RLC discard (#2515)

* Added ability to discard to dyn_block_queue

* Change way of keeping track of SDUs

* Check nullptr in poping callback. Starting to check for nullptr in RLC read_pdu.

* Adding RLC discard tests

* Clearing PDCP info when RLC discard happens

* Read SDUs until they are no longer nullptr

* Changed discard_if to use template argument

lib/include/srsran/adt/circular_buffer.h

@@ -18,6 +18,7 @@
 #include <array>
 #include <cassert>
 #include <condition_variable>
+#include <functional>
 #include <mutex>
 #include <thread>
 #include <type_traits>
@@ -156,6 +157,19 @@ public:
     buffer.resize(size);
   }
 
+  template <typename F>
+  T discard_if(const F& func)
+  {
+    for (auto it = buffer.begin(); it != buffer.end(); it++) {
+      if (*it != nullptr && func(*it)) {
+        T tmp = std::move(*it);
+        *it   = nullptr;
+        return tmp;
+      }
+    }
+    return nullptr;
+  }
+
 private:
   Container buffer;
   size_t    rpos  = 0;
@@ -264,6 +278,18 @@ public:
     return false;
   }
 
+  template <typename F>
+  bool discard_if(const F& func)
+  {
+    std::lock_guard<std::mutex> lock(mutex);
+    T                           tmp = circ_buffer.discard_if(func);
+    if (tmp == nullptr) {
+      return false;
+    }
+    pop_func(tmp);
+    return true;
+  }
+
 protected:
   bool                    active      = true;
   uint8_t                 nof_waiting = 0;
@@ -443,6 +469,12 @@ public:
     base_t(push_callback, pop_callback, size)
   {}
   void set_size(size_t size) { base_t::circ_buffer.set_size(size); }
+
+  template <typename F>
+  bool discard_if(const F& func)
+  {
+    return base_t::discard_if(func);
+  }
 };
 
 } // namespace srsran

lib/include/srsran/upper/byte_buffer_queue.h

@@ -23,7 +23,9 @@
 
 #include "srsran/adt/circular_buffer.h"
 #include "srsran/common/block_queue.h"
+#include "srsran/common/byte_buffer.h"
 #include "srsran/common/common.h"
+#include <functional>
 #include <pthread.h>
 
 namespace srsran {
@@ -31,7 +33,9 @@ namespace srsran {
 class byte_buffer_queue
 {
 public:
-  byte_buffer_queue(int capacity = 128) : queue(capacity, push_callback(unread_bytes), pop_callback(unread_bytes)) {}
+  byte_buffer_queue(int capacity = 128) :
+    queue(capacity, push_callback(unread_bytes, n_sdus), pop_callback(unread_bytes, n_sdus))
+  {}
 
   void write(unique_byte_buffer_t msg) { queue.push_blocking(std::move(msg)); }
 
@@ -46,6 +50,7 @@ public:
 
   void     resize(uint32_t capacity) { queue.set_size(capacity); }
   uint32_t size() { return (uint32_t)queue.size(); }
+  uint32_t get_n_sdus() { return n_sdus; }
 
   uint32_t size_bytes() { return unread_bytes; }
 
@@ -67,20 +72,42 @@ public:
 
   bool is_full() { return queue.full(); }
 
+  template <typename F>
+  bool discard_if(const F& func)
+  {
+    return queue.discard_if(func);
+  }
+
 private:
   struct push_callback {
-    explicit push_callback(uint32_t& unread_bytes_) : unread_bytes(&unread_bytes_) {}
-    void      operator()(const unique_byte_buffer_t& msg) { *unread_bytes += msg->N_bytes; }
+    explicit push_callback(uint32_t& unread_bytes_, uint32_t& n_sdus_) : unread_bytes(&unread_bytes_), n_sdus(&n_sdus_)
+    {}
+    void operator()(const unique_byte_buffer_t& msg)
+    {
+      *unread_bytes += msg->N_bytes;
+      (*n_sdus)++;
+    }
     uint32_t* unread_bytes;
+    uint32_t* n_sdus;
   };
   struct pop_callback {
-    explicit pop_callback(uint32_t& unread_bytes_) : unread_bytes(&unread_bytes_) {}
-    void      operator()(const unique_byte_buffer_t& msg) { *unread_bytes -= std::min(msg->N_bytes, *unread_bytes); }
+    explicit pop_callback(uint32_t& unread_bytes_, uint32_t& n_sdus_) : unread_bytes(&unread_bytes_), n_sdus(&n_sdus_)
+    {}
+    void operator()(const unique_byte_buffer_t& msg)
+    {
+      if (msg == nullptr) {
+        return;
+      }
+      *unread_bytes -= std::min(msg->N_bytes, *unread_bytes);
+      *n_sdus = std::max(0, (int32_t)(*n_sdus) - 1);
+    }
     uint32_t* unread_bytes;
+    uint32_t* n_sdus;
   };
 
