Date:   Mon, 11 Apr 2022 11:54:34 +0300
From:   Ido Schimmel <idosch@...sch.org>
To:     Nikolay Aleksandrov <razor@...ckwall.org>
Cc:     netdev@...r.kernel.org, roopa@...dia.com, kuba@...nel.org,
        davem@...emloft.net, bridge@...ts.linux-foundation.org
Subject: Re: [PATCH net-next 0/6] net: bridge: add flush filtering support

On Mon, Apr 11, 2022 at 10:47:38AM +0300, Ido Schimmel wrote:
> On Sat, Apr 09, 2022 at 01:58:51PM +0300, Nikolay Aleksandrov wrote:
> > Hi,
> > This patch-set adds support to specify filtering conditions for a flush
> > operation. Initially only FDB flush filtering is added, later MDB
> > support will be added as well. Some user-space applications need a 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, so a new bridge af
> > attribute is added (IFLA_BRIDGE_FLUSH) which contains the filtering
> > information for each object type which has to be flushed.
> > An example structure for fdbs:
> >      [ IFLA_BRIDGE_FLUSH ]
> >       `[ BRIDGE_FDB_FLUSH ]
> >         `[ FDB_FLUSH_NDM_STATE ]
> >         `[ FDB_FLUSH_NDM_FLAGS ]
> > 
> > I decided against embedding these 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 bridge nooffloaded nopermanent
> > < 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 >
> 
> IIUC, the new IFLA_BRIDGE_FLUSH attribute is supposed to be passed in
> RTM_SETLINK messages, but the current 'bridge fdb' commands all
> correspond to RTM_{NEW,DEL,GET}NEIGH messages. To continue following
> this pattern, did you consider turning the above examples to the
> following?
> 
> $ ip link set dev bridge type bridge fdb_flush vlan 100 static
> $ ip link set dev bridge type bridge fdb_flush vlan 1 dynamic
> $ ip link set dev ens16 type bridge_slave fdb_flush vlan 1 dynamic

Thinking about it again, I guess this is more appropriate:

$ ip link set dev bridge type bridge fdb_flush port ens16 vlan 1 dynamic

> $ ip link set dev bridge type bridge fdb_flush nooffloaded nopermanent
> $ ip link set dev bridge type bridge fdb_flush static noextern_learn
> $ ip link set dev bridge type bridge fdb_flush permanent
> 
> It's not critical, but I like the correspondence between iproute2
> commands and the underlying netlink messages.
> 
> > 
> > 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.
> > 
> > Patches in this set:
> >  1. adds the new IFLA_BRIDGE_FLUSH bridge af attribute
> >  2. adds a basic structure to describe an fdb flush filter
> >  3. adds fdb netlink flush call via BRIDGE_FDB_FLUSH attribute
> >  4 - 6. add support for specifying various fdb fields to filter
> > 
> > Patch-sets (in order):
> >  - Initial flush infra and fdb flush filtering (this set)
> >  - iproute2 support
> >  - selftests
> > 
> > Future work:
> >  - mdb flush support
> > 
> > Thanks,
> >  Nik
> > 
> > Nikolay Aleksandrov (6):
> >   net: bridge: add a generic flush operation
> >   net: bridge: fdb: add support for fine-grained flushing
> >   net: bridge: fdb: add new nl attribute-based flush call
> >   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
> >   net: bridge: fdb: add support for flush filtering based on vlan id
> > 
> >  include/uapi/linux/if_bridge.h |  22 ++++++
> >  net/bridge/br_fdb.c            | 128 +++++++++++++++++++++++++++++++--
> >  net/bridge/br_netlink.c        |  59 ++++++++++++++-
> >  net/bridge/br_private.h        |  12 +++-
> >  net/bridge/br_sysfs_br.c       |   6 +-
> >  5 files changed, 215 insertions(+), 12 deletions(-)
> > 
> > -- 
> > 2.35.1
> > 

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