netdev - Re: [PATCH v3 net-next 01/14] net: bridge: mst: Multiple Spanning Tree (MST) mode

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Date:   Mon, 14 Mar 2022 13:09:05 +0200
From:   Nikolay Aleksandrov <razor@...ckwall.org>
To:     Tobias Waldekranz <tobias@...dekranz.com>, davem@...emloft.net,
        kuba@...nel.org
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Ivan Vecera <ivecera@...hat.com>,
        Roopa Prabhu <roopa@...dia.com>,
        Russell King <linux@...linux.org.uk>,
        Ido Schimmel <idosch@...dia.com>,
        Petr Machata <petrm@...dia.com>,
        Cooper Lees <me@...perlees.com>,
        Matt Johnston <matt@...econstruct.com.au>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        bridge@...ts.linux-foundation.org
Subject: Re: [PATCH v3 net-next 01/14] net: bridge: mst: Multiple Spanning
 Tree (MST) mode

On 14/03/2022 12:37, Nikolay Aleksandrov wrote:
> On 14/03/2022 11:52, Tobias Waldekranz wrote:
>> Allow the user to switch from the current per-VLAN STP mode to an MST
>> mode.
>>
>> Up to this point, per-VLAN STP states where always isolated from each
>> other. This is in contrast to the MSTP standard (802.1Q-2018, Clause
>> 13.5), where VLANs are grouped into MST instances (MSTIs), and the
>> state is managed on a per-MSTI level, rather that at the per-VLAN
>> level.
>>
>> Perhaps due to the prevalence of the standard, many switching ASICs
>> are built after the same model. Therefore, add a corresponding MST
>> mode to the bridge, which we can later add offloading support for in a
>> straight-forward way.
>>
>> For now, all VLANs are fixed to MSTI 0, also called the Common
>> Spanning Tree (CST). That is, all VLANs will follow the port-global
>> state.
>>
>> Upcoming changes will make this actually useful by allowing VLANs to
>> be mapped to arbitrary MSTIs and allow individual MSTI states to be
>> changed.
>>
>> Signed-off-by: Tobias Waldekranz <tobias@...dekranz.com>
>> ---
> [snip]
>> diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
>> index 48bc61ebc211..35b47f6b449a 100644
>> --- a/net/bridge/br_private.h
>> +++ b/net/bridge/br_private.h
>> @@ -178,6 +178,7 @@ enum {
>>   * @br_mcast_ctx: if MASTER flag set, this is the global vlan multicast context
>>   * @port_mcast_ctx: if MASTER flag unset, this is the per-port/vlan multicast
>>   *                  context
>> + * @msti: if MASTER flag set, this holds the VLANs MST instance
>>   * @vlist: sorted list of VLAN entries
>>   * @rcu: used for entry destruction
>>   *
>> @@ -210,6 +211,8 @@ struct net_bridge_vlan {
>>  		struct net_bridge_mcast_port	port_mcast_ctx;
>>  	};
>>  
>> +	u16				msti;
>> +
>>  	struct list_head		vlist;
>>  
>>  	struct rcu_head			rcu;
>> @@ -445,6 +448,7 @@ enum net_bridge_opts {
>>  	BROPT_NO_LL_LEARN,
>>  	BROPT_VLAN_BRIDGE_BINDING,
>>  	BROPT_MCAST_VLAN_SNOOPING_ENABLED,
>> +	BROPT_MST_ENABLED,
>>  };
>>  
>>  struct net_bridge {
>> @@ -1765,6 +1769,29 @@ static inline bool br_vlan_state_allowed(u8 state, bool learn_allow)
>>  }
>>  #endif
>>  
>> +/* br_mst.c */
>> +#ifdef CONFIG_BRIDGE_VLAN_FILTERING
> 
> There is already such ifdef, you can embed all MST code inside it.
> 

My bad, I somehow confused the function placement. This is good. :)

Acked-by: Nikolay Aleksandrov <razor@...ckwall.org>