[Bridge] [PATCH net-next v2] bridge: fix hello and hold timers starting/stopping

[Bridge] [PATCH net-next v2] bridge: fix hello and hold timers starting/stopping

[Ivan Vecera]

Current bridge code incorrectly handles starting/stopping of hello and
hold timers during STP enable/disable.

1. Timers are stopped in br_stp_start() during NO_STP->USER_STP
   transition. The timers are already stopped in NO_STP state so
   this is confusing no-op.

2. During USER_STP->NO_STP transition the timers are started. This
   does not make sense and is confusion because the timer should not be
   active in NO_STP state.

Cc: davem@davemloft.net
Cc: sashok@cumulusnetworks.com
Cc: stephen@networkplumber.org
Cc: bridge@lists.linux-foundation.org
Cc: lucien.xin@gmail.com
Cc: nikolay@cumulusnetworks.com
Signed-off-by: Ivan Vecera <cera@cera.cz>
---
 net/bridge/br_stp_if.c | 11 -----------
 1 file changed, 11 deletions(-)

diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
index 08341d2aa9c9..a05027027513 100644
--- a/net/bridge/br_stp_if.c
+++ b/net/bridge/br_stp_if.c
@@ -150,7 +150,6 @@ static int br_stp_call_user(struct net_bridge *br, char *arg)
 
 static void br_stp_start(struct net_bridge *br)
 {
-	struct net_bridge_port *p;
 	int err = -ENOENT;
 
 	if (net_eq(dev_net(br->dev), &init_net))
@@ -169,11 +168,6 @@ static void br_stp_start(struct net_bridge *br)
 	if (!err) {
 		br->stp_enabled = BR_USER_STP;
 		br_debug(br, "userspace STP started\n");
-
-		/* Stop hello and hold timers */
-		del_timer(&br->hello_timer);
-		list_for_each_entry(p, &br->port_list, list)
-			del_timer(&p->hold_timer);
 	} else {
 		br->stp_enabled = BR_KERNEL_STP;
 		br_debug(br, "using kernel STP\n");
@@ -187,7 +181,6 @@ static void br_stp_start(struct net_bridge *br)
 
 static void br_stp_stop(struct net_bridge *br)
 {
-	struct net_bridge_port *p;
 	int err;
 
 	if (br->stp_enabled == BR_USER_STP) {
@@ -196,10 +189,6 @@ static void br_stp_stop(struct net_bridge *br)
 			br_err(br, "failed to stop userspace STP (%d)\n", err);
 
 		/* To start timers on any ports left in blocking */
-		mod_timer(&br->hello_timer, jiffies + br->hello_time);
-		list_for_each_entry(p, &br->port_list, list)
-			mod_timer(&p->hold_timer,
-				  round_jiffies(jiffies + BR_HOLD_TIME));
 		spin_lock_bh(&br->lock);
 		br_port_state_selection(br);
 		spin_unlock_bh(&br->lock);
-- 
2.13.0

Re: [Bridge] [PATCH net-next v2] bridge: fix hello and hold timers starting/stopping

[Xin Long]

On Sat, May 20, 2017 at 1:30 AM, Ivan Vecera <cera@cera.cz> wrote:
> Current bridge code incorrectly handles starting/stopping of hello and
> hold timers during STP enable/disable.
>
> 1. Timers are stopped in br_stp_start() during NO_STP->USER_STP
>    transition. The timers are already stopped in NO_STP state so
>    this is confusing no-op.
>
> 2. During USER_STP->NO_STP transition the timers are started. This
>    does not make sense and is confusion because the timer should not be
>    active in NO_STP state.
>
> Cc: davem@davemloft.net
> Cc: sashok@cumulusnetworks.com
> Cc: stephen@networkplumber.org
> Cc: bridge@lists.linux-foundation.org
> Cc: lucien.xin@gmail.com
> Cc: nikolay@cumulusnetworks.com
> Signed-off-by: Ivan Vecera <cera@cera.cz>
Reviewed-by: Xin Long <lucien.xin@gmail.com>

