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srsRAN_4G/lib/include/srsran/upper/rlc_am_lte.h

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/**
* Copyright 2013-2021 Software Radio Systems Limited
*
* This file is part of srsRAN.
*
* srsRAN is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of
* the License, or (at your option) any later version.
*
* srsRAN is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* A copy of the GNU Affero General Public License can be found in
* the LICENSE file in the top-level directory of this distribution
* and at http://www.gnu.org/licenses/.
*
*/
#ifndef SRSRAN_RLC_AM_LTE_H
#define SRSRAN_RLC_AM_LTE_H
#include "srsran/adt/accumulators.h"
#include "srsran/adt/circular_array.h"
#include "srsran/adt/circular_map.h"
#include "srsran/adt/intrusive_list.h"
#include "srsran/common/buffer_pool.h"
#include "srsran/common/common.h"
#include "srsran/common/srsran_assert.h"
#include "srsran/common/task_scheduler.h"
#include "srsran/common/timeout.h"
#include "srsran/interfaces/pdcp_interface_types.h"
#include "srsran/upper/byte_buffer_queue.h"
#include "srsran/upper/rlc_am_base.h"
#include "srsran/upper/rlc_common.h"
#include <deque>
#include <list>
#include <map>
namespace srsran {
#undef RLC_AM_BUFFER_DEBUG
class rlc_amd_tx_pdu;
class pdcp_pdu_info;
/// Pool that manages the allocation of RLC AM PDU Segments to RLC PDUs and tracking of segments ACK state
struct rlc_am_pdu_segment_pool {
const static size_t MAX_POOL_SIZE = 16384;
using rlc_list_tag = default_intrusive_tag;
struct free_list_tag {};
/// RLC AM PDU Segment, containing the PDCP SN and RLC SN it has been assigned to, and its current ACK state
struct segment_resource : public intrusive_forward_list_element<rlc_list_tag>,
public intrusive_forward_list_element<free_list_tag>,
public intrusive_double_linked_list_element<> {
const static uint32_t invalid_rlc_sn = std::numeric_limits<uint32_t>::max();
const static uint32_t invalid_pdcp_sn = std::numeric_limits<uint32_t>::max() - 1; // -1 for Status Report
int id() const;
void release_pdcp_sn();
void release_rlc_sn();
uint32_t rlc_sn() const { return rlc_sn_; }
uint32_t pdcp_sn() const { return pdcp_sn_; }
bool empty() const { return rlc_sn_ == invalid_rlc_sn and pdcp_sn_ == invalid_pdcp_sn; }
private:
friend struct rlc_am_pdu_segment_pool;
uint32_t rlc_sn_ = invalid_rlc_sn;
uint32_t pdcp_sn_ = invalid_pdcp_sn;
rlc_am_pdu_segment_pool* parent_pool = nullptr;
};
rlc_am_pdu_segment_pool();
rlc_am_pdu_segment_pool(const rlc_am_pdu_segment_pool&) = delete;
rlc_am_pdu_segment_pool(rlc_am_pdu_segment_pool&&) = delete;
rlc_am_pdu_segment_pool& operator=(const rlc_am_pdu_segment_pool&) = delete;
rlc_am_pdu_segment_pool& operator=(rlc_am_pdu_segment_pool&&) = delete;
bool has_segments() const { return not free_list.empty(); }
bool make_segment(rlc_amd_tx_pdu& rlc_list, pdcp_pdu_info& pdcp_info);
private:
intrusive_forward_list<segment_resource, free_list_tag> free_list;
std::array<segment_resource, MAX_POOL_SIZE> segments;
};
/// RLC AM PDU Segment, containing the PDCP SN and RLC SN it has been assigned to, and its current ACK state
using rlc_am_pdu_segment = rlc_am_pdu_segment_pool::segment_resource;
struct rlc_amd_rx_pdu {
rlc_amd_pdu_header_t header;
unique_byte_buffer_t buf;
uint32_t rlc_sn;
rlc_amd_rx_pdu() = default;
explicit rlc_amd_rx_pdu(uint32_t rlc_sn_) : rlc_sn(rlc_sn_) {}
};
struct rlc_amd_rx_pdu_segments_t {
std::list<rlc_amd_rx_pdu> segments;
};
/// Class that contains the parameters and state (e.g. segments) of a RLC PDU
class rlc_amd_tx_pdu
{
using list_type = intrusive_forward_list<rlc_am_pdu_segment>;
const static uint32_t invalid_rlc_sn = std::numeric_limits<uint32_t>::max();
list_type list;
public:
using iterator = typename list_type::iterator;
