On ons, maj 25, 2022 at 11:06, Nikolay Aleksandrov <razor@xxxxxxxxxxxxx> wrote: > On 24/05/2022 19:21, Hans Schultz wrote: >>> >>> Hi Hans, >>> So this approach has a fundamental problem, f->dst is changed without any synchronization >>> you cannot rely on it and thus you cannot account for these entries properly. We must be very >>> careful if we try to add any new synchronization not to affect performance as well. >>> More below... >>> >>>> @@ -319,6 +326,9 @@ static void fdb_delete(struct net_bridge *br, struct net_bridge_fdb_entry *f, >>>> if (test_bit(BR_FDB_STATIC, &f->flags)) >>>> fdb_del_hw_addr(br, f->key.addr.addr); >>>> >>>> + if (test_bit(BR_FDB_ENTRY_LOCKED, &f->flags) && !test_bit(BR_FDB_OFFLOADED, &f->flags)) >>>> + atomic_dec(&f->dst->locked_entry_cnt); >>> >>> Sorry but you cannot do this for multiple reasons: >>> - f->dst can be NULL >>> - f->dst changes without any synchronization >>> - there is no synchronization between fdb's flags and its ->dst >>> >>> Cheers, >>> Nik >> >> Hi Nik, >> >> if a port is decoupled from the bridge, the locked entries would of >> course be invalid, so maybe if adding and removing a port is accounted >> for wrt locked entries and the count of locked entries, would that not >> work? >> >> Best, >> Hans > > Hi Hans, > Unfortunately you need the correct amount of locked entries per-port if you want > to limit their number per-port, instead of globally. So you need a > consistent Hi Nik, the used dst is a port structure, so it is per-port and not globally. Best, Hans > fdb view with all its attributes when changing its dst in this case, which would > require new locking because you have multiple dependent struct fields and it will > kill roaming/learning scalability. I don't think this use case is worth the complexity it > will bring, so I'd suggest an alternative - you can monitor the number of locked entries > per-port from a user-space agent and disable port learning or some similar solution that > doesn't require any complex kernel changes. Is the limit a requirement to add the feature? > > I have an idea how to do it and to minimize the performance hit if it really is needed > but it'll add a lot of complexity which I'd like to avoid if possible. > > Cheers, > Nik