> ---
>  net/bridge/br_stp_if.c | 11 -----------
>  1 file changed, 11 deletions(-)
>
> diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
> index 08341d2aa9c9..a05027027513 100644
> --- a/net/bridge/br_stp_if.c
> +++ b/net/bridge/br_stp_if.c
> @@ -150,7 +150,6 @@ static int br_stp_call_user(struct net_bridge *br, char *arg)
>
>  static void br_stp_start(struct net_bridge *br)
>  {
> -       struct net_bridge_port *p;
>         int err = -ENOENT;
>
>         if (net_eq(dev_net(br->dev), &init_net))
> @@ -169,11 +168,6 @@ static void br_stp_start(struct net_bridge *br)
>         if (!err) {
>                 br->stp_enabled = BR_USER_STP;
>                 br_debug(br, "userspace STP started\n");
> -
> -               /* Stop hello and hold timers */
> -               del_timer(&br->hello_timer);
> -               list_for_each_entry(p, &br->port_list, list)
> -                       del_timer(&p->hold_timer);
>         } else {
>                 br->stp_enabled = BR_KERNEL_STP;
>                 br_debug(br, "using kernel STP\n");
> @@ -187,7 +181,6 @@ static void br_stp_start(struct net_bridge *br)
>
>  static void br_stp_stop(struct net_bridge *br)
>  {
> -       struct net_bridge_port *p;
>         int err;
>
>         if (br->stp_enabled == BR_USER_STP) {
> @@ -196,10 +189,6 @@ static void br_stp_stop(struct net_bridge *br)
>                         br_err(br, "failed to stop userspace STP (%d)\n", err);
>
>                 /* To start timers on any ports left in blocking */
> -               mod_timer(&br->hello_timer, jiffies + br->hello_time);
> -               list_for_each_entry(p, &br->port_list, list)
> -                       mod_timer(&p->hold_timer,
> -                                 round_jiffies(jiffies + BR_HOLD_TIME));
>                 spin_lock_bh(&br->lock);
>                 br_port_state_selection(br);
>                 spin_unlock_bh(&br->lock);
> --
> 2.13.0
>

Re: [Bridge] [PATCH net-next v2] bridge: fix hello and hold timers starting/stopping

[Nikolay Aleksandrov]

On 5/19/17 8:30 PM, Ivan Vecera wrote:
> Current bridge code incorrectly handles starting/stopping of hello and
> hold timers during STP enable/disable.
> 
> 1. Timers are stopped in br_stp_start() during NO_STP->USER_STP
>     transition. The timers are already stopped in NO_STP state so
>     this is confusing no-op.
> 
> 2. During USER_STP->NO_STP transition the timers are started. This
>     does not make sense and is confusion because the timer should not be
>     active in NO_STP state.
> 
> Cc: davem@davemloft.net
> Cc: sashok@cumulusnetworks.com
> Cc: stephen@networkplumber.org
> Cc: bridge@lists.linux-foundation.org
> Cc: lucien.xin@gmail.com
> Cc: nikolay@cumulusnetworks.com
> Signed-off-by: Ivan Vecera <cera@cera.cz>
> ---
>   net/bridge/br_stp_if.c | 11 -----------
>   1 file changed, 11 deletions(-)
> 

LGTM, thanks!

Acked-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>

Re: [Bridge] [PATCH net-next v2] bridge: fix hello and hold timers starting/stopping

[Hangbin Liu]

On Fri, May 19, 2017 at 07:30:43PM +0200, Ivan Vecera wrote:
> Current bridge code incorrectly handles starting/stopping of hello and
> hold timers during STP enable/disable.
> 
> 1. Timers are stopped in br_stp_start() during NO_STP->USER_STP
>    transition. The timers are already stopped in NO_STP state so
>    this is confusing no-op.

Hi Ivan,

Shouldn't we start hello timer in br_stp_start when NO_STP -> BR_KERNEL_STP ?
> 
> 2. During USER_STP->NO_STP transition the timers are started. This
>    does not make sense and is confusion because the timer should not be
>    active in NO_STP state.

Yes, but what about BR_KERNEL_STP -> NO_STP in function br_stp_stop() ?
> 
> Cc: davem@davemloft.net
> Cc: sashok@cumulusnetworks.com
> Cc: stephen@networkplumber.org
> Cc: bridge@lists.linux-foundation.org
> Cc: lucien.xin@gmail.com
> Cc: nikolay@cumulusnetworks.com
> Signed-off-by: Ivan Vecera <cera@cera.cz>
> ---
>  net/bridge/br_stp_if.c | 11 -----------
>  1 file changed, 11 deletions(-)
> 
> diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
> index 08341d2aa9c9..a05027027513 100644
> --- a/net/bridge/br_stp_if.c
> +++ b/net/bridge/br_stp_if.c
> @@ -150,7 +150,6 @@ static int br_stp_call_user(struct net_bridge *br, char *arg)
>  
>  static void br_stp_start(struct net_bridge *br)
>  {
> -	struct net_bridge_port *p;
>  	int err = -ENOENT;
>  
>  	if (net_eq(dev_net(br->dev), &init_net))
> @@ -169,11 +168,6 @@ static void br_stp_start(struct net_bridge *br)
>  	if (!err) {
>  		br->stp_enabled = BR_USER_STP;
>  		br_debug(br, "userspace STP started\n");
> -
> -		/* Stop hello and hold timers */
> -		del_timer(&br->hello_timer);
> -		list_for_each_entry(p, &br->port_list, list)
> -			del_timer(&p->hold_timer);

