/* packet-caneth.c

 * Routines for Controller Area Network over Ethernet dissection

 * Copyright 2018, Lazar Sumar <bugzilla@lazar.co.nz>

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998 Gerald Combs

 *

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

 */

/*

 * The CAN-ETH protocol is used for transmitting the Controller Area Network

 * (CAN) protocol over UDP.

 *

 * The protocol definition can be found at http://www.proconx.com/assets/files/products/caneth/canframe.pdf

 */

#include <config.h>

#include <epan/packet.h>

#include "packet-udp.h"

#include "packet-socketcan.h"

#define CAN_FRAME_LEN   15

#define CAN_ID_OFFSET       0

#define CAN_DLC_OFFSET      4

#define CAN_DATA_OFFSET     5

#define CAN_EXT_FLAG_OFFSET 13

#define CAN_RTR_FLAG_OFFSET 14

static const char magic[] = "ISO11898";

void proto_reg_handoff_caneth(void);

void proto_register_caneth(void);

static dissector_handle_t caneth_handle;

static int proto_caneth;

static int hf_caneth_magic;

static int hf_caneth_version;

static int hf_caneth_frames;

static int hf_caneth_options;

static int hf_caneth_can_ident_ext;

static int hf_caneth_can_ident_std;

static int hf_caneth_can_extflag;

static int hf_caneth_can_rtrflag;

static int hf_caneth_can_len;

static int hf_caneth_can_padding;

#define CANETH_UDP_PORT 11898

static int ett_caneth;

static int ett_caneth_frames;

static int ett_caneth_can;

static int proto_can;      // use CAN protocol for consistent filtering

/* A sample #define of the minimum length (in bytes) of the protocol data.

 * If data is received with fewer than this many bytes it is rejected by

 * the current dissector. */

#define CANETH_MIN_LENGTH 10

static bool

test_caneth(packet_info *pinfo _U_, tvbuff_t *tvb, int offset, void *data _U_)

{

    /* Check that we have enough length for the Magic, Version, and Length */

    if (tvb_reported_length(tvb) < CANETH_MIN_LENGTH)

        return false;

    /* Check that the magic id matches */

    if (tvb_strneql(tvb, offset, magic, 8) != 0)

        return false;

    /* Check that the version is 1 as that is the only supported version */

    if (tvb_get_uint8(tvb, offset+8) != 1)

        return false;

    /* Check that the version 1 limit of 16 can frames is respected */

    if (tvb_get_uint8(tvb, offset+9) > 16)

        return false;

    return true;

}

static unsigned

get_caneth_len(packet_info *pinfo _U_, tvbuff_t *tvb, int offset, void *data _U_)

{

    return (unsigned) tvb_get_ntohs(tvb, offset+3);

}

static int

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

{

    proto_tree *can_tree;

    proto_item *ti;

    uint32_t    raw_can_id;

    int8_t      ext_flag;

    int8_t      rtr_flag;

    tvbuff_t*   next_tvb;

    struct can_info can_info;

    ti = proto_tree_add_item(tree, proto_can, tvb, 0, -1, ENC_NA);

    can_tree = proto_item_add_subtree(ti, ett_caneth_can);

    ext_flag = tvb_get_uint8(tvb, CAN_EXT_FLAG_OFFSET);

    rtr_flag = tvb_get_uint8(tvb, CAN_RTR_FLAG_OFFSET);

    if (ext_flag)

    {

        proto_tree_add_item_ret_uint(can_tree, hf_caneth_can_ident_ext, tvb, CAN_ID_OFFSET, 4, ENC_LITTLE_ENDIAN, &raw_can_id);

        can_info.id = raw_can_id & CAN_EFF_MASK;

    }

    else

    {

        proto_tree_add_item_ret_uint(can_tree, hf_caneth_can_ident_std, tvb, CAN_ID_OFFSET, 4, ENC_LITTLE_ENDIAN, &raw_can_id);

        can_info.id = raw_can_id & CAN_SFF_MASK;

    }

    can_info.id |= (ext_flag ? CAN_EFF_FLAG : 0) | (rtr_flag ? CAN_RTR_FLAG : 0);

    can_info.fd = CAN_TYPE_CAN_CLASSIC;

    can_info.bus_id = 0; /* see get_bus_id in packet-socketcan.c? */

    proto_tree_add_item_ret_uint(can_tree, hf_caneth_can_len, tvb, CAN_DLC_OFFSET, 1, ENC_NA, &can_info.len);

    proto_tree_add_item(can_tree, hf_caneth_can_extflag, tvb, CAN_EXT_FLAG_OFFSET, 1, ENC_NA);

    proto_tree_add_item(can_tree, hf_caneth_can_rtrflag, tvb, CAN_RTR_FLAG_OFFSET, 1, ENC_NA);

    next_tvb = tvb_new_subset_length(tvb, CAN_DATA_OFFSET, can_info.len);

    if (!socketcan_call_subdissectors(next_tvb, pinfo, tree, &can_info, false)) {

        call_data_dissector(next_tvb, pinfo, tree);

    }

    if (tvb_captured_length_remaining(tvb, CAN_DATA_OFFSET + can_info.len) > 0)

