Fix consensus:

* Use LastValidators when a Vote is received for the last height.
* Fix Validation.Height/Round to use FirstPrecommit.

consensus/reactor.go

@@ -177,18 +177,20 @@ func (conR *ConsensusReactor) Receive(chId byte, peer *p2p.Peer, msgBytes []byte
 		switch msg := msg_.(type) {
 		case *VoteMessage:
 			vote := msg.Vote
-			var validators *ValidatorSet
+			var validators *sm.ValidatorSet
 			if rs.Height == vote.Height {
 				validators = rs.Validators
 			} else if rs.Height == vote.Height+1 {
-				validators = rs.LastBondedValidators
 				if !(rs.Step == RoundStepNewHeight && vote.Type == types.VoteTypePrecommit) {
 					return // Wrong height, not a LastCommit straggler commit.
 				}
+				validators = rs.LastValidators
 			} else {
 				return // Wrong height. Not necessarily a bad peer.
 			}
-		VOTE_PASS:
+
+			// We have vote/validators.  Height may not be rs.Height
+
 			address, _ := validators.GetByIndex(msg.ValidatorIndex)
 			added, index, err := conR.conS.AddVote(address, vote, peer.Key)
 			if err != nil {

consensus/state.go

@@ -215,6 +215,7 @@ type RoundState struct {
 	LockedBlockParts   *types.PartSet
 	Votes              *HeightVoteSet
 	LastCommit         *VoteSet // Last precommits at Height-1
+	LastValidators     *sm.ValidatorSet
 }
 
 func (rs *RoundState) String() string {
@@ -233,6 +234,7 @@ func (rs *RoundState) StringIndented(indent string) string {
 %s  LockedBlock:   %v %v
 %s  Votes:         %v
 %s  LastCommit: %v
+%s  LastValidators:    %v
 %s}`,
 		indent, rs.Height, rs.Round, rs.Step,
 		indent, rs.StartTime,
@@ -244,6 +246,7 @@ func (rs *RoundState) StringIndented(indent string) string {
 		indent, rs.LockedBlockParts.StringShort(), rs.LockedBlock.StringShort(),
 		indent, rs.Votes.StringIndented(indent+"    "),
 		indent, rs.LastCommit.StringShort(),
+		indent, rs.LastValidators.StringIndented(indent+"    "),
 		indent)
 }
 
@@ -406,6 +409,7 @@ func (cs *ConsensusState) updateToState(state *sm.State, contiguous bool) {
 	cs.LockedBlockParts = nil
 	cs.Votes = NewHeightVoteSet(height, validators)
 	cs.LastCommit = lastPrecommits
+	cs.LastValidators = state.LastBondedValidators
 
 	cs.state = state
 	cs.stagedBlock = nil

types/block.go

@@ -184,22 +184,39 @@ type Validation struct {
 	Precommits []*Vote `json:"precommits"`
 
 	// Volatile
-	hash     []byte
-	bitArray *BitArray
+	firstPrecommit *Vote
+	hash           []byte
+	bitArray       *BitArray
+}
+
+func (v *Validation) FirstPrecommit() *Vote {
+	if len(v.Precommits) == 0 {
+		return nil
+	}
+	if v.firstPrecommit != nil {
+		return v.firstPrecommit
+	}
+	for _, precommit := range v.Precommits {
+		if precommit != nil {
+			v.firstPrecommit = precommit
+			return precommit
+		}
+	}
+	return nil
 }
 
 func (v *Validation) Height() int {
 	if len(v.Precommits) == 0 {
 		return 0
 	}
-	return v.Precommits[0].Height
+	return v.FirstPrecommit().Height
 }
 
 func (v *Validation) Round() int {
 	if len(v.Precommits) == 0 {
 		return 0
 	}
-	return v.Precommits[0].Round
+	return v.FirstPrecommit().Round
 }
 
 func (v *Validation) ValidateBasic() error {