Date:   Mon, 11 Apr 2022 11:08:24 -0700
From:   Roopa Prabhu <roopa@...dia.com>
To:     Nikolay Aleksandrov <razor@...ckwall.org>, netdev@...r.kernel.org
Cc:     idosch@...sch.org, kuba@...nel.org, davem@...emloft.net,
        bridge@...ts.linux-foundation.org
Subject: Re: [PATCH net-next v2 0/8] net: bridge: add flush filtering support


On 4/11/22 10:29, Nikolay Aleksandrov wrote:
> Hi,
> This patch-set adds support to specify filtering conditions for a flush
> operation. This version has entirely different entry point (v1 had
> bridge-specific IFLA attribute, here I add new RTM_FLUSHNEIGH msg and
> netdev ndo_fdb_flush op) so I'll give a new overview altogether.
> After me and Ido discussed the feature offlist, we agreed that it would
> be best to add a new generic RTM_FLUSHNEIGH with a new ndo_fdb_flush
> callback which can be re-used for other drivers (e.g. vxlan).
> Patch 01 adds the new RTM_FLUSHNEIGH type, patch 02 then adds the
> new ndo_fdb_flush call. With this structure we need to add a generic
> rtnl_fdb_flush which will be used to do basic attribute validation and
> dispatch the call to the appropriate device based on the NTF_USE/MASTER
> flags (patch 03). Patch 04 then adds some common flush attributes which
> are used by the bridge and vxlan drivers (target ifindex, vlan id, ndm
> flags/state masks) with basic attribute validation, further validation
> can be done by the implementers of the ndo callback. Patch 05 adds a
> minimal ndo_fdb_flush to the bridge driver, it uses the current
> br_fdb_flush implementation to flush all entries similar to existing
> calls. Patch 06 adds filtering support to the new bridge flush op which
> supports target ifindex (port or bridge), vlan id and flags/state mask.
> Patch 07 converts ndm state/flags and their masks to bridge-private flags
> and fills them in the filter descriptor for matching. Finally patch 08
> fills in the target ifindex (after validating it) and vlan id (already
> validated by rtnl_fdb_flush) for matching. Flush filtering is needed
> because user-space applications need a quick way to delete only a
> specific set of entries, e.g. mlag implementations need a way to flush only
> dynamic entries excluding externally learned ones or only externally
> learned ones without static entries etc. Also apps usually want to target
> only a specific vlan or port/vlan combination. The current 2 flush
> operations (per port and bridge-wide) are not extensible and cannot
> provide such filtering.
>
> I decided against embedding new attrs into the old flush attributes for
> multiple reasons - proper error handling on unsupported attributes,
> older kernels silently flushing all, need for a second mechanism to
> signal that the attribute should be parsed (e.g. using boolopts),
> special treatment for permanent entries.
>
> Examples:
> $ bridge fdb flush dev bridge vlan 100 static
> < flush all static entries on vlan 100 >
> $ bridge fdb flush dev bridge vlan 1 dynamic
> < flush all dynamic entries on vlan 1 >
> $ bridge fdb flush dev bridge port ens16 vlan 1 dynamic
> < flush all dynamic entries on port ens16 and vlan 1 >
> $ bridge fdb flush dev ens16 vlan 1 dynamic master
> < as above: flush all dynamic entries on port ens16 and vlan 1 >
> $ bridge fdb flush dev bridge nooffloaded nopermanent self
> < flush all non-offloaded and non-permanent entries >
> $ bridge fdb flush dev bridge static noextern_learn
> < flush all static entries which are not externally learned >
> $ bridge fdb flush dev bridge permanent
> < flush all permanent entries >
> $ bridge fdb flush dev bridge port bridge permanent
> < flush all permanent entries pointing to the bridge itself >
>
> Note that all flags have their negated version (static vs nostatic etc)
> and there are some tricky cases to handle like "static" which in flag
> terms means fdbs that have NUD_NOARP but *not* NUD_PERMANENT, so the
> mask matches on both but we need only NUD_NOARP to be set. That's
> because permanent entries have both set so we can't just match on
> NUD_NOARP. Also note that this flush operation doesn't treat permanent
> entries in a special way (fdb_delete vs fdb_delete_local), it will
> delete them regardless if any port is using them. We can extend the api
> with a flag to do that if needed in the future.
>
> Patch-sets (in order):
>   - Initial flush infra and fdb flush filtering (this set)
>   - iproute2 support
>   - selftests
>
> Future work:
>   - mdb flush support (RTM_FLUSHMDB type)
>
> Thanks to Ido for the great discussion and feedback while working on this.
>
Cant we pile this on to RTM_DELNEIGH with a flush flag ?.

It is a bulk del, and sounds seems similar to the bulk dev del 
discussion on netdev a few months ago (i dont remember how that api 
ended up to be. unless i am misremembering).

neigh subsystem also needs this, curious how this api will work there.

(apologies if you guys already discussed this, did not have time to look 
through all the comments)

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