Allow gratuitous ARP requests.

Common++/header/MacAddress.h

@@ -137,6 +137,8 @@ namespace pcpp
 
 		/// A static value representing a zero value of MAC address, meaning address of value "00:00:00:00:00:00"
 		static MacAddress Zero;
+		/// A static value representing a broadcast MAC address, meaning address of value "ff:ff:ff:ff:ff:ff"
+		static MacAddress Broadcast;
 
 	private:
 		uint8_t m_Address[6] = { 0 };

Common++/src/MacAddress.cpp

@@ -5,6 +5,8 @@ namespace pcpp
 
 	MacAddress MacAddress::Zero(0, 0, 0, 0, 0, 0);
 
+	MacAddress MacAddress::Broadcast(0xff, 0xff, 0xff, 0xff, 0xff, 0xff);
+
 	std::string MacAddress::toString() const
 	{
 		char str[19];

Packet++/header/ArpLayer.h

@@ -52,6 +52,57 @@ namespace pcpp
 		ARP_REPLY = 0x0002     ///< ARP reply (response)
 	};
 
+	/**
+	 * @brief A struct representing the build data for an ARP request
+	 */
+	struct ArpRequest
+	{
+		MacAddress senderMacAddr;
+		IPv4Address senderIpAddr;
+		IPv4Address targetIpAddr;
+
+		ArpRequest(MacAddress senderMacAddress, IPv4Address senderIPAddress, IPv4Address targetIPAddress)
+		    : senderMacAddr(senderMacAddress), senderIpAddr(senderIPAddress), targetIpAddr(targetIPAddress) {};
+	};
+
+	/**
+	 * @brief A struct representing the build data for an ARP reply
+	 */
+	struct ArpReply
+	{
+		MacAddress senderMacAddr;
+		MacAddress targetMacAddr;
+		IPv4Address senderIpAddr;
+		IPv4Address targetIpAddr;
+
+		ArpReply(MacAddress senderMacAddress, MacAddress targetMacAddress, IPv4Address senderIPAddress,
+		         IPv4Address targetIPAddress)
+		    : senderMacAddr(senderMacAddress), targetMacAddr(targetMacAddress), senderIpAddr(senderIPAddress),
+		      targetIpAddr(targetIPAddress) {};
+	};
+
+	/**
+	 * @brief A struct representing the build data for a gratuitous ARP request
+	 */
+	struct GratuitousArpRequest
+	{
+		MacAddress senderMacAddr;
+		IPv4Address senderIpAddr;
+		GratuitousArpRequest(MacAddress senderMacAddress, IPv4Address senderIPAddress)
+		    : senderMacAddr(senderMacAddress), senderIpAddr(senderIPAddress) {};
+	};
+
+	/**
+	 * @brief A struct representing the build data a gratuitous ARP reply
+	 */
+	struct GratuitousArpReply
+	{
+		MacAddress senderMacAddr;
+		IPv4Address senderIpAddr;
+		GratuitousArpReply(MacAddress senderMacAddress, IPv4Address senderIPAddress)
+		    : senderMacAddr(senderMacAddress), senderIpAddr(senderIPAddress) {};
+	};
+
 	/**
 	 * @class ArpLayer
 	 * Represents an ARP protocol layer. Currently only IPv4 ARP messages are supported
@@ -83,6 +134,30 @@ namespace pcpp
 		ArpLayer(ArpOpcode opCode, const MacAddress& senderMacAddr, const MacAddress& targetMacAddr,
 		         const IPv4Address& senderIpAddr, const IPv4Address& targetIpAddr);
 
+		/**
+		 * @brief A constructor that creates an ARP request header.
+		 * @param arpRequest The ARP request data
+		 */
+		explicit ArpLayer(ArpRequest const& arpRequest);
+
+		/**
+		 * @brief A constructor that creates an ARP reply header.
+		 * @param arpReply The ARP reply data
+		 */
+		explicit ArpLayer(ArpReply const& arpReply);
+
+		/**
+		 * @brief A constructor that creates a gratuitous ARP request header.
+		 * @param gratuitousArpRequest The gratuitous ARP request data
+		 */
+		explicit ArpLayer(GratuitousArpRequest const& gratuitousArpRequest);
+
+		/**
+		 * @brief A constructor that creates a gratuitous ARP reply header.
+		 * @param gratuitousArpReply The gratuitous ARP reply data
+		 */
+		explicit ArpLayer(GratuitousArpReply const& gratuitousArpReply);
+
 		~ArpLayer() override = default;
 
 		/**

Packet++/src/ArpLayer.cpp

@@ -10,7 +10,7 @@ namespace pcpp
 	ArpLayer::ArpLayer(ArpOpcode opCode, const MacAddress& senderMacAddr, const MacAddress& targetMacAddr,
 	                   const IPv4Address& senderIpAddr, const IPv4Address& targetIpAddr)
 	{
-		const size_t headerLen = sizeof(arphdr);
+		constexpr size_t headerLen = sizeof(arphdr);
 		m_DataLen = headerLen;
 		m_Data = new uint8_t[headerLen];
 		memset(m_Data, 0, sizeof(headerLen));
@@ -24,15 +24,33 @@ namespace pcpp
 		arpHeader->senderIpAddr = senderIpAddr.toInt();
 	}
 
+	ArpLayer::ArpLayer(ArpRequest const& arpRequest)
+	    : ArpLayer(ARP_REQUEST, arpRequest.senderMacAddr, MacAddress::Zero, arpRequest.senderIpAddr,
+	               arpRequest.targetIpAddr)
+	{}
+
+	ArpLayer::ArpLayer(ArpReply const& arpReply)
+	    : ArpLayer(ARP_REPLY, arpReply.senderMacAddr, arpReply.targetMacAddr, arpReply.senderIpAddr,
+	               arpReply.targetIpAddr)
+	{}
+
+	ArpLayer::ArpLayer(GratuitousArpRequest const& gratuitousArpRequest)
+	    : ArpLayer(ARP_REQUEST, gratuitousArpRequest.senderMacAddr, MacAddress::Broadcast,
+	               gratuitousArpRequest.senderIpAddr, gratuitousArpRequest.senderIpAddr)
+	{}
+
+	ArpLayer::ArpLayer(GratuitousArpReply const& gratuitousArpReply)
+	    : ArpLayer(ARP_REPLY, gratuitousArpReply.senderMacAddr, MacAddress::Broadcast, gratuitousArpReply.senderIpAddr,
+	               gratuitousArpReply.senderIpAddr)
+	{}
+
 	void ArpLayer::computeCalculateFields()
 	{
 		arphdr* arpHeader = getArpHeader();
 		arpHeader->hardwareType = htobe16(1);  // Ethernet
 		arpHeader->hardwareSize = 6;
 		arpHeader->protocolType = htobe16(PCPP_ETHERTYPE_IP);  // assume IPv4 over ARP
 		arpHeader->protocolSize = 4;                           // assume IPv4 over ARP
-		if (arpHeader->opcode == htobe16(ARP_REQUEST))
-			MacAddress::Zero.copyTo(arpHeader->targetMacAddr);
 	}
 
 	bool ArpLayer::isRequest() const