#
# Copyright (C) 2026 GNS3 Technologies Inc.
# Author: Yue Guobin
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see .
"""
MCP (Model Context Protocol) service for GNS3 server.
Implements the standard MCP protocol over SSE transport using FastMCP:
/v3/mcp/sse — SSE stream
/v3/mcp/messages/ — JSON-RPC messages
Tools are registered via @mcp.tool() decorators.
"""
import contextvars
import json
import asyncio
import logging
import socket
from typing import Any, Annotated
from urllib.parse import parse_qs
from fastapi import APIRouter
from fastapi.responses import Response
from pydantic import Field
from mcp.server.fastmcp import FastMCP
from mcp.server.transport_security import TransportSecuritySettings
from gns3server.config import Config
from gns3server.services import auth_service
from gns3server.utils.request_utils import extract_client_info
from .projects import (
list_projects_handler, get_project_handler, create_project_handler,
delete_project_handler, open_project_handler, close_project_handler,
get_project_stats_handler, update_project_handler, duplicate_project_handler,
get_project_readme_handler, update_project_readme_handler,
)
from .nodes import (
get_nodes_handler, get_node_handler, start_node_handler,
stop_node_handler, reload_node_handler, suspend_node_handler,
create_node_handler, delete_node_handler, update_node_handler,
get_node_console_info_handler,
)
from .links import (
get_links_handler, get_link_handler, create_link_handler,
delete_link_handler, update_link_handler,
)
from .templates import (
list_templates_handler, get_template_handler, create_template_handler,
update_template_handler, delete_template_handler,
)
from .computes import (
list_computes_handler, get_compute_handler, get_compute_images_handler,
)
log = logging.getLogger(__name__)
# ── Server ready state ────────────────────────────────────────────────
# Tracks whether GNS3 server has completed initialization.
# MCP connections wait up to 5 seconds for startup to complete, then return
# 503 Service Unavailable if initialization is not complete to prevent
# "Received request before initialization was complete" errors.
_mcp_ready_event = asyncio.Event()
def set_mcp_server_ready(ready: bool = True) -> None:
"""
Set MCP server ready state.
Should be called after GNS3 startup completes (database, controller, etc.)
to allow MCP connections to proceed.
Args:
ready: True to mark server as ready, False to mark as not ready
"""
if ready:
_mcp_ready_event.set()
log.info("MCP server is now ready to accept connections")
else:
_mcp_ready_event.clear()
async def wait_for_mcp_ready() -> bool:
"""
Wait until MCP server is ready before accepting connections.
Returns:
True if server is ready, False if timeout reached
Returns immediately if already ready. Otherwise waits with a timeout
and returns False if server does not become ready in time.
"""
if _mcp_ready_event.is_set():
return True
log.debug("MCP server not ready yet, waiting for initialization to complete...")
try:
await asyncio.wait_for(_mcp_ready_event.wait(), timeout=5.0)
log.debug("MCP server is now ready, proceeding with connection")
return True
except asyncio.TimeoutError:
log.warning(
"MCP server ready check timed out after 5 seconds - "
"GNS3 server initialization may have issues"
)
return False
# ── Per‑connection JWT token ─────────────────────────────────────────
# Set during SSE authentication, read by tool handlers running in the
# same asyncio task (contextvars propagate through asyncio.to_thread).
_jwt_token_var: contextvars.ContextVar[str | None] = contextvars.ContextVar(
"mcp_jwt_token", default=None
)
# ── Token validation ──────────────────────────────────────────────────
async def _validate_token(token: str) -> bool:
"""Return True if token is a valid GNS3 JWT."""
try:
auth_service.get_username_from_token(token)
return True
except Exception:
return False
# ── Server URL helper ─────────────────────────────────────────────────
def _server_url() -> str:
cfg = Config.instance().settings
host = cfg.Server.host
if host in ("0.0.0.0", "::"):
try:
with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as s:
s.settimeout(0.1)
s.connect(("8.8.8.8", 80))
host = s.getsockname()[0]
except OSError:
host = "127.0.0.1"
scheme = "https" if cfg.Server.enable_ssl else "http"
return f"{scheme}://{host}:{cfg.Server.port}"
# ── FastMCP Server ────────────────────────────────────────────────────
def _create_mcp_server() -> FastMCP:
"""Create MCP server with security settings from configuration."""
