epan/dissectors/packet-rmt-alc.c

   1 /* packet-rmt-alc.c
   2  * Reliable Multicast Transport (RMT)
   3  * ALC Protocol Instantiation dissector
   4  * Copyright 2005, Stefano Pettini <spettini@users.sourceforge.net>
   5  * Copyright 2023, Sergey V. Lobanov <sergey@lobanov.in>
   6  *
   7  * Asynchronous Layered Coding (ALC):
   8  * ----------------------------------
   9  *
  10  * A massively scalable reliable content delivery protocol.
  11  * Asynchronous Layered Coding combines the Layered Coding Transport
  12  * (LCT) building block, a multiple rate congestion control building
  13  * block and the Forward Error Correction (FEC) building block to
  14  * provide congestion controlled reliable asynchronous delivery of
  15  * content to an unlimited number of concurrent receivers from a single
  16  * sender.
  17  *
  18  * References:
  19  *     RFC 3450, Asynchronous Layered Coding protocol instantiation
  20  *
  21  * Wireshark - Network traffic analyzer
  22  * By Gerald Combs <gerald@wireshark.org>
  23  * Copyright 1998 Gerald Combs
  24  *
  25  * SPDX-License-Identifier: GPL-2.0-or-later
  26  */
  27
  28 #include "config.h"
  29
  30 #include <epan/packet.h>
  31 #include <epan/prefs.h>
  32 #include <epan/expert.h>
  33 #include <epan/conversation.h>
  34 #include <wiretap/wtap.h>
  35 #include <wsutil/array.h>
  36
  37 #include "packet-rmt-common.h"
  38 #include "packet-lls.h"
  39
  40 /* Initialize the protocol and registered fields */
  41 /* ============================================= */
  42 static dissector_handle_t alc_handle;
  43
  44 void proto_register_alc(void);
  45 void proto_reg_handoff_alc(void);
  46
  47 static int proto_rmt_alc;
  48
  49 static int hf_version;
  50 static int hf_atsc3;
  51 static int hf_object_start_offset;
  52 static int hf_payload;
  53 static int hf_uncomp_payload;
  54
  55 static int ett_main;
  56 static int ett_uncomp_payload;
  57 static int ett_uncomp_decode;
  58
  59 static expert_field ei_version1_only;
  60
  61 static dissector_handle_t xml_handle;
  62 static dissector_handle_t rmt_lct_handle;
  63 static dissector_handle_t rmt_fec_handle;
  64
  65 static dissector_table_t media_type_dissector_table;
  66
  67 static bool g_codepoint_as_fec_encoding = true;
  68 static int      g_ext_192                   = LCT_PREFS_EXT_192_FLUTE;
  69 static int      g_ext_193                   = LCT_PREFS_EXT_193_FLUTE;
  70 static int      g_atsc3_mode                = LCT_ATSC3_MODE_AUTO;
  71
  72 static void
  73 try_decode_payload(tvbuff_t *tvb, packet_info *pinfo, proto_item *tree)
  74 {
  75     uint32_t b03 = tvb_get_uint32(tvb, 0, ENC_BIG_ENDIAN);
  76     /* xml ("<?xm") */
  77     if (b03 == 0x3C3F786D) {
  78         call_dissector(xml_handle, tvb, pinfo, tree);
  79     } else {
  80         uint32_t b47 = tvb_get_uint32(tvb, 4, ENC_BIG_ENDIAN);
  81         /* mp4 ("ftyp" or "sidx" or "styp" mp4 box) */
  82         if (b47 == 0x66747970 || b47 == 0x73696478 || b47 == 0x73747970) {
  83             /* MP4 dissector removes useful info from Protocol and Info columns so store it */
  84             char *col_info_text = wmem_strdup(pinfo->pool, col_get_text(pinfo->cinfo, COL_INFO));
  85             char *col_protocol_text = wmem_strdup(pinfo->pool, col_get_text(pinfo->cinfo, COL_PROTOCOL));
  86
  87             int mp4_dis = dissector_try_string_with_data(media_type_dissector_table, "video/mp4", tvb, pinfo, tree, true, NULL);
  88             char *col_protocol_text_mp4 = wmem_strdup(pinfo->pool,col_get_text(pinfo->cinfo, COL_PROTOCOL));
  89
  90             /* Restore Protocol and Info columns and add MP4 Protocol Info */
  91             col_set_str(pinfo->cinfo, COL_INFO, col_info_text);
  92             col_set_str(pinfo->cinfo, COL_PROTOCOL, col_protocol_text);
  93             if (mp4_dis > 0) {
  94                 col_append_sep_str(pinfo->cinfo, COL_PROTOCOL, "/", col_protocol_text_mp4);
  95             }
  96         }
  97     }
  98 }
  99
 100 static void
 101 try_uncompress(tvbuff_t *tvb, packet_info *pinfo, int offset, /*int len,*/ proto_item *ti)
 102 {
 103     tvbuff_t *uncompress_tvb = tvb_uncompress_zlib(tvb, offset, tvb_captured_length(tvb) - offset);
 104     if (uncompress_tvb) {
 105         add_new_data_source(pinfo, uncompress_tvb, "Uncompressed Payload");
 106
 107         proto_tree *uncompress_tree = proto_item_add_subtree(ti, ett_uncomp_payload);
 108         unsigned decomp_length = tvb_captured_length(uncompress_tvb);
 109         proto_item *ti_uncomp = proto_tree_add_item(uncompress_tree, hf_uncomp_payload, uncompress_tvb, 0, decomp_length, ENC_ASCII);
 110         proto_item_set_generated(ti_uncomp);
 111
 112         proto_tree *payload_tree = proto_item_add_subtree(ti_uncomp, ett_uncomp_decode);
 113         try_decode_payload(uncompress_tvb, pinfo, payload_tree);
 114     }
 115 }
 116
 117 /* Code to actually dissect the packets */
 118 /* ==================================== */
 119 static int
 120 dissect_alc(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
 121 {
 122     uint8_t             version;
 123     lct_data_exchange_t lct;
 124     fec_data_exchange_t fec;
 125     int                 len;
 126     bool                is_atsc3;
 127
 128     if (g_atsc3_mode == LCT_ATSC3_MODE_FORCE) {
 129         is_atsc3 = true;
 130     } else if (g_atsc3_mode == LCT_ATSC3_MODE_DISABLED) {
 131         is_atsc3 = false;
 132     } else { /* Auto detect mode*/
 133         /* If packet encap is ALP then it is necessary to use ATSC decoding mode*/
 134         is_atsc3 = pinfo->rec->rec_header.packet_header.pkt_encap == WTAP_ENCAP_ATSC_ALP;
 135     }
 136
 137     /* Offset for subpacket dissection */
 138     unsigned offset = 0;
 139
 140     /* Set up structures needed to add the protocol subtree and manage it */
 141     proto_item *ti;
 142     proto_tree *alc_tree;
 143
 144     tvbuff_t *new_tvb;
 145
 146     /* Make entries in Protocol column and Info column on summary display */
 147     col_set_str(pinfo->cinfo, COL_PROTOCOL, "ALC");
 148     col_clear(pinfo->cinfo, COL_INFO);
 149
 150     /* ALC header dissection */
 151     /* --------------------- */
 152
 153     version = hi_nibble(tvb_get_uint8(tvb, offset));
 154
 155     /* Create subtree for the ALC protocol */
 156     ti = proto_tree_add_item(tree, proto_rmt_alc, tvb, offset, -1, ENC_NA);
 157     alc_tree = proto_item_add_subtree(ti, ett_main);
 158
 159     /* Fill the ALC subtree */
 160     ti = proto_tree_add_uint(alc_tree, hf_version, tvb, offset, 1, version);
 161     PROTO_ITEM_SET_GENERATED(
 162         proto_tree_add_boolean(alc_tree, hf_atsc3, 0, 0, 0, is_atsc3)
 163     );
 164
 165     /* This dissector supports only ALCv1 packets.
 166      * If version > 1 print only version field and quit.