using const_iterator = typename list_type::const_iterator;
const uint32_t rlc_sn = invalid_rlc_sn;
uint32_t retx_count = 0;
rlc_amd_pdu_header_t header;
unique_byte_buffer_t buf;
explicit rlc_amd_tx_pdu(uint32_t rlc_sn_) : rlc_sn(rlc_sn_) {}
rlc_amd_tx_pdu(const rlc_amd_tx_pdu&) = delete;
rlc_amd_tx_pdu(rlc_amd_tx_pdu&& other) noexcept = default;
rlc_amd_tx_pdu& operator=(const rlc_amd_tx_pdu& other) = delete;
rlc_amd_tx_pdu& operator=(rlc_amd_tx_pdu&& other) = delete;
~rlc_amd_tx_pdu();
// Segment List Interface
void add_segment(rlc_am_pdu_segment& segment) { list.push_front(&segment); }
const_iterator begin() const { return list.begin(); }
const_iterator end() const { return list.end(); }
iterator begin() { return list.begin(); }
iterator end() { return list.end(); }
};
struct rlc_amd_retx_t {
uint32_t sn;
bool is_segment;
uint32_t so_start;
uint32_t so_end;
};
struct rlc_sn_info_t {
uint32_t sn;
bool is_acked;
};
/// Class that contains the parameters and state (e.g. unACKed segments) of a PDCP PDU
class pdcp_pdu_info
{
using list_type = intrusive_double_linked_list<rlc_am_pdu_segment>;
list_type list; // List of unACKed RLC PDUs that contain segments that belong to the PDCP PDU.
public:
const static uint32_t status_report_sn = std::numeric_limits<uint32_t>::max();
const static uint32_t invalid_pdcp_sn = std::numeric_limits<uint32_t>::max() - 1;
using iterator = typename list_type::iterator;
using const_iterator = typename list_type::const_iterator;
// Copy is forbidden to avoid multiple PDCP SN references to the same segment
pdcp_pdu_info() = default;
pdcp_pdu_info(pdcp_pdu_info&&) noexcept = default;
pdcp_pdu_info(const pdcp_pdu_info&) noexcept = delete;
pdcp_pdu_info& operator=(const pdcp_pdu_info&) noexcept = delete;
pdcp_pdu_info& operator=(pdcp_pdu_info&&) noexcept = default;
~pdcp_pdu_info() { clear(); }
uint32_t sn = invalid_pdcp_sn;
bool fully_txed = false; // Boolean indicating if the SDU is fully transmitted.
bool fully_acked() const { return fully_txed and list.empty(); }
bool valid() const { return sn != invalid_pdcp_sn; }
// Interface for list of unACKed RLC segments of the PDCP PDU
void add_segment(rlc_am_pdu_segment& segment) { list.push_front(&segment); }
void ack_segment(rlc_am_pdu_segment& segment);
void clear()
{
sn = invalid_pdcp_sn;
fully_txed = false;
while (not list.empty()) {
ack_segment(list.front());
}
}
const_iterator begin() const { return list.begin(); }
const_iterator end() const { return list.end(); }
};
template <class T>
struct rlc_ringbuffer_t {
T& add_pdu(size_t sn)
{
srsran_expect(not has_sn(sn), "The same SN=%zd should not be added twice", sn);
window.overwrite(sn, T(sn));
return window[sn];
}
void remove_pdu(size_t sn)
{
srsran_expect(has_sn(sn), "The removed SN=%zd is not in the window", sn);
window.erase(sn);
}
T& operator[](size_t sn) { return window[sn]; }
size_t size() const { return window.size(); }
bool empty() const { return window.empty(); }
void clear() { window.clear(); }
bool has_sn(uint32_t sn) const { return window.contains(sn); }
// Return the sum data bytes of all active PDUs (check PDU is non-null)
uint32_t get_buffered_bytes()
{
uint32_t buff_size = 0;
for (const auto& pdu : window) {
if (pdu.second.buf != nullptr) {
buff_size += pdu.second.buf->N_bytes;
}
}
return buff_size;
}
private:
srsran::static_circular_map<uint32_t, T, RLC_AM_WINDOW_SIZE> window;
};
struct buffered_pdcp_pdu_list {
public:
explicit buffered_pdcp_pdu_list();
void clear();
void add_pdcp_sdu(uint32_t sn)
{
srsran_expect(sn <= max_pdcp_sn or sn == status_report_sn, "Invalid PDCP SN=%d", sn);
srsran_assert(not has_pdcp_sn(sn), "Cannot re-add same PDCP SN twice");
pdcp_pdu_info& pdu = get_pdu_(sn);
if (pdu.valid()) {
pdu.clear();
count--;
}
pdu.sn = sn;
count++;
}
void clear_pdcp_sdu(uint32_t sn)
{
