[NET]: SG without checksum support is illegal.

net/core/dev.c

@@ -2582,6 +2582,16 @@ int register_netdevice(struct net_device *dev)
 	if ((ret = kobject_register(&dev->kobj)))
 		goto out_err;
 	
+	/* Fix illegal SG+CSUM combinations. */
+	if ((dev->features & NETIF_F_SG) &&
+	    !(dev->features & (NETIF_F_IP_CSUM |
+			       NETIF_F_NO_CSUM |
+			       NETIF_F_HW_CSUM))) {
+		printk("%s: Dropping NETIF_F_SG since no checksum feature.\n",
+		       dev->name);
+		dev->features &= ~NETIF_F_SG;
+	}
+
 	/*
 	 *	nil rebuild_header routine,
 	 *	that should be never called and used as just bug trap.