Relay add ban filter (#215)

* add filter for relay

* add pass

* check perstateTracer

* add interface check

jsonrpc/api_relay_filter_xlayer.go

@@ -0,0 +1,68 @@
+package jsonrpc
+
+import (
+	"encoding/json"
+
+	"github.com/0xPolygonHermez/zkevm-node/jsonrpc/types"
+)
+
+type ban func(request *types.Request) bool
+type banList []ban
+
+var banListInst banList
+
+func init() {
+	banListInst.register(debugTraceTransactionNotPrestateTracer)
+}
+
+func pass(request *types.Request) bool {
+	return !banListInst.ban(request)
+}
+
+func (c *banList) register(handler ban) {
+	*c = append(*c, handler)
+}
+
+func (c *banList) ban(request *types.Request) bool {
+	for _, handler := range *c {
+		if handler(request) {
+			return true
+		}
+	}
+
+	return false
+}
+
+// debutTraceTransactionNotPrestateTracer checks if the request is a debug_traceTransaction and the tracer is not preStateTracer
+func debugTraceTransactionNotPrestateTracer(req *types.Request) bool {
+	if req == nil || req.Method != "debug_traceTransaction" {
+		return false
+	}
+
+	// check params passed by request match function params
+	var testStruct []interface{}
+	if err := json.Unmarshal(req.Params, &testStruct); err != nil {
+		return false
+	}
+	inputs := make([]interface{}, len(testStruct))
+	if err := json.Unmarshal(req.Params, &inputs); err != nil {
+		return false
+	}
+
+	// for debug_tranceTransaction, at least 2 param is required
+	if len(inputs) < 2 { // nolint:gomnd
+		return false
+	}
+	traceCfgMap, ok := inputs[1].(map[string]interface{})
+	if !ok {
+		return false
+	}
+	if traceCfgMap["tracer"] == nil {
+		return false
+	}
+	if tracer, ok := traceCfgMap["tracer"].(string); ok && tracer != "prestateTracer" {
+		return true
+	}
+
+	return false
+}

jsonrpc/api_relay_xlayer.go

@@ -40,7 +40,7 @@ func getRelayDestURI(localDestURI string) string {
 }
 
 func tryRelay(localCfg ApiRelayConfig, request types.Request) (types.Response, bool) {
-	if shouldRelay(localCfg, request.Method) {
+	if shouldRelay(localCfg, request.Method) && pass(&request) {
 		destURI := getRelayDestURI(localCfg.DestURI)
 		res, err := client.JSONRPCRelay(destURI, request)
 		if err != nil {