Send keyper config index as part of EonStartVote

This replaces the use of the activation block number as part of the message. In
the app we still use the activation block number, but could probably also get
rid of it, since we just use the value from the keyper/batch config.

rolling-shutter/app/app.go

@@ -113,14 +113,14 @@ func LoadShutterAppFromFile(gobpath string) (ShutterApp, error) {
 	return shapp, nil
 }
 
-// getConfig returns the BatchConfig for the given mainchain block number.
-func (app *ShutterApp) getConfig(blockNumber uint64) *BatchConfig {
-	for i := len(app.Configs) - 1; i >= 0; i-- {
-		if app.Configs[i].ActivationBlockNumber <= blockNumber {
-			return app.Configs[i]
+// getConfigByKeyperConfigIndex returns the BatchConfig with the given keyperConfigIndex.
+func (app *ShutterApp) getConfigByKeyperConfigIndex(keyperConfigIndex uint64) (*BatchConfig, bool) {
+	for _, cfg := range app.Configs {
+		if cfg.KeyperConfigIndex == keyperConfigIndex {
+			return cfg, true
 		}
 	}
-	panic("guard element missing")
+	return nil, false
 }
 
 // checkConfig checks if the given BatchConfig could be added.
@@ -431,12 +431,16 @@ func (app *ShutterApp) deliverBlockSeen(
 }
 
 func (app *ShutterApp) deliverEonStartVoteMsg(msg *shmsg.EonStartVote, sender common.Address) abcitypes.ResponseDeliverTx {
-	config := app.getConfig(msg.ActivationBlockNumber)
+	config, ok := app.getConfigByKeyperConfigIndex(msg.KeyperConfigIndex)
+	if !ok {
+		return makeErrorResponse(fmt.Sprintf(
+			"config with keyper config index %d not found", msg.KeyperConfigIndex))
+	}
 	if !config.IsKeyper(sender) {
 		return notAKeyper(sender)
 	}
 
-	app.countEonStartVote(sender, config, msg.ActivationBlockNumber)
+	app.countEonStartVote(sender, config, config.ActivationBlockNumber)
 	dkg, activationBlockNumber, started := app.maybeStartEon(config)
 	if !started {
 		return abcitypes.ResponseDeliverTx{

rolling-shutter/keyper/smstate.go

@@ -484,7 +484,7 @@ func (st *ShuttermintState) finalizeDKG(
 		err = scheduleShutterMessage(
 			ctx, queries,
 			"requesting DKG restart",
-			shmsg.NewEonStartVote(uint64(keyperEon.ActivationBlockNumber)),
+			shmsg.NewEonStartVote(uint64(keyperEon.KeyperConfigIndex)),
 		)
 		if err != nil {
 			return err

rolling-shutter/shmsg/messages.go

@@ -284,11 +284,11 @@ func NewPolyEval(eon uint64, receivers []common.Address, encryptedEvals [][]byte
 }
 
 // NewEonStartVote creates a new eon start vote message.
-func NewEonStartVote(activationBlockNumber uint64) *Message {
+func NewEonStartVote(keyperConfigIndex uint64) *Message {
 	return &Message{
 		Payload: &Message_EonStartVote{
 			EonStartVote: &EonStartVote{
-				ActivationBlockNumber: activationBlockNumber,
+				KeyperConfigIndex: keyperConfigIndex,
 			},
 		},
 	}

rolling-shutter/shmsg/shmsg.proto

@@ -47,7 +47,7 @@ message Apology {
 }
 
 message EonStartVote {
-        uint64 activation_block_number = 1;
+        uint64 keyper_config_index = 2;
 }
 
 message Message {