c343ce0b8f
The Ethernet switch's kernel fast path: instead of a link crossing the
switch's per-port uBridge relay, the switch absorbs the peer's anchor into
its own kernel bridge. The peer's interface (Docker veth host end, QEMU
TAP, IOU port TAP, Dynamips port TAP) becomes the switch port, and frames
cross anchor -> switch bridge -> switch ports entirely in the kernel.
Wire format: the switch end receives nio_anchor ('join this interface to
my own bridge' — the mirror of nio_bridge), the peer end nio_bridge with a
null bridge ('your anchor is bridged elsewhere': carrier, markers and
impairments only — never bridge membership, and never a bridge delete, on
an interface this node does not own). Anchor names come from the shared
naming contract (utils.kernel_anchor), a pure function of node type, id,
adapter and port — the controller computes the peer's anchor while the
node may be stopped, which is what makes links to stopped nodes wireable.
Stopped peers defer the join; after any node of a link starts
(UDPLink.node_started) the controller re-pushes the switch NIO, and the
switch completes — or repairs, when a peer restart replaced its interface
under the same name — the join against the kernel's actual membership
instead of assuming it.
VLAN changes now edit membership in place: only the ports whose mode/VLAN
actually changed are touched, each losing exactly the previous mode's
entries the new mode does not want (the dot1q admits-all entry is one
range operation in both directions), and no port ever leaves the bridge to
change its VLANs. This replaces the old 'reset by re-enslaving' shortcut
(delif+addif on every wired port, added when the ports were the switch's
own TAPs): on absorbed anchors, re-enslaving an interface owned by another
node is where live testing watched links die — anchors occasionally lost
their bridge membership right after a ports_mapping update (later updates
then failed with delif EINVAL), reproducibly with qemu, IOU and Dynamips
peers and never with Docker's veths.
Eligibility: the switch side needs no capability of its own (its bridge
exists by construction); the peer must be able to anchor. Switch-to-switch
cascades stay on the relay — a kernel interface belongs to one bridge, and
joining two bridges needs a veth pair, deferred.
Verified live on a real server: qemu peers through four VLAN cycles with
both anchors enslaved throughout; a mixed switch (2 IOU + 2 Dynamips, four
kernel ports); Docker peers with real ICMP isolating and recovering (with
both anchors still enslaved); VPCS relay ports likewise in place.
This documentation is organized by AI with reference to actual code. AI can make mistakes — please verify against the source code when in doubt.
GNS3 Server Documentation
License
This documentation is licensed under the Creative Commons Attribution-ShareAlike 4.0 International License (CC BY-SA 4.0).
⚠️ Important - ShareAlike Requirement: If you create derivative works based on this documentation (including software that incorporates substantial portions of the documentation), your work must also be licensed under CC BY-SA 4.0 or a compatible license (such as GPLv3).
- 📄 Full License Text: See docs/LICENSE
- 🔗 License URL: https://creativecommons.org/licenses/by-sa/4.0/
- 📖 Compatibility: https://creativecommons.org/compatiblelicenses
Dual License Structure:
- 📚 Documentation: CC BY-SA 4.0 (this directory)
- 💻 Software Code: GPLv3 (see root LICENSE)
Technical documentation for the GNS3 server project, covering features, AI Copilot, development setup, and known issues.
Directory Structure
docs/
├── README.md # This file
├── development-setup.md # Ubuntu 24.04 development environment setup
├── openapi.json # OpenAPI specification
├── features/ # Feature documentation
│ ├── compute-controller-setup.md # Controller + Compute architecture & configuration
│ ├── statistics-api.md # Aggregated statistics API for monitoring
│ ├── vnc-websocket-console.md # Browser-based VNC console via WebSocket
│ └── web-wireshark-business-process.md # Web Wireshark (Docker + xpra packet capture)
├── design/ # Design proposals & roadmaps (not yet implemented)
│ └── docker-image-type.md # Docker image types: vendor profile discriminator + registry
├── gns3-copilot/ # AI Copilot feature documentation
│ ├── netmiko_devices.md # Netmiko supported devices (366 types)
│ ├── template-based-configuration-roadmap.md # Future: template-based config with HITL
│ └── implemented/ # Implemented features
│ ├── chat-api.md # Chat API (SSE, session management)
│ ├── llm-model-configs.md # LLM model configuration system
│ ├── command-security.md # Command security and filtering
│ ├── context-window-management.md # Context window optimization
│ ├── node-control-tools.md # Node start/stop/suspend tools
│ └── multi-vendor-device-support.md # Multi-vendor device support
└── bugs/ # Known issues & bug reports
└── telnet-server-connection-race-condition.md
Features
Image inventory synchronization
Image Manager's Sync Images action reconciles the catalog with the configured
image directories. Automatic synchronization uses filesystem events and periodic
scans (auto_discover_images, image_sync_interval, default 900 seconds).
New and changed images are checksummed; missing records retain their IDs and
template associations and become available again when restored at the same path.
