Bring up tun interface upon creation

TunDevice.cpp

@@ -44,6 +44,25 @@ TunDevice::TunDevice(const std::string& dev)
     _dev_name = ifr.ifr_name;
     _fd = fd;
 
+    // Bring interface up
+    kdebugf("Bringing interface up...\n");
+    int sockfd = socket(AF_INET, SOCK_DGRAM, 0); // Any socket will do
+    if(ioctl(sockfd, SIOCGIFFLAGS, (void*) &ifr) < 0) {
+        close(fd);
+        close(sockfd);
+        throw TunDevice::InitializationError(
+                "Could not get tunnel interface flags", errno, true);
+    }
+    ifr.ifr_flags |= IFF_UP | IFF_RUNNING;
+
+    if(ioctl(sockfd, SIOCSIFFLAGS, (void*) &ifr) < 0) {
+        close(fd);
+        close(sockfd);
+        throw TunDevice::InitializationError(
+                "Could not bring tunnel interface up", errno, true);
+    }
+    close(sockfd);
+
     // The device is now fully set up
     _poll_fd.fd = _fd;
     _poll_fd.events = POLLIN;