[RFC] dts: add MTU update testsuite

diff --git a/dts/framework/config/conf_yaml_schema.json b/dts/framework/config/conf_yaml_schema.json
index f02a310bb5..b60fed1442 100644
--- a/dts/framework/config/conf_yaml_schema.json
+++ b/dts/framework/config/conf_yaml_schema.json
@@ -187,7 +187,8 @@ 
       "enum": [
         "hello_world",
         "os_udp",
-        "pmd_buffer_scatter"
+        "pmd_buffer_scatter",
+        "mtu_update"
       ]
     },
     "test_target": {
diff --git a/dts/tests/TestSuite_mtu_update.py b/dts/tests/TestSuite_mtu_update.py
new file mode 100644
index 0000000000..7b6ea2a9dc
--- /dev/null
+++ b/dts/tests/TestSuite_mtu_update.py
@@ -0,0 +1,154 @@ 
+# SPDX-License-Identifier: BSD-3-Clause
+# Copyright(c) 2024 Arm Limited
+
+"""The DPDK MTU update app test suite.
+
+The MTU is how many bytes an ethernet frame can contain.
+This suite tests updating the MTU and verifies that the NIC accepts packets smaller than
+the or equal to new MTU and rejects packets larger.
+"""
+
+from scapy.layers.inet import IP  # type: ignore[import-untyped]
+from scapy.layers.l2 import Ether  # type: ignore[import-untyped]
+from scapy.packet import Raw  # type: ignore[import-untyped]
+
+from framework.remote_session.testpmd_shell import TestPmdShell
+from framework.test_suite import TestSuite
+
+IP_HEADER_LEN = 20  # IP overhead length
+STANDARD_MTU = 1500  # Default MTU size
+JUMBO_FRAME_MTU = 9000  # Jumbo MTU size
+VLAN_PADDING = 5  # Manufacturer overhead to account for VLAN size
+
+
+class TestMtuUpdate(TestSuite):
+    """DPDK MTU update test suite."""
+
+    def set_up_suite(self) -> None:
+        """Set up the test suite.
+
+        Teardown:
+            Set the MTU on the TG higher than any test will use, so it will not fragment packets.
+        """
+        self.tg_node.main_session.configure_port_mtu(JUMBO_FRAME_MTU + 200, self._tg_port_egress)
+        self.tg_node.main_session.configure_port_mtu(JUMBO_FRAME_MTU + 200, self._tg_port_ingress)
+
+    def send_packet_and_verify(self, ether_frame_size: int, should_receive: bool) -> None:
+        """Generate, send, and capture packets to verify that the sent packet was received or not.
+
+        Calculate the payload size by subtracting the IP header size from frame size.
+        Then, craft a packet with the payload being X's and the 4-byte CRC being replaced by "FCRC".
+        The packet is then sent.
+        If the packet is expected to be received, verify the full payload is within the received
+        packets.
+        If the packet is not expected to be received, verify the full payload is not within the
+        received packets.
+
+        Args:
+            ether_frame_size: Ethernet frame size of the packet to be generated and sent.
+            should_receive: Whether the test case expects to receive the packet or not.
+        """
+        # Calculate appropriate payload size.
+        payload = ether_frame_size - IP_HEADER_LEN
+
+        # Insert fake CRC('FCRC') at the end of the packet to account for CRC length.
+        packet = Ether() / IP(len=ether_frame_size) / Raw(load="X" * payload) / Raw("FCRC")
+
+        # Sends packet and checks if it was received.
+        received_packets = self.send_packet_and_capture(packet)
+
+        found = any(
+            ("X" * payload) in str(packets.load)
+            for packets in received_packets
+            if hasattr(packets, "load")
+        )
+
+        # Verify if the packet was received when it should have been, and vice versa.
+        if should_receive:
+            self.verify(
+                found,
+                f"Did not receive packet smaller than or equal to the MTU: {ether_frame_size}.",
+            )
+        else:
+            self.verify(not found, f"Received a packet larger than the MTU: {ether_frame_size}.")
+
+    def set_and_check_mtu(self, new_mtu: int) -> None:
+        """Sets the new MTU and verifies packets smaller than or equal to it will be
+            received and packets larger will not.
+
+        First, start testpmd and update the MTU. Then ensure the new value appears
+        on port info for all ports.
+        Next, start packet capturing and send 3 different lengths of packet and verify
+        they are handled correctly.
+            # 1. VLAN_PADDING units smaller than the MTU specified.
+            # 2. Equal to the MTU specified.
+            # 3. VLAN_PADDING units larger than the MTU specified (should be fragmented).
+        Finally, stop packet capturing.
+
+        Args:
+            new_mtu: New Maximum Transmission Unit to be tested.
+        """
+        with TestPmdShell(
+            self.sut_node,
+            tx_offloads=0x8000,
+            mbuf_size=[9200],
+            max_pkt_len=9200,
+            enable_scatter=True,
+        ) as testpmd:
+            # Configure the new MTU.
+            testpmd.set_port_mtu_all(new_mtu)
+
+            # Start packet capturing.
+            testpmd.start()
+
+            # Send 3 packets of different sizes (accounting for the size of VLAN).
+            # 1. VLAN_PADDING units smaller than the MTU specified.
+            # 2. Equal to the MTU specified.
+            # 3. VLAN_PADDING units larger than the MTU specified (should be fragmented).
+            smaller_frame_size: int = new_mtu - VLAN_PADDING
+            equal_frame_size: int = new_mtu
+            larger_frame_size: int = new_mtu + VLAN_PADDING
+            self.send_packet_and_verify(ether_frame_size=smaller_frame_size, should_receive=True)
+            self.send_packet_and_verify(ether_frame_size=equal_frame_size, should_receive=True)
+            self.send_packet_and_verify(ether_frame_size=larger_frame_size, should_receive=False)
+
+    def test_mtu_1500(self) -> None:
+        """Verify MTU of size 1500.
+
+        Test:
+            Set and check MTU of size 1500.
+        """
+        self.set_and_check_mtu(1500)
+
+    def test_mtu_2400(self) -> None:
+        """Verify MTU of size 2400.
+
+        Test:
+            Set and check MTU of size 2400.
+        """
+        self.set_and_check_mtu(2400)
+
+    def test_mtu_4800(self) -> None:
+        """Verify MTU of size 4800.
+
+        Test:
+            Set and check MTU of size 4800.
+        """
+        self.set_and_check_mtu(4800)
+
+    def test_mtu_9000(self) -> None:
+        """Verify MTU of size 9000.
+
+        Test:
+            Set and check MTU of size 9000.
+        """
+        self.set_and_check_mtu(9000)
+
+    def tear_down_suite(self) -> None:
+        """Tear down the test suite.
+
+        Teardown:
+            Set the MTU on the TG back to the standard 1500.
+        """
+        self.tg_node.main_session.configure_port_mtu(STANDARD_MTU, self._tg_port_egress)
+        self.tg_node.main_session.configure_port_mtu(STANDARD_MTU, self._tg_port_ingress)