I'm not sure if user space daemon will send bpdu or not? In comment
76b91c32dd86 ("bridge: stp: when using userspace stp stop kernel hello and
hold timers"). Nikolay said we should not handle it with BR_USER_STP.

>  	} else {
>  		br->stp_enabled = BR_KERNEL_STP;
>  		br_debug(br, "using kernel STP\n");
> @@ -187,7 +181,6 @@ static void br_stp_start(struct net_bridge *br)
>  
>  static void br_stp_stop(struct net_bridge *br)
>  {
> -	struct net_bridge_port *p;
>  	int err;
>  
>  	if (br->stp_enabled == BR_USER_STP) {
> @@ -196,10 +189,6 @@ static void br_stp_stop(struct net_bridge *br)
>  			br_err(br, "failed to stop userspace STP (%d)\n", err);
>  
>  		/* To start timers on any ports left in blocking */
> -		mod_timer(&br->hello_timer, jiffies + br->hello_time);
> -		list_for_each_entry(p, &br->port_list, list)
> -			mod_timer(&p->hold_timer,
> -				  round_jiffies(jiffies + BR_HOLD_TIME));

If we do not del hello_timer. after it expired in br_hello_timer_expired(),
Our state is br->dev->flags & IFF_UP and br->stp_enabled == NO_STP, it will
call mod_timer(&br->hello_timer, round_jiffies(jiffies + br->hello_time))
and we will keep sending bpdu message even after stp stoped.

>  		spin_lock_bh(&br->lock);
>  		br_port_state_selection(br);
>  		spin_unlock_bh(&br->lock);
> -- 

So how about just like

diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
index d8ad73b..0198f62 100644
--- a/net/bridge/br_stp_if.c
+++ b/net/bridge/br_stp_if.c
@@ -183,6 +183,7 @@ static void br_stp_start(struct net_bridge *br)
        } else {
                br->stp_enabled = BR_KERNEL_STP;
                br_debug(br, "using kernel STP\n");
+               mod_timer(&br->hello_timer, jiffies + br->hello_time);

                /* To start timers on any ports left in blocking */
                br_port_state_selection(br);
@@ -202,7 +203,6 @@ static void br_stp_stop(struct net_bridge *br)
                        br_err(br, "failed to stop userspace STP (%d)\n", err);

                /* To start timers on any ports left in blocking */
-               mod_timer(&br->hello_timer, jiffies + br->hello_time);
                list_for_each_entry(p, &br->port_list, list)
                        mod_timer(&p->hold_timer,
                                  round_jiffies(jiffies + BR_HOLD_TIME));
@@ -211,6 +211,7 @@ static void br_stp_stop(struct net_bridge *br)
                spin_unlock_bh(&br->lock);
        }

+       del_timer_sync(&br->hello_timer);
        br->stp_enabled = BR_NO_STP;
 }

Thanks
Hangbin

Re: [Bridge] [PATCH net-next v2] bridge: fix hello and hold timers starting/stopping

[Nikolay Aleksandrov]

On 5/20/17 8:57 AM, Hangbin Liu wrote:
> On Fri, May 19, 2017 at 07:30:43PM +0200, Ivan Vecera wrote:
>> Current bridge code incorrectly handles starting/stopping of hello and
>> hold timers during STP enable/disable.
>>
>> 1. Timers are stopped in br_stp_start() during NO_STP->USER_STP
>>     transition. The timers are already stopped in NO_STP state so
>>     this is confusing no-op.
> 
> Hi Ivan,
> 
> Shouldn't we start hello timer in br_stp_start when NO_STP -> BR_KERNEL_STP ?

