Base implementation of DHCP

Makefile

@@ -4,7 +4,7 @@ OBJS	= armc-start.o armc-cstartup.o armc-cstubs.o armc-cppstubs.o \
 	Drive.o Pi1541.o DiskImage.o iec_bus.o iec_commands.o m6502.o m6522.o \
 	gcr.o prot.o lz.o emmc.o diskio.o options.o Screen.o SSD1306.o ScreenLCD.o \
 	Timer.o FileBrowser.o DiskCaddy.o ROMs.o InputMappings.o xga_font_data.o m8520.o wd177x.o Pi1581.o SpinLock.o \
-	net.o net-tftp.o net-arp.o net-ethernet.o net-icmp.o net-ipv4.o net-udp.o
+	net.o net-tftp.o net-arp.o net-ethernet.o net-icmp.o net-ipv4.o net-udp.o net-dhcp.o
 
 SRCDIR   = src
 OBJS    := $(addprefix $(SRCDIR)/, $(OBJS))

src/main.cpp

@@ -377,6 +377,7 @@ void updateNetwork()
 	}
 
 	auto ethernetHeader = EthernetFrameHeader::Deserialize(ipBuffer);
+	const auto offset = ethernetHeader.SerializedLength();
 
 	static bool announcementSent = false;
 	if (!announcementSent)
@@ -388,10 +389,10 @@ void updateNetwork()
 	switch (ethernetHeader.type)
 	{
 	case ETHERTYPE_ARP:
-		HandleArpFrame(ethernetHeader, ipBuffer + ethernetHeader.SerializedLength());
+		HandleArpFrame(ethernetHeader, ipBuffer + offset);
 		break;
 	case ETHERTYPE_IPV4:
-		HandleIpv4Packet(ethernetHeader, ipBuffer + ethernetHeader.SerializedLength());
+		HandleIpv4Packet(ethernetHeader, ipBuffer + offset, sizeof(ipBuffer) - offset);
 		break;
 	}
 }
@@ -2048,4 +2049,3 @@ extern "C"
 #endif
 	}
 }
-

