Fixes from the audit: input checks, apply order, sign-in limits

- The server endpoint must be a plain host name or IP address. It is
  written into client configs as is, so a newline could add lines such
  as PreUp, which wg-quick runs as root on the client.
- Listen addresses and the session length (1–720 hours) are checked.
  Before web settings or a restore are saved, the server tries the new
  listen addresses and certificate files, so a value it cannot start
  with is refused instead of stopping the service at the next restart.
- Kernel applies run one at a time and read the config once it is
  their turn, so an older config can no longer be applied last.
- Pending passkey sign-ins are capped: 10 per address, 1000 in total.
- Behind a local proxy, the last X-Forwarded-For entry is the client;
  earlier ones come from the client and are ignored.
- With LAN access off, peers are also kept from the IPv6 networks on
  the uplink, not only from its private IPv4 networks.
- A change that leaves no user with a password is refused, and so is a
  backup without one or from a newer version.

README.md

@@ -27,16 +27,24 @@ dependencies on the server: the binary installs, updates and removes itself.
 - **IPv4 and IPv6:** IPv6 inside the tunnel is turned on automatically when the
   server has a global IPv6 address.
 - **Traffic history:** kept in `stats.json`, hourly for 48 h and daily for
-  400 days by default (Settings → Data retention).
+  400 days by default (Settings → Logs & history).
+- **Live view:** the speed of every peer right now, updated every 2 seconds,
+  with the last 2 minutes as a chart. Kept in memory only.
 - **Connection history:** every online session per peer, with start, duration,
   address and traffic. A new session starts when a device changes networks.
   Country and network operator come from the free
   [DB-IP Lite](https://db-ip.com) databases (CC BY 4.0). GHOSTWIRE downloads
   them monthly (about 20 MB) and looks addresses up locally, so peer addresses
-  never leave the server. You can switch this off under Settings → Data
-  retention.
+  never leave the server. You can switch this off under Settings → Logs &
+  history.
 - **Logs:** written to `GHOSTWIRE.jsonl`, rotated at 10 MB with 5 old files
-  kept by default. Changes are marked as audit entries.
+  kept by default, and shown on the Log page. Changes are marked as audit
+  entries.
+- **Update notice:** once a day the server asks Gitea or GitHub (your choice
+  under Settings → Updates) for the latest release. A newer one shows in the
+  sidebar, on the Dashboard and in Settings, with its release notes and the
+  commands to update this server. Nothing about the server is sent; the check
+  can be switched off.
 - **HTTPS built in:** Let's Encrypt, a self-signed certificate, your own
   certificate files, or plain HTTP behind a reverse proxy.
 
@@ -176,7 +184,7 @@ the running service.
 | Command | What it does |
 |---|---|
 | `GHOSTWIRE install [-domain d] [-email e] [-endpoint h] [-port p] [-y]` | Sets up and starts the service, as above. Asks for the settings no flag gave; `-y` never asks. |
-| `GHOSTWIRE update [-force]` | Run from the new binary, e.g. `sudo /tmp/GHOSTWIRE update`. Checks that it can read the current `config.json` (nothing changes if not), backs up the config to `config.json.bak-<old version>`, replaces the binary, updates the unit if needed and restarts. If the new version does not stay up, the old binary and config are put back and restarted. It refuses older versions without `-force`. |
+| `GHOSTWIRE update [-force]` | Run from the new binary, e.g. `sudo /tmp/GHOSTWIRE update`. Checks that it can read the current `config.json` (nothing changes if not), backs up the config to `config.json.bak-<old version>` (keeping the newest 3 such copies), replaces the binary, updates the unit if needed and restarts. If the new version does not stay up, the old binary and config are put back and restarted. It refuses older versions without `-force`. |
 | `GHOSTWIRE uninstall [-purge] [-y]` | Stops and removes the service, `wg0` and the firewall table. `-purge` also deletes `/opt/ghostwire` and the user. |
 | `GHOSTWIRE passwd [username]` | Sets a user's password (default: the first user) and reloads the running service. The way back in if you are locked out. |
 | `GHOSTWIRE version` | Prints the version. |
@@ -218,6 +226,7 @@ After editing `config.json` by hand, run `sudo systemctl reload ghostwire`.
 |---|---|
 | `GHOSTWIRE` | the program |
 | `config.json` | all settings, server key, peers, pending setup links with their PINs, user password hashes, authenticator app secrets, passkeys, recovery code and token hashes (0600) |
+| `config.json.bak-*` | copies of `config.json` made by `update`; the newest 3 are kept, and Settings → Upkeep lists and removes them |
 | `stats.json` | traffic and connection history per peer |
 | `geo-country.mmdb`, `geo-asn.mmdb` | DB-IP Lite databases for country and network lookups |
 | `GHOSTWIRE.jsonl` | log, one JSON object per line. Changes carry `"audit":true` |
@@ -257,6 +266,8 @@ signed in: GET /auth/mfa · POST /auth/mfa/totp/setup · /auth/mfa/totp/confirm
 signed in: POST /auth/mfa/keys/begin · /auth/mfa/keys/finish?name= · PATCH|DELETE /auth/mfa/keys/{id}
 signed in: POST /auth/mfa/recovery-codes
 GET    /status                           GET /stats?range=24h|7d|30d|90d
+GET    /live?since=                      (speed per peer, last 2 minutes in 2-second steps)
+GET    /live/stream                      (the same as server-sent events)
 GET    /server         PATCH /server     POST /server/rotate-key     GET /server/detect-ip
 GET    /peers          POST /peers       (returns the config and QR once)
 GET    /peers/{id}     PATCH /peers/{id} DELETE /peers/{id}
@@ -264,9 +275,10 @@ POST   /peers/{id}/enable | /disable | /issue-config
 GET    /peers/{id}/stats?range=…        GET /peers/{id}/sessions?limit=100
 GET    /peers/{id}/latency               (24 h, one point per 5 minutes)
 GET    /peers/{id}/setup (not read-only) DELETE /peers/{id}/setup
-GET    /settings       PATCH /settings   POST /restart
+GET    /settings       PATCH /settings   POST /restart   POST /updates/check
 GET    /logs?level=&limit=&audit=1       GET /logs/download
 signed in: GET|POST /tokens · DELETE /tokens/{id} · GET /backup · POST /restore
+signed in: GET|DELETE /update-backups · DELETE /update-backups/{name}   (config copies made by update)
 public: GET /setup/{token} · POST /setup/{token} {"pin"}   (what a setup link opens)
 ```
 
@@ -275,9 +287,22 @@ public: GET /setup/{token} · POST /setup/{token} {"pin"}   (what a setup link o
 setup link (`setup.url`, `setup.pin`, `setup.qr`) instead of a config. With a
 link, the peer's current keys keep working until the link is opened.
 
+`GET /settings` includes `updates`: the running and latest version,
+`available`, the release notes and the download links for this server's
+platform. `PATCH /settings` `{"updates": {"source": "gitea"|"github",
+"check": false}}` picks the source or switches the daily check off;
+`POST /updates/check` checks now. `GET /auth/me` has `updateAvailable` with
+the newer version while there is one.
+
 Traffic is reported from the peer's point of view: `down` is what the peer
 downloaded, `up` is what it uploaded.
 
+`GET /live` answers `{"step": 2, "size": 60, "points": [{"t": …, "peers":
+{"<id>": [down, up]}}]}` with speeds in bits per second, kept only in memory.
+With `since` (unix seconds) it returns only newer steps. `GET /live/stream`
+sends the same messages as server-sent events: the history first, then one
+message per new step.
+
 Latency is measured by pinging the peer's tunnel address every 30 seconds. Set
 it per peer with `PATCH /peers/{id}` `{"latencyCheck": "off"|"active"|"always"}`
 (default `off`). `active` pings only while the device sends traffic, so idle
@@ -303,6 +328,9 @@ Settings → Pair iOS app: scan the QR code, or tap "Copy pairing code" and past
 it into the app's "Enter manually". Self-signed certificates are pinned during
 pairing.
 
+The iOS app is currently in beta testing. For an invite, email
+[engineroom@redetzke.aero](mailto:engineroom@redetzke.aero).
+
 ## Development
 
 On macOS (or any non-Linux system), `make dev` starts the app on

api.go

@@ -3,15 +3,18 @@ package main
 import (
 	"cmp"
 	"context"
+	"crypto/tls"
 	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
 	"log/slog"
+	"net"
 	"net/http"
 	"net/netip"
 	"slices"
 	"strings"
+	"syscall"
 	"time"
 )
 
@@ -21,13 +24,16 @@ type App struct {
 	kernel   Kernel
 	recon    *Reconciler
 	stats    *Stats
+	speeds   *Speeds // nil in tests
 	auth     *Auth
 	tls      *webTLS
 	logPath  string
 	logw     *rotatingWriter // nil in tests
 	geo      *Geo            // nil in tests
+	updates  *Updater        // nil in tests
 	started  time.Time
 	shutdown func()   // graceful stop; systemd restarts the service
+	webAddrs []string // the addresses the web server listens on now
 }
 
 // --- helpers ---
@@ -143,6 +149,8 @@ func (a *App) routes() http.Handler {
 
 	g("GET /api/v1/status", a.status)
 	g("GET /api/v1/stats", a.allStats)
+	g("GET /api/v1/live", a.liveSpeeds)
+	g("GET /api/v1/live/stream", a.liveStream)
 
 	g("GET /api/v1/server", a.getServer)
 	g("PATCH /api/v1/server", a.patchServer)
@@ -173,6 +181,7 @@ func (a *App) routes() http.Handler {
 	// need a signed-in user.
 	g("GET /api/v1/settings", a.getSettings)
 	g("PATCH /api/v1/settings", a.patchSettings)
+	g("POST /api/v1/updates/check", a.checkUpdates)
 	g("POST /api/v1/restart", a.restart)
 	adm("GET /api/v1/tokens", a.listTokens)
 	adm("POST /api/v1/tokens", a.createToken)
@@ -181,6 +190,9 @@ func (a *App) routes() http.Handler {
 	g("GET /api/v1/logs/download", a.downloadLog)
 	adm("GET /api/v1/backup", a.backup)
 	adm("POST /api/v1/restore", a.restore)
+	adm("GET /api/v1/update-backups", a.listUpdateBackups)
+	adm("DELETE /api/v1/update-backups", a.removeUpdateBackups)
+	adm("DELETE /api/v1/update-backups/{name}", a.removeUpdateBackup)
 
 	mux.HandleFunc("/api/", func(w http.ResponseWriter, r *http.Request) {
 		writeJSON(w, http.StatusNotFound, map[string]string{"error": "no such endpoint"})
@@ -258,6 +270,9 @@ func (a *App) me(w http.ResponseWriter, r *http.Request) {
 		"id": p.UserID, "name": p.Name, "isAdmin": p.IsAdmin, "scope": p.Scope,
 		"mustChangePassword": p.MustChangePassword, "mfaSetupRequired": p.MFASetupRequired, "version": version, "session": p.Session,
 	}
+	if v := a.updates.Available(); v != "" {
+		out["updateAvailable"] = v
+	}
 	if _, u := a.store.Get().userByID(p.UserID); u != nil {
 		out["username"], out["note"], out["created"] = u.Username, u.Note, u.Created
 	}
@@ -342,7 +357,7 @@ func (a *App) status(w http.ResponseWriter, r *http.Request) {
 	d30, u30 := sumPoints(a.stats.series(nil, "30d"))
 	checks := a.kernel.Checks(cfg)
 	last, applyErr := a.recon.Status()
-	ac := Check{Name: "Last apply", OK: applyErr == nil, Detail: "applied " + last.Format(time.RFC3339)}
+	ac := Check{Name: "Kernel in sync", OK: applyErr == nil, Detail: "applied " + last.Format(time.RFC3339)}
 	if applyErr != nil {
 		ac.Detail = applyErr.Error()
 	}
@@ -390,6 +405,60 @@ func (a *App) allStats(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, map[string]any{"range": rng, "points": a.stats.series(nil, rng)})
 }
 
+// liveSpeeds returns each peer's speed over the last 2 minutes; with since
+// (unix seconds) only the newer steps.
+func (a *App) liveSpeeds(w http.ResponseWriter, r *http.Request) {
+	var since int64
+	fmt.Sscan(r.URL.Query().Get("since"), &since)
+	points := []SpeedPoint{}
+	if a.speeds != nil {
+		points = a.speeds.Since(since)
+	}
+	writeJSON(w, http.StatusOK, map[string]any{"step": int(speedStep / time.Second), "size": speedPoints, "points": points})
+}
+
+// liveStream sends the same data as server-sent events: the current points
+// first, then each new step as soon as it is sampled. The session is checked
+// again with every step, so signing out ends the stream.
+func (a *App) liveStream(w http.ResponseWriter, r *http.Request) {
+	if a.speeds == nil {
+		writeJSON(w, http.StatusServiceUnavailable, map[string]string{"error": "live speeds are not available"})
+		return
+	}
+	rc := http.NewResponseController(w)
+	_ = rc.SetWriteDeadline(time.Time{}) // the server's write timeout would cut the stream
+	w.Header().Set("Content-Type", "text/event-stream")
+	w.Header().Set("Cache-Control", "no-store")
+	w.Header().Set("X-Accel-Buffering", "no") // nginx: do not buffer
+	points, ch, cancel := a.speeds.Subscribe()
+	defer cancel()
+	send := func(points []SpeedPoint) bool {
+		b, _ := json.Marshal(map[string]any{"step": int(speedStep / time.Second), "size": speedPoints, "points": points})
+		if _, err := fmt.Fprintf(w, "data: %s\n\n", b); err != nil {
+			return false
+		}
+		return rc.Flush() == nil
+	}
+	if !send(points) {
+		return
+	}
+	for {
+		select {
+		case <-r.Context().Done():
+			return
+		case <-a.speeds.Done():
+			return
+		case pt := <-ch:
+			if _, ok := a.auth.Authenticate(r); !ok {
+				return
+			}
+			if !send([]SpeedPoint{pt}) {
+				return
+			}
+		}
+	}
+}
+
 func (a *App) peerStats(w http.ResponseWriter, r *http.Request) {
 	cfg := a.store.Get()
 	if _, p := cfg.peerByID(r.PathValue("id")); p == nil {
@@ -999,6 +1068,7 @@ func (a *App) getSettings(w http.ResponseWriter, r *http.Request) {
 		"decoy":       cfg.Decoy,
 		"signin":      cfg.SignIn,
 		"geo":         a.geoStatus(),
+		"updates":     a.updates.Status(),
 		"fingerprint": a.tls.Fingerprint(),
 		"logPath":     a.logPath,
 	})
@@ -1016,12 +1086,23 @@ func (a *App) patchSettings(w http.ResponseWriter, r *http.Request) {
 	}
 	var restart bool
 	err = a.store.Update(func(c *Config) error {
-		before, _ := json.Marshal(c.Web)
+		// Session length applies to the next sign-in; everything else in
+		// web needs a restart.
