Commit 2a3339f6 authored by James Chapman's avatar James Chapman Committed by David S. Miller
Browse files

l2tp: store l2tpv2 sessions in per-net IDR 



L2TPv2 sessions are currently kept in a per-tunnel hashlist, keyed by
16-bit session_id. When handling received L2TPv2 packets, we need to
first derive the tunnel using the 16-bit tunnel_id or sock, then
lookup the session in a per-tunnel hlist using the 16-bit session_id.

We want to avoid using sk_user_data in the datapath and double lookups
on every packet. So instead, use a per-net IDR to hold L2TPv2
sessions, keyed by a 32-bit value derived from the 16-bit tunnel_id
and session_id. This will allow the L2TPv2 UDP receive datapath to
lookup a session with a single lookup without deriving the tunnel
first.

L2TPv2 sessions are held in their own IDR to avoid potential
key collisions with L2TPv3 sessions.

Signed-off-by: default avatarJames Chapman <jchapman@katalix.com>
Reviewed-by: default avatarTom Parkin <tparkin@katalix.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent aa5e17e1

net/l2tp/l2tp_core.c

+55 −15
Original line number Diff line number Diff line
@@ -107,12 +107,18 @@ struct l2tp_net { 
	/* Lock for write access to l2tp_tunnel_idr */

	spinlock_t l2tp_tunnel_idr_lock;

	struct idr l2tp_tunnel_idr;

	/* Lock for write access to l2tp_v3_session_idr/htable */

	/* Lock for write access to l2tp_v[23]_session_idr/htable */

	spinlock_t l2tp_session_idr_lock;

	struct idr l2tp_v2_session_idr;

	struct idr l2tp_v3_session_idr;

	struct hlist_head l2tp_v3_session_htable[16];

};



static inline u32 l2tp_v2_session_key(u16 tunnel_id, u16 session_id)

{

	return ((u32)tunnel_id) << 16 | session_id;

}



static inline unsigned long l2tp_v3_session_hashkey(struct sock *sk, u32 session_id)

{

	return ((unsigned long)sk) + session_id;
@@ -292,6 +298,24 @@ struct l2tp_session *l2tp_v3_session_get(const struct net *net, struct sock *sk, 
}

EXPORT_SYMBOL_GPL(l2tp_v3_session_get);



struct l2tp_session *l2tp_v2_session_get(const struct net *net, u16 tunnel_id, u16 session_id)

{

	u32 session_key = l2tp_v2_session_key(tunnel_id, session_id);

	const struct l2tp_net *pn = l2tp_pernet(net);

	struct l2tp_session *session;



	rcu_read_lock_bh();

	session = idr_find(&pn->l2tp_v2_session_idr, session_key);

	if (session && refcount_inc_not_zero(&session->ref_count)) {

		rcu_read_unlock_bh();

		return session;

	}

	rcu_read_unlock_bh();



	return NULL;

}

EXPORT_SYMBOL_GPL(l2tp_v2_session_get);



struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth)

{

	int hash;
@@ -477,23 +501,32 @@ int l2tp_session_register(struct l2tp_session *session, 
			err = l2tp_session_collision_add(pn, session, session2);

		}

		spin_unlock_bh(&pn->l2tp_session_idr_lock);

		if (err == -ENOSPC)

			err = -EEXIST;

	} else {

		session_key = l2tp_v2_session_key(tunnel->tunnel_id,

						  session->session_id);

		spin_lock_bh(&pn->l2tp_session_idr_lock);

		err = idr_alloc_u32(&pn->l2tp_v2_session_idr, NULL,

				    &session_key, session_key, GFP_ATOMIC);

		spin_unlock_bh(&pn->l2tp_session_idr_lock);

	}



	if (err)

	if (err) {

		if (err == -ENOSPC)

			err = -EEXIST;

		goto err_tlock;

	}



	l2tp_tunnel_inc_refcount(tunnel);



	hlist_add_head_rcu(&session->hlist, head);

	spin_unlock_bh(&tunnel->hlist_lock);



	if (tunnel->version == L2TP_HDR_VER_3) {

	spin_lock_bh(&pn->l2tp_session_idr_lock);

	if (tunnel->version == L2TP_HDR_VER_3)

		idr_replace(&pn->l2tp_v3_session_idr, session, session_key);

	else

		idr_replace(&pn->l2tp_v2_session_idr, session, session_key);

	spin_unlock_bh(&pn->l2tp_session_idr_lock);

	}



	trace_register_session(session);
@@ -1321,25 +1354,30 @@ static void l2tp_session_unhash(struct l2tp_session *session) 


	/* Remove the session from core hashes */

	if (tunnel) {

		struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);

		struct l2tp_session *removed = session;



		/* Remove from the per-tunnel hash */

		spin_lock_bh(&tunnel->hlist_lock);

		hlist_del_init_rcu(&session->hlist);

		spin_unlock_bh(&tunnel->hlist_lock);



		/* For L2TPv3 we have a per-net IDR: remove from there, too */

		if (tunnel->version == L2TP_HDR_VER_3) {

			struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);

			struct l2tp_session *removed = session;



		/* Remove from per-net IDR */

		spin_lock_bh(&pn->l2tp_session_idr_lock);

		if (tunnel->version == L2TP_HDR_VER_3) {

			if (hash_hashed(&session->hlist))

				l2tp_session_collision_del(pn, session);

			else

				removed = idr_remove(&pn->l2tp_v3_session_idr,

						     session->session_id);

		} else {

			u32 session_key = l2tp_v2_session_key(tunnel->tunnel_id,

							      session->session_id);

			removed = idr_remove(&pn->l2tp_v2_session_idr,

					     session_key);

		}

		WARN_ON_ONCE(removed && removed != session);

		spin_unlock_bh(&pn->l2tp_session_idr_lock);

		}



		synchronize_rcu();

	}
@@ -1802,6 +1840,7 @@ static __net_init int l2tp_init_net(struct net *net) 
	idr_init(&pn->l2tp_tunnel_idr);

	spin_lock_init(&pn->l2tp_tunnel_idr_lock);



	idr_init(&pn->l2tp_v2_session_idr);

	idr_init(&pn->l2tp_v3_session_idr);

	spin_lock_init(&pn->l2tp_session_idr_lock);
@@ -1825,6 +1864,7 @@ static __net_exit void l2tp_exit_net(struct net *net) 
		flush_workqueue(l2tp_wq);

	rcu_barrier();



	idr_destroy(&pn->l2tp_v2_session_idr);

	idr_destroy(&pn->l2tp_v3_session_idr);

	idr_destroy(&pn->l2tp_tunnel_idr);

}

net/l2tp/l2tp_core.h

+1 −0
Original line number Diff line number Diff line
@@ -231,6 +231,7 @@ struct l2tp_session *l2tp_tunnel_get_session(struct l2tp_tunnel *tunnel, 
					     u32 session_id);



struct l2tp_session *l2tp_v3_session_get(const struct net *net, struct sock *sk, u32 session_id);

struct l2tp_session *l2tp_v2_session_get(const struct net *net, u16 tunnel_id, u16 session_id);

struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth);

struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,

						const char *ifname);