address comment

Signed-off-by: kkk777-7 <kota.kimura0725@gmail.com>

Author: kkk777-7

internal/gatewayapi/backendtrafficpolicy.go

@@ -1688,6 +1688,9 @@ func buildBandwidthLimit(bandwidth *egv1a1.BandwidthLimitSpec) (*ir.BandwidthLim
 		if !ok {
 			return nil, fmt.Errorf("request limit value must be convertible to an int64")
 		}
+		if bytes < 0 {
+			return nil, fmt.Errorf("request limit value must be positive")
+		}
 		kibps, err := bandwidthToKibps(uint64(bytes), bandwidth.Request.Limit.Unit)
 		if err != nil {
 			return nil, fmt.Errorf("request: %w", err)
@@ -1701,6 +1704,9 @@ func buildBandwidthLimit(bandwidth *egv1a1.BandwidthLimitSpec) (*ir.BandwidthLim
 		if !ok {
 			return nil, fmt.Errorf("response limit value must be convertible to an int64")
 		}
+		if bytes < 0 {
+			return nil, fmt.Errorf("response limit value must be positive")
+		}
 		kibps, err := bandwidthToKibps(uint64(bytes), bandwidth.Response.Limit.Unit)
 		if err != nil {
 			return nil, fmt.Errorf("response: %w", err)