user/sven/linux.git/include/net/switchdev.h, branch v5.15.53

net: make switchdev_bridge_port_{,unoffload} loosely coupled with the bridge

2021-08-04T11:35:07Z

With the introduction of explicit offloading API in switchdev in commit 2f5dc00f7a3e ("net: bridge: switchdev: let drivers inform which bridge ports are offloaded"), we started having Ethernet switch drivers calling directly into a function exported by net/bridge/br_switchdev.c, which is a function exported by the bridge driver. This means that drivers that did not have an explicit dependency on the bridge before, like cpsw and am65-cpsw, now do - otherwise it is not possible to call a symbol exported by a driver that can be built as module unless you are a module too. There was an attempt to solve the dependency issue in the form of commit b0e81817629a ("net: build all switchdev drivers as modules when the bridge is a module"). Grygorii Strashko, however, says about it: | In my opinion, the problem is a bit bigger here than just fixing the | build :( | | In case, of ^cpsw the switchdev mode is kinda optional and in many | cases (especially for testing purposes, NFS) the multi-mac mode is | still preferable mode. | | There were no such tight dependency between switchdev drivers and | bridge core before and switchdev serviced as independent, notification | based layer between them, so ^cpsw still can be "Y" and bridge can be | "M". Now for mostly every kernel build configuration the CONFIG_BRIDGE | will need to be set as "Y", or we will have to update drivers to | support build with BRIDGE=n and maintain separate builds for | networking vs non-networking testing. But is this enough? Wouldn't | it cause 'chain reaction' required to add more and more "Y" options | (like CONFIG_VLAN_8021Q)? | | PS. Just to be sure we on the same page - ARM builds will be forced | (with this patch) to have CONFIG_TI_CPSW_SWITCHDEV=m and so all our | automation testing will just fail with omap2plus_defconfig. In the light of this, it would be desirable for some configurations to avoid dependencies between switchdev drivers and the bridge, and have the switchdev mode as completely optional within the driver. Arnd Bergmann also tried to write a patch which better expressed the build time dependency for Ethernet switch drivers where the switchdev support is optional, like cpsw/am65-cpsw, and this made the drivers follow the bridge (compile as module if the bridge is a module) only if the optional switchdev support in the driver was enabled in the first place: https://patchwork.kernel.org/project/netdevbpf/patch/20210802144813.1152762-1-arnd@kernel.org/ but this still did not solve the fact that cpsw and am65-cpsw now must be built as modules when the bridge is a module - it just expressed correctly that optional dependency. But the new behavior is an apparent regression from Grygorii's perspective. So to support the use case where the Ethernet driver is built-in, NET_SWITCHDEV (a bool option) is enabled, and the bridge is a module, we need a framework that can handle the possible absence of the bridge from the running system, i.e. runtime bloatware as opposed to build-time bloatware. Luckily we already have this framework, since switchdev has been using it extensively. Events from the bridge side are transmitted to the driver side using notifier chains - this was originally done so that unrelated drivers could snoop for events emitted by the bridge towards ports that are implemented by other drivers (think of a switch driver with LAG offload that listens for switchdev events on a bonding/team interface that it offloads). There are also events which are transmitted from the driver side to the bridge side, which again are modeled using notifiers. SWITCHDEV_FDB_ADD_TO_BRIDGE is an example of this, and deals with notifying the bridge that a MAC address has been dynamically learned. So there is a precedent we can use for modeling the new framework. The difference compared to SWITCHDEV_FDB_ADD_TO_BRIDGE is that the work that the bridge needs to do when a port becomes offloaded is blocking in its nature: replay VLANs, MDBs etc. The calling context is indeed blocking (we are under rtnl_mutex), but the existing switchdev notification chain that the bridge is subscribed to is only the atomic one. So we need to subscribe the bridge to the blocking switchdev notification chain too. This patch: - keeps the driver-side perception of the switchdev_bridge_port_{,un}offload unchanged - moves the implementation of switchdev_bridge_port_{,un}offload from the bridge module into the switchdev module. - makes everybody that is subscribed to the switchdev blocking notifier chain "hear" offload & unoffload events - makes the bridge driver subscribe and handle those events - moves the bridge driver's handling of those events into 2 new functions called br_switchdev_port_{,un}offload. These functions contain in fact the core of the logic that was previously in switchdev_bridge_port_{,un}offload, just that now we go through an extra indirection layer to reach them. Unlike all the other switchdev notification structures, the structure used to carry the bridge port information, struct switchdev_notifier_brport_info, does not contain a "bool handled". This is because in the current usage pattern, we always know that a switchdev bridge port offloading event will be handled by the bridge, because the switchdev_bridge_port_offload() call was initiated by a NETDEV_CHANGEUPPER event in the first place, where info->upper_dev is a bridge. So if the bridge wasn't loaded, then the CHANGEUPPER event couldn't have happened. Signed-off-by: Vladimir Oltean Tested-by: Grygorii Strashko Signed-off-by: David S. Miller