+		listen := func() string {
+			w := c.Web
+			w.SessionHours = 0
+			b, _ := json.Marshal(w)
+			return string(b)
+		}
+		before, oldWeb := listen(), c.Web
 		if err := field(m, "web", &c.Web); err != nil {
 			return err
 		}
-		after, _ := json.Marshal(c.Web)
-		restart = string(before) != string(after)
+		if restart = listen() != before; restart {
+			if err := a.checkWebStart(oldWeb, c.Web); err != nil {
+				return err
+			}
+		}
 		if err := field(m, "stats", &c.Stats); err != nil {
 			return err
 		}
@@ -1031,6 +1112,9 @@ func (a *App) patchSettings(w http.ResponseWriter, r *http.Request) {
 		if err := field(m, "signin", &c.SignIn); err != nil {
 			return err
 		}
+		if err := field(m, "updates", &c.Updates); err != nil {
+			return err
+		}
 		return field(m, "log", &c.Log)
 	})
 	if err != nil {
@@ -1160,7 +1244,20 @@ func (a *App) restore(w http.ResponseWriter, r *http.Request) {
 		writeErr(w, badRequest("this file has no server key; is it a backup of this app?"))
 		return
 	}
-	if err := a.store.Update(func(c *Config) error { *c = in; return nil }); err != nil {
+	if in.Version > configVersion {
+		writeErr(w, badRequest("this backup is from a newer version of %s; update this server first", appName))
+		return
+	}
+	in.applyDefaults()
+	if !in.passwordSet() {
+		writeErr(w, badRequest("this backup has no user with a password; restoring it would lock everyone out"))
+		return
+	}
+	if err := a.store.Update(func(c *Config) error {
+		old := c.Web
+		*c = in
+		return a.checkWebStart(old, c.Web)
+	}); err != nil {
 		writeErr(w, err)
 		return
 	}
@@ -1168,6 +1265,55 @@ func (a *App) restore(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, map[string]any{"ok": true, "applyError": a.apply(), "restartRequired": true})
 }
 
+// checkWebStart refuses web settings the service could not start with: an
+// address it cannot listen on, or certificate files it cannot read. The
+// service would stop at the next restart, and the web interface and the API
+// with it.
+func (a *App) checkWebStart(old, next WebConfig) error {
+	if err := validateListen(next.Listen, "listen address", false); err != nil {
+		return &userError{err.Error()}
+	}
+	if err := validateListen(next.HTTPListen, "HTTP listen address", true); err != nil {
+		return &userError{err.Error()}
+	}
+	if next.TLS.Mode == "files" && next.TLS != old.TLS {
+		if _, err := tls.LoadX509KeyPair(next.TLS.CertFile, next.TLS.KeyFile); err != nil {
+			return badRequest("the certificate files cannot be used: %v", err)
+		}
+	}
+	addrs := []string{next.Listen}
+	if next.HTTPListen != "" && next.TLS.Mode != "off" {
+		addrs = append(addrs, next.HTTPListen)
+	}
+	for _, addr := range addrs {
+		if err := a.canListen(addr); err != nil {
+			return badRequest("cannot listen on %s: %v", addr, err)
+		}
+	}
+	return nil
+}
+
+// canListen tries to listen on addr. An address the service listens on now,
+// or one whose port it holds, is fine: it is free again after the restart.
+func (a *App) canListen(addr string) error {
+	if slices.Contains(a.webAddrs, addr) {
+		return nil
+	}
+	ln, err := net.Listen("tcp", addr)
+	if err == nil {
+		return ln.Close()
+	}
+	if errors.Is(err, syscall.EADDRINUSE) {
+		_, port, _ := net.SplitHostPort(addr)
+		for _, own := range a.webAddrs {
+			if _, p, _ := net.SplitHostPort(own); p == port {
+				return nil
+			}
+		}
+	}
+	return err
+}
+
 // applyRuntime applies the settings that take effect without a restart: log
 // level and log rotation. Traffic retention is read by the stats sampler.
 func (a *App) applyRuntime(c *Config) {
@@ -1176,6 +1322,17 @@ func (a *App) applyRuntime(c *Config) {
 		a.logw.SetLimits(c.Log.MaxSizeMB, c.Log.MaxFiles)
 	}
 	a.geo.SetEnabled(c.Stats.geoEnabled())
+	a.updates.Set(c.Updates)
+}
+
+// checkUpdates asks the release source now and returns what it found.
+func (a *App) checkUpdates(w http.ResponseWriter, r *http.Request) {
+	if a.updates == nil || !a.updates.Status().Enabled {
+		writeErr(w, badRequest("the update check is switched off"))
+		return
+	}
+	a.updates.Check(r.Context())
+	writeJSON(w, http.StatusOK, a.updates.Status())
 }
 
 func (a *App) geoStatus() GeoStatus {

app.css

@@ -33,8 +33,20 @@
 * { box-sizing: border-box; }
 html, body { margin: 0; }
 body { background: var(--ground); color: var(--ink); font-family: var(--sans); font-size: 14px; line-height: 1.45; }
-a { color: var(--link); }
-a:hover { color: var(--link-hover); }
+a { color: var(--link); text-decoration-color: rgba(28, 92, 171, .35); text-underline-offset: 3px; }
+a:hover { color: var(--link-hover); text-decoration-color: currentColor; }
+/* Links to another page (go, back) are ink with an arrow that nudges on
+   hover; outside links (ext) keep the link colour and get ↗. */
+a.go, a.back { color: var(--ink); font-size: 13px; font-weight: 500; text-decoration: none; white-space: nowrap; }
+a.go:hover, a.back:hover { color: var(--link); }
+a.go .ar { margin-left: 4px; }
+a.back .ar { margin-right: 4px; }
+a.ext .ar { margin-left: 2px; font-size: .8em; }
+.ar { display: inline-block; transition: transform .15s; }
+a.go:hover .ar { transform: translateX(3px); }
+a.back:hover .ar { transform: translateX(-3px); }
+a.ext:hover .ar { transform: translate(2px, -2px); }
+@media (prefers-reduced-motion: reduce) { .ar { transition: none; } }
 :focus-visible { outline: 2px solid var(--focus); outline-offset: 1px; }
 [hidden] { display: none !important; }
 .mono { font-family: var(--mono); font-size: 13px; }
@@ -69,7 +81,10 @@ a.brand, a.brand:hover { color: #fff; text-decoration: none; }
 .side .acct strong { font-size: 14px; font-weight: 500; color: #fff; overflow: hidden; text-overflow: ellipsis; }
 .side .acct span span { color: #a9aaa5; }
 .side .avatar { width: 28px; height: 28px; border-radius: 50%; background: #3a3b41; display: grid; place-items: center; flex: none; font-size: 13px; font-weight: 600; color: #fff; }
-.side .footrow { display: flex; justify-content: space-between; padding: 10px 12px 0; }
+.side .footrow { display: flex; justify-content: space-between; align-items: center; gap: 8px; padding: 10px 12px 0; }
+.side .footrow .upd { font-size: 11.5px; font-weight: 500; color: #cfe2f8; background: #1f3550; border: 1px solid #2d4a6e; padding: 2px 8px; border-radius: 999px; text-decoration: none; white-space: nowrap; }
+.side .footrow .upd:hover { color: #fff; }
+.side .nav .pip { margin-left: auto; width: 7px; height: 7px; border-radius: 50%; background: #6aa6ea; }
 .main { flex: 999 1 560px; min-width: 0; padding: 32px 32px 56px; }
 /* Beside the page (not stacked above it on a phone), the sidebar stays in
    place while the page scrolls, so the account link is always visible. */
@@ -83,7 +98,7 @@ a.brand, a.brand:hover { color: #fff; text-decoration: none; }
 .titleline { display: flex; flex-wrap: wrap; align-items: center; gap: 12px; }
 h1 { margin: 0; font-size: 26px; font-weight: 600; letter-spacing: -0.01em; overflow-wrap: anywhere; }
 .sub { margin: 4px 0 0; color: var(--ink-2); }
-.back { font-size: 13px; margin-bottom: -8px; }
+.back { margin-bottom: -8px; align-self: flex-start; }
 
 /* cards */
 .card { background: var(--surface); border: 1px solid var(--line); border-radius: 12px; padding: 20px; min-width: 0; }
@@ -129,6 +144,9 @@ h1 { margin: 0; font-size: 26px; font-weight: 600; letter-spacing: -0.01em; over
 .tag { display: inline-block; font-size: 11px; font-weight: 600; padding: 2px 8px; border-radius: 999px; background: var(--warn-bg); color: var(--warn-ink); margin-left: 6px; vertical-align: 1px; }
 .notice { display: flex; gap: 10px; align-items: flex-start; padding: 12px 14px; border-radius: 10px; background: var(--warn-bg); color: var(--warn-ink); font-size: 13px; }
 .notice.err { background: #fbefee; color: var(--bad-ink); }
+.notice.new { background: #e8f0fa; color: #174d8f; flex-wrap: wrap; align-items: center; }
+.notice.new .actions { margin-left: auto; }
+.btn.ghost { background: transparent; border-color: transparent; }
 .notice .btn { margin-left: auto; }
 
 /* tables */
@@ -145,7 +163,7 @@ tr:last-child td { border-bottom: 0; }
 .num { text-align: right; font-variant-numeric: tabular-nums; white-space: nowrap; }
 td .note { font-size: 12px; color: var(--ink-3); }
 a.pname { color: var(--ink); font-weight: 600; text-decoration: none; }
-a.pname:hover, a.pname:focus-visible { color: var(--ink); text-decoration: underline; text-underline-offset: 3px; }
+a.pname:hover { color: var(--link); }
 .empty { padding: 24px 12px; margin: 0; text-align: center; color: var(--ink-3); }
 
 /* forms */
@@ -173,28 +191,50 @@ fieldset { border: 0; margin: 0; padding: 0; min-width: 0; display: flex; flex-d
 .kv dt { color: var(--ink-2); }
 .kv dd { margin: 0; min-width: 0; overflow-wrap: anywhere; }
 
-/* health: public addresses, then one tile per check */
+/* health: public addresses on the left, one row per check on the right */
+.hcbody { display: grid; grid-template-columns: minmax(0, 5fr) minmax(0, 7fr); gap: 12px; margin-top: 16px; }
 .hchead { display: flex; align-items: baseline; gap: 12px; flex-wrap: wrap; }
 .hchead > span { font-size: 13px; color: var(--ink-2); }
 .hchead > span.bad { color: var(--bad-ink); font-weight: 500; }
-.hcaddrs { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 12px; margin-top: 16px; }
-.hcaddr { background: var(--ground); border-radius: 10px; padding: 14px 16px; min-width: 0; }
+.hcaddrs { display: flex; flex-direction: column; gap: 12px; }
+.hcaddr { flex: 1; display: flex; flex-direction: column; justify-content: center; background: var(--ground); border-radius: 10px; padding: 14px 18px; min-width: 0; }
 .hcaddr .l { display: flex; align-items: center; gap: 8px; font-size: 12px; color: var(--ink-2); }
 .hcaddr .v { margin-top: 4px; font-size: 15px; font-weight: 500; overflow-wrap: anywhere; }
-.hcaddr .v.mono { font-size: 20px; }
+.hcaddr .v.mono { font-size: 22px; }
 .hcaddr .n { font-family: var(--sans); font-size: 12px; font-weight: 400; color: var(--ink-2); }
 .hcaddr.bad { background: #fdf6f5; box-shadow: inset 0 0 0 1px #e6b3b0; }
 .hcaddr.bad .v { color: var(--bad-ink); }
-.hctiles { display: grid; grid-template-columns: repeat(auto-fill, minmax(190px, 1fr)); gap: 12px; margin-top: 12px; }
-.hctile { border: 1px solid var(--line); border-radius: 10px; padding: 12px 14px; display: flex; flex-direction: column; gap: 4px; min-width: 0; }
-.hctile .l { display: flex; align-items: center; gap: 8px; font-size: 12px; color: var(--ink-2); }
-.hctile .l > span:first-child { flex: 1; min-width: 0; }
-.hctile .s { font-size: 15px; font-weight: 500; }
-.hctile .r { font-size: 11.5px; color: var(--ink-3); overflow-wrap: anywhere; }
-.hctile .p { font-size: 12.5px; color: var(--bad-ink); overflow-wrap: anywhere; }
-.hctile.bad { border-color: #e6b3b0; background: #fdf6f5; }
-.hctile.bad .s { color: var(--bad-ink); }
-@media (max-width: 640px) { .hctiles { grid-template-columns: repeat(2, minmax(0, 1fr)); } }
+.hclist { border: 1px solid var(--line); border-radius: 10px; min-width: 0; }
+.hcrow { display: grid; grid-template-columns: 8px minmax(0, 190px) minmax(0, 1fr); gap: 2px 14px; align-items: baseline; padding: 11px 16px; border-top: 1px solid var(--line-2); }
+.hcrow:first-child { border-top: 0; }
+.hcrow > .dot { align-self: center; }
+.hcrow .l { font-size: 13px; color: var(--ink-2); }
+.hcrow .v { display: flex; flex-wrap: wrap; align-items: baseline; gap: 2px 10px; min-width: 0; }
+.hcrow .s { font-weight: 500; }
+.hcrow .r { font-size: 12px; color: var(--ink-3); overflow-wrap: anywhere; }
+.hcrow .p { grid-column: 2 / -1; font-size: 12.5px; color: var(--bad-ink); overflow-wrap: anywhere; }
+.hcrow.bad { background: #fdf6f5; }
+.hcrow.bad .s { color: var(--bad-ink); }
+@media (max-width: 1000px) { .hcbody { grid-template-columns: minmax(0, 1fr); } }
+@media (max-width: 640px) { .hcrow { grid-template-columns: 8px minmax(0, 1fr); } .hcrow .v { grid-column: 2; } }
+
+/* updates */
+.upvers { display: grid; grid-template-columns: repeat(auto-fit, minmax(180px, 1fr)); gap: 12px; margin-top: 14px; }
+.upbox { background: var(--ground); border-radius: 10px; padding: 12px 14px; display: flex; flex-direction: column; gap: 2px; min-width: 0; }
+.upbox > span { font-size: 12px; color: var(--ink-2); }
+.upbox strong { font-size: 15px; font-weight: 500; }
+.upbox strong.mono { font-size: 16px; }
+.upbox.new { background: #e8f0fa; box-shadow: inset 0 0 0 1px #bcd2ee; }
+.upbox.new strong { color: #174d8f; }
+.uptodate { display: flex; align-items: center; gap: 10px; margin: 14px 0 0; font-weight: 500; }
+.upnotes { border: 1px solid var(--line); border-radius: 10px; padding: 14px 16px; margin-top: 14px; display: flex; flex-direction: column; gap: 10px; font-size: 13px; }
+.upnotes p { margin: 0; max-width: 80ch; }
+.upnotes ul { margin: 0; padding-left: 18px; display: flex; flex-direction: column; gap: 6px; max-width: 80ch; }
