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dvmhost/src/common/p25/data/DataHeader.cpp

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// SPDX-License-Identifier: GPL-2.0-only
/**
* Digital Voice Modem - Common Library
* GPLv2 Open Source. Use is subject to license terms.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* @package DVM / Common Library
* @license GPLv2 License (https://opensource.org/licenses/GPL-2.0)
*
* Copyright (C) 2018,2022,2024 Bryan Biedenkapp, N2PLL
*
*/
#include "Defines.h"
#include "p25/P25Defines.h"
#include "p25/data/DataHeader.h"
#include "edac/CRC.h"
#include "Log.h"
#include "Utils.h"
using namespace p25;
using namespace p25::defines;
using namespace p25::data;
#include <cassert>
#include <cstring>
// ---------------------------------------------------------------------------
// Static Class Members
// ---------------------------------------------------------------------------
#if FORCE_TSBK_CRC_WARN
bool DataHeader::m_warnCRC = true;
#else
bool DataHeader::m_warnCRC = false;
#endif
// ---------------------------------------------------------------------------
// Public Class Members
// ---------------------------------------------------------------------------
/// <summary>
/// Initializes a new instance of the DataHeader class.
/// </summary>
DataHeader::DataHeader() :
m_ackNeeded(false),
m_outbound(false),
m_fmt(PDUFormatType::CONFIRMED),
m_sap(0U),
m_mfId(MFG_STANDARD),
m_llId(0U),
m_blocksToFollow(0U),
m_padLength(0U),
m_F(true),
m_S(false),
m_fsn(0U),
m_Ns(0U),
m_lastFragment(true),
m_headerOffset(0U),
m_srcLlId(0U),
m_rspClass(PDUAckClass::NACK),
m_rspType(PDUAckType::NACK_ILLEGAL),
m_rspStatus(0U),
m_ambtOpcode(0U),
m_ambtField8(0U),
m_ambtField9(0U),
m_trellis(),
m_data(nullptr)
{
m_data = new uint8_t[P25_PDU_HEADER_LENGTH_BYTES];
::memset(m_data, 0x00U, P25_PDU_HEADER_LENGTH_BYTES);
}
/// <summary>
/// Finalizes a instance of the DataHeader class.
/// </summary>
DataHeader::~DataHeader()
{
delete[] m_data;
}
/// <summary>
/// Decodes P25 PDU data header.
/// </summary>
/// <param name="data"></param>
/// <param name="noTrellis"></param>
/// <returns>True, if PDU data header was decoded, otherwise false.</returns>
bool DataHeader::decode(const uint8_t* data, bool noTrellis)
{
assert(data != nullptr);
// decode 1/2 rate Trellis & check CRC-CCITT 16
bool valid = true;
if (noTrellis) {
::memcpy(m_data, data, P25_PDU_HEADER_LENGTH_BYTES);
}
else {
valid = m_trellis.decode12(data, m_data);
}
if (valid) {
valid = edac::CRC::checkCCITT162(m_data, P25_PDU_HEADER_LENGTH_BYTES);
if (!valid) {
if (m_warnCRC) {
// if we're already warning instead of erroring CRC, don't announce invalid CRC in the
// case where no CRC is defined
if ((m_data[P25_PDU_HEADER_LENGTH_BYTES - 2U] != 0x00U) && (m_data[P25_PDU_HEADER_LENGTH_BYTES - 1U] != 0x00U)) {
LogWarning(LOG_P25, "DataHeader::decode(), failed CRC CCITT-162 check");
}
valid = true; // ignore CRC error
}
else {
LogError(LOG_P25, "DataHeader::decode(), failed CRC CCITT-162 check");
}
}
}
if (!valid) {
return false;
}
#if DEBUG_P25_PDU_DATA
Utils::dump(1U, "P25, DataHeader::decode(), PDU Header Data", m_data, P25_PDU_HEADER_LENGTH_BYTES);
#endif
m_ackNeeded = (m_data[0U] & 0x40U) == 0x40U; // Acknowledge Needed
m_outbound = (m_data[0U] & 0x20U) == 0x20U; // Inbound/Outbound
m_fmt = m_data[0U] & 0x1FU; // Packet Format
m_sap = m_data[1U] & 0x3FU; // Service Access Point
m_mfId = m_data[2U]; // Mfg Id.
