On 07/06/16(Tue) 12:36, Masao Uebayashi wrote: > On Mon, Jun 06, 2016 at 12:50:04PM +0200, Martin Pieuchot wrote: > > On 06/06/16(Mon) 16:23, Masao Uebayashi wrote: > > > On Mon, Jun 06, 2016 at 08:50:49AM +0200, Martin Pieuchot wrote: > > > > On 06/06/16(Mon) 13:04, Masao Uebayashi wrote: > > > > > Broadcast frame, coming into a bridge'ed interface, passes if_input() > > > > > 3 times, > > > > > and actually input (ether_input()) twice. > > > > > > > > > > - A frame enters an interface (e.g. pair(4)), the interface calls > > > > > if_input() > > > > > on it. The frame is queued in if_input_queue. > > > > > > > > > > - A task running if_input_process() is triggered. It takes the frame > > > > > and > > > > > calls bridge_input(). Frame is queued in bridgeintrq. > > > > > > > > > > - bridge_process() dispatches frame as multicast/broadcast (if > > > > > (ETHER_IS_MULTICAST())) and calls bridge_ifinput() on it, then > > > > > passes the > > > > > frame to bridgeintr_frame(). > > > > > > > > > > - bridgeintr_frame() calls bridge_broadcast() on it. > > > > > > > > > > - bridge_broadcast() calls bridge_localbroadcast(), which again calls > > > > > bridge_ifinput(). > > > > > > > > > > bridge_ifinput() is called twice for each broadcast frames. > > > > > bridge_ifinput() > > > > > calls if_input(). Thus 3 if_input() for each. > > > > > > > > > > These duplicate frames confuse pppoe(4), that's why it stops working. > > > > > > > > What do you mean by "confuse pppoe(4)"? I still don't understand what's > > > > the link between pppoe(4) and bpf(4) in this case and why BPF matters > > > > for a kernel driver. > > > > > > - PPPoE client (pppoe(4)) sends a PPPoE Discovery "initiation" frame, > > > which is > > > broadcast. > > > > > > - PPPoE server (npppd(8)) receives 3 copies of it via bpf(4), then returns > > > 3 PPPoE Discovery "offer" frames. > > > > > > - pppoe(4) receives 3 "offer" frames and gets confused ... somehow. > > > > > > I don't know the internal of pppoe(4) yet. pppoe(4) might have a bug, it > > > might be able to work even if it receives 3 replies at once, I don't know. > > > > > > I don't think that npppd(8) receiving 3 copies of broadcast frames (via > > > bpf(4)) is an intentional design anyway. > > > > I agree. Diff below should reduce the number of copies to 2. > > Diff works as expected for me, and reads me good. OK uebayasi@. > > > In order > > to remove the last copy somebody has to turn bridge_process() MP-safe > > and merge it with bridge_input(). > > > > Once this is done, bridge_input() can return "0" for multicast packets > > and ether_input() will be call directly without the need for requeueing > > the packet. > > I admit I don't fully understand the intention of if_ih_* handler. Can > you safely assume that there is always ether_input() hook just after > bridge_input()?
Since bridge(4) mostly work with Ethernet drivers, you can assume that it is after. Maybe you'll have a vlan_input() before.