+.upnotes .hd, .upcmd .hd { display: flex; align-items: baseline; gap: 10px; flex-wrap: wrap; }
+.upnotes .hd a { margin-left: auto; }
+.upcmd { display: flex; flex-direction: column; gap: 8px; margin-top: 14px; }
+.uprow { display: flex; justify-content: space-between; align-items: center; gap: 12px; flex-wrap: wrap; margin-top: 16px; padding-top: 14px; border-top: 1px solid var(--line-2); }
+#updates > .notice { margin-top: 14px; }
 
 /* activity */
 .ev { display: flex; gap: 12px; padding: 10px 0; border-bottom: 1px solid var(--line-2); font-size: 13px; }
@@ -226,7 +266,10 @@ fieldset { border: 0; margin: 0; padding: 0; min-width: 0; display: flex; flex-d
 .chart .grp span.up { background: var(--up); }
 .chart .grp span.total { background: var(--down); }
 .chart .grp.on span.total { background: var(--down-strong); }
-.xaxis { display: flex; justify-content: space-between; margin: 8px 0 0 56px; font-size: 11px; color: var(--axis-ink); }
+.xaxis { position: relative; height: 22px; margin-left: 56px; font-size: 11px; color: var(--axis-ink); }
+.xaxis span { position: absolute; top: 0; padding-top: 7px; transform: translateX(-50%); white-space: nowrap; font-variant-numeric: tabular-nums; }
+.xaxis span.edge::before { content: ''; position: absolute; left: 50%; top: 0; height: 4px; border-left: 1px solid var(--axis); }
+@media (max-width: 640px) { .xaxis span.minor { display: none; } }
 .chart.loading { opacity: .5; }
 .chart .plot { position: absolute; left: 56px; right: 0; top: 0; bottom: 1px; }
 .chart .plot svg { width: 100%; height: 100%; display: block; overflow: visible; }
@@ -303,8 +346,8 @@ dialog::backdrop { background: rgba(22, 23, 26, .55); }
 .setupbox { width: 100%; max-width: 400px; display: flex; flex-direction: column; gap: 24px; margin: auto 0; }
 .setupbox h1 { font-size: 22px; }
 .setupbox p { margin: 0; color: #c9c9c3; }
-.setupbox a { color: #9cc3f5; }
-.setupbox a:hover { color: #fff; }
+.setupbox a { color: #9cc3f5; text-decoration-color: rgba(156, 195, 245, .4); }
+.setupbox a:hover { color: #fff; text-decoration-color: currentColor; }
 .setupbox .center, .setupbox.center { text-align: center; display: flex; flex-direction: column; align-items: center; gap: 8px; }
 .setupbox.center { gap: 20px; }
 .setupbox .ghost { opacity: .45; }
@@ -342,3 +385,36 @@ dialog::backdrop { background: rgba(22, 23, 26, .55); }
 .mfarow .grow { flex: 1; min-width: 0; }
 .dlg .secret { font-size: 15px; letter-spacing: 0.04em; overflow-wrap: anywhere; }
 .dlg .codes { columns: 2; font-size: 15px; line-height: 1.8; }
+
+/* settings groups; the log page */
+.group { margin-top: 20px; display: flex; flex-direction: column; gap: 2px; }
+.group h2 { margin: 0; font-size: 19px; font-weight: 600; }
+.group p { margin: 0; font-size: 13px; color: var(--ink-2); }
+.card h3 { margin: 0; font-size: 16px; font-weight: 600; }
+.saves { font-size: 12px; color: var(--ink-3); }
+pre.log.tall { max-height: calc(100vh - 260px); min-height: 420px; }
+
+/* live */
+.livenow { display: grid; grid-template-columns: repeat(auto-fill, minmax(190px, 1fr)); gap: 12px 24px; margin-top: 14px; }
+.livenow .k { font-size: 13px; color: var(--ink-2); }
+.livenow .v { font-size: 30px; font-weight: 600; letter-spacing: -0.01em; margin-top: 4px; font-variant-numeric: tabular-nums; }
+.livenow .v small { font-size: 16px; color: var(--ink-3); font-weight: 500; margin-left: 6px; }
+.chart .larea { opacity: .15; }
+.chart .larea.down { fill: var(--down); }
+.chart .larea.up { fill: var(--up); }
+.chart .ldown, .chart .lup { fill: none; stroke-width: 1.75; stroke-linejoin: round; stroke-linecap: round; vector-effect: non-scaling-stroke; }
+.chart .ldown { stroke: var(--down); }
+.chart .lup { stroke: var(--up); }
+.chart .plot.live svg { overflow: hidden; }
+.xaxis.lx span:first-child { transform: none; }
+.xaxis.lx span:last-child { transform: translateX(-100%); }
+.spark.wide { width: 96px; }
+.spark .fill { fill: var(--down); opacity: .15; stroke: none; }
+tr.idle td { color: var(--ink-3); }
+tr.idle .spark polyline { stroke: var(--ink-3); }
+tr.idle .spark .fill { fill: var(--ink-3); }
+td .mono, td.num .mono { font-variant-numeric: tabular-nums; }
+.livesub { display: flex; align-items: center; gap: 6px; }
+.dot.pulse { animation: pulse 2s ease-in-out infinite; }
+@keyframes pulse { 50% { opacity: .35; } }
+@media (prefers-reduced-motion: reduce) { .dot.pulse { animation: none; } }

app.js

@@ -47,8 +47,10 @@
     peers: '<circle cx="9" cy="8" r="3.5"/><path d="M2.5 20c.8-3.5 3.4-5.5 6.5-5.5s5.7 2 6.5 5.5"/><path d="M16 4.8a3.5 3.5 0 0 1 0 6.4M18.5 14.8c1.5.8 2.6 2.6 3 5.2"/>',
     server: '<rect x="3" y="4" width="18" height="7" rx="1.5"/><rect x="3" y="13" width="18" height="7" rx="1.5"/><path d="M7 7.5h.01M7 16.5h.01"/>',
     settings: '<path d="M4 6h10M18 6h2M4 12h4M12 12h8M4 18h12"/><circle cx="16" cy="6" r="2"/><circle cx="10" cy="12" r="2"/><circle cx="18" cy="18" r="2"/>',
+    live: '<path d="M3 12h4l3-7 4 14 3-7h4"/>',
     plus: '<path d="M12 5v14M5 12h14"/>',
     key: '<circle cx="8" cy="15" r="4"/><path d="M11 12l9-9M17 6l3 3M14 9l2 2"/>',
+    log: '<rect x="4" y="3" width="16" height="18" rx="2"/><path d="M8 8h8M8 12h8M8 16h5"/>',
     logout: '<path d="M14 4h4a2 2 0 0 1 2 2v12a2 2 0 0 1-2 2h-4"/><path d="M10 16l-4-4 4-4M6 12h10"/>',
   };
 
@@ -167,6 +169,14 @@
 
   const badge = (st) => h('span', { class: 'badge' }, h('span', { class: st.dot }), st.label);
 
+  // go links to another page of the app; back returns to one. Their arrows
+  // nudge on hover. ext opens an outside page in a new tab, marked with ↗.
+  const arrow = (c) => h('span', { class: 'ar', 'aria-hidden': 'true' }, c);
+  const go = (href, text) => h('a', { class: 'go', href }, text, arrow('→'));
+  const back = (href, text) => h('a', { class: 'back', href }, arrow('←'), text);
+  const ext = (href, text) => h('a', { class: 'ext', href, target: '_blank', rel: 'noopener' }, text, arrow('↗'), h('span', { class: 'sr' }, ' (opens in a new tab)'));
+  const peerLink = (p) => h('a', { class: 'pname', href: '#/peers/' + p.id }, p.name);
+
   // svg builds an SVG element; attrs are set as attributes.
   function svg(tag, attrs, ...kids) {
     const el = document.createElementNS('http://www.w3.org/2000/svg', tag);
@@ -383,8 +393,8 @@
   function pointLabel(t, range) {
     const d = new Date(t * 1000);
     if (range === '24h') {
-      const hrs = Math.round((Date.now() - d.getTime()) / 3600000);
-      return hrs <= 0 ? 'This hour' : hrs + ' h ago';
+      const hm = (x) => x.toLocaleTimeString(undefined, { hour: '2-digit', minute: '2-digit' });
+      return hm(d) + '–' + hm(new Date(d.getTime() + 3600000));
     }
     return d.toLocaleDateString(undefined, { weekday: 'short', day: 'numeric', month: 'short' });
   }
@@ -429,9 +439,35 @@
         h('div', { class: 'gl top' }), h('div', { class: 'gl mid' }), h('div', { class: 'gl base' }),
         h('div', { class: 'yl top' }, fmtBytes(top)), h('div', { class: 'yl mid' }, fmtBytes(top / 2)),
         bars),
-      h('div', { class: 'xaxis' },
-        h('span', null, pointLabel(points[0].t, range)),
-        h('span', null, range === '24h' ? 'now' : pointLabel(points[points.length - 1].t, range))));
+      timeAxis(points.map((p) => p.t), range === '24h' ? 3600 : 86400));
+  }
+
+  // timeAxis labels the bottom of a chart with clock times or dates. Points
+  // are evenly spaced buckets of step seconds. Hourly buckets get the hour
+  // they start at, every 3 hours (6 on narrow screens), with the date at
+  // midnight; daily buckets get the date under the bar, every bar for a
+  // week and every 7th bar, counted back from today, for a month.
+  function timeAxis(ts, step) {
+    const n = ts.length;
+    const ticks = [];
+    if (step < 86400) {
+      for (let i = 0; i < n; i++) {
+        const d = new Date(ts[i] * 1000);
+        if (d.getMinutes() !== 0 || d.getHours() % 3 !== 0 || i === 0) continue;
+        const text = d.getHours() === 0
+          ? d.toLocaleDateString(undefined, { weekday: 'short', day: 'numeric' })
+          : d.toLocaleTimeString(undefined, { hour: '2-digit', minute: '2-digit' });
+        ticks.push({ at: i / n, text, minor: d.getHours() % 6 !== 0, edge: true });
+      }
+    } else {
+      const every = n > 10 ? 7 : 1;
+      for (let i = n - 1; i >= 0; i -= every) {
+        const d = new Date(ts[i] * 1000);
+        ticks.push({ at: (i + 0.5) / n, text: d.toLocaleDateString(undefined, n > 10 ? { day: 'numeric', month: 'short' } : { weekday: 'short', day: 'numeric' }) });
+      }
+    }
+    return h('div', { class: 'xaxis', 'aria-hidden': 'true' },
+      ticks.map((k) => h('span', { class: (k.minor ? 'minor' : '') + (k.edge ? ' edge' : ''), style: { left: (k.at * 100).toFixed(3) + '%' } }, k.text)));
   }
 
   // latencyChart draws the median as a line over a min–max band, one point
@@ -488,7 +524,7 @@
         h('div', { class: 'gl top' }), h('div', { class: 'gl mid' }), h('div', { class: 'gl base' }),
         h('div', { class: 'yl top' }, fmtMs(top)), h('div', { class: 'yl mid' }, fmtMs(top / 2)),
         wrapEl),
-      h('div', { class: 'xaxis' }, h('span', null, '24 h ago'), h('span', null, '12 h ago'), h('span', null, 'now')));
+      timeAxis(points.map((p) => p.t), 300));
   }
 
   // pairDialog creates an API token and shows it once, with the pairing QR
@@ -528,9 +564,9 @@
 
   // ---------- shell, router ----------
 
-  const NAV = [['#/', 'dashboard', 'Dashboard'], ['#/peers', 'peers', 'Peers'], ['#/server', 'server', 'Server'], ['#/settings', 'settings', 'Settings']];
+  const NAV = [['#/', 'dashboard', 'Dashboard'], ['#/live', 'live', 'Live'], ['#/peers', 'peers', 'Peers'], ['#/server', 'server', 'Server'], ['#/log', 'log', 'Log'], ['#/settings', 'settings', 'Settings']];
   let navLinks = {};
-  let srvBox, peerCount;
+  let srvBox, peerCount, verRow;
 
   function buildShell() {
     srvBox = h('div', { class: 'srv' }, h('span', { class: 'dot' }), h('span', null, 'Loading…'));
@@ -546,13 +582,25 @@
             h('span', { class: 'avatar', 'aria-hidden': 'true' }, me.name.slice(0, 1).toUpperCase()),
             h('span', null, h('strong', null, me.name), h('span', null, 'My account')))),
           h('button', { type: 'button', class: 'signout', 'aria-label': 'Sign out', onClick: logout }, icon('logout'), h('span', { class: 'tip', 'aria-hidden': 'true' }, 'Sign out'))),
-        h('div', { class: 'footrow' },
-          h('span', null, 'v' + me.version.replace(/^v/, '')))));
+        (verRow = h('div', { class: 'footrow' }))));
     main = h('main', { class: 'main', id: 'main' });
     app.replaceChildren(h('div', { class: 'shell' }, nav, main));
+    drawUpdateHint();
     refreshSide();
   }
 
+  // drawUpdateHint shows a newer release next to the version in the sidebar
+  // and as a dot on Settings.
+  function drawUpdateHint() {
+    if (!verRow) return;
+    const v = me.updateAvailable;
+    fill(verRow, h('span', null, 'v' + me.version.replace(/^v/, '')),
+      v ? h('a', { class: 'upd', href: '#/settings#updates' }, v + ' available') : null);
+    const set = navLinks['#/settings'];
+    set.querySelectorAll('.pip, .sr').forEach((e) => e.remove());
+    if (v) set.append(h('span', { class: 'pip', title: 'Update available' }), h('span', { class: 'sr' }, ', update available'));
+  }
+
   async function refreshSide() {
     try {
       const s = await api('GET', '/status');
@@ -578,11 +626,13 @@
 
   const ROUTES = [
     [/^#\/?$/, '#/', viewDashboard],
+    [/^#\/live$/, '#/live', viewLive],
     [/^#\/peers$/, '#/peers', viewPeers],
     [/^#\/peers\/new$/, '#/peers', viewPeerNew],
     [/^#\/peers\/([\w-]+)$/, '#/peers', viewPeer],
     [/^#\/server$/, '#/server', viewServer],
-    [/^#\/settings$/, '#/settings', viewSettings],
+    [/^#\/log$/, '#/log', viewLog],
+    [/^#\/settings(#\w+)?$/, '#/settings', viewSettings],
     [/^#\/account$/, '#/account', viewAccount],
   ];
 
@@ -980,18 +1030,35 @@
 
   // ---------- dashboard ----------
 
+  // RANGES are the time ranges offered above the traffic charts.
+  const RANGES = [['24h', '24 h'], ['7d', '7 days'], ['30d', '30 days']];
+
   async function viewDashboard(wrap) {
+    let range = '24h';
     const draw = async () => {
       const [st, pl, stats, logs] = await Promise.all([
         api('GET', '/status'),
         api('GET', '/peers'),
-        api('GET', '/stats?range=24h'),
+        api('GET', '/stats?range=' + range),
         me.isAdmin ? api('GET', '/logs?audit=1&limit=6').catch(() => null) : null,
       ]);
       const peers = pl.peers;
       const failing = st.checks.filter((c) => !c.ok);
       const ifCheck = st.checks.find((c) => c.name === 'WireGuard interface');
       const top = [...peers].sort((a, b) => (b.stats.down24h + b.stats.up24h) - (a.stats.down24h + a.stats.up24h)).slice(0, 6);
+      // A range switch fetches and redraws only the chart.
