linux.git/drivers/net/netdevsim/bus.c, branch v6.12.80

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

2026-01-17T15:31:24+00:00

[ Upstream commit d83dddffe1904e4a576d11a541878850a8e64cd2 ]

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 
Signed-off-by: Sasha Levin

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

netdevsim: rename 'driver' entry points

2021-11-01T13:29:41+00:00

Rename functions serving as driver entry points
from nsim_dev_... to nsim_drv_... this makes the
API boundary between bus and dev clearer.

Signed-off-by: Jakub Kicinski 
Signed-off-by: David S. Miller

netdevsim: move max vf config to dev

2021-11-01T13:29:41+00:00

max_vfs is a strange little beast because the file
hangs off of nsim's debugfs, but it configures a field
in the bus device. Move it to dev.c, let's look at it
as if the device driver was imposing VF limit based
on FW info (like pci_sriov_set_totalvfs()).

Again, when moving refactor the function not to hold
the vfs lock pointlessly while parsing the input.
Wrap the access from the read side in READ_ONCE()
to appease concurrency checkers. Do not check if
return value from snprintf() is negative...

Signed-off-by: Jakub Kicinski 
Signed-off-by: David S. Miller