   dyn_blocking_queue<unique_byte_buffer_t, push_callback, pop_callback> queue;
   uint32_t                                                              unread_bytes = 0;
+  uint32_t                                                              n_sdus       = 0;
 };
 
 } // namespace srsran

lib/src/upper/rlc_am_lte.cc

@@ -209,12 +209,9 @@ rlc_am_lte::rlc_am_lte_tx::rlc_am_lte_tx(rlc_am_lte* parent_) :
   pool(byte_buffer_pool::get_instance()),
   poll_retx_timer(parent_->timers->get_unique_timer()),
   status_prohibit_timer(parent_->timers->get_unique_timer())
-{
-}
+{}
 
-rlc_am_lte::rlc_am_lte_tx::~rlc_am_lte_tx()
-{
-}
+rlc_am_lte::rlc_am_lte_tx::~rlc_am_lte_tx() {}
 
 void rlc_am_lte::rlc_am_lte_tx::set_bsr_callback(bsr_callback_t callback)
 {
@@ -320,7 +317,7 @@ bool rlc_am_lte::rlc_am_lte_tx::has_data()
   return (((do_status() && not status_prohibit_timer.is_running())) || // if we have a status PDU to transmit
           (not retx_queue.empty()) ||                                  // if we have a retransmission
           (tx_sdu != NULL) ||                                          // if we are currently transmitting a SDU
-          (not tx_sdu_queue.is_empty())); // or if there is a SDU queued up for transmission
+          (tx_sdu_queue.get_n_sdus() != 0)); // or if there is a SDU queued up for transmission
 }
 
 /**
@@ -345,8 +342,8 @@ void rlc_am_lte::rlc_am_lte_tx::check_sn_reached_max_retx(uint32_t sn)
 uint32_t rlc_am_lte::rlc_am_lte_tx::get_buffer_state()
 {
   std::lock_guard<std::mutex> lock(mutex);
-  uint32_t n_bytes = 0;
-  uint32_t n_sdus  = 0;
+  uint32_t                    n_bytes = 0;
+  uint32_t                    n_sdus  = 0;
 
   logger.debug("%s Buffer state - do_status=%s, status_prohibit_running=%s (%d/%d)",
                RB_NAME,
@@ -384,7 +381,7 @@ uint32_t rlc_am_lte::rlc_am_lte_tx::get_buffer_state()
 
   // Bytes needed for tx SDUs
   if (tx_window.size() < 1024) {
-    n_sdus = tx_sdu_queue.size();
+    n_sdus = tx_sdu_queue.get_n_sdus();
     n_bytes += tx_sdu_queue.size_bytes();
     if (tx_sdu != NULL) {
       n_sdus++;
@@ -456,7 +453,21 @@ void rlc_am_lte::rlc_am_lte_tx::discard_sdu(uint32_t discard_sn)
   if (!tx_enabled) {
     return;
   }
-  logger.warning("Discard SDU not implemented yet");
+
+  bool discarded =
+      tx_sdu_queue.discard_if([&discard_sn](const unique_byte_buffer_t& sdu) { return sdu->md.pdcp_sn == discard_sn; });
+
+  if (discarded) {
+    // remove also from undelivered SDUs queue
+    logger.info("Discarding SDU with PDCP_SN=%d", discard_sn);
+    if (not undelivered_sdu_info_queue.has_pdcp_sn(discard_sn)) {
+      logger.info("PDCP SDU info does not exists for discarded SDU. PDCP_SN=%d", discard_sn);
+    } else {
+      undelivered_sdu_info_queue.clear_pdcp_sdu(discard_sn);
+    }
+  } else {
+    logger.info("Could not find SDU to discard. PDCP_SN=%d", discard_sn);
+  }
 }
 
 bool rlc_am_lte::rlc_am_lte_tx::sdu_queue_is_full()
@@ -966,7 +977,7 @@ int rlc_am_lte::rlc_am_lte_tx::build_data_pdu(uint8_t* payload, uint32_t nof_byt
   }
 