cfg = Config.instance().settings.Server
# Always pass an explicit TransportSecuritySettings to prevent FastMCP
# from auto-enabling protection when host is localhost (its default).
if cfg.mcp_enable_dns_rebinding_protection:
transport_security = TransportSecuritySettings(
enable_dns_rebinding_protection=True,
allowed_hosts=cfg.mcp_allowed_hosts or ["127.0.0.1:*", "localhost:*"],
allowed_origins=cfg.mcp_allowed_origins or ["http://127.0.0.1:*", "http://localhost:*"],
)
else:
transport_security = TransportSecuritySettings(
enable_dns_rebinding_protection=False,
)
mcp = FastMCP("GNS3 MCP Server", transport_security=transport_security)
return mcp
mcp = _create_mcp_server()
# ── Tool handlers ─────────────────────────────────────────────────────
def _run_handler_sync(handler, params: dict[str, Any]) -> list[dict[str, Any]]:
"""Run a synchronous Gns3Connector handler in a thread."""
ctx = {
"server_url": _server_url(),
"jwt_token": _jwt_token_var.get(),
}
result = handler(params, ctx)
return [{"type": "text", "text": json.dumps(result, ensure_ascii=False, default=str)}]
@mcp.tool()
async def list_projects() -> list[dict[str, Any]]:
"""List all GNS3 projects accessible to the current user."""
return await asyncio.to_thread(_run_handler_sync, list_projects_handler, {})
@mcp.tool()
async def get_project(
project_id: Annotated[str, Field(description="UUID of the project")],
) -> list[dict[str, Any]]:
"""Get detailed information about a specific project."""
return await asyncio.to_thread(_run_handler_sync, get_project_handler, {"project_id": project_id})
@mcp.tool()
async def create_project(
name: Annotated[str, Field(description="Project name")],
description: Annotated[str, Field(description="Optional project description")] = "",
) -> list[dict[str, Any]]:
"""Create a new GNS3 project."""
params = {"name": name}
if description:
params["description"] = description
return await asyncio.to_thread(_run_handler_sync, create_project_handler, params)
@mcp.tool()
async def delete_project(
project_id: Annotated[str, Field(description="UUID of the project to delete")],
) -> list[dict[str, Any]]:
"""Delete a GNS3 project permanently."""
return await asyncio.to_thread(_run_handler_sync, delete_project_handler, {"project_id": project_id})
@mcp.tool()
async def open_project(
project_id: Annotated[str, Field(description="UUID of the project to open")],
) -> list[dict[str, Any]]:
"""Open a closed GNS3 project."""
return await asyncio.to_thread(_run_handler_sync, open_project_handler, {"project_id": project_id})
@mcp.tool()
async def close_project(
project_id: Annotated[str, Field(description="UUID of the project to close")],
) -> list[dict[str, Any]]:
"""Close an open GNS3 project."""
return await asyncio.to_thread(_run_handler_sync, close_project_handler, {"project_id": project_id})
@mcp.tool()
async def get_project_stats(
project_id: Annotated[str, Field(description="UUID of the project to get statistics for")],
) -> list[dict[str, Any]]:
"""Get statistics (nodes, links, snapshots, drawings) for a project."""
return await asyncio.to_thread(_run_handler_sync, get_project_stats_handler, {"project_id": project_id})
@mcp.tool()
async def update_project(
project_id: Annotated[str, Field(description="UUID of the project to update")],
name: Annotated[str, Field(description="New project name")] = None,
auto_close: Annotated[bool, Field(description="Close project when last client leaves")] = None,
auto_open: Annotated[bool, Field(description="Project opens when GNS3 starts")] = None,
auto_start: Annotated[bool, Field(description="Project starts when opened")] = None,
scene_width: Annotated[int, Field(description="Width of the drawing area")] = None,
scene_height: Annotated[int, Field(description="Height of the drawing area")] = None,
zoom: Annotated[int, Field(description="Zoom of the drawing area")] = None,
show_layers: Annotated[bool, Field(description="Show layers on the drawing area")] = None,
snap_to_grid: Annotated[bool, Field(description="Snap to grid on the drawing area")] = None,
show_grid: Annotated[bool, Field(description="Show the grid on the drawing area")] = None,
grid_size: Annotated[int, Field(description="Grid size for the drawing area for nodes")] = None,
drawing_grid_size: Annotated[int, Field(description="Grid size for the drawing area for drawings")] = None,
show_interface_labels: Annotated[bool, Field(description="Show interface labels on the drawing area")] = None,
) -> list[dict[str, Any]]:
"""Update a project's properties (name, auto_close, auto_open, etc.)."""
