Added a portscan example. It's kind of nasty, but works.

examples/arpspoofing.cpp

@@ -74,7 +74,7 @@ int do_arp_spoofing(uint32_t iface, const string &iface_name, uint32_t gw, uint3
 }
 
 int main(int argc, char *argv[]) {
-    if(argc < 3 && cout << "Usage: <Gateway> <Victim> [Interface=eth0]\n")
+    if(argc < 3 && cout << "Usage: " << *argv << " <Gateway> <Victim> [Interface=eth0]\n")
         return 1;
     uint32_t gw, victim, own_ip;
     uint8_t own_hw[6];

examples/portscan.cpp

@@ -0,0 +1,116 @@
+/*
+ * libtins is a net packet wrapper library for crafting and
+ * interpreting sniffed packets.
+ *
+ * Copyright (C) 2011 Nasel
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#include <iostream>
+#include <string>
+#include <cstdlib>
+#include <pthread.h>
+#include "ip.h"
+#include "tcp.h"
+#include "ethernetII.h"
+#include "sniffer.h"
+#include "utils.h"
+#include "packetsender.h"
+
+
+using namespace std;
+using namespace Tins;
+
+struct ThreadData {
+    string interface;
+    string ip;
+};
+
+struct ScanHandler {
+    bool operator() (PDU *pdu) {
+        EthernetII *eth = dynamic_cast<EthernetII*>(pdu);
+        if(eth) {
+            IP *ip = dynamic_cast<IP*>(pdu->inner_pdu());
+            if(ip) {
+                TCP *tcp = dynamic_cast<TCP*>(ip->inner_pdu());
+                if(tcp) {
+                    if(tcp->get_flag(TCP::RST))
+                        cout << "Port: " << tcp->sport() << " closed\n";
+                    else if(tcp->get_flag(TCP::SYN))
+                        cout << "Port: " << tcp->sport() << " open\n";
+                }
+            }
+        }
+        return true;
+    }
+};
+
+
+Sniffer *sniffer;
+
+void send_syns(const string &iface, uint32_t dest_ip, int argc, char *argv[]) {
+    uint32_t own_ip;
+    if(!Utils::interface_ip(iface, own_ip) && cout << "Error obtaining interface ip.\n")
+        return;
+    PacketSender sender;
+    TCP *tcp = new TCP();
+    IP ip(dest_ip, own_ip, tcp);
+    tcp->set_flag(TCP::SYN, 1);
+    while(argc--) {
+        uint32_t port = atoi(*(argv++));
+        tcp->dport(port);
+        sender.send(&ip);
+    }
+}
+
+void *thread_proc(void *param) {
+    ThreadData *data = (ThreadData*)param;
+    ScanHandler handler;
+    AbstractSnifferHandler *my_handler = new SnifferHandler<ScanHandler>(&handler);
+    sniffer->sniff_loop("tcp and ip src " + data->ip, my_handler);
+    cout << "Listo\n";
+    delete my_handler;
+    return 0;
+}
+
+int main(int argc, char *argv[]) {
+    if(argc < 3 && cout << "Usage: " << *argv << " <IPADDR> <port1> [port2] [port3]\n")
+        return 1;
+    uint32_t ip;
+    try {
+        ip = Utils::resolve_ip(argv[1]);
+    }
+    catch(...) {
+        cout << "IP address is not valid.\n";
+        return 2;
+    }    
+    string iface = Utils::interface_from_ip(ip);
+    if(!iface.size() && cout << "Could not locate gateway interface for given ip address\n")
+        return 3;
+    sniffer = new Sniffer(iface, 300);
+    ThreadData data;
+    data.interface = iface;
+    data.ip = argv[1];
+    pthread_t thread;
+    pthread_create(&thread, 0, thread_proc, &data); 
+    
+    send_syns(iface, ip, argc - 2, argv + 2);
+    
+    sleep(5);
+    
+    pthread_cancel(thread);
+    delete sniffer;
+}