/* packet-rmt-alc.c

 * Reliable Multicast Transport (RMT)

 * ALC Protocol Instantiation dissector

 * Copyright 2005, Stefano Pettini <spettini@users.sourceforge.net>

 * Copyright 2023, Sergey V. Lobanov <sergey@lobanov.in>

 *

 * Asynchronous Layered Coding (ALC):

 * ----------------------------------

 *

 * A massively scalable reliable content delivery protocol.

 * Asynchronous Layered Coding combines the Layered Coding Transport

 * (LCT) building block, a multiple rate congestion control building

 * block and the Forward Error Correction (FEC) building block to

 * provide congestion controlled reliable asynchronous delivery of

 * content to an unlimited number of concurrent receivers from a single

 * sender.

 *

 * References:

 *     RFC 3450, Asynchronous Layered Coding protocol instantiation

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998 Gerald Combs

 *

 * SPDX-License-Identifier: GPL-2.0-or-later

 */

#include "config.h"

#include <epan/packet.h>

#include <epan/prefs.h>

#include <epan/expert.h>

#include <epan/conversation.h>

#include <wiretap/wtap.h>

#include <wsutil/array.h>

#include "packet-rmt-common.h"

#include "packet-lls.h"

/* Initialize the protocol and registered fields */

/* ============================================= */

static dissector_handle_t alc_handle;

void proto_register_alc(void);

void proto_reg_handoff_alc(void);

static int proto_rmt_alc;

static int hf_version;

static int hf_atsc3;

static int hf_object_start_offset;

static int hf_payload;

static int hf_uncomp_payload;

static int ett_main;

static int ett_uncomp_payload;

static int ett_uncomp_decode;

static expert_field ei_version1_only;

static dissector_handle_t xml_handle;

static dissector_handle_t rmt_lct_handle;

static dissector_handle_t rmt_fec_handle;

static dissector_table_t media_type_dissector_table;

static bool g_codepoint_as_fec_encoding = true;

static int      g_ext_192                   = LCT_PREFS_EXT_192_FLUTE;

static int      g_ext_193                   = LCT_PREFS_EXT_193_FLUTE;

static int      g_atsc3_mode                = LCT_ATSC3_MODE_AUTO;

static void

try_decode_payload(tvbuff_t *tvb, packet_info *pinfo, proto_item *tree)

{

    uint32_t b03 = tvb_get_uint32(tvb, 0, ENC_BIG_ENDIAN);

    /* xml ("<?xm") */

    if (b03 == 0x3C3F786D) {

        call_dissector(xml_handle, tvb, pinfo, tree);

    } else {

        uint32_t b47 = tvb_get_uint32(tvb, 4, ENC_BIG_ENDIAN);

        /* mp4 ("ftyp" or "sidx" or "styp" mp4 box) */

        if (b47 == 0x66747970 || b47 == 0x73696478 || b47 == 0x73747970) {

            /* MP4 dissector removes useful info from Protocol and Info columns so store it */

            char *col_info_text = wmem_strdup(pinfo->pool, col_get_text(pinfo->cinfo, COL_INFO));

            char *col_protocol_text = wmem_strdup(pinfo->pool, col_get_text(pinfo->cinfo, COL_PROTOCOL));

            int mp4_dis = dissector_try_string_with_data(media_type_dissector_table, "video/mp4", tvb, pinfo, tree, true, NULL);

            char *col_protocol_text_mp4 = wmem_strdup(pinfo->pool,col_get_text(pinfo->cinfo, COL_PROTOCOL));

            /* Restore Protocol and Info columns and add MP4 Protocol Info */

            col_set_str(pinfo->cinfo, COL_INFO, col_info_text);

            col_set_str(pinfo->cinfo, COL_PROTOCOL, col_protocol_text);

            if (mp4_dis > 0) {

                col_append_sep_str(pinfo->cinfo, COL_PROTOCOL, "/", col_protocol_text_mp4);

            }

        }

    }

}

static void

try_uncompress(tvbuff_t *tvb, packet_info *pinfo, int offset, /*int len,*/ proto_item *ti)

{

    tvbuff_t *uncompress_tvb = tvb_child_uncompress_zlib(tvb, tvb, offset, tvb_captured_length_remaining(tvb, offset));

    if (uncompress_tvb) {

        add_new_data_source(pinfo, uncompress_tvb, "Uncompressed Payload");

        proto_tree *uncompress_tree = proto_item_add_subtree(ti, ett_uncomp_payload);

        unsigned decomp_length = tvb_captured_length(uncompress_tvb);

        proto_item *ti_uncomp = proto_tree_add_item(uncompress_tree, hf_uncomp_payload, uncompress_tvb, 0, decomp_length, ENC_NA);

        proto_item_set_generated(ti_uncomp);

        proto_tree *payload_tree = proto_item_add_subtree(ti_uncomp, ett_uncomp_decode);

        try_decode_payload(uncompress_tvb, pinfo, payload_tree);

