feat(controller): offer Dynamips the kernel datapath

A Dynamips Ethernet port can anchor a kernel link whenever its compute's
uBridge has the tap module — the anchors are uBridge-created TAPs the
hypervisor merely opens, the same capability QEMU gates on, so no
Dynamips-specific capability is needed. Serial, ATM and POS ports are
excluded per port by the existing link-type check (the controller's port
matrix decides), keeping them on the relay whatever the capabilities.

Eligibility tests cover the mixed pairs (docker/qemu/iou endpoints on the
same compute), the strict tap-capability requirement, and the serial
exclusion.

gns3server/controller/udp_link.py

@@ -182,9 +182,12 @@ class UDPLink(Link):
         datapath and cannot carry a kernel link at all. IOU's Ethernet
         bays anchor on persistent TAPs too, bound to its IOL fabric
         (``iol_bridge add_nio_tap``) — a separate capability, since it can
-        be present or absent independently of the tap module. A kernel link
+        be present or absent independently of the tap module. Dynamips
-        is an Ethernet segment, so non-Ethernet ports (IOU serial) stay on
+        Ethernet slot ports anchor on persistent TAPs the hypervisor opens
-        the relay whatever the node's capabilities.
+        (the tap module again — the Dynamips binary itself creates nothing),
+        so it gates like QEMU. A kernel link is an Ethernet segment, so
+        non-Ethernet ports (IOU serial, Dynamips serial/ATM/POS adapters)
+        stay on the relay whatever the node's capabilities.
         """
 
         if not Config.instance().settings.Server.enable_kernel_datapath:
@@ -214,6 +217,11 @@ class UDPLink(Link):
             return capabilities.get("ubridge_tap") is True
         if node.node_type == "iou":
             return capabilities.get("ubridge_iol_tap") is True
+        if node.node_type == "dynamips":
+            # The anchors are uBridge-created TAPs the Dynamips hypervisor
+            # merely opens (nio create_tap) — the same tap-module capability
+            # QEMU needs, not a Dynamips-specific one.
+            return capabilities.get("ubridge_tap") is True
         return False
 
     async def _prepare(self):

tests/controller/test_kernel_datapath_link.py

@@ -169,6 +169,70 @@ async def test_iou_eligibility_is_its_own_capability(project):
     assert link._kernel_datapath_eligible(node1, node2) is False
 
 
+@pytest.mark.asyncio
+async def test_kernel_datapath_eligible_for_dynamips_with_tap_support(project):
+    """
+    Dynamips Ethernet slot ports anchor on persistent TAPs the hypervisor
+    opens (nio create_tap on a uBridge-created device), so they gate on the
+    tap module like QEMU — no Dynamips-specific capability — and mix with
+    docker/qemu/iou endpoints on the same compute.
+    """
+
+    compute = MagicMock()
+    compute.id = "compute-1"
+    compute.capabilities = {"ubridge_tap": True, "ubridge_iol_tap": True}
+    node1 = _node(project, compute, "r1", node_type="dynamips")
+    node2 = _node(project, compute, "r2", node_type="dynamips")
+    link = await _link(project, node1, node2)
+    assert link._kernel_datapath_eligible(node1, node2) is True
+
+    for peer in (
+        _node(project, compute, "docker1"),
+        _node(project, compute, "qemu1", node_type="qemu"),
+        _node(project, compute, "iou1", node_type="iou"),
+    ):
+        link = await _link(project, node1, peer)
+        assert link._kernel_datapath_eligible(node1, peer) is True
+
+
+@pytest.mark.asyncio
+async def test_dynamips_eligibility_follows_the_tap_capability(project):
+    """
+    A compute whose uBridge cannot create persistent TAPs keeps Dynamips on
+    the relay (the hypervisor would have nothing to open), and so does an
+    unreported/failed probe.
+    """
+
+    node2 = _node(project, _tap_capable_compute(), "docker1")
+    for tap_support in (None, False):
+        compute = _tap_capable_compute(tap_support=tap_support)
+        node1 = _node(project, compute, "r1", node_type="dynamips")
+        link = await _link(project, node1, node2)
+        assert link._kernel_datapath_eligible(node1, node2) is False
+
+
+@pytest.mark.asyncio
+async def test_kernel_datapath_not_eligible_for_dynamips_serial_ports(project):
+    """
+    A Dynamips serial port (NM-4T, WIC-2T, ...) stays on the relay whatever
+    the compute's capabilities — the same per-port exclusion as IOU serial,
+    decided by the controller's port matrix.
+    """
+
+    from gns3server.controller.ports.serial_port import SerialPort
+
+    compute = MagicMock()
+    compute.id = "compute-1"
+    compute.capabilities = {"ubridge_tap": True}
+
+    node1 = _node(project, compute, "r1", node_type="dynamips")
+    node1._ports = [SerialPort("Serial0/0", 0, 0, 0)]
+    node2 = _node(project, compute, "r2", node_type="dynamips")
+    node2._ports = [SerialPort("Serial0/0", 0, 0, 0)]
+    link = await _link(project, node1, node2)
+    assert link._kernel_datapath_eligible(node1, node2) is False
+
+
 @pytest.mark.asyncio
 async def test_kernel_datapath_not_eligible_for_serial_ports(project):
     """