Please see Xin Long's recent -net patch that fixes exactly this issue.
It will answer your questions below, too.

https://patchwork.ozlabs.org/patch/764685/

>>
>> 2. During USER_STP->NO_STP transition the timers are started. This
>>     does not make sense and is confusion because the timer should not be
>>     active in NO_STP state.
> 
> Yes, but what about BR_KERNEL_STP -> NO_STP in function br_stp_stop() ?
>>
>> Cc: davem@davemloft.net
>> Cc: sashok@cumulusnetworks.com
>> Cc: stephen@networkplumber.org
>> Cc: bridge@lists.linux-foundation.org
>> Cc: lucien.xin@gmail.com
>> Cc: nikolay@cumulusnetworks.com
>> Signed-off-by: Ivan Vecera <cera@cera.cz>
>> ---
>>   net/bridge/br_stp_if.c | 11 -----------
>>   1 file changed, 11 deletions(-)
>>
>> diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
>> index 08341d2aa9c9..a05027027513 100644
>> --- a/net/bridge/br_stp_if.c
>> +++ b/net/bridge/br_stp_if.c
>> @@ -150,7 +150,6 @@ static int br_stp_call_user(struct net_bridge *br, char *arg)
>>   
>>   static void br_stp_start(struct net_bridge *br)
>>   {
>> -	struct net_bridge_port *p;
>>   	int err = -ENOENT;
>>   
>>   	if (net_eq(dev_net(br->dev), &init_net))
>> @@ -169,11 +168,6 @@ static void br_stp_start(struct net_bridge *br)
>>   	if (!err) {
>>   		br->stp_enabled = BR_USER_STP;
>>   		br_debug(br, "userspace STP started\n");
>> -
>> -		/* Stop hello and hold timers */
>> -		del_timer(&br->hello_timer);
>> -		list_for_each_entry(p, &br->port_list, list)
>> -			del_timer(&p->hold_timer);
> 
> I'm not sure if user space daemon will send bpdu or not? In comment
> 76b91c32dd86 ("bridge: stp: when using userspace stp stop kernel hello and
> hold timers"). Nikolay said we should not handle it with BR_USER_STP >
>>   	} else {
>>   		br->stp_enabled = BR_KERNEL_STP;
>>   		br_debug(br, "using kernel STP\n");
>> @@ -187,7 +181,6 @@ static void br_stp_start(struct net_bridge *br)
>>   
>>   static void br_stp_stop(struct net_bridge *br)
>>   {
>> -	struct net_bridge_port *p;
>>   	int err;
>>   
>>   	if (br->stp_enabled == BR_USER_STP) {
>> @@ -196,10 +189,6 @@ static void br_stp_stop(struct net_bridge *br)
>>   			br_err(br, "failed to stop userspace STP (%d)\n", err);
>>   
>>   		/* To start timers on any ports left in blocking */
>> -		mod_timer(&br->hello_timer, jiffies + br->hello_time);
>> -		list_for_each_entry(p, &br->port_list, list)
>> -			mod_timer(&p->hold_timer,
>> -				  round_jiffies(jiffies + BR_HOLD_TIME));
> 
> If we do not del hello_timer. after it expired in br_hello_timer_expired(),
> Our state is br->dev->flags & IFF_UP and br->stp_enabled == NO_STP, it will
> call mod_timer(&br->hello_timer, round_jiffies(jiffies + br->hello_time))
> and we will keep sending bpdu message even after stp stoped.

Again see Xin Long's recent -net patch.

> 
>>   		spin_lock_bh(&br->lock);
>>   		br_port_state_selection(br);
>>   		spin_unlock_bh(&br->lock);
>> -- 
> 
> So how about just like
> 
> diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
> index d8ad73b..0198f62 100644
> --- a/net/bridge/br_stp_if.c
> +++ b/net/bridge/br_stp_if.c
> @@ -183,6 +183,7 @@ static void br_stp_start(struct net_bridge *br)
>          } else {
>                  br->stp_enabled = BR_KERNEL_STP;
>                  br_debug(br, "using kernel STP\n");
> +               mod_timer(&br->hello_timer, jiffies + br->hello_time);
> 
>                  /* To start timers on any ports left in blocking */
>                  br_port_state_selection(br);
> @@ -202,7 +203,6 @@ static void br_stp_stop(struct net_bridge *br)
>                          br_err(br, "failed to stop userspace STP (%d)\n", err);
> 
>                  /* To start timers on any ports left in blocking */
> -               mod_timer(&br->hello_timer, jiffies + br->hello_time);
>                  list_for_each_entry(p, &br->port_list, list)
>                          mod_timer(&p->hold_timer,
>                                    round_jiffies(jiffies + BR_HOLD_TIME));
> @@ -211,6 +211,7 @@ static void br_stp_stop(struct net_bridge *br)
>                  spin_unlock_bh(&br->lock);
>          }
> 
> +       del_timer_sync(&br->hello_timer);
>          br->stp_enabled = BR_NO_STP;
>   }
> 
> Thanks
> Hangbin
> 