params = {"project_id": project_id}
local_vars = {
"name": name, "auto_close": auto_close, "auto_open": auto_open, "auto_start": auto_start,
"scene_width": scene_width, "scene_height": scene_height, "zoom": zoom,
"show_layers": show_layers, "snap_to_grid": snap_to_grid, "show_grid": show_grid,
"grid_size": grid_size, "drawing_grid_size": drawing_grid_size, "show_interface_labels": show_interface_labels,
}
for key, val in local_vars.items():
if val is not None:
params[key] = val
return await asyncio.to_thread(_run_handler_sync, update_project_handler, params)
@mcp.tool()
async def duplicate_project(
project_id: Annotated[str, Field(description="UUID of the project to duplicate")],
name: Annotated[str, Field(description="New project name")],
reset_mac_addresses: Annotated[bool, Field(description="Reset MAC addresses for this project")] = False,
) -> list[dict[str, Any]]:
"""Duplicate a project."""
params = {"project_id": project_id, "name": name}
if reset_mac_addresses:
params["reset_mac_addresses"] = reset_mac_addresses
return await asyncio.to_thread(_run_handler_sync, duplicate_project_handler, params)
@mcp.tool()
async def get_project_readme(
project_id: Annotated[str, Field(description="UUID of the project")],
) -> list[dict[str, Any]]:
"""Get the content of a project's README.md file — the project documentation (Markdown format)."""
return await asyncio.to_thread(_run_handler_sync, get_project_readme_handler, {"project_id": project_id})
@mcp.tool()
async def update_project_readme(
project_id: Annotated[str, Field(description="UUID of the project")],
content: Annotated[str, Field(description="Content to write to README.md (Markdown format)")],
) -> list[dict[str, Any]]:
"""Update or create a project's README.md file — the project documentation (Markdown format)."""
return await asyncio.to_thread(_run_handler_sync, update_project_readme_handler, {"project_id": project_id, "content": content})
# ── Node tools ────────────────────────────────────────────────────────
@mcp.tool()
async def get_nodes(project_id: str) -> list[dict[str, Any]]:
"""List all nodes in a project."""
return await asyncio.to_thread(_run_handler_sync, get_nodes_handler, {"project_id": project_id})
@mcp.tool()
async def get_node(
project_id: Annotated[str, Field(description="UUID of the project")],
node_id: Annotated[str, Field(description="UUID of the node")],
) -> list[dict[str, Any]]:
"""Get detailed information about a specific node."""
return await asyncio.to_thread(_run_handler_sync, get_node_handler, {"project_id": project_id, "node_id": node_id})
@mcp.tool()
async def start_node(
project_id: Annotated[str, Field(description="UUID of the project")],
node_id: Annotated[str, Field(description="UUID of the node to start")],
) -> list[dict[str, Any]]:
"""Start a node in a project."""
return await asyncio.to_thread(_run_handler_sync, start_node_handler, {"project_id": project_id, "node_id": node_id})
@mcp.tool()
async def stop_node(
project_id: Annotated[str, Field(description="UUID of the project")],
node_id: Annotated[str, Field(description="UUID of the node to stop")],
) -> list[dict[str, Any]]:
"""Stop a node in a project."""
return await asyncio.to_thread(_run_handler_sync, stop_node_handler, {"project_id": project_id, "node_id": node_id})
@mcp.tool()
async def reload_node(
project_id: Annotated[str, Field(description="UUID of the project")],
node_id: Annotated[str, Field(description="UUID of the node to reload")],
) -> list[dict[str, Any]]:
"""Reload (restart) a node in a project."""