m_llId = (m_data[3U] << 16) + (m_data[4U] << 8) + m_data[5U]; // Logical Link ID
m_F = (m_data[6U] & 0x80U) == 0x80U; // Full Message Flag
m_blocksToFollow = m_data[6U] & 0x7FU; // Block Frames to Follow
m_padLength = m_data[7U] & 0x1FU; // Pad Byte Count
if (m_fmt == PDUFormatType::RSP || m_fmt == PDUFormatType::AMBT) {
m_padLength = 0U;
}
switch (m_fmt) {
case PDUFormatType::CONFIRMED:
m_S = (m_data[8U] & 0x80U) == 0x80U; // Re-synchronize Flag
m_Ns = (m_data[8U] >> 4) & 0x07U; // Packet Sequence No.
m_fsn = m_data[8U] & 0x07U; // Fragment Sequence No.
m_lastFragment = (m_data[8U] & 0x08U) == 0x08U; // Last Fragment Flag
m_headerOffset = m_data[9U] & 0x3FU; // Data Header Offset
break;
case PDUFormatType::RSP:
m_ackNeeded = false;
m_sap = PDUSAP::USER_DATA;
m_rspClass = (m_data[1U] >> 6) & 0x03U; // Response Class
m_rspType = (m_data[1U] >> 3) & 0x07U; // Response Type
m_rspStatus = m_data[1U] & 0x07U; // Response Status
if (!m_F) {
m_srcLlId = (m_data[7U] << 16) + (m_data[8U] << 8) + m_data[9U]; // Source Logical Link ID
}
break;
case PDUFormatType::AMBT:
m_ambtOpcode = m_data[7U] & 0x3FU; // AMBT Opcode
m_ambtField8 = m_data[8U]; // AMBT Field 8
m_ambtField9 = m_data[9U]; // AMBT Field 9
// fall-thru
case PDUFormatType::UNCONFIRMED:
default:
m_ackNeeded = false;
m_S = false;
m_Ns = 0U;
m_fsn = 0U;
m_headerOffset = 0U;
break;
}
return true;
}
/// <summary>
/// Encodes P25 PDU data header.
/// </summary>
/// <param name="data"></param>
void DataHeader::encode(uint8_t* data, bool noTrellis)
{
assert(data != nullptr);
uint8_t header[P25_PDU_HEADER_LENGTH_BYTES];
::memset(header, 0x00U, P25_PDU_HEADER_LENGTH_BYTES);
if (m_fmt == PDUFormatType::UNCONFIRMED || m_fmt == PDUFormatType::RSP) {
m_ackNeeded = false;
}
if (m_fmt == PDUFormatType::CONFIRMED && !m_ackNeeded) {
LogWarning(LOG_P25, "DataHeader::encode(), invalid values for confirmed PDU, ackNeeded = %u", m_ackNeeded);
m_ackNeeded = true; // force set this to true
}
header[0U] = (m_ackNeeded ? 0x40U : 0x00U) + // Acknowledge Needed
(m_outbound ? 0x20U : 0x00U) + // Inbound/Outbound
(m_fmt & 0x1FU); // Packet Format
header[1U] = m_sap & 0x3FU; // Service Access Point
header[1U] |= 0xC0U;
header[2U] = m_mfId; // Mfg Id.
header[3U] = (m_llId >> 16) & 0xFFU; // Logical Link ID
header[4U] = (m_llId >> 8) & 0xFFU;
header[5U] = (m_llId >> 0) & 0xFFU;
header[6U] = (m_F ? 0x80U : 0x00U) + // Full Message Flag
(m_blocksToFollow & 0x7FU); // Blocks Frames to Follow
switch (m_fmt) {
case PDUFormatType::CONFIRMED:
header[7U] = (m_padLength & 0x1FU); // Pad Byte Count
header[8U] = (m_S ? 0x80U : 0x00U) + // Re-synchronize Flag
((m_Ns & 0x07U) << 4) + // Packet Sequence No.
