Fix: make maximum node_id configurable (default: 250) (#2604)

Fixes #2603

Author: ipspace

docs/nodes.md

@@ -183,7 +183,7 @@ After the initial cleanup, the *netlab* [topology transformation code](dev/trans
 * Device interfaces created as needed during the link transformation phase and collected in the **interfaces** list.
 * [](modules.md) document describes further processing done on configuration module parameters.
 
-[^id]: Node **id** must be an integer between 1 and 250. When using the standard management interface IP addressing (where management IPv4 addresses start with .100), the node **id** should not exceed 150.
+[^id]: Node **id** must be an integer between 1 and MAX_NODE_ID (default: 250). You can change the maximum node ID with the **const.MAX_NODE_ID** [system default](topo-defaults). When using the standard management interface IP addressing (where management IPv4 addresses start with .100), the node **id** should not exceed 150.
 
 [^HOST]: Identified by **role: host** attribute
 

netsim/augment/nodes.py

@@ -20,7 +20,7 @@
 from ..data import global_vars,is_true_int
 from ..modules._dataplane import extend_id_set,is_id_used,set_id_counter,get_next_id
 
-MAX_NODE_ID: typing.Final[int] = 250
+MAX_NODE_ID: int
 
 """
 Reserve a node ID, for example for gateway ID, return True if successful, False if duplicate
@@ -38,6 +38,9 @@ def reserve_id(n_id: int) -> bool:
 """
 
 def create_node_dict(nodes: Box) -> Box:
+  global MAX_NODE_ID                                        # Max node ID has to be initialized early in the transformation
+  MAX_NODE_ID = global_vars.get_const('MAX_NODE_ID',250)
+
   if isinstance(nodes,dict):
     node_dict = nodes
   else:
@@ -469,6 +472,7 @@ def augment_node_device_data(n: Box, topology: Box) -> None:
 * set management IP and MAC addresses
 '''
 def transform(topology: Box, defaults: Box, pools: Box) -> None:
+  global MAX_NODE_ID
   for name,n in topology.nodes.items():
     if not must_be_int(n,'id',f'nodes.{name}',module='nodes',min_value=1,max_value=MAX_NODE_ID):
       continue

tests/errors/node-max-id.log

@@ -0,0 +1 @@
+Fatal error in dataplane: Ran out of node_id values, next value would be greater than 4

tests/errors/node-max-id.yml

@@ -0,0 +1,12 @@
+---
+defaults.const.MAX_NODE_ID: 4
+defaults.device: none
+
+nodes:
+  a:
+    id: 3
+  b:
+  c:
+  d:
+    id: 2
+  e: