feat(interface): apply MTU for dpdk plugin ifaces

When changing MTU on a running VPP, the interface has to be down.

- Other plugins (rdma, avf, af_xdp) need vastly different logic,
  so support for them will be added later.
+ Mlx5-core does not need to set MTU on Linux interface.
+ MTU setting now does not happen at final setting path up,
  it happens in driver initialization layer instead
  E.g. AVF tests will not attempt to change MTU.
+ MTU edit removed from some non-hardware interfaces (including memif)
  e.g. bond interfaces. MTU on parent hw interface seems to be enough.
+ The non-jumbo MTU value used is 1800,
  so 1518B tests with additional encapsulation can still work.
+ When VPP MTU setting fails, the failure is now propagated.
  Previously, the failure was just logged and ignored,
  but now there is no reason to hide it.

Ticket: CSIT-1797

Change-Id: I3b853f1faf90001d544cbbb87b2affbb882ffba0
Signed-off-by: Vratko Polak <vrpolak@cisco.com>

1 files changed, 10 insertions, 14 deletions

diff --git a/resources/libraries/python/InterfaceUtil.py b/resources/libraries/python/InterfaceUtil.py
index 24a65e86a9..7e645d1f5f 100644
--- a/resources/libraries/python/InterfaceUtil.py
+++ b/resources/libraries/python/InterfaceUtil.py
@@ -347,32 +347,28 @@ class InterfaceUtil:
             exec_cmd_no_error(node, cmd, sudo=True)
 
     @staticmethod
-    def vpp_set_interface_mtu(node, interface, mtu=9200):
-        """Set Ethernet MTU on interface.
+    def vpp_set_interface_mtu(node, interface, mtu):
+        """Apply new MTU value to a VPP hardware interface.
+
+        The interface should be down when this is called.
 
         :param node: VPP node.
-        :param interface: Interface to setup MTU. Default: 9200.
+        :param interface: Interface to set MTU on.
         :param mtu: Ethernet MTU size in Bytes.
         :type node: dict
         :type interface: str or int
         :type mtu: int
+        :raises AsserionError: If VPP refused to change the MTU or set if state.
         """
         if isinstance(interface, str):
             sw_if_index = Topology.get_interface_sw_index(node, interface)
         else:
             sw_if_index = interface
-
         cmd = u"hw_interface_set_mtu"
         err_msg = f"Failed to set interface MTU on host {node[u'host']}"
-        args = dict(
-            sw_if_index=sw_if_index,
-            mtu=int(mtu)
-        )
-        try:
-            with PapiSocketExecutor(node) as papi_exec:
-                papi_exec.add(cmd, **args).get_reply(err_msg)
-        except AssertionError as err:
-            logger.debug(f"Setting MTU failed.\n{err}")
+        args = dict(sw_if_index=sw_if_index, mtu=int(mtu))
+        with PapiSocketExecutor(node) as papi_exec:
+            papi_exec.add(cmd, **args).get_reply(err_msg)
 
     @staticmethod
     def vpp_node_interfaces_ready_wait(node, retries=15):
@@ -1994,7 +1990,7 @@ class InterfaceUtil:
         thread_data = VPPUtil.vpp_show_threads(node)
         worker_cnt = len(thread_data) - 1
         if not worker_cnt:
-            return None
+            return
         worker_ids = list()
         if workers:
             for item in thread_data: