Kernel: Collect IPv4 stuff in IPv4.h and ARP stuff in ARP.h.

Kernel/ARP.h

@@ -0,0 +1,61 @@
+#pragma once
+
+#include <Kernel/MACAddress.h>
+#include <Kernel/IPv4.h>
+#include <Kernel/EtherType.h>
+
+struct ARPOperation {
+enum : word {
+    Request = 1,
+    Response = 2,
+};
+};
+
+struct ARPHardwareType {
+enum : word {
+    Ethernet = 1,
+};
+};
+
+class [[gnu::packed]] ARPPacket {
+public:
+    word hardware_type() const { return ntohs(m_hardware_type); }
+    void set_hardware_type(word w) { m_hardware_type = htons(w); }
+
+    word protocol_type() const { return ntohs(m_protocol_type); }
+    void set_protocol_type(word w) { m_protocol_type = htons(w); }
+
+    byte hardware_address_length() const { return m_hardware_address_length; }
+    void set_hardware_address_length(byte b) { m_hardware_address_length = b; }
+
+    byte protocol_address_length() const { return m_protocol_address_length; }
+    void set_protocol_address_length(byte b) { m_protocol_address_length = b; }
+
+    word operation() const { return ntohs(m_operation); }
+    void set_operation(word w) { m_operation = htons(w); }
+
+    const MACAddress& sender_hardware_address() const { return m_sender_hardware_address; }
+    void set_sender_hardware_address(const MACAddress& address) { m_sender_hardware_address = address; }
+
+    const IPv4Address& sender_protocol_address() const { return m_sender_protocol_address; }
+    void set_sender_protocol_address(const IPv4Address& address) { m_sender_protocol_address = address; }
+
+    const MACAddress& target_hardware_address() const { return m_target_hardware_address; }
+    void set_target_hardware_address(const MACAddress& address) { m_target_hardware_address = address; }
+
+    const IPv4Address& target_protocol_address() const { return m_target_protocol_address; }
+    void set_target_protocol_address(const IPv4Address& address) { m_target_protocol_address = address; }
+
+private:
+    word m_hardware_type { 0x0100 };
+    word m_protocol_type { 0x0008 };
+    byte m_hardware_address_length { sizeof(MACAddress) };
+    byte m_protocol_address_length { sizeof(IPv4Address) };
+    word m_operation { 0 };
+    MACAddress m_sender_hardware_address;
+    IPv4Address m_sender_protocol_address;
+    MACAddress m_target_hardware_address;
+    IPv4Address m_target_protocol_address;
+};
+
+static_assert(sizeof(ARPPacket) == 28);