bridge: master device stuck in no-carrier state forever when in user-stp mode

When in user-stp mode, bridge master do not follow state of its slaves, so
after the following sequence of events it can stuck forever in no-carrier
state:
1) turn stp off
2) put all slaves down - master device will follow their state and also go in
no-carrier state
3) turn stp on with bridge-stp script returning 0 (go to the user-stp mode)
Now bridge master won't follow slaves' state and will never reach running
state.

This patch solves the problem by making user-stp and kernel-stp behavior
similar regarding master following slaves' states.
Signed-off-by: Vitalii Demianets <vitas@nppfactor.kiev.ua>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/br_netlink.c

@@ -18,6 +18,7 @@
 #include <net/sock.h>
 
 #include "br_private.h"
+#include "br_private_stp.h"
 
 static inline size_t br_nlmsg_size(void)
 {
@@ -188,6 +189,11 @@ static int br_rtm_setlink(struct sk_buff *skb,  struct nlmsghdr *nlh, void *arg)
 
 	p->state = new_state;
 	br_log_state(p);
+
+	spin_lock_bh(&p->br->lock);
+	br_port_state_selection(p->br);
+	spin_unlock_bh(&p->br->lock);
+
 	br_ifinfo_notify(RTM_NEWLINK, p);
 
 	return 0;

net/bridge/br_stp.c

@@ -399,25 +399,24 @@ void br_port_state_selection(struct net_bridge *br)
 	struct net_bridge_port *p;
 	unsigned int liveports = 0;
 
-	/* 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)
 			continue;
 
-		if (p->port_no == br->root_port) {
-			p->config_pending = 0;
-			p->topology_change_ack = 0;
-			br_make_forwarding(p);
-		} else if (br_is_designated_port(p)) {
-			del_timer(&p->message_age_timer);
-			br_make_forwarding(p);
-		} else {
-			p->config_pending = 0;
-			p->topology_change_ack = 0;
-			br_make_blocking(p);
+		/* Don't change port states if userspace is handling STP */
+		if (br->stp_enabled != BR_USER_STP) {
+			if (p->port_no == br->root_port) {
+				p->config_pending = 0;
+				p->topology_change_ack = 0;
+				br_make_forwarding(p);
+			} else if (br_is_designated_port(p)) {
+				del_timer(&p->message_age_timer);
+				br_make_forwarding(p);
+			} else {
+				p->config_pending = 0;
+				p->topology_change_ack = 0;
+				br_make_blocking(p);
+			}
 		}
 
 		if (p->state == BR_STATE_FORWARDING)