epan/dissectors/packet-sync.c

   1 /* packet-sync.c
   2  * Routines for MBMS synchronisation protocol dissection
   3  * Copyright 2012, David Wei <davidwei@lavabit.com>
   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  * Ref 3GPP TS 25.446
  12  */
  13
  14 #include "config.h"
  15
  16 #include <epan/packet.h>
  17 #include <epan/expert.h>
  18 #include <epan/crc6-tvb.h>
  19 #include <epan/unit_strings.h>
  20
  21 #include <wsutil/array.h>
  22
  23 #define TYPE_0_LEN 17
  24 #define TYPE_1_LEN 11
  25 #define TYPE_2_LEN 12
  26 #define TYPE_3_LEN 19
  27
  28 void proto_register_sync(void);
  29 void proto_reg_handoff_sync(void);
  30
  31 /* Initialize the protocol and registered fields */
  32 static int proto_sync;
  33 static int hf_sync_type;
  34 static int hf_sync_spare4;
  35 static int hf_sync_timestamp;
  36 static int hf_sync_packet_nr;
  37 static int hf_sync_elapsed_octet_ctr;
  38 static int hf_sync_total_nr_of_packet;
  39 static int hf_sync_total_nr_of_octet;
  40 static int hf_sync_header_crc;
  41 static int hf_sync_payload_crc;
  42 static int hf_sync_length_of_packet;
  43
  44 /* Initialize the subtree pointers */
  45 static int ett_sync;
  46
  47 static expert_field ei_sync_pdu_type2;
  48 static expert_field ei_sync_type;
  49
  50 static dissector_handle_t sync_handle;
  51 static dissector_handle_t ip_handle;
  52
  53 static const value_string sync_type_vals[] = {
  54     { 0, "Synchronisation frame without payload" },
  55     { 1, "User data with synchronisation frame for uncompressed headers" },
  56     { 2, "User data with synchronisation frame for compressed headers" },
  57     { 3, "Synchronisation frame with Length of Packets" },
  58     /* 4-15 reserved for future PDU type extensions */
  59     { 0, NULL}
  60 };
  61
  62 static int
  63 dissect_sync(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
  64 {
  65     proto_item *ti, *item, *type_item;
  66     proto_tree *sync_tree;
  67     uint8_t     type, spare;
  68     uint16_t    packet_nr, packet_len1, packet_len2;
  69     uint32_t    timestamp, total_nr_of_packet;
  70     int         offset = 0;
  71     tvbuff_t   *next_tvb;
  72
  73     type  = tvb_get_uint8(tvb, offset) >> 4;
  74     spare = tvb_get_uint8(tvb, offset) & 0x0F;
  75
  76     /* Heuristics to check if packet is really MBMS sync */
  77 #if 0
  78     if ( type > 3 )
  79         return 0;
  80
  81     if ( type == 0 && tvb_captured_length(tvb) < 18) {
  82         return 0;
  83     } else if ( type == 1 && tvb_captured_length(tvb) < 11 ) {
  84         return 0;
  85     } else if ( type == 3 && tvb_captured_length(tvb) < 19 ) {
  86         return 0;
  87     }
  88
  89     if ( (type != 2) && (spare != 0) )
  90         return 0;
  91 #endif
  92
  93     col_set_str(pinfo->cinfo, COL_PROTOCOL, "SYNC");
  94     col_set_str(pinfo->cinfo, COL_INFO, "MBMS synchronisation protocol");
  95
  96     /* Ugly, but necessary to get the correct length for type 3 */
  97     packet_nr = tvb_get_ntohs(tvb, offset+3) + 1;
  98
  99         /* The length varies depending on PDU type */
 100         switch (type) {
 101             case 0:
 102                 ti = proto_tree_add_item(tree, proto_sync, tvb, 0, TYPE_0_LEN, ENC_NA);
 103                 break;
 104             case 1:
 105                 ti = proto_tree_add_item(tree, proto_sync, tvb, 0, TYPE_1_LEN, ENC_NA);
 106                 break;
 107             case 2:
 108                 ti = proto_tree_add_item(tree, proto_sync, tvb, 0, TYPE_2_LEN + (spare & 0x01 ? 40 : 20), ENC_NA);
 109                 break;
 110             case 3:
