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

[Bobby Eshleman <bobbyeshleman@gmail.com>]

From: Bobby Eshleman <bobbyeshleman@meta.com>

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

-- 
2.47.3