evidence: dont send evidence to unsynced peers

* only send evidence to peers that are synced enough to validate it all
* closes #1624

evidence/reactor_test.go

@@ -14,6 +14,7 @@ import (
 	"github.com/tendermint/tmlibs/log"
 
 	cfg "github.com/tendermint/tendermint/config"
+	cstypes "github.com/tendermint/tendermint/consensus/types"
 	"github.com/tendermint/tendermint/p2p"
 	"github.com/tendermint/tendermint/types"
 )
@@ -130,8 +131,50 @@ func TestReactorBroadcastEvidence(t *testing.T) {
 	// make reactors from statedb
 	reactors := makeAndConnectEvidenceReactors(config, stateDBs)
 
+	// set the peer height on each reactor
+	for _, r := range reactors {
+		for _, peer := range r.Switch.Peers().List() {
+			ps := peerState{height}
+			peer.Set(types.PeerStateKey, ps)
+		}
+	}
+
 	// send a bunch of valid evidence to the first reactor's evpool
 	// and wait for them all to be received in the others
 	evList := sendEvidence(t, reactors[0].evpool, valAddr, NUM_EVIDENCE)
 	waitForEvidence(t, evList, reactors)
 }
+
+type peerState struct {
+	height int64
+}
+
+func (ps peerState) GetRoundState() *cstypes.PeerRoundState {
+	return &cstypes.PeerRoundState{
+		Height: ps.height,
+	}
+}
+
+func TestReactorSelectiveBroadcast(t *testing.T) {
+	config := cfg.TestConfig()
+
+	valAddr := []byte("myval")
+	height1 := int64(NUM_EVIDENCE) + 10
+	height2 := int64(NUM_EVIDENCE) / 2
+
+	// DB1 is ahead of DB2
+	stateDB1 := initializeValidatorState(valAddr, height1)
+	stateDB2 := initializeValidatorState(valAddr, height2)
+
+	// make reactors from statedb
+	reactors := makeAndConnectEvidenceReactors(config, []dbm.DB{stateDB1, stateDB2})
+	peer := reactors[0].Switch.Peers().List()[0]
+	ps := peerState{height2}
+	peer.Set(types.PeerStateKey, ps)
+
+	// send a bunch of valid evidence to the first reactor's evpool
+	evList := sendEvidence(t, reactors[0].evpool, valAddr, NUM_EVIDENCE)
+
+	// only ones less than the peers height should make it through
+	waitForEvidence(t, evList[:NUM_EVIDENCE/2], reactors[1:2])
+}