fix: skip the undelegation if the amount is less than relay fee

x/stake/endblock.go

@@ -6,6 +6,7 @@ import (
 	abci "github.com/tendermint/tendermint/abci/types"
 
 	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/cosmos/cosmos-sdk/types/fees"
 	"github.com/cosmos/cosmos-sdk/x/stake/keeper"
 	"github.com/cosmos/cosmos-sdk/x/stake/types"
 )
@@ -280,13 +281,34 @@ func handleRefundStake(ctx sdk.Context, k keeper.Keeper) sdk.Events {
 	var refundEvents sdk.Events
 	count := 0
 
+	bscValidators := k.GetAllValidators(ctx)
+	bscValidatorsMap := make(map[string]types.Validator, len(bscValidators))
+	for _, validator := range bscValidators {
+		bscValidatorsMap[validator.OperatorAddr.String()] = validator
+	}
+	boundDenom := k.BondDenom(ctx)
+
 	for ; iterator.Valid(); iterator.Next() {
 		delegation := types.MustUnmarshalDelegation(k.CDC(), iterator.Key(), iterator.Value())
 		if delegation.CrossStake {
+			validator := bscValidatorsMap[delegation.ValidatorAddr.String()]
+			amount := validator.TokensFromShares(delegation.GetShares()).RawInt()
+
+			relayFeeCalc := fees.GetCalculator(types.CrossDistributeUndelegatedRelayFee)
+			if relayFeeCalc == nil {
+				ctx.Logger().Error("no fee calculator of distributeUndelegated")
+				return refundEvents
+			}
+			relayFee := relayFeeCalc(nil)
+			if relayFee.Tokens.AmountOf(boundDenom) >= amount {
+				// skip if the amount is less than relay fee
+				continue
+			}
+
 			result := handleMsgSideChainUndelegate(ctx.WithCrossStake(true), types.MsgSideChainUndelegate{
 				DelegatorAddr: delegation.DelegatorAddr,
 				ValidatorAddr: delegation.ValidatorAddr,
-				Amount:        sdk.NewCoin(k.BondDenom(ctx), delegation.GetShares().RawInt()),
+				Amount:        sdk.NewCoin(boundDenom, amount),
 				SideChainId:   k.ScKeeper.BscSideChainId(ctx),
 			}, k)
 			refundEvents = refundEvents.AppendEvents(result.Events)