user/sven/linux.git/include/linux/rtnetlink.h, branch v6.1.152

rtnl: add helper to check if a notification is needed

2025-04-25T08:43:25Z

[ Upstream commit 8439109b76a3c405808383bf9dd532fc4b9c2dbd ] Building on the rtnl_has_listeners helper, add the rtnl_notify_needed helper to check if we can bail out early in the notification routines. Reviewed-by: Jiri Pirko Reviewed-by: Simon Horman Signed-off-by: Victor Nogueira Signed-off-by: Pedro Tammela Link: https://lore.kernel.org/r/20231208192847.714940-3-pctammela@mojatatu.com Signed-off-by: Jakub Kicinski Stable-dep-of: 369609fc6272 ("tc: Ensure we have enough buffer space when sending filter netlink notifications") Signed-off-by: Sasha Levin

rtnl: add helper to check if rtnl group has listeners

2025-04-25T08:43:25Z

[ Upstream commit c5e2a973448d958feb7881e4d875eac59fdeff3d ] As of today, rtnl code creates a new skb and unconditionally fills and broadcasts it to the relevant group. For most operations this is okay and doesn't waste resources in general. When operations are done without the rtnl_lock, as in tc-flower, such skb allocation, message fill and no-op broadcasting can happen in all cores of the system, which contributes to system pressure and wastes precious cpu cycles when no one will receive the built message. Introduce this helper so rtnetlink operations can simply check if someone is listening and then proceed if necessary. Reviewed-by: Jiri Pirko Reviewed-by: Simon Horman Signed-off-by: Jamal Hadi Salim Signed-off-by: Victor Nogueira Signed-off-by: Pedro Tammela Link: https://lore.kernel.org/r/20231208192847.714940-2-pctammela@mojatatu.com Signed-off-by: Jakub Kicinski Stable-dep-of: 369609fc6272 ("tc: Ensure we have enough buffer space when sending filter netlink notifications") Signed-off-by: Sasha Levin

net: sched: use queue_mapping to pick tx queue

2022-04-19T10:20:45Z

This patch fixes issue: * If we install tc filters with act_skbedit in clsact hook. It doesn't work, because netdev_core_pick_tx() overwrites queue_mapping. $ tc filter ... action skbedit queue_mapping 1 And this patch is useful: * We can use FQ + EDT to implement efficient policies. Tx queues are picked by xps, ndo_select_queue of netdev driver, or skb hash in netdev_core_pick_tx(). In fact, the netdev driver, and skb hash are _not_ under control. xps uses the CPUs map to select Tx queues, but we can't figure out which task_struct of pod/containter running on this cpu in most case. We can use clsact filters to classify one pod/container traffic to one Tx queue. Why ? In containter networking environment, there are two kinds of pod/ containter/net-namespace. One kind (e.g. P1, P2), the high throughput is key in these applications. But avoid running out of network resource, the outbound traffic of these pods is limited, using or sharing one dedicated Tx queues assigned HTB/TBF/FQ Qdisc. Other kind of pods (e.g. Pn), the low latency of data access is key. And the traffic is not limited. Pods use or share other dedicated Tx queues assigned FIFO Qdisc. This choice provides two benefits. First, contention on the HTB/FQ Qdisc lock is significantly reduced since fewer CPUs contend for the same queue. More importantly, Qdisc contention can be eliminated completely if each CPU has its own FIFO Qdisc for the second kind of pods. There must be a mechanism in place to support classifying traffic based on pods/container to different Tx queues. Note that clsact is outside of Qdisc while Qdisc can run a classifier to select a sub-queue under the lock. In general recording the decision in the skb seems a little heavy handed. This patch introduces a per-CPU variable, suggested by Eric. The xmit.skip_txqueue flag is firstly cleared in __dev_queue_xmit(). - Tx Qdisc may install that skbedit actions, then xmit.skip_txqueue flag is set in qdisc->enqueue() though tx queue has been selected in netdev_tx_queue_mapping() or netdev_core_pick_tx(). That flag is cleared firstly in __dev_queue_xmit(), is useful: - Avoid picking Tx queue with netdev_tx_queue_mapping() in next netdev in such case: eth0 macvlan - eth0.3 vlan - eth0 ixgbe-phy: For example, eth0, macvlan in pod, which root Qdisc install skbedit queue_mapping, send packets to eth0.3, vlan in host. In __dev_queue_xmit() of eth0.3, clear the flag, does not select tx queue according to skb->queue_mapping because there is no filters in clsact or tx Qdisc of this netdev. Same action taked in eth0, ixgbe in Host. - Avoid picking Tx queue for next packet. If we set xmit.skip_txqueue in tx Qdisc (qdisc->enqueue()), the proper way to clear it is clearing it in __dev_queue_xmit when processing next packets. For performance reasons, use the static key. If user does not config the NET_EGRESS, the patch will not be compiled. +----+ +----+ +----+ | P1 | | P2 | | Pn | +----+ +----+ +----+ | | | +-----------+-----------+ | | clsact/skbedit | MQ v +-----------+-----------+ | q0 | q1 | qn v v v HTB/FQ HTB/FQ ... FIFO Cc: Jamal Hadi Salim Cc: Cong Wang Cc: Jiri Pirko Cc: "David S. Miller" Cc: Jakub Kicinski Cc: Jonathan Lemon Cc: Eric Dumazet Cc: Alexander Lobakin Cc: Paolo Abeni Cc: Talal Ahmad Cc: Kevin Hao Cc: Ilias Apalodimas Cc: Kees Cook Cc: Kumar Kartikeya Dwivedi Cc: Antoine Tenart Cc: Wei Wang Cc: Arnd Bergmann Suggested-by: Eric Dumazet Signed-off-by: Tonghao Zhang Acked-by: Jamal Hadi Salim Signed-off-by: Paolo Abeni

