The FCS-at-end flag was being ignored in RadioTap. Added beacon display example.

examples/Makefile.in

@@ -1,26 +1,25 @@
 CXX=@CXX@
-CXXFLAGS=-c -Wall @CXXFLAGS@
-LDFLAGS=-lpcap -ltins -lpthread
-SOURCES=arpspoofing.cpp portscan.cpp 
+CXXFLAGS=-Wall @CXXFLAGS@
+LDFLAGS=-ltins
+EXECUTABLES=arpspoof portscan traceroute beacon_display
 
-OBJECTS=$(SOURCES:.cpp=.o)
-INCLUDE=
-EXECUTABLES=arpspoof portscan traceroute
-
-all: $(SOURCES) $(EXECUTABLES)
+all: $(EXECUTABLES)
 
 compile: $(OBJECTS)
 
 recompile: clean all
 
-arpspoof: arpspoofing.o
-	$(CXX) arpspoofing.o $(LDFLAGS) -o arpspoof
+arpspoof: 
+	$(CXX) arpspoofing.cpp -o arpspoofing $(CXXFLAGS) $(LDFLAGS)
 
-portscan: portscan.o
-	$(CXX) portscan.o $(LDFLAGS) -o portscan
+beacon_display: 
+	$(CXX) beacon_display.cpp -o beacon_display $(CXXFLAGS) $(LDFLAGS) 	
+
+portscan:
+	$(CXX) portscan.cpp -o portscan $(CXXFLAGS) $(LDFLAGS) -lpthread
 	
 traceroute: 
-	$(CXX) traceroute.cpp -o traceroute -std=c++0x -Wall $(LDFLAGS) 
+	$(CXX) traceroute.cpp -o traceroute -std=c++0x $(CXXFLAGS) $(LDFLAGS) 
 
 .cpp.o:
 	$(CXX) $(CXXFLAGS) $(INCLUDE) $< -o $@

examples/beacon_display.cpp

@@ -0,0 +1,49 @@
+#include <iostream>
+#include <map>
+#include <string>
+#include <tins/tins.h>
+
+using namespace Tins;
+
+class BeaconSniffer {
+public:
+    void run(const std::string &iface);
+private:
+    typedef Dot11::address_type address_type;
+    typedef std::map<address_type, std::string> ssids_type;
+
+    bool callback(PDU &pdu);
+    
+    ssids_type ssids;
+};
+
+void BeaconSniffer::run(const std::string &iface) {
+    Sniffer sniffer(iface, 1500, true, "type mgt subtype beacon");
+    sniffer.sniff_loop(make_sniffer_handler(this, &BeaconSniffer::callback));
+}
+
+bool BeaconSniffer::callback(PDU &pdu) {
+    Dot11Beacon *beacon = pdu.find_pdu<Dot11Beacon>();
+    if(beacon && !beacon->from_ds() && !beacon->to_ds()) {
+        address_type addr = beacon->addr2();
+        ssids_type::iterator it = ssids.find(addr);
+        if(it == ssids.end()) {
+            try {
+                it = ssids.insert(std::make_pair(addr, beacon->ssid())).first;
+                std::cout << it->first << " - " << it->second << std::endl;
+            }
+            catch(std::runtime_error&) {
+                // no ssid, just ignore it.
+            }
+        }
+    }
+    return true;
+}
+
+int main(int argc, char* argv[]) {
+    std::string interface = "wlan0";
+    if(argc == 2)
+        interface = argv[1];
+    BeaconSniffer sniffer;
+    sniffer.run(interface);
+}

include/pdu.h

@@ -189,7 +189,7 @@ namespace Tins {
         T *find_pdu(PDUType type = T::pdu_flag) {
             PDU *pdu = this;
             while(pdu) {
-                if(pdu->pdu_type() == type)
+                if(pdu->matches_flag(type))
                     return static_cast<T*>(pdu);
                 pdu = pdu->inner_pdu();
             }

src/radiotap.cpp

@@ -115,7 +115,14 @@ Tins::RadioTap::RadioTap(const uint8_t *buffer, uint32_t total_sz)
         buffer += sizeof(_rx_flags);
         total_sz -= sizeof(_rx_flags);
     }
-    if(total_sz)
+    if((flags() & FCS) != 0) {
+        if(total_sz <= 4)
+            throw std::runtime_error(msg);
+        else {
+            total_sz -= sizeof(uint32_t);
+        }
+    }
+    if(total_sz) 
         inner_pdu(Dot11::from_bytes(buffer, total_sz));
 }