NFD » ndn-cxx

Snippet to reproduce:

// g++ -o x -std=c++0x x.cpp $(pkg-config --cflags --libs libndn-cxx)
#include <ndn-cxx/security/key-chain.hpp>
#include <ndn-cxx/security/signing-helpers.hpp>
#include <ndn-cxx/security/validator-null.hpp>
#include <ndn-cxx/util/dummy-client-face.hpp>
#include <ndn-cxx/util/segment-fetcher.hpp>

namespace ndn {
namespace demo {

using util::DummyClientFace;
using util::SegmentFetcher;

KeyChain g_keyChain;

shared_ptr<Data>
makeData(const Name& name, bool isFinalBlock = false)
{
  auto data = make_shared<Data>(name);
  if (isFinalBlock) {
    data->setMetaInfo(MetaInfo().setFinalBlockId(name.at(-1)));
  }
  g_keyChain.sign(*data, ndn::signingWithSha256());
  return data;
}

int
main(int argc, char** argv)
{
  DummyClientFace face;
  int nNacks = 2;
  face.onSendInterest.connect([&] (const Interest& interest) {
    std::cout << interest << std::endl;
    const Name& name = interest.getName();
    if (!name.at(-1).isSegment()) {
      auto data0 = makeData(Name(name).appendVersion().appendSegment(0));
      face.getIoService().post([&face, data0] { face.receive(*data0); });
      return;
    }
    uint64_t segmentNo = name.at(-1).toSegment();
    if (segmentNo == 1 && nNacks-- > 0) {
      lp::Nack nack(interest);
      nack.setReason(lp::NackReason::DUPLICATE);
      face.getIoService().post([&face, nack] { face.receive(nack); });
      return;
    }
    auto data1 = makeData(name, segmentNo == 3);
    face.getIoService().post([&face, data1] { face.receive(*data1); });
  });

  SegmentFetcher::fetch(face,
                        Interest("ndn:/A"),
                        make_shared<ValidatorNull>(),
                        bind([] { std::cout << "COMPLETE" << std::endl; }),
                        bind([] { std::cout << "ERROR" << std::endl; }));
  face.processEvents();
  return 0;
}

} // namespace demo
} // namespace ndn

int
main(int argc, char** argv)
{
  return ndn::demo::main(argc, argv);
}

This snippet uses SegmentFetcher to fetch 4 segments.
The first and second Interests for segment1 would be responded with Nack-Duplicate.
All other responses are Data.

Expected: SegmentFetcher retrieves segment2 after receiving Data for segment1.

Actual: SegmentFetcher discards segment2 Data and restarts from segment0.

/A?ndn.ChildSelector=1&ndn.MustBeFresh=1&ndn.Nonce=369644762
/A/%FD%00%00%01Sz%F6%FC%1E/%00%01?ndn.ChildSelector=0&ndn.Nonce=509290956
/A/%FD%00%00%01Sz%F6%FC%1E/%00%01?ndn.ChildSelector=0&ndn.Nonce=944403614
/A/%FD%00%00%01Sz%F6%FC%1E/%00%01?ndn.ChildSelector=0&ndn.Nonce=1709422619
/A/%FD%00%00%01Sz%F6%FC%1E/%00%00?ndn.ChildSelector=0&ndn.Nonce=3626967908
/A/%FD%00%00%01Sz%F6%FC%1E/%00%01?ndn.ChildSelector=0&ndn.Nonce=2208639054
/A/%FD%00%00%01Sz%F6%FC%1E/%00%02?ndn.ChildSelector=0&ndn.Nonce=765477500
/A/%FD%00%00%01Sz%F6%FC%1E/%00%03?ndn.ChildSelector=0&ndn.Nonce=84957429
COMPLETE

Root cause: in SegmentFetcher::reExpressInterest, afterSegmentReceived is always called with isSegmentZeroExpected=true.