Re: [Bridge] [PATCH net-next v2] bridge: fix hello and hold timers starting/stopping

[Ivan Vecera]

2017-05-20 7:57 GMT+02:00 Hangbin Liu <liuhangbin@gmail.com>:
> On Fri, May 19, 2017 at 07:30:43PM +0200, Ivan Vecera wrote:
>> Current bridge code incorrectly handles starting/stopping of hello and
>> hold timers during STP enable/disable.
>>
>> 1. Timers are stopped in br_stp_start() during NO_STP->USER_STP
>>    transition. The timers are already stopped in NO_STP state so
>>    this is confusing no-op.
>
> Hi Ivan,
>
> Shouldn't we start hello timer in br_stp_start when NO_STP -> BR_KERNEL_STP ?

As Nikolay mentioned, this is fixed by
https://patchwork.ozlabs.org/patch/764685/

>>
>> 2. During USER_STP->NO_STP transition the timers are started. This
>>    does not make sense and is confusion because the timer should not be
>>    active in NO_STP state.
>
> Yes, but what about BR_KERNEL_STP -> NO_STP in function br_stp_stop() ?

The timer is lazily stopped by itself in its handler... or not rearmed
respectively.

>> Cc: davem@davemloft.net
>> Cc: sashok@cumulusnetworks.com
>> Cc: stephen@networkplumber.org
>> Cc: bridge@lists.linux-foundation.org
>> Cc: lucien.xin@gmail.com
>> Cc: nikolay@cumulusnetworks.com
>> Signed-off-by: Ivan Vecera <cera@cera.cz>
>> ---
>>  net/bridge/br_stp_if.c | 11 -----------
>>  1 file changed, 11 deletions(-)
>>
>> diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
>> index 08341d2aa9c9..a05027027513 100644
>> --- a/net/bridge/br_stp_if.c
>> +++ b/net/bridge/br_stp_if.c
>> @@ -150,7 +150,6 @@ static int br_stp_call_user(struct net_bridge *br, char *arg)
>>
>>  static void br_stp_start(struct net_bridge *br)
>>  {
>> -     struct net_bridge_port *p;
>>       int err = -ENOENT;
>>
>>       if (net_eq(dev_net(br->dev), &init_net))
>> @@ -169,11 +168,6 @@ static void br_stp_start(struct net_bridge *br)
>>       if (!err) {
>>               br->stp_enabled = BR_USER_STP;
>>               br_debug(br, "userspace STP started\n");
>> -
>> -             /* Stop hello and hold timers */
>> -             del_timer(&br->hello_timer);
>> -             list_for_each_entry(p, &br->port_list, list)
>> -                     del_timer(&p->hold_timer);
>
> I'm not sure if user space daemon will send bpdu or not? In comment
> 76b91c32dd86 ("bridge: stp: when using userspace stp stop kernel hello and
> hold timers"). Nikolay said we should not handle it with BR_USER_STP.
>
>>       } else {
>>               br->stp_enabled = BR_KERNEL_STP;
>>               br_debug(br, "using kernel STP\n");
>> @@ -187,7 +181,6 @@ static void br_stp_start(struct net_bridge *br)
>>
>>  static void br_stp_stop(struct net_bridge *br)
>>  {
>> -     struct net_bridge_port *p;
>>       int err;
>>
>>       if (br->stp_enabled == BR_USER_STP) {
>> @@ -196,10 +189,6 @@ static void br_stp_stop(struct net_bridge *br)
>>                       br_err(br, "failed to stop userspace STP (%d)\n", err);
>>
>>               /* To start timers on any ports left in blocking */
>> -             mod_timer(&br->hello_timer, jiffies + br->hello_time);
>> -             list_for_each_entry(p, &br->port_list, list)
>> -                     mod_timer(&p->hold_timer,
>> -                               round_jiffies(jiffies + BR_HOLD_TIME));
>
> If we do not del hello_timer. after it expired in br_hello_timer_expired(),
> Our state is br->dev->flags & IFF_UP and br->stp_enabled == NO_STP, it will
> call mod_timer(&br->hello_timer, round_jiffies(jiffies + br->hello_time))
> and we will keep sending bpdu message even after stp stoped.
>
>>               spin_lock_bh(&br->lock);
>>               br_port_state_selection(br);
>>               spin_unlock_bh(&br->lock);
>> --
>
> So how about just like
>
> diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
> index d8ad73b..0198f62 100644
> --- a/net/bridge/br_stp_if.c
> +++ b/net/bridge/br_stp_if.c
> @@ -183,6 +183,7 @@ static void br_stp_start(struct net_bridge *br)
>         } else {
>                 br->stp_enabled = BR_KERNEL_STP;
>                 br_debug(br, "using kernel STP\n");
> +               mod_timer(&br->hello_timer, jiffies + br->hello_time);
>
>                 /* To start timers on any ports left in blocking */
>                 br_port_state_selection(br);
> @@ -202,7 +203,6 @@ static void br_stp_stop(struct net_bridge *br)
>                         br_err(br, "failed to stop userspace STP (%d)\n", err);
>
>                 /* To start timers on any ports left in blocking */
> -               mod_timer(&br->hello_timer, jiffies + br->hello_time);
>                 list_for_each_entry(p, &br->port_list, list)
>                         mod_timer(&p->hold_timer,
>                                   round_jiffies(jiffies + BR_HOLD_TIME));
> @@ -211,6 +211,7 @@ static void br_stp_stop(struct net_bridge *br)
>                 spin_unlock_bh(&br->lock);
>         }
>
> +       del_timer_sync(&br->hello_timer);
>         br->stp_enabled = BR_NO_STP;
>  }
>
> Thanks
> Hangbin

