netdev - Re: [PATCH net-next v4 6/7] selftests: drv-net: add a TCP ping test case (and useful helpers)

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Message-ID: <662269a5a74a8_116a9b29483@willemb.c.googlers.com.notmuch>
Date: Fri, 19 Apr 2024 08:55:01 -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 v4 6/7] 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().
> 
> The test itself uses socat, which insists on v6 addresses
> being wrapped in [], it's not the only command which requires
> this format, so add the wrapped address to env. The hope
> is to save test code from checking if address is v6.
> 
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> ---
>  .../selftests/drivers/net/lib/py/env.py       |  4 +++
>  tools/testing/selftests/drivers/net/ping.py   | 24 ++++++++++++-
>  tools/testing/selftests/net/lib/py/utils.py   | 35 +++++++++++++++++++
>  3 files changed, 62 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/drivers/net/lib/py/env.py b/tools/testing/selftests/drivers/net/lib/py/env.py
> index 579c5b34e6fd..2f62270d59fa 100644
> --- a/tools/testing/selftests/drivers/net/lib/py/env.py
> +++ b/tools/testing/selftests/drivers/net/lib/py/env.py
> @@ -110,6 +110,10 @@ from .remote import Remote
>          self.addr = self.v6 if self.v6 else self.v4
>          self.remote_addr = self.remote_v6 if self.remote_v6 else self.remote_v4
>  
> +        # Bracketed addresses, some commands need IPv6 to be inside []
> +        self.baddr = f"[{self.v6}]" if self.v6 else self.v4
> +        self.remote_baddr = f"[{self.remote_v6}]" if self.remote_v6 else self.remote_v4
> +
>          self.ifname = self.dev['ifname']
>          self.ifindex = self.dev['ifindex']
>  
> diff --git a/tools/testing/selftests/drivers/net/ping.py b/tools/testing/selftests/drivers/net/ping.py
> index 9f65a0764aab..15a0bdcb46e2 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
>  
> +import random
> +
>  from lib.py import ksft_run, ksft_exit
> +from lib.py import ksft_eq
>  from lib.py import NetDrvEpEnv
> -from lib.py import cmd
> +from lib.py import bkg, cmd, wait_port_listen
>  
>  
>  def test_v4(cfg) -> None:
> @@ -16,6 +19,25 @@ 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))

Intended to be 1024 + random.randrange(1 << 15)?

> +
> +    with bkg(f"socat -t 2 -u TCP-LISTEN:{port} STDOUT", exit_wait=True) as nc:

Perhaps add reuseaddr to all tests with hand picked ports?

I guess that here the client initiates the close and hits the
TIME_WAIT. But not sure.

The odds of consecutive tests picking the same random ports are low.
But as we add tests and they are run in continuous testing, that
can become an annoying source of flaky runs.

> +        wait_port_listen(port)
> +
> +        cmd(f"echo ping | socat -t 2 -u STDIN TCP:{cfg.baddr}:{port}",
> +            shell=True, host=cfg.remote)
> +    ksft_eq(nc.stdout.strip(), "ping")
> +
> +    port = random.randrange(1024 + (1 << 15))
> +    with bkg(f"socat -t 2 -u TCP-LISTEN:{port} STDOUT", host=cfg.remote,
> +             exit_wait=True) as nc:
> +        wait_port_listen(port, host=cfg.remote)
> +
> +        cmd(f"echo ping | socat -t 2 -u STDIN TCP:{cfg.remote_baddr}:{port}", shell=True)
> +    ksft_eq(nc.stdout.strip(), "ping")
> +
> +