netdev - Re: [PATCH net] selftests: openvswitch: Use bash as interpreter

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Date: Mon, 17 Jun 2024 12:05:11 +0200
From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
To: Simon Horman <horms@...nel.org>
CC: Aaron Conole <aconole@...hat.com>, Adrian Moreno <amorenoz@...hat.com>,
	Pravin B Shelar <pshelar@....org>, Shuah Khan <shuah@...nel.org>,
	<netdev@...r.kernel.org>, <dev@...nvswitch.org>,
	<linux-kselftest@...r.kernel.org>, "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, "Paolo
 Abeni" <pabeni@...hat.com>
Subject: Re: [PATCH net] selftests: openvswitch: Use bash as interpreter

On 6/17/24 10:28, Simon Horman wrote:
> openvswitch.sh makes use of substitutions of the form ${ns:0:1}, to
> obtain the first character of $ns. Empirically, this is works with bash
> but not dash. When run with dash these evaluate to an empty string and
> printing an error to stdout.
> 
>   # dash -c 'ns=client; echo "${ns:0:1}"' 2>error
>   # cat error
>   dash: 1: Bad substitution
>   # bash -c 'ns=client; echo "${ns:0:1}"' 2>error
>   c
>   # cat error
> 
> This leads to tests that neither pass nor fail.
> F.e.
> 
>   TEST: arp_ping                                                      [START]
>   adding sandbox 'test_arp_ping'
>   Adding DP/Bridge IF: sbx:test_arp_ping dp:arpping {, , }
>   create namespaces
>   ./openvswitch.sh: 282: eval: Bad substitution
>   TEST: ct_connect_v4                                                 [START]
>   adding sandbox 'test_ct_connect_v4'
>   Adding DP/Bridge IF: sbx:test_ct_connect_v4 dp:ct4 {, , }
>   ./openvswitch.sh: 322: eval: Bad substitution
>   create namespaces
> 
> Resolve this by making openvswitch.sh a bash script.
> 
> Fixes: 918423fda910 ("selftests: openvswitch: add an initial flow programming case")
> Signed-off-by: Simon Horman <horms@...nel.org>

That's good fix,
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@...el.com>

sidenote: I like very much the idea to use the least powerful tool, like
sh vs bash, awk vs gawk, but it breaks when we forget what is outside of
the scope of the former/standard.
Perhaps for shell, we could convert all the selftests at once?

> ---
>   tools/testing/selftests/net/openvswitch/openvswitch.sh | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/net/openvswitch/openvswitch.sh b/tools/testing/selftests/net/openvswitch/openvswitch.sh
> index 5cae53543849..15bca0708717 100755
> --- a/tools/testing/selftests/net/openvswitch/openvswitch.sh
> +++ b/tools/testing/selftests/net/openvswitch/openvswitch.sh
> @@ -1,4 +1,4 @@
> -#!/bin/sh
> +#!/bin/bash
>   # SPDX-License-Identifier: GPL-2.0
>   #
>   # OVS kernel module self tests
> 
>