bareudp: Support per-netns netdev unregistration.

bareudp_exit_rtnl_net() iterates bareudp devices whose sockets
are in the dying netns and queues them for destruction.

So the devices may reside in different netns.

Let's use unregister_netdevice_queue_net() to support per-netns
device unregistration.

list_del() is changed to list_del_init() to avoid queueing the
same device twice.

Even after bareudp_exit_rtnl_net() queues a cross-netns bareudp
device, bareudp_dellink() could be called concurrently for it
(once RTNL is removed).  In such a case, __rtnl_net_unlock() will
perform the unregistration.

Note that bareudp uses register_pernet_subsys() instead of _device(),
so default_device_exit_batch() guarantees that the async per-netns
works are flushed before ->exit().

Tested:

1. Create bareudp device across two netns.

  # ip netns add ns1
  # ip netns add ns2
  # ip -n ns1 link add bareudp0 link-netns ns2 type bareudp \
    dstport 9292 ethertype ipv4

2. Run bpftrace to check that bareudp_uninit() is called between
   ->exit_rtnl() and ->exit().

  # bpftrace -e '#include <linux/netdevice.h>
  kprobe:bareudp_uninit {
      $dev = (struct net_device *)arg0;
      printf("PID: %d | DEV: %s%s\n", pid, $dev->name, kstack());
  }
  kprobe:bareudp_exit_rtnl_net,
  kprobe:bareudp_exit_net {
      printf("PID: %d%s\n", pid, kstack());
  }'

3. Remove the netns where the bareudp socket resides

  # ip netns del ns2

Now, we can see bareudp0 is unregistered by per-netns work
instead of cleanup_net() and it finishes before ->exit() to
avoid WARN_ON_ONCE(!list_empty(&bn->bareudp_list)) there.

  PID: 576
          bareudp_exit_rtnl_net+5
          ops_undo_list+702
          cleanup_net+1122
          process_scheduled_works+2538
  ...
  PID: 470 | DEV: bareudp0
          bareudp_uninit+5
          unregister_netdevice_many_notify+7129
          unregister_netdevice_many_net+1050
          rtnl_net_work_func+136
          process_scheduled_works+2538
  ...
  PID: 576
          bareudp_exit_net+5
          ops_undo_list+1064
          cleanup_net+1122
          process_scheduled_works+2538

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260703001009.1572444-11-kuniyu@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

0 files changed, 0 insertions, 0 deletions