net: switchdev: remove stray semicolon in switchdev_handle_fdb_del_to_device shim

2021-07-21T15:00:16Z

With the semicolon at the end, the compiler sees the shim function as a declaration and not as a definition, and warns: 'switchdev_handle_fdb_del_to_device' declared 'static' but never defined Reported-by: kernel test robot Fixes: 8ca07176ab00 ("net: switchdev: introduce a fanout helper for SWITCHDEV_FDB_{ADD,DEL}_TO_DEVICE") Signed-off-by: Vladimir Oltean Tested-by: Matthieu Baerts Signed-off-by: David S. Miller

net: switchdev: introduce a fanout helper for SWITCHDEV_FDB_{ADD,DEL}_TO_DEVICE

2021-07-20T14:04:27Z

Currently DSA has an issue with FDB entries pointing towards the bridge in the presence of br_fdb_replay() being called at port join and leave time. In particular, each bridge port will ask for a replay for the FDB entries pointing towards the bridge when it joins, and for another replay when it leaves. This means that for example, a bridge with 4 switch ports will notify DSA 4 times of the bridge MAC address. But if the MAC address of the bridge changes during the normal runtime of the system, the bridge notifies switchdev [ once ] of the deletion of the old MAC address as a local FDB towards the bridge, and of the insertion [ again once ] of the new MAC address as a local FDB. This is a problem, because DSA keeps the old MAC address as a host FDB entry with refcount 4 (4 ports asked for it using br_fdb_replay). So the old MAC address will not be deleted. Additionally, the new MAC address will only be installed with refcount 1, and when the first switch port leaves the bridge (leaving 3 others as still members), it will delete with it the new MAC address of the bridge from the local FDB entries kept by DSA (because the br_fdb_replay call on deletion will bring the entry's refcount from 1 to 0). So the problem, really, is that the number of br_fdb_replay() calls is not matched with the refcount that a host FDB is offloaded to DSA during normal runtime. An elegant way to solve the problem would be to make the switchdev notification emitted by br_fdb_change_mac_address() result in a host FDB kept by DSA which has a refcount exactly equal to the number of ports under that bridge. Then, no matter how many DSA ports join or leave that bridge, the host FDB entry will always be deleted when there are exactly zero remaining DSA switch ports members of the bridge. To implement the proposed solution, we remember that the switchdev objects and port attributes have some helpers provided by switchdev, which can be optionally called by drivers: switchdev_handle_port_obj_{add,del} and switchdev_handle_port_attr_set. These helpers: - fan out a switchdev object/attribute emitted for the bridge towards all the lower interfaces that pass the check_cb(). - fan out a switchdev object/attribute emitted for a bridge port that is a LAG towards all the lower interfaces that pass the check_cb(). In other words, this is the model we need for the FDB events too: something that will keep an FDB entry emitted towards a physical port as it is, but translate an FDB entry emitted towards the bridge into N FDB entries, one per physical port. Of course, there are many differences between fanning out a switchdev object (VLAN) on 3 lower interfaces of a LAG and fanning out an FDB entry on 3 lower interfaces of a LAG. Intuitively, an FDB entry towards a LAG should be treated specially, because FDB entries are unicast, we can't just install the same address towards 3 destinations. It is imaginable that drivers might want to treat this case specifically, so create some methods for this case and do not recurse into the LAG lower ports, just the bridge ports. DSA also listens for FDB entries on "foreign" interfaces, aka interfaces bridged with us which are not part of our hardware domain: think an Ethernet switch bridged with a Wi-Fi AP. For those addresses, DSA installs host FDB entries. However, there we have the same problem (those host FDB entries are installed with a refcount of only 1) and an even bigger one which we did not have with FDB entries towards the bridge: br_fdb_replay() is currently not called for FDB entries on foreign interfaces, just for the physical port and for the bridge itself. So when DSA sniffs an address learned by the software bridge towards a foreign interface like an e1000 port, and then that e1000 leaves the bridge, DSA remains with the dangling host FDB address. That will be fixed separately by replaying all FDB entries and not just the ones towards the port and the bridge. Signed-off-by: Vladimir Oltean Signed-off-by: David S. Miller

