Report version and auto-update state to Hammerhead and update on request

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

blacktip.go

@@ -38,6 +38,13 @@ type Config struct {
 	DataDir    string
 	Docker     bool // report local Docker containers for discovery
 
+	// Version is the release this binary was built from, reported to Hammerhead. AutoUpdate says
+	// whether the program may update itself; only then does it act on an update request from
+	// Hammerhead, by calling UpdateNow (which normally restarts the process into the new binary).
+	Version    string
+	AutoUpdate bool
+	UpdateNow  func(ctx context.Context) (newVersion string, err error)
+
 	// Traefik, when its Path is set, serves http/https resources instead of the built-in proxy.
 	Traefik TraefikConfig
 
@@ -106,6 +113,9 @@ type Blacktip struct {
 
 	logq       chan model.LogEntry
 	reportMu   sync.Mutex
+	updating   atomic.Bool
+	updateMsg  string // outcome of the update Hammerhead asked for, reported back
+	updateID   string // the request that updateMsg answers
 	dockerMu   sync.Mutex
 	dockerAt   time.Time
 	dockerList []model.Container
@@ -252,6 +262,9 @@ func (b *Blacktip) apply(cfg *model.EdgeConfig) {
 	if b.dashboard == "" {
 		b.dashboard = b.cfg.Hammerhead
 	}
+	if cfg.UpdateID != "" {
+		b.requestUpdate(cfg.UpdateID)
+	}
 	b.local = map[string]bool{}
 	for _, id := range cfg.Local {
 		b.local[id] = true
@@ -517,8 +530,10 @@ func (b *Blacktip) report() {
 		IPs: localIPs(), PublicKey: b.wgPub,
 		Status: map[string]model.MappingStatus{}, Stats: map[string]model.Stat{},
 		Containers: b.containers(), MailChecks: map[string]model.MailCheck{},
+		Version: b.cfg.Version, AutoUpdate: b.cfg.AutoUpdate,
 	}
 	b.mu.Lock()
+	rep.UpdateMsg, rep.UpdateID = b.updateMsg, b.updateID
 	for id, chk := range b.mailChecks {
 		rep.MailChecks[id] = chk
 	}
@@ -736,3 +751,38 @@ func (ms *mapState) dialOff(proto string, prefer, off int) (net.Conn, bool, erro
 	}
 	return nil, false, last
 }
+
+// requestUpdate acts on "update now" from Hammerhead (id identifies the request). It only ever installs
+// what this machine's own auto-update would (the newest release from its configured server), and only
+// when auto-update is on. Caller holds b.mu.
+func (b *Blacktip) requestUpdate(id string) {
+	if id == b.updateID {
+		return // already handled, or in progress
+	}
+	b.updateID, b.updateMsg = id, ""
+	if !b.cfg.AutoUpdate || b.cfg.UpdateNow == nil {
+		b.updateMsg = "auto-update is off on this machine (set BLACKTIP_AUTO_UPDATE=1 and restart it)"
+		go b.report()
+		return
+	}
+	if !b.updating.CompareAndSwap(false, true) {
+		b.updateMsg = "another update is already running"
+		go b.report()
+		return
+	}
+	go func() {
+		defer b.updating.Store(false)
+		tag, err := b.cfg.UpdateNow(b.ctx) // on success this restarts the process and does not return
+		b.mu.Lock()
+		switch {
+		case err != nil:
+			b.updateMsg = "update failed: " + err.Error()
+		case tag == "":
+			b.updateMsg = "already on the newest release"
+		default:
+			b.updateMsg = "updated to " + tag + ", restarting"
+		}
+		b.mu.Unlock()
+		b.report()
+	}()
+}