Added ARP class. It's not working yet.

include/arp.h

@@ -0,0 +1,43 @@
+#ifndef __ARP_H
+#define __ARP_H
+
+
+#include <string>
+#include "pdu.h"
+
+namespace Tins {
+    
+    class ARP : public PDU {
+    public:
+        enum Flags {
+            REQUEST = 0x0100,
+            REPLY   = 0x0200
+        };
+    
+        ARP();
+        
+        void set_arp_request(const std::string &ip_dst, const std::string &ip_src, const std::string &hw_src = "");
+        
+        uint32_t header_size() const;
+        
+        bool send(PacketSender* sender);
+    private:
+        struct arphdr {
+            uint16_t ar_hrd;	/* format of hardware address	*/
+            uint16_t ar_pro;	/* format of protocol address	*/
+            uint8_t	ar_hln;		/* length of hardware address	*/
+            uint8_t	ar_pln;		/* length of protocol address	*/
+            uint16_t ar_op;		/* ARP opcode (command)		*/
+            
+            uint8_t ar_sha[6];	/* sender hardware address	*/
+            uint32_t ar_sip;	/* sender IP address		*/
+            uint8_t ar_tha[6];	/* target hardware address	*/
+            uint32_t ar_tip;	/* target IP address		*/
+        } __attribute__((packed));
+        
+        void write_serialization(uint8_t *buffer, uint32_t total_sz, const PDU *parent);
+        
+        arphdr _arp;
+    };
+};
+#endif

src/arp.cpp

@@ -0,0 +1,40 @@
+#include <cstring>
+#include <cassert>
+#include <netinet/in.h>
+#include "arp.h"
+#include "utils.h"
+
+
+using namespace std;
+
+Tins::ARP::ARP() : PDU(0x0608) {
+    std::memset(&_arp, 0, sizeof(arphdr));
+    _arp.ar_hrd = 0x0100;
+    _arp.ar_pro = 0x0008;
+    _arp.ar_hln = 6;
+    _arp.ar_pln = 4;
+}
+
+void Tins::ARP::set_arp_request(const string &ip_dst, const string &ip_src, const string &hw_src) {
+    _arp.ar_tip = Utils::resolve_ip(ip_dst);
+    _arp.ar_sip = Utils::resolve_ip(ip_src);
+}
+
+uint32_t Tins::ARP::header_size() const {
+    return sizeof(arphdr);
+}
+
+void Tins::ARP::write_serialization(uint8_t *buffer, uint32_t total_sz, const PDU *) {
+    assert(total_sz >= sizeof(arphdr));
+    memcpy(buffer, &_arp, sizeof(arphdr));
+}
+
+bool Tins::ARP::send(PacketSender* sender) {
+    struct sockaddr_in link_addr;
+    link_addr.sin_family = AF_INET;
+    link_addr.sin_port = 0;
+    link_addr.sin_addr.s_addr = _arp.ar_sip;
+
+    return sender->send_l3(this, (struct sockaddr*)&link_addr, sizeof(link_addr), PacketSender::IP_SOCKET);
+}
+