|
| 1 | +package zeroconf |
| 2 | + |
| 3 | +import ( |
| 4 | + "fmt" |
| 5 | + |
| 6 | + "github.com/godbus/dbus/v5" |
| 7 | +) |
| 8 | + |
| 9 | +const ( |
| 10 | + avahiService = "org.freedesktop.Avahi" |
| 11 | + avahiServerPath = "/" |
| 12 | + avahiServerIface = "org.freedesktop.Avahi.Server" |
| 13 | + avahiEntryGroupIface = "org.freedesktop.Avahi.EntryGroup" |
| 14 | + |
| 15 | + // Avahi constants |
| 16 | + avahiIfUnspec = int32(-1) // AVAHI_IF_UNSPEC - use all interfaces |
| 17 | + avahiProtoUnspec = int32(-1) // AVAHI_PROTO_UNSPEC - use both IPv4 and IPv6 |
| 18 | +) |
| 19 | + |
| 20 | +// AvahiRegistrar implements ServiceRegistrar using avahi-daemon via D-Bus. |
| 21 | +// This allows go-librespot to share the mDNS responder with other services |
| 22 | +// on the system instead of running its own. |
| 23 | +// |
| 24 | +// Compatibility: Requires avahi-daemon 0.6.x or later (uses stable D-Bus API). |
| 25 | +// Tested with avahi 0.7 and 0.8. |
| 26 | +type AvahiRegistrar struct { |
| 27 | + conn *dbus.Conn |
| 28 | + entryGroup dbus.BusObject |
| 29 | + version string |
| 30 | +} |
| 31 | + |
| 32 | +// NewAvahiRegistrar creates a new avahi-daemon service registrar. |
| 33 | +// It connects to the system D-Bus and prepares to register services via avahi. |
| 34 | +func NewAvahiRegistrar() (*AvahiRegistrar, error) { |
| 35 | + conn, err := dbus.SystemBus() |
| 36 | + if err != nil { |
| 37 | + return nil, fmt.Errorf("failed to connect to system bus: %w", err) |
| 38 | + } |
| 39 | + |
| 40 | + // Verify avahi-daemon is available by calling GetHostName (available in all versions) |
| 41 | + server := conn.Object(avahiService, avahiServerPath) |
| 42 | + var hostname string |
| 43 | + err = server.Call(avahiServerIface+".GetHostName", 0).Store(&hostname) |
| 44 | + if err != nil { |
| 45 | + conn.Close() |
| 46 | + return nil, fmt.Errorf("failed to connect to avahi-daemon (is it running?): %w", err) |
| 47 | + } |
| 48 | + |
| 49 | + // Try to get version for logging (optional, may fail on older versions) |
| 50 | + version := getAvahiVersion(server) |
| 51 | + |
| 52 | + return &AvahiRegistrar{conn: conn, version: version}, nil |
| 53 | +} |
| 54 | + |
| 55 | +// getAvahiVersion attempts to retrieve the avahi-daemon version. |
| 56 | +// Returns "unknown" if version cannot be determined. |
| 57 | +func getAvahiVersion(server dbus.BusObject) string { |
| 58 | + // Try GetVersionString first (available in avahi 0.8+) |
| 59 | + var versionStr string |
| 60 | + if err := server.Call(avahiServerIface+".GetVersionString", 0).Store(&versionStr); err == nil { |
| 61 | + return versionStr |
| 62 | + } |
| 63 | + |
| 64 | + // Try GetAPIVersion (returns a single uint32) |
| 65 | + var apiVersion uint32 |
| 66 | + if err := server.Call(avahiServerIface+".GetAPIVersion", 0).Store(&apiVersion); err == nil { |
| 67 | + return fmt.Sprintf("API v%d", apiVersion) |
| 68 | + } |
| 69 | + |
| 70 | + return "unknown" |
| 71 | +} |
| 72 | + |
| 73 | +// Version returns the avahi-daemon version string. |
| 74 | +func (a *AvahiRegistrar) Version() string { |
| 75 | + return a.version |
| 76 | +} |
| 77 | + |
| 78 | +// Register publishes the service via avahi-daemon. |
| 79 | +func (a *AvahiRegistrar) Register(name, serviceType, domain string, port int, txt []string) error { |
| 80 | + server := a.conn.Object(avahiService, avahiServerPath) |
| 81 | + |
| 82 | + // Create a new entry group for our service |
| 83 | + var groupPath dbus.ObjectPath |
| 84 | + err := server.Call(avahiServerIface+".EntryGroupNew", 0).Store(&groupPath) |
| 85 | + if err != nil { |
| 86 | + return fmt.Errorf("failed to create entry group: %w", err) |
| 87 | + } |
| 88 | + |
| 89 | + a.entryGroup = a.conn.Object(avahiService, groupPath) |
| 90 | + |
| 91 | + // Convert TXT records to [][]byte format required by avahi |
| 92 | + txtBytes := make([][]byte, len(txt)) |
| 93 | + for i, t := range txt { |
| 94 | + txtBytes[i] = []byte(t) |
| 95 | + } |
| 96 | + |
| 97 | + // AddService signature: iiussssqaay |
| 98 | + // interface (i): network interface index, -1 for all |
| 99 | + // protocol (i): IP protocol, -1 for both IPv4/IPv6 |
| 100 | + // flags (u): publish flags, 0 for default |
| 101 | + // name (s): service instance name |
| 102 | + // type (s): service type (e.g., "_spotify-connect._tcp") |
| 103 | + // domain (s): domain to publish in (e.g., "local") |
| 104 | + // host (s): hostname, empty for default |
| 105 | + // port (q): port number (uint16) |
| 106 | + // txt (aay): TXT record data as array of byte arrays |
| 107 | + err = a.entryGroup.Call(avahiEntryGroupIface+".AddService", 0, |
| 108 | + avahiIfUnspec, // interface |
| 109 | + avahiProtoUnspec, // protocol |
| 110 | + uint32(0), // flags |
| 111 | + name, // service name |
| 112 | + serviceType, // service type |
| 113 | + domain, // domain |
| 114 | + "", // host (empty = use default hostname) |
| 115 | + uint16(port), // port |
| 116 | + txtBytes, // TXT records |
| 117 | + ).Err |
| 118 | + if err != nil { |
| 119 | + return fmt.Errorf("failed to add service: %w", err) |
| 120 | + } |
| 121 | + |
| 122 | + // Commit the entry group to publish the service |
| 123 | + err = a.entryGroup.Call(avahiEntryGroupIface+".Commit", 0).Err |
| 124 | + if err != nil { |
| 125 | + return fmt.Errorf("failed to commit entry group: %w", err) |
| 126 | + } |
| 127 | + |
| 128 | + return nil |
| 129 | +} |
| 130 | + |
| 131 | +// Shutdown removes the service from avahi and releases resources. |
| 132 | +func (a *AvahiRegistrar) Shutdown() { |
| 133 | + if a.entryGroup != nil { |
| 134 | + // Free the entry group (this also unpublishes the service) |
| 135 | + _ = a.entryGroup.Call(avahiEntryGroupIface+".Free", 0).Err |
| 136 | + a.entryGroup = nil |
| 137 | + } |
| 138 | + if a.conn != nil { |
| 139 | + _ = a.conn.Close() |
| 140 | + a.conn = nil |
| 141 | + } |
| 142 | +} |
0 commit comments