T_XCould it be that #switchdev vs. #DSA is a bit of a mess on #Linux? I have the feeling I'm starting to get a better hang of their code, while trying to implement something in there. For instance: The Linux bridge notifies MDB additions through switchdev events. Either your switch driver can listen/react to them directly. But also DSA listens to them and can call a port_mdb_add handler which your driver registered with DSA. Some drivers are some DSA / switchdev hybrid...
Neither #switchdev nor #DSA really check if an IGMP/MLD querier exists. So if you enable #multicast snooping on these you currently also need to make sure to have an #IGMP / #MLD querier somewhere. Which is different to a classic Linux bridge, which will stop snooping optimizations if there is none, to avoid packet loss. Only for Marvell Prestera I found some mrouter-exists check via an according switchdev event. Which no other driver uses. And...
...and even this mrouter exists #switchdev event is a quite incomplete approach. What if you multicast router somehow #IGMP / #MLD querying disabled -> would break any #IPv6, even if you're not using multicast routing. What if you only have an IGMP querier? Would notify an mrouter-exists, but there's no MLD querier, so again IPv6 would be broken...
In the classic, non-DSA #Linux bridge the philosophy so far is: No matter in what combination you enable/disable multicast_snooping+ multicast_querier: The bridge ensures you don't break any network protocol, it detects per protocol family if #multicast snooping is applicable. That together with #RFC4541 I think is the only way to regain trust for #IGMP / #MLD snooping imo.
And now things like #DSA or #switchdev come along with non-foolproof solutions, diverging between each driver...
And now things like #DSA or #switchdev come along with non-foolproof solutions, diverging between each driver...
I really think #Linux kernel switch folks should make up their mind at some point if they think switch drivers should register handlers with #DSA or if they should implement a switch-case to check for various #switchdev events for the same stuff. One approach should be ditched.
Frank@T_X
No. ðŸ˜
It's called "Technologieoffenheit". 🤪