1 files changed, 143 insertions, 0 deletions
diff --git a/libtransport/src/protocols/rtc/rtc_rs_fec_only.cc b/libtransport/src/protocols/rtc/rtc_rs_fec_only.cc
new file mode 100644
index 000000000..5b10823ec
--- /dev/null
+++ b/libtransport/src/protocols/rtc/rtc_rs_fec_only.cc
@@ -0,0 +1,143 @@
+/*
+ * 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_fec_only.h>
+
+namespace transport {
+
+namespace protocol {
+
+namespace rtc {
+
+RecoveryStrategyFecOnly::RecoveryStrategyFecOnly(
+    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)),
+      congestion_state_(false),
+      probing_state_(false),
+      switch_rounds_(0) {}
+
+RecoveryStrategyFecOnly::RecoveryStrategyFecOnly(RecoveryStrategy &&rs)
+    : RecoveryStrategy(std::move(rs)) {
+  setRtxFec(true, false);
+  switch_rounds_ = 0;
+  congestion_state_ = false;
+  probing_state_ = false;
+}
+
+RecoveryStrategyFecOnly::~RecoveryStrategyFecOnly() {}
+
+void RecoveryStrategyFecOnly::turnOnRecovery() {
+  recovery_on_ = true;
+  // init strategy
+  uint32_t fec_to_ask = computeFecPacketsToAsk();
+  if (fec_to_ask > 0) {
+    // the probing phase detected a lossy link. we immedialty start the fec and
+    // we disable the check to prevent to send fec packets before RTX. in fact
+    // here we know that we have losses and it is not a problem of OOO packets
+    setRtxFec(true, true);
+    rtx_during_fec_ = 1;  // avoid to stop fec
+    indexer_->setNFec(fec_to_ask);
+  } else {
+    // keep only RTX on
+    setRtxFec(true, true);
+  }
+}
+
+void RecoveryStrategyFecOnly::onNewRound(bool in_sync) {
+  if (!recovery_on_) {
+    indexer_->setNFec(0);
+    return;
+  }
+
+  // XXX for the moment we are considering congestion events
+  // if(rc_->inCongestionState()){
+  //   congestion_state_ = true;
+  //   probing_state_ = false;
+  //   indexer_->setNFec(0);
+  //   return;
+  // }
+
+  // no congestion
+  if (congestion_state_) {
+    // this is the first round after congestion
+    // enter probing phase
+    probing_state_ = true;
+    congestion_state_ = false;
+  }
+
+  if (probing_state_) {
+    probing();
+  } else {
+    uint32_t fec_to_ask = computeFecPacketsToAsk();
+    // If fec_to_ask == 0 we use rtx even if in these strategy we use only fec.
+    // In this way the first packet loss that triggers the usage of fec can be
+    // recovered using rtx, otherwise it will always be lost
+    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);  // keep both
+      }
+    }
+    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);
+  }
+}
+
+void RecoveryStrategyFecOnly::newPacketLoss(uint32_t seq) {
+  if (rtx_on_ && recovery_on_) {
+    addNewRtx(seq, false);
+  } else {
+    if (!state_->isPending(seq) && !indexer_->isFec(seq)) {
+      addNewRtx(seq, true);
+    } else {
+      // if not pending add to list to recover with fec
+      recover_with_fec_.insert(seq);
+      state_->onPossibleLossWithNoRtx(seq);
+    }
+  }
+}
+
+void RecoveryStrategyFecOnly::receivedPacket(uint32_t seq) {
+  removePacketState(seq);
+}
+
+void RecoveryStrategyFecOnly::probing() {
+  // TODO
+  // for the moment ask for all fec and exit the probing phase
+  probing_state_ = false;
+  uint32_t fec_to_ask = computeFecPacketsToAsk();
+  indexer_->setNFec(fec_to_ask);
+}
+
+}  // end namespace rtc
+
+}  // end namespace protocol
+
+}  // end namespace transport