/* packet-pw-cesopsn.c

 * Routines for CESoPSN PW dissection as per RFC5086.

 * Copyright 2009, Dmitry Trebich, Artem Tamazov <artem.tamazov@tellabs.com>

 *

 * Wireshark - Network traffic analyzer

 * By Gerald Combs <gerald@wireshark.org>

 * Copyright 1998 Gerald Combs

 *

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

 *

 * History:

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

 * 16.03.2009 initial implementation for MPLS

 * 14.08.2009 added: support for IP/UDP demultiplexing

 * Not supported yet:

 * - All PW modes, except Basic NxDS0 mode.

 * - <Optional> RTP Headers (RFC3550)

 * - Decoding of PW payload

 */

#include "config.h"

#include <epan/packet.h>

#include <epan/expert.h>

#include "packet-mpls.h"

#include "packet-pw-common.h"

void proto_register_pw_cesopsn(void);

void proto_reg_handoff_pw_cesopsn(void);

static int proto = -1;

static int ett_pw_cesopsn;

static int hf_cw;

static int hf_cw_bits03;

static int hf_cw_lm;

static int hf_cw_r;

static int hf_cw_frg;

static int hf_cw_len;

static int hf_cw_seq;

static int hf_payload;

static int hf_payload_l;

static expert_field ei_payload_size_invalid_undecoded;

static expert_field ei_cw_frg;

static expert_field ei_payload_size_invalid_error;

static expert_field ei_cw_bits03;

static expert_field ei_pref_cw_len;

static expert_field ei_cw_lm;

static expert_field ei_packet_size_too_small;

static dissector_handle_t pw_padding_handle;

static dissector_handle_t pw_cesopsn_udp_handle;

static dissector_handle_t pw_cesopsn_mpls_handle;

static const value_string vals_cw_lm[] = {

  /* note that bitmask in hs_register_info is 0xb == 1011B */

  /* this is why 0x8 comes just after 0x3 */

  { 0x0,  "Normal situation - no AC faults" },

  /*{ 0x1,  "Reserved combination" },*/

  { 0x2,  "AC Fault - RDI condition" },

  { 0x3,  "Reserved for CESoPSN signaling" },

  { 0x8,  "AC Fault - TDM data is invalid" },

  /*{ 0x9,  "Reserved combination" },*/

  /*{ 0xa,  "Reserved combination" },*/

  /*{ 0xb,  "Reserved combination" },*/

  { 0,  NULL }

};

static

void dissect_pw_cesopsn( tvbuff_t * tvb_original

            ,packet_info * pinfo

            ,proto_tree * tree

            ,pwc_demux_type_t demux)

{

  const int encaps_size = 4; /*RTP header in encapsulation is not supported yet*/

  int       packet_size;

  int       payload_size;

  int       padding_size;

  int properties;

  packet_size = tvb_reported_length_remaining(tvb_original, 0);

  /*

   * FIXME

   * "4" below should be replaced by something like "min_packet_size_this_dissector"

   * Also call to dissect_try_cw_first_nibble() should be moved before this block

   */

  if (packet_size < 4) /* 4 is smallest size which may be sensible (for PWACH dissector) */

  {

    proto_item  *item;

    item = proto_tree_add_item(tree, proto, tvb_original, 0, -1, ENC_NA);

    expert_add_info_format(pinfo, item, &ei_packet_size_too_small,

               "PW packet size (%d) is too small to carry sensible information"

               ,(int)packet_size);

    col_set_str(pinfo->cinfo, COL_PROTOCOL, "CESoPSN basic (no RTP)");

    col_set_str(pinfo->cinfo, COL_INFO, "Malformed: PW packet is too small");

    return;

  }

  switch (demux)

  {

  case PWC_DEMUX_MPLS:

    if (dissect_try_cw_first_nibble(tvb_original, pinfo, tree))

    {

      return;

    }

    break;

  case PWC_DEMUX_UDP:

    break;

  default:

    DISSECTOR_ASSERT_NOT_REACHED();

    return;

  }

  /* check how "good" is this packet */

  /* also decide payload length from packet size and CW */

  properties = PWC_PACKET_PROPERTIES_T_INITIALIZER;

  if (0 != (tvb_get_uint8(tvb_original, 0) & 0xf0 /*bits03*/))

  {

    properties |= PWC_CW_BAD_BITS03;

  }

  if (0 != (tvb_get_uint8(tvb_original, 1) & 0xc0 /*frag*/))

  {

    properties |= PWC_CW_BAD_FRAG;

  }

  {

    /* RFC5086:

     * [LEN (bits (10 to 15) MAY be used to carry the length of the CESoPSN

     * packet (defined as the size of the CESoPSN header + the payload size)

     * if it is less than 64 bytes, and MUST be set to zero otherwise.

