kernel/linux.git/net/dsa/switch.c, branch v6.6.132

net: dsa: avoid suspicious RCU usage for synced VLAN-aware MAC addresses

2023-06-27T16:37:41+00:00

When using the felix driver (the only one which supports UC filtering and MC filtering) as a DSA master for a random other DSA switch, one can see the following stack trace when the downstream switch ports join a VLAN-aware bridge: ============================= WARNING: suspicious RCU usage ----------------------------- net/8021q/vlan_core.c:238 suspicious rcu_dereference_protected() usage! stack backtrace: Workqueue: dsa_ordered dsa_slave_switchdev_event_work Call trace: lockdep_rcu_suspicious+0x170/0x210 vlan_for_each+0x8c/0x188 dsa_slave_sync_uc+0x128/0x178 __hw_addr_sync_dev+0x138/0x158 dsa_slave_set_rx_mode+0x58/0x70 __dev_set_rx_mode+0x88/0xa8 dev_uc_add+0x74/0xa0 dsa_port_bridge_host_fdb_add+0xec/0x180 dsa_slave_switchdev_event_work+0x7c/0x1c8 process_one_work+0x290/0x568 What it's saying is that vlan_for_each() expects rtnl_lock() context and it's not getting it, when it's called from the DSA master's ndo_set_rx_mode(). The caller of that - dsa_slave_set_rx_mode() - is the slave DSA interface's dsa_port_bridge_host_fdb_add() which comes from the deferred dsa_slave_switchdev_event_work(). We went to great lengths to avoid the rtnl_lock() context in that call path in commit 0faf890fc519 ("net: dsa: drop rtnl_lock from dsa_slave_switchdev_event_work"), and calling rtnl_lock() is simply not an option due to the possibility of deadlocking when calling dsa_flush_workqueue() from the call paths that do hold rtnl_lock() - basically all of them. So, when the DSA master calls vlan_for_each() from its ndo_set_rx_mode(), the state of the 8021q driver on this device is really not protected from concurrent access by anything. Looking at net/8021q/, I don't think that vlan_info->vid_list was particularly designed with RCU traversal in mind, so introducing an RCU read-side form of vlan_for_each() - vlan_for_each_rcu() - won't be so easy, and it also wouldn't be exactly what we need anyway. In general I believe that the solution isn't in net/8021q/ anyway; vlan_for_each() is not cut out for this task. DSA doesn't need rtnl_lock() to be held per se - since it's not a netdev state change that we're blocking, but rather, just concurrent additions/removals to a VLAN list. We don't even need sleepable context - the callback of vlan_for_each() just schedules deferred work. The proposed escape is to remove the dependency on vlan_for_each() and to open-code a non-sleepable, rtnl-free alternative to that, based on copies of the VLAN list modified from .ndo_vlan_rx_add_vid() and .ndo_vlan_rx_kill_vid(). Fixes: 64fdc5f341db ("net: dsa: sync unicast and multicast addresses for VLAN filters too") Signed-off-by: Vladimir Oltean Link: https://lore.kernel.org/r/20230626154402.3154454-1-vladimir.oltean@nxp.com Signed-off-by: Jakub Kicinski

net: dsa: add trace points for VLAN operations

2023-04-12T07:36:07+00:00

These are not as critical as the FDB/MDB trace points (I'm not aware of outstanding VLAN related bugs), but maybe they are useful to somebody, either debugging something or simply trying to learn more. Signed-off-by: Vladimir Oltean Signed-off-by: David S. Miller