    }

}

/* Code to actually dissect the packets */

/* ==================================== */

static int

dissect_alc(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)

{

    uint8_t             version;

    lct_data_exchange_t lct;

    fec_data_exchange_t fec;

    int                 len;

    bool                is_atsc3;

    if (g_atsc3_mode == LCT_ATSC3_MODE_FORCE) {

        is_atsc3 = true;

    } else if (g_atsc3_mode == LCT_ATSC3_MODE_DISABLED) {

        is_atsc3 = false;

    } else { /* Auto detect mode*/

        /* If packet encap is ALP then it is necessary to use ATSC decoding mode*/

        is_atsc3 = pinfo->rec->rec_header.packet_header.pkt_encap == WTAP_ENCAP_ATSC_ALP;

    }

    /* Offset for subpacket dissection */

    unsigned offset = 0;

    /* Set up structures needed to add the protocol subtree and manage it */

    proto_item *ti;

    proto_tree *alc_tree;

    tvbuff_t *new_tvb;

    /* Make entries in Protocol column and Info column on summary display */

    col_set_str(pinfo->cinfo, COL_PROTOCOL, "ALC");

    col_clear(pinfo->cinfo, COL_INFO);

    /* ALC header dissection */

    /* --------------------- */

    version = hi_nibble(tvb_get_uint8(tvb, offset));

    /* Create subtree for the ALC protocol */

    ti = proto_tree_add_item(tree, proto_rmt_alc, tvb, offset, -1, ENC_NA);

    alc_tree = proto_item_add_subtree(ti, ett_main);

    /* Fill the ALC subtree */

    ti = proto_tree_add_uint(alc_tree, hf_version, tvb, offset, 1, version);

    PROTO_ITEM_SET_GENERATED(

        proto_tree_add_boolean(alc_tree, hf_atsc3, 0, 0, 0, is_atsc3)

    );

    /* This dissector supports only ALCv1 packets.

     * If version > 1 print only version field and quit.

     */

    if (version != 1) {

        expert_add_info(pinfo, ti, &ei_version1_only);

        /* Complete entry in Info column on summary display */

        col_add_fstr(pinfo->cinfo, COL_INFO, "Version: %u (not supported)", version);

        return 0;

    }

    /* LCT header dissection */

    /* --------------------- */

    new_tvb = tvb_new_subset_remaining(tvb,offset);

    lct.ext_192 = g_ext_192;

    lct.ext_193 = g_ext_193;

    lct.codepoint = 0;

    lct.is_flute = false;

    lct.is_atsc3 = is_atsc3;

    lct.is_sp = false;

    len = call_dissector_with_data(rmt_lct_handle, new_tvb, pinfo, alc_tree, &lct);

    if (len < 0)

        return offset;

    offset += len;

    /* FEC header dissection */

    /* --------------------- */

    /* Only if LCT dissector has determined FEC Encoding ID */

    /* FEC dissector needs to be called with encoding_id filled */

    if (!lct.is_sp && g_codepoint_as_fec_encoding && tvb_reported_length(tvb) > offset)

    {

        fec.encoding_id = lct.codepoint;

        new_tvb = tvb_new_subset_remaining(tvb,offset);

        len = call_dissector_with_data(rmt_fec_handle, new_tvb, pinfo, alc_tree, &fec);

        if (len < 0)

            return offset;

        offset += len;

    }

    /* A/331 specifies start_offset field */

    int64_t object_start_offset = -1;

    if (lct.is_sp) {

        object_start_offset = tvb_get_uint32(tvb, offset, ENC_BIG_ENDIAN);

        proto_tree_add_item(alc_tree, hf_object_start_offset, tvb, offset, 4, ENC_BIG_ENDIAN);

        offset += 4;

    }

    /* Add the Payload item */

    if (tvb_reported_length(tvb) > offset){

        if(lct.is_flute){

            new_tvb = tvb_new_subset_remaining(tvb,offset);

            call_dissector(xml_handle, new_tvb, pinfo, alc_tree);

        }else{

            ti = proto_tree_add_item(alc_tree, hf_payload, tvb, offset, -1, ENC_NA);

            if (object_start_offset == 0 &&

                tvb_captured_length_remaining(tvb, offset) > 18 &&

                tvb_get_uint16(tvb, offset, ENC_BIG_ENDIAN) == 0x1f8b) {

                /* gzip is detected */

                try_uncompress(tvb, pinfo, offset, ti);

            } else if (object_start_offset == 0) {

                /* gzip is not detected */

                new_tvb = tvb_new_subset_remaining(tvb, offset);

                try_decode_payload(new_tvb, pinfo, alc_tree);

