netdev - Fw: [Bug 215793] New: ip netns del is asynchronous??? -- very unexpected and puzzling

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Message-ID: <20220405102350.61dce151@hermes.local>
Date:   Tue, 5 Apr 2022 10:23:50 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     netdev@...r.kernel.org
Subject: Fw: [Bug 215793] New: ip netns del is asynchronous??? -- very
 unexpected and puzzling



Begin forwarded message:

Date: Sat, 02 Apr 2022 12:14:36 +0000
From: bugzilla-daemon@...nel.org
To: stephen@...workplumber.org
Subject: [Bug 215793] New: ip netns del is asynchronous??? -- very unexpected and puzzling


https://bugzilla.kernel.org/show_bug.cgi?id=215793

            Bug ID: 215793
           Summary: ip netns del is asynchronous??? -- very unexpected and
                    puzzling
           Product: Networking
           Version: 2.5
    Kernel Version: 5.10.106
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Other
          Assignee: stephen@...workplumber.org
          Reporter: rm+bko@...anrm.net
        Regression: No

Hello,

I have a script like this:

  ip netns del test-ns
  ip netns add test-ns
  ip link add tun-test type gre local any remote 8.8.8.8
  ip link set tun-test netns test-ns

As is, the script will fail exactly every other time:

---------------
# ./nstest.sh 
RTNETLINK answers: File exists
Cannot find device "tun-test"

# ./nstest.sh 

# ./nstest.sh 
RTNETLINK answers: File exists
Cannot find device "tun-test"

# ./nstest.sh 

# ./nstest.sh 
RTNETLINK answers: File exists
Cannot find device "tun-test"

# ./nstest.sh 

# ./nstest.sh 
RTNETLINK answers: File exists
Cannot find device "tun-test"

# ./nstest.sh 

# ./nstest.sh 
RTNETLINK answers: File exists
Cannot find device "tun-test"

# ./nstest.sh 

# ./nstest.sh 
RTNETLINK answers: File exists
Cannot find device "tun-test"

---------------
That's because "ip netns del" seems to return without actually finishing to
fully delete the NS. Adding a "sleep 1" after the first line, makes the script
complete successfully every time. This is a very unexpected behavior. I would
ask for a better workaround than "sleep 1", but I believe there should be no
workaround, and the script should reliably work as posted.

Hope you can consider changing this.

Thanks!

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