 167      */
 168     if (version != 1) {
 169         expert_add_info(pinfo, ti, &ei_version1_only);
 170
 171         /* Complete entry in Info column on summary display */
 172         col_add_fstr(pinfo->cinfo, COL_INFO, "Version: %u (not supported)", version);
 173         return 0;
 174     }
 175
 176     /* LCT header dissection */
 177     /* --------------------- */
 178     new_tvb = tvb_new_subset_remaining(tvb,offset);
 179
 180     lct.ext_192 = g_ext_192;
 181     lct.ext_193 = g_ext_193;
 182     lct.codepoint = 0;
 183     lct.is_flute = false;
 184     lct.is_atsc3 = is_atsc3;
 185     lct.is_sp = false;
 186     len = call_dissector_with_data(rmt_lct_handle, new_tvb, pinfo, alc_tree, &lct);
 187     if (len < 0)
 188         return offset;
 189
 190     offset += len;
 191
 192     /* FEC header dissection */
 193     /* --------------------- */
 194
 195     /* Only if LCT dissector has determined FEC Encoding ID */
 196     /* FEC dissector needs to be called with encoding_id filled */
 197     if (!lct.is_sp && g_codepoint_as_fec_encoding && tvb_reported_length(tvb) > offset)
 198     {
 199         fec.encoding_id = lct.codepoint;
 200
 201         new_tvb = tvb_new_subset_remaining(tvb,offset);
 202         len = call_dissector_with_data(rmt_fec_handle, new_tvb, pinfo, alc_tree, &fec);
 203         if (len < 0)
 204             return offset;
 205
 206         offset += len;
 207     }
 208
 209     /* A/331 specifies start_offset field */
 210     int64_t object_start_offset = -1;
 211     if (lct.is_sp) {
 212         object_start_offset = tvb_get_uint32(tvb, offset, 4);
 213         proto_tree_add_item(alc_tree, hf_object_start_offset, tvb, offset, 4, ENC_BIG_ENDIAN);
 214         offset += 4;
 215     }
 216
 217     /* Add the Payload item */
 218     if (tvb_reported_length(tvb) > offset){
 219         if(lct.is_flute){
 220             new_tvb = tvb_new_subset_remaining(tvb,offset);
 221             call_dissector(xml_handle, new_tvb, pinfo, alc_tree);
 222         }else{
 223             ti = proto_tree_add_item(alc_tree, hf_payload, tvb, offset, -1, ENC_NA);
 224             if (object_start_offset == 0 &&
 225                 tvb_captured_length_remaining(tvb, offset) > 18 &&
 226                 tvb_get_uint16(tvb, offset, ENC_BIG_ENDIAN) == 0x1f8b) {
 227                 /* gzip is detected */
 228                 try_uncompress(tvb, pinfo, offset, ti);
 229             } else if (object_start_offset == 0) {
 230                 /* gzip is not detected */
 231                 new_tvb = tvb_new_subset_remaining(tvb, offset);
 232                 try_decode_payload(new_tvb, pinfo, alc_tree);
 233             }
 234         }
 235     }
 236
 237     /* Add Channel info in ATSC3 mode */
 238     if(lct.is_atsc3) {
 239         char *channel_info = get_slt_channel_info(pinfo);
 240         if (channel_info != NULL) {
 241             col_append_sep_str(pinfo->cinfo, COL_INFO, " ", channel_info);
 242             wmem_free(pinfo->pool, channel_info);
 243         }
 244     }
 245
 246     return tvb_reported_length(tvb);
 247 }
 248
 249
 250 static bool
 251 dissect_alc_heur_udp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)
 252 {
 253     /* Lookup over ATSC3 SLT Table*/
 254     if (!test_alc_over_slt(pinfo, tvb, 0, data))
 255         return false;
 256
 257     conversation_t *conversation = find_or_create_conversation(pinfo);
 258     conversation_set_dissector(conversation, alc_handle);
 259
 260     return (dissect_alc(tvb, pinfo, tree, data) != 0);
 261 }
 262
 263 void proto_register_alc(void)
 264 {
 265     /* Setup ALC header fields */
 266     static hf_register_info hf_ptr[] = {
 267
 268         { &hf_version,
 269           { "Version", "alc.version", FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL }},
 270
 271         { &hf_atsc3,
 272           { "Decode as ATSC3", "alc.atsc3", FT_BOOLEAN, BASE_NONE, NULL, 0x0, NULL, HFILL }},
 273
 274         { &hf_object_start_offset,
 275           { "Object Start Offset", "alc.object_start_offset", FT_UINT32, BASE_DEC, NULL, 0x0, NULL, HFILL }},
 276
