kernel/linux.git/drivers/net/netdevsim/bus.c, branch v6.19.11

net: netdevsim: fix inconsistent carrier state after link/unlink

2026-01-07T02:04:00+00:00

This patch fixes the edge case behavior on ifup/ifdown and linking/unlinking two netdevsim interfaces: 1. unlink two interfaces netdevsim1 and netdevsim2 2. ifdown netdevsim1 3. ifup netdevsim1 4. link two interfaces netdevsim1 and netdevsim2 5. (Now two interfaces are linked in terms of netdevsim peer, but carrier state of the two interfaces remains DOWN.) This inconsistent behavior is caused by the current implementation, which only cares about the "link, then ifup" order, not "ifup, then link" order. This patch fixes the inconsistency by calling netif_carrier_on() when two netdevsim interfaces are linked. This patch fixes buggy behavior on NetworkManager-based systems which causes the netdevsim test to fail with the following error: # timeout set to 600 # selftests: drivers/net/netdevsim: peer.sh # 2025/12/25 00:54:03 socat[9115] W address is opened in read-write mode but only supports read-only # 2025/12/25 00:56:17 socat[9115] W connect(7, AF=2 192.168.1.1:1234, 16): Connection timed out # 2025/12/25 00:56:17 socat[9115] E TCP:192.168.1.1:1234: Connection timed out # expected 3 bytes, got 0 # 2025/12/25 00:56:17 socat[9109] W exiting on signal 15 not ok 13 selftests: drivers/net/netdevsim: peer.sh # exit=1 This patch also solves timeout on TCP Fast Open (TFO) test in NetworkManager-based systems because it also depends on netdevsim's carrier consistency. Fixes: 1a8fed52f7be ("netdevsim: set the carrier when the device goes up") Signed-off-by: Yohei Kojima Reviewed-by: Breno Leitao Link: https://patch.msgid.link/602c9e1ba5bb2ee1997bb38b1d866c9c3b807ae9.1767624906.git.yk@y-koj.net Signed-off-by: Jakub Kicinski

netdevsim: implement peer queue flow control

2025-07-15T00:36:50+00:00

Add flow control mechanism between paired netdevsim devices to stop the TX queue during high traffic scenarios. When a receive queue becomes congested (approaching NSIM_RING_SIZE limit), the corresponding transmit queue on the peer device is stopped using netif_subqueue_try_stop(). Once the receive queue has sufficient capacity again, the peer's transmit queue is resumed with netif_tx_wake_queue(). Key changes: * Add nsim_stop_peer_tx_queue() to pause peer TX when RX queue is full * Add nsim_start_peer_tx_queue() to resume peer TX when RX queue drains * Implement queue mapping validation to ensure TX/RX queue count match * Wake all queues during device unlinking to prevent stuck queues * Use RCU protection when accessing peer device references * wake the queues when changing the queue numbers * Remove IFF_NO_QUEUE given it will enqueue packets now The flow control only activates when devices have matching TX/RX queue counts to ensure proper queue mapping. Suggested-by: Jakub Kicinski Signed-off-by: Breno Leitao Link: https://patch.msgid.link/20250711-netdev_flow_control-v3-1-aa1d5a155762@debian.org Signed-off-by: Jakub Kicinski

net: netdevsim: Support setting dev->perm_addr on port creation

2025-07-12T00:00:18+00:00

Network management daemons that match on the device permanent address currently have no virtual interface types to test against. NetworkManager, in particular, has carried an out of tree patch to set the permanent address on netdevsim devices to use in its CI for this purpose. To support this use case, support setting netdev->perm_addr when creating a netdevsim port. Reviewed-by: Simon Horman Signed-off-by: Toke Høiland-Jørgensen Link: https://patch.msgid.link/20250710-netdevsim-perm_addr-v4-1-c9db2fecf3bf@redhat.com Signed-off-by: Jakub Kicinski

netdevsim: allow two netdevsim ports to be connected

2024-03-01T10:43:10+00:00

Add two netdevsim bus attribute to sysfs: /sys/bus/netdevsim/link_device /sys/bus/netdevsim/unlink_device Writing "A M B N" to link_device will link netdevsim M in netnsid A with netdevsim N in netnsid B. Writing "A M" to unlink_device will unlink netdevsim M in netnsid A from its peer, if any. rtnl_lock is taken to ensure nothing changes during the linking. Signed-off-by: David Wei Reviewed-by: Maciek Machnikowski Signed-off-by: David S. Miller

net: netdevsim: constify the struct device_type usage

2024-02-21T09:45:23+00:00

Since commit aed65af1cc2f ("drivers: make device_type const"), the driver core can properly handle constant struct device_type. Move the nsim_bus_dev_type variable to be a constant structure as well, placing it into read-only memory which can not be modified at runtime. Cc: Greg Kroah-Hartman Signed-off-by: Ricardo B. Marliere Reviewed-by: Simon Horman Signed-off-by: David S. Miller

netdevsim: make nsim_bus const

2024-02-07T13:40:27+00:00

Now that the driver core can properly handle constant struct bus_type, move the nsim_bus variable to be a constant structure as well, placing it into read-only memory which can not be modified at runtime. Cc: Greg Kroah-Hartman Suggested-by: Greg Kroah-Hartman Signed-off-by: Ricardo B. Marliere Reviewed-by: Greg Kroah-Hartman Signed-off-by: David S. Miller