return await asyncio.to_thread(_run_handler_sync, reload_node_handler, {"project_id": project_id, "node_id": node_id})
@mcp.tool()
async def suspend_node(
project_id: Annotated[str, Field(description="UUID of the project")],
node_id: Annotated[str, Field(description="UUID of the node to suspend")],
) -> list[dict[str, Any]]:
"""Suspend a node in a project."""
return await asyncio.to_thread(_run_handler_sync, suspend_node_handler, {"project_id": project_id, "node_id": node_id})
@mcp.tool()
async def create_node(
project_id: Annotated[str, Field(description="UUID of the project")],
template_id: Annotated[str, Field(description="UUID of the template to create the node from")],
x: Annotated[int, Field(description="X coordinate on the project canvas")] = 0,
y: Annotated[int, Field(description="Y coordinate on the project canvas")] = 0,
compute_id: Annotated[str, Field(description="Compute ID (default: local)")] = "local",
) -> list[dict[str, Any]]:
"""Create a new node from a template in a project."""
return await asyncio.to_thread(_run_handler_sync, create_node_handler, {
"project_id": project_id, "template_id": template_id,
"x": x, "y": y, "compute_id": compute_id,
})
@mcp.tool()
async def delete_node(
project_id: Annotated[str, Field(description="UUID of the project")],
node_id: Annotated[str, Field(description="UUID of the node to delete")],
) -> list[dict[str, Any]]:
"""Delete a node from a project."""
return await asyncio.to_thread(_run_handler_sync, delete_node_handler, {"project_id": project_id, "node_id": node_id})
@mcp.tool()
async def update_node(
project_id: Annotated[str, Field(description="UUID of the project")],
node_id: Annotated[str, Field(description="UUID of the node to update")],
**kwargs: Any,
) -> list[dict[str, Any]]:
"""Update a node's properties (name, position, etc.)."""
params = {"project_id": project_id, "node_id": node_id, **kwargs}
return await asyncio.to_thread(_run_handler_sync, update_node_handler, params)
@mcp.tool()
async def get_node_console_info(
project_id: Annotated[str, Field(description="UUID of the project containing the node")],
node_id: Annotated[str, Field(description="UUID of the node to get console info for")],
) -> list[dict[str, Any]]:
"""Get WebSocket console connection info for a node.
Returns the WebSocket URL, console type (telnet/ssh/vnc), and other
connection details needed to interact with a node's console via WebSocket.
Complete workflow:
1. Call this tool with project_id and node_id to get the WebSocket URL
2. Connect to the returned URL using websocat in text mode (-t):
> websocat -t "ws://:3080/v3/projects/{project_id}/nodes/{node_id}/console/ws?token={jwt_token}"
3. Send device commands with \\r\\n line endings via heredoc:
> websocat -t "ws://..." <<< $'\\r\\nenable\\r\\nshow version\\r\\nexit\\r\\n'
4. Receive response: websocat receives and displays device output
Use 'timeout' to avoid connection hanging:
> timeout 10 websocat -t "ws://..." <<< $'commands\\r\\n'
Key points:
- Use \\r\\n (not \\n) to match console protocol line endings
- Use $'...' format for escape sequences in bash
- Set a timeout to prevent hanging connections
"""
return await asyncio.to_thread(_run_handler_sync, get_node_console_info_handler, {
"project_id": project_id, "node_id": node_id,
})
# ── Link tools ────────────────────────────────────────────────────────
@mcp.tool()
async def get_links(project_id: str) -> list[dict[str, Any]]:
"""List all links in a project."""
return await asyncio.to_thread(_run_handler_sync, get_links_handler, {"project_id": project_id})
@mcp.tool()
async def get_link(
project_id: Annotated[str, Field(description="UUID of the project")],
link_id: Annotated[str, Field(description="UUID of the link")],
) -> list[dict[str, Any]]:
"""Get detailed information about a specific link."""
