Function createIPHeader

test/network/stack.test.js:37–55

(net, srcIP, dstIP, protocol, payloadLen)

// Helper to create IP header
function createIPHeader(net, srcIP, dstIP, protocol, payloadLen) {
    const header = Buffer.alloc(20);
    header[0] = 0x45; // Version 4, IHL 5
    header[1] = 0x00; // DSCP/ECN
    header.writeUInt16BE(20 + payloadLen, 2); // Total length
    header.writeUInt16BE(0, 4); // Identification
    header.writeUInt16BE(0x4000, 6); // Flags + Fragment offset (Don't fragment)
    header[8] = 64; // TTL
    header[9] = protocol; // Protocol
    header.writeUInt16BE(0, 10); // Checksum (calculate after)
    Buffer.from(srcIP.split('.').map(Number)).copy(header, 12);
    Buffer.from(dstIP.split('.').map(Number)).copy(header, 16);
    
    // Calculate checksum
    const checksum = net.calculateChecksum(header);
    header.writeUInt16BE(checksum, 10);
    
    return header;
}

const vmMac = Buffer.from([0x02, 0x00, 0x00, 0x00, 0x00, 0x01]);
const gatewayMac = Buffer.from([0x5a, 0x94, 0xef, 0xe4, 0x0c, 0xdd]);