1 files changed, 365 insertions, 0 deletions
diff --git a/libtransport/src/core/rs.cc b/libtransport/src/core/rs.cc
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+
+/*
+ * 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 <core/fec.h>
+#include <core/rs.h>
+#include <hicn/transport/core/global_object_pool.h>
+#include <hicn/transport/utils/log.h>
+
+#include <cassert>
+
+namespace transport {
+namespace core {
+namespace fec {
+
+BlockCode::BlockCode(uint32_t k, uint32_t n, struct fec_parms *code)
+    : Packets(),
+      k_(k),
+      n_(n),
+      code_(code),
+      max_buffer_size_(0),
+      current_block_size_(0),
+      to_decode_(false) {
+  sorted_index_.reserve(n);
+}
+
+bool BlockCode::addRepairSymbol(const fec::buffer &packet, uint32_t i) {
+  // Get index
+  to_decode_ = true;
+  TRANSPORT_LOGD("adding symbol of size %zu", packet->length());
+  return addSymbol(packet, i, packet->length() - sizeof(fec_header));
+}
+
+bool BlockCode::addSourceSymbol(const fec::buffer &packet, uint32_t i) {
+  return addSymbol(packet, i, packet->length());
+}
+
+bool BlockCode::addSymbol(const fec::buffer &packet, uint32_t i,
+                          std::size_t size) {
+  if (size > max_buffer_size_) {
+    max_buffer_size_ = size;
+  }
+
+  operator[](current_block_size_++) = std::make_pair(i, packet);
+
+  if (current_block_size_ >= k_) {
+    if (to_decode_) {
+      decode();
+    } else {
+      encode();
+    }
+
+    clear();
+    return false;
+  }
+
+  return true;
+}
+
+void BlockCode::encode() {
+  gf *data[n_];
+  std::uint16_t old_values[k_];
+  uint32_t base = operator[](0).first;
+
+  // Set packet length in first 2 bytes
+  for (uint32_t i = 0; i < k_; i++) {
+    auto &packet = operator[](i).second;
+
+    TRANSPORT_LOGD("Current buffer size: %zu", packet->length());
+
+    auto ret = packet->ensureCapacityAndFillUnused(max_buffer_size_, 0);
+    if (TRANSPORT_EXPECT_FALSE(ret == false)) {
+      throw errors::RuntimeException(
+          "Provided packet is not suitable to be used as FEC source packet. "
+          "Aborting.");
+    }
+
+    // Buffers should hold 2 bytes before the starting pointer, in order to be
+    // able to set the length for the encoding operation
+    packet->prepend(2);
+    uint16_t *length = reinterpret_cast<uint16_t *>(packet->writableData());
+
+    old_values[i] = *length;
+    *length = htons(packet->length() - LEN_SIZE_BYTES);
+
+    data[i] = packet->writableData();
+  }
+
+  // Finish to fill source block with the buffers to hold the repair symbols
+  for (uint32_t i = k_; i < n_; i++) {
+    // For the moment we get a packet from the pool here.. later we'll need to
+    // require a packet from the caller with a callback.
+    auto packet = PacketManager<>::getInstance().getMemBuf();
+    packet->append(max_buffer_size_ + sizeof(fec_header) + LEN_SIZE_BYTES);
+    fec_header *fh = reinterpret_cast<fec_header *>(packet->writableData());
+
+    fh->setSeqNumberBase(base);
+    fh->setNFecSymbols(n_ - k_);
+    fh->setEncodedSymbolId(i);
+    fh->setSourceBlockLen(n_);
+
+    packet->trimStart(sizeof(fec_header));
+
+    data[i] = packet->writableData();
+    operator[](i) = std::make_pair(i, std::move(packet));
+  }
+
+  // Generate repair symbols and put them in corresponding buffers
+  TRANSPORT_LOGD("Calling encode with max_buffer_size_ = %zu",
+                 max_buffer_size_);
+  for (uint32_t i = k_; i < n_; i++) {
+    fec_encode(code_, data, data[i], i, max_buffer_size_ + LEN_SIZE_BYTES);
+  }
+
+  // Restore original content of buffer space used to store the length
+  for (uint32_t i = 0; i < k_; i++) {
+    auto &packet = operator[](i).second;
+    uint16_t *length = reinterpret_cast<uint16_t *>(packet->writableData());
+    *length = old_values[i];
+    packet->trimStart(2);
+  }
+
+  // Re-include header in repair packets