src/net-dhcp.cpp

@@ -0,0 +1,265 @@
+#include "net-dhcp.h"
+#include "net-udp.h"
+#include "net-ipv4.h"
+#include "net-ethernet.h"
+#include <random>
+#include <cassert>
+#include "types.h"
+#include <uspi.h>
+#include <uspios.h>
+
+namespace Net::Dhcp
+{
+	DhcpHeader::DhcpHeader()
+	{}
+
+	DhcpHeader::DhcpHeader(Opcode opcode, uint32_t transactionId) :
+		opcode(opcode),
+		hardwareAddressType(1), // Ethernet
+		hops(0),
+		transactionId(transactionId),
+		secondsElapsed(0),
+		flags(0), // TODO assumption
+		clientIpAddress(0),
+		yourIpAddress(0),
+		serverIpAddress(0),
+		relayIpAddress(0),
+		clientHardwareAddress{0},
+		serverHostname{0},
+		bootFile{0},
+		magicValue{99, 130, 83, 99}
+	{
+		const auto mac = GetMacAddress();
+		hardwareAddressLength = mac.size();
+		std::memcpy(clientHardwareAddress.data(), mac.data(), mac.size());
+	}
+
+	size_t DhcpHeader::Serialize(uint8_t* buffer, const size_t size) const
+	{
+		if (size < DhcpHeader::SerializedLength()) {
+			return 0;
+		}
+
+		size_t i = 0;
+		buffer[i++] = static_cast<uint8_t>(opcode);
+		buffer[i++] = hardwareAddressType;
+		buffer[i++] = hardwareAddressLength;
+		buffer[i++] = hops;
+		buffer[i++] = transactionId >> 24;
+		buffer[i++] = transactionId >> 16;
+		buffer[i++] = transactionId >> 8;
+		buffer[i++] = transactionId;
+		buffer[i++] = secondsElapsed >> 8;
+		buffer[i++] = secondsElapsed;
+		buffer[i++] = flags >> 8;
+		buffer[i++] = flags;
+		buffer[i++] = clientIpAddress >> 24;
+		buffer[i++] = clientIpAddress >> 16;
+		buffer[i++] = clientIpAddress >> 8;
+		buffer[i++] = clientIpAddress;
+		buffer[i++] = yourIpAddress >> 24;
+		buffer[i++] = yourIpAddress >> 16;
+		buffer[i++] = yourIpAddress >> 8;
+		buffer[i++] = yourIpAddress;
+		buffer[i++] = relayIpAddress >> 24;
+		buffer[i++] = relayIpAddress >> 16;
+		buffer[i++] = relayIpAddress >> 8;
+		buffer[i++] = relayIpAddress;
+
+		std::memcpy(buffer + i, clientHardwareAddress.data(), clientHardwareAddress.size());
+		i += clientHardwareAddress.size();
+
+		std::memcpy(buffer + i, serverHostname.data(), serverHostname.size());
+		i += serverHostname.size();
+
+		std::memcpy(buffer + i, bootFile.data(), bootFile.size());
+		i += bootFile.size();
+
+		std::memcpy(buffer + i, magicValue.data(), magicValue.size());
+		i += magicValue.size();
+
+		return i;
+	}
+
+	size_t DhcpHeader::Deserialize(
+		DhcpHeader& out, const uint8_t* buffer, const size_t size
+	) {
+		if (size < SerializedLength()) {
+			return 0;
+		}
+
+		out.opcode = static_cast<Opcode>(buffer[0]);
+		out.hardwareAddressType = buffer[1];
+		out.hardwareAddressLength = buffer[2];
+		out.hops = buffer[3];
+		out.transactionId =
+			buffer[4] << 24 | buffer[5] << 16 | buffer[6] << 8 | buffer[7];
+		out.secondsElapsed = buffer[8] << 8 | buffer[9];
+		out.flags = buffer[10] << 8 | buffer[11];
+		out.clientIpAddress =
+			buffer[12] << 24 | buffer[13] << 16 | buffer[14] << 8 | buffer[15];
+		out.yourIpAddress =
+			buffer[16] << 24 | buffer[17] << 16 | buffer[18] << 8 | buffer[19];
+		out.serverIpAddress =
+			buffer[20] << 24 | buffer[21] << 16 | buffer[22] << 8 | buffer[23];
+		out.relayIpAddress =
+			buffer[24] << 24 | buffer[25] << 16 | buffer[26] << 8 | buffer[27];
+
+		std::memcpy(
+			out.clientHardwareAddress.data(),
+			buffer + 28,
+			out.clientHardwareAddress.size()
+		);
+		std::memcpy(out.serverHostname.data(), buffer + 44, out.serverHostname.size());
+		std::memcpy(out.bootFile.data(), buffer + 108, out.bootFile.size());
+		std::memcpy(out.magicValue.data(), buffer + 236, out.magicValue.size());
+
+		assert(SerializedLength() == 240);
+		return 240;
+	}
+
+	static uint32_t transactionId;
+	static std::vector<uint32_t> offeredIpAddresses;
+	static std::vector<uint32_t> serverIpAddresses;
+	static std::vector<MacAddress> serverMacAddresses;
+	static bool serverSelected;
+
+	void sendRequest(uint32_t clientIpAddress, MacAddress serverMacAddress, uint32_t serverIpAddress)
+	{
+		const DhcpHeader dhcpHeader(Opcode::BootRequest, transactionId);
+
+		size_t udpLength =
