Add selftest case for testing the speed and duplex state of
local NIC driver and the partner based on the supported
link modes obtained from the ethtool. Speed and duplex states
are varied and verified using ethtool.

Signed-off-by: Mohan Prasad J <mohan.prasad@microchip.com>
---
 .../drivers/net/hw/nic_link_layer.py          | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/tools/testing/selftests/drivers/net/hw/nic_link_layer.py b/tools/testing/selftests/drivers/net/hw/nic_link_layer.py
index fb046efbe..4548da3d9 100644
--- a/tools/testing/selftests/drivers/net/hw/nic_link_layer.py
+++ b/tools/testing/selftests/drivers/net/hw/nic_link_layer.py
@@ -73,6 +73,27 @@ def test_autonegotiation(cfg, link_config) -> None:
         time.sleep(time_delay)
         verify_autonegotiation(cfg, state, link_config)
 
+def test_network_speed(cfg, link_config) -> None:
+    common_link_modes = link_config.common_link_modes
+    if not common_link_modes:
+        KsftSkipEx("No common link modes exist")
+    speeds, duplex_modes = link_config.get_speed_duplex_values(common_link_modes)
+
+    if speeds and duplex_modes and len(speeds) == len(duplex_modes):
+        for idx in range(len(speeds)):
+            speed = speeds[idx]
+            duplex = duplex_modes[idx]
+            if link_config.set_speed_and_duplex(speed, duplex) == False:
+                raise KsftFailEx(f"Unable to set speed and duplex parameters for {cfg.ifname}")
+            time.sleep(time_delay)
+            if link_config.verify_speed_and_duplex(speed, duplex) == False:
+                raise KsftSkipEx(f"Unable to verify speed and duplex states for interface {cfg.ifname}")
+    else:
+        if not speeds or not duplex_modes:
+            KsftSkipEx(f"No supported speeds or duplex modes found for interface {cfg.ifname}")
+        else:
+            KsftSkipEx("Mismatch in the number of speeds and duplex modes")
+
 def main() -> None:
     with NetDrvEpEnv(__file__, nsim_test=False) as cfg:
         link_config = LinkConfig(cfg)
-- 
2.43.0