+/* We try to identify a flow through its rxhash first. The reason that
+ * we do not check rxq no. is becuase some cards(e.g 82599), chooses
+ * the rxq based on the txq where the last packet of the flow comes. As
+ * the userspace application move between processors, we may get a
+ * different rxq no. here. If we could not get rxhash, then we would
+ * hope the rxq no. may help here.
+ */
+static u16 tun_select_queue(struct net_device *dev, struct sk_buff *skb)
+{
+ struct tun_struct *tun = netdev_priv(dev);
+ u32 txq = 0;
+ u32 numqueues = 0;
+
+ rcu_read_lock();
+ numqueues = tun->numqueues;
+
+ txq = skb_get_rxhash(skb);
+ if (txq) {
+ /* use multiply and shift instead of expensive divide */
+ txq = ((u64)txq * numqueues) >> 32;
+ } else if (likely(skb_rx_queue_recorded(skb))) {
+ txq = skb_get_rx_queue(skb);
+ while (unlikely(txq >= numqueues))
+ txq -= numqueues;
+ }
+
+ rcu_read_unlock();
+ return txq;
+}
+
+static void tun_set_real_num_queues(struct tun_struct *tun)
+{
+ netif_set_real_num_tx_queues(tun->dev, tun->numqueues);
+ netif_set_real_num_rx_queues(tun->dev, tun->numqueues);
+}
+
+static void __tun_detach(struct tun_file *tfile, bool clean)
+{
+ struct tun_file *ntfile;
+ struct tun_struct *tun;
+ struct net_device *dev;
+
+ tun = rcu_dereference_protected(tfile->tun,
+ lockdep_rtnl_is_held());
+ if (tun) {
+ u16 index = tfile->queue_index;
+ BUG_ON(index >= tun->numqueues);
+ dev = tun->dev;
+
+ rcu_assign_pointer(tun->tfiles[index],
+ tun->tfiles[tun->numqueues - 1]);
+ rcu_assign_pointer(tfile->tun, NULL);
+ ntfile = rcu_dereference_protected(tun->tfiles[index],
+ lockdep_rtnl_is_held());
+ ntfile->queue_index = index;
+
+ --tun->numqueues;
+ sock_put(&tfile->sk);
+
+ synchronize_net();
+ /* Drop read queue */
+ skb_queue_purge(&tfile->sk.sk_receive_queue);
+ tun_set_real_num_queues(tun);
+
+ if (tun->numqueues == 0 && !(tun->flags & TUN_PERSIST))
+ if (dev->reg_state == NETREG_REGISTERED)
+ unregister_netdevice(dev);
+ }
+
+ if (clean) {
+ BUG_ON(!test_bit(SOCK_EXTERNALLY_ALLOCATED,
+ &tfile->socket.flags));
+ sk_release_kernel(&tfile->sk);
+ }
+}
+
+static void tun_detach(struct tun_file *tfile, bool clean)
+{
+ rtnl_lock();
+ __tun_detach(tfile, clean);
+ rtnl_unlock();
+}
+
+static void tun_detach_all(struct net_device *dev)
+{
+ struct tun_struct *tun = netdev_priv(dev);
+ struct tun_file *tfile;
+ int i, n = tun->numqueues;
+
+ for (i = 0; i < n; i++) {
+ tfile = rcu_dereference_protected(tun->tfiles[i],
+ lockdep_rtnl_is_held());
+ BUG_ON(!tfile);
+ wake_up_all(&tfile->wq.wait);
+ rcu_assign_pointer(tfile->tun, NULL);
+ --tun->numqueues;
+ }
+ BUG_ON(tun->numqueues != 0);
+
+ synchronize_net();
+ for (i = 0; i < n; i++) {
+ tfile = rcu_dereference_protected(tun->tfiles[i],
+ lockdep_rtnl_is_held());
+ /* Drop read queue */
+ skb_queue_purge(&tfile->sk.sk_receive_queue);
+ sock_put(&tfile->sk);
+ }
+}
+