feat: allocate IOL Docker application IDs from a pool disjoint from IOU

IOL interface MACs derive from the application ID (aabb.cc{app}{iface}),
so ids must be unique across opened projects sharing computes — the same
reason IOU has its allocator. IOL Docker nodes draw from the upper half
(512-1022, netiomux's fixed peer is 1023) so the two node types can
neither collide nor starve each other; IOU behavior is unchanged.

The controller sniffs the same GNS3_IOL_RUNNER environment marker the
compute uses to select IOLDockerVM (both the nested-properties and
template/top-level-kwarg shapes), stores the id in node properties like
IOU does, and passes it through the Docker create payload. Without an
allocation the compute falls back to a stable node-derived id in the
same upper range.

gns3server/utils/application_id.py

@@ -13,6 +13,7 @@
 #
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
 
 from gns3server.controller.controller_error import ControllerError
 
@@ -20,13 +21,32 @@ import logging
 
 log = logging.getLogger(__name__)
 
+# IOU draws from the lower half: uBridge's iol_bridge uses application_id + 512
+# for its netio peer endpoint. IOL Docker nodes (iol-runner images) draw from
+# the upper half: their netiomux peer is the fixed id 1023. Both node types
+# derive interface MACs from the id (aabb.cc{app}{iface}), so the two pools
+# must stay disjoint — a shared id silently blackholes traffic between the
+# nodes as a MAC loop.
+IOU_APPLICATION_ID_POOL = range(1, 512)
+IOL_DOCKER_APPLICATION_ID_POOL = range(512, 1023)
 
-def get_next_application_id(projects, computes):
+
+def is_iol_runner_environment(environment) -> bool:
+    """
+    Whether a Docker node environment carries the GNS3_IOL_RUNNER marker —
+    the same signal the compute uses to select the IOLDockerVM class.
+    """
+
+    return "GNS3_IOL_RUNNER=" in (environment or "")
+
+
+def get_next_application_id(projects, computes, iol_docker=False):
     """
     Calculates free application_id from given nodes
 
     :param projects: all projects managed by controller
     :param computes: all computes used by the project
+    :param iol_docker: allocate for an IOL Docker (iol-runner) node instead of IOU
     :raises HTTPConflict when exceeds number
     :return: integer first free id
     """
@@ -38,12 +58,26 @@ def get_next_application_id(projects, computes):
         if project.status == "opened":
             nodes.extend(list(project.nodes.values()))
 
-    used = {n.properties["application_id"] for n in nodes if n.node_type == "iou" and n.compute.id in computes}
-    pool = set(range(1, 512))
+    if iol_docker:
+        used = {
+            n.properties["application_id"]
+            for n in nodes
+            if n.node_type == "docker"
+            and n.compute.id in computes
+            and "application_id" in n.properties
+            and is_iol_runner_environment(n.properties.get("environment"))
+        }
+        pool = set(IOL_DOCKER_APPLICATION_ID_POOL)
+        limit = "511 IOL Docker nodes"
+    else:
+        used = {n.properties["application_id"] for n in nodes if n.node_type == "iou" and n.compute.id in computes}
+        pool = set(IOU_APPLICATION_ID_POOL)
+        limit = "512 nodes"
     try:
         application_id = (pool - used).pop()
         return application_id
     except KeyError:
         raise ControllerError(
-            "Cannot create a new IOU node (limit of 512 nodes across all opened projects using the same computes)"
+            f"Cannot create a new {'IOL Docker' if iol_docker else 'IOU'} node "
+            f"(limit of {limit} across all opened projects using the same computes)"
         )