[PATCH 4.4 17/53] bridge: start hello_timer when enabling KERNEL_STP in br_stp_start

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Xin Long <lucien.xin@gmail.com>


[ Upstream commit 6d18c732b95c0a9d35e9f978b4438bba15412284 ]

Since commit 76b91c32dd86 ("bridge: stp: when using userspace stp stop
kernel hello and hold timers"), bridge would not start hello_timer if
stp_enabled is not KERNEL_STP when br_dev_open.

The problem is even if users set stp_enabled with KERNEL_STP later,
the timer will still not be started. It causes that KERNEL_STP can
not really work. Users have to re-ifup the bridge to avoid this.

This patch is to fix it by starting br->hello_timer when enabling
KERNEL_STP in br_stp_start.

As an improvement, it's also to start hello_timer again only when
br->stp_enabled is KERNEL_STP in br_hello_timer_expired, there is
no reason to start the timer again when it's NO_STP.

Fixes: 76b91c32dd86 ("bridge: stp: when using userspace stp stop kernel hello and hold timers")
Reported-by: Haidong Li <haili@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Reviewed-by: Ivan Vecera <cera@cera.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/bridge/br_stp_if.c    |    1 +
 net/bridge/br_stp_timer.c |    2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

--- a/net/bridge/br_stp_if.c
+++ b/net/bridge/br_stp_if.c
@@ -166,6 +166,7 @@ static void br_stp_start(struct net_brid
 		br_debug(br, "using kernel STP\n");
 
 		/* To start timers on any ports left in blocking */
+		mod_timer(&br->hello_timer, jiffies + br->hello_time);
 		br_port_state_selection(br);
 	}
 
--- a/net/bridge/br_stp_timer.c
+++ b/net/bridge/br_stp_timer.c
@@ -40,7 +40,7 @@ static void br_hello_timer_expired(unsig
 	if (br->dev->flags & IFF_UP) {
 		br_config_bpdu_generation(br);
 
-		if (br->stp_enabled != BR_USER_STP)
+		if (br->stp_enabled == BR_KERNEL_STP)
 			mod_timer(&br->hello_timer,
 				  round_jiffies(jiffies + br->hello_time));
 	}