+			dhcpHeader.SerializedLength() + UdpDatagramHeader::SerializedLength();
+		const UdpDatagramHeader udpHeader(
+			UDP_PORT_DHCP_CLIENT, UDP_PORT_DHCP_SERVER, udpLength);
+
+		size_t ipv4Length = udpLength + Ipv4Header::SerializedLength();
+		const Ipv4Header ipv4Header(
+			IP_PROTO_UDP, clientIpAddress, serverIpAddress, ipv4Length);
+		const EthernetFrameHeader ethernetHeader(
+			serverMacAddress, GetMacAddress(), ETHERTYPE_IPV4);
+
+		uint8_t buffer[USPI_FRAME_BUFFER_SIZE];
+		size_t size = 0;
+		const auto expectedSize =
+			ethernetHeader.SerializedLength() +
+			ipv4Header.SerializedLength() +
+			udpHeader.SerializedLength() +
+			dhcpHeader.SerializedLength();
+
+		size += ethernetHeader.Serialize(buffer + size);
+		size += ipv4Header.Serialize(buffer + size);
+		size += udpHeader.Serialize(buffer + size);
+		size += dhcpHeader.Serialize(buffer + size, USPI_FRAME_BUFFER_SIZE - size);
+
+		if (size != expectedSize) {
+			// TODO Log
+			return;
+		}
+
+		USPiSendFrame(buffer, size);
+	}
+
+	void discoverTimerHandler(unsigned int hTimer, void* nParam, void* nContext)
+	{
+		if (transactionId == 0 || offeredIpAddresses.empty())
+		{
+			return;
+		}
+
+		// Select the first IP address
+		const auto clientIpAddress = offeredIpAddresses[0];
+
+		// Send DHCP Requests to every server with that IP address.
+		for (size_t i = 0; i < serverIpAddresses.size(); i++)
+		{
+			sendRequest(clientIpAddress, serverMacAddresses[i], serverIpAddresses[i]);
+		}
+	}
+
+	void SendDiscover()
+	{
+		transactionId = std::rand();
+		offeredIpAddresses.clear();
+		const DhcpHeader dhcpHeader(Opcode::BootRequest, transactionId);
+
+		size_t udpLength =
+			dhcpHeader.SerializedLength() + UdpDatagramHeader::SerializedLength();
+		const UdpDatagramHeader udpHeader(
+			UDP_PORT_DHCP_CLIENT, UDP_PORT_DHCP_SERVER, udpLength);
+
+		size_t ipv4Length = udpLength + Ipv4Header::SerializedLength();
+		const Ipv4Header ipv4Header(IP_PROTO_UDP, 0, 0xFFFFFFFF, ipv4Length);
+		const EthernetFrameHeader ethernetHeader(GetMacAddress(), ETHERTYPE_IPV4);
+
+		uint8_t buffer[USPI_FRAME_BUFFER_SIZE];
+		size_t size = 0;
+		const auto expectedSize =
+			ethernetHeader.SerializedLength() +
+			ipv4Header.SerializedLength() +
+			udpHeader.SerializedLength() +
+			dhcpHeader.SerializedLength();
+
+		size += ethernetHeader.Serialize(buffer + size);
+		size += ipv4Header.Serialize(buffer + size);
+		size += udpHeader.Serialize(buffer + size);
+		size += dhcpHeader.Serialize(buffer + size, USPI_FRAME_BUFFER_SIZE - size);
+
+		if (size != expectedSize) {
+			// TODO Log
+			return;
+		}
+
+		USPiSendFrame(buffer, size);
+
+		// Wait a second for responses
+		StartKernelTimer(1 * HZ, discoverTimerHandler, nullptr, nullptr);
+	}
+
+	static void handleOfferPacket(
+		const EthernetFrameHeader ethernetHeader, const DhcpHeader dhcpHeader
+	) {
+		offeredIpAddresses.push_back(dhcpHeader.yourIpAddress);
+		serverIpAddresses.push_back(dhcpHeader.serverIpAddress);
+		serverMacAddresses.push_back(ethernetHeader.macSource);
+	}
+
+	static void handleAckPacket(
+		const EthernetFrameHeader ethernetHeader, const DhcpHeader dhcpHeader
+	) {
+		Ipv4Address = dhcpHeader.yourIpAddress;
+
+		// TODO Schedule handler for end of lease.
+
+		transactionId = 0;
+		offeredIpAddresses.clear();
+		serverIpAddresses.clear();
+		serverMacAddresses.clear();
+		serverSelected = false;
+	}
+
+	void HandlePacket(
+		const EthernetFrameHeader& ethernetHeader, const uint8_t* buffer, size_t size
+	) {
+		auto dhcpHeader = DhcpHeader();
+		const auto dhcpSize = DhcpHeader::Deserialize(dhcpHeader, buffer, size);
+		if (dhcpSize == 0) {
+			// TODO log
+			return;
+		}
+
+		if (dhcpHeader.opcode != Opcode::BootReply) return;
+		if (dhcpHeader.hardwareAddressType != 1) return;
+		if (dhcpHeader.hardwareAddressLength != 6) return;
+		if (dhcpHeader.transactionId != transactionId) return;
+
+		if (!serverSelected)
+		{
+			handleOfferPacket(ethernetHeader, dhcpHeader);
+		}
+		else
+		{
+			handleAckPacket(ethernetHeader, dhcpHeader);
+		}
+	}
+} // namespace Net::Dhcp

