Kernel: Implement loopback network interface

kernel/include/kernel/Networking/Loopback.h

@@ -0,0 +1,39 @@
+#pragma once
+
+#include <kernel/Networking/NetworkInterface.h>
+
+namespace Kernel
+{
+
+	class LoopbackInterface : public NetworkInterface
+	{
+	public:
+		static constexpr size_t buffer_size = BAN::numeric_limits<uint16_t>::max() + 1;
+
+	public:
+		static BAN::ErrorOr<BAN::RefPtr<LoopbackInterface>> create();
+
+		BAN::MACAddress get_mac_address() const override { return {}; }
+
+		bool link_up() override { return true; }
+		int link_speed() override { return 1000; }
+
+		size_t payload_mtu() const override { return buffer_size - sizeof(EthernetHeader); }
+
+	protected:
+		LoopbackInterface()
+			: NetworkInterface(Type::Loopback)
+		{}
+
+		BAN::ErrorOr<void> send_bytes(BAN::MACAddress destination, EtherType protocol, BAN::ConstByteSpan) override;
+
+		bool can_read_impl() const override { return false; }
+		bool can_write_impl() const override { return false; }
+		bool has_error_impl() const override { return false; }
+
+	private:
+		SpinLock m_buffer_lock;
+		BAN::UniqPtr<VirtualRange> m_buffer;
+	};
+
+}