 111                 ti = proto_tree_add_item(tree, proto_sync, tvb, 0,
 112                                          TYPE_3_LEN + (int16_t)(packet_nr % 2 == 0 ?
 113                                                                1.5*packet_nr : 1.5*(packet_nr-1)+2),
 114                                          ENC_NA);
 115                 break;
 116             default:
 117                 ti = proto_tree_add_item(tree, proto_sync, tvb, 0, -1, ENC_NA);
 118                 break;
 119         }
 120
 121         sync_tree = proto_item_add_subtree(ti, ett_sync);
 122
 123         /* Octet 1 - PDU Type */
 124         type_item = proto_tree_add_item(sync_tree, hf_sync_type, tvb, offset, 1, ENC_BIG_ENDIAN);
 125         proto_tree_add_item(sync_tree, hf_sync_spare4, tvb, offset, 1, ENC_BIG_ENDIAN);
 126         offset++;
 127
 128         /* Octet 2 - Time Stamp */
 129         timestamp = tvb_get_ntohs(tvb, offset) * 10;
 130         proto_tree_add_uint(sync_tree, hf_sync_timestamp, tvb, offset, 2, timestamp);
 131         offset += 2;
 132
 133         /* Octet 4 - Packet Number */
 134         proto_tree_add_uint(sync_tree, hf_sync_packet_nr, tvb, offset, 2, packet_nr);
 135         offset += 2;
 136
 137         /* Octet 6 - Elapsed Octet Counter */
 138         proto_tree_add_item(sync_tree, hf_sync_elapsed_octet_ctr, tvb, offset, 4, ENC_BIG_ENDIAN);
 139         offset += 4;
 140
 141         switch (type) {
 142             case 0:
 143                 /* SYNC PDU Type 0 */
 144                 proto_tree_add_item(sync_tree, hf_sync_total_nr_of_packet, tvb, offset, 3, ENC_BIG_ENDIAN);
 145                 offset += 3;
 146                 proto_tree_add_item(sync_tree, hf_sync_total_nr_of_octet, tvb, offset, 5, ENC_BIG_ENDIAN);
 147                 offset += 5;
 148                 proto_tree_add_item(sync_tree, hf_sync_header_crc, tvb, offset, 1, ENC_BIG_ENDIAN);
 149                 offset++;
 150                 break;
 151             case 1:
 152                 /* SYNC PDU Type 1 */
 153                 /* XXX - Calculate the CRC and check against this value? */
 154                 item = proto_tree_add_item(sync_tree, hf_sync_header_crc, tvb, offset, 1, ENC_BIG_ENDIAN);
 155                 proto_tree_add_item(sync_tree, hf_sync_payload_crc, tvb, offset, 2, ENC_BIG_ENDIAN);
 156                 proto_item_append_text(item, " [Calculated CRC 0x%x]",
 157                                         crc6_compute_tvb(tvb, offset));
 158                 offset += 2;
 159
 160                 /* XXX - The payload may not always be present? */
 161                 next_tvb = tvb_new_subset_remaining(tvb, offset);
 162                 /* XXX - The payload may not always be IP? */
 163                 call_dissector(ip_handle, next_tvb, pinfo, tree);
 164                 break;
 165             case 2:
 166                 /* SYNC PDU Type 2 */
 167                 expert_add_info(pinfo, ti, &ei_sync_pdu_type2);
 168                 break;
 169             case 3:
 170                 /* SYNC PDU Type 3 */
 171                 total_nr_of_packet = tvb_get_ntoh24(tvb, offset);
 172                 proto_tree_add_item(sync_tree, hf_sync_total_nr_of_packet, tvb, offset, 3, ENC_BIG_ENDIAN);
 173                 offset += 3;
