netdev - Re: [PATCH net-next v3 8/8] selftests: drv-net: add a TCP ping test case (and useful helpers)

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Message-ID: <662131d77b55d_ec9b92945@willemb.c.googlers.com.notmuch>
Date: Thu, 18 Apr 2024 10:44:39 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Jakub Kicinski <kuba@...nel.org>, 
 davem@...emloft.net
Cc: netdev@...r.kernel.org, 
 edumazet@...gle.com, 
 pabeni@...hat.com, 
 shuah@...nel.org, 
 petrm@...dia.com, 
 linux-kselftest@...r.kernel.org, 
 willemdebruijn.kernel@...il.com, 
 Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH net-next v3 8/8] selftests: drv-net: add a TCP ping test
 case (and useful helpers)

Jakub Kicinski wrote:
> More complex tests often have to spawn a background process,
> like a server which will respond to requests or tcpdump.
> 
> Add support for creating such processes using the with keyword:
> 
>   with bkg("my-daemon", ..):
>      # my-daemon is alive in this block
> 
> My initial thought was to add this support to cmd() directly
> but it runs the command in the constructor, so by the time
> we __enter__ it's too late to make sure we used "background=True".
> 
> Second useful helper transplanted from net_helper.sh is
> wait_port_listen().
> 
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> ---
>  tools/testing/selftests/drivers/net/ping.py | 24 +++++++++++++--
>  tools/testing/selftests/net/lib/py/utils.py | 33 +++++++++++++++++++++
>  2 files changed, 55 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/drivers/net/ping.py b/tools/testing/selftests/drivers/net/ping.py
> index 58aefd3e740f..8532e3be72ba 100755
> --- a/tools/testing/selftests/drivers/net/ping.py
> +++ b/tools/testing/selftests/drivers/net/ping.py
> @@ -1,9 +1,12 @@
>  #!/usr/bin/env python3
>  # SPDX-License-Identifier: GPL-2.0
>  
> -from lib.py import ksft_run, ksft_exit, KsftXfailEx
> +import random
> +
> +from lib.py import ksft_run, ksft_exit
> +from lib.py import ksft_eq, KsftXfailEx
>  from lib.py import NetDrvEpEnv
> -from lib.py import cmd
> +from lib.py import bkg, cmd, wait_port_listen
>  
>  
>  def test_v4(cfg) -> None:
> @@ -22,6 +25,23 @@ from lib.py import cmd
>      cmd(f"ping -c 1 -W0.5 {cfg.v6}", host=cfg.remote)
>  
>  
> +def test_tcp(cfg) -> None:
> +    port = random.randrange(1024 + (1 << 15))
> +    with bkg(f"nc -l {cfg.addr} {port}") as nc:
> +        wait_port_listen(port)
> +
> +        cmd(f"echo ping | nc {cfg.addr} {port}",
> +            shell=True, host=cfg.remote)
> +    ksft_eq(nc.stdout.strip(), "ping")
> +
> +    port = random.randrange(1024 + (1 << 15))
> +    with bkg(f"nc -l {cfg.remote_addr} {port}", host=cfg.remote) as nc:
> +        wait_port_listen(port, host=cfg.remote)
> +
> +        cmd(f"echo ping | nc {cfg.remote_addr} {port}", shell=True)
> +    ksft_eq(nc.stdout.strip(), "ping")
> +

There are different netcat implementations floating around.

I notice that I have to pass -N on the client to terminate the
connection after EOF. Else both peers keep the connection open,
waiting for input. And explicitly pass -6 if passing an IPv6
address. I think this is the one that ships with Debian..