src/net-dhcp.h

@@ -0,0 +1,93 @@
+#pragma once
+#include "net.h"
+
+namespace Net::Dhcp
+{
+	enum class Opcode : uint8_t
+	{
+		BootRequest = 1,
+		BootReply = 2,
+	};
+
+	struct DhcpHeader
+	{
+		/// Message op code / message type. 1 = BOOTREQUEST, 2 = BOOTREPLY
+		Opcode opcode;
+
+		/// Hardware address type, see ARP section in "Assigned Numbers" RFC
+		uint8_t hardwareAddressType;
+
+		uint8_t hardwareAddressLength;
+
+		/// Client sets to zero, optionally used by relay agents when booting via a
+		/// relay agent.
+		uint8_t hops;
+
+		/// A random number chosen by the client, used by the client and server to
+		/// associate messages and responses between a client and a server.
+		uint32_t transactionId;
+
+		/// Filled in by client, seconds elapsed since client began address acquisition
+		/// or renewal process.
+		uint16_t secondsElapsed;
+
+		uint16_t flags;
+
+		/// Only filled in if client is in BOUND, RENEW or REBINDING state and can
+		/// respond to ARP requests.
+		uint32_t clientIpAddress;
+
+		/// 'your' (client) IP address.
+		uint32_t yourIpAddress;
+
+		/// IP address of next server to use in bootstrap; returned in DHCPOFFER,
+		/// DHCPACK by server.
+		uint32_t serverIpAddress;
+
+		/// Relay agent IP address, used in booting via a relay agent.
+		uint32_t relayIpAddress;
+
+		std::array<uint8_t, 16> clientHardwareAddress;
+
+		/// Optional server host name, null terminated string.
+		std::array<uint8_t, 64> serverHostname;
+
+		/// Boot file name, null terminated string; "generic" name or null in
+		/// DHCPDISCOVER, fully qualified directory-path name in DHCPOFFER.
+		std::array<uint8_t, 128> bootFile;
+
+		/// Always 99, 130, 83, 99
+		std::array<uint8_t, 4> magicValue;
+
+		DhcpHeader();
+		DhcpHeader(Opcode opcode, uint32_t transactionId);
+
+		constexpr static size_t SerializedLength()
+		{
+			return
+				sizeof(Opcode) +
+				sizeof(hardwareAddressType) +
+				sizeof(hardwareAddressLength) +
+				sizeof(hops) +
+				sizeof(transactionId) +
+				sizeof(secondsElapsed) +
+				sizeof(flags) +
+				sizeof(clientIpAddress) +
+				sizeof(yourIpAddress) +
+				sizeof(serverIpAddress) +
+				sizeof(relayIpAddress) +
+				sizeof(clientHardwareAddress) +
+				sizeof(serverHostname) +
+				sizeof(bootFile) +
+				sizeof(magicValue);
+		}
+
+		size_t Serialize(uint8_t* buffer, const size_t size) const;
+		static size_t Deserialize(
+			DhcpHeader& out, const uint8_t* buffer, const size_t size);
+	};
+
+	void SendDiscover();
+	void HandlePacket(
+		const EthernetFrameHeader& ethernetHeader, const uint8_t* buffer, size_t size);
+} // namespace Net::Dhcp

src/net-ethernet.cpp

@@ -9,9 +9,20 @@ EthernetFrameHeader::EthernetFrameHeader(std::uint16_t type) :
 	type(type)
 {}
 
+EthernetFrameHeader::EthernetFrameHeader(
+	MacAddress macSource, uint16_t type
+) :
+	macDestination{255, 255, 255, 255, 255, 255},
+	macSource(macSource),
+	type(type)
+{}
+
 EthernetFrameHeader::EthernetFrameHeader(
 	MacAddress macDestination, MacAddress macSource, uint16_t type
-) : macDestination(macDestination), macSource(macSource), type(type)
+) :
+	macDestination(macDestination),
+	macSource(macSource),
+	type(type)
 {}
 
 std::size_t EthernetFrameHeader::Serialize(uint8_t* buffer) const

src/net-ethernet.h

@@ -9,6 +9,7 @@ struct EthernetFrameHeader
 
 	EthernetFrameHeader();
 	EthernetFrameHeader(std::uint16_t type);
+	EthernetFrameHeader(MacAddress macSource, uint16_t type);
 	EthernetFrameHeader(MacAddress macDestination, MacAddress macSource, uint16_t type);
 
 	constexpr static std::size_t SerializedLength()

src/net-tftp.cpp

@@ -71,9 +71,15 @@ static std::unique_ptr<TftpPacket> handleTftpWriteRequest(const uint8_t* data)
 	return response;
 }
 
