Re: [PATCH net-next] net: dropreason: add SKB_DROP_REASON_{BROAD,MULTI}CAST_BACKLOG

[Jakub Kicinski <kuba@kernel.org>]

On Tue, 7 Apr 2026 03:09:41 -0700 Eric Dumazet wrote:
> On Mon, Apr 6, 2026 at 6:02 PM Jakub Kicinski <kuba@kernel.org> wrote:
> > On Fri,  3 Apr 2026 02:24:43 +0000 Eric Dumazet wrote:  
> > > ipvlan and macvlan use queues to process broadcast or multicast packets
> > > from a work queue.
> > >
> > > Under attack these queues can drop packets.
> > >
> > > Add BROADCAST_BACKLOG drop_reason for macvlan broadcast queue.
> > >
> > > Add MULTICAST_BACKLOG drop_reason for ipvlan multicast queue.  
> >
> > What distinction are you trying to communicate by using BROADCAST
> > vs MULTICAST? Funny naming of the functions aside I believe that
> > in both cases we're basically dealing with multicast traffic.
> > Reading the code it seems like macvlan has some optimization where
> > it delivers the frame inline if the multicast group is not very
> > popular. And if it is popular it schedules a work (and calls that
> > broadcast). ipvlan doesn't have the inline filter and calls the
> > deliver via work multicast.
> >
> > tl;dr I think the drivers do the same thing just call their functions
> > broadcast vs multicast. Having two drop reasons here is actively
> > misleading?  
> 
> My intent was to differentiate ipvlan and macvlan reasons, some
> deployments use both.
> 
> I can rename the reasons if you think this is better.
> 
> IPVLAN_MULTICAST_BACKLOG
> 
> MACVLAN_BROADCAST_BACKLOG

Sounds better, thanks