Vladimir Oltean
2023-Apr-18 15:59 UTC
[Bridge] [PATCH v2 net] net: bridge: switchdev: don't notify FDB entries with "master dynamic"
There is a structural problem in switchdev, where the flag bits in struct switchdev_notifier_fdb_info (added_by_user, is_local etc) only represent a simplified / denatured view of what's in struct net_bridge_fdb_entry :: flags (BR_FDB_ADDED_BY_USER, BR_FDB_LOCAL etc). Each time we want to pass more information about struct net_bridge_fdb_entry :: flags to struct switchdev_notifier_fdb_info (here, BR_FDB_STATIC), we find that FDB entries were already notified to switchdev with no regard to this flag, and thus, switchdev drivers had no indication whether the notified entries were static or not. For example, this command: ip link add br0 type bridge && ip link set swp0 master br0 bridge fdb add dev swp0 00:01:02:03:04:05 master dynamic has never worked as intended with switchdev. It causes a struct net_bridge_fdb_entry to be passed to br_switchdev_fdb_notify() which has a single flag set: BR_FDB_ADDED_BY_USER. This is further passed to the switchdev notifier chain, where interested drivers have no choice but to assume this is a static (does not age) and sticky (does not migrate) FDB entry. So currently, all drivers offload it to hardware as such, as can be seen below ("offload" is set). bridge fdb get 00:01:02:03:04:05 dev swp0 master 00:01:02:03:04:05 dev swp0 offload master br0 The software FDB entry expires $ageing_time centiseconds after the kernel last sees a packet with this MAC SA, and the bridge notifies its deletion as well, so it eventually disappears from hardware too. This is a problem, because it is actually desirable to start offloading "master dynamic" FDB entries correctly - they should expire $ageing_time centiseconds after the *hardware* port last sees a packet with this MAC SA - and this is how the current incorrect behavior was discovered. With an offloaded data plane, it can be expected that software only sees exception path packets, so an otherwise active dynamic FDB entry would be aged out by software sooner than it should. With the change in place, these FDB entries are no longer offloaded: bridge fdb get 00:01:02:03:04:05 dev swp0 master 00:01:02:03:04:05 dev swp0 master br0 and this also constitutes a better way (assuming a backport to stable kernels) for user space to determine whether the kernel has the capability of doing something sane with these or not. As opposed to "master dynamic" FDB entries, on the current behavior of which no one currently depends on (which can be deduced from the lack of kselftests), Ido Schimmel explains that entries with the "extern_learn" flag (BR_FDB_ADDED_BY_EXT_LEARN) should still be notified to switchdev, since the spectrum driver listens to them (and this is kind of okay, because although they are treated identically to "static", they are expected to not age, and to roam). Fixes: 6b26b51b1d13 ("net: bridge: Add support for notifying devices about FDB add/del") Link: https://lore.kernel.org/netdev/20230327115206.jk5q5l753aoelwus at skbuf/ Signed-off-by: Vladimir Oltean <vladimir.oltean at nxp.com> Reviewed-by: Jesse Brandeburg <jesse.brandeburg at intel.com> --- v1->v2: let extern_learn entries still pass through to switchdev v1 at: https://lore.kernel.org/netdev/20230410204951.1359485-1-vladimir.oltean at nxp.com/ net/bridge/br_switchdev.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/net/bridge/br_switchdev.c b/net/bridge/br_switchdev.c index de18e9c1d7a7..ba95c4d74a60 100644 --- a/net/bridge/br_switchdev.c +++ b/net/bridge/br_switchdev.c @@ -148,6 +148,17 @@ br_switchdev_fdb_notify(struct net_bridge *br, if (test_bit(BR_FDB_LOCKED, &fdb->flags)) return; + /* Entries with these flags were created using ndm_state == NUD_REACHABLE, + * ndm_flags == NTF_MASTER( | NTF_STICKY), ext_flags == 0 by something + * equivalent to 'bridge fdb add ... master dynamic (sticky)'. + * Drivers don't know how to deal with these, so don't notify them to + * avoid confusing them. + */ + if (test_bit(BR_FDB_ADDED_BY_USER, &fdb->flags) && + !test_bit(BR_FDB_STATIC, &fdb->flags) && + !test_bit(BR_FDB_ADDED_BY_EXT_LEARN, &fdb->flags)) + return; + br_switchdev_fdb_populate(br, &item, fdb, NULL); switch (type) { -- 2.34.1
Ido Schimmel
2023-Apr-19 12:49 UTC
[Bridge] [PATCH v2 net] net: bridge: switchdev: don't notify FDB entries with "master dynamic"