(m_lastFragment ? 0x08U : 0x00U) + // Last Fragment Flag
(m_fsn & 0x07); // Fragment Sequence No.
header[9U] = m_headerOffset & 0x3FU; // Data Header Offset
break;
case PDUFormatType::RSP:
header[1U] = ((m_rspClass & 0x03U) << 6) + // Response Class
((m_rspType & 0x07U) << 3) + // Response Type
((m_rspStatus & 0x07U)); // Response Status
if (!m_F) {
header[7U] = (m_srcLlId >> 16) & 0xFFU; // Source Logical Link ID
header[8U] = (m_srcLlId >> 8) & 0xFFU;
header[9U] = (m_srcLlId >> 0) & 0xFFU;
}
break;
case PDUFormatType::AMBT:
header[7U] = (m_ambtOpcode & 0x3FU); // AMBT Opcode
header[8U] = m_ambtField8; // AMBT Field 8
header[9U] = m_ambtField9; // AMBT Field 9
break;
case PDUFormatType::UNCONFIRMED:
default:
header[7U] = (m_padLength & 0x1FU); // Pad Byte Count
header[8U] = 0x00U;
header[9U] = m_headerOffset & 0x3FU; // Data Header Offset
break;
}
// compute CRC-CCITT 16
edac::CRC::addCCITT162(header, P25_PDU_HEADER_LENGTH_BYTES);
#if DEBUG_P25_PDU_DATA
Utils::dump(1U, "P25, DataHeader::encode(), PDU Header Data", header, P25_PDU_HEADER_LENGTH_BYTES);
#endif
if (!noTrellis) {
// encode 1/2 rate Trellis
m_trellis.encode12(header, data);
} else {
::memcpy(data, header, P25_PDU_HEADER_LENGTH_BYTES);
}
}
/// <summary>
/// Helper to reset data values to defaults.
/// </summary>
void DataHeader::reset()
{
m_ackNeeded = false;
m_outbound = false;
m_fmt = PDUFormatType::CONFIRMED;
m_sap = PDUSAP::USER_DATA;
m_mfId = MFG_STANDARD;
m_llId = 0U;
m_F = true;
m_blocksToFollow = 0U;
m_padLength = 0U;
m_S = false;
m_Ns = 0U;
m_fsn = 0U;
m_lastFragment = true;
m_headerOffset = 0U;
m_srcLlId = 0U;
m_rspClass = PDUAckClass::NACK;
m_rspType = PDUAckType::NACK_ILLEGAL;
m_rspStatus = 0U;
m_ambtOpcode = 0U;
m_ambtField8 = 0U;
m_ambtField9 = 0U;
::memset(m_data, 0x00U, P25_PDU_HEADER_LENGTH_BYTES);
}
/// <summary>
/// Gets the total length in bytes of enclosed packet data.
/// </summary>
/// <returns></returns>
uint32_t DataHeader::getPacketLength() const
{
if (m_fmt == PDUFormatType::CONFIRMED) {
return P25_PDU_CONFIRMED_DATA_LENGTH_BYTES * m_blocksToFollow - 4 - m_padLength;
}
else {
return P25_PDU_UNCONFIRMED_LENGTH_BYTES * m_blocksToFollow - 4 - m_padLength;
}
}
/// <summary>
/// Gets the raw header data.
/// </summary>
/// <returns></returns>
uint32_t DataHeader::getData(uint8_t* buffer) const
{
assert(buffer != nullptr);
assert(m_data != nullptr);
::memcpy(buffer, m_data, P25_PDU_HEADER_LENGTH_BYTES);
return P25_PDU_HEADER_LENGTH_BYTES;
}
/// <summary>
/// Helper to determine the pad length for a given packet length.
/// </summary>
/// <param name="fmt"></param>
/// <param name="packetLength"></param>
uint32_t DataHeader::calculatePadLength(uint8_t fmt, uint32_t packetLength)
{
uint32_t len = packetLength + 4;
if (fmt == PDUFormatType::CONFIRMED) {
return P25_PDU_CONFIRMED_DATA_LENGTH_BYTES - (len % P25_PDU_CONFIRMED_DATA_LENGTH_BYTES);
}
else {
return P25_PDU_UNCONFIRMED_LENGTH_BYTES - (len % P25_PDU_UNCONFIRMED_LENGTH_BYTES);
}
}
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