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Message-ID: <20220330085154.34440715@kernel.org> Date: Wed, 30 Mar 2022 08:51:54 -0700 From: Jakub Kicinski <kuba@...nel.org> To: Alexandra Winter <wintera@...ux.ibm.com>, Nikolay Aleksandrov <razor@...ckwall.org> Cc: "David S. Miller" <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>, Hangbin Liu <liuhangbin@...il.com>, netdev@...r.kernel.org, linux-s390@...r.kernel.org, Heiko Carstens <hca@...ux.ibm.com>, Roopa Prabhu <roopa@...dia.com>, bridge@...ts.linux-foundation.org, Ido Schimmel <idosch@...dia.com>, Jiri Pirko <jiri@...dia.com>, Jay Vosburgh <j.vosburgh@...il.com> Subject: Re: [PATCH net-next v2] veth: Support bonding events On Wed, 30 Mar 2022 13:14:12 +0200 Alexandra Winter wrote: > >> This patch in no way addresses (2). But then, again, if we put > >> a macvlan on top of a bridge master it will shotgun its GARPS all > >> the same. So it's not like veth would be special in that regard. > >> > >> Nik, what am I missing? > > > > If we're talking about macvlan -> bridge -> bond then the bond flap's > > notify peers shouldn't reach the macvlan. Hm, right. I'm missing a step in my understanding. As you say bridge does not seem to be re-broadcasting the event to its master. So how does Alexandra catch this kind of an event? :S case NETDEV_NOTIFY_PEERS: /* propagate to peer of a bridge attached veth */ if (netif_is_bridge_master(dev)) { IIUC bond will notify with dev == bond netdev. Where is the event with dev == br generated? > > Generally broadcast traffic > > is quite expensive for the bridge, I have patches that improve on the > > technical side (consider ports only for the same bcast domain), but you also > > wouldn't want unnecessary bcast packets being sent around. :) > > There are setups with tens of bond devices and propagating that to all would be > > very expensive, but most of all unnecessary. It would also hurt setups with > > a lot of vlan devices on the bridge. There are setups with hundreds of vlans > > and hundreds of macvlans on top, propagating it up would send it to all of > > them and that wouldn't scale at all, these mostly have IP addresses too. Ack. > > Perhaps we can enable propagation on a per-port or per-bridge basis, then we > > can avoid these walks. That is, make it opt-in. Maybe opt-out? But assuming the event is only generated on active/backup switch over - when would it be okay to ignore the notification? > >>> It also seems difficult to avoid re-bouncing the notifier. > >> > >> syzbot will make short work of this patch, I think the potential > >> for infinite loops has to be addressed somehow. IIUC this is the > >> first instance of forwarding those notifiers to a peer rather > >> than within a upper <> lower device hierarchy which is a DAG. > > My concern was about the Hangbin's alternative proposal to notify all > bridge ports. I hope in my porposal I was able to avoid infinite loops. Possibly I'm confused as to where the notification for bridge master gets sent..
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