Issue #15: Check all possible names for the network interface

Signed-off-by: Felipe Shi Iu Wu <felipeshiwu@gmail.com>

src/linux/get_macaddr.cpp

@@ -25,17 +25,42 @@ std::string get_macaddr() {
     std::fstream file;
     std::string macaddr;
 
-    file.open("/sys/class/net/eth0/address", std::ifstream::in);
+    /* #FIXME The way we are breaking the getline to get the network 
+     * interface is not very efficient, because we create a char 
+     * array and a string to the same thing.
+    */
 
-    if (!file.is_open()) {
-        file.open("/sys/class/net/eth1/address", std::ifstream::in);
-        if (!file.is_open()) {
-            throw std::string("No address file found.");
+    char line[40];
+    char iface[20];
+    char dest[20];
+    std::string Iface;
+    std::string Destination;
+    std::string file_path;
+
+    FILE *fp = fopen("/proc/net/route", "r");
+    fgets (line, sizeof(line), fp);    // Skip the first line (column headers).
+
+    /* Loop to found the default network interface*/
+    while (fgets(line, sizeof(line), fp)) {
+
+        /* Found the interface name and check that it is default*/
+        sscanf(line, "%s %s\n", iface, dest);
+
+        Iface = iface;
+        Destination = dest;
+
+        if (Destination == "00000000") {  //  found default network interface
+            /* found macaddr with the default network interface*/
+            file_path = "/sys/class/net/"+Iface+"/address";
+            file.open(file_path, std::ifstream::in);
+            if (!file.is_open()) {
+                throw std::string("No address file found.");
+            }
+            getline(file, macaddr);  //  get macaddr
+            file.close();
         }
     }
-
-    getline(file, macaddr);
-    file.close();
+    fclose(fp);
 
     return macaddr;
 }