perf: parallelize UDP port allocation and NIO creation in UDPLink.create

Previously the two sides' UDP port reservations and NIO tunnel
POSTs were issued sequentially, even though they are independent
once the peer addresses are known — each node talks to its own
compute/uBridge with no shared lock, so the HTTP round-trips can
overlap.

- Port allocation: gather _allocate_port for both computes
- NIO creation: gather both node.post calls together
- Error handling: if either side fails, roll back whichever side
  succeeded (previously only node2-fails→cleanup-node1) before
  re-raising the first error

Batch loading (open/import project) benefits most because links
are created at high concurrency and the per-link wall-clock
time is dominated by the sum of its two sequential NIO POSTs.

gns3server/controller/udp_link.py

@@ -16,6 +16,8 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 
+import asyncio
+
 from .controller_error import ControllerError, ControllerNotFoundError
 from .link import Link, _UNSET
 from .node_types import BUILTIN_NODE_TYPES
@@ -99,25 +101,25 @@ class UDPLink(Link):
         except ValueError as e:
             raise ControllerError(f"Cannot get an IP address on same subnet: {e}")
 
-        # Reserve a UDP port on both side
-        # Try pre-allocated ports first (used during batch project loading)
-        port = self._project.pop_preallocated_udp_port(node1.compute.id)
-        if port is not None:
-            self._node1_port = port
-        else:
-            response = await node1.compute.post(f"/projects/{self._project.id}/ports/udp")
-            self._node1_port = response.json["udp_port"]
-        port = self._project.pop_preallocated_udp_port(node2.compute.id)
-        if port is not None:
-            self._node2_port = port
-        else:
-            response = await node2.compute.post(f"/projects/{self._project.id}/ports/udp")
-            self._node2_port = response.json["udp_port"]
+        # Reserve a UDP port on both sides in parallel. Pre-allocated ports
+        # (used during batch project loading) are popped from memory; otherwise
+        # each side falls back to a single HTTP round-trip to its compute.
+        async def _allocate_port(compute):
+            port = self._project.pop_preallocated_udp_port(compute.id)
+            if port is not None:
+                return port
+            response = await compute.post(f"/projects/{self._project.id}/ports/udp")
+            return response.json["udp_port"]
+
+        self._node1_port, self._node2_port = await asyncio.gather(
+            _allocate_port(node1.compute), _allocate_port(node2.compute)
+        )
 
         node1_filters, node2_filters = self._get_node_filters(node1, node2)
         node1_markers, node2_markers = self._get_node_markers(node1, node2)
 
-        # Create the tunnel on both side
+        # Build the tunnel specs for both sides. Index 0 is always node1 so
+        # that update()/delete() keep addressing self._link_data[0]/[1].
         self._link_data.append(
             {
                 "lport": self._node1_port,
@@ -129,8 +131,6 @@ class UDPLink(Link):
                 "suspend": self._suspended,
             }
         )
-        await node1.post(f"/adapters/{adapter_number1}/ports/{port_number1}/nio", data=self._link_data[0], timeout=120)
-
         self._link_data.append(
             {
                 "lport": self._node2_port,
@@ -142,14 +142,35 @@ class UDPLink(Link):
                 "suspend": self._suspended,
             }
         )
-        try:
-            await node2.post(
+
+        # Create the NIO tunnel on both sides in parallel. The two ends are
+        # independent once the ports and peer addresses are known -- each node
+        # talks to its own compute/uBridge with no shared lock between them --
+        # so the two POSTs overlap. If either fails, roll back whichever side
+        # succeeded before re-raising the first error.
+        results = await asyncio.gather(
+            node1.post(
+                f"/adapters/{adapter_number1}/ports/{port_number1}/nio", data=self._link_data[0], timeout=120
+            ),
+            node2.post(
                 f"/adapters/{adapter_number2}/ports/{port_number2}/nio", data=self._link_data[1], timeout=120
-            )
-        except Exception as e:
-            # We clean the first NIO
-            await node1.delete(f"/adapters/{adapter_number1}/ports/{port_number1}/nio", timeout=120)
-            raise e
+            ),
+            return_exceptions=True,
+        )
+        errors = [result for result in results if isinstance(result, Exception)]
+        if errors:
+            cleanup = []
+            if not isinstance(results[0], Exception):
+                cleanup.append(
+                    node1.delete(f"/adapters/{adapter_number1}/ports/{port_number1}/nio", timeout=120)
+                )
+            if not isinstance(results[1], Exception):
+                cleanup.append(
+                    node2.delete(f"/adapters/{adapter_number2}/ports/{port_number2}/nio", timeout=120)
+                )
+            if cleanup:
+                await asyncio.gather(*cleanup, return_exceptions=True)
+            raise errors[0]
         self._created = True
         # New links automatically inherit every active project-level marker
         # definition so the user doesn't have to reconfigure.