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

From: Tobias Waldekranz <[email-masked]>
Date: Tue, 15 Mar 2022 23:57:01 +0100

On Wed, Mar 16, 2022 at 00:42, Vladimir Oltean <[email-masked]> wrote:
> On Tue, Mar 15, 2022 at 11:26:59PM +0100, Tobias Waldekranz wrote:
>> On Tue, Mar 15, 2022 at 18:33, Vladimir Oltean <[email-masked]> 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 <[email-masked]>
>> >> ---
>> >
>> > 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?
>
> Ok, makes sense. So far, unoffloaded bridge ports meant that the DSA
> switch driver didn't have a ->port_bridge_join() implementation.
> Presumably that also came along with a missing ->port_fdb_add()
> implementation. So probably no NPD for the existing code paths, it is
> just your unoffloaded MST support that opens up new possibilities.
>
> Anyway, the dereference of dp->bridge first appeared in commit
> c26933639b54 ("net: dsa: request drivers to perform FDB isolation")
> which is still just in net-next.

Thanks, I just sent it separately:

https://lore.kernel.org/netdev/[email-masked]

>> >>  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
>> >>