+      const traffic = h('div', null, chart(stats.points, range, 'total', true));
+      const pills = h('div', { class: 'pills', role: 'group', 'aria-label': 'Time range' });
+      const drawPills = () => pills.replaceChildren(...RANGES.map(([k, t]) =>
+        h('button', { type: 'button', class: range === k ? 'pill on' : 'pill', 'aria-pressed': String(range === k), onClick: async () => {
+          range = k;
+          drawPills();
+          try {
+            const s = await api('GET', '/stats?range=' + k);
+            if (range === k) traffic.replaceChildren(chart(s.points, k, 'total', true));
+          } catch (x) { toast(x.message, true); }
+        } }, t)));
+      drawPills();
 
       fill(wrap,
         h('div', { class: 'head' },
@@ -1005,6 +1072,8 @@
           h('div', null, h('strong', null, 'Needs attention: '), failing.map((c) => c.name + ' (' + c.detail + ')').join(' · ')),
           h('a', { class: 'btn small', href: '#/server' }, 'Health')) : null,
 
+        updateBanner(),
+
         h('div', { class: 'tiles' },
           h('div', { class: 'card tile' }, h('div', { class: 'k' }, 'Peers online'),
             h('div', { class: 'v' }, String(st.peers.online), h('small', null, '/ ' + st.peers.total)),
@@ -1020,22 +1089,22 @@
             h('div', { class: 's' }, 'Service up ' + ago(st.started).replace(' ago', '') + ' · ' + (st.healthy ? 'all checks pass' : failing.length + ' check(s) failing')))),
 
         h('section', { class: 'card', 'aria-labelledby': 'tput' },
-          h('div', { class: 'cardhead' }, h('h2', { id: 'tput' }, 'Traffic, all peers · last 24 hours')),
-          chart(stats.points, '24h', 'total', true)),
+          h('div', { class: 'cardhead' }, h('h2', { id: 'tput' }, 'Traffic, all peers'), pills),
+          traffic),
 
         h('div', { class: 'cols' },
           h('section', { class: 'card flush' },
-            h('div', { class: 'cardhead' }, h('h2', null, 'Peers'), h('a', { href: '#/peers' }, 'All peers')),
+            h('div', { class: 'cardhead' }, h('h2', null, 'Peers'), go('#/peers', 'All peers')),
             top.length ? h('div', { class: 'tbl' }, h('table', { class: 'narrow' },
               h('thead', null, h('tr', null, h('th', null, 'Name'), h('th', null, 'Status'), h('th', { class: 'num' }, 'Download, 24 h'), h('th', { class: 'num' }, 'Upload, 24 h'))),
               h('tbody', null, top.map((p) => h('tr', null,
-                h('td', null, h('a', { href: '#/peers/' + p.id }, p.name)),
+                h('td', null, peerLink(p)),
                 h('td', null, badge(peerState(p))),
                 h('td', { class: 'num' }, fmtBytes(p.stats.down24h)),
                 h('td', { class: 'num' }, fmtBytes(p.stats.up24h)))))))
-              : h('p', { class: 'empty' }, 'No peers yet. ', h('a', { href: '#/peers/new' }, 'Add the first one'))),
+              : h('p', { class: 'empty' }, 'No peers yet. ', go('#/peers/new', 'Add the first one'))),
           logs ? h('section', { class: 'card' },
-            h('div', { class: 'cardhead' }, h('h2', null, 'Recent activity'), h('a', { href: '#/settings' }, 'Log')),
+            h('div', { class: 'cardhead' }, h('h2', null, 'Recent activity'), go('#/log', 'Log')),
             logs.lines.length
               ? h('div', null, logs.lines.map((l) => h('div', { class: 'ev' }, h('time', { datetime: l.time }, fmtWhen(l.time)), h('span', null, describeAudit(l)))))
               : h('p', { class: 'empty' }, 'No changes yet.')) : null));
@@ -1044,6 +1113,245 @@
     every(30000, () => draw().catch(() => {}));
   }
 
+  // ---------- live ----------
+
+  // fmtRate formats a speed in bits per second, with one decimal from
+  // kbit/s up so the figures keep their shape as they change.
+  function fmtRate(bps) {
+    const u = ['bit/s', 'kbit/s', 'Mbit/s', 'Gbit/s'];
+    let i = 0, v = bps;
+    while (v >= 1000 && i < u.length - 1) { v /= 1000; i++; }
+    return (i === 0 ? String(Math.round(v)) : v.toFixed(1)) + ' ' + u[i];
+  }
+
+  // curvePath draws a smooth line through the points (monotone cubic): it
+  // never dips below zero or rises above a peak between two steps.
+  function curvePath(xy) {
+    const n = xy.length;
+    if (n < 3) return 'M' + xy.map(([x, y]) => x.toFixed(1) + ',' + y.toFixed(2)).join('L');
+    const d = [], m = [];
+    for (let i = 0; i < n - 1; i++) d.push((xy[i + 1][1] - xy[i][1]) / (xy[i + 1][0] - xy[i][0]));
+    m[0] = d[0];
+    m[n - 1] = d[n - 2];
+    for (let i = 1; i < n - 1; i++) m[i] = d[i - 1] * d[i] <= 0 ? 0 : (d[i - 1] + d[i]) / 2;
+    for (let i = 0; i < n - 1; i++) {
+      if (d[i] === 0) { m[i] = m[i + 1] = 0; continue; }
+      const a = m[i] / d[i], b = m[i + 1] / d[i], q = a * a + b * b;
+      if (q > 9) { const t = 3 / Math.sqrt(q); m[i] = t * a * d[i]; m[i + 1] = t * b * d[i]; }
+    }
+    let p = 'M' + xy[0][0].toFixed(1) + ',' + xy[0][1].toFixed(2);
+    for (let i = 0; i < n - 1; i++) {
+      const [x0, y0] = xy[i], [x1, y1] = xy[i + 1], k = (x1 - x0) / 3;
+      p += 'C' + (x0 + k).toFixed(1) + ',' + (y0 + m[i] * k).toFixed(2) + ' ' + (x1 - k).toFixed(1) + ',' + (y1 - m[i + 1] * k).toFixed(2) + ' ' + x1.toFixed(1) + ',' + y1.toFixed(2);
+    }
+    return p;
+  }
+
+  // Below this a peer counts as idle: keepalives and background chatter.
+  const IDLE_BPS = 2000;
+
+  // The figures and the table average the last few steps so they do not
+  // swing with every burst; the charts show each step.
+  const AVG_STEPS = 5;
+
+  const calm = () => window.matchMedia('(prefers-reduced-motion: reduce)').matches;
+
+  // liveChart draws download and upload as lines over light, see-through
+  // areas, so neither looks less important where they overlap. It is
+  // built once and updated in place: each new step enters just beyond the
+  // right edge and the chart slides left by one step over the step's length,
+  // so it moves steadily instead of jumping. Hover shows the values at a
+  // moment.
+  function liveChart() {
+    const W = 1000, H = 100;
+    let pts = [], size = 60, step = 2, off = 0, dx = W / 59, t0 = 0, moving = false;
+    const downArea = svg('path', { class: 'larea down' });
+    const upArea = svg('path', { class: 'larea up' });
+    const down = svg('path', { class: 'ldown' });
+    const up = svg('path', { class: 'lup' });
+    const cursor = svg('line', { class: 'cursor', x1: 0, x2: 0, y1: 0, y2: H, visibility: 'hidden' });
+    const g = svg('g', null, downArea, upArea, down, up, cursor);
+    const plot = svg('svg', { viewBox: '0 0 ' + W + ' ' + H, preserveAspectRatio: 'none', 'aria-hidden': 'true' }, g);
+    const ylTop = h('div', { class: 'yl top' }), ylMid = h('div', { class: 'yl mid' });
+    const at = (p) => new Date(p.t * 1000).toLocaleTimeString(undefined, { hour: '2-digit', minute: '2-digit', second: '2-digit' });
+    const idle = () => {
+      const peak = pts.reduce((m, p) => p.down + p.up > m.down + m.up ? p : m, { down: 0, up: 0 });
+      return peak.t
+        ? ['Peak ', h('strong', null, fmtRate(peak.down + peak.up)), ' at ' + at(peak) + ' · hover the chart to see a moment.']
+        : ['No traffic in the last 2 minutes.'];
+    };
+    const readout = h('div', { class: 'readout' });
+    let hoverT = null;
+    const x = (i) => off + i * dx;
+    const show = (i) => {
+      const p = pts[i];
+      hoverT = p.t;
+      cursor.setAttribute('x1', x(i).toFixed(1)); cursor.setAttribute('x2', x(i).toFixed(1)); cursor.setAttribute('visibility', 'visible');
+      readout.replaceChildren(at(p), ' · Download ', h('strong', null, fmtRate(p.down)), ' · Upload ', h('strong', null, fmtRate(p.up)));
+    };
+    const plotEl = h('div', { class: 'plot live', role: 'img', 'aria-label': 'Speed of all peers over the last 2 minutes',
+      onMousemove: (e) => {
+        if (!pts.length) return;
+        const r = plotEl.getBoundingClientRect();
+        const shift = moving ? Math.min(1, (performance.now() - t0) / (step * 1000)) * dx : 0;
+        const xv = (e.clientX - r.left) / r.width * W + shift;
+        show(Math.max(0, Math.min(pts.length - 1, Math.round((xv - off) / dx))));
+      },
+      onMouseleave: () => { hoverT = null; cursor.setAttribute('visibility', 'hidden'); readout.replaceChildren(...idle()); } }, plot);
+    const el = h('div', null,
+      readout,
+      h('div', { class: 'chart small' },
+        h('div', { class: 'gl top' }), h('div', { class: 'gl mid' }), h('div', { class: 'gl base' }),
+        ylTop, ylMid, plotEl),
+      h('div', { class: 'xaxis lx' }, h('span', { style: { left: '0%' } }, '2 min ago'), h('span', { style: { left: '50%' } }, '1 min ago'), h('span', { style: { left: '100%' } }, 'now')));
+
+    // update draws points; slide is true for a new step arriving live.
+    const update = (points, sz, st, slide) => {
+      pts = points; size = sz; step = st; dx = W / (size - 1);
+      moving = slide && !calm();
+      const n = pts.length;
+      // The newest point sits at the right edge, or one step beyond it
+      // while sliding in.
+      off = W - (n - 1) * dx + (moving ? dx : 0);
+      const top = niceTop(Math.max(0, ...pts.map((p) => Math.max(p.down, p.up))) || 1e6);
+      const line = (k) => curvePath(pts.map((p, i) => [x(i), H - p[k] / top * H]));
+      if (n > 1) {
+        const dl = line('down'), ul = line('up');
+        const base = 'L' + x(n - 1).toFixed(1) + ',' + H + 'L' + x(0).toFixed(1) + ',' + H + 'Z';
+        downArea.setAttribute('d', dl + base);
+        upArea.setAttribute('d', ul + base);
+        down.setAttribute('d', dl);
+        up.setAttribute('d', ul);
+      }
+      // Axis values are round: no ".0".
+      ylTop.textContent = fmtRate(top).replace('.0 ', ' ');
+      ylMid.textContent = fmtRate(top / 2).replace('.0 ', ' ');
+      g.style.transition = 'none';
+      g.style.transform = 'translateX(0)';
+      if (moving) {
+        g.getBoundingClientRect(); // start the slide from 0
+        t0 = performance.now();
+        g.style.transition = 'transform ' + step + 's linear';
+        g.style.transform = 'translateX(' + (-dx).toFixed(2) + 'px)';
+      }
+      const i = hoverT == null ? -1 : pts.findIndex((p) => p.t === hoverT);
+      if (i >= 0) show(i);
+      else { hoverT = null; cursor.setAttribute('visibility', 'hidden'); readout.replaceChildren(...idle()); }
+    };
+    return { el, update };
+  }
+
+  // rateSpark draws a peer's total speed over the same window, scaled to its
+  // own peak.
+  function rateSpark(vals) {
+    const s = svg('svg', { class: 'spark wide', viewBox: '0 0 96 18', preserveAspectRatio: 'none', 'aria-hidden': 'true' });
+    const top = Math.max(...vals, IDLE_BPS * 4);
+    const n = vals.length;
+    if (n < 2) return s;
+    const pts = vals.map((v, i) => (i / (n - 1) * 96).toFixed(1) + ',' + (17 - v / top * 15).toFixed(1));
+    s.append(svg('polygon', { class: 'fill', points: '0,18 ' + pts.join(' ') + ' 96,18' }), svg('polyline', { points: pts.join(' ') }));
+    return s;
+  }
+
+  // viewLive shows the speed of every peer right now. The server streams its
+  // short in-memory history (the last 2 minutes in 2-second steps) and then
+  // each new step as it is sampled.
+  async function viewLive(wrap) {
+    let peers = (await api('GET', '/peers')).peers;
+    let live = { step: 2, size: 60, points: [] };
+    let paused = false, es = null, retry = 0;
+    const down = h('div', { class: 'v' }), up = h('div', { class: 'v' }), active = h('div', { class: 'v' });
+    const totals = h('div', { class: 'livenow' },
+      h('div', null, h('div', { class: 'k' }, h('span', { class: 'key down' }), 'Download'), down),
+      h('div', null, h('div', { class: 'k' }, h('span', { class: 'key up' }), 'Upload'), up),
+      h('div', null, h('div', { class: 'k' }, 'Active peers'), active));
+    const lc = liveChart();
+    const rows = h('div');
+    const pauseBtn = h('button', { type: 'button', class: 'btn', onClick: () => {
+      paused = !paused;
+      pauseBtn.textContent = paused ? 'Resume' : 'Pause';
+      sub.replaceChildren(...subText());
+      if (paused) close(); else open();
+    } }, 'Pause');
+    const subText = () => paused
+      ? ['Paused · the chart keeps the moment you paused']
+      : [h('span', { class: 'dot ok pulse' }), ' Updated every ' + live.step + ' s · figures are ' + AVG_STEPS * live.step + '-second averages'];
+    const sub = h('p', { class: 'sub livesub' }, subText());
+
+    const draw = (slide) => {
+      const pts = live.points;
+      const sumAt = (p) => Object.values(p.peers).reduce((a, [d, u]) => ({ down: a.down + d, up: a.up + u }), { down: 0, up: 0 });
+      const series = pts.map((p) => ({ t: p.t, ...sumAt(p) }));
+      const recent = pts.slice(-AVG_STEPS);
+      const avg = (f) => recent.length ? recent.reduce((a, p) => a + f(p), 0) / recent.length : 0;
+      const last = {};
+      for (const p of peers) last[p.id] = [avg((x) => (x.peers[p.id] || [0, 0])[0]), avg((x) => (x.peers[p.id] || [0, 0])[1])];
+      down.textContent = fmtRate(avg((p) => sumAt(p).down));
+      up.textContent = fmtRate(avg((p) => sumAt(p).up));
+      active.replaceChildren(String(peers.filter((p) => { const r = last[p.id]; return r && r[0] + r[1] >= IDLE_BPS; }).length),
+        h('small', null, '/ ' + peers.filter((p) => p.stats.online).length + ' online'));
+      lc.update(series, live.size, live.step, slide);
+
+      const online = peers.filter((p) => p.stats.online)
+        .map((p) => ({ p, r: last[p.id] || [0, 0], hist: pts.map((x) => { const v = x.peers[p.id]; return v ? v[0] + v[1] : 0; }) }))
+        .sort((a, b) => (b.r[0] + b.r[1]) - (a.r[0] + a.r[1]) || a.p.name.localeCompare(b.p.name));
+      const rate = (v, idle) => idle ? h('span', { class: 'muted' }, '–') : h('span', { class: 'mono' }, fmtRate(v));
+      rows.replaceChildren(
+        online.length ? h('div', { class: 'tbl' }, h('table', { class: 'narrow' },
+          h('thead', null, h('tr', null, h('th', null, 'Peer'), h('th', null, 'Last 2 minutes'), h('th', { class: 'num' }, 'Download'), h('th', { class: 'num' }, 'Upload'), h('th', null, 'Endpoint'))),
+          h('tbody', null, online.map(({ p, r, hist }) => {
+            const idle = r[0] + r[1] < IDLE_BPS;
+            return h('tr', { class: idle ? 'idle' : null },
+              h('td', null, peerLink(p), idle ? h('span', { class: 'tag plain' }, 'idle') : null),
+              h('td', null, rateSpark(hist)),
+              h('td', { class: 'num' }, rate(r[0], idle)),
+              h('td', { class: 'num' }, rate(r[1], idle)),
+              h('td', null, h('span', { class: 'mono' }, p.stats.endpoint ? p.stats.endpoint.replace(/:\d+$/, '') : '–'),
+                p.stats.location && p.stats.location.country ? h('span', { class: 'cc', title: fmtLocation(p.stats.location) }, p.stats.location.country) : null));
+          })))) : h('p', { class: 'empty' }, 'No peer is online.'));
+    };
+
+    // The first message of a stream is the whole history; later ones carry
+    // one new step each. One step more than the server keeps is held, so
+    // the chart's left edge stays filled while it slides.
