This will simulate ping failure for these two hosts. We can now block ping packets from going to selected destination hosts, e.g. In the above, the default policy of the OUTPUT chain is ACCEPT, which is to allow all packets to go out of the box. OUTPUT, which is responsible for allowing packets to go out of the Linux machine. We are interested in the last chain, i.e. There are three chains in the above output. To verify this, issue the following command (you have to be root to use iptables):Ĭhain INPUT (policy ACCEPT 27798 packets, 8233K bytes) pkts bytes target prot opt in out source destination Chain FORWARD (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 27120 packets, 8354K bytes) pkts bytes target prot opt in out source destination In the initial stage, iptables allows all packets to come in and go out of the machine. The default firewall that comes with a Linux host is the iptables software. If ITNM is running on a Linux machine, we can use iptables to achieve this. To simulate ping failure, we can block ping packets from reaching some of the above devices. the Default Chassis Ping poll policy always succeeds for these devices. Initially, there are no events associated with these devices as the devices can be reached by the ncp_poller, i.e. Void MX_FREERTOS_Init(void) /* (MISRA C 2004 rule 8.We begin with the following Layer 2 network topology, which is the result of discovering five network devices using SNMP. Void StartDefaultTask(void const * argument) Int addr_size,sent_data char data_buffer Uint8_t lcpStartIndex, lcpStopIndex, lcpStartOld, lcpStart, lcpStop, dataReceived, timeOut, fillThePPPBuffer, gsmInitEnd, sendLCP, sendNCP, socketOpened, socketBind, socketOpen = 0 Uint8_t sent, send, connect, connectionStatus, endOfLcpNegotiation, NCPNegotiation = 0 Uint8_t receivedValue,connected,called = 0 Uint8_t recData, recDataOlder, recDataOlder2,recDataOlder3,recDataOlder4,recDataOlder5,recDataOlder6 Uint8_t lcpBufferIndex, quantityOfPackages = 0 The main thread, and the timer interrupt is as follows: /* Includes -*/ I use interrupt based UART transceiving which starts to fill the received buffer and put it into pppos_input_tcpip(ppp, recBuffer, recIndex) unless new data comes in 10ms. Thirdly, the most important, when I ping the IP of GSM above, the periodic data "~y " with length 68, is sent much more in time between MCU and GSM, means that pinging triggers the communication between GSM and MCU but no response back. That means my debugging of printf( ) cannot show me all of the periodic data. Secondly, after the establishment above, MCU and GSM module starts to send periodic data to each other as "~y " with length 49 and 53 respectively. The first problematic thing I viewed is the Netmask address however, LwIP PPPoS establishes this. The IP, gateway and netmask addresses that are established over PPP stack are as follows: IP = 5.26.61.173 However, when I start a PPPoS session, I cannot ping the IP which was successfully established over PPP. When I send AT commands over UART to GSM module as below, I get an IP address by the internal stack of the GSM module and ping it successfully: AT I use GSM module Telit GL865 in UART communication with STM32F7 MCU and softwares STM32CubeMX, Keil.
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