I am developing a firewall program to block some DNS requests. It works normally on most Mac computers, but a few computers experience internet connectivity issues after installing the firewall. I have noticed a large number of logs in the console, such as "CFIL: Failed to create UDP flow". I want to know what caused this? Here is my code override func handleNewFlow(_ flow: NEFilterFlow) -> NEFilterNewFlowVerdict { guard let socketFlow = flow as? NEFilterSocketFlow, let endpoint = socketFlow.remoteEndpoint as? NWHostEndpoint, let appToken = flow.sourceAppAuditToken else { return .allow() } if endpoint.port == "53" && socketFlow.socketProtocol == IPPROTO_UDP { return .filterDataVerdict( withFilterInbound: false, peekInboundBytes: 0, filterOutbound: true, peekOutboundBytes: 1560) } return .allow() } override func handleOutboundData(from flow: NEFilterFlow, readBytesStartOffset offset: Int, readBytes: Data) -> NEFilterDataVerdict { guard let socketFlow = flow as? NEFilterSocketFlow, let endpoint = socketFlow.remoteEndpoint as? NWHostEndpoint, let appToken = flow.sourceAppAuditToken else { return .allow() } /* find rule... */ if let ruleName = ruleName { return .drop() } return .allow() }