One endpoint of the reverse co-driving tunnel.

The co-driving model from omnigent: a host dials OUT to a server over a single link (the server never dials in), and many logical channels are multiplexed over that one link. A teammate's browser "attaches" by opening a channel on the server endpoint; the frames tunnel down to the host endpoint, which spawns the channel's handler locally -- so the work runs on the owner's machine, and the owner's filesystem and credentials never leave it.

In the BEAM this is a GenServer holding the link plus a registry of channels. An endpoint is role: :server or role: :host. Only the host sets :on_open, the callback that materializes a local handler for each inbound channel.

The link

The endpoint is transport-agnostic. Outbound frames go through a send_fun (binary -> any); inbound bytes arrive as {:tunnel_recv, binary} messages. Raxol.Agent.Tunnel.Link.connect/2 wires two endpoints together in-process (deterministic, no network). A real WebSocket transport (e.g. Mint.WebSocket on the host, Bandit on the server) is a drop-in adapter: read the socket and send {:tunnel_recv, bytes} to the endpoint; set send_fun to write the socket.

Channels

• open_channel/3 (typically called on the server) allocates a channel_id, registers the caller (or :owner) as the local channel owner, and sends an :open frame. The peer's :on_open spawns its handler.
• send_data/3 sends channel I/O to the peer.
• close_channel/3 closes a channel on both ends.

A channel owner receives {:tunnel_data, channel_id, data} for inbound I/O and {:tunnel_closed, channel_id, reason} when the channel closes. Owners are monitored: if an owner dies, its channel is closed and the peer notified.