kernel/linux.git/include/net/dsa.h, branch v6.18.21

net: dsa: properly keep track of conduit reference

2026-01-08T09:16:45+00:00

[ Upstream commit 06e219f6a706c367c93051f408ac61417643d2f9 ] Problem description ------------------- DSA has a mumbo-jumbo of reference handling of the conduit net device and its kobject which, sadly, is just wrong and doesn't make sense. There are two distinct problems. 1. The OF path, which uses of_find_net_device_by_node(), never releases the elevated refcount on the conduit's kobject. Nominally, the OF and non-OF paths should result in objects having identical reference counts taken, and it is already suspicious that dsa_dev_to_net_device() has a put_device() call which is missing in dsa_port_parse_of(), but we can actually even verify that an issue exists. With CONFIG_DEBUG_KOBJECT_RELEASE=y, if we run this command "before" and "after" applying this patch: (unbind the conduit driver for net device eno2) echo 0000:00:00.2 > /sys/bus/pci/drivers/fsl_enetc/unbind we see these lines in the output diff which appear only with the patch applied: kobject: 'eno2' (ffff002009a3a6b8): kobject_release, parent 0000000000000000 (delayed 1000) kobject: '109' (ffff0020099d59a0): kobject_release, parent 0000000000000000 (delayed 1000) 2. After we find the conduit interface one way (OF) or another (non-OF), it can get unregistered at any time, and DSA remains with a long-lived, but in this case stale, cpu_dp->conduit pointer. Holding the net device's underlying kobject isn't actually of much help, it just prevents it from being freed (but we never need that kobject directly). What helps us to prevent the net device from being unregistered is the parallel netdev reference mechanism (dev_hold() and dev_put()). Actually we actually use that netdev tracker mechanism implicitly on user ports since commit 2f1e8ea726e9 ("net: dsa: link interfaces with the DSA master to get rid of lockdep warnings"), via netdev_upper_dev_link(). But time still passes at DSA switch probe time between the initial of_find_net_device_by_node() code and the user port creation time, time during which the conduit could unregister itself and DSA wouldn't know about it. So we have to run of_find_net_device_by_node() under rtnl_lock() to prevent that from happening, and release the lock only with the netdev tracker having acquired the reference. Do we need to keep the reference until dsa_unregister_switch() / dsa_switch_shutdown()? 1: Maybe yes. A switch device will still be registered even if all user ports failed to probe, see commit 86f8b1c01a0a ("net: dsa: Do not make user port errors fatal"), and the cpu_dp->conduit pointers remain valid. I haven't audited all call paths to see whether they will actually use the conduit in lack of any user port, but if they do, it seems safer to not rely on user ports for that reference. 2. Definitely yes. We support changing the conduit which a user port is associated to, and we can get into a situation where we've moved all user ports away from a conduit, thus no longer hold any reference to it via the net device tracker. But we shouldn't let it go nonetheless - see the next change in relation to dsa_tree_find_first_conduit() and LAG conduits which disappear. We have to be prepared to return to the physical conduit, so the CPU port must explicitly keep another reference to it. This is also to say: the user ports and their CPU ports may not always keep a reference to the same conduit net device, and both are needed. As for the conduit's kobject for the /sys/class/net/ entry, we don't care about it, we can release it as soon as we hold the net device object itself. History and blame attribution ----------------------------- The code has been refactored so many times, it is very difficult to follow and properly attribute a blame, but I'll try to make a short history which I hope to be correct. We have two distinct probing paths: - one for OF, introduced in 2016 in commit 83c0afaec7b7 ("net: dsa: Add new binding implementation") - one for non-OF, introduced in 2017 in commit 71e0bbde0d88 ("net: dsa: Add support for platform data") These are both complete rewrites of the original probing paths (which used struct dsa_switch_driver and other weird stuff, instead of regular devices on their respective buses for register access, like MDIO, SPI, I2C etc): - one for OF, introduced in 2013 in commit 5e95329b701c ("dsa: add device tree bindings to register DSA switches") - one for non-OF, introduced in 2008 in commit 91da11f870f0 ("net: Distributed Switch Architecture protocol support") except for tiny bits and pieces like dsa_dev_to_net_device() which were seemingly carried over since the original commit, and used to this day. The point is that the original probing paths received a fix in 2015 in the form of commit 679fb46c5785 ("net: dsa: Add missing master netdev dev_put() calls"), but the fix never made it into the "new" (dsa2) probing paths that can still be traced to today, and the fixed probing path was later deleted in 2019 in commit 93e86b3bc842 ("net: dsa: Remove legacy probing support"). That is to say, the new probing paths were never quite correct in this area. The existence of the legacy probing support which was deleted in 2019 explains why dsa_dev_to_net_device() returns a conduit with elevated refcount (because it was supposed to be released during dsa_remove_dst()). After the removal of the legacy code, the only user of dsa_dev_to_net_device() calls dev_put(conduit) immediately after this function returns. This pattern makes no sense today, and can only be interpreted historically to understand why dev_hold() was there in the first place. Change details -------------- Today we have a better netdev tracking infrastructure which we should use. Logically netdev_hold() belongs in common code (dsa_port_parse_cpu(), where dp->conduit is assigned), but there is a tradeoff to be made with the rtnl_lock() section which would become a bit too long if we did that - dsa_port_parse_cpu() also calls request_module(). So we duplicate a bit of logic in order for the callers of dsa_port_parse_cpu() to be the ones responsible of holding the conduit reference and releasing it on error. This shortens the rtnl_lock() section significantly. In the dsa_switch_probe() error path, dsa_switch_release_ports() will be called in a number of situations, one being where dsa_port_parse_cpu() maybe didn't get the chance to run at all (a different port failed earlier, etc). So we have to test for the conduit being NULL prior to calling netdev_put(). There have still been so many transformations to the code since the blamed commits (rename master -> conduit, commit 0650bf52b31f ("net: dsa: be compatible with masters which unregister on shutdown")), that it only makes sense to fix the code using the best methods available today and see how it can be backported to stable later. I suspect the fix cannot even be backported to kernels which lack dsa_switch_shutdown(), and I suspect this is also maybe why the long-lived conduit reference didn't make it into the new DSA probing paths at the time (problems during shutdown). Because dsa_dev_to_net_device() has a single call site and has to be changed anyway, the logic was just absorbed into the non-OF dsa_port_parse(). Tested on the ocelot/felix switch and on dsa_loop, both on the NXP LS1028A with CONFIG_DEBUG_KOBJECT_RELEASE=y. Reported-by: Ma Ke Closes: https://lore.kernel.org/netdev/20251214131204.4684-1-make24@iscas.ac.cn/ Fixes: 83c0afaec7b7 ("net: dsa: Add new binding implementation") Fixes: 71e0bbde0d88 ("net: dsa: Add support for platform data") Reviewed-by: Jonas Gorski Signed-off-by: Vladimir Oltean Link: https://patch.msgid.link/20251215150236.3931670-1-vladimir.oltean@nxp.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin

net: dsa: tag_brcm: add support for legacy FCS tags

2025-06-18T00:52:01+00:00

Add support for legacy Broadcom FCS tags, which are similar to DSA_TAG_PROTO_BRCM_LEGACY. BCM5325 and BCM5365 switches require including the original FCS value and length, as opposed to BCM63xx switches. Adding the original FCS value and length to DSA_TAG_PROTO_BRCM_LEGACY would impact performance of BCM63xx switches, so it's better to create a new tag. Signed-off-by: Álvaro Fernández Rojas Reviewed-by: Florian Fainelli Link: https://patch.msgid.link/20250614080000.1884236-3-noltari@gmail.com Signed-off-by: Jakub Kicinski

net: dsa: convert to ndo_hwtstamp_get() and ndo_hwtstamp_set()

2025-05-09T23:34:09+00:00

New timestamping API was introduced in commit 66f7223039c0 ("net: add NDOs for configuring hardware timestamping") from kernel v6.6. It is time to convert DSA to the new API, so that the ndo_eth_ioctl() path can be removed completely. Move the ds->ops->port_hwtstamp_get() and ds->ops->port_hwtstamp_set() calls from dsa_user_ioctl() to dsa_user_hwtstamp_get() and dsa_user_hwtstamp_set(). Due to the fact that the underlying ifreq type changes to kernel_hwtstamp_config, the drivers and the Ocelot switchdev front-end, all hooked up directly or indirectly, must also be converted all at once. The conversion also updates the comment from dsa_port_supports_hwtstamp(), which is no longer true because kernel_hwtstamp_config is kernel memory and does not need copy_to_user(). I've deliberated whether it is necessary to also update "err != -EOPNOTSUPP" to a more general "!err", but all drivers now either return 0 or -EOPNOTSUPP. The existing logic from the ocelot_ioctl() function, to avoid configuring timestamping if the PHY supports the operation, is obsoleted by more advanced core logic in dev_set_hwtstamp_phylib(). This is only a partial preparation for proper PHY timestamping support. None of these switch driver currently sets up PTP traps for PHY timestamping, so setting dev->see_all_hwtstamp_requests is not yet necessary and the conversion is relatively trivial. Signed-off-by: Vladimir Oltean Tested-by: Vladimir Oltean # felix, sja1105, mv88e6xxx Reviewed-by: Vadim Fedorenko Link: https://patch.msgid.link/20250508095236.887789-1-vladimir.oltean@nxp.com Signed-off-by: Jakub Kicinski

