/* packet-docsis.c

 * Routines for docsis dissection

 * Copyright 2002, Anand V. Narwani <anand[AT]narwani.org>

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998 Gerald Combs

 *

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

 */

/* This code is based on the DOCSIS 1.1 specification available at:

 * https://www.cablelabs.com/specifications/radio-frequency-interface-specification

 *

 * This code was updated to include DOCSIS 3.1 specification details available at:

 * https://www.cablelabs.com/specifications/CM-SP-MULPIv3.1

 *

 * Updates are backward compatible with previous DOCSIS specifications.

 *

 * DOCSIS Captures can be facilitated using the Cable Monitor Feature

 * available on Cisco Cable Modem Termination Systems:

 * https://www.cisco.com/c/en/us/td/docs/cable/cmts/config_guide/b_cmts_security_and_cable_monitoring_features/b_cmts_security_and_cable_monitoring_features_chapter_010.html

 *

 * This dissector depends on the presence of a DOCSIS encapsulation type.

 * There is no simple way to distinguish DOCSIS Frames from Ethernet frames,

 * since the frames are copied from the RF interface on the CMTS to

 * a Fast Ethernet interface; thus a preference was needed to enable

 * the DOCSIS encapsulation type.

 *

 * Libpcap 0.7 and later allow a link-layer header type to be specified for

 * some interfaces on some platforms; for Ethernet interfaces, they allow

 * DOCSIS to be specified.  If an Ethernet capture is done with a link-layer

 * type of DOCSIS, the file will have a link-layer header type of DLT_DOCSIS;

 * Wireshark will treat the frames in that capture as DOCSIS frames, even

 * if the preference mentioned above isn't enabled.

 */

#include "config.h"

#include <epan/etypes.h>

#include <epan/expert.h>

#include <epan/packet.h>

#include <epan/prefs.h>

#include <epan/reassemble.h>

#include <epan/addr_resolv.h>

#include <epan/exceptions.h>

#include <epan/tfs.h>

#include <epan/crc16-tvb.h>

#include <epan/crc32-tvb.h>

void proto_register_docsis(void);

void proto_reg_handoff_docsis(void);

/* Assume all packets have an FCS */

static bool docsis_check_fcs = true;

static bool docsis_dissect_encrypted_frames;

#define DOCSIS_MIN_HEADER_LEN   6

#define FCTYPE_PACKET   0x00

#define FCTYPE_SPECIAL  0x01

#define FCTYPE_ISOLAT   0x02

#define FCTYPE_MACSPC   0x03

#define FCPARM_TIMING_HDR           0x00

#define FCPARM_MAC_MGMT_HDR         0x01

#define FCPARM_RQST_FRM             0x02

#define FCPARM_FRAG_HDR             0x03

#define FCPARM_QUEUE_DEPTH_REQ_FRM  0x04

#define FCPARM_CONCAT_HDR           0x1C

#define EXT_HDR_OFF     0x00

#define EXT_HDR_ON      0x01

#define FRAG_FCS_LEN    4

#define FRAG_FIRST      0x20

#define FRAG_MIDDLE     0x00

#define FRAG_LAST       0x10

#define EH_NULL_CONFIG      0

#define EH_REQUEST          1

#define EH_ACK_REQ          2

#define EH_BP_UP            3

#define EH_BP_DOWN          4

#define EH_SFLOW_HDR_DOWN   5

#define EH_SFLOW_HDR_UP     6

#define EH_BP_UP2           7

#define EH_DS_SERVICE       8

#define EH_PATH_VERIFY      9

#define EH_RESERVED_10      10

#define EH_RESERVED_11      11

#define EH_RESERVED_12      12

#define EH_RESERVED_13      13

#define EH_RESERVED_14      14

#define EH_EXTENDED         15

/* Initialize the protocol and registered fields */

static int proto_docsis;

static int hf_docsis_fctype;

static int hf_docsis_machdr_fcparm;

static int hf_docsis_fcparm;

static int hf_docsis_exthdr;

static int hf_docsis_concat_cnt;

static int hf_docsis_macparm;

static int hf_docsis_ehdrlen;

static int hf_docsis_len;

static int hf_docsis_eh_type;

static int hf_docsis_eh_len;

static int hf_docsis_eh_val;

static int hf_docsis_ehx_type;

static int hf_docsis_ehx_len;

static int hf_docsis_frag_rsvd;

static int hf_docsis_frag_first;

static int hf_docsis_frag_last;

static int hf_docsis_frag_seq;

static int hf_docsis_sid;

static int hf_docsis_mini_slots;

static int hf_docsis_requested_size;

static int hf_docsis_hcs;

static int hf_docsis_hcs_status;

static int hf_docsis_bpi_en;

static int hf_docsis_toggle_bit;

static int hf_docsis_key_seq;

static int hf_docsis_ehdr_ver;

static int hf_docsis_said;

static int hf_docsis_ehdr_phsi;

static int hf_docsis_ehdr_qind;

static int hf_docsis_ehdr_grants;

static int hf_docsis_reserved;

static int hf_docsis_ehdr_ds_traffic_pri;

static int hf_docsis_ehdr_ds_seq_chg_cnt;

static int hf_docsis_ehdr_ds_dsid;

static int hf_docsis_ehdr_ds_pkt_seq_num;

static int hf_docsis_ehdr_bpup2_bpi_en;

static int hf_docsis_ehdr_bpup2_toggle_bit;

static int hf_docsis_ehdr_bpup2_key_seq;

static int hf_docsis_ehdr_bpup2_ver;

static int hf_docsis_ehdr_bpup2_sid;

static int hf_docsis_ehdr_pv_st_refpt;

static int hf_docsis_ehdr_pv_timestamp;

static int hf_docsis_fragments;

static int hf_docsis_fragment;

static int hf_docsis_fragment_overlap;

static int hf_docsis_fragment_overlap_conflict;

static int hf_docsis_fragment_multiple_tails;

static int hf_docsis_fragment_too_long_fragment;

static int hf_docsis_fragment_error;

static int hf_docsis_fragment_count;

static int hf_docsis_reassembled_in;

static int hf_docsis_reassembled_length;

static int hf_docsis_reassembled_data;

static int hf_docsis_frag_fcs;

static int hf_docsis_frag_fcs_status;

static int hf_docsis_dst;

static int hf_docsis_dst_resolved;

static int hf_docsis_src;

static int hf_docsis_src_resolved;

static int hf_docsis_lg;

static int hf_docsis_ig;

static int hf_docsis_encrypted_payload;

static dissector_handle_t docsis_handle;

static dissector_handle_t eth_maybefcs_handle;

static dissector_handle_t docsis_mgmt_handle;