     * Note:  If fixed RTP header is used in the encapsulation, it is

     * considered part of the CESoPSN header.]

     *

     * Note that this differs from RFC4385's definition of length:

     * [ If the MPLS payload is less than 64 bytes, the length field

     * MUST be set to the length of the PW payload...]

     *

     * We will use RFC5086's definition here.

     */

    int  cw_len;

    int payload_size_from_packet;

    cw_len = tvb_get_uint8(tvb_original, 1) & 0x3f;

    payload_size_from_packet = packet_size - encaps_size;

    if (cw_len != 0)

    {

      int payload_size_from_cw;

      payload_size_from_cw = cw_len - encaps_size;

      /*

       * Assumptions for error case,

       * will be overwritten if no errors found:

       */

      payload_size = payload_size_from_packet;

      padding_size = 0;

      if (payload_size_from_cw < 0)

      {

        properties |= PWC_CW_BAD_PAYLEN_LT_0;

      }

      else if (payload_size_from_cw > payload_size_from_packet)

      {

        properties |= PWC_CW_BAD_PAYLEN_GT_PACKET;

      }

      else if (payload_size_from_packet >= 64)

      {

        properties |= PWC_CW_BAD_LEN_MUST_BE_0;

      }

      else /* ok */

      {

        payload_size = payload_size_from_cw;

        padding_size = payload_size_from_packet - payload_size_from_cw; /* >=0 */

      }

    }

    else

    {

      payload_size = payload_size_from_packet;

      padding_size = 0;

    }

  }

  {

    uint8_t cw_lm;

    cw_lm = tvb_get_uint8(tvb_original, 0) & 0x0b /*l+mod*/;

    if (NULL == try_val_to_str(cw_lm, vals_cw_lm))

    {

      properties |= PWC_CW_SUSPECT_LM;

    }

    {

      uint8_t l_bit, m_bits;

      l_bit  = (cw_lm & 0x08) >> 3;

      m_bits = (cw_lm & 0x03) >> 0;

      if ((l_bit == 0 && m_bits == 0x0) /*CESoPSN data packet - normal situation*/

          ||(l_bit == 0 && m_bits == 0x2) /*CESoPSN data packet - RDI on the AC*/ )

      {

        if ((payload_size == 0) || ((payload_size % 8) != 0))

        {

          properties |= PWC_PAY_SIZE_BAD;

        }

      }

      else if (l_bit == 1 && m_bits == 0x0) /*TDM data is invalid; payload MAY be omitted*/

      {

        /*allow any size of payload*/

      }

      else /*reserved combinations*/

      {

        /*allow any size of payload*/

      }

    }

  }

  /* fill up columns*/

  col_set_str(pinfo->cinfo, COL_PROTOCOL, "CESoPSN basic (no RTP)");

  col_clear(pinfo->cinfo, COL_INFO);

  if (properties & PWC_ANYOF_CW_BAD)

  {

    col_set_str(pinfo->cinfo, COL_INFO, "CW:Bad, ");

  }

  else if (properties & PWC_ANYOF_CW_SUSPECT)

  {

    col_append_str(pinfo->cinfo, COL_INFO, "CW:Suspect, ");

  }

  if (properties & PWC_PAY_SIZE_BAD)

  {

    col_append_str(pinfo->cinfo, COL_INFO, "Payload size:Bad, ");

  }

  col_append_fstr(pinfo->cinfo, COL_INFO, "TDM octets:%d", (int)payload_size);

  if (padding_size != 0)

  {

    col_append_fstr(pinfo->cinfo, COL_INFO, ", Padding:%d", (int)padding_size);

  }

  {

    proto_item* item;

    item = proto_tree_add_item(tree, proto, tvb_original, 0, -1, ENC_NA);

    pwc_item_append_cw(item,tvb_get_ntohl(tvb_original, 0),true);

    pwc_item_append_text_n_items(item,(int)payload_size,"octet");

    {

      proto_tree* tree2;

      tree2 = proto_item_add_subtree(item, ett_pw_cesopsn);

      {

        tvbuff_t* tvb;

        proto_item* item2;

        tvb = tvb_new_subset_length(tvb_original, 0, PWC_SIZEOF_CW);

        item2 = proto_tree_add_item(tree2, hf_cw, tvb, 0, -1, ENC_NA);

        pwc_item_append_cw(item2,tvb_get_ntohl(tvb, 0),false);

        {

          proto_tree* tree3;

          tree3 = proto_item_add_subtree(item, ett_pw_cesopsn);

          {

            proto_item* item3;

            if (properties & PWC_CW_BAD_BITS03) /*display only if value is wrong*/

            {

              item3 = proto_tree_add_item(tree3, hf_cw_bits03, tvb, 0, 1, ENC_BIG_ENDIAN);

              expert_add_info(pinfo, item3, &ei_cw_bits03);

