Use device notifier in Linux kernel switch for detecting port status changes.

To report on link status and whether a port is administratively enabled or
disabled, the reference switches poll.  This change uses the Linux kernel's
device notification system, so that polling isn't necessary.

datapath/Modules.mk

@@ -6,6 +6,7 @@ openflow_sources = \
 	crc32.c \
 	datapath.c \
 	dp_dev.c \
+	dp_notify.c \
 	flow.c \
 	forward.c \
 	table-hash.c \

datapath/datapath.c

@@ -88,12 +88,10 @@ DEFINE_MUTEX(dp_mutex);
 EXPORT_SYMBOL(dp_mutex);
 
 static int dp_maint_func(void *data);
-static int update_port_status(struct net_bridge_port *p);
-static int send_port_status(struct net_bridge_port *p, uint8_t status);
+static void init_port_status(struct net_bridge_port *p);
 static int dp_genl_openflow_done(struct netlink_callback *);
 static struct net_bridge_port *new_nbp(struct datapath *,
 				       struct net_device *, int port_no);
-static int del_switch_port(struct net_bridge_port *);
 
 /* nla_shrink - reduce amount of space reserved by nla_reserve
  * @skb: socket buffer from which to recover room
@@ -309,7 +307,7 @@ static int new_dp(int dp_idx)
 	return 0;
 
 err_destroy_local_port:
-	del_switch_port(dp->local_port);
+	dp_del_switch_port(dp->local_port);
 err_destroy_chain:
 	chain_destroy(dp->chain);
 err_destroy_dp_dev:
@@ -378,16 +376,16 @@ int add_switch_port(struct datapath *dp, struct net_device *dev)
 	if (IS_ERR(p))
 		return PTR_ERR(p);
 
-	update_port_status(p);
+	init_port_status(p);
 
 	/* Notify the ctlpath that this port has been added */
-	send_port_status(p, OFPPR_ADD);
+	dp_send_port_status(p, OFPPR_ADD);
 
 	return 0;
 }
 
 /* Delete 'p' from switch. */
-static int del_switch_port(struct net_bridge_port *p)
+int dp_del_switch_port(struct net_bridge_port *p)
 {
 	/* First drop references to device. */
 	cancel_work_sync(&p->port_task);
@@ -403,7 +401,7 @@ static int del_switch_port(struct net_bridge_port *p)
 	synchronize_rcu();
 
 	/* Notify the ctlpath that this port no longer exists */
-	send_port_status(p, OFPPR_DELETE);
+	dp_send_port_status(p, OFPPR_DELETE);
 
 	dev_put(p->dev);
 	kfree(p);
@@ -419,7 +417,7 @@ static void del_dp(struct datapath *dp)
 
 	/* Drop references to DP. */
 	list_for_each_entry_safe (p, n, &dp->port_list, node)
-		del_switch_port(p);
+		dp_del_switch_port(p);
 	rcu_assign_pointer(dps[dp->dp_idx], NULL);
 
 	/* Kill off local_port dev references from buffered packets that have
@@ -443,15 +441,6 @@ static int dp_maint_func(void *data)
 	struct datapath *dp = (struct datapath *) data;
 
 	while (!kthread_should_stop()) {
-		struct net_bridge_port *p;
-
-		/* Check if port status has changed */
-		rcu_read_lock();
-		list_for_each_entry_rcu (p, &dp->port_list, node) 
-			if (update_port_status(p)) 
-				send_port_status(p, OFPPR_MOD);
-		rcu_read_unlock();
-
 		/* Timeout old entries */
 		chain_timeout(dp->chain);
 		msleep_interruptible(MAINT_SLEEP_MSECS);
@@ -886,20 +875,13 @@ dp_update_port_flags(struct datapath *dp, const struct ofp_port_mod *opm)
 	return 0;
 }
 
-/* Update the port status field of the bridge port.  A non-zero return
- * value indicates some field has changed. 
- *
- * NB: Callers of this function may hold the RCU read lock, so any
- * additional checks must not sleep.
- */
-static int
-update_port_status(struct net_bridge_port *p)
+/* Initialize the port status field of the bridge port. */
+static void
+init_port_status(struct net_bridge_port *p)
 {
 	unsigned long int flags;
-	uint32_t orig_status;
 
 	spin_lock_irqsave(&p->lock, flags);
-	orig_status = p->status;
 
 	if (p->dev->flags & IFF_UP) 
 		p->status &= ~OFPPFL_PORT_DOWN;
@@ -912,11 +894,10 @@ update_port_status(struct net_bridge_port *p)
 		p->status |= OFPPFL_LINK_DOWN;
 
 	spin_unlock_irqrestore(&p->lock, flags);
-	return (orig_status != p->status);
 }
 
-static int
-send_port_status(struct net_bridge_port *p, uint8_t status)
+int
+dp_send_port_status(struct net_bridge_port *p, uint8_t status)
 {
 	struct sk_buff *skb;
 	struct ofp_port_status *ops;
@@ -1162,7 +1143,7 @@ static int dp_genl_add_del_port(struct sk_buff *skb, struct genl_info *info)
 			err = -ENOENT;
 			goto out_put;
 		}
-		err = del_switch_port(port->br_port);
+		err = dp_del_switch_port(port->br_port);
 	}
 
 out_put:
@@ -1740,10 +1721,14 @@ static int __init dp_init(void)
 	if (err)
 		goto error;
 