#if 0

static dissector_table_t docsis_dissector_table;

#endif

static expert_field ei_docsis_hcs_bad;

static expert_field ei_docsis_len;

static expert_field ei_docsis_len_small;

static expert_field ei_docsis_frag_fcs_bad;

static expert_field ei_docsis_eh_len;

/* Initialize the subtree pointers */

static int ett_docsis;

static int ett_ehdr;

static int ett_docsis_fragments;

static int ett_docsis_fragment;

static int ett_addr;

static const value_string fctype_vals[] = {

  {FCTYPE_PACKET,   "Packet PDU"},

  {FCTYPE_SPECIAL,  "Special Use"},

  {FCTYPE_ISOLAT,   "Isolation PDU"},

  {FCTYPE_MACSPC,   "MAC Specific"},

  {0, NULL}

};

static const value_string eh_type_vals[] = {

  {0,                 "NULL Configuration Parameter"},

  {EH_REQUEST,        "Request"},

  {EH_ACK_REQ,        "Acknowledgement Requested"},

  {EH_BP_UP,          "Upstream Privacy Element"},

  {EH_BP_DOWN,        "Downstream  Privacy Element"},

  {EH_SFLOW_HDR_UP,   "Service Flow EH; PHS Header Upstream"},

  {EH_SFLOW_HDR_DOWN, "Service Flow EH; PHS Header Downstream"},

  {EH_BP_UP2,         "Upstream Privacy with Multi Channel"},

  {EH_DS_SERVICE,     "Downstream Service"},

  {EH_PATH_VERIFY,    "Path Verify"},

  {EH_RESERVED_10,    "Reserved"},

  {EH_RESERVED_11,    "Reserved"},

  {EH_RESERVED_12,    "Reserved"},

  {EH_RESERVED_13,    "Reserved"},

  {EH_RESERVED_14,    "Reserved"},

  {EH_EXTENDED,       "Extended"},

  {0, NULL}

};

static const value_string ms_fcparm_vals[] = {

  {FCPARM_TIMING_HDR,           "Timing Header"},

  {FCPARM_MAC_MGMT_HDR,         "MAC Management Message"},

  {FCPARM_RQST_FRM,             "Request Frame"},

  {FCPARM_FRAG_HDR,             "Fragmentation Header"},

  {FCPARM_QUEUE_DEPTH_REQ_FRM,  "Queue Depth-based Request Frame"},

  {FCPARM_CONCAT_HDR,           "Concatenation Header"},

  {0, NULL}

};

static const value_string pkt_fcparm_vals[] = {

  {0x00,           "PDU MAC"},

  {0x01,           "DELAY/DUPLICATE/MULTICAST/BROADCAST"},

  {0, NULL}

};

static const true_false_string exthdr_tfs = {

  "Extended Header Present",

  "Extended Header Absent"

};

static const true_false_string qind_tfs = {

  "Rate overrun",

  "Rate non-overrun"

};

static const true_false_string odd_even_tfs = {

  "Odd Key",

  "Even Key",

};

static const value_string unique_no_phs[] = {

  { 0, "No PHS on current packet" },

  { 0, NULL }

};

/* Fragmentation Flags / Sequence */

static uint8_t frag_flags;

static uint8_t frag_seq;

static uint16_t frag_sid;

/*

 * Defragmentation of DOCSIS

 */

static reassembly_table docsis_reassembly_table;

static const fragment_items docsis_frag_items = {

  &ett_docsis_fragment,

  &ett_docsis_fragments,

  &hf_docsis_fragments,

  &hf_docsis_fragment,

  &hf_docsis_fragment_overlap,

  &hf_docsis_fragment_overlap_conflict,

  &hf_docsis_fragment_multiple_tails,

  &hf_docsis_fragment_too_long_fragment,

  &hf_docsis_fragment_error,

  &hf_docsis_fragment_count,

  &hf_docsis_reassembled_in,

  &hf_docsis_reassembled_length,

  &hf_docsis_reassembled_data,

  "DOCSIS fragments"

};

/* Dissection */

/* Code to Dissect the extended header; TLV Formatted headers */

static void

dissect_ehdr (tvbuff_t * tvb, proto_tree * tree, packet_info * pinfo, bool *is_encrypted)

{

  proto_tree *ehdr_tree;

  proto_item *eh_length_item;

  int ehdrlen;

  int pos;

  uint8_t type;

  uint8_t len;

  ehdrlen = tvb_get_uint8 (tvb, 1);

  pos = 4;

  ehdr_tree = proto_tree_add_subtree(tree, tvb, pos, ehdrlen, ett_ehdr, NULL, "Extended Header");

  while (pos < ehdrlen + 4)

  {

    type = (tvb_get_uint8 (tvb, pos) & 0xF0);

    len = (tvb_get_uint8 (tvb, pos) & 0x0F);

    if ((((type >> 4) & 0x0F)== 6) && (len == 2))

    {

      proto_tree_add_uint_format_value(ehdr_tree, hf_docsis_eh_type, tvb, pos, 1, 0x60, "Unsolicited Grant Sync EHDR Sub-Element");