pdcp_pdu_info& pdu = get_pdu_(sn);
if (not pdu.valid()) {
return;
}
pdu.clear();
count--;
}
pdcp_pdu_info& operator[](uint32_t sn)
{
srsran_expect(has_pdcp_sn(sn), "Invalid access to non-existent PDCP SN=%d", sn);
return get_pdu_(sn);
}
bool has_pdcp_sn(uint32_t pdcp_sn) const
{
srsran_expect(pdcp_sn <= max_pdcp_sn or pdcp_sn == status_report_sn, "Invalid PDCP SN=%d", pdcp_sn);
return get_pdu_(pdcp_sn).sn == pdcp_sn;
}
uint32_t nof_sdus() const { return count; }
private:
const static size_t max_pdcp_sn = 262143u;
const static size_t buffer_size = 4096u;
const static uint32_t status_report_sn = pdcp_pdu_info::status_report_sn;
pdcp_pdu_info& get_pdu_(uint32_t sn)
{
return (sn == status_report_sn) ? status_report_pdu : buffered_pdus[static_cast<size_t>(sn % buffer_size)];
}
const pdcp_pdu_info& get_pdu_(uint32_t sn) const
{
return (sn == status_report_sn) ? status_report_pdu : buffered_pdus[static_cast<size_t>(sn % buffer_size)];
}
// size equal to buffer_size
std::vector<pdcp_pdu_info> buffered_pdus;
pdcp_pdu_info status_report_pdu;
uint32_t count = 0;
};
class pdu_retx_queue
{
public:
rlc_amd_retx_t& push()
{
assert(not full());
rlc_amd_retx_t& p = buffer[wpos];
wpos = (wpos + 1) % RLC_AM_WINDOW_SIZE;
return p;
}
void pop() { rpos = (rpos + 1) % RLC_AM_WINDOW_SIZE; }
rlc_amd_retx_t& front()
{
assert(not empty());
return buffer[rpos];
}
void clear()
{
wpos = 0;
rpos = 0;
}
bool has_sn(uint32_t sn) const
{
for (size_t i = rpos; i != wpos; i = (i + 1) % RLC_AM_WINDOW_SIZE) {
if (buffer[i].sn == sn) {
return true;
}
}
return false;
}
size_t size() const { return (wpos >= rpos) ? wpos - rpos : RLC_AM_WINDOW_SIZE + wpos - rpos; }
bool empty() const { return wpos == rpos; }
bool full() const { return size() == RLC_AM_WINDOW_SIZE - 1; }
private:
std::array<rlc_amd_retx_t, RLC_AM_WINDOW_SIZE> buffer;
size_t wpos = 0;
size_t rpos = 0;
};
class rlc_am_lte : public rlc_common
{
public:
rlc_am_lte(srslog::basic_logger& logger,
uint32_t lcid_,
srsue::pdcp_interface_rlc* pdcp_,
srsue::rrc_interface_rlc* rrc_,
srsran::timer_handler* timers_);
bool configure(const rlc_config_t& cfg_);
void reestablish();
void stop();
void empty_queue();
rlc_mode_t get_mode();
uint32_t get_bearer();
// PDCP interface
void write_sdu(unique_byte_buffer_t sdu);
void discard_sdu(uint32_t pdcp_sn);
bool sdu_queue_is_full();
// MAC interface
bool has_data();
uint32_t get_buffer_state();
int read_pdu(uint8_t* payload, uint32_t nof_bytes);
void write_pdu(uint8_t* payload, uint32_t nof_bytes);
rlc_bearer_metrics_t get_metrics();
void reset_metrics();
void set_bsr_callback(bsr_callback_t callback);
private:
// Transmitter sub-class
class rlc_am_lte_tx : public timer_callback
{
public:
rlc_am_lte_tx(rlc_am_lte* parent_);
~rlc_am_lte_tx();
bool configure(const rlc_config_t& cfg_);
void empty_queue();
void reestablish();
void stop();
int write_sdu(unique_byte_buffer_t sdu);
int read_pdu(uint8_t* payload, uint32_t nof_bytes);
void discard_sdu(uint32_t discard_sn);
bool sdu_queue_is_full();
bool has_data();
uint32_t get_buffer_state();
// Timeout callback interface
void timer_expired(uint32_t timeout_id);
// Interface for Rx subclass
void handle_control_pdu(uint8_t* payload, uint32_t nof_bytes);
void set_bsr_callback(bsr_callback_t callback);
private:
int build_status_pdu(uint8_t* payload, uint32_t nof_bytes);
int build_retx_pdu(uint8_t* payload, uint32_t nof_bytes);
int build_segment(uint8_t* payload, uint32_t nof_bytes, rlc_amd_retx_t retx);
int build_data_pdu(uint8_t* payload, uint32_t nof_bytes);
void update_notification_ack_info(uint32_t rlc_sn);
void debug_state();
int required_buffer_size(rlc_amd_retx_t retx);
void retransmit_pdu();
// Helpers
bool poll_required();
bool do_status();
void check_sn_reached_max_retx(uint32_t sn);
rlc_am_lte* parent = nullptr;
