| Message ID | 20230418155902.898627-1-vladimir.oltean@nxp.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 927cdea5d2095287ddd5246e5aa68eb5d68db2be |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v2,net] net: bridge: switchdev: don't notify FDB entries with "master dynamic" | expand |
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 >
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@skbuf/ > Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> > Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com> Reviewed-by: Ido Schimmel <idosch@nvidia.com> Tested-by: Ido Schimmel <idosch@nvidia.com>
Hello: This patch was applied to netdev/net.git (main) by Paolo Abeni <pabeni@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!
On Tue, Apr 18, 2023 at 18:59, Vladimir Oltean <vladimir.oltean@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.
On Sun, Apr 23, 2023 at 10:47:15AM +0200, Hans Schultz wrote: > 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. As explained too many times already in the thread here: https://patchwork.kernel.org/project/netdevbpf/patch/20230318141010.513424-3-netdev@kapio-technology.com/ the plan is: | Just like commit 6ab4c3117aec ("net: bridge: don't notify switchdev for | local FDB addresses"), we could deny that for stable kernels, and add | the correct interpretation of the flag in net-next. Obviously we have not reached the end of that plan, and net-next is closed now.
On Mon, Apr 24, 2023 at 15:26, Vladimir Oltean <vladimir.oltean@nxp.com> wrote: > On Sun, Apr 23, 2023 at 10:47:15AM +0200, Hans Schultz wrote: >> 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. > > As explained too many times already in the thread here: > https://patchwork.kernel.org/project/netdevbpf/patch/20230318141010.513424-3-netdev@kapio-technology.com/ > the plan is: Ahh yes thanks, I see the comment you wrote on march the 27th.
On Mon, Apr 24, 2023 at 15:26, Vladimir Oltean <vladimir.oltean@nxp.com> wrote: > > Obviously we have not reached the end of that plan, and net-next is closed now. Seems to me that net-next is open. Maybe it will close soon.
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) {
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@skbuf/ Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> Reviewed-by: Jesse Brandeburg <jesse.brandeburg@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@nxp.com/ net/bridge/br_switchdev.c | 11 +++++++++++ 1 file changed, 11 insertions(+)