daemon

Overview ¶

Package daemon provides APIs for SCION applications to interact with the SCION control plane. It supports two modes of operation:

• Standalone mode: Runs daemon functionality in-process, communicating directly with the control service. No separate daemon process required.
• Remote mode: Connects to a SCION daemon process via gRPC.

Quick Start ¶

Use NewAutoConnector with WithDaemon (for remote daemon) or WithConfigDir (for standalone mode):

// Remote daemon connection
conn, err := daemon.NewAutoConnector(ctx, daemon.WithDaemon("127.0.0.1:30255"))

// Or standalone mode with local config
conn, err := daemon.NewAutoConnector(ctx, daemon.WithConfigDir("/etc/scion"))

if err != nil {
    log.Fatal(err)
}
defer conn.Close()

// Query paths to a destination
paths, err := conn.Paths(ctx, dstIA, srcIA, daemon.PathReqFlags{})

If both WithDaemon and WithConfigDir are set, WithDaemon takes priority. Empty string options are ignored, making it safe to pass values from CLI flags:

conn, err := daemon.NewAutoConnector(ctx,
    daemon.WithDaemon(daemonAddr),    // may be empty
    daemon.WithConfigDir(configDir),  // may be empty
)

Standalone Mode ¶

Standalone mode runs the daemon logic in-process, which is useful for:

• Deployments without a separate daemon process
• CLI tools that need minimal dependencies
• Testing and development

For more control over standalone mode, use NewStandaloneConnector directly:

// Load topology information
localASInfo, err := daemon.LoadASInfoFromFile("/etc/scion/topology.json")
if err != nil {
    log.Fatal(err)
}

// Create standalone connector with options
conn, err := daemon.NewStandaloneConnector(ctx, localASInfo,
    daemon.WithCertsDir("/etc/scion/certs"),     // TRC certificates location
    daemon.WithMetrics(),                         // Enable Prometheus metrics
    daemon.WithPeriodicCleanup(),                 // Enable path DB cleanup
)
if err != nil {
    log.Fatal(err)
}
defer conn.Close()

Standalone mode requires:

• topology.json: Network topology file with control service addresses
• certs/: Directory containing TRC files for segment verification (required via WithCertsDir)

To disable segment verification (NOT recommended for production):

conn, err := daemon.NewStandaloneConnector(ctx, localASInfo,
    daemon.WithDisabledSegVerification(),
)

Remote Mode ¶

Remote mode connects to a running SCION daemon via gRPC. Use NewService to create a connection factory:

svc := daemon.NewService("127.0.0.1:30255")
conn, err := svc.Connect(ctx)
if err != nil {
    log.Fatal(err)
}
defer conn.Close()

The Connector Interface ¶

The Connector interface is the central abstraction of this package. All connection modes (standalone, remote) implement this interface, allowing applications to work with any backend transparently.

See Connector for all available methods.

Loading Topology ¶

To get topology information (local IA, port range, interfaces) from a connector:

// One-time load
topo, err := daemon.LoadTopology(ctx, conn)

// Auto-reloading topology (for long-running applications)
reloadingTopo, err := daemon.NewReloadingTopology(ctx, conn)
go reloadingTopo.Run(ctx, 30*time.Second)
topo := reloadingTopo.Topology()

Helper Types ¶

The package provides helper types for common patterns:

// Querier wraps a Connector for path queries
querier := daemon.Querier{Connector: conn, IA: localIA}
paths, err := querier.Query(ctx, dstIA)

// RevHandler adapts Connector for snet.RevocationHandler
revHandler := daemon.RevHandler{Connector: conn}

// TopoQuerier provides topology queries
topoQuerier := daemon.TopoQuerier{Connector: conn}
addr, err := topoQuerier.UnderlayAnycast(ctx, addr.SvcCS)