            }

        }

    }

    /* Add Channel info in ATSC3 mode */

    if(lct.is_atsc3) {

        char *channel_info = get_slt_channel_info(pinfo);

        if (channel_info != NULL) {

            col_append_sep_str(pinfo->cinfo, COL_INFO, " ", channel_info);

            wmem_free(pinfo->pool, channel_info);

        }

    }

    return tvb_reported_length(tvb);

}

static bool

dissect_alc_heur_udp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)

{

    /* Lookup over ATSC3 SLT Table*/

    if (!test_alc_over_slt(pinfo, tvb, 0, data))

        return false;

    conversation_t *conversation = find_or_create_conversation(pinfo);

    conversation_set_dissector(conversation, alc_handle);

    return (dissect_alc(tvb, pinfo, tree, data) != 0);

}

void proto_register_alc(void)

{

    /* Setup ALC header fields */

    static hf_register_info hf_ptr[] = {

        { &hf_version,

          { "Version", "alc.version", FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL }},

        { &hf_atsc3,

          { "Decode as ATSC3", "alc.atsc3", FT_BOOLEAN, BASE_NONE, NULL, 0x0, NULL, HFILL }},

        { &hf_object_start_offset,

          { "Object Start Offset", "alc.object_start_offset", FT_UINT32, BASE_DEC, NULL, 0x0, NULL, HFILL }},

        { &hf_payload,

          { "Payload", "alc.payload", FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL }},

        { &hf_uncomp_payload,

          { "Uncompressed Payload", "alc.payload.uncompressed", FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL }},

    };

    /* Setup protocol subtree array */

    static int *ett_ptr[] = {

        &ett_main,

        &ett_uncomp_payload,

        &ett_uncomp_decode,

    };

    static ei_register_info ei[] = {

        { &ei_version1_only, { "alc.version1_only", PI_PROTOCOL, PI_WARN, "Sorry, this dissector supports ALC version 1 only", EXPFILL }},

    };

    module_t *module;

    expert_module_t* expert_rmt_alc;

    /* Register the protocol name and description */

    proto_rmt_alc = proto_register_protocol("Asynchronous Layered Coding", "ALC", "alc");

    alc_handle = register_dissector("alc", dissect_alc, proto_rmt_alc);

    /* Register the header fields and subtrees used */

    proto_register_field_array(proto_rmt_alc, hf_ptr, array_length(hf_ptr));

    proto_register_subtree_array(ett_ptr, array_length(ett_ptr));

    expert_rmt_alc = expert_register_protocol(proto_rmt_alc);

    expert_register_field_array(expert_rmt_alc, ei, array_length(ei));

    /* Register preferences */

    module = prefs_register_protocol(proto_rmt_alc, NULL);

    prefs_register_obsolete_preference(module, "default.udp_port.enabled");

    prefs_register_bool_preference(module,

                                   "lct.codepoint_as_fec_id",

                                   "LCT Codepoint as FEC Encoding ID",

                                   "Whether the LCT header Codepoint field should be considered the FEC Encoding ID of carried object",

                                   &g_codepoint_as_fec_encoding);

    prefs_register_enum_preference(module,

                                   "lct.ext.192",

                                   "LCT header extension 192",

                                   "How to decode LCT header extension 192",

                                   &g_ext_192,

                                   enum_lct_ext_192,

                                   false);

    prefs_register_enum_preference(module,

                                   "lct.ext.193",

                                   "LCT header extension 193",

                                   "How to decode LCT header extension 193",

                                   &g_ext_193,

                                   enum_lct_ext_193,

                                   false);

    prefs_register_enum_preference(module,

                                   "lct.atsc3.mode",

                                   "ATSC3 Mode",

                                   "How to detect ATSC3 data",

                                   &g_atsc3_mode,

                                   enum_lct_atsc3_mode,

                                   false);

}

void proto_reg_handoff_alc(void)

{

    dissector_add_for_decode_as_with_preference("udp.port", alc_handle);

    xml_handle = find_dissector_add_dependency("xml", proto_rmt_alc);

    rmt_lct_handle = find_dissector_add_dependency("rmt-lct", proto_rmt_alc);

    rmt_fec_handle = find_dissector_add_dependency("rmt-fec", proto_rmt_alc);

    heur_dissector_add("udp", dissect_alc_heur_udp, "Asynchronous Layered Coding",

                       "alc", proto_rmt_alc, HEURISTIC_ENABLE);

    media_type_dissector_table = find_dissector_table("media_type");

}

/*

 * Editor modelines - https://www.wireshark.org/tools/modelines.html

 *

 * Local variables:

 * c-basic-offset: 4

 * tab-width: 8

 * indent-tabs-mode: nil

 * End:

 *

 * ex: set shiftwidth=4 tabstop=8 expandtab:

 * :indentSize=4:tabSize=8:noTabs=true:

 */