The /v3/images/sync API supports dry-run and forced checksum verification.
Database migration d9e8a2b7c401 is required when upgrading an existing catalog.
Atomic image publication requires filesystem hard-link support.
Controller + Compute Setup (features/compute-controller-setup.md)
Architecture and minimum configuration for setting up GNS3 Controller with remote Compute nodes. Covers compute node config, controller registration, and multi-compute deployment.
Statistics API (features/statistics-api.md)
Aggregated server statistics API (GET /v3/statistics) for monitoring dashboards. Collects compute resources, project/node/link counts, and Web Wireshark container status in a single request.
VNC WebSocket Console (features/vnc-websocket-console.md)
Browser-based VNC console access via WebSocket. The Controller acts as WebSocket-to-WebSocket relay, and Compute bridges WebSocket to TCP for QEMU/Docker VMs. Supports noVNC clients.
API Error Responses (features/api-error-responses.md)
Unified error response format across all GNS3 API endpoints. Documents HTTP status codes, error types, and client-side error handling patterns.
Web Wireshark (features/web-wireshark-business-process.md)
Web-based packet capture analysis using Docker + xpra HTML5 client. Zero-install Wireshark experience directly in the browser, integrated with GNS3 topologies.
Marker (Traffic Insight) (features/marker-traffic-insight.md)
Real-time traffic insight via per-link BPF markers and project-level inherited definitions. A marker taps a link in uBridge, emitting match notifications and pcap capture on BPF hit; definitions fan out to every capable link automatically.
Marker Tag Replay (features/marker-tag-replay.md)
Aggregate playback across links keyed by tag: once every marker under a tag is paused, their pcaps merge into one timestamp-ordered timeline; frames are decoded on demand via tshark into an isomorphic JSON protocol tree. The cross-link delta of the same packet measures the intermediate node's forwarding latency.
Docker exec Console (Vendor NOS) (features/docker-exec-console.md)
Console for vendor NOS containers (SR Linux, XRd, …) whose CLI is a TUI off PID 1: runs the vendor CLI via the Docker exec API, plus GNS3_SKIP_INIT/GNS3_INTERFACE_NAMES boot knobs and SKIP_INIT volume persistence.
Cisco XRd Control Plane (features/vendor-nos-xrd.md)
Cisco XRd as a GNS3 Docker router: vendor path + shm/device injection (GNS3_SHM_SIZE/GNS3_DEVICES), config-file injection (extra_configs), udev masking (GNS3_MASK_UDEV) so privileged systemd containers don't disturb the host, and the host-readiness check.
IOL Images with iol-runner (features/iol-runner-docker.md)
Cisco CML containerized IOL (e.g. iol-xe/iol-xe:17-18-02) as GNS3 Docker routers: generic unix-socket NIO (GNS3_UNIX_SOCKET_NIO — adapters wired via AF_UNIX datagram socket pairs instead of TAP/netns) plus IOLDockerVM (GNS3_IOL_RUNNER=1 — per-start config generation, /tmp/run preparation, stale-socket cleanup, console on PID 1 stdio).
Design & Roadmaps (design/)
Docker Image Types (design/docker-image-type.md)
Proposed image_type discriminator on Docker templates plus a compute-side profile registry: vendor parameters graduate from environment markers into schema-gated fields, generic-feature applicability becomes declared capability data, and the existing markers remain as a compatibility fallback. Not a new node type — vendor images are content, not mechanism.
GNS3 AI Copilot (gns3-copilot/)
Implemented Features
| Feature | Description | Status |
|---|---|---|
| Chat API | SSE streaming, session management, token statistics | Implemented |
| LLM Model Configs | Multi-level model config (system/group/user) | Implemented |
| Command Security | Command filtering, dangerous operation detection, HITL | Implemented |
| Context Window Management | Token optimization, content filtering, compression | Implemented |
| Node Control Tools | Start/stop/suspend with batch ops and progress tracking | Implemented |
| Multi-Vendor Support | Cisco, Huawei, Ruijie, VPCS with custom Netmiko drivers | Implemented |
Reference
- Netmiko Supported Devices — 366 device types (154 SSH, 55 Telnet, 3 custom GNS3 drivers)
Roadmap
- Template-Based Configuration with HITL — Jinja2 templates with human-in-the-loop confirmations for device configuration and node creation
Known Issues (bugs/)
- Telnet Server Connection Race Condition —
getpeername()error when client disconnects during connection setup (High severity, Open) - Docker Link UDP Self-Loop — intermittent one-way link (both ends handed the same UDP port by an allocation race); fixed (Medium severity)
Development Setup (development-setup.md)
Quick-start guide for Ubuntu 24.04: install via PPA, set up dependencies, and run gns3-server from source.
Related Documentation
- GNS3 Server API Documentation — Interactive API docs (also available locally via
redoc.html) - GNS3 Web UI Documentation
- LangGraph Documentation
Last updated: 2026-09-01