Subject: Re: [PATCH net-next 02/12] selftests/vsock: make wait_for_listener() work even if pipefail is on

From: Simon Horman <[email-masked]>
Date: Mon, 27 Oct 2025 16:48:28 +0000

On Wed, Oct 22, 2025 at 06:00:06PM -0700, Bobby Eshleman wrote:
> From: Bobby Eshleman <[email-masked]>
> 
> Save/restore pipefail to not mistakenly trip the if-condition
> in wait_for_listener().
> 
> awk doesn't gracefully handle SIGPIPE with a non-zero exit code, so grep
> exiting upon finding a match causes false-positives when the pipefail
> option is used. This will enable pipefail usage, so that we can losing
> failures when piping test output into log() functions.
> 
> Fixes: a4a65c6fe08b ("selftests/vsock: add initial vmtest.sh for vsock")
> Signed-off-by: Bobby Eshleman <[email-masked]>
> ---
>  tools/testing/selftests/vsock/vmtest.sh | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/tools/testing/selftests/vsock/vmtest.sh b/tools/testing/selftests/vsock/vmtest.sh
> index 561600814bef..ec3ff443f49a 100755
> --- a/tools/testing/selftests/vsock/vmtest.sh
> +++ b/tools/testing/selftests/vsock/vmtest.sh
> @@ -243,6 +243,7 @@ wait_for_listener()
>  	local port=$1
>  	local interval=$2
>  	local max_intervals=$3
> +	local old_pipefail
>  	local protocol=tcp
>  	local pattern
>  	local i
> @@ -251,6 +252,13 @@ wait_for_listener()
>  
>  	# for tcp protocol additionally check the socket state
>  	[ "${protocol}" = "tcp" ] && pattern="${pattern}0A"
> +
> +	# 'grep -q' exits on match, sending SIGPIPE to 'awk', which exits with
> +	# an error, causing the if-condition to fail when pipefail is set.
> +	# Instead, temporarily disable pipefail and restore it later.
> +	old_pipefail=$(set -o | awk '/^pipefail[[:space:]]+(on|off)$/{print $2}')
> +	set +o pipefail
> +
>  	for i in $(seq "${max_intervals}"); do
>  		if awk '{print $2" "$4}' /proc/net/"${protocol}"* | \
>  		   grep -q "${pattern}"; then

Hi Bobby,

I agree this is a problem. But I'm wondering if you considered
moving the pattern matching into the awk script. I'm no awk expert.
But suspect that would lead to a more elegant solution.

> @@ -258,6 +266,10 @@ wait_for_listener()
>  		fi
>  		sleep "${interval}"
>  	done
> +
> +	if [[ "${old_pipefail}" == on ]]; then
> +		set -o pipefail
> +	fi
>  }
>  
>  vm_wait_for_listener() {
> 
> -- 
> 2.47.3
> 
>