Re: [Bridge] [PATCH net-next v2] bridge: fix hello and hold timers starting/stopping

[Hangbin Liu]

On Sat, May 20, 2017 at 09:06:16AM +0200, Ivan Vecera wrote:
> 2017-05-20 7:57 GMT+02:00 Hangbin Liu <liuhangbin@gmail.com>:
> > On Fri, May 19, 2017 at 07:30:43PM +0200, Ivan Vecera wrote:
> >> Current bridge code incorrectly handles starting/stopping of hello and
> >> hold timers during STP enable/disable.
> >>
> >> 1. Timers are stopped in br_stp_start() during NO_STP->USER_STP
> >>    transition. The timers are already stopped in NO_STP state so
> >>    this is confusing no-op.
> >
> > Hi Ivan,
> >
> > Shouldn't we start hello timer in br_stp_start when NO_STP -> BR_KERNEL_STP ?
> 
> As Nikolay mentioned, this is fixed by
> https://patchwork.ozlabs.org/patch/764685/

Ah, sorry. My mistake. I only saw xin's patch and your v2 patch. So I mixed
them up and thought this is xin's V2 patch. That's why I wonder we didn't
start hello timer in br_stp_start...

Now I see your v1 patch with:

The patch is a follow-up for "bridge: start hello_timer when enabling
KERNEL_STP in br_stp_start" patch from Xin Long."

Sorry for mixed them up.
> 
> >>
> >> 2. During USER_STP->NO_STP transition the timers are started. This
> >>    does not make sense and is confusion because the timer should not be
> >>    active in NO_STP state.
> >
> > Yes, but what about BR_KERNEL_STP -> NO_STP in function br_stp_stop() ?
> 
> The timer is lazily stopped by itself in its handler... or not rearmed
> respectively.

Yes, with xin's patch this timer will stoped by itself.

Thanks
Hangbin

Re: [Bridge] [PATCH net-next v2] bridge: fix hello and hold timers starting/stopping

[David Miller]

From: Ivan Vecera <cera@cera.cz>
Date: Fri, 19 May 2017 19:30:43 +0200

> Current bridge code incorrectly handles starting/stopping of hello and
> hold timers during STP enable/disable.
> 
> 1. Timers are stopped in br_stp_start() during NO_STP->USER_STP
>    transition. The timers are already stopped in NO_STP state so
>    this is confusing no-op.
> 
> 2. During USER_STP->NO_STP transition the timers are started. This
>    does not make sense and is confusion because the timer should not be
>    active in NO_STP state.
> 
> Cc: davem@davemloft.net
> Cc: sashok@cumulusnetworks.com
> Cc: stephen@networkplumber.org
> Cc: bridge@lists.linux-foundation.org
> Cc: lucien.xin@gmail.com
> Cc: nikolay@cumulusnetworks.com
> Signed-off-by: Ivan Vecera <cera@cera.cz>

Applied.