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> This documentation is organized by AI with reference to actual code. AI can make mistakes — please verify against the source code when in doubt.


# IOL Images with iol-runner (Cisco CML containerized IOL) as Docker Nodes

## Overview

IOL images packaged with Cisco CML's container runner — for example
`iol-xe/iol-xe:17-18-02` (IOS-XE 17.18.02 IOL in a scratch image driven by
`iol-runner`, module `virl.lab/cmd/iol-runner`) — run as first-class GNS3
Docker router nodes with **zero changes to the image**. The integration adds
two generic server mechanisms:

1. **Unix-socket NIO** (`GNS3_UNIX_SOCKET_NIO=1`, on `VendorDockerVM`): link
   adapters through per-interface AF_UNIX datagram sockets instead of a TAP
   interface moved into the container's network namespace.
2. **`IOLDockerVM`** (marker `GNS3_IOL_RUNNER=1`): generates the runner's
   config file per start, prepares its runtime directory and cleans up stale
   sockets — the iol-runner-specific glue on top of the vendor path.

## How the image works

```mermaid
graph LR
    subgraph Container["scratch container (PID 1)"]
        RUNNER["/iol-runner -config /config/iol-config.json -stdio"]
        IOL["IOL process<br/>(IOS-XE 17.18.02)"]
        NETIOMUX["netiomux"]
        SOCKETS["/tmp/s00.sock (recv)<br/>/tmp/c00.sock (send-to path)<br/>… one pair per interface"]
        RUNNER -->|"spawn -e/-s/-m + app id"| IOL
        IOL -->|"netio bus /tmp/netio&lt;uid&gt;/"| NETIOMUX --> SOCKETS
    end
    subgraph Host
        UBRIDGE["uBridge bridgeN<br/>add_nio_unix …/gns3/unixio/&lt;node&gt;/cNN.sock …<br/>+ add_nio_udp (topology)"]
        RTDIR["/run/user/&lt;uid&gt;/gns3/unixio/&lt;node&gt;<br/>(bind-mounted at /tmp)"]
        VOL["project-files/docker/&lt;node&gt;/config<br/>(+ tmp/run, nested bind at /tmp/run)"]
    end
    SOCKETS <-->|"same files, two spellings<br/>(the /tmp bind)"| RTDIR <--> UBRIDGE
    UBRIDGE -.->|"iol-config.json +<br/>persistent /tmp/run"| VOL
```

* **Console**: the runner muxes the IOS console onto PID 1 stdio (`-stdio`
  entrypoint flag). The plain `console_type: "telnet"` attaches to it — no
  `docker_exec` needed. The runner requires a TTY, which GNS3 always
  allocates; without one the runner exits (`inappropriate ioctl for device`).
* **Networking**: the runner does not touch the container's network
  namespace. Per interface N it creates, inside the container's `/tmp`: a
  receive socket `s%02d.sock` (frames sent there are injected into guest
  interface N) and a send-to path `c%02d.sock` (whoever binds it receives
  the guest's frames). Frames are **raw Ethernet**, one datagram per frame —
  the same two-mailbox convention uBridge's `add_nio_unix` natively speaks
  (it binds the c-socket, sends to the s-socket). GNS3 bind-mounts a
  per-node directory from the runtime directory
  (`/run/user/<uid>/gns3/unixio/<node-id>`, next to the uBridge control
  sockets) at the container's `/tmp`, so uBridge reaches the sockets as
  plain host files: the path stays far under AF_UNIX's 107-byte `sun_path`
  cap (a projects-tree node path alone exceeds it) and the directory is
  owned by the server user, to whom the runner drops its privileges. This
  mirrors how CML itself runs the image (`source=…/tmp,target=/tmp` in its
  node definition). The directory is ephemeral and removed with the node.
* **Licensing**: the image ships a self-consistent `/etc/hostid` + `.iourc`
  pair, and the runner regenerates the license from the host ID at boot —
  nothing to configure.
* **Persistence**: `/tmp/run` (the IOL working directory) holds the NETMAP,
  the startup-config (`config`, plain IOS format) and NVRAM (`nvram_00001`).
  It is the only `/tmp` path that needs to survive: GNS3 bind-mounts the
  node directory's `tmp/run/` at `/tmp/run` (nested inside the runtime-dir
  bind), so the router's configuration survives stop/start and container
  recreation while sockets, netio buses and runner logs stay ephemeral.
  The generated config maps the runner to the server's uid/gid
  (`user-id`/`group-id`), so all files it creates are owned by the server
  user (no permission-fix pass needed).

