netdev - Re: [PATCH v4 net-next 09/15] net: dsa: Never offload FDB entries on standalone ports

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Date:   Tue, 15 Mar 2022 23:26:59 +0100
From:   Tobias Waldekranz <tobias@...dekranz.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     davem@...emloft.net, kuba@...nel.org, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Ivan Vecera <ivecera@...hat.com>,
        Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        Russell King <linux@...linux.org.uk>,
        Petr Machata <petrm@...dia.com>,
        Ido Schimmel <idosch@...dia.com>,
        Matt Johnston <matt@...econstruct.com.au>,
        Cooper Lees <me@...perlees.com>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, bridge@...ts.linux-foundation.org
Subject: Re: [PATCH v4 net-next 09/15] net: dsa: Never offload FDB entries
 on standalone ports

On Tue, Mar 15, 2022 at 18:33, Vladimir Oltean <olteanv@...il.com> wrote:
> On Tue, Mar 15, 2022 at 01:25:37AM +0100, Tobias Waldekranz wrote:
>> If a port joins a bridge that it can't offload, it will fallback to
>> standalone mode and software bridging. In this case, we never want to
>> offload any FDB entries to hardware either.
>> 
>> Signed-off-by: Tobias Waldekranz <tobias@...dekranz.com>
>> ---
>
> When you resend, please send this patch separately, unless something
> breaks really ugly with your MST series in place.

Sure. I found this while testing the software fallback. It prevents a
segfault in dsa_port_bridge_host_fdb_add, which (rightly, I think)
assumes that dp->bridge is valid. I feel like this should have a Fixes:
tag, but I'm not sure which commit to blame. Any suggestions?

>>  net/dsa/slave.c | 3 +++
>>  1 file changed, 3 insertions(+)
>> 
>> diff --git a/net/dsa/slave.c b/net/dsa/slave.c
>> index a61a7c54af20..647adee97f7f 100644
>> --- a/net/dsa/slave.c
>> +++ b/net/dsa/slave.c
>> @@ -2624,6 +2624,9 @@ static int dsa_slave_fdb_event(struct net_device *dev,
>>  	if (ctx && ctx != dp)
>>  		return 0;
>>  
>> +	if (!dp->bridge)
>> +		return 0;
>> +
>>  	if (switchdev_fdb_is_dynamically_learned(fdb_info)) {
>>  		if (dsa_port_offloads_bridge_port(dp, orig_dev))
>>  			return 0;
>> -- 
>> 2.25.1
>>