NFD

So basically this happens when node A tries to send an Interest it just received.
Is there any issue/documentation about removing straggling timer?
Would this still be an issue if per upstream suppression timer is implemented (4066).

#4200 would change Strategy::rejectPendingInterest to schedule the PIT entry for immediate deletion. Incorrect invocations in multicast and ASF strategies are harmful because they effectively drop the PIT entry and prevent Data from going to downstream. This must be resolved before #4200.

I am working on top of NFD commit 3cf75dc10be93d024a5ee125e22aef9a7ab25986 (i.e. before straggler timer, #4200).
I am unable to reproduce the scenario as described. The following unit test does not trigger the given log message.
Junxiao, are you able to reproduce using this commit? Could you elaborate on how the strategies have stopped working?

BOOST_AUTO_TEST_CASE(RejectPendingInterest)
{
  /*
  *      +---------+           +---------+            +----------+
  *      |  nodeA  |-----------|  nodeR  |------------|   nodeB  |
  *      +---------+    1ms    +---------+    1ms     +----------+
  */

  TopologyTester topo;
  TopologyNode nodeA = topo.addForwarder("A"),
               nodeR = topo.addForwarder("R"),
               nodeB = topo.addForwarder("B");

  for (TopologyNode node : {nodeA, nodeR, nodeB}) {
    topo.setStrategy<MulticastStrategy>(node);
    //topo.setStrategy<AsfStrategy>(node);
  }

  shared_ptr<TopologyLink> linkAR = topo.addLink("AR", time::milliseconds(1), {nodeA, nodeR}),
                           linkRB = topo.addLink("RB", time::milliseconds(1), {nodeR, nodeB});

  shared_ptr<TopologyAppLink> pingFromB = topo.addAppFace("cB", nodeB),
                              pingFromA = topo.addAppFace("cA", nodeB),
                              pingServer = topo.addAppFace("p", nodeA, Name("/A"));

  topo.registerPrefix(nodeR, linkAR->getFace(nodeR), Name("/A"), 1);
  topo.registerPrefix(nodeA, linkAR->getFace(nodeA), Name("/"), 1);
  topo.registerPrefix(nodeB, linkRB->getFace(nodeB), Name("/"), 1);

  shared_ptr<Interest> interest = makeInterest(Name("/A/1"));
  pingFromB->getClientFace().expressInterest(*interest, nullptr, nullptr, nullptr);

  this->advanceClocks(time::milliseconds(1), time::milliseconds(15));

  pingFromA->getClientFace().expressInterest(*interest, nullptr, nullptr, nullptr);

  this->advanceClocks(time::milliseconds(1), time::milliseconds(15));
}

I think this is because per upstream suppression is being used in multicast and ASF strategies (#note3).

Multicast strategy rejects pending interest when:

nEligibleNextHops == 0 && !isSuppressed

ASF strategy rejects pending interest when:

nexthops.size() == 0 or faceToUse == nullptr