linux-kernel - [PATCH] tools/testing/selftests/bpf/test_tc_tunnel.sh: Prevent client connect before server bind

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Date: Thu, 29 Feb 2024 14:00:00 +0000
From: "Alessandro Carminati (Red Hat)" <alessandro.carminati@...il.com>
To: Andrii Nakryiko <andrii@...nel.org>,
	Shuah Khan <shuah@...nel.org>
Cc: Mykola Lysenko <mykolal@...com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...gle.com>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Alessandro Carminati <alessandro.carminati@...il.com>,
	bpf@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] tools/testing/selftests/bpf/test_tc_tunnel.sh: Prevent client connect before server bind

In some systems, the netcat server can incur in delay to start listening.
When this happens, the test can randomly fail in various points.
This is an example error message:
   # ip gre none gso
   # encap 192.168.1.1 to 192.168.1.2, type gre, mac none len 2000
   # test basic connectivity
   # Ncat: Connection refused.

Signed-off-by: Alessandro Carminati (Red Hat) <alessandro.carminati@...il.com>
---
 tools/testing/selftests/bpf/test_tc_tunnel.sh | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/test_tc_tunnel.sh b/tools/testing/selftests/bpf/test_tc_tunnel.sh
index 910044f08908..01c0f4b1a8c2 100755
--- a/tools/testing/selftests/bpf/test_tc_tunnel.sh
+++ b/tools/testing/selftests/bpf/test_tc_tunnel.sh
@@ -72,7 +72,6 @@ cleanup() {
 server_listen() {
 	ip netns exec "${ns2}" nc "${netcat_opt}" -l "${port}" > "${outfile}" &
 	server_pid=$!
-	sleep 0.2
 }
 
 client_connect() {
@@ -93,6 +92,22 @@ verify_data() {
 	fi
 }
 
+wait_for_port() {
+	local digits=8
+	local port2check=$(printf ":%04X" $1)
+	local prot=$([ "$2" == "-6" ] && echo 6 && digits=32)
+
+	for i in $(seq 20); do
+		if ip netns exec "${ns2}" cat /proc/net/tcp${prot} | \
+			sed -r 's/^[ \t]+[0-9]+: ([0-9A-F]{'${digits}'}:[0-9A-F]{4}) .*$/\1/' | \
+			grep -q "${port2check}"; then
+			return 0
+		fi
+		sleep 0.1
+	done
+	return 1
+}
+
 set -e
 
 # no arguments: automated test, run all
@@ -193,6 +208,7 @@ setup
 # basic communication works
 echo "test basic connectivity"
 server_listen
+wait_for_port ${port} ${netcat_opt}
 client_connect
 verify_data
 
@@ -204,6 +220,7 @@ ip netns exec "${ns1}" tc filter add dev veth1 egress \
 	section "encap_${tuntype}_${mac}"
 echo "test bpf encap without decap (expect failure)"
 server_listen
+wait_for_port ${port} ${netcat_opt}
 ! client_connect
 
 if [[ "$tuntype" =~ "udp" ]]; then
-- 
2.34.1