face: NDNLPv2 fragmentation and reassembly
refs #3171
Change-Id: If29035b697b904ee49cb86d9248be488657c6f9e
diff --git a/daemon/face/lp-fragmenter.cpp b/daemon/face/lp-fragmenter.cpp
new file mode 100644
index 0000000..b54f7d5
--- /dev/null
+++ b/daemon/face/lp-fragmenter.cpp
@@ -0,0 +1,162 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2014-2015, Regents of the University of California,
+ * Arizona Board of Regents,
+ * Colorado State University,
+ * University Pierre & Marie Curie, Sorbonne University,
+ * Washington University in St. Louis,
+ * Beijing Institute of Technology,
+ * The University of Memphis.
+ *
+ * This file is part of NFD (Named Data Networking Forwarding Daemon).
+ * See AUTHORS.md for complete list of NFD authors and contributors.
+ *
+ * NFD is free software: you can redistribute it and/or modify it under the terms
+ * of the GNU General Public License as published by the Free Software Foundation,
+ * either version 3 of the License, or (at your option) any later version.
+ *
+ * NFD 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * NFD, e.g., in COPYING.md file. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "lp-fragmenter.hpp"
+#include "link-service.hpp"
+#include <ndn-cxx/encoding/tlv.hpp>
+
+namespace nfd {
+namespace face {
+
+NFD_LOG_INIT("LpFragmenter");
+
+static_assert(lp::tlv::LpPacket < 253, "LpPacket TLV-TYPE must fit in 1 octet");
+static_assert(lp::tlv::Sequence < 253, "Sequence TLV-TYPE must fit in 1 octet");
+static_assert(lp::tlv::FragIndex < 253, "FragIndex TLV-TYPE must fit in 1 octet");
+static_assert(lp::tlv::FragCount < 253, "FragCount TLV-TYPE must fit in 1 octet");
+static_assert(lp::tlv::Fragment < 253, "Fragment TLV-TYPE must fit in 1 octet");
+
+/** \brief maximum overhead on a single fragment,
+ * not counting other NDNLPv2 headers
+ */
+static const size_t MAX_SINGLE_FRAG_OVERHEAD =
+ 1 + 9 + // LpPacket TLV-TYPE and TLV-LENGTH
+ 1 + 1 + 8 + // Sequence TLV
+ 1 + 9; // Fragment TLV-TYPE and TLV-LENGTH
+
+/** \brief maximum overhead of adding fragmentation to payload,
+ * not counting other NDNLPv2 headers
+ */
+static const size_t MAX_FRAG_OVERHEAD =
+ 1 + 9 + // LpPacket TLV-TYPE and TLV-LENGTH
+ 1 + 1 + 8 + // Sequence TLV
+ 1 + 1 + 8 + // FragIndex TLV
+ 1 + 1 + 8 + // FragCount TLV
+ 1 + 9; // Fragment TLV-TYPE and TLV-LENGTH
+
+LpFragmenter::Options::Options()
+ : nMaxFragments(400)
+{
+}
+
+LpFragmenter::LpFragmenter(const LpFragmenter::Options& options, const LinkService* linkService)
+ : m_options(options)
+ , m_linkService(linkService)
+{
+}
+
+void
+LpFragmenter::setOptions(const Options& options)
+{
+ m_options = options;
+}
+
+const LinkService*
+LpFragmenter::getLinkService() const
+{
+ return m_linkService;
+}
+
+std::tuple<bool, std::vector<lp::Packet>>
+LpFragmenter::fragmentPacket(const lp::Packet& packet, size_t mtu)
+{
+ BOOST_ASSERT(packet.has<lp::FragmentField>());
+ BOOST_ASSERT(!packet.has<lp::FragIndexField>());
+ BOOST_ASSERT(!packet.has<lp::FragCountField>());
+
+ if (MAX_SINGLE_FRAG_OVERHEAD + packet.wireEncode().size() <= mtu) {
+ // fast path: fragmentation not needed
+ // To qualify for fast path, the packet must have space for adding a sequence number,
+ // because another NDNLPv2 feature may require the sequence number.
+ return std::make_tuple(true, std::vector<lp::Packet>{packet});
+ }
+
+ ndn::Buffer::const_iterator netPktBegin, netPktEnd;
+ std::tie(netPktBegin, netPktEnd) = packet.get<lp::FragmentField>();
+ size_t netPktSize = std::distance(netPktBegin, netPktEnd);
+
+ // compute size of other NDNLPv2 headers to be placed on the first fragment
+ size_t firstHeaderSize = 0;
+ const Block& packetWire = packet.wireEncode();
+ if (packetWire.type() == lp::tlv::LpPacket) {
+ for (const Block& element : packetWire.elements()) {
+ if (element.type() != lp::tlv::Fragment) {
+ firstHeaderSize += element.size();
+ }
+ }
+ }
+
+ // compute payload size
+ if (MAX_FRAG_OVERHEAD + firstHeaderSize + 1 > mtu) { // 1-octet fragment
+ NFD_LOG_FACE_WARN("fragmentation error, MTU too small for first fragment: DROP");
+ return std::make_tuple(false, std::vector<lp::Packet>{});
+ }
+ size_t firstPayloadSize = std::min(netPktSize, mtu - firstHeaderSize - MAX_FRAG_OVERHEAD);
+ size_t payloadSize = mtu - MAX_FRAG_OVERHEAD;
+ size_t fragCount = 1 + ((netPktSize - firstPayloadSize) / payloadSize) +
+ ((netPktSize - firstPayloadSize) % payloadSize != 0);
+
+ // compute FragCount
+ if (fragCount > m_options.nMaxFragments) {
+ NFD_LOG_FACE_WARN("fragmentation error, FragCount over limit: DROP");
+ return std::make_pair(false, std::vector<lp::Packet>{});
+ }
+
+ // populate fragments
+ std::vector<lp::Packet> frags(fragCount);
+ frags.front() = packet; // copy input packet to preserve other NDNLPv2 fields
+ size_t fragIndex = 0;
+ auto fragBegin = netPktBegin,
+ fragEnd = fragBegin + firstPayloadSize;
+ while (fragBegin < netPktEnd) {
+ lp::Packet& frag = frags[fragIndex];
+ frag.add<lp::FragIndexField>(fragIndex);
+ frag.add<lp::FragCountField>(fragCount);
+ frag.set<lp::FragmentField>(std::make_pair(fragBegin, fragEnd));
+ BOOST_ASSERT(frag.wireEncode().size() <= mtu);
+
+ ++fragIndex;
+ fragBegin = fragEnd;
+ fragEnd = std::min(netPktEnd, fragBegin + payloadSize);
+ }
+ BOOST_ASSERT(fragIndex == fragCount);
+
+ return std::make_pair(true, frags);
+}
+
+std::ostream&
+operator<<(std::ostream& os, const FaceLogHelper<LpFragmenter>& flh)
+{
+ if (flh.obj.getLinkService() == nullptr) {
+ os << "[id=0,local=unknown,remote=unknown] ";
+ }
+ else {
+ os << FaceLogHelper<LinkService>(*flh.obj.getLinkService());
+ }
+ return os;
+}
+
+} // namespace face
+} // namespace nfd