Re: [Bridge] [PATCH net-next 0/6] net: bridge: add flush filtering support

[Ido Schimmel <idosch@idosch.org>]

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
$ 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
>