This patch will fix the following problems:

r8168-8.038.00/src/r8168_n.c:17545:5: error: implicit declaration of function ‘SET_ETHTOOL_OPS’ [-Werror=implicit-function-declaration]
     SET_ETHTOOL_OPS(dev, &rtl8168_ethtool_ops);
     ^

r8168-8.038.00/src/r8168_n.c:19122:5: error: implicit declaration of function ‘PREPARE_DELAYED_WORK’ [-Werror=implicit-function-declaration]
     PREPARE_DELAYED_WORK(&tp->task, task);
     ^


From https://bugs.launchpad.net/ubuntu/+source/r8168-dkms/+bug/1345548 comment 4 & 5

--- r8168-8.038.00/src/r8168_n.c.orig
+++ r8168-8.038.00/src/r8168_n.c
@@ -17542,7 +17542,11 @@ rtl8168_init_one(struct pci_dev *pdev,
 
     RTL_NET_DEVICE_OPS(rtl8168_netdev_ops);
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3,16,0)
     SET_ETHTOOL_OPS(dev, &rtl8168_ethtool_ops);
+#else
+    dev->ethtool_ops = &rtl8168_ethtool_ops;
+#endif
 
     dev->watchdog_timeo = RTL8168_TX_TIMEOUT;
     dev->irq = pdev->irq;
@@ -19119,7 +19123,11 @@ static void rtl8168_schedule_work(struct
 {
     struct rtl8168_private *tp = netdev_priv(dev);
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3,15,0)
     PREPARE_DELAYED_WORK(&tp->task, task);
+#else
+    INIT_DELAYED_WORK(&tp->task, task);
+#endif
     schedule_delayed_work(&tp->task, 4);
 }
 #endif