bridge: add support for user mode STP

This patchset based on work by Aji_Srinivas@emc.com provides allows
spanning tree to be controled from userspace.  Like hotplug, it
uses call_usermodehelper when spanning tree is enabled so there
is no visible API change. If call to start usermode STP fails
it falls back to existing kernel STP.
Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>

net/bridge/br_if.c

@@ -203,7 +203,7 @@ static struct net_device *new_bridge_dev(const char *name)
 	memcpy(br->group_addr, br_group_address, ETH_ALEN);
 
 	br->feature_mask = dev->features;
-	br->stp_enabled = 0;
+	br->stp_enabled = BR_NO_STP;
 	br->designated_root = br->bridge_id;
 	br->root_path_cost = 0;
 	br->root_port = 0;

net/bridge/br_ioctl.c

@@ -137,7 +137,8 @@ static int old_dev_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
 		b.topology_change = br->topology_change;
 		b.topology_change_detected = br->topology_change_detected;
 		b.root_port = br->root_port;
-		b.stp_enabled = br->stp_enabled;
+
+		b.stp_enabled = (br->stp_enabled != BR_NO_STP);
 		b.ageing_time = jiffies_to_clock_t(br->ageing_time);
 		b.hello_timer_value = br_timer_value(&br->hello_timer);
 		b.tcn_timer_value = br_timer_value(&br->tcn_timer);
@@ -251,7 +252,7 @@ static int old_dev_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
 		if (!capable(CAP_NET_ADMIN))
 			return -EPERM;
 
-		br->stp_enabled = args[1]?1:0;
+		br_stp_set_enabled(br, args[1]);
 		return 0;
 
 	case BRCTL_SET_BRIDGE_PRIORITY:

net/bridge/br_netlink.c

@@ -165,7 +165,7 @@ static int br_rtm_setlink(struct sk_buff *skb,  struct nlmsghdr *nlh, void *arg)
 		return -EINVAL;
 
 	/* if kernel STP is running, don't allow changes */
-	if (p->br->stp_enabled)
+	if (p->br->stp_enabled == BR_KERNEL_STP)
 		return -EBUSY;
 
 	if (!netif_running(dev) ||

net/bridge/br_private.h

@@ -26,7 +26,10 @@
 #define BR_PORT_BITS	10
 #define BR_MAX_PORTS	(1<<BR_PORT_BITS)
 
-#define BR_VERSION	"2.2"
+#define BR_VERSION	"2.3"
+
+/* Path to usermode spanning tree program */
+#define BR_STP_PROG	"/sbin/bridge-stp"
 
 typedef struct bridge_id bridge_id;
 typedef struct mac_addr mac_addr;
@@ -107,7 +110,13 @@ struct net_bridge
 
 	u8				group_addr[ETH_ALEN];
 	u16				root_port;
-	unsigned char			stp_enabled;
+
+	enum {
+		BR_NO_STP, 		/* no spanning tree */
+		BR_KERNEL_STP,		/* old STP in kernel */
+		BR_USER_STP,		/* new RSTP in userspace */
+	} stp_enabled;
+
 	unsigned char			topology_change;
 	unsigned char			topology_change_detected;
 
@@ -127,7 +136,6 @@ static inline int br_is_root_bridge(const struct net_bridge *br)
 	return !memcmp(&br->bridge_id, &br->designated_root, 8);
 }
 
-
 /* br_device.c */
 extern void br_dev_setup(struct net_device *dev);
 extern int br_dev_xmit(struct sk_buff *skb, struct net_device *dev);
@@ -209,6 +217,7 @@ extern void br_become_designated_port(struct net_bridge_port *p);
 /* br_stp_if.c */
 extern void br_stp_enable_bridge(struct net_bridge *br);
 extern void br_stp_disable_bridge(struct net_bridge *br);
+extern void br_stp_set_enabled(struct net_bridge *br, unsigned long val);
 extern void br_stp_enable_port(struct net_bridge_port *p);
 extern void br_stp_disable_port(struct net_bridge_port *p);
 extern void br_stp_recalculate_bridge_id(struct net_bridge *br);

net/bridge/br_stp.c

@@ -370,11 +370,11 @@ static void br_make_blocking(struct net_bridge_port *p)
 static void br_make_forwarding(struct net_bridge_port *p)
 {
 	if (p->state == BR_STATE_BLOCKING) {
-		if (p->br->stp_enabled) {
+		if (p->br->stp_enabled == BR_KERNEL_STP)
 			p->state = BR_STATE_LISTENING;
-		} else {
+		else
 			p->state = BR_STATE_LEARNING;
-		}
+
 		br_log_state(p);
 		mod_timer(&p->forward_delay_timer, jiffies + p->br->forward_delay);	}
 }
@@ -384,6 +384,10 @@ void br_port_state_selection(struct net_bridge *br)
 {
 	struct net_bridge_port *p;
 
