fix(links): reserve ports on add, accept port name and auto, add port_in_use code

gns3server/controller/controller_error.py

@@ -17,9 +17,14 @@
 
 
 class ControllerError(Exception):
-    def __init__(self, message: str):
+    def __init__(self, message: str, code: str | None = None):
         super().__init__()
         self._message = message
+        self._code = code
+
+    @property
+    def code(self):
+        return self._code
 
     def __repr__(self):
         return self._message

gns3server/controller/link.py

@@ -276,7 +276,7 @@ class Link:
         if port is None:
             raise ControllerNotFoundError(f"Port {adapter_number}/{port_number} for {node.name} not found")
         if port.link is not None:
-            raise ControllerError("Port is already used")
+            raise ControllerError("Port is already used", code="port_in_use")
 
         self._link_type = port.link_type
 
@@ -313,17 +313,29 @@ class Link:
             {"node": node, "adapter_number": adapter_number, "port_number": port_number, "port": port, "label": label}
         )
 
+        if not batch:
+            port.link = self
+
         if len(self._nodes) == 2 and not batch:
-            await self.create()
+            try:
+                await self.create()
+            except BaseException:
+                self.release_ports()
+                raise
             for n in self._nodes:
                 n["node"].add_link(self)
-                n["port"].link = self
             self._created = True
             self._project.emit_notification("link.created", self.asdict())
 
         if dump:
             self._project.dump()
 
+    def release_ports(self):
+        for n in self._nodes:
+            if n["port"].link == self:
+                n["port"].link = None
+            n["node"].links.discard(self)
+
     async def update_nodes(self, nodes):
         for node_data in nodes:
             node = self._project.get_node(node_data["node_id"])
@@ -352,11 +364,7 @@ class Link:
         """
         Delete the link
         """
-        for n in self._nodes:
-            # It could be different of self if we rollback an already existing link
-            if n["port"].link == self:
-                n["port"].link = None
-                n["node"].remove_link(self)
+        self.release_ports()
 
     async def reset(self):
         """

gns3server/controller/node.py

@@ -1142,6 +1142,27 @@ class Node:
                 return port
         return None
 
+    def get_port_by_name(self, name):
+        """
+        Return the port with this name or None if the port is not found
+        """
+        for port in self.ports:
+            if port.name == name:
+                return port
+        return None
+
+    def get_free_port(self, link_type=None):
+        """
+        Return the lowest free port, optionally restricted to a link type,
+        or None if there is no such port
+        """
+        free_ports = [
+            port for port in self.ports if port.link is None and (link_type is None or port.link_type == link_type)
+        ]
+        if not free_ports:
+            return None
+        return min(free_ports, key=lambda port: (port.adapter_number, port.port_number))
+
     def _list_ports(self):
         """
         Generate the list of port display in the client

gns3server/controller/ports/port.py

@@ -41,6 +41,10 @@ class Port:
     def link(self, val):
         self._link = val
 
+    @property
+    def name(self):
+        return self._name
+
     @property
     def adapter_number(self):
         return self._adapter_number