1 files changed, 147 insertions, 0 deletions
diff --git a/libtransport/src/protocols/rtc/rtc_rs_delay.cc b/libtransport/src/protocols/rtc/rtc_rs_delay.cc
new file mode 100644
index 000000000..7d7a01133
--- /dev/null
+++ b/libtransport/src/protocols/rtc/rtc_rs_delay.cc
@@ -0,0 +1,147 @@
+/*
+ * Copyright (c) 2021 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <glog/logging.h>
+#include <protocols/rtc/rtc_consts.h>
+#include <protocols/rtc/rtc_rs_delay.h>
+
+namespace transport {
+
+namespace protocol {
+
+namespace rtc {
+
+RecoveryStrategyDelayBased::RecoveryStrategyDelayBased(
+    Indexer *indexer, SendRtxCallback &&callback, asio::io_service &io_service,
+    interface::RtcTransportRecoveryStrategies rs_type,
+    interface::StrategyCallback &&external_callback)
+    : RecoveryStrategy(indexer, std::move(callback), io_service, true, false,
+                       rs_type,
+                       std::move(external_callback)),  // start with rtx
+      congestion_state_(false),
+      probing_state_(false),
+      switch_rounds_(0) {}
+
+RecoveryStrategyDelayBased::RecoveryStrategyDelayBased(RecoveryStrategy &&rs)
+    : RecoveryStrategy(std::move(rs)) {
+  setRtxFec(true, false);
+  // we have to re-init congestion and
+  // probing
+  switch_rounds_ = 0;
+  congestion_state_ = false;
+  probing_state_ = false;
+}
+
+RecoveryStrategyDelayBased::~RecoveryStrategyDelayBased() {}
+
+void RecoveryStrategyDelayBased::turnOnRecovery() {
+  recovery_on_ = true;
+  uint64_t rtt = state_->getMinRTT();
+  uint32_t fec_to_ask = computeFecPacketsToAsk();
+  if (rtt > MAX_RTT_BEFORE_FEC && fec_to_ask > 0) {
+    // we need to start FEC (see fec only strategy for more details)
+    setRtxFec(true, true);
+    rtx_during_fec_ = 1;  // avoid to stop fec
+    indexer_->setNFec(fec_to_ask);
+  } else {
+    // use RTX
+    setRtxFec(true, false);
+    switch_rounds_ = 0;
+  }
+}
+
+void RecoveryStrategyDelayBased::softSwitchToFec(uint32_t fec_to_ask) {
+  if (fec_to_ask == 0) {
+    setRtxFec(true, false);
+    switch_rounds_ = 0;
+  } else {
+    switch_rounds_++;
+    if (switch_rounds_ >= ((RTC_INTEREST_LIFETIME / ROUND_LEN) * 2) &&
+        rtx_during_fec_ != 0) {  // go to fec only if it is needed (RTX are on)
+      setRtxFec(false, true);
+    } else {
+      setRtxFec(true, true);
+    }
+  }
+}
+
+void RecoveryStrategyDelayBased::onNewRound(bool in_sync) {
+  if (!recovery_on_) {
+    // disable fec so that no extra packet will be sent
+    // for rtx we check if recovery is on in newPacketLoss
+    setRtxFec(true, false);
+    indexer_->setNFec(0);
+    return;
+  }
+
+  uint64_t rtt = state_->getAvgRTT();
+
+  // XXX at the moment we are not looking at congestion events
+  // bool congestion = rc_->inCongestionState();
+
+  if ((!fec_on_ && rtt >= MAX_RTT_BEFORE_FEC) ||
+      (fec_on_ && rtt > (MAX_RTT_BEFORE_FEC - 10))) {
+    // switch from rtx to fec or keep use fec. Notice that if some rtx are
+    // waiting to be scheduled, they will be sent normally, but no new rtx will
+    // be created if the loss rate is 0 keep to use RTX.
+    uint32_t fec_to_ask = computeFecPacketsToAsk();
+    softSwitchToFec(fec_to_ask);
+    if (rtx_during_fec_ == 0)  // if we do not send any RTX the losses
+                               // registered may be due to jitter
+      indexer_->setNFec(0);
+    else
+      indexer_->setNFec(fec_to_ask);
+    return;
+  }
+
+  if ((fec_on_ && rtt <= (MAX_RTT_BEFORE_FEC - 10)) ||
+      (!rtx_on_ && rtt <= MAX_RTT_BEFORE_FEC)) {
+    // turn on rtx
+    softSwitchToFec(0);
+    indexer_->setNFec(0);
+    return;
+  }
+}
+
+void RecoveryStrategyDelayBased::newPacketLoss(uint32_t seq) {
+  if (rtx_on_ && recovery_on_) {
+    addNewRtx(seq, false);
+  } else {
+    if (!state_->isPending(seq) && !indexer_->isFec(seq)) {
+      addNewRtx(seq, true);
+    } else {
+      recover_with_fec_.insert(seq);
+      state_->onPossibleLossWithNoRtx(seq);
+    }
+  }
+}
+
+void RecoveryStrategyDelayBased::receivedPacket(uint32_t seq) {
+  removePacketState(seq);
+}
+
+void RecoveryStrategyDelayBased::probing() {
+  // TODO
+  // for the moment ask for all fec and exit the probing phase
+  probing_state_ = false;
+  setRtxFec(false, true);
+  indexer_->setNFec(computeFecPacketsToAsk());
+}
+
+}  // end namespace rtc
+
+}  // end namespace protocol
+
+}  // end namespace transport