Check if the netdev list is empty and create veth pair to be used for
feature on/off testing.
Remove the veth pair after testing is complete.

Signed-off-by: Abhinav Jain <jain.abhinav177@gmail.com>
---
 tools/testing/selftests/net/netdevice.sh | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/tools/testing/selftests/net/netdevice.sh b/tools/testing/selftests/net/netdevice.sh
index e3afcb424710..279c44271047 100755
--- a/tools/testing/selftests/net/netdevice.sh
+++ b/tools/testing/selftests/net/netdevice.sh
@@ -129,6 +129,7 @@ kci_netdev_ethtool()
 
 	kci_netdev_ethtool_test 74 'dump' "ethtool -d $netdev"
 	kci_netdev_ethtool_test 94 'stats' "ethtool -S $netdev"
+
 	return 0
 }
 
@@ -196,10 +197,27 @@ if [ ! -e "$TMP_LIST_NETDEV" ];then
 fi
 
 ip link show |grep '^[0-9]' | grep -oE '[[:space:]].*eth[0-9]*:|[[:space:]].*enp[0-9]s[0-9]:' | cut -d\  -f2 | cut -d: -f1> "$TMP_LIST_NETDEV"
+
+veth_created=0
+
+if [ ! -s "$TMP_LIST_NETDEV" ]; then
+	echo "No valid network device found, creating veth pair"
+	ip link add veth0 type peer name veth1
+	echo "veth0" > "$TMP_LIST_NETDEV"
+	echo "veth1" >> "$TMP_LIST_NETDEV"
+	veth_created=1
+fi
+
 while read netdev
 do
 	kci_test_netdev "$netdev"
 done < "$TMP_LIST_NETDEV"
 
+#clean up veth interface pair if it was created
+if [ "veth_created" ]; then
+	ip link delete veth0
+	echo "Removed veth pair"
+fi
+
 rm "$TMP_LIST_NETDEV"
 exit 0
-- 
2.34.1

On Wed,  7 Aug 2024 17:57:16 +0000 Abhinav Jain wrote:
> +	ip link add veth0 type peer name veth1

That's not the right syntax..
-- 
pw-bot: cr

On Wed, 7 Aug 2024 18:28:34 -0700 Jakub Kicinski wrote:
> That's not the right syntax..

Thanks for the feedback Jakub. I have rectified this and while at it,
I tested using vng on a network based kernel and found another issue in
veth removal logic. I have fixed that as well.

Please kindly check the v5 series here:
https://lore.kernel.org/all/20240808122452.25683-1-jain.abhinav177@gmail.com/
---

On Thu,  8 Aug 2024 12:28:47 +0000 Abhinav Jain wrote:
> On Wed, 7 Aug 2024 18:28:34 -0700 Jakub Kicinski wrote:
> > That's not the right syntax..  
> 
> Thanks for the feedback Jakub. I have rectified this and while at it,
> I tested using vng on a network based kernel and found another issue in
> veth removal logic. I have fixed that as well.
> 
> Please kindly check the v5 series here

I'll take a look, but please try to follow the guidance in our process
doc: https://www.kernel.org/doc/html/next/process/maintainer-netdev.html