From ef647f1300d69adb8223d970554d59d7e244db6d Mon Sep 17 00:00:00 2001 From: Stephen Hemminger Date: Tue, 5 Aug 2008 18:42:51 -0700 Subject: bridge: Eliminate unnecessary forward delay From: Stephen Hemminger Based upon original patch by Herbert Xu, which contained the following problem description: -------------------- When the forward delay is set to zero, we still delay the setting of the forwarding state by one or possibly two timers depending on whether STP is enabled. This could either turn out to be instantaneous, or horribly slow depending on the load of the machine. As there is nothing preventing us from enabling forwarding straight away, this patch eliminates this potential delay by executing the code directly if the forward delay is zero. The effect of this problem is that immediately after the carrier comes on a port, the bridge will drop all packets received from that port until it enters forwarding mode, thus causing unnecessary packet loss. Note that this patch doesn't fully remove the delay due to the link watcher. We should also check the carrier state when we are about to drop an incoming packet because the port is disabled. But that's for another patch. -------------------- This version of the fix takes a different approach, in that it just does the state change directly. Signed-off-by: David S. Miller --- net/bridge/br_stp.c | 25 ++++++++++++++++++------- 1 file changed, 18 insertions(+), 7 deletions(-) (limited to 'net') diff --git a/net/bridge/br_stp.c b/net/bridge/br_stp.c index 921bbe5..6e63ec3 100644 --- a/net/bridge/br_stp.c +++ b/net/bridge/br_stp.c @@ -368,14 +368,25 @@ static void br_make_blocking(struct net_bridge_port *p) /* called under bridge lock */ static void br_make_forwarding(struct net_bridge_port *p) { - if (p->state == BR_STATE_BLOCKING) { - if (p->br->stp_enabled == BR_KERNEL_STP) - p->state = BR_STATE_LISTENING; - else - p->state = BR_STATE_LEARNING; + struct net_bridge *br = p->br; - br_log_state(p); - mod_timer(&p->forward_delay_timer, jiffies + p->br->forward_delay); } + if (p->state != BR_STATE_BLOCKING) + return; + + if (br->forward_delay == 0) { + p->state = BR_STATE_FORWARDING; + br_topology_change_detection(br); + del_timer(&p->forward_delay_timer); + } + else if (p->br->stp_enabled == BR_KERNEL_STP) + p->state = BR_STATE_LISTENING; + else + p->state = BR_STATE_LEARNING; + + br_log_state(p); + + if (br->forward_delay != 0) + mod_timer(&p->forward_delay_timer, jiffies + br->forward_delay); } /* called under bridge lock */ -- cgit v1.1