return await asyncio.to_thread(_run_handler_sync, get_link_handler, {"project_id": project_id, "link_id": link_id})
@mcp.tool()
async def create_link(
project_id: Annotated[str, Field(description="UUID of the project")],
nodes: Annotated[list, Field(description="List of node connections, e.g. [{\"node_id\": \"...\", \"adapter_number\": 0, \"port_number\": 0}]")],
link_type: Annotated[str, Field(description="Link type - ethernet or serial")] = "ethernet",
filters: Annotated[dict, Field(description="Optional packet filters (must use array format): frequency_drop: [N], packet_loss: [rate], delay: [ms, jitter], corrupt: [rate], bpf: [expression]")] = None,
) -> list[dict[str, Any]]:
"""Create a link between two nodes in a project.
Filters must use array format:
- frequency_drop: [N] - Drop every Nth packet (N: -1 to 32767)
- packet_loss: [rate] - Packet loss percentage (rate: 0 to 100)
- delay: [ms, jitter] - Latency and jitter in milliseconds
- corrupt: [rate] - Packet corruption percentage (rate: 0 to 100)
- bpf: [expression] - Berkeley Packet Filter expression
Example: {"filters": {"delay": [100, 10], "packet_loss": [5]}}
"""
params = {"project_id": project_id, "nodes": nodes, "link_type": link_type}
if filters:
params["filters"] = filters
return await asyncio.to_thread(_run_handler_sync, create_link_handler, params)
@mcp.tool()
async def delete_link(
project_id: Annotated[str, Field(description="UUID of the project")],
link_id: Annotated[str, Field(description="UUID of the link to delete")],
) -> list[dict[str, Any]]:
"""Delete a link from a project."""
return await asyncio.to_thread(_run_handler_sync, delete_link_handler, {"project_id": project_id, "link_id": link_id})
@mcp.tool()
async def update_link(
project_id: Annotated[str, Field(description="UUID of the project")],
link_id: Annotated[str, Field(description="UUID of the link to update")],
**kwargs: Any,
) -> list[dict[str, Any]]:
"""Update a link's properties (suspend, filters, etc.).
Supported kwargs:
- suspend: boolean - Suspend or resume the link
- filters: dict - Packet filters (must use array format):
* frequency_drop: [N] - Drop every Nth packet (N: -1 to 32767)
* packet_loss: [rate] - Packet loss percentage (rate: 0 to 100)
* delay: [ms, jitter] - Latency and jitter in milliseconds
* corrupt: [rate] - Packet corruption percentage (rate: 0 to 100)
* bpf: [expression] - Berkeley Packet Filter expression
Example filters:
{"filters": {"frequency_drop": [10]}}
{"filters": {"delay": [100, 10]}}
{"filters": {"packet_loss": [5]}}
{"filters": {"delay": [50, 5], "packet_loss": [2]}}
"""
params = {"project_id": project_id, "link_id": link_id, **kwargs}
return await asyncio.to_thread(_run_handler_sync, update_link_handler, params)
# ── Template tools ────────────────────────────────────────────────────
@mcp.tool()
async def list_templates() -> list[dict[str, Any]]:
"""List all available templates on the server."""
return await asyncio.to_thread(_run_handler_sync, list_templates_handler, {})
@mcp.tool()
async def get_template(
template_id: Annotated[str | None, Field(description="Template UUID (optional if name is provided)")] = None,
name: Annotated[str | None, Field(description="Template name (optional if template_id is provided)")] = None,
) -> list[dict[str, Any]]:
"""Get detailed information about a specific template."""
return await asyncio.to_thread(_run_handler_sync, get_template_handler, {
"template_id": template_id, "name": name,
})
@mcp.tool()
async def create_template(
name: Annotated[str, Field(description="Template name")],
template_type: Annotated[str, Field(description="Template type (e.g. qemu, docker, dynamips)")],
compute_id: Annotated[str, Field(description="Compute ID (default: local)")] = "local",
) -> list[dict[str, Any]]:
"""Create a new template."""
