Advertise W5500-EVB-Pico as network gateway using ARP (GARP?)

Question

Hi there, I’m using the W5500-EVB-Pico board with Arduino IDE to do some testing and I just want to send a packet with the packet structure that is in the code that I’m posting below, however, it seems W5500 libraries are handling ARP, and thus I can’t send custom raw packets. Is there something I’m doing wrong? In wireshark the operation code always shows (1) so it’s not announcing itself. #include <Ethernet.h> byte mac[] = { 0x00, 0xAA, 0xBB, 0xCC, 0xDE, 0x02 }; // MAC address of the Ethernet shield IPAddress ipAddress(192, 168, 1, 1); // IP address of the Ethernet shield IPAddress destIpAddress(255, 255, 255, 255); // Destination IP address EthernetUDP udpClient; void setup() { while (!Serial) { ; // wait for serial port to connect. Needed for native USB port only } Ethernet.init(17); Ethernet.begin(mac, ipAddress); Serial.begin(9600); delay(1000); udpClient.begin(0); // Open a random local port sendArpRequest(destIpAddress); //udpClient.begin(0); // Open a random local port //sendArpRequest(destIpAddress); } void sendArpRequest(const IPAddress& targetIp) { // Create the ARP request packet uint8_t arpRequestPacket[] = { 0x08, 0x06, 0x00, 0x01, // Hardware type: Ethernet (1) 0x08, 0x00, // Protocol type: IPv4 (0x0800) 0x06, // Hardware address length: 6 0x04, // Protocol address length: 4 0x00, 0x02, // ARP operation: Request (2) mac[0], mac[1], mac[2], mac[3], mac[4], mac[5], // Sender MAC address ipAddress[0], ipAddress[1], ipAddress[2], ipAddress[3], // Sender IP address 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // Target MAC address (zeroed out) targetIp[0], targetIp[1], targetIp[2], targetIp[3] // Target IP address }; // Send the ARP request packet udpClient.beginPacket(targetIp, 0); udpClient.write(arpRequestPacket, sizeof(arpRequestPacket)); udpClient.endPacket(); }

Eugeny · Answer

ARP/GARP is datalink layer, to get its functionality you must switch socket 0 into MACRAW mode. You seem to use UDP mode.

Eugeny · Answer

Look into the libraries you use, hopefully there’re calls for MACRAW mode, or universal calls (eg. data I/O) which can be reused for MACRAW mode. scooter: uint16_t regValue = socketMode << 8; Is Sn_MR 8-bit?

scooter · Answer

I’ll have to look deeper into the libraries then, thank you, I can’t test with the board until tomorrow, so I’ll revert back here then, in the meantime, here’s the Sn_MR register in the datasheet, it’s 8-bit, no? image855×269 25.1 KB

Eugeny · Answer

scooter: it’s 8-bit, no Yes, then it is not clear for me how you can scooter: Write(Sn_MR(socketNum), regValue); write 16-bit value into 8-bit register unless there’s some hidden logic in this function

scooter · Answer

Heh, great catch, still a lot for me to learn, thank you, absolute mistake by me! I’ll update on progress in around 14 hours!

scooter · Answer

So I managed to make progress, however I’m not managing to get packets sent out, it seems to always fail. I basically always get “failed to send”. Using the RP2040 Ethernet/ Ethernet2 library, it seems like I am setting the correct modes and registers through this code, I’d definitely appreciate some more guidance if possible #include #include #include #include // Initialize the Ethernet library byte mac[] = { 0x00, 0xAA, 0xBB, 0xCC, 0xDE, 0x02 }; // MAC address of the Ethernet shield IPAddress destIpAddress(255,255,255,255); IPAddress ipAddress(192, 168, 51, 1); // IP address of the Ethernet shield uint8_t ipAddr[4] = {255, 255, 255, 255}; void setup() { while (!Serial) { ; // wait for serial port to connect. Needed for native USB port only } // Initialize the SPI bus SPI.begin(); // Initialize the Ethernet library and the W5500 module Ethernet.init(17);// init 17 Serial.begin(9600); delay(1000); Ethernet.begin(mac); Serial.print("My IP address: "); Serial.println(Ethernet.localIP()); } void sendArpRequest(const IPAddress& targetIp) { // Create the ARP request packet uint8_t arpRequestPacket[] = { 0x08, 0x06, 0x00, 0x01, // Hardware type: Ethernet (1) 0x08, 0x00, // Protocol type: IPv4 (0x0800) 0x06, // Hardware address length: 6 0x04, // Protocol address length: 4 0x00, 0x02, // ARP operation: Request (2) mac[0], mac[1], mac[2], mac[3], mac[4], mac[5], // Sender MAC address ipAddress[0], ipAddress[1], ipAddress[2], ipAddress[3], // Sender IP address 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // Target MAC address (zeroed out) targetIp[0], targetIp[1], targetIp[2], targetIp[3] // Target IP address }; int packetSize = sizeof(arpRequestPacket); SOCKET macrawSocket = socket(0,SnMR::MACRAW, 0, 0); if (sendto(macrawSocket, arpRequestPacket, packetSize,ipAddr, 0) == 0) { Serial.println("failed to send"); } close(macrawSocket); } void loop() { sendArpRequest(destIpAddress); delay(5000); }

scooter · Answer

Solved this by using a different Library