            }

            item3 = proto_tree_add_item(tree3, hf_cw_lm,  tvb, 0, 1, ENC_BIG_ENDIAN);

            if (properties & PWC_CW_SUSPECT_LM)

            {

              expert_add_info(pinfo, item3, &ei_cw_lm);

            }

            proto_tree_add_item(tree3, hf_cw_r, tvb, 0, 1, ENC_BIG_ENDIAN);

            item3 = proto_tree_add_item(tree3, hf_cw_frg, tvb, 1, 1, ENC_BIG_ENDIAN);

            if (properties & PWC_CW_BAD_FRAG)

            {

              expert_add_info(pinfo, item3, &ei_cw_frg);

            }

            item3 = proto_tree_add_item(tree3, hf_cw_len, tvb, 1, 1, ENC_BIG_ENDIAN);

            if (properties & PWC_CW_BAD_PAYLEN_LT_0)

            {

              expert_add_info_format(pinfo, item3, &ei_pref_cw_len,

                "Bad Length: too small, must be > %d",

                (int)encaps_size);

            }

            if (properties & PWC_CW_BAD_PAYLEN_GT_PACKET)

            {

              expert_add_info_format(pinfo, item3, &ei_pref_cw_len,

                "Bad Length: must be <= than PSN packet size (%d)",

                (int)packet_size);

            }

            if (properties & PWC_CW_BAD_LEN_MUST_BE_0)

            {

              expert_add_info_format(pinfo, item3, &ei_pref_cw_len,

                "Bad Length: must be 0 if CESoPSN packet size (%d) is > 64",

                (int)packet_size);

            }

            proto_tree_add_item(tree3, hf_cw_seq, tvb, 2, 2, ENC_BIG_ENDIAN);

          }

        }

      }

    }

    /* payload */

    if (payload_size == 0)

    {

      if (properties & PWC_PAY_SIZE_BAD)

      {

        expert_add_info_format(pinfo, item, &ei_payload_size_invalid_error,

          "CESoPSN payload: none found. Size of payload must be <> 0");

      }

      else

      {

        expert_add_info(pinfo, item, &ei_payload_size_invalid_undecoded);

      }

    }

    else

    {

      proto_tree* tree2;

      tree2 = proto_item_add_subtree(item, ett_pw_cesopsn);

      {

        proto_item* item2;

        tvbuff_t* tvb;

        tvb = tvb_new_subset_length(tvb_original, PWC_SIZEOF_CW, payload_size);

        item2 = proto_tree_add_item(tree2, hf_payload, tvb, 0, -1, ENC_NA);

        pwc_item_append_text_n_items(item2,(int)payload_size,"octet");

        if (properties & PWC_PAY_SIZE_BAD)

        {

          expert_add_info_format(pinfo, item2, &ei_payload_size_invalid_error,

            "CESoPSN packet payload size must be multiple of 8");

        }

        tree2 = proto_item_add_subtree(item2, ett_pw_cesopsn);

        call_data_dissector(tvb, pinfo, tree2);

        item2 = proto_tree_add_int(tree2, hf_payload_l, tvb, 0, 0

          ,(int)payload_size); /* allow filtering */

        proto_item_set_hidden(item2);

      }

    }

    /* padding */

    if (padding_size > 0)

    {

      proto_tree* tree2;

      tree2 = proto_item_add_subtree(item, ett_pw_cesopsn);

      {

        tvbuff_t* tvb;

        tvb = tvb_new_subset_length(tvb_original, PWC_SIZEOF_CW + payload_size, padding_size);

        call_dissector(pw_padding_handle, tvb, pinfo, tree2);

      }

    }

  }

  return;

}

static

int dissect_pw_cesopsn_mpls( tvbuff_t * tvb_original, packet_info * pinfo, proto_tree * tree, void* data _U_)

{

  dissect_pw_cesopsn(tvb_original,pinfo,tree,PWC_DEMUX_MPLS);

  return tvb_captured_length(tvb_original);

}

static

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

{

  dissect_pw_cesopsn(tvb,pinfo,tree,PWC_DEMUX_UDP);

  return tvb_captured_length(tvb);

}

void proto_register_pw_cesopsn(void)

{

  static hf_register_info hf[] = {

    { &hf_cw  ,{"Control Word"    ,"pwcesopsn.cw"

          ,FT_NONE      ,BASE_NONE    ,NULL

          ,0        ,NULL      ,HFILL }},

    {&hf_cw_bits03,{"Bits 0 to 3"     ,"pwcesopsn.cw.bits03"

