Get all running non-loopback devices by default, thanks to Alexandre LAURENT!

devices.cpp

@@ -19,11 +19,58 @@
  *
  */
 
-
 #include "devices.h"
 
-device * determine_default_device()
+#include <iostream>
+#include <cstring>
+
+#include <sys/socket.h>
+#include <net/if.h>
+#include <ifaddrs.h>
+
+device * get_default_devices()
 {
-	return new device("eth0");
+	struct ifaddrs *ifaddr, *ifa;
+
+	if (getifaddrs(&ifaddr) == -1) 
+	{
+		std::cerr << "Fail to get interface addresses" << std::endl;
+		// perror("getifaddrs");
+		return NULL;
+	}
+
+	device* devices = NULL;
+	for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) 
+	{
+		if (ifa->ifa_addr == NULL)  
+			continue;  
+
+		// The interface is up, not a loopback and running ?
+		if ( !(ifa->ifa_flags & IFF_LOOPBACK) && 
+			 (ifa->ifa_flags & IFF_UP) &&
+			 (ifa->ifa_flags & IFF_RUNNING) )
+		{
+			// Check if the interface is already known by going through all the devices
+			bool found = false;
+			device* pIter = devices;
+			while(pIter != NULL)
+			{
+				if ( strcmp(ifa->ifa_name,pIter->name) == 0 )
+				{
+					found = true;
+				}
+				pIter = pIter->next;
+			}
+
+			// We found a new interface, let's add it
+			if ( found == false )
+			{
+				devices = new device(strdup(ifa->ifa_name),devices);
+			}
+		}
+	}
+
+	freeifaddrs(ifaddr);
+	return devices;
 }
 

devices.h

@@ -34,6 +34,10 @@ public:
 	device * next;
 };
 
-device * determine_default_device();
+/**
+ * This function can return null, if no good interface is found
+ * The function avoids loopback interface and down/not running interfaces
+ */
+device * get_default_devices();
 
 #endif

main.cpp

@@ -18,7 +18,7 @@ static void help(void)
 	//std::cerr << "		-f : format of packets on interface, default is eth.\n";
 	std::cerr << "		-p : sniff in promiscious mode (not recommended).\n";
 	std::cerr << "		-s : sort output by sent column.\n";
-	std::cerr << "		device : device(s) to monitor. default is eth0\n";
+	std::cerr << "		device : device(s) to monitor. default is all interfaces up and running excluding loopback\n";
 	std::cerr << std::endl;
 	std::cerr << "When nethogs is running, press:\n";
 	std::cerr << " q: quit\n";
@@ -88,7 +88,12 @@ int main (int argc, char** argv)
 
 	if (devices == NULL)
 	{
-		devices = determine_default_device();
+		devices = get_default_devices();
+        if ( devices == NULL )
+        {
+            std::cerr << "Not devices to monitor" << std::endl;
+            return 0;
+        }
 	}
 
 	if ((!tracemode) && (!DEBUG)){