fix filter for next round period 0 votes

agreement/voteAggregator.go

@@ -221,7 +221,8 @@ func (agg *voteAggregator) filterBundle(ub unauthenticatedBundle, freshData fres
 
 // voteStepFresh is a helper function for vote relay rules.  Votes from steps
 // [soft, next] are always propagated, as are votes from [s-1, s+1] where s is
-// the current/last concluding step.
+// the current/last concluding step. Set mine to 0 to effectively disable allowing
+// votes adjacent to the current/last concluding step.
 func voteStepFresh(descr string, proto protocol.ConsensusVersion, mine, vote step) error {
 	if vote <= next {
 		// always propagate first recovery vote to ensure synchronous block of periods after partition
@@ -248,8 +249,12 @@ func voteFresh(proto protocol.ConsensusVersion, freshData freshnessData, vote un
 		return fmt.Errorf("filtered vote from bad round: player.Round=%v; vote.Round=%v", freshData.PlayerRound, vote.R.Round)
 	}
 
-	if freshData.PlayerRound+1 == vote.R.Round && (vote.R.Period > 0 || vote.R.Step > next) {
-		return fmt.Errorf("filtered future vote from bad period or step: player.Round=%v; vote.(Round,Period,Step)=(%v,%v,%v)", freshData.PlayerRound, vote.R.Round, vote.R.Period, vote.R.Step)
+	if freshData.PlayerRound+1 == vote.R.Round {
+		if (vote.R.Period > 0) {
+			return fmt.Errorf("filtered future vote from bad period: player.Round=%v; vote.(Round,Period,Step)=(%v,%v,%v)", freshData.PlayerRound, vote.R.Round, vote.R.Period, vote.R.Step)
+		}
+		// pipeline votes from next round period 0
+		return voteStepFresh("from next round", proto, 0, vote.R.Step)
 	}
 
 	switch vote.R.Period {

agreement/voteAggregator_test.go

@@ -777,3 +777,65 @@ func TestVoteAggregatorFiltersVotePresentPeriod(t *testing.T) {
 	require.NoError(t, err)
 	require.NoErrorf(t, res, "VotePresent not correctly filtered")
 }
+
+func TestVoteAggregatorFiltersVoteNextRound(t *testing.T) {
+	// Set up a composed test machine
+	rRouter := new(rootRouter)
+	rRouter.update(player{}, 0, false)
+	voteM := &ioAutomataConcrete{
+		listener:  rRouter.voteRoot,
+		routerCtx: rRouter,
+	}
+	helper := voteMakerHelper{}
+	helper.Setup()
+	b := testCaseBuilder{}
+
+	// define a current player state for freshness testing
+	lastConcludingStep := next
+	msgTemplate := filterableMessageEvent{
+		FreshnessData: freshnessData{
+			PlayerRound:          round(10),
+			PlayerPeriod:         period(10),
+			PlayerStep:           next + 5,
+			PlayerLastConcluding: lastConcludingStep,
+		},
+	}
+	// generate old next vote in next round, period 0, step 1; make sure it is accepted
+	pV := helper.MakeRandomProposalValue()
+	uv := helper.MakeUnauthenticatedVote(t, 0, round(11), period(0), soft, *pV)
+	inMsg := msgTemplate // copy
+	inMsg.messageEvent = messageEvent{
+		T: votePresent,
+		Input: message{
+			UnauthenticatedVote: uv,
+		},
+	}
+	b.AddInOutPair(inMsg, emptyEvent{})
+
+	// next round, period 0, step > next should be rejected
+	uv = helper.MakeUnauthenticatedVote(t, 1, round(11), period(0), next+1, *pV)
+	inMsg = msgTemplate // copy
+	inMsg.messageEvent = messageEvent{
+		T: votePresent,
+		Input: message{
+			UnauthenticatedVote: uv,
+		},
+	}
+	b.AddInOutPair(inMsg, filteredEvent{T: voteFiltered})
+
+	// next round, period 1 should be rejected
+	uv = helper.MakeUnauthenticatedVote(t, 1, round(11), period(1), soft, *pV)
+	inMsg = msgTemplate // copy
+	inMsg.messageEvent = messageEvent{
+		T: votePresent,
+		Input: message{
+			UnauthenticatedVote: uv,
+		},
+	}
+	b.AddInOutPair(inMsg, filteredEvent{T: voteFiltered})
+
+	// finalize
+	res, err := b.Build().Validate(voteM)
+	require.NoError(t, err)
+	require.NoErrorf(t, res, "Votes from next round not correctly filtered")
+}