net: dsa: add trace points for FDB/MDB operations

2023-04-12T07:36:07+00:00

DSA performs non-trivial housekeeping of unicast and multicast addresses on shared (CPU and DSA) ports, and puts a bit of pressure on higher layers, requiring them to behave correctly (remove these addresses exactly as many times as they were added). Otherwise, either addresses linger around forever, or DSA returns -ENOENT complaining that entries that were already deleted must be deleted again. To aid debugging, introduce some trace points specifically for FDB and MDB - that's where some of the bugs still are right now. Some bugs I have seen were also due to race conditions, see: - 630fd4822af2 ("net: dsa: flush switchdev workqueue on bridge join error path") - a2614140dc0f ("net: dsa: mv88e6xxx: flush switchdev FDB workqueue before removing VLAN") so it would be good to not disturb the timing too much, hence the choice to use trace points vs regular dev_dbg(). I've had these for some time on my computer in a less polished form, and they've proven useful. What I found most useful was to enable CONFIG_BOOTTIME_TRACING, add "trace_event=dsa" to the kernel cmdline, and run "cat /sys/kernel/debug/tracing/trace". This is to debug more complex environments with network managers started by the init system, things like that. Signed-off-by: Vladimir Oltean Signed-off-by: David S. Miller

net: dsa: kill off dsa_priv.h

2022-11-23T04:41:54+00:00

The last remnants in dsa_priv.h are a netlink-related definition for which we create a new header, and DSA_MAX_NUM_OFFLOADING_BRIDGES which is only used from dsa.c, so move it there. Some inclusions need to be adjusted now that we no longer have headers included transitively from dsa_priv.h. Signed-off-by: Vladimir Oltean Reviewed-by: Florian Fainelli Signed-off-by: Jakub Kicinski

net: dsa: move tag_8021q headers to their proper place

2022-11-23T04:41:53+00:00

tag_8021q definitions are all over the place. Some are exported to linux/dsa/8021q.h (visible by DSA core, taggers, switch drivers and everyone else), and some are in dsa_priv.h. Move the structures that don't need external visibility into tag_8021q.c, and the ones which don't need the world or switch drivers to see them into tag_8021q.h. We also have the tag_8021q.h inclusion from switch.c, which is basically the entire reason why tag_8021q.c was built into DSA in commit 8b6e638b4be2 ("net: dsa: build tag_8021q.c as part of DSA core"). I still don't know how to better deal with that, so leave it alone. Signed-off-by: Vladimir Oltean Reviewed-by: Florian Fainelli Signed-off-by: Jakub Kicinski

net: dsa: rename dsa2.c back into dsa.c and create its header

2022-11-23T04:41:53+00:00

The previous change moved the code into the larger file (dsa2.c) to minimize the delta. Rename that now to dsa.c, and create dsa.h, where all related definitions from dsa_priv.h go. Signed-off-by: Vladimir Oltean Reviewed-by: Florian Fainelli Signed-off-by: Jakub Kicinski

net: dsa: move dsa_tree_notify() and dsa_broadcast() to switch.c

2022-11-23T04:41:51+00:00

There isn't an intuitive place for these 2 cross-chip notifier functions according to the function-to-file classification based on names (dsa_switch_*() goes to switch.c), but I consider these to be part of the cross-chip notifier handling, therefore part of switch.c. Move them there to reduce bloat in dsa2.c (the place where all code with no better place to go goes). Signed-off-by: Vladimir Oltean Reviewed-by: Florian Fainelli Signed-off-by: Jakub Kicinski

net: dsa: move headers exported by switch.c to switch.h

2022-11-23T04:41:51+00:00

Reduce code bloat in dsa_priv.h by moving the prototypes exported by switch.h into their own header file. Signed-off-by: Vladimir Oltean Reviewed-by: Florian Fainelli Signed-off-by: Jakub Kicinski

net: dsa: move headers exported by slave.c to slave.h

2022-11-23T04:41:49+00:00

Minimize the use of the bloated dsa_priv.h by moving the prototypes exported by slave.c to their own header file. This is just approximate to get the code structure right. There are some interdependencies with static inline code left in dsa_priv.h, so leave slave.h included from there for now. Signed-off-by: Vladimir Oltean Reviewed-by: Florian Fainelli Signed-off-by: Jakub Kicinski

net: dsa: move headers exported by port.c to port.h

2022-11-23T04:41:48+00:00

Minimize the use of the bloated dsa_priv.h by moving the prototypes exported by port.c to their own header file. Signed-off-by: Vladimir Oltean Reviewed-by: Florian Fainelli Signed-off-by: Jakub Kicinski