Detect network interface of the default route without use of ip

fairmq/tools/Network.h

@@ -11,6 +11,7 @@
 
 #include <map>
 #include <string>
+#include <stdexcept>
 
 // forward declarations
 namespace boost
@@ -31,6 +32,8 @@ namespace mq
 namespace tools
 {
 
+struct DefaultRouteDetectionError : std::runtime_error { using std::runtime_error::runtime_error; };
+
 // returns a map with network interface names as keys and their IP addresses as values
 std::map<std::string, std::string> getHostIPs();