epan/dissectors/packet-cesoeth.c

   1 /* packet-cesoeth.c
   2  * Dissection of Circuit Emulation Service over Ethernet (MEF 8)
   3  * www.mef.net
   4  *
   5  * Copyright 2018, AimValley B.V.
   6  * Jaap Keuter <jkeuter@aimvalley.nl>
   7  *
   8  * Wireshark - Network traffic analyzer
   9  * By Gerald Combs <gerald@wireshark.org>
  10  * Copyright 1998 Gerald Combs
  11  *
  12  * SPDX-License-Identifier: GPL-2.0-or-later
  13  */
  14
  15 #include "config.h"
  16
  17 #include <epan/packet.h>
  18 #include <epan/prefs.h>
  19 #include <epan/expert.h>
  20 #include <epan/etypes.h>
  21 #include "packet-rtp.h"
  22
  23 void proto_register_cesoeth(void);
  24 void proto_reg_handoff_cesoeth(void);
  25
  26 static dissector_handle_t cesoeth_handle;
  27
  28 static int proto_cesoeth;
  29 static int hf_cesoeth_pw_ecid;
  30 static int hf_cesoeth_pw_res;
  31 static int hf_cesoeth_cw;
  32 static int hf_cesoeth_cw_reserved1;
  33 static int hf_cesoeth_cw_l;
  34 static int hf_cesoeth_cw_r;
  35 static int hf_cesoeth_cw_l0_m;
  36 static int hf_cesoeth_cw_l1_m;
  37 static int hf_cesoeth_cw_frg;
  38 static int hf_cesoeth_cw_len;
  39 static int hf_cesoeth_cw_seq;
  40 static int hf_cesoeth_padding;
  41
  42 static int ett_cesoeth;
  43 static int ett_cesoeth_cw;
  44
  45 static expert_field ei_cesoeth_reserved;
  46 static expert_field ei_cesoeth_length;
  47
  48 static int* const cesoeth_l0_cw[] =
  49 {
  50     &hf_cesoeth_cw_reserved1,
  51     &hf_cesoeth_cw_l,
  52     &hf_cesoeth_cw_r,
  53     &hf_cesoeth_cw_l0_m,
  54     &hf_cesoeth_cw_frg,
  55     &hf_cesoeth_cw_len,
  56     &hf_cesoeth_cw_seq,
  57     NULL
  58 };
  59
  60 static int* const cesoeth_l1_cw[] =
  61 {
  62     &hf_cesoeth_cw_reserved1,
  63     &hf_cesoeth_cw_l,
  64     &hf_cesoeth_cw_r,
  65     &hf_cesoeth_cw_l1_m,
  66     &hf_cesoeth_cw_frg,
  67     &hf_cesoeth_cw_len,
  68     &hf_cesoeth_cw_seq,
  69     NULL
  70 };
  71
  72 static const value_string frg_names[] =
  73 {
  74     { 0, "No fragmentation" },
  75     { 1, "First fragment" },
  76     { 2, "Last fragment" },
  77     { 3, "Intermediate fragment" },
  78     { 0, NULL }
  79 };
  80
  81 static const value_string l0_m_names[] =
  82 {
  83     { 0, "No local TDM defect" },
  84     { 1, "Reserved" },
  85     { 2, "RDI on TDM input" },
  86     { 3, "Non-TDM data" },
  87     { 0, NULL }
  88 };
  89
  90 static const value_string l1_m_names[] =
  91 {
  92     { 0, "TDM defect" },
  93     { 1, "Reserved" },
  94     { 2, "Reserved" },
  95     { 3, "Reserved" },
  96     { 0, NULL }
  97 };
  98
  99 /* Preferences */
 100 static bool has_rtp_header;
 101 static bool heuristic_rtp_header = true;
 102
 103
 104 static int
 105 dissect_cesoeth(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
 106 {
 107     proto_tree  *cesoeth_tree;
 108     proto_item  *cesoeth_ti;
 109     proto_item  *bitmask_ti;
 110     int         offset = 0;
 111     uint32_t    ecid, reserved;
 112     bool        l_bit, r_bit;
 113     uint8_t     m_bits, frg;
 114     int         cw_len, padding_len, tail_len, payload_len;
 115     uint16_t    sn;
 116     tvbuff_t    *next_tvb;
 117
 118     col_set_str(pinfo->cinfo, COL_PROTOCOL, "CESoETH");
 119     col_clear(pinfo->cinfo, COL_INFO);
 120