netdevsim: Block until all devices are released

2023-10-27T21:48:36+00:00

Like other buses, devices on the netdevsim bus have a release callback that is invoked when the reference count of the device drops to zero. However, unlike other buses such as PCI, the release callback is not necessarily built into the kernel, as netdevsim can be built as a module. The above is problematic as nothing prevents the module from being unloaded before the release callback has been invoked, which can happen asynchronously. One such example can be found in commit a380687200e0 ("devlink: take device reference for devlink object") where devlink calls put_device() from an RCU callback. The issue is not theoretical and the reproducer in [1] can reliably crash the kernel. The conclusion of this discussion was that the issue should be solved in netdevsim, which is what this patch is trying to do. Add a reference count that is increased when a device is added to the bus and decreased when a device is released. Signal a completion when the reference count drops to zero and wait for the completion when unloading the module so that the module will not be unloaded before all the devices were released. The reference count is initialized to one so that completion is only signaled when unloading the module. With this patch, the reproducer in [1] no longer crashes the kernel. [1] https://lore.kernel.org/netdev/20230619125015.1541143-2-idosch@nvidia.com/ Fixes: a380687200e0 ("devlink: take device reference for devlink object") Signed-off-by: Ido Schimmel Reviewed-by: Jiri Pirko Link: https://lore.kernel.org/r/20231026083343.890689-1-idosch@nvidia.com Signed-off-by: Jakub Kicinski

driver core: bus: mark the struct bus_type for sysfs callbacks as constant

2023-03-23T12:20:40+00:00

struct bus_type should never be modified in a sysfs callback as there is nothing in the structure to modify, and frankly, the structure is almost never used in a sysfs callback, so mark it as constant to allow struct bus_type to be moved to read-only memory. Cc: "David S. Miller" Cc: "James E.J. Bottomley" Cc: "K. Y. Srinivasan" Cc: Alexander Gordeev Cc: Alexandre Bounine Cc: Alison Schofield Cc: Ben Widawsky Cc: Dexuan Cui Cc: Eric Dumazet Cc: Haiyang Zhang Cc: Hannes Reinecke Cc: Harald Freudenberger Cc: Heiko Carstens Cc: Hu Haowen Cc: Jakub Kicinski Cc: Jens Axboe Cc: Jonathan Corbet Cc: Laurentiu Tudor Cc: Matt Porter Cc: Michael Ellerman Cc: Paolo Abeni Cc: Stuart Yoder Cc: Vasily Gorbik Cc: Vishal Verma Cc: Yanteng Si Acked-by: Ilya Dryomov # rbd Acked-by: Ira Weiny # cxl Reviewed-by: Alex Shi Acked-by: Iwona Winiarska Acked-by: Dan Williams Acked-by: Bjorn Helgaas # pci Acked-by: Wei Liu Acked-by: Martin K. Petersen # scsi Link: https://lore.kernel.org/r/20230313182918.1312597-23-gregkh@linuxfoundation.org Signed-off-by: Greg Kroah-Hartman

netdevsim: fix memory leak in nsim_bus_dev_new()

2022-10-27T17:47:09+00:00

If device_register() failed in nsim_bus_dev_new(), the value of reference in nsim_bus_dev->dev is 1. obj->name in nsim_bus_dev->dev will not be released. unreferenced object 0xffff88810352c480 (size 16): comm "echo", pid 5691, jiffies 4294945921 (age 133.270s) hex dump (first 16 bytes): 6e 65 74 64 65 76 73 69 6d 31 00 00 00 00 00 00 netdevsim1...... backtrace: [<000000005e2e5e26>] __kmalloc_node_track_caller+0x3a/0xb0 [<0000000094ca4fc8>] kvasprintf+0xc3/0x160 [<00000000aad09bcc>] kvasprintf_const+0x55/0x180 [<000000009bac868d>] kobject_set_name_vargs+0x56/0x150 [<000000007c1a5d70>] dev_set_name+0xbb/0xf0 [<00000000ad0d126b>] device_add+0x1f8/0x1cb0 [<00000000c222ae24>] new_device_store+0x3b6/0x5e0 [<0000000043593421>] bus_attr_store+0x72/0xa0 [<00000000cbb1833a>] sysfs_kf_write+0x106/0x160 [<00000000d0dedb8a>] kernfs_fop_write_iter+0x3a8/0x5a0 [<00000000770b66e2>] vfs_write+0x8f0/0xc80 [<0000000078bb39be>] ksys_write+0x106/0x210 [<00000000005e55a4>] do_syscall_64+0x35/0x80 [<00000000eaa40bbc>] entry_SYSCALL_64_after_hwframe+0x46/0xb0 Fixes: 40e4fe4ce115 ("netdevsim: move device registration and related code to bus.c") Signed-off-by: Zhengchao Shao Link: https://lore.kernel.org/r/20221026015405.128795-1-shaozhengchao@huawei.com Signed-off-by: Jakub Kicinski

netdevsim: convert driver to use unlocked devlink API during init/fini

2022-07-19T03:10:48+00:00

Prepare for devlink reload being called with devlink->lock held and convert the netdevsim driver to use unlocked devlink API during init and fini flows. Take devl_lock() in reload_down() and reload_up() ops in the meantime before reload cmd is converted to take the lock itself. Signed-off-by: Jiri Pirko Signed-off-by: Jakub Kicinski