net: dsa: implement get_ts_stats ethtool operation for user ports

2025-01-18T04:01:09+00:00

Integrate with the standard infrastructure for reporting hardware packet timestamping statistics. Signed-off-by: Vladimir Oltean Reviewed-by: Jakub Kicinski Link: https://patch.msgid.link/20250116104628.123555-3-vladimir.oltean@nxp.com Signed-off-by: Jakub Kicinski

net: dsa: remove get_mac_eee() method

2025-01-08T02:06:18+00:00

The get_mac_eee() is no longer called by the core DSA code, nor are there any implementations of this method. Remove it. Signed-off-by: Russell King (Oracle) Link: https://patch.msgid.link/E1tUllU-007UzL-KV@rmk-PC.armlinux.org.uk Signed-off-by: Jakub Kicinski

net: dsa: provide implementation of .support_eee()

2024-12-12T04:29:38+00:00

Provide a trivial implementation for the .support_eee() method which switch drivers can use to simply indicate that they support EEE on all their user ports. Signed-off-by: Russell King (Oracle) Reviewed-by: Florian Fainelli Reviewed-by: Vladimir Oltean Link: https://patch.msgid.link/E1tL149-006cZJ-JJ@rmk-PC.armlinux.org.uk Signed-off-by: Jakub Kicinski

net: dsa: add hook to determine whether EEE is supported

2024-12-12T04:29:38+00:00

Add a hook to determine whether the switch supports EEE. This will return false if the switch does not, or true if it does. If the method is not implemented, we assume (currently) that the switch supports EEE. Signed-off-by: Russell King (Oracle) Reviewed-by: Florian Fainelli Reviewed-by: Vladimir Oltean Link: https://patch.msgid.link/E1tL144-006cZD-El@rmk-PC.armlinux.org.uk Signed-off-by: Jakub Kicinski

net: dsa: remove obsolete phylink dsa_switch operations

2024-10-07T23:23:10+00:00

No driver now uses the DSA switch phylink members, so we can now remove the method pointers, but we need to leave empty shim functions to allow those drivers that do not provide phylink MAC operations structure to continue functioning. Signed-off-by: Russell King (oracle) Reviewed-by: Vladimir Oltean Tested-by: Vladimir Oltean # sja1105, felix, dsa_loop Link: https://patch.msgid.link/E1swKNV-0060oN-1b@rmk-PC.armlinux.org.uk Signed-off-by: Jakub Kicinski

net: dsa: provide a software untagging function on RX for VLAN-aware bridges

2024-08-16T08:59:32+00:00

Through code analysis, I realized that the ds->untag_bridge_pvid logic is contradictory - see the newly added FIXME above the kernel-doc for dsa_software_untag_vlan_unaware_bridge(). Moreover, for the Felix driver, I need something very similar, but which is actually _not_ contradictory: untag the bridge PVID on RX, but for VLAN-aware bridges. The existing logic does it for VLAN-unaware bridges. Since I don't want to change the functionality of drivers which were supposedly properly tested with the ds->untag_bridge_pvid flag, I have introduced a new one: ds->untag_vlan_aware_bridge_pvid, and I have refactored the DSA reception code into a common path for both flags. TODO: both flags should be unified under a single ds->software_vlan_untag, which users of both current flags should set. This is not something that can be carried out right away. It needs very careful examination of all drivers which make use of this functionality, since some of them actually get this wrong in the first place. For example, commit 9130c2d30c17 ("net: dsa: microchip: ksz8795: Use software untagging on CPU port") uses this in a driver which has ds->configure_vlan_while_not_filtering = true. The latter mechanism has been known for many years to be broken by design: https://lore.kernel.org/netdev/CABumfLzJmXDN_W-8Z=p9KyKUVi_HhS7o_poBkeKHS2BkAiyYpw@mail.gmail.com/ and we have the situation of 2 bugs canceling each other. There is no private VLAN, and the port follows the PVID of the VLAN-unaware bridge. So, it's kinda ok for that driver to use the ds->untag_bridge_pvid mechanism, in a broken way. Signed-off-by: Vladimir Oltean Signed-off-by: David S. Miller

Merge branch 'net-make-timestamping-selectable'

2024-07-15T15:02:30+00:00

First part of "net: Make timestamping selectable" from Kory Maincent. Change the driver-facing type already to lower rebasing pain. Link: https://lore.kernel.org/20240709-feature_ptp_netnext-v17-0-b5317f50df2a@bootlin.com/ Signed-off-by: Jakub Kicinski