From 88c0a6b503b7f4fffb68a8d49c3987870c5b1d6b Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Sun, 2 Apr 2023 15:37:55 +0300 Subject: net: create a netdev notifier for DSA to reject PTP on DSA master The fact that PTP 2-step TX timestamping is broken on DSA switches if the master also timestamps the same packets is documented by commit f685e609a301 ("net: dsa: Deny PTP on master if switch supports it"). We attempt to help the users avoid shooting themselves in the foot by making DSA reject the timestamping ioctls on an interface that is a DSA master, and the switch tree beneath it contains switches which are aware of PTP. The only problem is that there isn't an established way of intercepting ndo_eth_ioctl calls, so DSA creates avoidable burden upon the network stack by creating a struct dsa_netdevice_ops with overlaid function pointers that are manually checked from the relevant call sites. There used to be 2 such dsa_netdevice_ops, but now, ndo_eth_ioctl is the only one left. There is an ongoing effort to migrate driver-visible hardware timestamping control from the ndo_eth_ioctl() based API to a new ndo_hwtstamp_set() model, but DSA actively prevents that migration, since dsa_master_ioctl() is currently coded to manually call the master's legacy ndo_eth_ioctl(), and so, whenever a network device driver would be converted to the new API, DSA's restrictions would be circumvented, because any device could be used as a DSA master. The established way for unrelated modules to react on a net device event is via netdevice notifiers. So we create a new notifier which gets called whenever there is an attempt to change hardware timestamping settings on a device. Finally, there is another reason why a netdev notifier will be a good idea, besides strictly DSA, and this has to do with PHY timestamping. With ndo_eth_ioctl(), all MAC drivers must manually call phy_has_hwtstamp() before deciding whether to act upon SIOCSHWTSTAMP, otherwise they must pass this ioctl to the PHY driver via phy_mii_ioctl(). With the new ndo_hwtstamp_set() API, it will be desirable to simply not make any calls into the MAC device driver when timestamping should be performed at the PHY level. But there exist drivers, such as the lan966x switch, which need to install packet traps for PTP regardless of whether they are the layer that provides the hardware timestamps, or the PHY is. That would be impossible to support with the new API. The proposal there, too, is to introduce a netdev notifier which acts as a better cue for switching drivers to add or remove PTP packet traps, than ndo_hwtstamp_set(). The one introduced here "almost" works there as well, except for the fact that packet traps should only be installed if the PHY driver succeeded to enable hardware timestamping, whereas here, we need to deny hardware timestamping on the DSA master before it actually gets enabled. This is why this notifier is called "PRE_", and the notifier that would get used for PHY timestamping and packet traps would be called NETDEV_CHANGE_HWTSTAMP. This isn't a new concept, for example NETDEV_CHANGEUPPER and NETDEV_PRECHANGEUPPER do the same thing. In expectation of future netlink UAPI, we also pass a non-NULL extack pointer to the netdev notifier, and we make DSA populate it with an informative reason for the rejection. To avoid making it go to waste, we make the ioctl-based dev_set_hwtstamp() create a fake extack and print the message to the kernel log. Link: https://lore.kernel.org/netdev/20230401191215.tvveoi3lkawgg6g4@skbuf/ Link: https://lore.kernel.org/netdev/20230310164451.ls7bbs6pdzs4m6pw@skbuf/ Signed-off-by: Vladimir Oltean Reviewed-by: Florian Fainelli Signed-off-by: David S. Miller --- net/dsa/master.