-	err = dp_init_netlink();
+	err = register_netdevice_notifier(&dp_device_notifier);
 	if (err)
 		goto error_flow_exit;
 
+	err = dp_init_netlink();
+	if (err)
+		goto error_unreg_notifier;
+
 	/* Hook into callback used by the bridge to intercept packets.
 	 * Parasites we are. */
 	if (br_handle_frame_hook)
@@ -1752,6 +1737,8 @@ static int __init dp_init(void)
 
 	return 0;
 
+error_unreg_notifier:
+	unregister_netdevice_notifier(&dp_device_notifier);
 error_flow_exit:
 	flow_exit();
 error:
@@ -1763,6 +1750,7 @@ static void dp_cleanup(void)
 {
 	fwd_exit();
 	dp_uninit_netlink();
+	unregister_netdevice_notifier(&dp_device_notifier);
 	flow_exit();
 	br_handle_frame_hook = NULL;
 }

datapath/datapath.h

@@ -84,7 +84,9 @@ struct net_bridge_port {
 };
 
 extern struct mutex dp_mutex;
+extern struct notifier_block dp_device_notifier;
 
+int dp_del_switch_port(struct net_bridge_port *);
 int dp_output_port(struct datapath *, struct sk_buff *, int out_port,
 		   int ignore_no_fwd);
 int dp_output_control(struct datapath *, struct sk_buff *, uint32_t, 
@@ -92,6 +94,7 @@ int dp_output_control(struct datapath *, struct sk_buff *, uint32_t,
 int dp_set_origin(struct datapath *, uint16_t, struct sk_buff *);
 int dp_send_features_reply(struct datapath *, const struct sender *);
 int dp_send_config_reply(struct datapath *, const struct sender *);
+int dp_send_port_status(struct net_bridge_port *p, uint8_t status);
 int dp_send_flow_expired(struct datapath *, struct sw_flow *,
 			 enum ofp_flow_expired_reason);
 int dp_send_error_msg(struct datapath *, const struct sender *, 

datapath/dp_notify.c

@@ -0,0 +1,63 @@
+/*
+ * Distributed under the terms of the GNU GPL version 2.
+ * Copyright (c) 2007, 2008 The Board of Trustees of The Leland 
+ * Stanford Junior University
+ */
+
+/* Handle changes to managed devices */
+
+#include <linux/netdevice.h>
+
+#include "datapath.h"
+
+
+static int dp_device_event(struct notifier_block *unused, unsigned long event, 
+		void *ptr) 
+{
+	struct net_device *dev = ptr;
+	struct net_bridge_port *p = dev->br_port;
+	unsigned long int flags;
+	uint32_t orig_status;
+
+
+	/* Check if monitored port */
+	if (!p)
+		return NOTIFY_DONE;
+
+	spin_lock_irqsave(&p->lock, flags);
+	orig_status = p->status;
+
+	switch (event) {
+		case NETDEV_CHANGE:
+			if (netif_carrier_ok(p->dev))
+				p->status &= ~OFPPFL_LINK_DOWN;
+			else
+				p->status |= OFPPFL_LINK_DOWN;
+			break;
+
+		case NETDEV_DOWN:
+			p->status |= OFPPFL_PORT_DOWN;
+			break;
+
+		case NETDEV_UP:
+			p->status &= ~OFPPFL_PORT_DOWN;
+			break;
+
+		case NETDEV_UNREGISTER:
+			/* xxx Make sure this is correct */
+			spin_unlock_irqrestore(&p->lock, flags);
+			dp_del_switch_port(p);
+			return NOTIFY_DONE;
+			break;
+	}
+	spin_unlock_irqrestore(&p->lock, flags);
+
+	if (orig_status != p->status) 
+		dp_send_port_status(p, OFPPR_MOD);
+
+	return NOTIFY_DONE;
+}
+
+struct notifier_block dp_device_notifier = {
+	.notifier_call = dp_device_event
+};

datapath/linux-2.4/.gitignore

@@ -9,6 +9,7 @@
 /crc32.c
 /crc_t.c
 /dp_dev.c
+/dp_notify.c
 /flow.c
 /forward.c
 /forward_t.c

datapath/linux-2.6/.gitignore

@@ -6,6 +6,7 @@
 /crc_t.c
 /datapath.c
 /dp_dev.c
+/dp_notify.c
 /flow.c
 /forward.c
 /forward_t.c