    }

    else

    {

      proto_tree_add_item (ehdr_tree, hf_docsis_eh_type, tvb, pos, 1, ENC_BIG_ENDIAN);

    }

    eh_length_item = proto_tree_add_item (ehdr_tree, hf_docsis_eh_len, tvb, pos, 1, ENC_BIG_ENDIAN);

    pos++;

    switch ((type >> 4) & 0x0F)

    {

      case EH_REQUEST:

        /* Request: Minislots Requested */

        if (len == 3)

        {

          proto_tree_add_item(ehdr_tree, hf_docsis_mini_slots, tvb, pos, 1, ENC_NA);

          proto_tree_add_item(ehdr_tree, hf_docsis_sid, tvb, pos + 1, 2, ENC_BIG_ENDIAN);

        }

        else

        {

          expert_add_info(pinfo, eh_length_item, &ei_docsis_eh_len);

          return;

        }

        break;

      case EH_ACK_REQ:

        /* Deprecated in DOCSIS 3.1 */

        if (len == 2)

        {

          proto_tree_add_item(ehdr_tree, hf_docsis_sid, tvb, pos, 2, ENC_BIG_ENDIAN);

        }

        else

        {

          expert_add_info(pinfo, eh_length_item, &ei_docsis_eh_len);

          return;

        }

        break;

      case EH_BP_UP:

        /* Upstream Privacy EH Element or Upstream Privacy with fragmentation */

        proto_tree_add_item (ehdr_tree, hf_docsis_key_seq, tvb, pos, 1,

                             ENC_BIG_ENDIAN);

        proto_tree_add_item (ehdr_tree, hf_docsis_ehdr_ver, tvb, pos, 1,

                             ENC_BIG_ENDIAN);

        proto_tree_add_item_ret_boolean (ehdr_tree, hf_docsis_bpi_en, tvb, pos + 1, 1,

                             ENC_BIG_ENDIAN, is_encrypted);

        proto_tree_add_item (ehdr_tree, hf_docsis_toggle_bit, tvb, pos + 1,

                             1, ENC_BIG_ENDIAN);

        proto_tree_add_item (ehdr_tree, hf_docsis_sid, tvb, pos + 1, 2,

                             ENC_BIG_ENDIAN);

        frag_sid = tvb_get_uint8 (tvb, pos+1) & 0xCFFF;

        proto_tree_add_item (ehdr_tree, hf_docsis_mini_slots, tvb, pos + 3,

                             1, ENC_BIG_ENDIAN);

        if (pinfo->fragmented)

        {

          proto_tree_add_item (ehdr_tree, hf_docsis_frag_rsvd, tvb, pos+4,

                               1, ENC_BIG_ENDIAN);

          frag_flags = tvb_get_uint8 (tvb, pos+4) & 0x30;

          proto_tree_add_item (ehdr_tree, hf_docsis_frag_first, tvb, pos+4,

                               1, ENC_BIG_ENDIAN);

          proto_tree_add_item (ehdr_tree, hf_docsis_frag_last, tvb, pos+4,

                               1, ENC_BIG_ENDIAN);

          frag_seq = tvb_get_uint8 (tvb, pos+4) & 0x0F;

          proto_tree_add_item (ehdr_tree, hf_docsis_frag_seq, tvb, pos+4,

                               1, ENC_BIG_ENDIAN);

        }

        break;

      case EH_BP_DOWN:

        /* Downstream Privacy EH Element */

        proto_tree_add_item (ehdr_tree, hf_docsis_key_seq, tvb, pos, 1,

                             ENC_BIG_ENDIAN);

        proto_tree_add_item (ehdr_tree, hf_docsis_ehdr_ver, tvb, pos, 1,

                             ENC_BIG_ENDIAN);

        proto_tree_add_item_ret_boolean (ehdr_tree, hf_docsis_bpi_en, tvb, pos + 1, 1,

                             ENC_BIG_ENDIAN, is_encrypted);

        proto_tree_add_item (ehdr_tree, hf_docsis_toggle_bit, tvb, pos + 1,

                             1, ENC_BIG_ENDIAN);

        proto_tree_add_item (ehdr_tree, hf_docsis_said, tvb, pos + 1, 2,

                             ENC_BIG_ENDIAN);

        proto_tree_add_item (ehdr_tree, hf_docsis_reserved, tvb, pos + 3, 1,

                             ENC_BIG_ENDIAN);

        break;

      case EH_SFLOW_HDR_DOWN:

        /* Deprecated in DOCSIS 3.1, was Downstream Service Flow EH Element in earlier revisions */

      case EH_SFLOW_HDR_UP:

        /* Deprecated in DOCSIS 3.1, was Upstream Service Flow EH Element in earlier revisions */

        proto_tree_add_item(ehdr_tree, hf_docsis_ehdr_phsi, tvb, pos, 1, ENC_BIG_ENDIAN);

        if (len == 2)

        {

          proto_tree_add_item (ehdr_tree, hf_docsis_ehdr_qind, tvb, pos+1, 1, ENC_BIG_ENDIAN);

          proto_tree_add_item (ehdr_tree, hf_docsis_ehdr_grants, tvb, pos+1, 1, ENC_BIG_ENDIAN);

        }

        break;

      case EH_BP_UP2:

        /* Upstream Privacy EH Element, version 2, with no piggyback request */

        proto_tree_add_item (ehdr_tree, hf_docsis_ehdr_bpup2_key_seq, tvb, pos, 1,

                             ENC_BIG_ENDIAN);

        proto_tree_add_item (ehdr_tree, hf_docsis_ehdr_bpup2_ver, tvb, pos, 1,

                             ENC_BIG_ENDIAN);

        proto_tree_add_item_ret_boolean (ehdr_tree, hf_docsis_ehdr_bpup2_bpi_en, tvb, pos + 1, 1,

