From: Yohei Kojima <yk@y-koj.net>

This patch adds a testcase to check if linking already-connected
netdevsim interfaces fails.

This patch also moves the testcase on invalid ifidx before linking
two netdevsims so that the test would fail if argument validation code
got broken: after linking two netdevsims, the test might not fail
because it attempts to link an already-connected netdevsim with
non-existing netdevsim.

Additionally, this patch adds comments for readability and details the
error message.

Signed-off-by: Yohei Kojima <yk@y-koj.net>
---
 .../selftests/drivers/net/netdevsim/peer.sh      | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/drivers/net/netdevsim/peer.sh b/tools/testing/selftests/drivers/net/netdevsim/peer.sh
index 7f32b5600925..338c844fe632 100755
--- a/tools/testing/selftests/drivers/net/netdevsim/peer.sh
+++ b/tools/testing/selftests/drivers/net/netdevsim/peer.sh
@@ -76,6 +76,7 @@ NSIM_DEV_2_FD=$((256 + RANDOM % 256))
 exec {NSIM_DEV_2_FD}</var/run/netns/nscl
 NSIM_DEV_2_IFIDX=$(ip netns exec nscl cat /sys/class/net/$NSIM_DEV_2_NAME/ifindex)
 
+# argument error checking
 echo "$NSIM_DEV_1_FD:$NSIM_DEV_1_IFIDX $NSIM_DEV_2_FD:2000" > $NSIM_DEV_SYS_LINK 2>/dev/null
 if [ $? -eq 0 ]; then
 	echo "linking with non-existent netdevsim should fail"
@@ -97,6 +98,14 @@ if [ $? -eq 0 ]; then
 	exit 1
 fi
 
+echo "$NSIM_DEV_1_FD:$NSIM_DEV_1_IFIDX $NSIM_DEV_2_FD:a" > $NSIM_DEV_SYS_LINK 2>/dev/null
+if [ $? -eq 0 ]; then
+	echo "linking with invalid ifidx should fail"
+	cleanup_ns
+	exit 1
+fi
+
+# link two netdevsim interfaces
 echo "$NSIM_DEV_1_FD:$NSIM_DEV_1_IFIDX $NSIM_DEV_2_FD:$NSIM_DEV_2_IFIDX" > $NSIM_DEV_SYS_LINK
 if [ $? -ne 0 ]; then
 	echo "linking netdevsim1 with netdevsim2 should succeed"
@@ -104,11 +113,10 @@ if [ $? -ne 0 ]; then
 	exit 1
 fi
 
-# argument error checking
-
-echo "$NSIM_DEV_1_FD:$NSIM_DEV_1_IFIDX $NSIM_DEV_2_FD:a" > $NSIM_DEV_SYS_LINK 2>/dev/null
+# semantic error checking
+echo "$NSIM_DEV_1_FD:$NSIM_DEV_1_IFIDX $NSIM_DEV_2_FD:$NSIM_DEV_2_IFIDX" > $NSIM_DEV_SYS_LINK 2>/dev/null
 if [ $? -eq 0 ]; then
-	echo "invalid arg should fail"
+	echo "linking already-connected netdevsim should fail"
 	cleanup_ns
 	exit 1
 fi
-- 
2.51.2