-static std::unique_ptr<TftpPacket> handleTftpData(const uint8_t* data, size_t length)
+static std::unique_ptr<TftpPacket> handleTftpData(const uint8_t* buffer, size_t size)
 {
-	auto packet = TftpDataPacket::Deserialize(data, length);
+	TftpDataPacket packet;
+	const auto tftpSize = TftpDataPacket::Deserialize(packet, buffer, size);
+	if (size == 0)
+	{
+		// TODO log
+		return nullptr;
+	}
 
 	if (packet.blockNumber != currentBlockNumber + 1)
 	{
@@ -268,11 +274,15 @@ size_t TftpAcknowledgementPacket::Serialize(uint8_t* buffer) const
 //
 TftpDataPacket::TftpDataPacket() : opcode(TFTP_OP_DATA) {}
 
-TftpDataPacket TftpDataPacket::Deserialize(const uint8_t* buffer, size_t length)
-{
-	TftpDataPacket self;
-	self.opcode = buffer[0] << 8 | buffer[1];
-	self.blockNumber = buffer[2] << 8 | buffer[3];
-	self.data = std::vector<uint8_t>(buffer + 4, buffer + length);
-	return self;
+size_t TftpDataPacket::Deserialize(
+	TftpDataPacket& out, const uint8_t* buffer, size_t size
+) {
+	if (size < sizeof(opcode) + sizeof(blockNumber)) {
+		return 0;
+	}
+
+	out.opcode = buffer[0] << 8 | buffer[1];
+	out.blockNumber = buffer[2] << 8 | buffer[3];
+	out.data = std::vector<uint8_t>(buffer + 4, buffer + size);
+	return size;
 }

src/net-tftp.h

@@ -64,5 +64,6 @@ struct TftpDataPacket
 	std::vector<uint8_t> data;
 
 	TftpDataPacket();
-	static TftpDataPacket Deserialize(const uint8_t* buffer, size_t length);
+	static size_t Deserialize(
+		TftpDataPacket& out, const uint8_t* buffer, size_t length);
 };

src/net-udp.cpp

@@ -14,7 +14,7 @@ UdpDatagramHeader::UdpDatagramHeader(
     checksum(0)
 {}
 
-size_t UdpDatagramHeader::Serialize(uint8_t* buffer)
+size_t UdpDatagramHeader::Serialize(uint8_t* buffer) const
 {
     size_t i = 0;
     buffer[i++] = sourcePort >> 8;

src/net-udp.h

@@ -22,6 +22,6 @@ struct UdpDatagramHeader
 			sizeof(checksum);
 	}
 
-	size_t Serialize(uint8_t* buffer);
+	size_t Serialize(uint8_t* buffer) const;
 	static UdpDatagramHeader Deserialize(const uint8_t* buffer);
 };

src/net.cpp

@@ -6,6 +6,7 @@
 #include "net-icmp.h"
 #include "net-ipv4.h"
 #include "net-udp.h"
+#include "net-dhcp.h"
 #include "net.h"
 #include "types.h"
 
@@ -82,9 +83,11 @@ void HandleArpFrame(const EthernetFrameHeader ethernetHeader, uint8_t* buffer)
 //
 // IPv4
 //
-void HandleIpv4Packet(const EthernetFrameHeader ethernetHeader, const uint8_t* buffer)
-{
+void HandleIpv4Packet(
+	const EthernetFrameHeader ethernetHeader, const uint8_t* buffer, const size_t size
+) {
 	const auto ipv4Header = Ipv4Header::Deserialize(buffer);
+	const auto offset = Ipv4Header::SerializedLength();
 
 	// Update ARP table
 	ArpTable.insert(std::make_pair(ipv4Header.sourceIp, ethernetHeader.macSource));
@@ -100,8 +103,7 @@ void HandleIpv4Packet(const EthernetFrameHeader ethernetHeader, const uint8_t* b
 	}
 	else if (ipv4Header.protocol == IP_PROTO_UDP)
 	{
-		HandleUdpDatagram(
-			ethernetHeader, ipv4Header, buffer + ipv4Header.SerializedLength());
+		HandleUdpDatagram(ethernetHeader, ipv4Header, buffer + offset, size - offset);
 	}
 }
 