net: switchdev: introduce helper for checking dynamically learned FDB entries

2021-07-20T14:04:27Z

It is a bit difficult to understand what DSA checks when it tries to avoid installing dynamically learned addresses on foreign interfaces as local host addresses, so create a generic switchdev helper that can be reused and is generally more readable. Signed-off-by: Vladimir Oltean Signed-off-by: David S. Miller

net: switchdev: add a context void pointer to struct switchdev_notifier_info

2021-06-28T21:09:03Z

In the case where the driver asks for a replay of a certain type of event (port object or attribute) for a bridge port that is a LAG, it may do so because this port has just joined the LAG. But there might already be other switchdev ports in that LAG, and it is preferable that those preexisting switchdev ports do not act upon the replayed event. The solution is to add a context to switchdev events, which is NULL most of the time (when the bridge layer initiates the call) but which can be set to a value controlled by the switchdev driver when a replay is requested. The driver can then check the context to figure out if all ports within the LAG should act upon the switchdev event, or just the ones that match the context. We have to modify all switchdev_handle_* helper functions as well as the prototypes in the drivers that use these helpers too, because these helpers hide the underlying struct switchdev_notifier_info from us and there is no way to retrieve the context otherwise. The context structure will be populated and used in later patches. Signed-off-by: Vladimir Oltean Reviewed-by: Florian Fainelli Signed-off-by: David S. Miller

net: bridge: switchdev: include local flag in FDB notifications

2021-04-16T22:15:45Z

As explained in bugfix commit 6ab4c3117aec ("net: bridge: don't notify switchdev for local FDB addresses") as well as in this discussion: https://lore.kernel.org/netdev/20210117193009.io3nungdwuzmo5f7@skbuf/ the switchdev notifiers for FDB entries managed to have a zero-day bug, which was that drivers would not know what to do with local FDB entries, because they were not told that they are local. The bug fix was to simply not notify them of those addresses. Let us now add the 'is_local' bit to bridge FDB entries, and make all drivers ignore these entries by their own choice. Co-developed-by: Tobias Waldekranz Signed-off-by: Tobias Waldekranz Signed-off-by: Vladimir Oltean Reviewed-by: Grygorii Strashko Reviewed-by: Ido Schimmel Signed-off-by: David S. Miller