                             ENC_BIG_ENDIAN, is_encrypted);

        proto_tree_add_item (ehdr_tree, hf_docsis_ehdr_bpup2_toggle_bit, tvb, pos + 1,

                             1, ENC_BIG_ENDIAN);

        proto_tree_add_item (ehdr_tree, hf_docsis_ehdr_bpup2_sid, tvb, pos + 1, 2,

                             ENC_BIG_ENDIAN);

        break;

      case EH_DS_SERVICE:

        /* Downstream Service EH Element */

        proto_tree_add_item(ehdr_tree, hf_docsis_ehdr_ds_traffic_pri, tvb, pos, 1, ENC_BIG_ENDIAN);

        if (len == 3)

        {

          proto_tree_add_item (ehdr_tree, hf_docsis_ehdr_ds_dsid, tvb, pos, 3, ENC_BIG_ENDIAN);

        }

        if (len == 5)

        {

          proto_tree_add_item (ehdr_tree, hf_docsis_ehdr_ds_seq_chg_cnt, tvb, pos, 1, ENC_BIG_ENDIAN);

          proto_tree_add_item (ehdr_tree, hf_docsis_ehdr_ds_dsid, tvb, pos, 3, ENC_BIG_ENDIAN);

          proto_tree_add_item (ehdr_tree, hf_docsis_ehdr_ds_pkt_seq_num, tvb, pos+3, 2, ENC_BIG_ENDIAN);

        }

        break;

      case EH_PATH_VERIFY:

        /* Path Verify EH Element */

        if (len == 5)

        {

          proto_tree_add_item (ehdr_tree, hf_docsis_ehdr_pv_st_refpt, tvb, pos, 1, ENC_BIG_ENDIAN);

          proto_tree_add_item (ehdr_tree, hf_docsis_ehdr_pv_timestamp, tvb, pos+1, 4, ENC_BIG_ENDIAN);

        }

        break;

      case EH_EXTENDED:

        /* Extended EH Element, ignore eh_len */

        proto_tree_add_item(ehdr_tree, hf_docsis_ehx_type, tvb, pos, 1, ENC_NA);

        pos++;

        proto_tree_add_item_ret_uint8(ehdr_tree, hf_docsis_ehx_len, tvb, pos, 1, ENC_NA, &len);

        pos++;

        /* FALLTHROUGH */

      default:

        if (len > 0)

          proto_tree_add_item (ehdr_tree, hf_docsis_eh_val, tvb, pos,

                               len, ENC_NA);

    }

    pos += len;

  }

  return;

}

/* Code to Dissect the Header Check Sequence field */

/* Return false in case FCS validation is enabled, but FCS is incorrect */

/* Return true in all other cases */

static bool

dissect_hcs_field (tvbuff_t * tvb, packet_info * pinfo, proto_tree * docsis_tree, int hdrlen)

{

  /* dissect the header check sequence */

  if(docsis_check_fcs){

    /* CRC-CCITT(16+12+5+1) */

    uint16_t fcs = g_ntohs(crc16_ccitt_tvb(tvb, (hdrlen - 2)));

    proto_tree_add_checksum(docsis_tree, tvb, (hdrlen - 2), hf_docsis_hcs, hf_docsis_hcs_status, &ei_docsis_hcs_bad, pinfo, fcs, ENC_BIG_ENDIAN, PROTO_CHECKSUM_VERIFY);

    return (tvb_get_ntohs(tvb, (hdrlen - 2)) == fcs) ? true : false;

  }

  else

  {

    proto_tree_add_checksum(docsis_tree, tvb, (hdrlen - 2), hf_docsis_hcs, hf_docsis_hcs_status, &ei_docsis_hcs_bad, pinfo, 0, ENC_BIG_ENDIAN, PROTO_CHECKSUM_NO_FLAGS);

  }

  return true;

}

/* Code to Dissect the extended header length / MAC Param field and Length field */

/* The length field may contain a SID, but this logic is not handled here */

static proto_item*

dissect_exthdr_length_field (tvbuff_t * tvb, packet_info * pinfo, proto_tree * docsis_tree,

                             uint8_t exthdr, uint16_t mac_parm, uint16_t len_sid, uint16_t *payload_length, bool *is_encrypted)

{

  proto_item *length_item;

  if (exthdr == EXT_HDR_ON)

  {

    /* Add in Extended Header Length */

    proto_tree_add_item (docsis_tree, hf_docsis_ehdrlen, tvb, 1, 1,  ENC_BIG_ENDIAN);

    length_item = proto_tree_add_item (docsis_tree, hf_docsis_len, tvb, 2, 2, ENC_BIG_ENDIAN);

    /* Validate PDU length */

    if ((len_sid - mac_parm) > *payload_length)

    {

      *payload_length = len_sid;

      expert_add_info(pinfo, length_item, &ei_docsis_len);

    }

    /* Pass off to the Extended Header dissection */

    dissect_ehdr (tvb, docsis_tree, pinfo, is_encrypted);

  }

  else

  {

    /* Add in MAC Parm field only */

    proto_tree_add_item (docsis_tree, hf_docsis_macparm, tvb, 1, 1, ENC_BIG_ENDIAN);

    length_item = proto_tree_add_item (docsis_tree, hf_docsis_len, tvb, 2, 2, ENC_BIG_ENDIAN);

    /* Validate PDU length */

    if (len_sid > *payload_length)

    {

      *payload_length = len_sid;

      expert_add_info(pinfo, length_item, &ei_docsis_len);

    }

  }

  return length_item;

}

/* Code to Dissect Encrypted DOCSIS Frames */

/* Print DST and SRC MACs and do not dissect the payload */

/* Implementation inferred from packet-eth.c */

static void

dissect_encrypted_frame (tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree, const uint8_t fctype, const uint8_t fcparm)

{

  uint32_t          offset, frame_len;

  const uint8_t     *src_addr, *dst_addr;

  const char        *src_addr_name, *dst_addr_name;

  proto_item        *addr_item;

  proto_tree        *addr_tree=NULL;

//  tvbuff_t          *next_tvb;

  /* According to CM-SP-SEC-v3.1, PDU regions of the following

   * frames must be encrypted when security is enabled:

   * - Variable-length PDU MAC Frames;

   * - Fragmentation MAC Frames;

   * - Registration Request (REG-REQ-MP) MAC Management Message Frames;

   * - Isolation PDU MAC Frames.

