Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Wed, 6 Jul 2022 16:28:34 +0300
From:   Vladimir Oltean <olteanv@gmail.com>
To:     Hans S <schultz.hans@gmail.com>
Cc:     "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>, netdev@vger.kernel.org,
        Hans Schultz <schultz.hans+netdev@gmail.com>,
        Andrew Lunn <andrew@lunn.ch>,
        Vivien Didelot <vivien.didelot@gmail.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>, Jiri Pirko <jiri@resnulli.us>,
        Ivan Vecera <ivecera@redhat.com>,
        Roopa Prabhu <roopa@nvidia.com>,
        Nikolay Aleksandrov <razor@blackwall.org>,
        Shuah Khan <shuah@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Ido Schimmel <idosch@nvidia.com>, linux-kernel@vger.kernel.org,
        bridge@lists.linux-foundation.org, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH V3 net-next 3/4] net: dsa: mv88e6xxx: mac-auth/MAB
 implementation
Message-ID: <20220706132834.rdw7mmpbwt55kt4r@skbuf>
References: <20220524152144.40527-1-schultz.hans+netdev@gmail.com>
 <20220524152144.40527-4-schultz.hans+netdev@gmail.com>
 <20220627180557.xnxud7d6ol22lexb@skbuf>
 <CAKUejP7ugMB9d3MVX3m9Brw12_ocFoT+nuJJucYdQH70kzC7=w@mail.gmail.com>
 <CAKUejP5u9rrH8tODODG0a1PLXfLhk7NLe5LUYkefkbs15uU=BQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAKUejP5u9rrH8tODODG0a1PLXfLhk7NLe5LUYkefkbs15uU=BQ@mail.gmail.com>
Precedence: bulk

On Tue, Jul 05, 2022 at 05:05:52PM +0200, Hans S wrote:
> Hi, does anybody know what it going on with this variable?
> struct dsa_port *dp ->ageing_time;
> 
> I experience that it changes value like a factor ~10 at times.

Could you be a bit more specific? Are you talking about STP Topology
Change Notification BPDUs, which trigger this code path?

diff --git a/net/bridge/br_stp.c b/net/bridge/br_stp.c
index 7d27b2e6038f..9b25bc2dcb3e 100644
--- a/net/bridge/br_stp.c
+++ b/net/bridge/br_stp.c
@@ -671,10 +671,10 @@ void __br_set_topology_change(struct net_bridge *br, unsigned char val)
 
 		if (val) {
 			t = 2 * br->forward_delay;
-			br_debug(br, "decreasing ageing time to %lu\n", t);
+			br_info(br, "decreasing ageing time to %lu\n", t);
 		} else {
 			t = br->bridge_ageing_time;
-			br_debug(br, "restoring ageing time to %lu\n", t);
+			br_info(br, "restoring ageing time to %lu\n", t);
 		}
 
 		err = __set_ageing_time(br->dev, t);

Coincidentally the default values of 2 * br->forward_delay and br->bridge_ageing_time
are 1 order of magnitude apart from each other.

[  139.998310] br0: topology change detected, propagating
[  140.003490] br0: decreasing ageing time to 3000
[  175.193054] br0: restoring ageing time to 30000

What's the problem anyway?