net: rtnetlink: Add UAPI toggle for IFLA_OFFLOAD_XSTATS_L3_STATS

2022-03-03T10:37:23Z

The offloaded HW stats are designed to allow per-netdevice enablement and disablement. Add an attribute, IFLA_STATS_SET_OFFLOAD_XSTATS_L3_STATS, which should be carried by the RTM_SETSTATS message, and expresses a desire to toggle L3 offload xstats on or off. As part of the above, add an exported function rtnl_offload_xstats_notify() that drivers can use when they have installed or deinstalled the counters backing the HW stats. At this point, it is possible to enable, disable and query L3 offload xstats on netdevices. (However there is no driver actually implementing these.) Signed-off-by: Petr Machata Signed-off-by: Ido Schimmel Signed-off-by: David S. Miller

net: sched: extend Qdisc with rcu

2018-09-26T03:17:35Z

Currently, Qdisc API functions assume that users have rtnl lock taken. To implement rtnl unlocked classifiers update interface, Qdisc API must be extended with functions that do not require rtnl lock. Extend Qdisc structure with rcu. Implement special version of put function qdisc_put_unlocked() that is called without rtnl lock taken. This function only takes rtnl lock if Qdisc reference counter reached zero and is intended to be used as optimization. Signed-off-by: Vlad Buslov Acked-by: Jiri Pirko Signed-off-by: David S. Miller

net: core: netlink: add helper refcount dec and lock function

2018-09-26T03:17:35Z

Rtnl lock is encapsulated in netlink and cannot be accessed by other modules directly. This means that reference counted objects that rely on rtnl lock cannot use it with refcounter helper function that atomically releases decrements reference and obtains mutex. This patch implements simple wrapper function around refcount_dec_and_lock that obtains rtnl lock if reference counter value reached 0. Signed-off-by: Vlad Buslov Acked-by: Jiri Pirko Signed-off-by: David S. Miller

net: Introduce net_rwsem to protect net_namespace_list

2018-03-29T17:47:53Z

rtnl_lock() is used everywhere, and contention is very high. When someone wants to iterate over alive net namespaces, he/she has no a possibility to do that without exclusive lock. But the exclusive rtnl_lock() in such places is overkill, and it just increases the contention. Yes, there is already for_each_net_rcu() in kernel, but it requires rcu_read_lock(), and this can't be sleepable. Also, sometimes it may be need really prevent net_namespace_list growth, so for_each_net_rcu() is not fit there. This patch introduces new rw_semaphore, which will be used instead of rtnl_mutex to protect net_namespace_list. It is sleepable and allows not-exclusive iterations over net namespaces list. It allows to stop using rtnl_lock() in several places (what is made in next patches) and makes less the time, we keep rtnl_mutex. Here we just add new lock, while the explanation of we can remove rtnl_lock() there are in next patches. Fine grained locks generally are better, then one big lock, so let's do that with net_namespace_list, while the situation allows that. Signed-off-by: Kirill Tkhai Signed-off-by: David S. Miller

net: Rename net_sem to pernet_ops_rwsem

2018-03-27T17:18:09Z

net_sem is some undefined area name, so it will be better to make the area more defined. Rename it to pernet_ops_rwsem for better readability and better intelligibility. Signed-off-by: Kirill Tkhai Signed-off-by: David S. Miller

net: Add rtnl_lock_killable()

2018-03-16T16:31:19Z

rtnl_lock() is widely used mutex in kernel. Some of kernel code does memory allocations under it. In case of memory deficit this may invoke OOM killer, but the problem is a killed task can't exit if it's waiting for the mutex. This may be a reason of deadlock and panic. This patch adds a new primitive, which responds on SIGKILL, and it allows to use it in the places, where we don't want to sleep forever. Signed-off-by: Kirill Tkhai Signed-off-by: David S. Miller

net: Kill net_mutex

2018-02-20T18:23:13Z

We take net_mutex, when there are !async pernet_operations registered, and read locking of net_sem is not enough. But we may get rid of taking the mutex, and just change the logic to write lock net_sem in such cases. This obviously reduces the number of lock operations, we do. Signed-off-by: Kirill Tkhai Signed-off-by: David S. Miller