+    function open() {
+      if (es || paused || document.hidden || !wrap.isConnected) return;
+      let first = true;
+      es = new EventSource('/api/v1/live/stream');
+      es.onmessage = (e) => {
+        retry = 0;
+        const m = JSON.parse(e.data);
+        live = { step: m.step, size: m.size, points: first ? m.points : live.points.concat(m.points).slice(-m.size - 1) };
+        draw(!first);
+        first = false;
+      };
+      es.onerror = () => {
+        if (es.readyState !== EventSource.CLOSED) { first = true; return; } // the browser reconnects
+        close();
+        // Refused, e.g. signed out: api() shows the sign-in page on 401.
+        api('GET', '/status').then(() => { if (wrap.isConnected) setTimeout(open, Math.min(30000, 2000 * 2 ** retry++)); }).catch(() => {});
+      };
+    }
+    function close() { if (es) { es.close(); es = null; } }
+    const onVis = () => { if (document.hidden) close(); else open(); };
+    document.addEventListener('visibilitychange', onVis);
+    cleanups.push(() => { close(); document.removeEventListener('visibilitychange', onVis); });
+
+    fill(wrap,
+      h('div', { class: 'head' },
+        h('div', null, h('h1', null, 'Live'), sub),
+        h('div', { class: 'actions' }, pauseBtn)),
+      h('section', { class: 'card', 'aria-labelledby': 'lv' },
+        h('div', { class: 'cardhead' }, h('h2', { id: 'lv' }, 'All peers · right now')),
+        totals, lc.el),
+      h('section', { class: 'card flush', 'aria-labelledby': 'lp' },
+        h('div', { class: 'cardhead' }, h('h2', { id: 'lp' }, 'Peers'), h('span', { class: 'hint' }, 'Busiest first')),
+        rows));
+    draw(false);
+    open();
+    every(15000, async () => { try { peers = (await api('GET', '/peers')).peers; } catch { /* keep last */ } });
+  }
+
   function describeAudit(l) {
     const parts = [l.msg.charAt(0).toUpperCase() + l.msg.slice(1)];
     if (l.peer) parts.push(': ' + l.peer);
@@ -1124,7 +1432,7 @@
         return hit && keep;
       });
       tbody.replaceChildren(...sorted(rows).map((p) => h('tr', null,
-        h('td', null, h('a', { class: 'pname', href: '#/peers/' + p.id }, p.name), p.note ? h('div', { class: 'note' }, p.note) : null),
+        h('td', null, peerLink(p), p.note ? h('div', { class: 'note' }, p.note) : null),
         h('td', { class: 'mono' }, p.ipv4),
         h('td', null, badge(peerState(p))),
         h('td', { class: 'mono muted' }, p.stats.endpoint || '–',
@@ -1279,7 +1587,7 @@
     drawPreview();
 
     fill(wrap,
-      h('a', { class: 'back', href: '#/peers' }, '← Peers'),
+      back('#/peers', 'Peers'),
       h('div', null, h('h1', null, 'Add peer'), h('p', { class: 'sub' }, 'Assigns the next free address and adds the peer to ' + srv.interface + ' without a restart.')),
       h('div', { class: 'split' }, form,
         h('aside', { class: 'card aside', 'aria-labelledby': 'pv' },
@@ -1311,7 +1619,7 @@
       sessMore.textContent = allSessions ? 'Show fewer' : 'Show all ' + sessions.length;
     };
     drawSessions();
-    let range = '7d';
+    let range = '24h';
     const st = peerState(p);
     const traffic = h('div');
     const totals = h('div', { class: 'legend-row' });
@@ -1333,7 +1641,7 @@
     };
 
     async function drawTraffic() {
-      pills.replaceChildren(...[['24h', '24 h'], ['7d', '7 days'], ['30d', '30 days']].map(([k, t]) =>
+      pills.replaceChildren(...RANGES.map(([k, t]) =>
         h('button', { type: 'button', class: range === k ? 'pill on' : 'pill', 'aria-pressed': String(range === k), onClick: () => { range = k; drawTraffic(); } }, t)));
       const s = await api('GET', '/peers/' + id + '/stats?range=' + range);
       const down = s.points.reduce((a, x) => a + x.down, 0), up = s.points.reduce((a, x) => a + x.up, 0);
@@ -1436,7 +1744,7 @@
     };
 
     fill(wrap,
-      h('a', { class: 'back', href: '#/peers' }, '← Peers'),
+      back('#/peers', 'Peers'),
       h('div', { class: 'head' },
         h('div', null,
           h('div', { class: 'titleline' }, h('h1', null, p.name), badge(st.key === 'online' ? { ...st, label: 'Online · handshake ' + ago(p.stats.lastHandshake) } : st)),
@@ -1487,7 +1795,7 @@
           : h('p', { class: 'empty' }, 'No connections recorded yet.'),
         sessions.length > SHORT ? h('div', { style: { margin: '8px 12px 0' } }, sessMore) : null,
         h('p', { class: 'hint', style: { margin: '4px 12px 12px' } }, 'Country and network: ',
-          h('a', { href: 'https://db-ip.com', target: '_blank', rel: 'noopener' }, 'IP Geolocation by DB-IP'),
+          ext('https://db-ip.com', 'IP Geolocation by DB-IP'),
           '. Kept as long as the daily traffic history.')),
 
       h('form', { class: 'card', onSubmit: save },
@@ -1511,9 +1819,9 @@
   const DNS_PRESETS = [['Quad9', '9.9.9.9, 149.112.112.112']];
 
   // healthParts turns the server's checks into the Health card: the public
-  // address per IP family (from its uplink and public address checks), then
-  // one tile per other check with a plain-word status, the raw setting and,
-  // when it fails, what is wrong.
+  // address per IP family (from its uplink and public address checks) and,
+  // beside them, one row per other check with a plain-word status, the raw
+  // setting and, when it fails, what is wrong.
   function healthParts(checks) {
     const by = Object.fromEntries(checks.map((c) => [c.name, c]));
     const addrs = [];
@@ -1547,8 +1855,8 @@
           t.status = c.ok ? 'Present' : 'Missing';
           if (/^table /.test(c.detail)) { t.raw = c.detail.replace(/ (present|missing)$/, ''); t.problem = null; }
           break;
-        case 'Last apply':
-          if (c.ok) { const iso = c.detail.replace(/^applied /, ''); t.status = ago(iso); t.title = fmtStamp(iso); } else t.status = 'Failed';
+        case 'Kernel in sync':
+          if (c.ok) { const iso = c.detail.replace(/^applied /, ''); t.status = ago(iso); t.title = fmtStamp(iso); } else t.status = 'Out of sync';
           break;
         case 'Latency check': t.status = c.ok ? 'Tunnel ping works' : 'Failing'; break;
       }
@@ -1563,14 +1871,14 @@
     return h('section', { class: 'card', 'aria-labelledby': 'hc' },
       h('div', { class: 'hchead' }, h('h2', { id: 'hc' }, 'Health'),
         h('span', { class: hp.failing ? 'bad' : null }, hp.failing ? hp.failing + ' of ' + hp.total + ' checks failing' : 'All ' + hp.total + ' checks pass')),
+      h('div', { class: 'hcbody' },
       hp.addrs.length ? h('div', { class: 'hcaddrs' }, hp.addrs.map((a) => h('div', { class: a.ok ? 'hcaddr' : 'hcaddr bad' },
         h('div', { class: 'l' }, dot(a.ok), a.label),
         h('div', { class: a.mono ? 'v mono' : 'v' }, a.value, a.note ? h('span', { class: 'n' }, ' ' + a.note) : null)))) : null,
-      h('div', { class: 'hctiles' }, hp.tiles.map((t) => h('div', { class: t.ok ? 'hctile' : 'hctile bad', title: t.title || null },
-        h('div', { class: 'l' }, h('span', null, t.label), dot(t.ok)),
-        h('div', { class: 's' }, t.status),
-        t.raw ? h('div', { class: 'r mono' }, t.raw) : null,
-        t.problem ? h('div', { class: 'p' }, t.problem) : null))));
+      h('div', { class: 'hclist' }, hp.tiles.map((t) => h('div', { class: t.ok ? 'hcrow' : 'hcrow bad', title: t.title || null },
+        dot(t.ok), h('span', { class: 'l' }, t.label),
+        h('span', { class: 'v' }, h('span', { class: 's' }, t.status), t.raw ? h('span', { class: 'r mono' }, t.raw) : null),
+        t.problem ? h('div', { class: 'p' }, t.problem) : null)))));
   }
 
   async function viewServer(wrap) {
@@ -1680,7 +1988,7 @@
           fieldEl('up6', 'IPv6 uplink interface', h('input', { id: 'up6', class: 'mono', value: draft.uplinkV6, placeholder: 'auto: ' + (srv.detectedUplinkV6 || 'none found'), onInput: str('uplinkV6') })),
           cb('nat', 'Masquerade (NAT) peer traffic to the internet'),
           cb('peerToPeer', 'Allow peers to reach each other'),
-          cb('lanAccess', 'Allow peers to reach the server\'s LAN', 'Private networks on the uplink interface'),
+          cb('lanAccess', 'Allow peers to reach the server\'s LAN', 'Private IPv4 and the IPv6 networks on the uplink interface'),
           cb('openPort', 'Accept UDP ' + draft.listenPort + ' in the input chain'))),
 
       h('section', { class: 'card', 'aria-labelledby': 'ky' },
@@ -1693,6 +2001,155 @@
       bar);
   }
 
+  // ---------- log ----------
+
+  async function viewLog(wrap) {
+    const s = await api('GET', '/settings');
+    let level = 'all';
+    const box = h('pre', { class: 'log tall', tabindex: '0', 'aria-label': 'Log lines, newest first' });
+    const pills = h('div', { class: 'pills', role: 'group', 'aria-label': 'Level filter' });
+    let audit = false;
+    const draw = async () => {
+      pills.replaceChildren(...[['all', 'All'], ['info', 'Info'], ['warn', 'Warn'], ['error', 'Error']].map(([k, t]) =>
+        h('button', { type: 'button', class: level === k && !audit ? 'pill on' : 'pill', 'aria-pressed': String(level === k && !audit), onClick: () => { level = k; audit = false; draw(); } }, t)),
+        h('button', { type: 'button', class: audit ? 'pill on' : 'pill', 'aria-pressed': String(audit), onClick: () => { audit = true; draw(); } }, 'Changes only'));
+      try {
+        const r = await api('GET', '/logs?limit=500&level=' + level + (audit ? '&audit=1' : ''));
+        box.textContent = r.lines.length ? r.lines.map(fmtLogLine).join('\n') : 'No entries at this level.';
+      } catch (e) { box.textContent = e.message; }
+    };
+    fill(wrap,
+      h('div', { class: 'head' },
+        h('div', null, h('h1', null, 'Log'), h('p', { class: 'sub' }, h('span', { class: 'mono' }, s.logPath), ' · level ' + s.log.level + ' · rotates at ' + s.log.maxSizeMB + ' MB, keeps ' + s.log.maxFiles + ' files')),
+        h('div', { class: 'actions' },
+          h('a', { class: 'btn', href: '#/settings#logs' }, 'Log settings'),
+          h('a', { class: 'btn', href: '/api/v1/logs/download' }, 'Download log'))),
+      h('section', { class: 'card', 'aria-label': 'Log lines' },
+        h('div', { class: 'cardhead' }, h('span', { class: 'muted' }, 'Newest first · refreshes every 10 s'), pills),
+        h('div', { class: 'section' }, box)));
+    every(10000, draw);
+    await draw();
+  }
+
+  // ---------- updates ----------
+
+  const HIDE_UPDATE = 'GHOSTWIRE.hideUpdate';
+
+  // updateBanner tells the Dashboard about a newer release until it is
+  // hidden for that version.
+  function updateBanner() {
+    const v = me.updateAvailable;
+    let hidden = null;
+    try { hidden = localStorage.getItem(HIDE_UPDATE); } catch { /* storage blocked */ }
+    if (!v || hidden === v) return null;
+    const box = h('div', { class: 'notice new' },
+      h('div', null, h('strong', null, 'GHOSTWIRE ' + v + ' is available. '), 'You\'re on v' + me.version.replace(/^v/, '') + '.'),
+      h('div', { class: 'actions' },
+        h('a', { class: 'btn small', href: '#/settings#updates' }, 'How to update'),
+        h('button', { type: 'button', class: 'btn small ghost', onClick: () => {
+          try { localStorage.setItem(HIDE_UPDATE, v); } catch { /* storage blocked */ }
+          box.remove();
+        } }, 'Hide until the next version')));
+    return box;
+  }
+
+  // mdInline turns **bold** and `code` into elements; everything else stays
+  // text.
+  const mdInline = (text) => text.split(/(\*\*[^*]+\*\*|`[^`]+`)/).filter(Boolean).map((t) =>
+    t.startsWith('**') ? h('strong', null, t.slice(2, -2)) : t.startsWith('`') ? h('code', null, t.slice(1, -1)) : t);
+
+  // releaseSummary picks the opening paragraph and the first bullet list out
+  // of the release notes; the full notes are a link away.
