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>

1 files changed, 56 insertions, 0 deletions

diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
index a285897..1c1806d 100644
--- a/net/bridge/br_stp_if.c
+++ b/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)
 {