+	/* Don't change port states if userspace is handling STP */
+	if (br->stp_enabled == BR_USER_STP)
+		return;
+
 	list_for_each_entry(p, &br->port_list, list) {
 		if (p->state != BR_STATE_DISABLED) {
 			if (p->port_no == br->root_port) {

net/bridge/br_stp_bpdu.c

@@ -33,9 +33,6 @@ static void br_send_bpdu(struct net_bridge_port *p,
 {
 	struct sk_buff *skb;
 
-	if (!p->br->stp_enabled)
-		return;
-
 	skb = dev_alloc_skb(length+LLC_RESERVE);
 	if (!skb)
 		return;
@@ -75,6 +72,9 @@ void br_send_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
 {
 	unsigned char buf[35];
 
+	if (p->br->stp_enabled != BR_KERNEL_STP)
+		return;
+
 	buf[0] = 0;
 	buf[1] = 0;
 	buf[2] = 0;
@@ -117,6 +117,9 @@ void br_send_tcn_bpdu(struct net_bridge_port *p)
 {
 	unsigned char buf[4];
 
+	if (p->br->stp_enabled != BR_KERNEL_STP)
+		return;
+
 	buf[0] = 0;
 	buf[1] = 0;
 	buf[2] = 0;
@@ -157,9 +160,13 @@ int br_stp_rcv(struct sk_buff *skb, struct net_device *dev,
 	br = p->br;
 	spin_lock(&br->lock);
 
-	if (p->state == BR_STATE_DISABLED
-	    || !br->stp_enabled
-	    || !(br->dev->flags & IFF_UP))
+	if (br->stp_enabled != BR_KERNEL_STP)
+		goto out;
+
+	if (!(br->dev->flags & IFF_UP))
+		goto out;
+
+	if (p->state == BR_STATE_DISABLED)
 		goto out;
 
 	if (compare_ether_addr(dest, br->group_addr) != 0)

net/bridge/br_stp_if.c

@@ -123,6 +123,62 @@ void br_stp_disable_port(struct net_bridge_port *p)
 		br_become_root_bridge(br);
 }
 
+static void br_stp_start(struct net_bridge *br)
+{
+	int r;
+	char *argv[] = { BR_STP_PROG, br->dev->name, "start", NULL };
+	char *envp[] = { NULL };
+
+	r = call_usermodehelper(BR_STP_PROG, argv, envp, 1);
+	if (r == 0) {
+		br->stp_enabled = BR_USER_STP;
+		printk(KERN_INFO "%s: userspace STP started\n", br->dev->name);
+	} else {
+		br->stp_enabled = BR_KERNEL_STP;
+		printk(KERN_INFO "%s: starting userspace STP failed, "
+				"staring kernel STP\n", br->dev->name);
+
+		/* To start timers on any ports left in blocking */
+		spin_lock_bh(&br->lock);
+		br_port_state_selection(br);
+		spin_unlock_bh(&br->lock);
+	}
+}
+
+static void br_stp_stop(struct net_bridge *br)
+{
+	int r;
+	char *argv[] = { BR_STP_PROG, br->dev->name, "stop", NULL };
+	char *envp[] = { NULL };
+
+	if (br->stp_enabled == BR_USER_STP) {
+		r = call_usermodehelper(BR_STP_PROG, argv, envp, 1);
+		printk(KERN_INFO "%s: userspace STP stopped, return code %d\n",
+			br->dev->name, r);
+
+
+		/* To start timers on any ports left in blocking */
+		spin_lock_bh(&br->lock);
+		br_port_state_selection(br);
+		spin_unlock_bh(&br->lock);
+	}
+
+	br->stp_enabled = BR_NO_STP;
+}
+
+void br_stp_set_enabled(struct net_bridge *br, unsigned long val)
+{
+	ASSERT_RTNL();
+
+	if (val) {
+		if (br->stp_enabled == BR_NO_STP)
+			br_stp_start(br);
+	} else {
+		if (br->stp_enabled != BR_NO_STP)
+			br_stp_stop(br);
+	}
+}
+
 /* called under bridge lock */
 void br_stp_change_bridge_id(struct net_bridge *br, const unsigned char *addr)
 {

net/bridge/br_sysfs_br.c

@@ -149,7 +149,9 @@ static ssize_t show_stp_state(struct device *d,
 
 static void set_stp_state(struct net_bridge *br, unsigned long val)
 {
-	br->stp_enabled = val;
+	spin_unlock_bh(&br->lock);
+	br_stp_set_enabled(br, val);
+	spin_lock_bh(&br->lock);
 }
 
 static ssize_t store_stp_state(struct device *d,