+  function releaseSummary(md) {
+    const lines = md.replace(/\r/g, '').split('\n');
+    const para = [];
+    for (const l of lines) {
+      if (!l.trim()) { if (para.length) break; continue; }
+      if (/^(#|- |\* |```|\|)/.test(l)) break;
+      para.push(l.trim());
+    }
+    const items = [];
+    let started = false;
+    for (const l of lines) {
+      const m = /^[-*] (.+)$/.exec(l);
+      if (m) { started = true; items.push(m[1]); } else if (started && l.trim()) break;
+    }
+    return { summary: para.join(' '), items };
+  }
+
+  function updatesCard(initial) {
+    let st = initial;
+    const card = h('section', { class: 'card', id: 'updates', 'aria-labelledby': 'upd' });
+    const setStatus = (next) => {
+      st = next;
+      me.updateAvailable = st.enabled && st.available ? st.latest.version : undefined;
+      drawUpdateHint();
+      draw();
+    };
+    const checkNow = async (btn) => {
+      if (btn) { btn.disabled = true; btn.textContent = 'Checking…'; }
+      try { setStatus(await api('POST', '/updates/check')); } catch (x) { toast(x.message, true); draw(); }
+    };
+    const save = async (updates) => {
+      try {
+        await api('PATCH', '/settings', { updates });
+        const s = await api('GET', '/settings');
+        if (s.updates.enabled) await checkNow(); else setStatus(s.updates);
+      } catch (x) { toast(x.message, true); draw(); }
+    };
+    const SOURCES = [['gitea', 'Gitea', 'git.redetzke.aero/Redetzke/GHOSTWIRE'], ['github', 'GitHub', 'github.com/danielredetzke/GHOSTWIRE']];
+    const srcName = () => SOURCES.find(([k]) => k === st.source)[1];
+
+    function draw() {
+      const cur = 'v' + st.current.replace(/^v/, '');
+      const rel = st.latest;
+      const notes = rel && st.available ? releaseSummary(rel.notes || '') : null;
+      const cmds = st.available && st.file ? [
+        'curl -fLO ' + st.fileUrl,
+        'curl -fLO ' + st.sumsUrl,
+        'sha256sum -c --ignore-missing SHA256SUMS',
+        'chmod +x ' + st.file,
+        'sudo ./' + st.file + ' update',
+      ].join('\n') : null;
+      fill(card,
+        h('div', { class: 'cardhead' },
+          h('h3', { id: 'upd' }, 'Updates'),
+          st.enabled ? h('span', { class: 'muted' }, st.checked ? 'Last checked ' + ago(st.checked) : 'Not checked yet') : null),
+        h('div', { class: 'upvers' },
+          h('div', { class: 'upbox' }, h('span', null, 'Running'), h('strong', { class: 'mono' }, cur)),
+          rel ? h('div', { class: st.available ? 'upbox new' : 'upbox' }, h('span', null, 'Latest release'), h('strong', { class: 'mono' }, rel.version)) : null,
+          h('div', { class: 'upbox' }, h('span', null, 'This server'), h('strong', null, st.arch ? 'Linux · ' + st.arch : 'No release file for this platform'))),
+        st.enabled && st.error ? h('div', { class: 'notice err', role: 'alert' },
+          h('div', null, 'The last check failed: ' + st.error + '. ' + (st.lastOk ? 'Last worked ' + ago(st.lastOk) + '. ' : '') + 'Try the other source.')) : null,
+        rel && !st.available ? h('p', { class: 'uptodate' }, h('span', { class: 'dot ok' }), 'GHOSTWIRE is up to date.') : null,
+        notes ? h('div', { class: 'upnotes' },
+          h('div', { class: 'hd' }, h('strong', null, 'What\'s new in ' + rel.version),
+            h('span', { class: 'muted' }, 'Released ' + fmtDate(rel.published) + ' · from ' + srcName()),
+            ext(rel.url, 'Full notes on ' + srcName())),
+          /security/i.test(notes.summary) ? h('p', { class: 'notice' }, 'Includes security fixes.') : null,
+          notes.summary ? h('p', null, mdInline(notes.summary)) : null,
+          notes.items.length ? h('ul', null, notes.items.map((t) => h('li', null, mdInline(t)))) : null) : null,
+        cmds ? h('div', { class: 'upcmd' },
+          h('div', { class: 'hd' }, h('strong', null, 'Update this server'), h('span', { class: 'muted' }, 'Run on the server. VPN connections stay up.')),
+          h('pre', { class: 'code' }, cmds),
+          h('div', null, h('button', { type: 'button', class: 'btn small', onClick: () => copy(cmds) }, 'Copy commands'))) : null,
+        st.available && !st.file ? h('p', null, 'No release file is built for this platform. ', ext(rel.url, 'See the release')) : null,
+        h('fieldset', { class: 'section' }, h('legend', { class: 'legend' }, 'Release source'),
+          h('div', { class: 'grid' }, SOURCES.map(([k, name, where]) => h('label', { class: 'opt' },
+            h('input', { type: 'radio', name: 'upsrc', value: k, checked: st.source === k, onChange: () => save({ source: k }) }),
+            h('span', null, h('strong', null, name), h('br'), h('span', { class: 'hint mono' }, where))))),
+          h('span', { class: 'hint' }, 'Both carry the same releases and files. The check, the release notes and the download links use the source you pick.')),
+        h('div', { class: 'uprow' },
+          h('label', { class: 'check' },
+            h('input', { type: 'checkbox', checked: st.enabled, onChange: (e) => save({ check: e.target.checked }) }),
+            h('span', null, 'Check for updates once a day', h('br'),
+              h('span', { class: 'hint' }, 'Asks ' + new URL(st.sourceUrl).host + ' for the latest release. Nothing about this server is sent.'))),
+          st.enabled ? h('button', { type: 'button', class: 'btn small', onClick: (e) => checkNow(e.currentTarget) }, 'Check now') : null));
+    }
+    draw();
+    return card;
+  }
+
   // ---------- settings ----------
 
   // ---------- my account ----------
@@ -1800,7 +2257,6 @@
       return;
     }
     const [s, tk, us] = await Promise.all([api('GET', '/settings'), api('GET', '/tokens'), api('GET', '/users')]);
-    let logLevelFilter = 'all';
 
     // users
     const userBody = h('tbody');
@@ -1965,20 +2421,13 @@
       try { await api('DELETE', '/tokens/' + t.id); toast('Revoked ' + t.name); reloadTokens(); } catch (e) { toast(e.message, true); }
     };
 
-    // logs
-    const logBox = h('pre', { class: 'log', tabindex: '0', 'aria-label': 'Log lines, newest first' });
-    const logPills = h('div', { class: 'pills', role: 'group', 'aria-label': 'Level filter' });
-    const drawLogs = async () => {
-      logPills.replaceChildren(...[['all', 'All'], ['info', 'Info'], ['warn', 'Warn'], ['error', 'Error']].map(([k, t]) =>
-        h('button', { type: 'button', class: logLevelFilter === k ? 'pill on' : 'pill', 'aria-pressed': String(logLevelFilter === k), onClick: () => { logLevelFilter = k; drawLogs(); } }, t)));
-      try {
-        const r = await api('GET', '/logs?limit=200&level=' + logLevelFilter);
-        logBox.textContent = r.lines.length ? r.lines.map(fmtLogLine).join('\n') : 'No entries at this level.';
-      } catch (e) { logBox.textContent = e.message; }
-    };
-    const levelSel = h('select', { id: 'lv', onChange: async (e) => {
-      try { await api('PATCH', '/settings', { log: { ...s.log, level: e.target.value } }); s.log.level = e.target.value; toast('Log level: ' + e.target.value); } catch (x) { toast(x.message, true); }
-    } }, ['debug', 'info', 'warn', 'error'].map((l) => h('option', { value: l, selected: s.log.level === l }, l)));
+    const levelSel = h('select', { id: 'lv' }, [['debug', 'Debug: everything'], ['info', 'Info'], ['warn', 'Warnings and errors'], ['error', 'Errors only']].map(([l, t]) => h('option', { value: l, selected: s.log.level === l }, t)));
+    const sessSel = h('select', { id: 'st', onChange: async (e) => {
+      try { await api('PATCH', '/settings', { web: { ...s.web, sessionHours: Number(e.target.value) } }); s.web.sessionHours = Number(e.target.value); toast('Session length saved'); } catch (x) { toast(x.message, true); }
+    } }, [[1, '1 hour'], [12, '12 hours'], [24, '1 day'], [168, '7 days']].map(([v, t]) => h('option', { value: String(v), selected: s.web.sessionHours === v }, t)));
+    const geoBox = h('input', { type: 'checkbox', id: 'geo', checked: s.stats.geoip !== false, onChange: async (e) => {
+      try { await api('PATCH', '/settings', { stats: { ...s.stats, geoip: e.target.checked } }); toast(e.target.checked ? 'Country lookup on' : 'Country lookup off'); } catch (x) { e.target.checked = !e.target.checked; toast(x.message, true); }
+    } });
 
     // sign-in rules
     const requireBox = h('input', { type: 'checkbox', id: 'rq', checked: s.signin.requireMfa, onChange: async (e) => {
@@ -2028,7 +2477,6 @@
     const logFiles = h('input', { id: 'rf', type: 'number', min: '1', max: '100', value: s.log.maxFiles, inputMode: 'numeric' });
     const hourly = presetSelect('rh', s.stats.hourlyHours, [[24, '1 day'], [48, '2 days'], [168, '7 days'], [336, '14 days'], [744, '31 days']], 'hours');
     const daily = presetSelect('rd', s.stats.dailyDays, [[30, '30 days'], [90, '90 days'], [180, '6 months'], [400, '13 months'], [730, '2 years'], [1825, '5 years'], [3660, '10 years']], 'days');
-    const geo = h('input', { type: 'checkbox', checked: s.stats.geoip !== false });
     const geoStatus = s.geo && s.geo.updated ? 'Database from ' + fmtDate(s.geo.updated) + '.' : 'Not downloaded yet.';
     const diskHint = h('span', { class: 'hint' });
     const drawDiskHint = () => {
@@ -2047,14 +2495,45 @@
       if (shrinks && !await confirmDialog({ title: 'Delete older data?', text: 'The new limits are lower: older log files and traffic history beyond them are deleted. This cannot be undone.', ok: 'Save and delete', danger: true })) return;
       try {
         await api('PATCH', '/settings', {
-          log: { ...s.log, maxSizeMB: next.maxSizeMB, maxFiles: next.maxFiles },
-          stats: { hourlyHours: next.hourlyHours, dailyDays: next.dailyDays, geoip: geo.checked },
+          log: { ...s.log, level: levelSel.value, maxSizeMB: next.maxSizeMB, maxFiles: next.maxFiles },
+          stats: { ...s.stats, hourlyHours: next.hourlyHours, dailyDays: next.dailyDays },
         });
-        toast('Retention saved');
+        toast('Logs & history saved');
         render();
       } catch (x) { retErr.textContent = x.message; }
     };
 
+    // copies of config.json that updates leave behind
+    const copies = h('div', { class: 'section' });
+    const drawCopies = async () => {
+      let list;
+      try { list = (await api('GET', '/update-backups')).backups; } catch (x) { fill(copies, h('p', { class: 'err-text' }, x.message)); return; }
+      const remove = async (b) => {
+        if (!await confirmDialog({ title: 'Remove ' + b.name + '?', text: 'This copy of your settings from ' + b.version + ' is deleted from the server. It cannot be restored.', ok: 'Remove', danger: true })) return;
+        try { await api('DELETE', '/update-backups/' + encodeURIComponent(b.name)); toast('Removed ' + b.name); drawCopies(); } catch (x) { toast(x.message, true); }
+      };
+      const removeAll = async () => {
+        const n = list.length;
+        if (!await confirmDialog({ title: n === 1 ? 'Remove the copy?' : 'Remove all ' + n + ' copies?', text: 'They are deleted from the server and cannot be restored. Your current settings are not affected.', ok: 'Remove all', danger: true })) return;
+        try { await api('DELETE', '/update-backups'); toast(n === 1 ? 'Removed 1 copy' : 'Removed ' + n + ' copies'); drawCopies(); } catch (x) { toast(x.message, true); }
+      };
+      const total = list.reduce((t, b) => t + b.size, 0);
+      fill(copies,
+        h('div', { class: 'cardhead' },
+          h('div', null, h('strong', null, 'Copies made by updates'),
+            h('p', { class: 'lead', style: { marginBottom: '0' } }, 'Each update saves the previous config.json next to it. They hold the same secrets as a backup.')),
+          list.length ? h('button', { type: 'button', class: 'btn', onClick: removeAll }, 'Remove all') : null),
+        list.length ? h('div', { class: 'tbl section' }, h('table', { class: 'narrow' },
+          h('thead', null, h('tr', null, h('th', null, 'File'), h('th', null, 'From version'), h('th', null, 'Saved'), h('th', { class: 'num' }, 'Size'), h('th', null, h('span', { class: 'sr' }, 'Actions')))),
+          h('tbody', null, list.map((b, i) => h('tr', null,
+            h('td', null, h('span', { class: 'mono' }, b.name), i === 0 ? h('span', { class: 'tag plain' }, 'Newest') : null),
+            h('td', { class: 'mono' }, b.version),
+            h('td', null, fmtStamp(b.modified)),
+            h('td', { class: 'num' }, fmtBytes(b.size)),
+            h('td', { class: 'num' }, h('button', { type: 'button', class: 'btn small', onClick: () => remove(b) }, 'Remove'))))))) : h('p', { class: 'muted', style: { margin: '12px 0 0' } }, 'No copies from updates.'),
+        list.length ? h('p', { class: 'hint', style: { margin: '8px 0 0' } }, list.length + (list.length === 1 ? ' copy, ' : ' copies, ') + fmtBytes(total) + ' next to config.json. After each update, only the newest 3 are kept.') : null);
+    };
+
     // backup
     const restoreInput = h('input', { type: 'file', accept: 'application/json,.json', hidden: true, onChange: async (e) => {
       const f = e.target.files[0];
@@ -2070,85 +2549,94 @@
       } catch (x) { toast(x.message, true); }
     } });
 
+    const groupHead = (id, title, text) => h('div', { class: 'group', id }, h('h2', null, title), h('p', null, text));
     fill(wrap,
-      h('div', null, h('h1', null, 'Settings'), h('p', { class: 'sub' }, 'Users, web interface, API access for the iOS app, logs, data retention and backups')),
+      h('div', null, h('h1', null, 'Settings'), h('p', { class: 'sub' }, 'Who can sign in, the web interface, logs and history, updates and backups')),
       restartBox,
 
+      groupHead('g-access', 'Access', 'Who can sign in, and how.'),
       h('section', { class: 'card flush', 'aria-labelledby': 'usr' },
         h('div', { class: 'cardhead' },
-          h('div', null, h('h2', { id: 'usr' }, 'Users'), h('p', { class: 'lead', style: { marginBottom: '0' } }, 'Everyone here is an admin. You cannot delete yourself, so one user always remains.')),
+          h('div', null, h('h3', { id: 'usr' }, 'Users'), h('p', { class: 'lead', style: { marginBottom: '0' } }, 'Everyone here is an admin. You cannot delete yourself, so one user always remains.')),
           h('button', { type: 'button', class: 'btn primary', onClick: addUser }, 'Add user')),
