cmd/tsmcp: add a MCP implementationbradfitz/mcp

Change-Id: I6e2a391dfe0929e6c44a537456fb2ea4c06b603b
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

1 files changed, 94 insertions, 0 deletions

diff --git a/cmd/tsmcp/tsmcp.go b/cmd/tsmcp/tsmcp.go
new file mode 100644
index 000000000..3016f8088
--- /dev/null
+++ b/cmd/tsmcp/tsmcp.go
@@ -0,0 +1,94 @@
+package main
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/mark3labs/mcp-go/mcp"
+	"github.com/mark3labs/mcp-go/server"
+	"tailscale.com/client/local"
+	"tailscale.com/ipn"
+)
+
+func main() {
+	var s Server
+	s.lc = new(local.Client)
+
+	// Create MCP server
+	s.ms = server.NewMCPServer(
+		"Tailscale",
+		"1.0.0",
+	)
+
+	// Add tool
+	toolStatus := mcp.NewTool("get_connection_status",
+		mcp.WithDescription("Check Tailscale's connection status"),
+		// mcp.WithString("name",
+		//     mcp.Required(),
+		//     mcp.Description("Name of the person to greet"),
+		// ),
+	)
+
+	s.ms.AddTool(toolStatus, s.statusHandler)
+
+	toolUp := mcp.NewTool("up",
+		mcp.WithDescription("Turn Tailscale on (run 'tailscale up')"),
+	)
+	s.ms.AddTool(toolUp, s.upHandler)
+
+	toolDown := mcp.NewTool("down",
+		mcp.WithDescription("Turn Tailscale off (run 'tailscale down')"),
+	)
+	s.ms.AddTool(toolDown, s.downHandler)
+
+	// Start the stdio server
+	if err := server.ServeStdio(s.ms); err != nil {
+		fmt.Printf("Server error: %v\n", err)
+	}
+}
+
+type Server struct {
+	lc *local.Client
+	ms *server.MCPServer
+}
+
+func (s *Server) statusHandler(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+	status, err := s.lc.StatusWithoutPeers(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get connection status: %w", err)
+	}
+	switch status.BackendState {
+	case "NoState":
+		return mcp.NewToolResultText("In 'NoState', meaning it's broken or wedged or hung or maybe very early in its startup life cycle. But probably broken."), nil
+	case "Starting":
+		return mcp.NewToolResultText("In 'Starting', meaning it's starting up, but not yet fully connected. In particular, the control plane connection might be up, but no DERP yet."), nil
+	default:
+		return mcp.NewToolResultText(status.BackendState), nil
+	}
+}
+
+func (s *Server) upHandler(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+	_, err := s.lc.EditPrefs(ctx, &ipn.MaskedPrefs{
+		WantRunningSet: true,
+		Prefs: ipn.Prefs{
+			WantRunning: true,
+		},
+	})
+	if err != nil {
+		return nil, fmt.Errorf("failed to turn on Tailscale: %w", err)
+	}
+	return mcp.NewToolResultText("done"), nil
+}
+
+func (s *Server) downHandler(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+	_, err := s.lc.EditPrefs(ctx, &ipn.MaskedPrefs{
+		WantRunningSet: true,
+		Prefs: ipn.Prefs{
+			WantRunning: false,
+		},
+	})
+	if err != nil {
+		return nil, fmt.Errorf("failed to turn off Tailscale: %w", err)
+	}
+	return mcp.NewToolResultText("done"), nil
+}