   // Pull SDUs from queue
-  while (pdu_space > head_len && tx_sdu_queue.size() > 0 && header.N_li < RLC_AM_WINDOW_SIZE) {
+  while (pdu_space > head_len && tx_sdu_queue.get_n_sdus() > 0 && header.N_li < RLC_AM_WINDOW_SIZE) {
     if (last_li > 0) {
       header.li[header.N_li] = last_li;
       header.N_li++;
@@ -978,7 +989,18 @@ int rlc_am_lte::rlc_am_lte_tx::build_data_pdu(uint8_t* payload, uint32_t nof_byt
       }
       break;
     }
-    tx_sdu  = tx_sdu_queue.read();
+
+    do {
+      tx_sdu = tx_sdu_queue.read();
+    } while (tx_sdu == nullptr && tx_sdu_queue.size() != 0);
+
+    if (tx_sdu == nullptr) {
+      if (header.N_li > 0) {
+        header.N_li--;
+      }
+      break;
+    }
+
     to_move = ((pdu_space - head_len) >= tx_sdu->N_bytes) ? tx_sdu->N_bytes : pdu_space - head_len;
     memcpy(pdu_ptr, tx_sdu->msg, to_move);
     last_li = to_move;
@@ -1045,7 +1067,7 @@ int rlc_am_lte::rlc_am_lte_tx::build_data_pdu(uint8_t* payload, uint32_t nof_byt
   }
 
   // Update Tx window
-  vt_s      = (vt_s + 1) % MOD;
+  vt_s = (vt_s + 1) % MOD;
 
   // Write final header and TX
   tx_pdu.buf                      = std::move(pdu);
@@ -1318,9 +1340,7 @@ rlc_am_lte::rlc_am_lte_rx::rlc_am_lte_rx(rlc_am_lte* parent_) :
   reordering_timer(parent_->timers->get_unique_timer())
 {}
 
-rlc_am_lte::rlc_am_lte_rx::~rlc_am_lte_rx()
-{
-}
+rlc_am_lte::rlc_am_lte_rx::~rlc_am_lte_rx() {}
 
 bool rlc_am_lte::rlc_am_lte_rx::configure(rlc_am_config_t cfg_)
 {
@@ -1752,8 +1772,8 @@ void rlc_am_lte::rlc_am_lte_rx::write_pdu(uint8_t* payload, const uint32_t nof_b
     parent->tx.handle_control_pdu(payload, nof_bytes);
   } else {
     std::lock_guard<std::mutex> lock(mutex);
-    rlc_amd_pdu_header_t header      = {};
-    uint32_t             payload_len = nof_bytes;
+    rlc_amd_pdu_header_t        header      = {};
+    uint32_t                    payload_len = nof_bytes;
     rlc_am_read_data_pdu_header(&payload, &payload_len, &header);
     if (payload_len > nof_bytes) {
       logger.info("Dropping corrupted PDU (%d B). Remaining length after header %d B.", nof_bytes, payload_len);
@@ -1858,9 +1878,9 @@ int rlc_am_lte::rlc_am_lte_rx::get_status_pdu(rlc_status_pdu_t* status, const ui
 int rlc_am_lte::rlc_am_lte_rx::get_status_pdu_length()
 {
   std::lock_guard<std::mutex> lock(mutex);
-  rlc_status_pdu_t status = {};
-  status.ack_sn           = vr_ms;
-  uint32_t i              = vr_r;
+  rlc_status_pdu_t            status = {};
+  status.ack_sn                      = vr_ms;
+  uint32_t i                         = vr_r;
   while (RX_MOD_BASE(i) < RX_MOD_BASE(vr_ms) && status.N_nack < RLC_AM_WINDOW_SIZE) {
     if (not rx_window.has_sn(i)) {
       status.N_nack++;