   * There are also other corner cases when MAC Management frames might be encrypted

   * (e.g. EH_TYPE=7 as described in CM-SP-MULPIv3.1-I15-180509 Table 17 and Table 20)

   */

  if (fctype == FCTYPE_MACSPC) {

    if (fcparm == FCPARM_MAC_MGMT_HDR) {

      col_append_str (pinfo->cinfo, COL_INFO, " (Encrypted MMM)");

    } else if (fcparm == FCPARM_FRAG_HDR) {

      col_append_str (pinfo->cinfo, COL_INFO, " (Encrypted Fragmentation MAC Frame)");

    } else {

      col_append_str (pinfo->cinfo, COL_INFO, " (Encrypted)");

    }

  } else {

    col_append_str (pinfo->cinfo, COL_INFO, " (Encrypted)");

  }

  offset = 0;

  frame_len = tvb_captured_length_remaining (tvb, offset);

  switch (fctype)

  {

    case FCTYPE_PACKET:

    case FCTYPE_ISOLAT:

    case FCTYPE_MACSPC:

      dst_addr = tvb_get_ptr(tvb, 0, 6);

      dst_addr_name = get_ether_name(dst_addr);

      src_addr = tvb_get_ptr(tvb, 6, 6);

      src_addr_name = get_ether_name(src_addr);

      addr_item = proto_tree_add_ether(tree, hf_docsis_dst, tvb, 0, 6, dst_addr);

      addr_tree = proto_item_add_subtree(addr_item, ett_addr);

      addr_item=proto_tree_add_string(addr_tree, hf_docsis_dst_resolved, tvb, 0, 6,

          dst_addr_name);

      proto_item_set_generated(addr_item);

      proto_tree_add_item(addr_tree, hf_docsis_lg, tvb, 0, 3, ENC_BIG_ENDIAN);

      proto_tree_add_item(addr_tree, hf_docsis_ig, tvb, 0, 3, ENC_BIG_ENDIAN);

      addr_item = proto_tree_add_ether(tree, hf_docsis_src, tvb, 6, 6, src_addr);

      addr_tree = proto_item_add_subtree(addr_item, ett_addr);

      addr_item=proto_tree_add_string(addr_tree, hf_docsis_src_resolved, tvb, 6, 6,

          src_addr_name);

      proto_item_set_generated(addr_item);

      proto_tree_add_item(addr_tree, hf_docsis_lg, tvb, 6, 3, ENC_BIG_ENDIAN);

      proto_tree_add_item(addr_tree, hf_docsis_ig, tvb, 6, 3, ENC_BIG_ENDIAN);

      offset += 12;

      break;

  }

  proto_tree_add_item(tree, hf_docsis_encrypted_payload, tvb, offset, frame_len - offset, ENC_NA);

  return;

}

/* Main DOCSIS Dissection Entry Point */

/* Code to Dissect the DOCSIS Frames */

static int

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

{

  uint8_t fc = 0;

  uint8_t fctype = 0;

  uint8_t fcparm = 0;

  uint8_t exthdr = 0;

  uint16_t mac_parm = 0;

  uint8_t hdrlen = DOCSIS_MIN_HEADER_LEN;

  uint16_t len_sid = 0;

  tvbuff_t *next_tvb = NULL;

  tvbuff_t *mgt_tvb = NULL;

  int pdulen = 0;

  uint16_t payload_length = 0;

  /* uint16_t framelen = 0; */

  bool save_fragmented;

  bool is_encrypted = false;

  bool fcs_correct;

  proto_item *ti;

  proto_tree *docsis_tree;

  /* Extract Frame Control parts */

  fc = tvb_get_uint8 (tvb, 0); /* Frame Control Byte */

  fctype = (fc >> 6) & 0x03;    /* Frame Control Type:  2 MSB Bits */

  fcparm = (fc >> 1) & 0x1F;    /* Frame Control Parameter: Next 5 Bits */

  exthdr = (fc & 0x01);         /* Extended Header Bit: LSB */

  /* Extract the MAC Parm; MAC Parm and SID offsets; change for a Queue Depth Request */

  if (fcparm == FCPARM_QUEUE_DEPTH_REQ_FRM) {

    mac_parm = tvb_get_ntohs (tvb, 1);

    len_sid = tvb_get_ntohs (tvb, 3);

    hdrlen = DOCSIS_MIN_HEADER_LEN + 1; // 7-byte header for this message type

  } else {

    mac_parm = tvb_get_uint8 (tvb, 1);

    len_sid = tvb_get_ntohs (tvb, 2);

  }

  /* Set Header Length based on presence of Extended header */

  if (exthdr == EXT_HDR_ON) {

    hdrlen += mac_parm;

  }

  /* Captured Payload Length is based on the length of the header */

  payload_length = tvb_reported_length_remaining (tvb, hdrlen);

  /* If this is a Request Frame, then pdulen is 0 and framelen is 6 */

  if ((fctype == FCTYPE_MACSPC) && (fcparm == FCPARM_RQST_FRM || fcparm == FCPARM_QUEUE_DEPTH_REQ_FRM))

  {

    pdulen = 0;

    /*

    if (fcparm == FCPARM_QUEUE_DEPTH_REQ_FRM)

      framelen = DOCSIS_MIN_HEADER_LEN + 1;

    else

      framelen = DOCSIS_MIN_HEADER_LEN;