 121     cesoeth_ti = proto_tree_add_item(tree, proto_cesoeth, tvb, 0, -1, ENC_NA);
 122     cesoeth_tree = proto_item_add_subtree(cesoeth_ti, ett_cesoeth);
 123
 124     proto_tree_add_item_ret_uint(cesoeth_tree, hf_cesoeth_pw_ecid, tvb, offset, 4, ENC_BIG_ENDIAN, &ecid);
 125     col_append_fstr(pinfo->cinfo, COL_INFO, "ECID: 0x%05x", ecid);
 126     bitmask_ti = proto_tree_add_item_ret_uint(cesoeth_tree, hf_cesoeth_pw_res, tvb, offset, 4, ENC_BIG_ENDIAN, &reserved);
 127     if (reserved != 0x102)
 128         expert_add_info_format(pinfo, bitmask_ti, &ei_cesoeth_reserved, "Reserved field must be 0x102");
 129     offset += 4;
 130
 131     /*
 132      * CES header control word
 133      *
 134      * bits  name       description
 135      * 31-28 reserved   set to 0
 136      *  27   L-bit      set to 1 to indicate local TDM failure
 137      *  26   R-bit      set to 1 to indicate remote loss of frame
 138      * 25-24 M-bits     modifier bits
 139      * 23-22 FRG bits   fragmentation bits
 140      * 21-16 length     length (0 if no padding applied)
 141      * 15-0  sequence   sequence number
 142      */
 143
 144     l_bit  = (tvb_get_uint8(tvb, offset) & 0x08) ? true : false;
 145     r_bit  = (tvb_get_uint8(tvb, offset) & 0x04) ? true : false;
 146     m_bits = (tvb_get_uint8(tvb, offset) & 0x03);
 147     frg    = tvb_get_bits8(tvb, 40, 2);
 148     cw_len = tvb_get_bits8(tvb, 42, 6);
 149     sn     = tvb_get_ntohs(tvb, offset + 2);
 150
 151     col_append_fstr(pinfo->cinfo, COL_INFO, ", SN: %u", sn);
 152
 153     if (l_bit)
 154     {
 155         bitmask_ti = proto_tree_add_bitmask(cesoeth_tree, tvb, offset, hf_cesoeth_cw, ett_cesoeth_cw, cesoeth_l1_cw, ENC_NA);
 156         col_append_sep_fstr(pinfo->cinfo, COL_INFO, NULL, "%s", val_to_str_const(m_bits, l1_m_names, "Unknown"));
 157     } else {
 158         bitmask_ti = proto_tree_add_bitmask(cesoeth_tree, tvb, offset, hf_cesoeth_cw, ett_cesoeth_cw, cesoeth_l0_cw, ENC_NA);
 159         if (m_bits)
 160             col_append_sep_fstr(pinfo->cinfo, COL_INFO, NULL, "%s", val_to_str_const(m_bits, l0_m_names, "Unknown"));
 161     }
 162
 163     if (cw_len >= 42)
 164     {
 165         /*
 166          * Now we have to go spelunking in the bitmask tree for the length item
 167          * in order to add an expert item to it.
 168          */
 169         proto_tree *bm_tree = proto_item_get_subtree(bitmask_ti);
 170         if (bm_tree) {
 171             proto_item *pi;
 172
 173             for (pi = tree->first_child; pi; pi = pi->next)
 174             {
 175                 field_info *fi;
 176                 fi = PITEM_FINFO(pi);
 177                 if (fi && (fi->hfinfo->id == hf_cesoeth_cw_len))
 178                     break;
 179             }
 180
 181             expert_add_info_format(pinfo, pi, &ei_cesoeth_length, "Length can not be 42 or larger");
 182         }
 183
 184         cw_len = 0; /* Put a stop to this madness */
 185     }
 186
 187     if (r_bit)
 188         col_append_sep_str(pinfo->cinfo, COL_INFO, NULL, "Remote loss of frame");
 189
 190     if (frg)
 191         col_append_sep_fstr(pinfo->cinfo, COL_INFO, NULL, "%s", val_to_str_const(frg, frg_names, "Unknown"));
 192
 193     offset += 4;
 194
 195     /*
 196      * When L is set the TDM payload MAY be missing.