 174                 proto_tree_add_item(sync_tree, hf_sync_total_nr_of_octet, tvb, offset, 5, ENC_BIG_ENDIAN);
 175                 offset += 5;
 176                 proto_tree_add_item(sync_tree, hf_sync_header_crc, tvb, offset, 1, ENC_BIG_ENDIAN);
 177                 proto_tree_add_item(sync_tree, hf_sync_payload_crc, tvb, offset, 2, ENC_BIG_ENDIAN);
 178                 offset += 2;
 179
 180                 if (offset < (int)tvb_reported_length(tvb)) {
 181                     int i;
 182
 183                     if (total_nr_of_packet != 0 && packet_nr % 2 == 0) {
 184                         /* Even number of packets */
 185                         for (i = 1; i < packet_nr; i+=2, offset+=3) {
 186                             packet_len1 = tvb_get_bits16(tvb, offset*8,    12, ENC_BIG_ENDIAN);
 187                             packet_len2 = tvb_get_bits16(tvb, offset*8+12, 12, ENC_BIG_ENDIAN);
 188                             proto_tree_add_uint_format(sync_tree, hf_sync_length_of_packet, tvb, offset,   2, packet_len1, "Length of Packet %u : %hu", i,   packet_len1);
 189                             proto_tree_add_uint_format(sync_tree, hf_sync_length_of_packet, tvb, offset+1, 2, packet_len2, "Length of Packet %u : %hu", i+1, packet_len2);
 190                         }
 191                     } else {
 192                         /* Odd number of packets */
 193                         for (i = 1; i < packet_nr; i+=2, offset+=3) {
 194                             packet_len1 = tvb_get_bits16(tvb, offset*8,    12, ENC_BIG_ENDIAN);
 195                             packet_len2 = tvb_get_bits16(tvb, offset*8+12, 12, ENC_BIG_ENDIAN);
 196                             proto_tree_add_uint_format(sync_tree, hf_sync_length_of_packet, tvb, offset,   2, packet_len1, "Length of Packet %u : %hu", i,   packet_len1);
 197                             proto_tree_add_uint_format(sync_tree, hf_sync_length_of_packet, tvb, offset+1, 2, packet_len2, "Length of Packet %u : %hu", i+1, packet_len2);
 198                         }
 199                         packet_len1 = tvb_get_bits16(tvb, offset*8, 12, ENC_BIG_ENDIAN);
 200                         proto_tree_add_uint_format(sync_tree, hf_sync_length_of_packet, tvb, offset, 2, packet_len1, "Length of Packet %u : %hu", packet_nr, packet_len1);
 201                         offset++;
 202                         proto_tree_add_item(sync_tree, hf_sync_spare4, tvb, offset, 1, ENC_BIG_ENDIAN);
 203                     }
 204
 205                 }
 206                 break;
 207             default:
 208                 expert_add_info(pinfo, type_item, &ei_sync_type);
 209                 break;
 210         }
 211
 212     return tvb_captured_length(tvb);
 213
 214 }
 215
 216 void
 217 proto_register_sync(void)
 218 {
 219     static hf_register_info hf_sync[] = {
 220         { &hf_sync_type,
 221             { "PDU Type", "sync.type",
 222             FT_UINT8, BASE_DEC, VALS(sync_type_vals), 0xF0,
 223             NULL, HFILL }
 224         },
 225         { &hf_sync_spare4,
 226             { "Spare", "sync.spare",
 227             FT_UINT8, BASE_DEC, NULL, 0x0F,
 228             NULL, HFILL }
 229         },
 230         { &hf_sync_timestamp,
 231             { "Timestamp", "sync.timestamp",
 232             FT_UINT16, BASE_DEC|BASE_UNIT_STRING, UNS(&units_milliseconds), 0x0,
