include <epan/packet.h>
  17 #include <epan/capture_dissectors.h>
  18 #include <wsutil/pint.h>
  19 #include <epan/addr_resolv.h>
  20
  21 #include "packet-ipx.h"
  22 #include "packet-llc.h"
  23 #include <epan/etypes.h>
  24 #include <epan/prefs.h>
  25
  26 void proto_register_ieee8021cb(void);
  27 void proto_reg_handoff_ieee8021cb(void);
  28
  29 static dissector_handle_t ieee8021cb_handle;
  30 static dissector_handle_t ethertype_handle;
  31
  32 static capture_dissector_handle_t ieee8021cb_cap_handle;
  33 static capture_dissector_handle_t ipx_cap_handle;
  34 static capture_dissector_handle_t llc_cap_handle;
  35
  36 /* GLOBALS ************************************************************/
  37
  38 static int proto_ieee8021cb;
  39
  40 /* dot1cb R-tag fields */
  41 static int hf_ieee8021cb_res;
  42 static int hf_ieee8021cb_seq;
  43
  44 /* Encapsulated protocol */
  45 static int hf_ieee8021cb_etype;
  46
  47 static int ett_ieee8021cb;
  48
  49 #define IEEE8021CB_LEN 6
  50
  51 static bool
  52 capture_ieee8021cb(const unsigned char *pd, int offset, int len, capture_packet_info_t *cpinfo, const union wtap_pseudo_header *pseudo_header)
  53 {
  54     uint16_t encap_proto;
  55
  56     if (!BYTES_ARE_IN_FRAME(offset, len, IEEE8021CB_LEN + 1))
  57         return false;
  58
  59     encap_proto = pntoh16( &pd[offset + IEEE8021CB_LEN - 2] );
  60     if (encap_proto <= IEEE_802_3_MAX_LEN) {
  61         if ( pd[offset + IEEE8021CB_LEN] == 0xff
  62              && pd[offset + IEEE8021CB_LEN + 1] == 0xff ) {
  63             return call_capture_dissector(ipx_cap_handle, pd, offset + IEEE8021CB_LEN, len, cpinfo, pseudo_header);
  64         }
  65         else {
  66             return call_capture_dissector(llc_cap_handle, pd, offset + IEEE8021CB_LEN, len, cpinfo, pseudo_header);
  67         }
  68     }
  69
  70     return try_capture_dissector("ethertype", encap_proto, pd, offset + IEEE8021CB_LEN, len, cpinfo, pseudo_header);
  71 }
  72
  73 /* Dissector *************************************************************/
  74 static
  75 int dissect_ieee8021cb(tvbuff_t *tvb, packet_info *pinfo,
  76                    proto_tree *tree, void* data _U_)
  77 {
  78     proto_tree       *ptree   = NULL;
  79     uint16_t          seq, pro;
  80     ethertype_data_t  ethertype_data;
  81     proto_tree       *ieee8021cb_tree;
  82
  83     /* add info to column display */
  84     col_set_str(pinfo->cinfo, COL_PROTOCOL, "802.1CB R-Tag");
  85     col_clear(pinfo->cinfo, COL_INFO);
  86
  87     seq = tvb_get_ntohs(tvb, 2);
  88     pro = tvb_get_ntohs(tvb, 4);
  89
  90     col_add_fstr(pinfo->cinfo, COL_INFO, "SEQ: %u", seq);
  91
  92     /* create the protocol tree */
  93     ptree = proto_tree_add_item(tree, proto_ieee8021cb, tvb, 0, IEEE8021CB_LEN, ENC_NA);
  94     ieee8021cb_tree = proto_item_add_subtree(ptree, ett_ieee8021cb);
  95
  96     /* add fields */
  97     proto_tree_add_uint(ieee8021cb_tree, hf_ieee8021cb_seq,   tvb, 2, 2, seq);
  98     proto_tree_add_uint(ieee8021cb_tree, hf_ieee8021cb_etype, tvb, 4, 2, pro);
  99
 100     proto_item_append_text(ptree, ", SEQ: %u", seq);
 101
 102     ethertype_data.fh_tree        = ieee8021cb_tree;
 103     ethertype_data.fcs_len        = 0;
 104     ethertype_data.etype          = pro;
 105     ethertype_data.payload_offset = IEEE8021CB_LEN;
 106
 107     /* 802.1CB tags are always followed by an ethertype; call next dissector
 108        based on ethertype */
 109     call_dissector_with_data(ethertype_handle, tvb, pinfo, tree, &ethertype_data);
 110
 111     return tvb_captured_length(tvb);
 112 }
 113
 114 void
 115 proto_register_ieee8021cb(void)
 116 {
 117     static hf_register_info hf_1cb[] = {
 118         { &hf_ieee8021cb_res, {
 119                 "Reserved", "ieee8021cb.reserved", FT_UINT16, BASE_HEX,
 120                 NULL, 0x0, NULL, HFILL }},
 121         { &hf_ieee8021cb_seq, {
 122                 "SEQ", "ieee8021cb.seq", FT_UINT16, BASE_HEX_DEC,
 123                 NULL, 0x0, NULL, HFILL }},
 124         { &hf_ieee8021cb_etype, {
 125                 "Type", "ieee8021cb.etype", FT_UINT16, BASE_HEX,
 126                 VALS(etype_vals), 0x0, "Ethertype", HFILL }}
 127     };
 128
 129     static int *ett[] = {
 130         &ett_ieee8021cb
 131     };
 132
 133     /* registration */
 134     proto_ieee8021cb = proto_register_protocol("802.1CB Redundancy Tag", "R-Tag", "ieee8021cb");
 135     proto_register_field_array(proto_ieee8021cb, hf_1cb, array_length(hf_1cb));
 136     proto_register_subtree_array(ett, array_length(ett));
 137
 138     ieee8021cb_handle = register_dissector("ieee8021cb", dissect_ieee8021cb, proto_ieee8021cb);
 139     ieee8021cb_cap_handle = register_capture_dissector("ieee8021cb", capture_ieee8021cb, proto_ieee8021cb);
 140 }
 141
 142 void
 143 proto_reg_handoff_ieee8021cb(void)
 144 {
 145
 146     dissector_add_uint("ethertype", ETHERTYPE_IEEE_802_1CB, ieee8021cb_handle);
 147     ethertype_handle = find_dissector_add_dependency("ethertype", proto_ieee8021cb);
 148     capture_dissector_add_uint("ethertype", ETHERTYPE_IEEE_802_1CB, ieee8021cb_cap_handle);
 149
 150     ipx_cap_handle = find_capture_dissector("ipx");
 151     llc_cap_handle = find_capture_dissector("llc");
 152 }
 153
 154 /*
 155  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 156  *
 157  * Local Variables:
 158  * c-basic-offset: 4
 159  * tab-width: 8
 160  * indent-tabs-mode: nil
 161  * End:
 162  *
 163  * ex: set shiftwidth=4 tabstop=8 expandtab:
 164  * :indentSize=4:tabSize=8:noTabs=true:
 165  */