On Tue, Apr 18, 2023 at 06:59:02PM +0300, Vladimir Oltean wrote:> diff --git a/net/bridge/br_switchdev.c b/net/bridge/br_switchdev.c > index de18e9c1d7a7..ba95c4d74a60 100644 > --- a/net/bridge/br_switchdev.c > +++ b/net/bridge/br_switchdev.c > @@ -148,6 +148,17 @@ br_switchdev_fdb_notify(struct net_bridge *br, > if (test_bit(BR_FDB_LOCKED, &fdb->flags)) > return;Thanks for the patch. Ran a few tests and looks fine. Will report full results tomorrow morning.> > + /* Entries with these flags were created using ndm_state == NUD_REACHABLE, > + * ndm_flags == NTF_MASTER( | NTF_STICKY), ext_flags == 0 by something > + * equivalent to 'bridge fdb add ... master dynamic (sticky)'. > + * Drivers don't know how to deal with these, so don't notify them to > + * avoid confusing them. > + */ > + if (test_bit(BR_FDB_ADDED_BY_USER, &fdb->flags) && > + !test_bit(BR_FDB_STATIC, &fdb->flags) && > + !test_bit(BR_FDB_ADDED_BY_EXT_LEARN, &fdb->flags)) > + return; > + > br_switchdev_fdb_populate(br, &item, fdb, NULL); > > switch (type) { > -- > 2.34.1 >
Ido Schimmel
2023-Apr-20 06:23 UTC
[Bridge] [PATCH v2 net] net: bridge: switchdev: don't notify FDB entries with "master dynamic"
On Tue, Apr 18, 2023 at 06:59:02PM +0300, Vladimir Oltean wrote:> There is a structural problem in switchdev, where the flag bits in > struct switchdev_notifier_fdb_info (added_by_user, is_local etc) only > represent a simplified / denatured view of what's in struct > net_bridge_fdb_entry :: flags (BR_FDB_ADDED_BY_USER, BR_FDB_LOCAL etc). > Each time we want to pass more information about struct > net_bridge_fdb_entry :: flags to struct switchdev_notifier_fdb_info > (here, BR_FDB_STATIC), we find that FDB entries were already notified to > switchdev with no regard to this flag, and thus, switchdev drivers had > no indication whether the notified entries were static or not.[...]> Fixes: 6b26b51b1d13 ("net: bridge: Add support for notifying devices about FDB add/del") > Link: https://lore.kernel.org/netdev/20230327115206.jk5q5l753aoelwus at skbuf/ > Signed-off-by: Vladimir Oltean <vladimir.oltean at nxp.com> > Reviewed-by: Jesse Brandeburg <jesse.brandeburg at intel.com>Reviewed-by: Ido Schimmel <idosch at nvidia.com> Tested-by: Ido Schimmel <idosch at nvidia.com>
patchwork-bot+netdevbpf at kernel.org
2023-Apr-20 07:50 UTC
[Bridge] [PATCH v2 net] net: bridge: switchdev: don't notify FDB entries with "master dynamic"
Hello: This patch was applied to netdev/net.git (main) by Paolo Abeni <pabeni at redhat.com>: On Tue, 18 Apr 2023 18:59:02 +0300 you wrote:> There is a structural problem in switchdev, where the flag bits in > struct switchdev_notifier_fdb_info (added_by_user, is_local etc) only > represent a simplified / denatured view of what's in struct > net_bridge_fdb_entry :: flags (BR_FDB_ADDED_BY_USER, BR_FDB_LOCAL etc). > Each time we want to pass more information about struct > net_bridge_fdb_entry :: flags to struct switchdev_notifier_fdb_info > (here, BR_FDB_STATIC), we find that FDB entries were already notified to > switchdev with no regard to this flag, and thus, switchdev drivers had > no indication whether the notified entries were static or not. > > [...]Here is the summary with links: - [v2,net] net: bridge: switchdev: don't notify FDB entries with "master dynamic" https://git.kernel.org/netdev/net/c/927cdea5d209 You are awesome, thank you! -- Deet-doot-dot, I am a bot. https://korg.docs.kernel.org/patchwork/pwbot.html
Hans Schultz
2023-Apr-23 08:47 UTC
[Bridge] [PATCH v2 net] net: bridge: switchdev: don't notify FDB entries with "master dynamic"
On Tue, Apr 18, 2023 at 18:59, Vladimir Oltean <vladimir.oltean at nxp.com> wrote:> diff --git a/net/bridge/br_switchdev.c b/net/bridge/br_switchdev.c > index de18e9c1d7a7..ba95c4d74a60 100644 > --- a/net/bridge/br_switchdev.c > +++ b/net/bridge/br_switchdev.c > @@ -148,6 +148,17 @@ br_switchdev_fdb_notify(struct net_bridge *br, > if (test_bit(BR_FDB_LOCKED, &fdb->flags)) > return; > > + /* Entries with these flags were created using ndm_state == NUD_REACHABLE, > + * ndm_flags == NTF_MASTER( | NTF_STICKY), ext_flags == 0 by something > + * equivalent to 'bridge fdb add ... master dynamic (sticky)'. > + * Drivers don't know how to deal with these, so don't notify them to > + * avoid confusing them. > + */ > + if (test_bit(BR_FDB_ADDED_BY_USER, &fdb->flags) && > + !test_bit(BR_FDB_STATIC, &fdb->flags) && > + !test_bit(BR_FDB_ADDED_BY_EXT_LEARN, &fdb->flags)) > + return; > +I do not understand this patch. It seems to me that it basically blocks any future use of dynamic fdb entries from userspace towards drivers. I would have expected that something would be done in the DSA layer, where (switchcore) drivers would be able to set some flags to indicate which features are supported by the driver, including non-static fdb entries. But as the placement here is earlier in the datapath from userspace towards drivers it's not possible to do any such thing in the DSA layer wrt non-static fdb entries.