 233             "Relative time value for the starting time of a synchronisation sequence within the synchronisation period.", HFILL }
 234         },
 235         { &hf_sync_packet_nr,
 236             { "Packet Number", "sync.packet_nr",
 237             FT_UINT16, BASE_DEC, NULL, 0x0,
 238             "Number of elapsed SYNC PDUs cumulatively within the synchronisation sequence.", HFILL }
 239         },
 240         { &hf_sync_elapsed_octet_ctr,
 241             { "Elapsed Octet Counter", "sync.elapsed_octet_ctr",
 242             FT_UINT32, BASE_DEC, NULL, 0x0,
 243             "Number of elapsed cumulative octets cumulatively within one synchronisation sequence.", HFILL }
 244         },
 245         { &hf_sync_total_nr_of_packet,
 246             { "Total Number of Packet", "sync.total_nr_of_packet",
 247             FT_UINT24, BASE_DEC, NULL, 0x0,
 248             "Cumulatively the number of the packets for the MBMS service within one synchronisation period.", HFILL }
 249         },
 250         { &hf_sync_total_nr_of_octet,
 251             { "Total Number of Octet", "sync.total_nr_of_octet",
 252             FT_UINT64, BASE_DEC, NULL, 0x0,
 253             "Cumulatively the number of the octets for the MBMS service within one synchronisation period.", HFILL }
 254         },
 255         { &hf_sync_header_crc,
 256             { "Header CRC", "sync.header_crc",
 257             FT_UINT8, BASE_HEX, NULL, 0xFC,
 258             NULL, HFILL }
 259         },
 260         { &hf_sync_payload_crc,
 261             { "Payload CRC", "sync.payload_crc",
 262             FT_UINT16, BASE_HEX, NULL, 0x03FF,
 263             NULL, HFILL }
 264         },
 265         { &hf_sync_length_of_packet,
 266             { "Length of Packet", "sync.length_of_packet",
 267             FT_UINT16, BASE_DEC, NULL, 0x0,
 268             NULL, HFILL }
 269         },
 270     };
 271
 272     static int *ett_sync_array[] = {
 273         &ett_sync
 274     };
 275
 276     static ei_register_info ei[] = {
 277         { &ei_sync_pdu_type2, { "sync.pdu_type2", PI_UNDECODED, PI_WARN, "SYNC PDU type 2 unsupported", EXPFILL }},
 278         { &ei_sync_type, { "sync.type.unknown", PI_PROTOCOL, PI_WARN, "Unknown SYNC PDU type", EXPFILL }},
 279     };
 280
 281     expert_module_t* expert_sync;
 282
 283     proto_sync = proto_register_protocol("MBMS synchronisation protocol", "SYNC", "sync");
 284
 285     proto_register_field_array(proto_sync, hf_sync, array_length(hf_sync));
 286     proto_register_subtree_array(ett_sync_array, array_length(ett_sync_array));
 287     expert_sync = expert_register_protocol(proto_sync);
 288     expert_register_field_array(expert_sync, ei, array_length(ei));
 289
 290     sync_handle = register_dissector("sync", dissect_sync, proto_sync);
 291 }
 292
 293 void
 294 proto_reg_handoff_sync(void)
 295 {
 296     ip_handle   = find_dissector_add_dependency("ip", proto_sync);
 297
 298     dissector_add_for_decode_as_with_preference("udp.port", sync_handle);
 299 }
 300
 301 /*
 302  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 303  *
 304  * Local variables:
 305  * c-basic-offset: 4
 306  * tab-width: 8
 307  * indent-tabs-mode: nil
 308  * End:
 309  *
 310  * vi: set shiftwidth=4 tabstop=8 expandtab:
 311  * :indentSize=4:tabSize=8:noTabs=true:
 312  */