Vladimir Oltean
2022-Jul-17 12:57 UTC
[Bridge] [PATCH v4 net-next 3/6] drivers: net: dsa: add locked fdb entry flag to drivers
On Sun, Jul 17, 2022 at 02:21:47PM +0200, netdev at kapio-technology.com wrote:> On 2022-07-13 14:39, Ido Schimmel wrote: > > On Wed, Jul 13, 2022 at 09:09:58AM +0200, netdev at kapio-technology.com > > wrote: > > > > > What are "Storm Prevention" and "zero-DPV" FDB entries? > > They are both FDB entries that at the HW level drops all packets having a > specific SA, thus using minimum resources. > (thus the name "Storm Prevention" aka, protection against DOS attacks. We > must remember that we operate with CPU based learning.)DPV means Destination Port Vector, and an ATU entry with a DPV of 0 essentially means a FDB entry pointing nowhere, so it will drop the packet. That's a slight problem with Hans' implementation, the bridge thinks that the locked FDB entry belongs to port X, but in reality it matches on all bridged ports (since it matches by FID). FID allocation in mv88e6xxx is slightly strange, all VLAN-unaware bridge ports, belonging to any bridge, share the same FID, so the FDB databases are not exactly isolated from each other.
netdev at kapio-technology.com
2022-Jul-17 13:09 UTC
[Bridge] [PATCH v4 net-next 3/6] drivers: net: dsa: add locked fdb entry flag to drivers
On 2022-07-17 14:57, Vladimir Oltean wrote:> On Sun, Jul 17, 2022 at 02:21:47PM +0200, netdev at kapio-technology.com > wrote: >> On 2022-07-13 14:39, Ido Schimmel wrote: >> > On Wed, Jul 13, 2022 at 09:09:58AM +0200, netdev at kapio-technology.com >> > wrote: >> >> > >> > What are "Storm Prevention" and "zero-DPV" FDB entries? >> >> They are both FDB entries that at the HW level drops all packets >> having a >> specific SA, thus using minimum resources. >> (thus the name "Storm Prevention" aka, protection against DOS attacks. >> We >> must remember that we operate with CPU based learning.) > > DPV means Destination Port Vector, and an ATU entry with a DPV of 0 > essentially means a FDB entry pointing nowhere, so it will drop the > packet. That's a slight problem with Hans' implementation, the bridge > thinks that the locked FDB entry belongs to port X, but in reality it > matches on all bridged ports (since it matches by FID). FID allocation > in mv88e6xxx is slightly strange, all VLAN-unaware bridge ports, > belonging to any bridge, share the same FID, so the FDB databases are > not exactly isolated from each other.But if the locked port is vlan aware and has a pvid, it should not block other ports. Besides the fid will be zero with vlan unaware afaik, and all with zero fid do not create locked entries.