@@ -111,12 +113,20 @@ void HandleIpv4Packet(const EthernetFrameHeader ethernetHeader, const uint8_t* b
 void HandleUdpDatagram(
 	const EthernetFrameHeader ethernetHeader,
 	const Ipv4Header ipv4Header,
-	const uint8_t* buffer
-)
-{
+	const uint8_t* buffer,
+	const size_t size
+) {
 	const auto udpHeader = UdpDatagramHeader::Deserialize(buffer);
 
-	if (udpHeader.destinationPort == 69) // nice
+	if (udpHeader.destinationPort == UDP_PORT_DHCP_CLIENT)
+	{
+		Net::Dhcp::HandlePacket(
+			ethernetHeader,
+			buffer + udpHeader.SerializedLength(),
+			size - udpHeader.SerializedLength()
+		);
+	}
+	else if (udpHeader.destinationPort == UDP_PORT_TFTP)
 	{
 		HandleTftpDatagram(
 			ethernetHeader,
@@ -155,8 +165,10 @@ void SendIcmpEchoRequest(MacAddress mac, uint32_t ip)
 
 void HandleIcmpFrame(const uint8_t* buffer)
 {
+	// TODO Don't re-parse the upper layers
 	size_t requestSize = 0;
-	const auto requestEthernetHeader = EthernetFrameHeader::Deserialize(buffer + requestSize);
+	const auto requestEthernetHeader =
+		EthernetFrameHeader::Deserialize(buffer + requestSize);
 	requestSize += requestEthernetHeader.SerializedLength();
 	const auto requestIpv4Header = Ipv4Header::Deserialize(buffer + requestSize);
 	requestSize += requestIpv4Header.SerializedLength();
@@ -165,7 +177,8 @@ void HandleIcmpFrame(const uint8_t* buffer)
 
 	if (requestIcmpHeader.type == ICMP_ECHO_REQUEST)
 	{
-		const auto requestEchoHeader = IcmpEchoHeader::Deserialize(buffer + requestSize);
+		const auto requestEchoHeader =
+			IcmpEchoHeader::Deserialize(buffer + requestSize);
 		requestSize += requestEchoHeader.SerializedLength();
 
 		const IcmpPacketHeader responseIcmpHeader(ICMP_ECHO_REPLY, 0);
@@ -309,7 +322,7 @@ MacAddress GetMacAddress()
 	return macAddress;
 }
 
-const uint32_t Ipv4Address = 0xC0A80164;
+uint32_t Ipv4Address = 0xC0A80164;
 const MacAddress MacBroadcast{0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
 
 bool FileUploaded = false;

src/net.h

@@ -15,6 +15,12 @@ enum ArpOperation {
 	ARP_OPERATION_REPLY = 2,
 };
 
+enum UdpPort {
+	UDP_PORT_DHCP_SERVER = 67,
+	UDP_PORT_DHCP_CLIENT = 68,
+	UDP_PORT_TFTP = 69,  // nice
+};
+
 typedef std::array<uint8_t, 6> MacAddress;
 
 struct EthernetFrameHeader;
@@ -41,7 +47,8 @@ void SendArpAnnouncement(MacAddress mac, uint32_t ip);
 //
 // IPv4
 //
-void HandleIpv4Packet(const EthernetFrameHeader ethernetHeader, const uint8_t* buffer);
+void HandleIpv4Packet(
+	const EthernetFrameHeader ethernetHeader, const uint8_t* buffer, const size_t size);
 
 //
 // UDP
@@ -49,7 +56,8 @@ void HandleIpv4Packet(const EthernetFrameHeader ethernetHeader, const uint8_t* b
 void HandleUdpDatagram(
 	const EthernetFrameHeader ethernetHeader,
 	const Ipv4Header ipv4Header,
-	const uint8_t* buffer
+	const uint8_t* buffer,
+	const size_t size
 );
 
 void HandleTftpDatagram(
@@ -73,7 +81,7 @@ std::uint16_t InternetChecksum(const void* data, std::size_t size);
 MacAddress GetMacAddress();
 
 extern const MacAddress MacBroadcast;
-extern const uint32_t Ipv4Address;
+extern uint32_t Ipv4Address;
 
 extern bool FileUploaded;
 extern std::unordered_map<std::uint32_t, MacAddress> ArpTable;