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'net/dsa/master.h') diff --git a/net/dsa/master.h b/net/dsa/master.h index 3fc0e610b5b5..80842f4e27f7 100644 --- a/net/dsa/master.h +++ b/net/dsa/master.h @@ -15,5 +15,8 @@ int dsa_master_lag_setup(struct net_device *lag_dev, struct dsa_port *cpu_dp, struct netlink_ext_ack *extack); void dsa_master_lag_teardown(struct net_device *lag_dev, struct dsa_port *cpu_dp); +int dsa_master_pre_change_hwtstamp(struct net_device *dev, + const struct kernel_hwtstamp_config *config, + struct netlink_ext_ack *extack); #endif -- cgit v1.2.3 From 5a17818682cf43ad0fdd6035945f3b7a8c9dc5e9 Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Thu, 6 Apr 2023 14:42:46 +0300 Subject: net: dsa: replace NETDEV_PRE_CHANGE_HWTSTAMP notifier with a stub There was a sort of rush surrounding commit 88c0a6b503b7 ("net: create a netdev notifier for DSA to reject PTP on DSA master"), due to a desire to convert DSA's attempt to deny TX timestamping on a DSA master to something that doesn't block the kernel-wide API conversion from ndo_eth_ioctl() to ndo_hwtstamp_set(). What was required was a mechanism that did not depend on ndo_eth_ioctl(), and what was provided was a mechanism that did not depend on ndo_eth_ioctl(), while at the same time introducing something that wasn't absolutely necessary - a new netdev notifier. There have been objections from Jakub Kicinski that using notifiers in general when they are not absolutely necessary creates complications to the control flow and difficulties to maintainers who look at the code. So there is a desire to not use notifiers. In addition to that, the notifier chain gets called even if there is no DSA in the system and no one is interested in applying any restriction. Take the model of udp_tunnel_nic_ops and introduce a stub mechanism, through which net/core/dev_ioctl.c can call into DSA even when CONFIG_NET_DSA=m. Compared to the code that existed prior to the notifier conversion, aka what was added in commits: - 4cfab3566710 ("net: dsa: Add wrappers for overloaded ndo_ops") - 3369afba1e46 ("net: Call into DSA netdevice_ops wrappers") this is different because we are not overloading any struct net_device_ops of the DSA master anymore, but rather, we are exposing a rather specific functionality which is orthogonal to which API is used to enable it - ndo_eth_ioctl() or ndo_hwtstamp_set(). Also, what is similar is that both approaches use function pointers to get from built-in code to DSA. There is no point in replicating the function pointers towards __dsa_master_hwtstamp_validate() once for every CPU port (dev->dsa_ptr). Instead, it is sufficient to introduce a singleton struct dsa_stubs, built into the kernel, which contains a single function pointer to __dsa_master_hwtstamp_validate(). I find this approach preferable to what we had originally, because dev->dsa_ptr->netdev_ops->ndo_do_ioctl() used to require going through struct dsa_port (dev->dsa_ptr), and so, this was incompatible with any attempts to add any data encapsulation and hide DSA data structures from the outside world. Link: https://lore.kernel.org/netdev/20230403083019.120b72fd@kernel.org/ Signed-off-by: Vladimir Oltean Reviewed-by: Florian Fainelli Signed-off-by: David S. Miller --- include/linux/netdevice.h | 6 ------ include/net/dsa_stubs.h | 48 +++++++++++++++++++++++++++++++++++++++++++++++ net/Makefile | 2 +- net/core/dev.c | 2 +- net/core/dev_ioctl.c | 12 ++---------- net/dsa/Makefile | 6 ++++++ net/dsa/dsa.c | 19 +++++++++++++++++++ net/dsa/master.c | 2 +- net/dsa/master.h | 2 +- net/dsa/slave.c | 11 ----------- net/dsa/stubs.c | 10 ++++++++++ 11 files changed, 89 insertions(+), 31 deletions(-) create mode 100644 include/net/dsa_stubs.h create mode 100644 net/dsa/stubs.c (limited to 'net/dsa/master.h') diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index a740be3bb911..1c25b39681b3 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -2878,7 +2878,6 @@ enum netdev_cmd { NETDEV_OFFLOAD_XSTATS_REPORT_USED, NETDEV_OFFLOAD_XSTATS_REPORT_DELTA, NETDEV_XDP_FEAT_CHANGE, - NETDEV_PRE_CHANGE_HWTSTAMP, }; const char *netdev_cmd_to_name(enum netdev_cmd cmd); @@ -2929,11 +2928,6 @@ struct netdev_notifier_pre_changeaddr_info { const unsigned char *dev_addr; }; -struct netdev_notifier_hwtstamp_info { - struct netdev_notifier_info info; /* must be first */ - struct kernel_hwtstamp_config *config; -}; - enum netdev_offload_xstats_type { NETDEV_OFFLOAD_XSTATS_TYPE_L3 = 1, }; diff --git a/include/net/dsa_stubs.h b/include/net/dsa_stubs.h new file mode 100644 index 000000000000..361811750a54 --- /dev/null +++ b/include/net/dsa_stubs.h @@ -0,0 +1,48 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * include/net/dsa_stubs.h - Stubs for the Distributed Switch Architecture framework + */ + +#include +#include +#include +#include + +#if IS_ENABLED(CONFIG_NET_DSA) + +extern const struct dsa_stubs *dsa_stubs; + +struct dsa_stubs { + int (*master_hwtstamp_validate)(struct net_device *dev, + const struct kernel_hwtstamp_config *config, + struct netlink_ext_ack *extack); +}; + +static inline int dsa_master_hwtstamp_validate(struct net_device *dev, + const struct kernel_hwtstamp_config *config, + struct netlink_ext_ack *extack) +{ + if (!netdev_uses_dsa(dev)) + return 0; + + /* rtnl_lock() is a sufficient guarantee, because as long as + * netdev_uses_dsa() returns true, the dsa_core module is still + * registered, and so, dsa_unregister_stubs() couldn't have run. + * For netdev_uses_dsa() to start returning false, it would imply that + * dsa_master_teardown() has executed, which requires rtnl_lock(). + */ + ASSERT_RTNL(); + + return dsa_stubs->master_hwtstamp_validate(dev, config, extack); +} + +#else + +static inline int dsa_master_hwtstamp_validate(struct net_device *dev, + const struct kernel_hwtstamp_config *config, + struct netlink_ext_ack *extack) +{ + return 0; +} + +#endif diff --git a/net/Makefile b/net/Makefile index 0914bea9c335..87592009366f 100644 --- a/net/Makefile +++ b/net/Makefile @@ -24,7 +24,7 @@ obj-$(CONFIG_PACKET) += packet/ obj-$(CONFIG_NET_KEY) += key/ obj-$(CONFIG_BRIDGE) += bridge/ obj-$(CONFIG_NET_DEVLINK) += devlink/ -obj-$(CONFIG_NET_DSA) += dsa/ +obj-y += dsa/ obj-$(CONFIG_ATALK) += appletalk/ obj-$(CONFIG_X25) += x25/ obj-$(CONFIG_LAPB) += lapb/ diff --git a/net/core/dev.c b/net/core/dev.c index 7ce5985be84b..480600a075ce 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -1612,7 +1612,7 @@ const char *netdev_cmd_to_name(enum netdev_cmd cmd) N(SVLAN_FILTER_PUSH_INFO) N(SVLAN_FILTER_DROP_INFO) N(PRE_CHANGEADDR) N(OFFLOAD_XSTATS_ENABLE) N(OFFLOAD_XSTATS_DISABLE) N(OFFLOAD_XSTATS_REPORT_USED) N(OFFLOAD_XSTATS_REPORT_DELTA) - N(XDP_FEAT_CHANGE) N(PRE_CHANGE_HWTSTAMP) + N(XDP_FEAT_CHANGE) } #undef N return "UNKNOWN_NETDEV_EVENT"; diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c index 6d772837eb3f..3730945ee294 100644 --- a/net/core/dev_ioctl.c +++ b/net/core/dev_ioctl.c @@ -7,7 +7,7 @@ #include #include #include -#include +#include #include #include "dev.h" @@ -259,9 +259,6 @@ static int dev_get_hwtstamp(struct net_device *dev, struct ifreq *ifr) static int dev_set_hwtstamp(struct net_device *dev, struct ifreq *ifr) { - struct netdev_notifier_hwtstamp_info info = { - .info.dev = dev, - }; struct kernel_hwtstamp_config kernel_cfg; struct netlink_ext_ack extack = {}; struct hwtstamp_config cfg; @@ -276,12 +273,7 @@ static int dev_set_hwtstamp(struct net_device *dev, struct ifreq *ifr) if (err) return err; - info.info.extack = &extack; - info.config = &kernel_cfg; - - err = call_netdevice_notifiers_info(NETDEV_PRE_CHANGE_HWTSTAMP, - &info.info); - err = notifier_to_errno(err); + err = dsa_master_hwtstamp_validate(dev, &kernel_cfg, &extack); if (err) { if (extack._msg) netdev_err(dev, "%s\n", extack._msg); diff --git a/net/dsa/Makefile b/net/dsa/Makefile index cc7e93a562fe..3835de286116 100644 --- a/net/dsa/Makefile +++ b/net/dsa/Makefile @@ -1,4 +1,10 @@ # SPDX-License-Identifier: GPL-2.0 + +# the stubs are built-in whenever DSA is built-in or module +ifdef CONFIG_NET_DSA +obj-y := stubs.o +endif + # the core obj-$(CONFIG_NET_DSA) += dsa_core.o dsa_core-y += \ diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c index e5f156940c67..ab1afe67fd18 100644 --- a/net/dsa/dsa.c +++ b/net/dsa/dsa.c @@ -17,6 +17,7 @@ #include #include #include +#include #include #include "devlink.h" @@ -1702,6 +1703,20 @@ bool dsa_mdb_present_in_other_db(struct dsa_switch *ds, int port, } EXPORT_SYMBOL_GPL(dsa_mdb_present_in_other_db); +static const struct dsa_stubs __dsa_stubs = { + .master_hwtstamp_validate = __dsa_master_hwtstamp_validate, +}; + +static void dsa_register_stubs(void) +{ + dsa_stubs = &__dsa_stubs; +} + +static void dsa_unregister_stubs(void) +{ + dsa_stubs = NULL; +} + static int __init dsa_init_module(void) { int rc; @@ -1721,6 +1736,8 @@ static int __init dsa_init_module(void) if (rc) goto netlink_register_fail; + dsa_register_stubs(); + return 0; netlink_register_fail: @@ -1735,6 +1752,8 @@ module_init(dsa_init_module); static void __exit dsa_cleanup_module(void) { + dsa_unregister_stubs(); + rtnl_link_unregister(&dsa_link_ops); dsa_slave_unregister_notifier(); diff --git a/net/dsa/master.c b/net/dsa/master.c index c2cabe6248b1..6be89ab0cc01 100644 --- a/net/dsa/master.c +++ b/net/dsa/master.c @@ -198,7 +198,7 @@ static void dsa_master_get_strings(struct net_device *dev, uint32_t stringset, /* Deny PTP operations on master if there is at least one switch in the tree * that is PTP capable. */ -int dsa_master_pre_change_hwtstamp(struct net_device *dev, +int __dsa_master_hwtstamp_validate(struct net_device *dev, const struct kernel_hwtstamp_config *config, struct netlink_ext_ack *extack) { diff --git a/net/dsa/master.h b/net/dsa/master.h index 80842f4e27f7..76e39d3ec909 100644 --- a/net/dsa/master.h +++ b/net/dsa/master.h @@ -15,7 +15,7 @@ int dsa_master_lag_setup(struct net_device *lag_dev, struct dsa_port *cpu_dp, struct netlink_ext_ack *extack); void dsa_master_lag_teardown(struct net_device *lag_dev, struct dsa_port *cpu_dp); -int dsa_master_pre_change_hwtstamp(struct net_device *dev, +int __dsa_master_hwtstamp_validate(struct net_device *dev, const struct kernel_hwtstamp_config *config, struct netlink_ext_ack *extack); diff --git a/net/dsa/slave.c b/net/dsa/slave.c index 8abc1658ac47..165bb2cb8431 100644 --- a/net/dsa/slave.c +++ b/net/dsa/slave.c @@ -3289,7 +3289,6 @@ static int dsa_master_changeupper(struct net_device *dev, static int dsa_slave_netdevice_event(struct notifier_block *nb, unsigned long event, void *ptr) { - struct netlink_ext_ack *extack = netdev_notifier_info_to_extack(ptr); struct net_device *dev = netdev_notifier_info_to_dev(ptr); switch (event) { @@ -3419,16 +3418,6 @@ static int dsa_slave_netdevice_event(struct notifier_block *nb, return NOTIFY_OK; } - case NETDEV_PRE_CHANGE_HWTSTAMP: { - struct netdev_notifier_hwtstamp_info *info = ptr; - int err; - - if (!netdev_uses_dsa(dev)) - return NOTIFY_DONE; - - err = dsa_master_pre_change_hwtstamp(dev, info->config, extack); - return notifier_from_errno(err); - } default: break; } diff --git a/net/dsa/stubs.c b/net/dsa/stubs.c new file mode 100644 index 000000000000..2ed8a6c85fbf --- /dev/null +++ b/net/dsa/stubs.c @@ -0,0 +1,10 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Stubs for DSA functionality called by the core network stack. + * These are necessary because CONFIG_NET_DSA can be a module, and built-in + * code cannot directly call symbols exported by modules. + */ +#include + +const struct dsa_stubs *dsa_stubs; +EXPORT_SYMBOL_GPL(dsa_stubs); -- cgit v1.2.3