    {

        proto_tree_add_item(can_tree, hf_caneth_can_padding, tvb, CAN_DATA_OFFSET + can_info.len, -1, ENC_NA);

    }

    return tvb_captured_length(tvb);

}

static int

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

{

    proto_tree *caneth_tree;

    proto_item *ti;

    uint32_t    frame_count, offset;

    tvbuff_t*   next_tvb;

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

        return 0;

    col_set_str(pinfo->cinfo, COL_PROTOCOL, "CAN-ETH");

    col_clear(pinfo->cinfo, COL_INFO);

    ti = proto_tree_add_item(tree, proto_caneth, tvb, 0, -1, ENC_NA);

    caneth_tree = proto_item_add_subtree(ti, ett_caneth);

    proto_tree_add_item(caneth_tree, hf_caneth_magic, tvb, 0, 8, ENC_ASCII);

    proto_tree_add_item(caneth_tree, hf_caneth_version, tvb, 8, 1, ENC_NA);

    proto_tree_add_item_ret_uint(caneth_tree, hf_caneth_frames, tvb, 9, 1, ENC_NA, &frame_count);

    for (offset = 10; frame_count-- > 0; offset += CAN_FRAME_LEN)

    {

        next_tvb = tvb_new_subset_length(tvb, offset, CAN_FRAME_LEN);

        dissect_caneth_can(next_tvb, pinfo, tree, data);

    }

    if (tvb_captured_length_remaining(tvb, offset) > 0)

    {

        proto_tree_add_item(caneth_tree, hf_caneth_options, tvb, offset, -1, ENC_NA);

    }

    return tvb_captured_length(tvb);

}

static bool

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

{

    return (udp_dissect_pdus(tvb, pinfo, tree, CANETH_MIN_LENGTH, test_caneth,

                     get_caneth_len, dissect_caneth, data) != 0);

}

void

proto_register_caneth(void)

{

    static hf_register_info hf[] = {

        {

            &hf_caneth_magic,

            {

                "Magic", "caneth.magic",

                FT_STRING, BASE_NONE,

                NULL, 0x0,

                "The magic identifier used to denote the start of a CAN-ETH packet", HFILL

            }

        },

        {

            &hf_caneth_version,

            {

                "Version", "caneth.version",

                FT_UINT8, BASE_DEC,

                NULL, 0x0,

                NULL, HFILL

            }

        },

        {

            &hf_caneth_frames,

            {

                "CAN Frames", "caneth.frames",

                FT_UINT8, BASE_DEC,

                NULL, 0x0,

                "Number of enclosed CAN frames", HFILL

            }

        },

        {

            &hf_caneth_options,

            {

                "Options (Reserved)", "caneth.options",

                FT_BYTES, BASE_NONE,

                NULL, 0x0,

                "Options field, reserved for future use, should be empty", HFILL

            }

        },

        {

            &hf_caneth_can_ident_ext,

            {

                "Identifier", "can.id",

                FT_UINT32, BASE_HEX,

                NULL, CAN_EFF_MASK,

                NULL, HFILL

            }

        },

        {

            &hf_caneth_can_ident_std,

            {

                "Identifier", "can.id",

                FT_UINT32, BASE_HEX,

                NULL, CAN_SFF_MASK,

                NULL, HFILL

            }

        },

        {

            &hf_caneth_can_extflag,

            {

                "Extended Flag", "can.flags.xtd",

                FT_BOOLEAN, BASE_NONE,

                NULL, 0,

                NULL, HFILL

            }

        },

        {

            &hf_caneth_can_rtrflag,

            {

                "Remote Transmission Request Flag", "can.flags.rtr",

                FT_BOOLEAN, BASE_NONE,

                NULL, 0,

                NULL, HFILL

            }

        },

        {

            &hf_caneth_can_len,

            {

                "Frame-Length", "can.len",

                FT_UINT8, BASE_DEC,

                NULL, 0x0,

                NULL, HFILL

            }

        },

        {

            &hf_caneth_can_padding,

            {

                "Padding", "caneth.can.padding",

                FT_BYTES, BASE_NONE,

                NULL, 0x0,

                NULL, HFILL

            }

        },

    };

    static int *ett[] = {

        &ett_caneth,

        &ett_caneth_frames,

        &ett_caneth_can,

    };

    proto_caneth = proto_register_protocol("Controller Area Network over Ethernet", "CAN-ETH", "caneth");

    proto_register_field_array(proto_caneth, hf, array_length(hf));

    proto_register_subtree_array(ett, array_length(ett));

    caneth_handle = register_dissector("caneth", dissect_caneth, proto_caneth);

}

void

proto_reg_handoff_caneth(void)

{

    dissector_add_uint_with_preference("udp.port", CANETH_UDP_PORT, caneth_handle);

    heur_dissector_add("udp", dissect_caneth_heur_udp, "CAN-ETH over UDP", "caneth_udp", proto_caneth, HEURISTIC_DISABLE);

    proto_can = proto_get_id_by_filter_name("can");

}

/*

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

 *

 * Local variables:

 * c-basic-offset: 4

 * tab-width: 8

 * indent-tabs-mode: nil

 * End:

 *

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

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

 */