+  for (uint32_t i = k_; i < n_; i++) {
+    auto &packet = operator[](i).second;
+    TRANSPORT_LOGD("Produced repair symbol of size = %zu", packet->length());
+    packet->prepend(sizeof(fec_header));
+  }
+}
+
+void BlockCode::decode() {
+  gf *data[k_];
+  uint32_t index[k_];
+
+  for (uint32_t i = 0; i < k_; i++) {
+    auto &packet = operator[](i).second;
+    index[i] = operator[](i).first;
+    sorted_index_[i] = index[i];
+
+    if (index[i] < k_) {
+      TRANSPORT_LOGD("DECODE SOURCE - index %u - Current buffer size: %zu",
+                     index[i], packet->length());
+      // This is a source packet. We need to prepend the length and fill
+      // additional space to 0
+
+      // Buffers should hold 2 bytes before the starting pointer, in order to be
+      // able to set the length for the encoding operation
+      packet->prepend(LEN_SIZE_BYTES);
+      packet->ensureCapacityAndFillUnused(max_buffer_size_, 0);
+      uint16_t *length = reinterpret_cast<uint16_t *>(packet->writableData());
+
+      *length = htons(packet->length() - LEN_SIZE_BYTES);
+    } else {
+      TRANSPORT_LOGD("DECODE SYMBOL - index %u - Current buffer size: %zu",
+                     index[i], packet->length());
+      packet->trimStart(sizeof(fec_header));
+    }
+
+    data[i] = packet->writableData();
+  }
+
+  // We decode the source block
+  TRANSPORT_LOGD("Calling decode with max_buffer_size_ = %zu",
+                 max_buffer_size_);
+  fec_decode(code_, data, reinterpret_cast<int *>(index), max_buffer_size_);
+
+  // Find the index in the block for recovered packets
+  for (uint32_t i = 0; i < k_; i++) {
+    if (index[i] != i) {
+      for (uint32_t j = 0; j < k_; j++)
+        if (sorted_index_[j] == uint32_t(index[i])) {
+          sorted_index_[j] = i;
+        }
+    }
+  }
+
+  // Reorder block by index with in-place sorting
+  for (uint32_t i = 0; i < k_; i++) {
+    for (uint32_t j = sorted_index_[i]; j != i; j = sorted_index_[i]) {
+      std::swap(sorted_index_[j], sorted_index_[i]);
+      std::swap(operator[](j), operator[](i));
+    }
+  }
+
+  // Adjust length according to the one written in the source packet
+  for (uint32_t i = 0; i < k_; i++) {
+    auto &packet = operator[](i).second;
+    uint16_t *length = reinterpret_cast<uint16_t *>(packet->writableData());
+    packet->trimStart(2);
+    packet->setLength(ntohs(*length));
+  }
+}
+
+void BlockCode::clear() {
+  current_block_size_ = 0;
+  max_buffer_size_ = 0;
+  sorted_index_.clear();
+  to_decode_ = false;
+}
+
+void rs::MatrixDeleter::operator()(struct fec_parms *params) {
+  fec_free(params);
+}
+
+rs::Codes rs::createCodes() {
+  Codes ret;
+
+  ret.emplace(std::make_pair(1, 3), Matrix(fec_new(1, 3), MatrixDeleter()));
+  ret.emplace(std::make_pair(6, 10), Matrix(fec_new(6, 10), MatrixDeleter()));
+  ret.emplace(std::make_pair(8, 32), Matrix(fec_new(8, 32), MatrixDeleter()));
+  ret.emplace(std::make_pair(10, 30), Matrix(fec_new(10, 30), MatrixDeleter()));
+  ret.emplace(std::make_pair(16, 24), Matrix(fec_new(16, 24), MatrixDeleter()));
+  ret.emplace(std::make_pair(10, 40), Matrix(fec_new(10, 40), MatrixDeleter()));
+  ret.emplace(std::make_pair(10, 60), Matrix(fec_new(10, 60), MatrixDeleter()));
+  ret.emplace(std::make_pair(10, 90), Matrix(fec_new(10, 90), MatrixDeleter()));
+
+  return ret;
+}
+
+rs::Codes rs::codes_ = createCodes();
+
+rs::rs(uint32_t k, uint32_t n) : k_(k), n_(n) {}
+
+void rs::setFECCallback(const PacketsReady &callback) {
+  fec_callback_ = callback;
+}
+
+encoder::encoder(uint32_t k, uint32_t n)
+    : rs(k, n),
+      current_code_(codes_[std::make_pair(k, n)].get()),
+      source_block_(k_, n_, current_code_) {}
+
+void encoder::consume(const fec::buffer &packet, uint32_t index) {
+  if (!source_block_.addSourceSymbol(packet, index)) {
+    std::vector<buffer> repair_packets;