    */

  } else {

    /* framelen = DOCSIS_MIN_HEADER_LEN + len_sid; */

    pdulen = len_sid - (mac_parm + 2);

  }

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

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

  switch (fctype)

  {

    case FCTYPE_PACKET:

      col_set_str (pinfo->cinfo, COL_INFO, "Packet PDU");

      break;

    case FCTYPE_SPECIAL:

      col_set_str (pinfo->cinfo, COL_INFO, "Special Use");

      break;

    case FCTYPE_ISOLAT:

      col_set_str (pinfo->cinfo, COL_INFO, "Isolation PDU");

      break;

    case FCTYPE_MACSPC:

      if (fcparm == FCPARM_RQST_FRM)

        col_add_fstr (pinfo->cinfo, COL_INFO,

                      "Request Frame SID=%u Mini Slots=%u", len_sid,

                      mac_parm);

      else if (fcparm == FCPARM_QUEUE_DEPTH_REQ_FRM)

        col_add_fstr (pinfo->cinfo, COL_INFO,

                      "Request Frame SID=%u, Requested Size=%uxN bytes", len_sid,

                      mac_parm);

      else if (fcparm == FCPARM_FRAG_HDR)

        col_set_str (pinfo->cinfo, COL_INFO, "Fragmented Frame");

      else

        col_set_str (pinfo->cinfo, COL_INFO, "MAC Specific");

      break;

  }  /* switch fctype */

  ti = proto_tree_add_item(tree, proto_docsis, tvb, 0, hdrlen, ENC_NA);

  docsis_tree = proto_item_add_subtree (ti, ett_docsis);

  /* add an item to the subtree, see section 1.6 for more information */

  /* Add in FC Byte fields */

  proto_tree_add_item (docsis_tree, hf_docsis_fctype, tvb, 0, 1, ENC_BIG_ENDIAN);

  switch (fctype)

  {

    case FCTYPE_PACKET:

    {

      proto_item_append_text (ti, " Packet PDU");

      proto_tree_add_item (docsis_tree, hf_docsis_fcparm, tvb, 0, 1, ENC_BIG_ENDIAN);

      proto_tree_add_item (docsis_tree, hf_docsis_exthdr, tvb, 0, 1, ENC_BIG_ENDIAN);

      /* Dissect Length field for a PDU */

      dissect_exthdr_length_field (tvb, pinfo, docsis_tree, exthdr, mac_parm, len_sid, &payload_length, &is_encrypted);

      /* Dissect Header Check Sequence field for a PDU */

      fcs_correct = dissect_hcs_field (tvb, pinfo, docsis_tree, hdrlen);

      if (fcs_correct && pdulen > 0)

      {

        next_tvb =  tvb_new_subset_remaining(tvb, hdrlen);

        if(is_encrypted && !docsis_dissect_encrypted_frames)

          dissect_encrypted_frame (next_tvb, pinfo, docsis_tree, fctype, fcparm);

        else

          call_dissector (eth_maybefcs_handle, next_tvb, pinfo, docsis_tree);

      }

      break;

    }

    case FCTYPE_SPECIAL:

    {

      proto_item_append_text (ti, " Special Use PDU");

      proto_tree_add_item (docsis_tree, hf_docsis_machdr_fcparm, tvb, 0, 1, ENC_BIG_ENDIAN);

      proto_tree_add_item (docsis_tree, hf_docsis_exthdr, tvb, 0, 1, ENC_BIG_ENDIAN);

      /* Dissect Length field for a PDU */

      dissect_exthdr_length_field (tvb, pinfo, docsis_tree, exthdr, mac_parm, len_sid, &payload_length, &is_encrypted);

      /* Dissect Header Check Sequence field for a PDU */

      fcs_correct = dissect_hcs_field (tvb, pinfo, docsis_tree, hdrlen);

      if (fcs_correct) {

        if (fcparm == FCPARM_MAC_MGMT_HDR && exthdr == EXT_HDR_OFF) {

          /* Pass off to the DOCSIS Management dissector/s */

          mgt_tvb = tvb_new_subset_remaining(tvb, hdrlen);

          if (is_encrypted && !docsis_dissect_encrypted_frames)

            dissect_encrypted_frame (mgt_tvb, pinfo, docsis_tree, fctype, fcparm);

          else

            call_dissector (docsis_mgmt_handle, mgt_tvb, pinfo, docsis_tree);

        } else {

          /* Don't do anything for a Reserved Frame */

          next_tvb =  tvb_new_subset_remaining(tvb, hdrlen);

          call_data_dissector(next_tvb, pinfo, tree);

        }

      }

      break;

    }

    case FCTYPE_ISOLAT:

    {

      proto_item_append_text (ti, " Isolation PDU");

      proto_tree_add_item (docsis_tree, hf_docsis_fcparm, tvb, 0, 1, ENC_BIG_ENDIAN);

      proto_tree_add_item (docsis_tree, hf_docsis_exthdr, tvb, 0, 1, ENC_BIG_ENDIAN);

      /* Dissect Length field for a PDU */

      dissect_exthdr_length_field (tvb, pinfo, docsis_tree, exthdr, mac_parm, len_sid, &payload_length, &is_encrypted);

      /* Dissect Header Check Sequence field for a PDU */

      fcs_correct = dissect_hcs_field (tvb, pinfo, docsis_tree, hdrlen);

      if (fcs_correct && pdulen > 0)

      {

        next_tvb =  tvb_new_subset_remaining(tvb, hdrlen);

        if(is_encrypted && !docsis_dissect_encrypted_frames)

          dissect_encrypted_frame (next_tvb, pinfo, docsis_tree, fctype, fcparm);

        else

          call_dissector (eth_maybefcs_handle, next_tvb, pinfo, docsis_tree);