lib/test/upper/rlc_am_test.cc

@@ -3413,6 +3413,85 @@ bool reestablish_test()
   return SRSRAN_SUCCESS;
 }
 
+// This test checks the correct functioning of RLC discard functionality
+bool discard_test()
+{
+  const rlc_config_t config = rlc_config_t::default_rlc_am_config();
+#if HAVE_PCAP
+  rlc_pcap pcap;
+  pcap.open("rlc_am_reestablish_test.pcap", config);
+  rlc_am_tester tester(&pcap);
+#else
+  rlc_am_tester tester(NULL);
+#endif
+
+  srsran::timer_handler timers(8);
+
+  rlc_am_lte rlc1(srslog::fetch_basic_logger("RLC_AM_1"), 1, &tester, &tester, &timers);
+  rlc_am_lte rlc2(srslog::fetch_basic_logger("RLC_AM_2"), 1, &tester, &tester, &timers);
+
+  srslog::fetch_basic_logger("RLC_AM_1").set_hex_dump_max_size(100);
+  srslog::fetch_basic_logger("RLC_AM_2").set_hex_dump_max_size(100);
+  srslog::fetch_basic_logger("RLC").set_hex_dump_max_size(100);
+
+  if (not rlc1.configure(config)) {
+    return -1;
+  }
+
+  if (not rlc2.configure(config)) {
+    return -1;
+  }
+
+  // Check has_data() after a SDU discard
+  {
+    uint32_t num_tx_pdus = 1;
+    for (uint32_t i = 0; i < num_tx_pdus; ++i) {
+      // Write SDU
+      unique_byte_buffer_t sdu = srsran::make_byte_buffer();
+      TESTASSERT(sdu != nullptr);
+      sdu->N_bytes = 5;
+      for (uint32_t k = 0; k < sdu->N_bytes; ++k) {
+        sdu->msg[k] = i; // Write the index into the buffer
+      }
+      sdu->md.pdcp_sn = i;
+      rlc1.write_sdu(std::move(sdu));
+    }
+  }
+  rlc1.discard_sdu(0); // Try to discard PDCP_SN=1
+  TESTASSERT(rlc1.has_data() == false);
+
+  // Discard an SDU in the midle of the queue and read PDUs after
+  {
+    uint32_t num_tx_pdus = 10;
+    for (uint32_t i = 0; i < num_tx_pdus; ++i) {
+      // Write SDU
+      unique_byte_buffer_t sdu = srsran::make_byte_buffer();
+      TESTASSERT(sdu != nullptr);
+      sdu->N_bytes = 1;
+      for (uint32_t k = 0; k < sdu->N_bytes; ++k) {
+        sdu->msg[k] = i; // Write the index into the buffer
+      }
+      sdu->md.pdcp_sn = i;
+      rlc1.write_sdu(std::move(sdu));
+    }
+  }
+  rlc1.discard_sdu(3); // Try to discard PDCP_SN=1
+  TESTASSERT(rlc1.has_data() == true);
+  TESTASSERT(rlc1.get_buffer_state() == 23); // 2 bytes fixed header, 12 , 9 bytes of data,
+
+  unique_byte_buffer_t pdu = srsran::make_byte_buffer();
+  uint32_t             len = rlc1.read_pdu(pdu->msg, 50); // enough for all PDUs
+  pdu->N_bytes             = len;
+  TESTASSERT(23 == len);
+
+  srslog::fetch_basic_logger("TEST").info("Received %zd SDUs", tester.sdus.size());
+
+#if HAVE_PCAP
+  pcap.close();
+#endif
+
+  return SRSRAN_SUCCESS;
+}
 int main(int argc, char** argv)
 {
   // Setup the log message spy to intercept error and warning log entries from RLC
@@ -3603,5 +3682,10 @@ int main(int argc, char** argv)
     exit(-1);
   };
 
+  if (discard_test()) {
+    printf("discard_test failed\n");
+    exit(-1);
+  };
+
   return SRSRAN_SUCCESS;
 }