net: bridge: add helper to replay port and host-joined mdb entries

2021-03-23T21:49:05Z

I have a system with DSA ports, and udhcpcd is configured to bring interfaces up as soon as they are created. I create a bridge as follows: ip link add br0 type bridge As soon as I create the bridge and udhcpcd brings it up, I also have avahi which automatically starts sending IPv6 packets to advertise some local services, and because of that, the br0 bridge joins the following IPv6 groups due to the code path detailed below: 33:33:ff:6d:c1:9c vid 0 33:33:00:00:00:6a vid 0 33:33:00:00:00:fb vid 0 br_dev_xmit -> br_multicast_rcv -> br_ip6_multicast_add_group -> __br_multicast_add_group -> br_multicast_host_join -> br_mdb_notify This is all fine, but inside br_mdb_notify we have br_mdb_switchdev_host hooked up, and switchdev will attempt to offload the host joined groups to an empty list of ports. Of course nobody offloads them. Then when we add a port to br0: ip link set swp0 master br0 the bridge doesn't replay the host-joined MDB entries from br_add_if, and eventually the host joined addresses expire, and a switchdev notification for deleting it is emitted, but surprise, the original addition was already completely missed. The strategy to address this problem is to replay the MDB entries (both the port ones and the host joined ones) when the new port joins the bridge, similar to what vxlan_fdb_replay does (in that case, its FDB can be populated and only then attached to a bridge that you offload). However there are 2 possibilities: the addresses can be 'pushed' by the bridge into the port, or the port can 'pull' them from the bridge. Considering that in the general case, the new port can be really late to the party, and there may have been many other switchdev ports that already received the initial notification, we would like to avoid delivering duplicate events to them, since they might misbehave. And currently, the bridge calls the entire switchdev notifier chain, whereas for replaying it should just call the notifier block of the new guy. But the bridge doesn't know what is the new guy's notifier block, it just knows where the switchdev notifier chain is. So for simplification, we make this a driver-initiated pull for now, and the notifier block is passed as an argument. To emulate the calling context for mdb objects (deferred and put on the blocking notifier chain), we must iterate under RCU protection through the bridge's mdb entries, queue them, and only call them once we're out of the RCU read-side critical section. There was some opportunity for reuse between br_mdb_switchdev_host_port, br_mdb_notify and the newly added br_mdb_queue_one in how the switchdev mdb object is created, so a helper was created. Suggested-by: Ido Schimmel Signed-off-by: Vladimir Oltean Acked-by: Nikolay Aleksandrov Signed-off-by: David S. Miller

switchdev: mrp: Extend ring_role_mrp and in_role_mrp

2021-02-16T22:47:46Z

Add the member sw_backup to the structures switchdev_obj_ring_role_mrp and switchdev_obj_in_role_mrp. In this way the SW can call the driver in 2 ways, once when sw_backup is set to false, meaning that the driver should implement this completely in HW. And if that is not supported the SW will call again but with sw_backup set to true, meaning that the HW should help or allow the SW to run the protocol. For example when role is MRM, if the HW can't detect when it stops receiving MRP Test frames but it can trap these frames to CPU, then it needs to return -EOPNOTSUPP when sw_backup is false and return 0 when sw_backup is true. Signed-off-by: Horatiu Vultur Signed-off-by: David S. Miller

switchdev: mrp: Remove CONFIG_BRIDGE_MRP

2021-02-16T22:47:46Z

Remove #IS_ENABLED(CONFIG_BRIDGE_MRP) from switchdev.h. This will simplify the code implements MRP callbacks and will be similar with the vlan filtering. Signed-off-by: Horatiu Vultur Signed-off-by: David S. Miller

net: bridge: fix switchdev_port_attr_set stub when CONFIG_SWITCHDEV=n

2021-02-15T21:15:10Z

The switchdev_port_attr_set function prototype was updated only for the case where CONFIG_SWITCHDEV=y|m, leaving a prototype mismatch with the stub definition for the disabled case. This results in a build error, so update that function too. Fixes: dcbdf1350e33 ("net: bridge: propagate extack through switchdev_port_attr_set") Signed-off-by: Vladimir Oltean Signed-off-by: David S. Miller