      }

      break;

    }

    case FCTYPE_MACSPC:

    {

      proto_item_append_text (ti, " MAC-Specific PDU");

      proto_tree_add_item (docsis_tree, hf_docsis_machdr_fcparm, tvb, 0, 1, ENC_BIG_ENDIAN);

      proto_tree_add_item (docsis_tree, hf_docsis_exthdr, tvb, 0, 1, ENC_BIG_ENDIAN);

      switch(fcparm)

      {

        case FCPARM_TIMING_HDR:

          // no break

        case FCPARM_MAC_MGMT_HDR:

        {

          /* Dissect Length field for a PDU */

          dissect_exthdr_length_field (tvb, pinfo, docsis_tree, exthdr, mac_parm, len_sid, &payload_length, &is_encrypted);

          /* Dissect Header Check Sequence field for a PDU */

          fcs_correct = dissect_hcs_field (tvb, pinfo, docsis_tree, hdrlen);

          if (fcs_correct)

          {

            /* Pass off to the DOCSIS Management dissector/s */

            mgt_tvb = tvb_new_subset_remaining(tvb, hdrlen);

            if(is_encrypted && !docsis_dissect_encrypted_frames)

              dissect_encrypted_frame (mgt_tvb, pinfo, docsis_tree, fctype, fcparm);

            else

              call_dissector (docsis_mgmt_handle, mgt_tvb, pinfo, docsis_tree);

          }

          break;

        }

        case FCPARM_RQST_FRM:

        {

          /* Decode for a Request Frame.  No extended header */

          proto_tree_add_uint (docsis_tree, hf_docsis_mini_slots, tvb, 1, 1, mac_parm);

          proto_tree_add_uint (docsis_tree, hf_docsis_sid, tvb, 2, 2, len_sid);

          /* Dissect Header Check Sequence field for a PDU */

          fcs_correct = dissect_hcs_field (tvb, pinfo, docsis_tree, hdrlen);

          if (fcs_correct)

          {

            /* Don't do anything for a Request Frame, there is no data following it */

          }

          break;

        }

        case FCPARM_FRAG_HDR:

        {

          proto_item *length_item;

          /* Check if this is a fragmentation header */

          save_fragmented = pinfo->fragmented;

          pinfo->fragmented = true;

          /* Dissect Length field for a PDU */

          length_item = dissect_exthdr_length_field (tvb, pinfo, docsis_tree, exthdr, mac_parm, len_sid, &payload_length, &is_encrypted);

          if (len_sid < 4) {

            expert_add_info_format(pinfo, length_item, &ei_docsis_len_small, "Len field value is too small to fit fragment FCS");

            THROW(ReportedBoundsError);

          }

          /* Dissect Header Check Sequence field for a PDU */

          fcs_correct = dissect_hcs_field (tvb, pinfo, docsis_tree, hdrlen);

          if (fcs_correct)

          {

            uint32_t fcs = 0;

            if (!tvb_bytes_exist(tvb, hdrlen, len_sid)) {

              fcs_correct = false;

            } else {

              /* Grab the Fragment FCS */

              uint32_t sent_fcs = tvb_get_ntohl(tvb, (hdrlen + len_sid - 4));

              fcs = crc32_802_tvb(tvb, hdrlen + len_sid - 4);

              fcs_correct = (sent_fcs == fcs);

            }

            /* Only defragment valid frames with a good FCS */

            if (fcs_correct)

            {

              fragment_head *frag_msg = NULL;

              frag_msg = fragment_add_seq_check(&docsis_reassembly_table,

                                                tvb, hdrlen, pinfo,

                                                frag_sid, NULL, /* ID for fragments belonging together */

                                                frag_seq, /* Fragment Sequence Number */

                                                (len_sid - 4), /* fragment length - to the end */

                                                !(frag_flags & FRAG_LAST)); /* More fragments? */

              next_tvb = process_reassembled_data(tvb, hdrlen, pinfo,

                                                  "Reassembled Message", frag_msg, &docsis_frag_items,

                                                  NULL, docsis_tree);

              if (frag_flags == FRAG_LAST)

                pinfo->fragmented = false;

              else

                pinfo->fragmented = true;

              if (frag_msg) { /* Reassembled */

                proto_item_append_text (ti, " (Message Reassembled)");

              } else { /* Not last packet of reassembled Short Message */

                proto_item_append_text (ti, " (Message fragment %u)", frag_seq);

              }

              if(next_tvb)

              {

                /* By default assume an Ethernet payload */

                if(is_encrypted && !docsis_dissect_encrypted_frames)

                  dissect_encrypted_frame (next_tvb, pinfo, docsis_tree, fctype, fcparm);

                else

                  call_dissector (eth_maybefcs_handle, next_tvb, pinfo, docsis_tree);

              } else {

                /* Otherwise treat as Data */

                tvbuff_t *payload_tvb = tvb_new_subset_length(tvb, hdrlen, len_sid - 4);

                call_data_dissector(payload_tvb, pinfo, docsis_tree);

              }

            }

            /* Add the Fragment FCS to the end of the parent tree */

            proto_tree_add_checksum(docsis_tree, tvb, (hdrlen + len_sid - 4), hf_docsis_frag_fcs, hf_docsis_frag_fcs_status, &ei_docsis_frag_fcs_bad, pinfo, fcs, ENC_BIG_ENDIAN, PROTO_CHECKSUM_VERIFY);

            pinfo->fragmented = save_fragmented;

          }

          break;

        }

        case FCPARM_QUEUE_DEPTH_REQ_FRM:

        {

          /* Decode for a Queue-depth Based Request */

          proto_tree_add_uint (docsis_tree, hf_docsis_requested_size, tvb, 1, 2, mac_parm);

          proto_tree_add_uint (docsis_tree, hf_docsis_sid, tvb, 3, 2, len_sid);