         h('div', { class: 'tbl' }, h('table', null,
           h('thead', null, h('tr', null, h('th', null, 'User'), h('th', null, 'Status'), h('th', null, 'Two-step'), h('th', null, 'Last sign-in'), h('th', null, 'App tokens'), h('th', null, 'Created'), h('th', null, h('span', { class: 'sr' }, 'Actions')))),
           userBody))),
 
       h('section', { class: 'card', 'aria-labelledby': 'sgn' },
-        h('h2', { id: 'sgn' }, 'Sign-in'),
-        h('p', { class: 'lead' }, 'Everyone sets up two-step sign-in under My account: an authenticator app or passkeys, including on a YubiKey. Changes apply immediately.'),
+        h('div', { class: 'cardhead' }, h('h3', { id: 'sgn' }, 'Sign-in'), h('span', { class: 'saves' }, 'Saves right away')),
+        h('p', { class: 'lead' }, 'Everyone sets up two-step sign-in under My account: an authenticator app or passkeys, including on a YubiKey.'),
         h('label', { class: 'check' }, requireBox, h('span', null, 'Require two-step sign-in for everyone', h('br'),
-          h('span', { class: 'hint' }, 'Users without it are asked to set it up right after their password. To help someone who lost their phone or key, use Edit → Reset two-step sign-in.')))),
+          h('span', { class: 'hint' }, 'Users without it are asked to set it up right after their password. To help someone who lost their phone or key, use Edit → Reset two-step sign-in.'))),
+        h('div', { class: 'grid section' },
+          h('div', { class: 'field' }, h('label', { htmlFor: 'st' }, 'Stay signed in for'), sessSel, h('span', { class: 'hint' }, 'Applies to new sign-ins')),
+          h('div', { class: 'field' }), h('div', { class: 'field' }))),
 
+      h('section', { class: 'card', 'aria-labelledby': 'api' },
+        h('div', { class: 'cardhead' },
+          h('div', null, h('h3', { id: 'api' }, 'iOS app and API tokens'), h('p', { class: 'lead', style: { marginBottom: '0' } }, 'For the iOS app and scripts. A token appears once when you create it, and only a hash is stored.')),
+          h('button', { type: 'button', class: 'btn primary', onClick: () => pairDialog(reloadTokens) }, 'Pair iOS app')),
+        h('div', { class: 'tbl section' }, h('table', { class: 'narrow' },
+          h('thead', null, h('tr', null, h('th', null, 'Name'), h('th', null, 'Owner'), h('th', null, 'Access'), h('th', null, 'Created'), h('th', null, 'Last used'), h('th', null, h('span', { class: 'sr' }, 'Actions')))),
+          tbody))),
+
+      groupHead('g-web', 'Web interface', 'Where this interface listens and what strangers see.'),
       h('form', { class: 'card', onSubmit: saveWeb, 'aria-labelledby': 'web' },
-        h('h2', { id: 'web' }, 'Web interface'),
-        h('p', { class: 'lead' }, 'Changes take effect after the service restarts.'),
+        h('div', { class: 'cardhead' }, h('h3', { id: 'web' }, 'Address and HTTPS'), h('span', { class: 'saves' }, 'Save, then restart')),
+        h('p', { class: 'lead' }, 'Usually set once during install.'),
         h('div', { class: 'grid' },
           h('div', { class: 'field' }, h('label', { htmlFor: 'la' }, 'Listen address'), h('input', { id: 'la', class: 'mono', value: web.listen, onInput: (e) => { web.listen = e.target.value.trim(); } })),
           h('div', { class: 'field' }, h('label', { htmlFor: 'hl' }, 'HTTP listen address'), h('input', { id: 'hl', class: 'mono', value: web.httpListen, placeholder: 'off', onInput: (e) => { web.httpListen = e.target.value.trim(); } }), h('span', { class: 'hint' }, 'Redirects to HTTPS and answers Let\'s Encrypt http-01 checks. Empty turns it off')),
           h('div', { class: 'field' }, h('label', { htmlFor: 'tls' }, 'HTTPS'), modeSel),
-          h('div', { class: 'field' }, h('label', { htmlFor: 'st' }, 'Session length'), h('select', { id: 'st', onChange: (e) => { web.sessionHours = Number(e.target.value); } },
-            [[1, '1 hour'], [12, '12 hours'], [24, '1 day'], [168, '7 days']].map(([v, t]) => h('option', { value: String(v), selected: web.sessionHours === v }, t)))),
           s.fingerprint ? h('div', { class: 'field' }, h('label', { htmlFor: 'fp' }, 'Certificate fingerprint (SHA-256)'), h('input', { id: 'fp', class: 'mono', value: s.fingerprint, readOnly: true }), h('span', { class: 'hint' }, 'The iOS app pins this when pairing')) : null),
         h('div', { class: 'section' }, fAcme, fFiles),
         webErr,
         h('div', { class: 'formfoot' }, h('button', { type: 'submit', class: 'btn primary' }, 'Save'))),
 
       h('section', { class: 'card', 'aria-labelledby': 'dcy' },
-        h('h2', { id: 'dcy' }, 'Decoy'),
-        h('p', { class: 'lead' }, 'Shows an ordinary web server page instead of this interface. The iOS app and setup links keep working. Changes apply immediately.'),
+        h('div', { class: 'cardhead' }, h('h3', { id: 'dcy' }, 'Decoy'), h('span', { class: 'saves' }, 'Saves right away')),
+        h('p', { class: 'lead' }, 'Shows an ordinary web server page instead of this interface. The iOS app and setup links keep working.'),
         h('label', { class: 'check' }, decoyBox, h('span', null, 'Decoy', h('br'),
           h('span', { class: 'hint' }, 'Hides the web interface. Turn it off again in the iOS app.'))),
         h('div', { class: 'grid section' },
           h('div', { class: 'field' }, h('label', { htmlFor: 'dp' }, 'Decoy page'), decoySel))),
 
-      h('section', { class: 'card', 'aria-labelledby': 'api' },
-        h('div', { class: 'cardhead' },
-          h('div', null, h('h2', { id: 'api' }, 'API tokens'), h('p', { class: 'lead', style: { marginBottom: '0' } }, 'For the iOS app and scripts. A token appears once when you create it, and only a hash is stored.')),
-          h('button', { type: 'button', class: 'btn primary', onClick: () => pairDialog(reloadTokens) }, 'Pair iOS app')),
-        h('div', { class: 'tbl section' }, h('table', { class: 'narrow' },
-          h('thead', null, h('tr', null, h('th', null, 'Name'), h('th', null, 'Owner'), h('th', null, 'Access'), h('th', null, 'Created'), h('th', null, 'Last used'), h('th', null, h('span', { class: 'sr' }, 'Actions')))),
-          tbody))),
-
-      h('section', { class: 'card', 'aria-labelledby': 'lg' },
-        h('div', { class: 'cardhead' },
-          h('div', null, h('h2', { id: 'lg' }, 'Log'), h('p', { class: 'lead', style: { marginBottom: '0' } }, h('span', { class: 'mono' }, s.logPath), ' · rotates at ' + s.log.maxSizeMB + ' MB, keeps ' + s.log.maxFiles + ' files')),
-          logPills),
-        h('div', { class: 'section' }, logBox),
-        h('div', { class: 'grid section' },
-          h('div', { class: 'field' }, h('label', { htmlFor: 'lv' }, 'Log level'), levelSel),
-          h('div', { class: 'field', style: { justifyContent: 'flex-end' } }, h('a', { class: 'btn', href: '/api/v1/logs/download' }, 'Download log')))),
-
+      groupHead('logs', 'Logs & history', 'What the server records and for how long. The log itself is on the Log page.'),
       h('form', { class: 'card', onSubmit: saveRetention, 'aria-labelledby': 'ret' },
-        h('h2', { id: 'ret' }, 'Data retention'),
-        h('p', { class: 'lead' }, 'How much log and traffic history is kept. Changes apply immediately, without a restart.'),
+        h('div', { class: 'cardhead' }, h('h3', { id: 'ret' }, 'Log and traffic history'), h('span', { class: 'saves' }, 'Save, no restart')),
+        h('p', { class: 'lead' }, 'Lower limits delete older data when you save. All-time totals are always kept.'),
         h('div', { class: 'grid' },
+          h('div', { class: 'field' }, h('label', { htmlFor: 'lv' }, 'Log level'), levelSel),
           h('div', { class: 'field' }, h('label', { htmlFor: 'rs' }, 'Log file size (MB)'), logSize, h('span', { class: 'hint' }, 'The log starts a new file at this size. 1–1000')),
-          h('div', { class: 'field' }, h('label', { htmlFor: 'rf' }, 'Old log files kept'), logFiles, diskHint),
+          h('div', { class: 'field' }, h('label', { htmlFor: 'rf' }, 'Old log files kept'), logFiles, diskHint)),
+        h('div', { class: 'grid section' },
           h('div', { class: 'field' }, h('label', { htmlFor: 'rh' }, 'Hourly traffic history'), hourly, h('span', { class: 'hint' }, 'Used by the 24-hour charts')),
-          h('div', { class: 'field' }, h('label', { htmlFor: 'rd' }, 'Daily traffic history'), daily, h('span', { class: 'hint' }, 'Used by the 7- and 30-day charts and the connection history. All-time totals are always kept'))),
-        h('label', { class: 'check section' }, geo, h('span', null, 'Show country and network of peer addresses', h('br'),
-          h('span', { class: 'hint' }, 'Downloads the free DB-IP Lite databases (about 20 MB) once a month and looks addresses up on this server only. ' + geoStatus))),
+          h('div', { class: 'field' }, h('label', { htmlFor: 'rd' }, 'Daily traffic history'), daily, h('span', { class: 'hint' }, 'Used by the 7- and 30-day charts and the connection history')),
+          h('div', { class: 'field' })),
         retErr,
-        h('div', { class: 'formfoot' }, h('button', { type: 'submit', class: 'btn primary' }, 'Save retention'))),
+        h('div', { class: 'formfoot' }, h('a', { class: 'btn', href: '#/log' }, 'Open the log'), h('button', { type: 'submit', class: 'btn primary' }, 'Save'))),
+
+      h('section', { class: 'card', 'aria-labelledby': 'geo-h' },
+        h('div', { class: 'cardhead' }, h('h3', { id: 'geo-h' }, 'Country and network lookup'), h('span', { class: 'saves' }, 'Saves right away')),
+        h('label', { class: 'check' }, geoBox, h('span', null, 'Show country and network of peer addresses', h('br'),
+          h('span', { class: 'hint' }, 'Downloads the free DB-IP Lite databases (about 20 MB) once a month and looks addresses up on this server only. ' + geoStatus)))),
+
+      groupHead('g-upkeep', 'Upkeep', 'New versions and copies of your settings.'),
+      updatesCard(s.updates),
 
       h('section', { class: 'card', 'aria-labelledby': 'bk' },
-        h('h2', { id: 'bk' }, 'Backup & restore'),
-        h('p', { class: 'lead' }, 'A backup is a copy of config.json with server key, peers, tokens and settings. Keep it safe: it contains the server\'s private key.'),
+        h('h3', { id: 'bk' }, 'Backup & restore'),
+        h('p', { class: 'lead' }, 'A backup is a copy of config.json with server key, peers, tokens and settings. Keep it safe: it contains the server\'s private key, preshared keys and authenticator app secrets.'),
         h('div', { class: 'actions' },
           h('a', { class: 'btn', href: '/api/v1/backup' }, 'Download backup'),
           h('button', { type: 'button', class: 'btn', onClick: () => restoreInput.click() }, 'Restore from file…'),
-          restoreInput)));
-    await drawLogs();
+          restoreInput),
+        copies));
+    drawCopies();
+    const jumpTo = location.hash.split('#')[2];
+    if (jumpTo) document.getElementById(jumpTo)?.scrollIntoView();
   }
 
+
   render();
 })();

auth.go

@@ -287,9 +287,14 @@ func remoteIP(r *http.Request) string {
 		host = r.RemoteAddr
 	}
 	// Behind a local reverse proxy the real client is in X-Forwarded-For.
+	// The proxy appends the address it saw, so only the last entry counts:
+	// earlier ones come from the client and can be anything.
 	if ip := net.ParseIP(host); ip != nil && ip.IsLoopback() {
-		if xff := r.Header.Get("X-Forwarded-For"); xff != "" {
-			return strings.TrimSpace(strings.Split(xff, ",")[0])
+		if xff := r.Header.Values("X-Forwarded-For"); len(xff) > 0 {
+			list := strings.Split(xff[len(xff)-1], ",")
+			if last := strings.TrimSpace(list[len(list)-1]); net.ParseIP(last) != nil {
+				return last
+			}
 		}
 	}
 	return host

config.go

@@ -11,6 +11,7 @@ import (
 	"path/filepath"
 	"regexp"
 	"slices"
+	"strconv"
 	"strings"
 	"sync"
 	"syscall"
@@ -34,8 +35,17 @@ type Config struct {
 	Stats   StatsConfig   `json:"stats"`
 	Decoy   DecoyConfig   `json:"decoy"`
 	SignIn  SignInConfig  `json:"signin"`
+	Updates UpdatesConfig `json:"updates"`
 }
 
+// UpdatesConfig sets the daily check for a newer release.
+type UpdatesConfig struct {
+	Check  *bool  `json:"check,omitempty"` // default on
+	Source string `json:"source"`          // gitea | github, see updateSources
+}
+
+func (c UpdatesConfig) checkEnabled() bool { return c.Check == nil || *c.Check }
+
 // SignInConfig holds the rules for signing in to the web interface.
 type SignInConfig struct {
 	// RequireMFA sends users without two-step sign-in to set it up before
@@ -67,8 +77,29 @@ const (
 	minLogFiles, maxLogFiles     = 1, 100
 	minHourlyHours, maxHourlyHrs = 24, 24 * 31
 	minDailyDays, maxDailyDays   = 7, 3660
+	minSessionHours              = 1
+	maxSessionHours              = 30 * 24
 )
 
+// validateListen checks a listen address like ":443" or "192.0.2.1:443".
+// Empty is allowed when optional (the HTTP listener is then off).
+func validateListen(addr, field string, optional bool) error {
+	if addr == "" && optional {
+		return nil
+	}
+	host, port, err := net.SplitHostPort(addr)
+	if err != nil {
+		return fmt.Errorf("%s %q must look like :443 or 192.0.2.1:443", field, addr)
+	}
+	if n, err := strconv.Atoi(port); err != nil || n < 1 || n > 65535 {
+		return fmt.Errorf("%s %q: the port must be 1–65535", field, addr)
+	}
+	if host != "" && host != "localhost" && checkEndpoint(host) != nil {
+		return fmt.Errorf("%s %q: %q is not an IP address or host name", field, addr, host)
+	}
+	return nil
+}
+
 type WebConfig struct {
 	Listen       string    `json:"listen"`     // HTTPS (or HTTP when tls.mode is "off") listen address
 	HTTPListen   string    `json:"httpListen"` // plain HTTP for ACME http-01 and redirects; "" disables
@@ -246,6 +277,9 @@ func (c *Config) applyDefaults() {
 	if c.Decoy.Page == "" {
 		c.Decoy.Page = "nginx"
 	}
+	if c.Updates.Source == "" {
+		c.Updates.Source = "gitea"
+	}
 	if c.APITokens == nil {
 		c.APITokens = []APIToken{}
 	}
@@ -352,7 +386,9 @@ func (c *Config) validate() error {
 	if v6.Masked() != v6 {
 		return fmt.Errorf("IPv6 network must be the network address, e.g. %s", v6.Masked())
 	}
-	if s.Endpoint != "" && strings.ContainsAny(s.Endpoint, " /:") && net.ParseIP(s.Endpoint) == nil {
+	// The endpoint is written into client configs as is, so it must be a
+	// plain host name or IP: anything else could add lines to them.