 277         { &hf_payload,
 278           { "Payload", "alc.payload", FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL }},
 279
 280         { &hf_uncomp_payload,
 281           { "Uncompressed Payload", "alc.payload.uncompressed", FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL }},
 282     };
 283
 284     /* Setup protocol subtree array */
 285     static int *ett_ptr[] = {
 286         &ett_main,
 287         &ett_uncomp_payload,
 288         &ett_uncomp_decode,
 289     };
 290
 291     static ei_register_info ei[] = {
 292         { &ei_version1_only, { "alc.version1_only", PI_PROTOCOL, PI_WARN, "Sorry, this dissector supports ALC version 1 only", EXPFILL }},
 293     };
 294
 295     module_t *module;
 296     expert_module_t* expert_rmt_alc;
 297
 298     /* Register the protocol name and description */
 299     proto_rmt_alc = proto_register_protocol("Asynchronous Layered Coding", "ALC", "alc");
 300     alc_handle = register_dissector("alc", dissect_alc, proto_rmt_alc);
 301
 302     /* Register the header fields and subtrees used */
 303     proto_register_field_array(proto_rmt_alc, hf_ptr, array_length(hf_ptr));
 304     proto_register_subtree_array(ett_ptr, array_length(ett_ptr));
 305     expert_rmt_alc = expert_register_protocol(proto_rmt_alc);
 306     expert_register_field_array(expert_rmt_alc, ei, array_length(ei));
 307
 308     /* Register preferences */
 309     module = prefs_register_protocol(proto_rmt_alc, NULL);
 310
 311     prefs_register_obsolete_preference(module, "default.udp_port.enabled");
 312
 313     prefs_register_bool_preference(module,
 314                                    "lct.codepoint_as_fec_id",
 315                                    "LCT Codepoint as FEC Encoding ID",
 316                                    "Whether the LCT header Codepoint field should be considered the FEC Encoding ID of carried object",
 317                                    &g_codepoint_as_fec_encoding);
 318
 319     prefs_register_enum_preference(module,
 320                                    "lct.ext.192",
 321                                    "LCT header extension 192",
 322                                    "How to decode LCT header extension 192",
 323                                    &g_ext_192,
 324                                    enum_lct_ext_192,
 325                                    false);
 326
 327     prefs_register_enum_preference(module,
 328                                    "lct.ext.193",
 329                                    "LCT header extension 193",
 330                                    "How to decode LCT header extension 193",
 331                                    &g_ext_193,
 332                                    enum_lct_ext_193,
 333                                    false);
 334
 335     prefs_register_enum_preference(module,
 336                                    "lct.atsc3.mode",
 337                                    "ATSC3 Mode",
 338                                    "How to detect ATSC3 data",
 339                                    &g_atsc3_mode,
 340                                    enum_lct_atsc3_mode,
 341                                    false);
 342 }
 343
 344 void proto_reg_handoff_alc(void)
 345 {
 346     dissector_add_for_decode_as_with_preference("udp.port", alc_handle);
 347     xml_handle = find_dissector_add_dependency("xml", proto_rmt_alc);
 348     rmt_lct_handle = find_dissector_add_dependency("rmt-lct", proto_rmt_alc);
 349     rmt_fec_handle = find_dissector_add_dependency("rmt-fec", proto_rmt_alc);
 350     heur_dissector_add("udp", dissect_alc_heur_udp, "Asynchronous Layered Coding",
 351                        "alc", proto_rmt_alc, HEURISTIC_ENABLE);
 352
 353     media_type_dissector_table = find_dissector_table("media_type");
 354 }
 355
 356 /*
 357  * Editor modelines - https://www.wireshark.org/tools/modelines.html
 358  *
 359  * Local variables:
 360  * c-basic-offset: 4
 361  * tab-width: 8
 362  * indent-tabs-mode: nil
 363  * End:
 364  *
 365  * ex: set shiftwidth=4 tabstop=8 expandtab:
 366  * :indentSize=4:tabSize=8:noTabs=true:
 367  */