 197      * But also when snap value is used on capture.
 198      * Will the optional RTP header be there when the TDM payload is missing? I guess so.
 199      * Length includes the size of the CW (being 4), the optional RTP header (being 12) and
 200      * the TDM payload, as long as it doesn't exceed 42 octets. Length > 0 indicates padding,
 201      * which must NOT be passed to the RTP dissector, it's not RTP padding.
 202      */
 203
 204     padding_len = (cw_len > 0) ? (42 - cw_len) : 0;
 205     tail_len = tvb_reported_length_remaining(tvb, offset);
 206     payload_len = tail_len - padding_len;
 207
 208     if (payload_len > 0)
 209     {
 210         next_tvb = tvb_new_subset_length(tvb, offset, payload_len);
 211
 212         if ((has_rtp_header) ||
 213             ((heuristic_rtp_header) &&
 214                 /* Check for RTP version 2, the other fields must be zero */
 215                 (tvb_get_uint8(tvb, offset) == 0x80) &&
 216                 /* Check the marker is zero. Unfortunately PT is not always from the dynamic range */
 217                 ((tvb_get_uint8(tvb, offset + 1) & 0x80) == 0) &&
 218                 /* The sequence numbers from cw and RTP header must match */
 219                 (tvb_get_ntohs(tvb, offset + 2) == sn)))
 220         {
 221             struct _rtp_info rtp_info;
 222
 223             int rtp_header_len = dissect_rtp_shim_header(tvb, offset, pinfo, cesoeth_tree, &rtp_info);
 224
 225             col_set_str(pinfo->cinfo, COL_PROTOCOL, "CESoETH (w RTP)");
 226             col_append_sep_fstr(pinfo->cinfo, COL_INFO, NULL, "RTP PT: %u, SSRC: 0x%X, Seq: %u, Time=%u",
 227                                 rtp_info.info_payload_type,
 228                                 rtp_info.info_sync_src,
 229                                 rtp_info.info_seq_num,
 230                                 rtp_info.info_timestamp
 231                                );
 232
 233             next_tvb = tvb_new_subset_length(tvb, offset + rtp_header_len, payload_len - rtp_header_len);
 234         }
 235
 236         call_data_dissector(next_tvb, pinfo, tree);
 237
 238         offset += payload_len;
 239     }
 240
 241     if (padding_len > 0)
 242     {
 243         proto_tree_add_item(cesoeth_tree, hf_cesoeth_padding, tvb, offset, padding_len, ENC_NA);
 244
 245         offset += padding_len;
 246     }
 247
 248     return offset;
 249 }
 250
 251 void
 252 proto_register_cesoeth(void)
 253 {
 254     static hf_register_info hf[] = {
 255         { &hf_cesoeth_pw_ecid,
 256             { "ECID", "cesoeth.ecid", FT_UINT32, BASE_HEX,
 257             NULL, 0xFFFFF000, NULL, HFILL }},
 258         { &hf_cesoeth_pw_res,
 259             { "Reserved", "cesoeth.res", FT_UINT32, BASE_HEX,
 260             NULL, 0x00000FFF, "Reserved (0x102)", HFILL }},
 261
 262         { &hf_cesoeth_cw,
 263             { "Control word", "cesoeth.cw", FT_UINT32, BASE_HEX,
 264             NULL, 0x0, NULL, HFILL }},
 265
 266         { &hf_cesoeth_cw_reserved1,
 267             { "Reserved", "cesoeth.cw.reserved", FT_UINT32, BASE_HEX,
 268             NULL, 0xF0000000, NULL, HFILL }},
 269         { &hf_cesoeth_cw_l,
 270             { "L-bit", "cesoeth.cw.l", FT_BOOLEAN, 32,