return await asyncio.to_thread(_run_handler_sync, create_template_handler, {
"name": name, "template_type": template_type, "compute_id": compute_id,
})
@mcp.tool()
async def update_template(
template_id: Annotated[str | None, Field(description="Template UUID (optional if name is provided)")] = None,
name: Annotated[str | None, Field(description="Template name (optional if template_id is provided)")] = None,
**kwargs: Any,
) -> list[dict[str, Any]]:
"""Update an existing template's properties."""
params = {"template_id": template_id, "name": name, **kwargs}
return await asyncio.to_thread(_run_handler_sync, update_template_handler, params)
@mcp.tool()
async def delete_template(
template_id: Annotated[str | None, Field(description="Template UUID (optional if name is provided)")] = None,
name: Annotated[str | None, Field(description="Template name (optional if template_id is provided)")] = None,
) -> list[dict[str, Any]]:
"""Delete a template."""
return await asyncio.to_thread(_run_handler_sync, delete_template_handler, {
"template_id": template_id, "name": name,
})
# ── Compute tools ─────────────────────────────────────────────────────
@mcp.tool()
async def list_computes() -> list[dict[str, Any]]:
"""List all compute nodes available to the server."""
return await asyncio.to_thread(_run_handler_sync, list_computes_handler, {})
@mcp.tool()
async def get_compute(
compute_id: Annotated[str, Field(description="Compute ID (default: local)")] = "local",
) -> list[dict[str, Any]]:
"""Get detailed information about a compute node."""
return await asyncio.to_thread(_run_handler_sync, get_compute_handler, {"compute_id": compute_id})
@mcp.tool()
async def get_compute_images(
emulator: Annotated[str, Field(description="Emulator type (e.g. qemu, iou, docker)")],
compute_id: Annotated[str, Field(description="Compute ID (default: local)")] = "local",
) -> list[dict[str, Any]]:
"""List available images for an emulator on a compute node."""
return await asyncio.to_thread(_run_handler_sync, get_compute_images_handler, {
"emulator": emulator, "compute_id": compute_id,
})
# ── Auth‑wrapped SSE app ──────────────────────────────────────────────
def _make_auth_wrapper(inner_app):
"""Wrap the SSE app with JWT validation.
Supports two ways to pass the token (checked in order):
1. Authorization: Bearer header
2. ?token= query parameter
POST messages are passed through (authenticated by their session).
"""
async def auth_wrapper(scope, receive, send):
# Wait for GNS3 server to complete initialization before accepting MCP connections
server_ready = await wait_for_mcp_ready()
if not server_ready:
# Server initialization timed out - return 503 Service Unavailable
client_info = extract_client_info(scope, auth_service)
log.warning(
f"Rejecting MCP connection - GNS3 server initialization not complete. "
f"Client: {client_info['host']}:{client_info['port']} ({client_info['user_info']}, Path: {client_info['path']})"
)
response = Response(
"GNS3 server initialization not complete - please retry later",
status_code=503
)
await response(scope, receive, send)
return
if scope["type"] == "http" and scope["method"] == "GET":
token = None
headers = dict(scope.get("headers", []))
auth = headers.get(b"authorization", b"").decode()
if auth.startswith("Bearer "):
token = auth[7:]
if not token:
params = parse_qs(scope.get("query_string", b"").decode())
tokens = params.get("token", [])
if tokens:
token = tokens[0]
if not token or not await _validate_token(token):
response = Response("Missing or invalid token", status_code=401)
await response(scope, receive, send)
return
_jwt_token_var.set(token)
await inner_app(scope, receive, send)
return auth_wrapper
# ── FastAPI router ────────────────────────────────────────────────────
router = APIRouter(prefix="/mcp", tags=["MCP"])
@router.get("/")
async def mcp_root():
"""MCP service metadata."""
return {
"name": "GNS3 MCP Server",
"version": "1.0.0",
"authentication": ["Authorization: Bearer ", "?token="],
"transports": {
"sse": "/v3/mcp/transport/sse",
},
}
def register_starlette_routes(app):
"""Mount MCP transports on the FastAPI app."""
sse_app = _make_auth_wrapper(mcp.sse_app(mount_path=""))
app.mount("/v3/mcp/transport", sse_app, name="mcp-sse")
log.info("MCP SSE server mounted at /v3/mcp/transport")