1. routing.py
   • Purpose: Registry of mesh routing protocols. Exactly one is active per scenario, selected with [Routing] protocol = 'olsrd' | 'babel' | 'none' in config.toml (none = netem shaping only, no daemon).
   • Usage:
     • get_protocol(name) returns the RoutingProtocol entry, None for 'none', and raises on unknown names so config errors surface at load time.
     • Each RoutingProtocol declares its firewall binary, dedicated chain (VSNES_OLSR, VSNES_BABEL), how out-of-LOS peers are dropped (src_ip for OLSR, src_mac for babel’s IPv6 link-local hellos), the gated UDP port (698 / 6696), and the routing-ctl start/stop commands.
     • Its methods build the shell lines that set up/tear down the chain, add/remove per-peer DROP rules, and start/stop the daemon; Channel.py batches them into one docker exec per node.
     • To add a protocol, add one entry to PROTOCOLS (plus routing-ctl support in the node image) — see the module docstring, “Adding a routing protocol”.
   • Related Files:
     • Used by Scenario.py (validates the protocol at load) and Channel.py (applies the gating and manages the daemon lifecycle).