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

On 5/20/17 8:57 AM, Hangbin Liu wrote:

On Fri, May 19, 2017 at 07:30:43PM +0200, Ivan Vecera wrote:

quoted

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/

quoted

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() ?

quoted

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 <redacted>
---
  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 >

quoted

  	} 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.