        ,FT_UINT8     ,BASE_DEC   ,NULL

        ,0xf0       ,NULL      ,HFILL }},

    { &hf_cw_lm,  {"L+M bits"     ,"pwcesopsn.cw.lm"

         ,FT_UINT8      ,BASE_HEX   ,VALS(vals_cw_lm)

         ,0x0b          ,NULL      ,HFILL }},

    {&hf_cw_r,  {"R bit: Local CE-bound IWF"  ,"pwcesopsn.cw.rbit"

         ,FT_UINT8      ,BASE_DEC   ,VALS(pwc_vals_cw_r_bit)

         ,0x04        ,NULL      ,HFILL }},

    {&hf_cw_frg,  {"Fragmentation"    ,"pwcesopsn.cw.frag"

         ,FT_UINT8      ,BASE_DEC   ,VALS(pwc_vals_cw_frag)

         ,0xc0        ,NULL      ,HFILL }},

    {&hf_cw_len,  {"Length"     ,"pwcesopsn.cw.length"

         ,FT_UINT8      ,BASE_DEC   ,NULL

         ,0x3f        ,NULL      ,HFILL }},

    {&hf_cw_seq,  {"Sequence number"    ,"pwcesopsn.cw.seqno"

         ,FT_UINT16     ,BASE_DEC   ,NULL

         ,0       ,NULL      ,HFILL }},

    {&hf_payload  ,{"TDM payload"     ,"pwcesopsn.payload"

          ,FT_BYTES     ,BASE_NONE    ,NULL

          ,0        ,NULL      ,HFILL }},

    {&hf_payload_l  ,{"TDM payload length"    ,"pwcesopsn.payload.len"

          ,FT_INT32     ,BASE_DEC   ,NULL

          ,0        ,NULL      ,HFILL }}

  };

  static int *ett_array[] = {

    &ett_pw_cesopsn

  };

  static ei_register_info ei[] = {

    { &ei_packet_size_too_small, { "pwcesopsn.packet_size_too_small", PI_MALFORMED, PI_ERROR, "PW packet size is too small to carry sensible information", EXPFILL }},

    { &ei_cw_bits03, { "pwcesopsn.cw.bits03.not_zero", PI_MALFORMED, PI_ERROR, "Bits 0..3 of Control Word must be 0", EXPFILL }},

    { &ei_cw_lm, { "pwcesopsn.cw.lm.reserved", PI_UNDECODED, PI_WARN, "Reserved combination of L and Modifier bits", EXPFILL }},

    { &ei_cw_frg, { "pwcesopsn.cw.frag.not_allowed", PI_MALFORMED, PI_ERROR, "Fragmentation of payload is not allowed for basic CESoPSN mode", EXPFILL }},

    { &ei_pref_cw_len, { "pwcesopsn.cw.length.invalid", PI_MALFORMED, PI_ERROR, "Bad Length: too small", EXPFILL }},

    { &ei_payload_size_invalid_error, { "pwcesopsn.payload.size_invalid", PI_MALFORMED, PI_ERROR, "CESoPSN payload size invalid", EXPFILL }},

    { &ei_payload_size_invalid_undecoded, { "pwcesopsn.payload.undecoded", PI_UNDECODED, PI_NOTE, "CESoPSN payload: omitted to conserve bandwidth", EXPFILL }},

  };

  expert_module_t* expert_pwcesopsn;

  proto = proto_register_protocol("CESoPSN basic NxDS0 mode (no RTP support)", "CESoPSN basic (no RTP)", "pwcesopsn");

  proto_register_field_array(proto, hf, array_length(hf));

  proto_register_subtree_array(ett_array, array_length(ett_array));

  expert_pwcesopsn = expert_register_protocol(proto);

  expert_register_field_array(expert_pwcesopsn, ei, array_length(ei));

  pw_cesopsn_mpls_handle = register_dissector("pw_cesopsn_mpls", dissect_pw_cesopsn_mpls, proto);

  pw_cesopsn_udp_handle = register_dissector("pw_cesopsn_udp", dissect_pw_cesopsn_udp, proto);

}

void proto_reg_handoff_pw_cesopsn(void)

{

  pw_padding_handle = find_dissector_add_dependency("pw_padding", proto);

  /* For Decode As */

  dissector_add_for_decode_as("mpls.label", pw_cesopsn_mpls_handle);

  dissector_add_for_decode_as("mpls.pfn", pw_cesopsn_mpls_handle);

  dissector_add_for_decode_as_with_preference("udp.port", pw_cesopsn_udp_handle);

}

/*

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

 *

 * Local variables:

 * c-basic-offset: 8

 * tab-width: 8

 * indent-tabs-mode: t

 * End:

 *

 * vi: set shiftwidth=8 tabstop=8 noexpandtab:

 * :indentSize=8:tabSize=8:noTabs=false:

 */