byte_buffer_pool* pool = nullptr;
srslog::basic_logger& logger;
rlc_am_pdu_segment_pool segment_pool;
/****************************************************************************
* Configurable parameters
* Ref: 3GPP TS 36.322 v10.0.0 Section 7
***************************************************************************/
rlc_am_config_t cfg = {};
// TX SDU buffers
byte_buffer_queue tx_sdu_queue;
unique_byte_buffer_t tx_sdu;
bool tx_enabled = false;
/****************************************************************************
* State variables and counters
* Ref: 3GPP TS 36.322 v10.0.0 Section 7
***************************************************************************/
// Tx state variables
uint32_t vt_a = 0; // ACK state. SN of next PDU in sequence to be ACKed. Low edge of tx window.
uint32_t vt_ms = RLC_AM_WINDOW_SIZE; // Max send state. High edge of tx window. vt_a + window_size.
uint32_t vt_s = 0; // Send state. SN to be assigned for next PDU.
uint32_t poll_sn = 0; // Poll send state. SN of most recent PDU txed with poll bit set.
// Tx counters
uint32_t pdu_without_poll = 0;
uint32_t byte_without_poll = 0;
rlc_status_pdu_t tx_status;
/****************************************************************************
* Timers
* Ref: 3GPP TS 36.322 v10.0.0 Section 7
***************************************************************************/
srsran::timer_handler::unique_timer poll_retx_timer;
srsran::timer_handler::unique_timer status_prohibit_timer;
// SDU info for PDCP notifications
buffered_pdcp_pdu_list undelivered_sdu_info_queue;
// Callback function for buffer status report
bsr_callback_t bsr_callback;
// Tx windows
rlc_ringbuffer_t<rlc_amd_tx_pdu> tx_window;
pdu_retx_queue retx_queue;
pdcp_sn_vector_t notify_info_vec;
// Mutexes
std::mutex mutex;
// default to RLC SDU queue length
const uint32_t MAX_SDUS_PER_RLC_PDU = RLC_TX_QUEUE_LEN;
};
// Receiver sub-class
class rlc_am_lte_rx : public timer_callback
{
public:
rlc_am_lte_rx(rlc_am_lte* parent_);
~rlc_am_lte_rx();
bool configure(rlc_am_config_t cfg_);
void reestablish();
void stop();
void write_pdu(uint8_t* payload, uint32_t nof_bytes);
uint32_t get_rx_buffered_bytes(); // returns sum of PDUs in rx_window
uint32_t get_sdu_rx_latency_ms();
// Timeout callback interface
void timer_expired(uint32_t timeout_id);
// Functions needed by Tx subclass to query rx state
int get_status_pdu_length();
int get_status_pdu(rlc_status_pdu_t* status, const uint32_t nof_bytes);
bool get_do_status();
void reset_status(); // called when status PDU has been sent
private:
void handle_data_pdu(uint8_t* payload, uint32_t nof_bytes, rlc_amd_pdu_header_t& header);
void handle_data_pdu_segment(uint8_t* payload, uint32_t nof_bytes, rlc_amd_pdu_header_t& header);
void reassemble_rx_sdus();
bool inside_rx_window(const int16_t sn);
void debug_state();
void print_rx_segments();
bool add_segment_and_check(rlc_amd_rx_pdu_segments_t* pdu, rlc_amd_rx_pdu* segment);
rlc_am_lte* parent = nullptr;
byte_buffer_pool* pool = nullptr;
srslog::basic_logger& logger;
/****************************************************************************
* Configurable parameters
* Ref: 3GPP TS 36.322 v10.0.0 Section 7
***************************************************************************/
rlc_am_config_t cfg = {};
// RX SDU buffers
unique_byte_buffer_t rx_sdu;
/****************************************************************************
* State variables and counters
* Ref: 3GPP TS 36.322 v10.0.0 Section 7
***************************************************************************/
// Rx state variables
uint32_t vr_r = 0; // Receive state. SN following last in-sequence received PDU. Low edge of rx window
uint32_t vr_mr = RLC_AM_WINDOW_SIZE; // Max acceptable receive state. High edge of rx window. vr_r + window size.
