feat: add ethernet & TCP/IP stack

kernel/src/Net/Ipv4.hpp

@@ -0,0 +1,49 @@
+/*
+    * Ipv4.hpp
+    * Internet Protocol version 4
+    * Copyright (c) 2025 Daniel Hammer
+*/
+
+#pragma once
+#include <cstdint>
+
+namespace Net::Ipv4 {
+
+    constexpr uint8_t PROTO_ICMP = 1;
+    constexpr uint8_t PROTO_TCP  = 6;
+    constexpr uint8_t PROTO_UDP  = 17;
+
+    constexpr uint8_t DEFAULT_TTL = 64;
+
+    constexpr uint16_t HEADER_SIZE = 20; // Without options
+
+    struct Header {
+        uint8_t  VersionIhl;     // Version (4 bits) + IHL (4 bits)
+        uint8_t  Tos;            // Type of Service
+        uint16_t TotalLength;
+        uint16_t Identification;
+        uint16_t FlagsFragment;  // Flags (3 bits) + Fragment Offset (13 bits)
+        uint8_t  Ttl;
+        uint8_t  Protocol;
+        uint16_t Checksum;
+        uint32_t SrcIp;
+        uint32_t DstIp;
+    } __attribute__((packed));
+
+    // Initialize the IPv4 subsystem
+    void Initialize();
+
+    // Handle an incoming IP packet (called by Ethernet layer)
+    void OnPacketReceived(const uint8_t* data, uint16_t length);
+
+    // Send an IP packet with the given protocol and payload
+    bool Send(uint32_t destIp, uint8_t protocol, const uint8_t* payload, uint16_t payloadLen);
+
+    // Compute the Internet checksum over a buffer
+    uint16_t Checksum(const void* data, uint16_t length);
+
+    // Compute TCP/UDP pseudo-header checksum
+    uint16_t PseudoHeaderChecksum(uint32_t srcIp, uint32_t dstIp, uint8_t protocol,
+                                   uint16_t length, const void* data, uint16_t dataLen);
+
+}