Fix consensus: use the right ValidatorSet upon Vote receive

consensus/reactor.go

@@ -177,16 +177,19 @@ func (conR *ConsensusReactor) Receive(chId byte, peer *p2p.Peer, msgBytes []byte
 		switch msg := msg_.(type) {
 		case *VoteMessage:
 			vote := msg.Vote
-			if rs.Height != vote.Height {
-				if rs.Height == vote.Height+1 {
-					if rs.Step == RoundStepNewHeight && vote.Type == types.VoteTypePrecommit {
-						goto VOTE_PASS // *ducks*
-					}
+			var validators *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.
 				}
+			} else {
 				return // Wrong height. Not necessarily a bad peer.
 			}
 		VOTE_PASS:
-			address, _ := rs.Validators.GetByIndex(msg.ValidatorIndex)
+			address, _ := validators.GetByIndex(msg.ValidatorIndex)
 			added, index, err := conR.conS.AddVote(address, vote, peer.Key)
 			if err != nil {
 				// If conflicting sig, broadcast evidence tx for slashing. Else punish peer.