Re: [PATCH net-next 1/4] selftests: drv-net: try to check if port is in use

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

Jakub Kicinski wrote:
> We use random ports for communication. As Willem predicted
> this leads to occasional failures. Try to check if port is
> already in use by opening a socket and binding to that port.
> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> ---
>  tools/testing/selftests/net/lib/py/utils.py | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/net/lib/py/utils.py b/tools/testing/selftests/net/lib/py/utils.py
> index 0540ea24921d..9fa9ec720c89 100644
> --- a/tools/testing/selftests/net/lib/py/utils.py
> +++ b/tools/testing/selftests/net/lib/py/utils.py
> @@ -3,6 +3,7 @@
>  import json as _json
>  import random
>  import re
> +import socket
>  import subprocess
>  import time
>  
> @@ -81,7 +82,17 @@ import time
>      """
>      Get unprivileged port, for now just random, one day we may decide to check if used.
>      """
> -    return random.randint(10000, 65535)
> +    while True:
> +        port = random.randint(10000, 65535)
> +        try:
> +            with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
> +                s.bind(("", port))
> +            with socket.socket(socket.AF_INET6, socket.SOCK_STREAM) as s:
> +                s.bind(("", port))

Is the separate AF_INET needed? As AF_INET6 is not IPV6_V6ONLY.

The following correctly fails in the second bind

    with socket.socket(socket.AF_INET6, socket.SOCK_STREAM) as s6:
      s6.bind(("", 8000))
      with socket.socket(socket.AF_INET6, socket.SOCK_STREAM) as s4:
          s4.bind(("", 8000))


> +            return port
> +        except OSError as e:
> +            if e.errno != 98:  # already in use
> +                raise
>  
>  
>  def wait_port_listen(port, proto="tcp", ns=None, host=None, sleep=0.005, deadline=5):
> -- 
> 2.45.2
>