Kernel: Implement loopback network interface

kernel/include/kernel/Device/DeviceNumbers.h

@@ -20,6 +20,7 @@ namespace Kernel
 		NVMeController,
 		NVMeNamespace,
 		Ethernet,
+		Loopback,
 		TmpFS,
 	};
 

kernel/include/kernel/Networking/E1000/E1000.h

@@ -34,7 +34,8 @@ namespace Kernel
 
 	protected:
 		E1000(PCI::Device& pci_device)
-			: m_pci_device(pci_device)
+			: NetworkInterface(Type::Ethernet)
+			, m_pci_device(pci_device)
 		{ }
 		BAN::ErrorOr<void> initialize();
 

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;
+	};
+
+}

kernel/include/kernel/Networking/NetworkInterface.h

@@ -32,10 +32,11 @@ namespace Kernel
 		enum class Type
 		{
 			Ethernet,
+			Loopback,
 		};
 
 	public:
-		NetworkInterface();
+		NetworkInterface(Type);
 		virtual ~NetworkInterface() {}
 
 		virtual BAN::MACAddress get_mac_address() const = 0;
@@ -49,6 +50,8 @@ namespace Kernel
 		BAN::IPv4Address get_gateway() const { return m_gateway; }
 		void set_gateway(BAN::IPv4Address new_gateway) { m_gateway = new_gateway; }
 
+		Type type() const { return m_type; }
+
 		virtual bool link_up() = 0;
 		virtual int link_speed() = 0;
 

kernel/include/kernel/Networking/NetworkManager.h

@@ -22,7 +22,7 @@ namespace Kernel
 
 		BAN::ErrorOr<void> add_interface(PCI::Device& pci_device);
 
-		BAN::Vector<BAN::RefPtr<NetworkInterface>> interfaces() { return m_interfaces; }
+		BAN::Vector<BAN::RefPtr<NetworkInterface>>& interfaces() { return m_interfaces; }
 
 		BAN::ErrorOr<BAN::RefPtr<Socket>> create_socket(Socket::Domain, Socket::Type, mode_t, uid_t, gid_t);
 
@@ -31,6 +31,8 @@ namespace Kernel
 	private:
 		NetworkManager() {}
 
+		BAN::ErrorOr<void> add_interface(BAN::RefPtr<NetworkInterface>);
+
 	private:
 		BAN::UniqPtr<IPv4Layer>						m_ipv4_layer;
 		BAN::Vector<BAN::RefPtr<NetworkInterface>>	m_interfaces;

kernel/include/kernel/Networking/RTL8169/RTL8169.h

@@ -26,7 +26,8 @@ namespace Kernel
 
 	protected:
 		RTL8169(PCI::Device& pci_device)
-			: m_pci_device(pci_device)
+			: NetworkInterface(Type::Ethernet)
+			, m_pci_device(pci_device)
 		{ }
 		BAN::ErrorOr<void> initialize();