 271             NULL, 0x08000000, "Local TDM failure", HFILL }},
 272         { &hf_cesoeth_cw_r,
 273             { "R-bit", "cesoeth.cw.r", FT_BOOLEAN, 32,
 274             NULL, 0x04000000, "Remote Loss of Frames indication", HFILL }},
 275         { &hf_cesoeth_cw_l0_m,
 276             { "M-bits", "cesoeth.cw.m", FT_UINT32, BASE_HEX,
 277             VALS(l0_m_names), 0x03000000, "Modifier bits", HFILL }},
 278         { &hf_cesoeth_cw_l1_m,
 279             { "M-bits", "cesoeth.cw.m", FT_UINT32, BASE_HEX,
 280             VALS(l1_m_names), 0x03000000, "Modifier bits", HFILL }},
 281         { &hf_cesoeth_cw_frg,
 282             { "Frg", "cesoeth.cw.frg", FT_UINT32, BASE_HEX,
 283             VALS(frg_names), 0x00C00000, "Fragmentation bits", HFILL }},
 284         { &hf_cesoeth_cw_len,
 285             { "Len", "cesoeth.cw.len", FT_UINT32, BASE_DEC,
 286             NULL, 0x003F0000, "Length", HFILL }},
 287         { &hf_cesoeth_cw_seq,
 288             { "SN", "cesoeth.cw.sn", FT_UINT32, BASE_DEC,
 289             NULL, 0x0000FFFF, "Sequence number", HFILL }},
 290
 291         { &hf_cesoeth_padding,
 292             { "Padding", "cesoeth.padding", FT_BYTES, BASE_NONE,
 293             NULL, 0x0, NULL, HFILL }}
 294     };
 295
 296     static int *ett[] = {
 297         &ett_cesoeth,
 298         &ett_cesoeth_cw
 299     };
 300
 301     static ei_register_info ei[] = {
 302         { &ei_cesoeth_reserved,
 303             { "cesoeth.reserved", PI_PROTOCOL, PI_WARN,
 304               "Reserved field", EXPFILL }},
 305         { &ei_cesoeth_length,
 306             { "cesoeth.length", PI_PROTOCOL, PI_WARN,
 307               "Length field", EXPFILL }}
 308     };
 309
 310     module_t *cesoeth_module;
 311     expert_module_t* expert_cesoeth;
 312
 313     proto_cesoeth = proto_register_protocol("Circuit Emulation Service over Ethernet", "CESoETH", "cesoeth");
 314     proto_register_field_array(proto_cesoeth, hf, array_length(hf));
 315     proto_register_subtree_array(ett, array_length(ett));
 316     expert_cesoeth = expert_register_protocol(proto_cesoeth);
 317     expert_register_field_array(expert_cesoeth, ei, array_length(ei));
 318
 319     cesoeth_module = prefs_register_protocol(proto_cesoeth, NULL);
 320
 321     prefs_register_bool_preference(cesoeth_module, "rtp_header", "RTP header in CES payload",
 322                                    "Whether or not the RTP header is present in the CES payload.", &has_rtp_header);
 323
 324     prefs_register_bool_preference(cesoeth_module, "rtp_header_heuristic", "Try to find RTP header in CES payload",
 325                                    "Heuristically determine if an RTP header is present in the CES payload.", &heuristic_rtp_header);
 326
 327
 328     cesoeth_handle = register_dissector("cesoeth", dissect_cesoeth, proto_cesoeth);
 329 }
 330
 331 void
 332 proto_reg_handoff_cesoeth(void)
 333 {
 334     dissector_add_uint("ethertype", ETHERTYPE_CESOETH, cesoeth_handle);
 335 }
 336
 337 /*
 338  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 339  *
 340  * Local variables:
 341  * c-basic-offset: 4
 342  * tab-width: 8
 343  * indent-tabs-mode: nil
 344  * End:
 345  *
 346  * vi: set shiftwidth=4 tabstop=8 expandtab:
 347  * :indentSize=4:tabSize=8:noTabs=true:
 348  */