Date:   Wed, 13 Apr 2022 01:50:21 +0300
From:   Nikolay Aleksandrov <razor@...ckwall.org>
To:     netdev@...r.kernel.org
Cc:     dsahern@...nel.org, roopa@...dia.com, idosch@...sch.org,
        kuba@...nel.org, davem@...emloft.net,
        bridge@...ts.linux-foundation.org
Subject: Re: [PATCH net-next v3 0/8] net: bridge: add flush filtering support

On 4/12/22 16:22, Nikolay Aleksandrov wrote:
> Hi,
> This patch-set adds support to specify filtering conditions for a bulk
> delete (flush) operation. This version uses a new nlmsghdr delete flag
> called NLM_F_BULK in combination with a new ndo_fdb_del_bulk op which is
> used to signal that the driver supports bulk deletes (that avoids
> pushing common mac address checks to ndo_fdb_del implementations and
> also has a different prototype and parsed attribute expectations, more
> info in patch 03). The new delete flag can be used for any RTM_DEL*
> type, implementations just need to be careful with older kernels which
> are doing non-strict attribute parses. Here I use the fact that mac
> address attribute (lladdr) is mandatory in the classic fdb del case, but
> it's not allowed if bulk deleting so older kernels will error out.
> Patch 01 adds the new NLM_F_BULK delete request modifier, patch 02 then
> adds the new ndo_fdb_del_bulk call. Patch 03 adds NLM_F_BULK support to
> rtnl_fdb_del, on such request strict parsing is used only for the
> supported attributes, and if the ndo is implemented it's called, the
> NTF_SELF/MASTER rules are the same as for the standard rtnl_fdb_del.
> Patch 04 implements bridge-specific minimal ndo_fdb_del_bulk call which
> uses the current br_fdb_flush to delete all entries. Patch 05 adds
> filtering support to the new bridge flush op which supports target
> ifindex (port or bridge), vlan id and flags/state mask. Patch 06 adds
> ndm state and flags mask attributes which will be used for filtering.
> 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 >
> 
> Example of a flush call with unsupported netlink attribute (NDA_DST):
> $ bridge fdb flush dev bridge vlan 100 dynamic dst
> Error: Unsupported attribute.
> 
> Example of a flush call on an older kernel:
> $ bridge fdb flush dev bridge dynamic
> Error: invalid address.
> 
> 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.
> 
> v3: Add NLM_F_BULK delete modifier and ndo_fdb_del_bulk callback,
>      patches 01 - 03 and 06 are new. Patch 04 is changed to implement
>      bulk_del instead of flush, patches 05, 07 and 08 are adjusted to
>      use NDA_ attributes
> 
> Thanks,
>   Nik
> 
> Nikolay Aleksandrov (8):
>    net: netlink: add NLM_F_BULK delete request modifier
>    net: add ndo_fdb_del_bulk
>    net: rtnetlink: add NLM_F_BULK support to rtnl_fdb_del
>    net: bridge: fdb: add ndo_fdb_del_bulk
>    net: bridge: fdb: add support for fine-grained flushing
>    net: rtnetlink: add ndm flags and state mask attributes
>    net: bridge: fdb: add support for flush filtering based on ndm flags
>      and state
>    net: bridge: fdb: add support for flush filtering based on ifindex and
>      vlan
> 
>   include/linux/netdevice.h      |   9 ++
>   include/uapi/linux/neighbour.h |   2 +
>   include/uapi/linux/netlink.h   |   1 +
>   net/bridge/br_device.c         |   1 +
>   net/bridge/br_fdb.c            | 154 +++++++++++++++++++++++++++++++--
>   net/bridge/br_netlink.c        |   9 +-
>   net/bridge/br_private.h        |  19 +++-
>   net/bridge/br_sysfs_br.c       |   6 +-
>   net/core/rtnetlink.c           |  66 ++++++++++----
>   9 files changed, 238 insertions(+), 29 deletions(-)
> 

I realized an improvement I've missed to do in patch 08 (use port's 
ifindex when doing a bridge flush through a port and NDA_IFINDEX is not 
specified), I'll leave this set for comments and will prepare v4 with it 
and anything else that comes up in the meantime.

Thanks,
  Nik

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