uint32_t vr_x = 0; // t_reordering state. SN following PDU which triggered t_reordering.
uint32_t vr_ms = 0; // Max status tx state. Highest possible value of SN for ACK_SN in status PDU.
uint32_t vr_h = 0; // Highest rx state. SN following PDU with highest SN among rxed PDUs.
// Mutex to protect members
std::mutex mutex;
// Rx windows
rlc_ringbuffer_t<rlc_amd_rx_pdu> rx_window;
std::map<uint32_t, rlc_amd_rx_pdu_segments_t> rx_segments;
bool poll_received = false;
bool do_status = false;
/****************************************************************************
* Timers
* Ref: 3GPP TS 36.322 v10.0.0 Section 7
***************************************************************************/
srsran::timer_handler::unique_timer reordering_timer;
srsran::rolling_average<double> sdu_rx_latency_ms;
};
// Common variables needed/provided by parent class
srsue::rrc_interface_rlc* rrc = nullptr;
srslog::basic_logger& logger;
srsue::pdcp_interface_rlc* pdcp = nullptr;
srsran::timer_handler* timers = nullptr;
uint32_t lcid = 0;
rlc_config_t cfg = {};
std::string rb_name;
static const int poll_periodicity = 8; // After how many data PDUs a status PDU shall be requested
// Rx and Tx objects
rlc_am_lte_tx tx;
rlc_am_lte_rx rx;
rlc_bearer_metrics_t metrics = {};
};
/****************************************************************************
* Header pack/unpack helper functions
* Ref: 3GPP TS 36.322 v10.0.0 Section 6.2.1
***************************************************************************/
void rlc_am_read_data_pdu_header(byte_buffer_t* pdu, rlc_amd_pdu_header_t* header);
void rlc_am_read_data_pdu_header(uint8_t** payload, uint32_t* nof_bytes, rlc_amd_pdu_header_t* header);
void rlc_am_write_data_pdu_header(rlc_amd_pdu_header_t* header, byte_buffer_t* pdu);
void rlc_am_write_data_pdu_header(rlc_amd_pdu_header_t* header, uint8_t** payload);
void rlc_am_read_status_pdu(byte_buffer_t* pdu, rlc_status_pdu_t* status);
void rlc_am_read_status_pdu(uint8_t* payload, uint32_t nof_bytes, rlc_status_pdu_t* status);
void rlc_am_write_status_pdu(rlc_status_pdu_t* status, byte_buffer_t* pdu);
int rlc_am_write_status_pdu(rlc_status_pdu_t* status, uint8_t* payload);
uint32_t rlc_am_packed_length(rlc_amd_pdu_header_t* header);
uint32_t rlc_am_packed_length(rlc_status_pdu_t* status);
uint32_t rlc_am_packed_length(rlc_amd_retx_t retx);
bool rlc_am_is_valid_status_pdu(const rlc_status_pdu_t& status);
bool rlc_am_is_pdu_segment(uint8_t* payload);
std::string rlc_am_undelivered_sdu_info_to_string(const std::map<uint32_t, pdcp_pdu_info>& info_queue);
void log_rlc_amd_pdu_header_to_string(srslog::log_channel& log_ch, const rlc_amd_pdu_header_t& header);
bool rlc_am_start_aligned(const uint8_t fi);
bool rlc_am_end_aligned(const uint8_t fi);
bool rlc_am_is_unaligned(const uint8_t fi);
bool rlc_am_not_start_aligned(const uint8_t fi);
} // namespace srsran
#endif // SRSRAN_RLC_AM_LTE_H
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