[PATCH v2 3/4] dts: add methods for modifying MTU to testpmd shell

[jspewock@iol.unh.edu]

From: Jeremy Spewock <jspewock@iol.unh.edu>

There are methods within DTS currently that support updating the MTU of
ports on a node, but the methods for doing this in a linux session rely
on the ip command and the port being bound to the kernel driver. Since
test suites are run while bound to the driver for DPDK, there needs to
be a way to modify the value while bound to said driver as well. This is
done by using testpmd to modify the MTU.

Signed-off-by: Jeremy Spewock <jspewock@iol.unh.edu>
---
 dts/framework/remote_session/testpmd_shell.py | 68 +++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/dts/framework/remote_session/testpmd_shell.py b/dts/framework/remote_session/testpmd_shell.py
index ca30aac264..3f425154dd 100644
--- a/dts/framework/remote_session/testpmd_shell.py
+++ b/dts/framework/remote_session/testpmd_shell.py
@@ -227,6 +227,74 @@ def set_forward_mode(self, mode: TestPmdForwardingModes, verify: bool = True):
                 f"Test pmd failed to set fwd mode to {mode.value}"
             )
 
+    def _stop_port(self, port_id: int, verify: bool = True) -> None:
+        """Stop port `port_id` in testpmd.
+
+        Depending on the PMD, the port may need to be stopped before configuration can take place.
+        This method wraps the command needed to properly stop ports and take their link down.
+
+        Args:
+            port_id: ID of the port to take down.
+            verify: If :data:`True` the output will be scanned in an attempt to verify that the
+                stopping of ports was successful. Defaults to True.
+
+        Raises:
+            InteractiveCommandExecutionError: If `verify` is :data:`True` and the port did not
+                successfully stop.
+        """
+        stop_port_output = self.send_command(f"port stop {port_id}")
+        if verify and ("Done" not in stop_port_output):
+            self._logger.debug(f"Failed to stop port {port_id}. Output was:\n{stop_port_output}")
+            raise InteractiveCommandExecutionError(f"Test pmd failed to stop port {port_id}.")
+
+    def _start_port(self, port_id: int, verify: bool = True) -> None:
+        """Start port `port_id` in testpmd.
+
+        Because the port may need to be stopped to make some configuration changes, it naturally
+        follows that it will need to be started again once those changes have been made.
+
+        Args:
+            port_id: ID of the port to start.
+            verify: If :data:`True` the output will be scanned in an attempt to verify that the
+                port came back up without error. Defaults to True.
+
+        Raises:
+            InteractiveCommandExecutionError: If `verify` is :data:`True` and the port did not come
+                back up.
+        """
+        start_port_output = self.send_command(f"port start {port_id}")
+        if verify and ("Done" not in start_port_output):
+            self._logger.debug(f"Failed to start port {port_id}. Output was:\n{start_port_output}")
+            raise InteractiveCommandExecutionError(f"Test pmd failed to start port {port_id}.")
+
+    def set_port_mtu(self, port_id: int, mtu: int, verify: bool = True) -> None:
+        """Change the MTU of a port using testpmd.
+
+        Some PMDs require that the port be stopped before changing the MTU, and it does no harm to
+        stop the port before configuring in cases where it isn't required, so we first stop ports,
+        then update the MTU, then start the ports again afterwards.
+
+        Args:
+            port_id: ID of the port to adjust the MTU on.
+            mtu: Desired value for the MTU to be set to.
+            verify: If `verify` is :data:`True` then the output will be scanned in an attempt to
+                verify that the mtu was properly set on the port. Defaults to True.
+
+        Raises:
+            InteractiveCommandExecutionError: If `verify` is :data:`True` and the MTU was not
+                properly updated on the port matching `port_id`.
+        """
+        self._stop_port(port_id, verify)
+        set_mtu_output = self.send_command(f"port config mtu {port_id} {mtu}")
+        self._start_port(port_id, verify)
+        if verify and (f"MTU: {mtu}" not in self.send_command(f"show port info {port_id}")):
+            self._logger.debug(
+                f"Failed to set mtu to {mtu} on port {port_id}." f" Output was:\n{set_mtu_output}"
+            )
+            raise InteractiveCommandExecutionError(
+                f"Test pmd failed to update mtu of port {port_id} to {mtu}"
+            )
+
     def _close(self) -> None:
         """Overrides :meth:`~.interactive_shell.close`."""
         self.send_command("quit", "Bye...")
-- 
2.45.1