Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit b8732fb7 authored by Jason Wang's avatar Jason Wang Committed by David S. Miller
Browse files

tuntap: limit the number of flow caches 



We create new flow caches when a new flow is identified by tuntap, This may lead
some issues:

- userspace may produce a huge amount of short live flows to exhaust host memory
- the unlimited number of flow caches may produce a long list which increase the
  time in the linear searching

Solve this by introducing a limit of total number of flow caches.

Cc: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent edfb6a14

drivers/net/tun.c

+6 −1
Original line number Diff line number Diff line
@@ -113,6 +113,7 @@ struct tap_filter { 
 * the netdevice to be fit in one page. So we can make sure the success of

 * memory allocation. TODO: increase the limit. */

#define MAX_TAP_QUEUES DEFAULT_MAX_NUM_RSS_QUEUES

#define MAX_TAP_FLOWS  4096



#define TUN_FLOW_EXPIRE (3 * HZ)
@@ -185,6 +186,7 @@ struct tun_struct { 
	unsigned int numdisabled;

	struct list_head disabled;

	void *security;

	u32 flow_count;

};



static inline u32 tun_hashfn(u32 rxhash)
@@ -218,6 +220,7 @@ static struct tun_flow_entry *tun_flow_create(struct tun_struct *tun, 
		e->queue_index = queue_index;

		e->tun = tun;

		hlist_add_head_rcu(&e->hash_link, head);

		++tun->flow_count;

	}

	return e;

}
@@ -228,6 +231,7 @@ static void tun_flow_delete(struct tun_struct *tun, struct tun_flow_entry *e) 
		  e->rxhash, e->queue_index);

	hlist_del_rcu(&e->hash_link);

	kfree_rcu(e, rcu);

	--tun->flow_count;

}



static void tun_flow_flush(struct tun_struct *tun)
@@ -317,7 +321,8 @@ static void tun_flow_update(struct tun_struct *tun, u32 rxhash, 
		e->updated = jiffies;

	} else {

		spin_lock_bh(&tun->lock);

		if (!tun_flow_find(head, rxhash))

		if (!tun_flow_find(head, rxhash) &&

		    tun->flow_count < MAX_TAP_FLOWS)

			tun_flow_create(tun, head, rxhash, queue_index);



		if (!timer_pending(&tun->flow_gc_timer))