          /* Dissect Header Check Sequence field for a PDU */

          fcs_correct = dissect_hcs_field (tvb, pinfo, docsis_tree, hdrlen);

          if (fcs_correct)

          {

          /* No PDU Payload for this frame */

          }

          break;

        }

        case FCPARM_CONCAT_HDR:

        {

          /* Decode for a Concatenated Header; ONLY for DOCSIS versions < 3.1.  No Extended Header */

          proto_item_append_text (ti, " (Concatenated Header)");

          proto_tree_add_item (docsis_tree, hf_docsis_concat_cnt, tvb, 1, 1, ENC_BIG_ENDIAN);

          proto_tree_add_item (docsis_tree, hf_docsis_len, tvb, 2, 2, ENC_BIG_ENDIAN);

          /* Dissect Header Check Sequence field for a PDU */

          fcs_correct = dissect_hcs_field (tvb, pinfo, docsis_tree, hdrlen);

          if (fcs_correct)

          {

            // There used to be a section of code here that recursively

            // called dissect_docsis. It has been removed. If you plan on

            // adding concatenated PDU support back you should consider

            // doing something like the following:

            // dissect_docsis(...) {

            //   while(we_have_pdus_remaining) {

            //     int pdu_len = dissect_docsis_pdu(...)

            //     if (pdu_len < 1) {

            //       add_expert...

            //       break;

            //     }

            //   }

            // }

            // Adding back this functionality using recursion might result

            // in this dissector being disabled by default or removed entirely.

          }

          break;

        }

        default:

            /* Unknown parameter, stop dissection */

          break;

      } /* switch fcparm */

      break;

    }

  } /* switch fctype */

  return tvb_captured_length(tvb);

}

/* Register the protocol with Wireshark */

void

proto_register_docsis (void)

{

  static hf_register_info hf[] = {

    {&hf_docsis_fctype,

     {"FCType", "docsis.fctype",

      FT_UINT8, BASE_HEX, VALS (fctype_vals), 0xC0,

      "Frame Control Type", HFILL}

    },

    {&hf_docsis_fcparm,

     {"FCParm", "docsis.fcparm",

      FT_UINT8, BASE_DEC, VALS (pkt_fcparm_vals), 0x3E,

      "Parameter Field", HFILL}

    },

    {&hf_docsis_machdr_fcparm,

     {"FCParm", "docsis.fcparm",

      FT_UINT8, BASE_DEC, VALS (ms_fcparm_vals), 0x3E,

      "Parameter Field", HFILL}

    },

    {&hf_docsis_exthdr,

     {"EXTHDR", "docsis.exthdr",

      FT_BOOLEAN, 8, TFS (&exthdr_tfs), 0x01,

      "Extended Header Presence", HFILL}

    },

    {&hf_docsis_macparm,

     {"MACParm", "docsis.macparm",

      FT_UINT8, BASE_HEX, NULL, 0x0,

      "MAC Parameter Field", HFILL}

    },

    {&hf_docsis_concat_cnt,

     {"Number of Concatenated Frames", "docsis.concat_cnt",

      FT_UINT8, BASE_DEC, NULL, 0x0,

      NULL, HFILL}

    },

    {&hf_docsis_ehdrlen,

     {"Extended Header Length (bytes)", "docsis.ehdrlen",

      FT_UINT8, BASE_DEC, NULL, 0x0,

      NULL, HFILL}

    },

    {&hf_docsis_len,

     {"Length of the MAC frame (bytes)", "docsis.len",

      FT_UINT16, BASE_DEC, NULL, 0x0,

      "Length of the MAC frame, not counting the fixed-length MAC header", HFILL}

    },

    {&hf_docsis_eh_type,

     {"Type", "docsis.ehdr.type",

      FT_UINT8, BASE_DEC, VALS (eh_type_vals), 0xF0,

      "TLV Type", HFILL}

    },

    {&hf_docsis_eh_len,

     {"Length", "docsis.ehdr.len",

      FT_UINT8, BASE_DEC, NULL, 0x0F,

      "TLV Len", HFILL}

    },

    {&hf_docsis_eh_val,

     {"Value", "docsis.ehdr.value",

      FT_BYTES, BASE_NONE, NULL, 0x0,

      "TLV Value", HFILL}

    },

    {&hf_docsis_ehx_type,

     {"Extended Type", "docsis.ehdr.ehx_type",

      FT_UINT8, BASE_DEC, NULL, 0x0,

      "TLV Type", HFILL}

    },

    {&hf_docsis_ehx_len,

     {"Extended Length", "docsis.ehdr.ehx_len",

      FT_UINT8, BASE_DEC, NULL, 0x0,

      "TLV Len", HFILL}

    },

    {&hf_docsis_frag_rsvd,

     {"Reserved", "docsis.frag_rsvd",

      FT_UINT8, BASE_DEC, NULL, 0xC0,

      NULL, HFILL}

    },

    {&hf_docsis_frag_first,

     {"First Frame", "docsis.frag_first",

      FT_BOOLEAN, 8, NULL, 0x20,

      NULL, HFILL}

    },

    {&hf_docsis_frag_last,

     {"Last Frame", "docsis.frag_last",

      FT_BOOLEAN, 8, NULL, 0x10,

      NULL, HFILL}

    },

    {&hf_docsis_frag_seq,

     {"Fragmentation Sequence #", "docsis.frag_seq",

      FT_UINT8, BASE_DEC, NULL, 0x0F,

      "Fragmentation Sequence Number", HFILL}

    },

    {&hf_docsis_sid,

     {"SID", "docsis.ehdr.sid",

      FT_UINT16, BASE_DEC_HEX, NULL, 0x3FFF,

      "Service Identifier", HFILL}

    },

    {&hf_docsis_said,

     {"SAID", "docsis.ehdr.said",

      FT_UINT16, BASE_DEC, NULL, 0x3FFF,