xfrm interface: store xfrmi contexts in a hash by if_id

xfrmi_lookup() is called on every packet. Using a single list for
looking up if_id becomes a bottleneck when having many xfrm interfaces.
Signed-off-by: Eyal Birger <eyal.birger@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/xfrm/xfrm_interface.c

@@ -49,20 +49,28 @@ static struct rtnl_link_ops xfrmi_link_ops __read_mostly;
 static unsigned int xfrmi_net_id __read_mostly;
 static const struct net_device_ops xfrmi_netdev_ops;
 
+#define XFRMI_HASH_BITS	8
+#define XFRMI_HASH_SIZE	BIT(XFRMI_HASH_BITS)
+
 struct xfrmi_net {
 	/* lists for storing interfaces in use */
-	struct xfrm_if __rcu *xfrmi[1];
+	struct xfrm_if __rcu *xfrmi[XFRMI_HASH_SIZE];
 };
 
 #define for_each_xfrmi_rcu(start, xi) \
 	for (xi = rcu_dereference(start); xi; xi = rcu_dereference(xi->next))
 
+static u32 xfrmi_hash(u32 if_id)
+{
+	return hash_32(if_id, XFRMI_HASH_BITS);
+}
+
 static struct xfrm_if *xfrmi_lookup(struct net *net, struct xfrm_state *x)
 {
 	struct xfrmi_net *xfrmn = net_generic(net, xfrmi_net_id);
 	struct xfrm_if *xi;
 
-	for_each_xfrmi_rcu(xfrmn->xfrmi[0], xi) {
+	for_each_xfrmi_rcu(xfrmn->xfrmi[xfrmi_hash(x->if_id)], xi) {
 		if (x->if_id == xi->p.if_id &&
 		    (xi->dev->flags & IFF_UP))
 			return xi;
@@ -107,7 +115,7 @@ static struct xfrm_if *xfrmi_decode_session(struct sk_buff *skb,
 
 static void xfrmi_link(struct xfrmi_net *xfrmn, struct xfrm_if *xi)
 {
-	struct xfrm_if __rcu **xip = &xfrmn->xfrmi[0];
+	struct xfrm_if __rcu **xip = &xfrmn->xfrmi[xfrmi_hash(xi->p.if_id)];
 
 	rcu_assign_pointer(xi->next , rtnl_dereference(*xip));
 	rcu_assign_pointer(*xip, xi);
@@ -118,7 +126,7 @@ static void xfrmi_unlink(struct xfrmi_net *xfrmn, struct xfrm_if *xi)
 	struct xfrm_if __rcu **xip;
 	struct xfrm_if *iter;
 
-	for (xip = &xfrmn->xfrmi[0];
+	for (xip = &xfrmn->xfrmi[xfrmi_hash(xi->p.if_id)];
 	     (iter = rtnl_dereference(*xip)) != NULL;
 	     xip = &iter->next) {
 		if (xi == iter) {
@@ -162,7 +170,7 @@ static struct xfrm_if *xfrmi_locate(struct net *net, struct xfrm_if_parms *p)
 	struct xfrm_if *xi;
 	struct xfrmi_net *xfrmn = net_generic(net, xfrmi_net_id);
 
-	for (xip = &xfrmn->xfrmi[0];
+	for (xip = &xfrmn->xfrmi[xfrmi_hash(p->if_id)];
 	     (xi = rtnl_dereference(*xip)) != NULL;
 	     xip = &xi->next)
 		if (xi->p.if_id == p->if_id)
@@ -761,11 +769,14 @@ static void __net_exit xfrmi_exit_batch_net(struct list_head *net_exit_list)
 		struct xfrmi_net *xfrmn = net_generic(net, xfrmi_net_id);
 		struct xfrm_if __rcu **xip;
 		struct xfrm_if *xi;
+		int i;
 
-		for (xip = &xfrmn->xfrmi[0];
-		     (xi = rtnl_dereference(*xip)) != NULL;
-		     xip = &xi->next)
-			unregister_netdevice_queue(xi->dev, &list);
+		for (i = 0; i < XFRMI_HASH_SIZE; i++) {
+			for (xip = &xfrmn->xfrmi[i];
+			     (xi = rtnl_dereference(*xip)) != NULL;
+			     xip = &xi->next)
+				unregister_netdevice_queue(xi->dev, &list);
+		}
 	}
 	unregister_netdevice_many(&list);
 	rtnl_unlock();