[PATCH v4 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 | 102 +++++++++++++++++-
 1 file changed, 101 insertions(+), 1 deletion(-)

diff --git a/dts/framework/remote_session/testpmd_shell.py b/dts/framework/remote_session/testpmd_shell.py
index 805bb3a77d..09f80cb250 100644
--- a/dts/framework/remote_session/testpmd_shell.py
+++ b/dts/framework/remote_session/testpmd_shell.py
@@ -20,7 +20,7 @@
 from enum import Enum, auto
 from functools import partial
 from pathlib import PurePath
-from typing import Callable, ClassVar
+from typing import Any, Callable, ClassVar
 
 from framework.exception import InteractiveCommandExecutionError
 from framework.settings import SETTINGS
@@ -82,6 +82,39 @@ class TestPmdForwardingModes(StrEnum):
     recycle_mbufs = auto()
 
 
+def stop_then_start_port_decorator(
+    func: Callable[["TestPmdShell", int, Any, bool], None]
+) -> Callable[["TestPmdShell", int, Any, bool], None]:
+    """Decorator that stops a port, runs decorated function, then starts the port.
+
+    The function being decorated must be a method defined in :class:`TestPmdShell` that takes a
+    port ID (as an int) as its first parameter and has a "verify" parameter (as a bool) as its last
+    parameter. The port ID and verify parameters will be passed into
+    :meth:`TestPmdShell._stop_port` so that the correct port is stopped/started and verification
+    takes place if desired.
+
+    Args:
+        func: The function to run while the port is stopped.
+
+    Returns:
+        Wrapper function that stops a port, runs the decorated function, then starts the port.
+    """
+
+    def wrapper(shell: "TestPmdShell", port_id: int, *args, **kwargs) -> None:
+        """Function that wraps the instance method of :class:`TestPmdShell`.
+
+        Args:
+            shell: Instance of the shell containing the method to decorate.
+            port_id: ID of the port to stop/start.
+        """
+        verify_value = kwargs["verify"] if "verify" in kwargs else args[-1]
+        shell._stop_port(port_id, verify_value)
+        func(shell, port_id, *args, **kwargs)
+        shell._start_port(port_id, verify_value)
+
+    return wrapper
+
+
 class TestPmdShell(SingleActiveInteractiveShell):
     """Testpmd interactive shell.
 
@@ -227,6 +260,73 @@ 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 with `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}.")
+
+    @stop_then_start_port_decorator
+    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 :data:`True`.
+
+        Raises:
+            InteractiveCommandExecutionError: If `verify` is :data:`True` and the MTU was not
+                properly updated on the port matching `port_id`.
+        """
+        set_mtu_output = self.send_command(f"port config mtu {port_id} {mtu}")
+        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.stop()
-- 
2.45.1