## Template

Create the template once via `POST /v3/templates` (authenticated — see the
API docs for the auth flow), or in the Web UI under
*Edit → Preferences → Docker templates → New* with the same fields:

```json
{
    "name": "IOS-XE 17.18.02 IOL",
    "template_type": "docker",
    "image": "iol-xe/iol-xe:17-18-02",
    "category": "router",
    "symbol": ":/symbols/router.svg",
    "adapters": 2,
    "console_type": "telnet",
    "environment": "GNS3_IOL_RUNNER=1",
    "extra_volumes": ["/config"]
}
```

| Field | Value | Why |
|---|---|---|
| `environment` | `GNS3_IOL_RUNNER=1` | The switch that selects `IOLDockerVM` (skip-init, unix-socket NIO, auto volumes). Optional: `GNS3_IOL_MEMORY=<MB>` (default 2048). |
| `extra_volumes` | `["/config"]` | `/tmp/run` is auto-added. **Never add `/tmp`** — it would persist the socket directory into the projects tree and uBridge would reject the too-long AF_UNIX path. |
| `adapters` | number of 4-port units | The IOU convention: one adapter = `Ethernet0/0`–`Ethernet0/3`, two adapters add `Ethernet1/0`–`1/3`, … (8 units / 32 ports max). Ports are addressed as (adapter, port 0–3) and shown grouped in the UI. |
| `memory` | optional; `0` (default) = no cap | Unset works — Docker applies no limit. When you do set a cap, keep it at IOL memory + ~512 MB, or the cgroup OOM-killer shoots the router. |
| `console_type` | `telnet` | The runner muxes the IOS console onto PID 1 stdio; `docker_exec` is not needed. |

### Verify

1. The node's port list shows the grouped IOL interfaces
   (`Ethernet0/0`–`Ethernet1/3` for two adapters), addressed
   (adapter, port).
2. Drop a node into a project and start it — the console shows the
   `Linux Unix (i686)` banner within seconds.
3. `$XDG_RUNTIME_DIR/gns3/unixio/<node-id>/` contains `s00.sock`… (one
   pair per port).
4. The startup-config lives at
   `project-files/docker/<node>/tmp/run/config` (interface names
   `Ethernet0/0`, not `GigabitEthernet0/0`).

## Server mechanisms

| Mechanism | Where | What it does |
|---|---|---|
| `GNS3_UNIX_SOCKET_NIO=1` | `VendorDockerVM` | `_add_ubridge_connection` override: `bridge create` + `bridge add_nio_unix <dir>/c{N:02d}.sock <dir>/s{N:02d}.sock` instead of TAP + `docker move_to_ns`. No TAP allocation, no `set_mac_addr`, namespace untouched. The socket directory is bound from a per-node runtime directory unless a persisted volume already covers it. |
| `GNS3_UNIX_SOCKET_DIR=<dir>` | `VendorDockerVM` | In-container socket directory (default `/tmp`). Any image whose agent exposes the `s%02d`/`c%02d` datagram pairs can use this without the IOL specifics. |
| `GNS3_IOL_RUNNER=1` | `IOLDockerVM` (selected in the manager) | Forces skip-init + unix-socket NIO + the `/config` and `/tmp/run` volumes; on every start writes `<node>/config/iol-config.json` (`num-eth` = adapter count, `num-serial` = 0, memory from `GNS3_IOL_MEMORY`, default 2048), creates `<node>/tmp/run/` (the IOL process dies without it) and removes stale sockets/netio dirs from the socket directory (`tmp/run` is never touched). |
| `restart()` hardening | `IOLDockerVM` | The base `docker restart` would boot the runner on a stale config and leave uBridge wired to the previous run's sockets; reload becomes graceful stop (SIGTERM → NVRAM flush) + full start. |

`GNS3_STOP_TIMEOUT` (default 60) controls the SIGTERM grace period on stop.
Extra iol-runner flags can be passed via `start_command`, e.g. `-keep`
(L1 keepalives) or `-debug 9` (verbose `process.log` — very useful when
diagnosing wiring issues).

## Notes and caveats

* **Memory sizing**: `memory` caps the whole container; the IOL process gets
  `GNS3_IOL_MEMORY` (default 2048 MB). Keep container memory at IOL memory
  + ~512 MB headroom or the OOM-killer will shoot the router.
* **MAC addresses**: the `mac_address` template field and per-adapter custom
  MACs are ignored — IOL derives its own scheme from the node's application
  ID (`aabb.cc{app}{iface}`), e.g. `aabb.cc03.0400`. The controller
  allocates the ID at node creation from the upper half of the id space
  (512–1022, disjoint from IOU's 1–511, limit 511 IOL Docker nodes across
  opened projects sharing computes); without an allocation (raw compute API,
  pre-allocation topologies) a stable node-derived fallback in the same
  range is used. Nodes sharing an ID would silently drop each other's
  frames as MAC loops.
* **Interface names are IOL-style `Ethernet0/0`**, not `GigabitEthernet0/0`
  (4 ports per unit, matching the adapter-count granularity) — startup
  configs addressing `GigabitEthernet…` are rejected by the parser.
* **Adapters**: one adapter is a 4-port unit (the IOU model): change the
  count while the node is stopped; the config is regenerated on the next
  start (`num-eth` = adapters × 4) and the runner creates the matching
  socket set.
* **Stop before editing**: NVRAM is only flushed on a graceful stop (SIGTERM,
  "cleanup done" in `process.log`); a kill loses the running-config changes
  since the last `write memory`.
* **Class selection is create-time**: toggling `GNS3_IOL_RUNNER` via PUT
  takes effect after a project reload (same as `docker_exec`).
* The startup-config lives at `project-files/docker/<node>/tmp/run/config`;
  `extra_configs` targets under persisted volumes are warned against by the
  generic create path — edit the file directly or paste via the console.