+    for (uint32_t i = k_; i < n_; i++) {
+      repair_packets.emplace_back(std::move(source_block_[i].second));
+    }
+    fec_callback_(repair_packets);
+  }
+}
+
+decoder::decoder(uint32_t k, uint32_t n) : rs(k, n) {}
+
+void decoder::recoverPackets(SourceBlocks::iterator &src_block_it) {
+  TRANSPORT_LOGD("recoverPackets for %u", k_);
+  auto &src_block = src_block_it->second;
+  std::vector<buffer> source_packets(k_);
+  for (uint32_t i = 0; i < src_block.getK(); i++) {
+    source_packets[i] = std::move(src_block[i].second);
+  }
+
+  fec_callback_(source_packets);
+  processed_source_blocks_.emplace(src_block_it->first);
+
+  auto it = parked_packets_.find(src_block_it->first);
+  if (it != parked_packets_.end()) {
+    parked_packets_.erase(it);
+  }
+
+  src_blocks_.erase(src_block_it);
+}
+
+void decoder::consume(const fec::buffer &packet, uint32_t index) {
+  // Normalize index
+  auto i = index % n_;
+
+  // Get base
+  uint32_t base = index - i;
+
+  TRANSPORT_LOGD(
+      "Decoder consume called for source symbol. BASE = %u, index = %u and i = "
+      "%u",
+      base, index, i);
+
+  // check if a source block already exist for this symbol. If it does not
+  // exist, we lazily park this packet until we receive a repair symbol for the
+  // same block. This is done for 2 reason:
+  // 1) If we receive all the source packets of a block, we do not need to
+  //    recover anything.
+  // 2) Sender may change n and k at any moment, so we construct the source
+  //    block based on the (n, k) values written in the fec header. This is
+  //    actually not used right now, since we use fixed value of n and k passed
+  //    at construction time, but it paves the ground for a more dynamic
+  //    protocol that may come in the future.
+  auto it = src_blocks_.find(base);
+  if (it != src_blocks_.end()) {
+    auto ret = it->second.addSourceSymbol(packet, i);
+    if (!ret) {
+      recoverPackets(it);
+    }
+  } else {
+    TRANSPORT_LOGD("Adding to parked source packets");
+    auto ret = parked_packets_.emplace(
+        base, std::vector<std::pair<buffer, uint32_t> >());
+    ret.first->second.emplace_back(packet, i);
+  }
+}
+
+void decoder::consume(const fec::buffer &packet) {
+  // Repair symbol! Get index and base source block.
+  fec_header *h = reinterpret_cast<fec_header *>(packet->writableData());
+  auto i = h->getEncodedSymbolId();
+  auto base = h->getSeqNumberBase();
+  auto n = h->getSourceBlockLen();
+  auto k = n - h->getNFecSymbols();
+
+  TRANSPORT_LOGD(
+      "Decoder consume called for repair symbol. BASE = %u, index = %u and i = "
+      "%u",
+      base, base + i, i);
+
+  // check if a source block already exist for this symbol
+  auto it = src_blocks_.find(base);
+  if (it == src_blocks_.end()) {
+    // Create new source block
+    auto code_it = codes_.find(std::make_pair(k, n));
+    if (code_it == codes_.end()) {
+      TRANSPORT_LOGE("Code for k = %u and n = %u does not exist.", k_, n_);
+      return;
+    }
+
+    auto emplace_result =
+        src_blocks_.emplace(base, BlockCode(k, n, code_it->second.get()));
+    it = emplace_result.first;
+
+    // Check in the parked packets and insert any packet that is part of this
+    // source block
+
+    auto it2 = parked_packets_.find(base);
+    if (it2 != parked_packets_.end()) {
+      for (auto &packet_index : it2->second) {
+        auto ret =
+            it->second.addSourceSymbol(packet_index.first, packet_index.second);
+        if (!ret) {
+          recoverPackets(it);
+          // Finish to delete packets in same source block that were
+          // eventually not used
+          return;
+        }
+      }
+    }
+  }
+
+  auto ret = it->second.addRepairSymbol(packet, i);
+  if (!ret) {
+    recoverPackets(it);
+  }
+}
+
+}  // namespace fec
+}  // namespace core
+}  // namespace transport