+	if s.Endpoint != "" && checkEndpoint(s.Endpoint) != nil {
 		return errors.New("endpoint must be a host name or IP address without port")
 	}
 	if err := validateHostList(s.ClientDefaults.DNS, "DNS", false); err != nil {
@@ -382,6 +418,18 @@ func (c *Config) validate() error {
 	if _, ok := decoyPages[c.Decoy.Page]; !ok {
 		return fmt.Errorf("unknown decoy page %q", c.Decoy.Page)
 	}
+	if _, ok := updateSources[c.Updates.Source]; !ok {
+		return fmt.Errorf("update source must be gitea or github")
+	}
+	if err := validateListen(c.Web.Listen, "listen address", false); err != nil {
+		return err
+	}
+	if err := validateListen(c.Web.HTTPListen, "HTTP listen address", true); err != nil {
+		return err
+	}
+	if h := c.Web.SessionHours; h < minSessionHours || h > maxSessionHours {
+		return fmt.Errorf("session length must be %d–%d hours", minSessionHours, maxSessionHours)
+	}
 	switch c.Web.TLS.Mode {
 	case "acme":
 		if c.Web.TLS.Domain == "" {
@@ -571,6 +619,12 @@ func (s *Store) Update(fn func(c *Config) error) error {
 		s.mu.Unlock()
 		return &userError{err.Error()}
 	}
+	// With no user left (applyDefaults then adds an "admin" without a
+	// password), nobody could sign in until someone ran "passwd" on the server.
+	if old.passwordSet() && !next.passwordSet() {
+		s.mu.Unlock()
+		return &userError{"this would leave no user with a password, and nobody could sign in"}
+	}
 	if err := writeFileAtomic(s.path, next, 0o600); err != nil {
 		s.mu.Unlock()
 		return err

kernel.go

@@ -4,6 +4,7 @@ import (
 	"log/slog"
 	"net/netip"
 	"os"
+	"slices"
 	"strings"
 	"sync"
 	"time"
@@ -40,6 +41,28 @@ type Kernel interface {
 	Close() error
 }
 
+// lanBlock picks, from the networks on the uplinks, the ones peers must not
+// reach while LAN access is off: private IPv4 networks, and IPv6 networks
+// except link-local, since a home LAN uses global IPv6 addresses. IPv6
+// prefixes shorter than /48 are left out: they are no LAN.
+func lanBlock(nets []netip.Prefix) []netip.Prefix {
+	var out []netip.Prefix
+	for _, p := range nets {
+		a := p.Addr().Unmap()
+		p = netip.PrefixFrom(a, min(p.Bits(), a.BitLen())).Masked()
+		switch {
+		case a.Is4() && !a.IsPrivate():
+			continue
+		case a.Is6() && (a.IsLinkLocalUnicast() || a.IsLoopback() || p.Bits() < 48):
+			continue
+		}
+		if !slices.Contains(out, p) {
+			out = append(out, p)
+		}
+	}
+	return out
+}
+
 // readSysctl returns the trimmed content of a /proc/sys file, or "".
 func readSysctl(path string) string {
 	b, err := os.ReadFile(path)
@@ -56,6 +79,10 @@ type Reconciler struct {
 	store   *Store
 	trigger chan struct{}
 
+	// applyMu runs one apply at a time. Each reads the config once it holds
+	// the lock, so the last apply always uses the newest config.
+	applyMu sync.Mutex
+
 	mu        sync.Mutex
 	lastErr   error
 	lastApply time.Time
@@ -76,6 +103,8 @@ func (r *Reconciler) Kick() {
 // ApplyNow applies synchronously and returns the result, so an API call can
 // report kernel errors to the user.
 func (r *Reconciler) ApplyNow() error {
+	r.applyMu.Lock()
+	defer r.applyMu.Unlock()
 	err := r.kernel.Apply(r.store.Get())
 	r.mu.Lock()
 	r.lastErr, r.lastApply = err, time.Now()

kernel_linux.go

@@ -217,7 +217,8 @@ func (k *linuxKernel) Apply(c *Config) error {
 	if c.Server.IPv6Enabled {
 		_ = os.WriteFile("/proc/sys/net/ipv6/conf/all/forwarding", []byte("1"), 0o644)
 	}
-	return applyFirewall(c, k.Uplink(c, false), k.Uplink(c, true), lanNetworks(k.Uplink(c, false)))
+	up4, up6 := k.Uplink(c, false), k.Uplink(c, true)
+	return applyFirewall(c, up4, up6, lanNetworks(up4, up6))
 }
 
 func (k *linuxKernel) Sample(iface string) ([]PeerSample, error) {
@@ -264,27 +265,27 @@ func (k *linuxKernel) Uplink(c *Config, v6 bool) string {
 	return l.Attrs().Name
 }
 
-// lanNetworks returns the private IPv4 networks on the uplink, used to block
-// peers from the server's LAN when LAN access is off.
-func lanNetworks(uplink string) []netip.Prefix {
-	if uplink == "" {
-		return nil
+// lanNetworks returns the LAN networks on the IPv4 and IPv6 uplinks (see
+// lanBlock), used to block peers from the server's LAN when LAN access is off.
+func lanNetworks(uplinks ...string) []netip.Prefix {
+	var nets []netip.Prefix
+	for i, uplink := range uplinks {
+		if uplink == "" || slices.Contains(uplinks[:i], uplink) {
+			continue
 		}
 		l, err := netlink.LinkByName(uplink)
 		if err != nil {
-		return nil
-	}
-	addrs, _ := netlink.AddrList(l, netlink.FAMILY_V4)
-	var out []netip.Prefix
-	for _, a := range addrs {
-		if !a.IP.IsPrivate() {
 			continue
 		}
+		addrs, _ := netlink.AddrList(l, netlink.FAMILY_ALL)
+		for _, a := range addrs {
 			ones, _ := a.Mask.Size()
-		ip, _ := netip.AddrFromSlice(a.IP.To4())
-		out = append(out, netip.PrefixFrom(ip, ones).Masked())
+			if ip, ok := netip.AddrFromSlice(a.IP); ok {
+				nets = append(nets, netip.PrefixFrom(ip.Unmap(), ones))
 			}
-	return out
+		}
+	}
+	return lanBlock(nets)
 }
 
 // publicAddr reports the uplink's address for the health check: the first

kernel_other.go

@@ -5,8 +5,10 @@ package main
 import (
 	"fmt"
 	"log/slog"
+	"maps"
 	"math/rand/v2"
 	"net/netip"
+	"slices"
 	"sync"
 	"time"
 )
@@ -17,6 +19,7 @@ import (
 type simKernel struct {
 	mu    sync.Mutex
 	peers map[string]*PeerSample
+	last  time.Time // previous Sample; traffic grows with the time since
 }
 
 func newKernel() (Kernel, error) {
@@ -53,17 +56,23 @@ func (k *simKernel) Apply(c *Config) error {
 func (k *simKernel) Sample(string) ([]PeerSample, error) {
 	k.mu.Lock()
 	defer k.mu.Unlock()
+	now := time.Now()
+	f := 1.0
+	if !k.last.IsZero() {
+		f = now.Sub(k.last).Seconds() / 30
+	}
+	k.last = now
 	var out []PeerSample
-	i := 0
-	for _, p := range k.peers {
-		// Every third peer stays idle; the others move some data.
+	for i, key := range slices.Sorted(maps.Keys(k.peers)) {
+		p := k.peers[key]
+		// Every third peer stays idle; the others move some data, scaled to
+		// the time since the previous sample.
 		if i%3 != 2 {
-			p.TxBytes += rand.Int64N(40 << 20)
-			p.RxBytes += rand.Int64N(6 << 20)
-			p.LastHandshake = time.Now().Add(-time.Duration(rand.IntN(90)) * time.Second)
+			p.TxBytes += int64(float64(rand.Int64N(40<<20)) * f)
+			p.RxBytes += int64(float64(rand.Int64N(6<<20)) * f)
+			p.LastHandshake = now.Add(-time.Duration(rand.IntN(90)) * time.Second)
 		}
 		out = append(out, *p)
-		i++
 	}
 	return out, nil
 }

main.go

@@ -219,18 +219,25 @@ func run(configPath string) error {
 	var stopOnce sync.Once
 	shutdown := func() { stopOnce.Do(func() { close(stop) }) }
 
+	speeds := newSpeeds(store, kernel)
 	auth := newAuth(store)
 	app := &App{
-		store: store, kernel: kernel, recon: recon, stats: stats, auth: auth, tls: webTLS,
-		logPath: logPath, logw: logw, geo: geo, started: time.Now(), shutdown: shutdown,
+		store: store, kernel: kernel, recon: recon, stats: stats, speeds: speeds, auth: auth, tls: webTLS,
+		logPath: logPath, logw: logw, geo: geo, updates: newUpdater(cfg.Updates), started: time.Now(), shutdown: shutdown,
+		webAddrs: []string{cfg.Web.Listen},
+	}
+	if cfg.Web.HTTPListen != "" && cfg.Web.TLS.Mode != "off" {
+		app.webAddrs = append(app.webAddrs, cfg.Web.HTTPListen)
 	}
 
 	var wg sync.WaitGroup
-	wg.Add(4)
+	wg.Add(6)
 	go func() { defer wg.Done(); recon.Run(stop) }()
 	go func() { defer wg.Done(); stats.Run(stop) }()
+	go func() { defer wg.Done(); speeds.Run(stop) }()
 	go func() { defer wg.Done(); stats.RunPings(stop) }()
 	go func() { defer wg.Done(); geo.Run(stop) }()
+	go func() { defer wg.Done(); app.updates.Run(stop) }()
 	go func() {
 		t := time.NewTicker(10 * time.Minute)
 		defer t.Stop()

main_test.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"net"
 	"net/http"
 	"net/http/cookiejar"
 	"net/http/httptest"
@@ -78,6 +79,16 @@ func TestValidate(t *testing.T) {
 		"bad dns":         func(c *Config) { c.Peers[0].DNS = []string{"dns.example"} },
 		"bad port":        func(c *Config) { c.Server.ListenPort = 70000 },
 		"unmasked net":    func(c *Config) { c.Server.IPv4 = "10.84.12.5/24" },
+		"update source":   func(c *Config) { c.Updates.Source = "sourceforge" },
+		// The endpoint goes into client configs: no extra lines.
+		"endpoint newline": func(c *Config) { c.Server.Endpoint = "vpn.example.net\n[Interface]\nPreUp=id;#" },
+		"endpoint tab":     func(c *Config) { c.Server.Endpoint = "vpn.example.net\tx" },
+		"endpoint port":    func(c *Config) { c.Server.Endpoint = "vpn.example.net:51820" },
+		"listen":           func(c *Config) { c.Web.Listen = "not-an-address" },
+		"listen port":      func(c *Config) { c.Web.Listen = ":70000" },
+		"http listen":      func(c *Config) { c.Web.HTTPListen = "80" },
+		"session hours":    func(c *Config) { c.Web.SessionHours = -1 },
+		"session too long": func(c *Config) { c.Web.SessionHours = 100000 },
 	} {
 		cc := c.clone()
 		mutate(cc)
@@ -85,6 +96,20 @@ func TestValidate(t *testing.T) {
 			t.Errorf("%s: expected an error", name)
 		}
 	}
+	for _, ep := range []string{"vpn.example.net", "203.0.113.7", "2001:db8::1"} {
+		cc := c.clone()
+		cc.Server.Endpoint = ep
+		if err := cc.validate(); err != nil {
+			t.Errorf("endpoint %q rejected: %v", ep, err)
+		}
+	}
+	for _, l := range []string{":443", "0.0.0.0:8443", "[::]:443", "localhost:8080"} {
+		cc := c.clone()
+		cc.Web.Listen = l
+		if err := cc.validate(); err != nil {
+			t.Errorf("listen %q rejected: %v", l, err)
+		}
+	}
 }
 
 func TestClientConfig(t *testing.T) {
@@ -350,6 +375,30 @@ func TestAPI(t *testing.T) {
 	bearer("POST", "/tokens", 403, map[string]string{"name": "more", "scope": "rw"})
 	bearer("DELETE", "/tokens/"+tok["id"].(string), 403)
 	bearer("GET", "/backup", 403)
+	bearer("GET", "/update-backups", 403)
+	bearer("DELETE", "/update-backups", 403)
+
+	// Config copies made by update: listed newest first, removed one by
+	// one or all at once; nothing else in the folder can be removed.
+	for i, v := range []string{"v0.3.2", "v0.4.0"} {
+		f := filepath.Join(dir, "config.json.bak-"+v)
+		_ = os.WriteFile(f, []byte("{}"), 0o600)
+		_ = os.Chtimes(f, time.Now(), time.Now().Add(time.Duration(i-2)*time.Hour))
+	}
+	list := call("GET", "/update-backups", nil, 200)["backups"].([]any)
+	if len(list) != 2 || list[0].(map[string]any)["version"] != "v0.4.0" {
+		t.Fatalf("update backups: %v", list)
+	}
+	call("DELETE", "/update-backups/config.json", nil, 400)
+	call("DELETE", "/update-backups/stats.json", nil, 400)
+	call("DELETE", "/update-backups/config.json.bak-v9.9.9", nil, 400)
+	call("DELETE", "/update-backups/config.json.bak-v0.3.2", nil, 200)
+	if r := call("DELETE", "/update-backups", nil, 200); r["removed"] != float64(1) {
+		t.Fatalf("remove all: %v", r)
+	}
+	if _, err := os.Stat(filepath.Join(dir, "config.json")); err != nil {
+		t.Fatal("config.json is gone:", err)
+	}
 
 	call("DELETE", "/peers/"+id, nil, 200)
 	if len(store.Get().Peers) != 0 {
@@ -1194,6 +1243,17 @@ func TestMFA(t *testing.T) {
 	c3("POST", "/auth/login/recovery", map[string]string{"ticket": ticket, "code": codes[0].(string)}, 401)
 	c3("POST", "/auth/login/recovery", map[string]string{"ticket": ticket, "code": codes[1].(string)}, 200)
 
+	// Session length needs no restart; the listen address does.
+	web := store.Get().Web
+	web.SessionHours = 24
+	if r := adm("PATCH", "/settings", map[string]any{"web": web}, 200); r["restartRequired"] != false || store.Get().Web.SessionHours != 24 {
+		t.Fatalf("session length: %v", r)
+	}
+	web.Listen = "127.0.0.1:9443"
+	if r := adm("PATCH", "/settings", map[string]any{"web": web}, 200); r["restartRequired"] != true {
+		t.Fatalf("listen address: %v", r)
+	}
+
 	// Required for everyone: a user without it can only set it up.
 	adm("PATCH", "/settings", map[string]any{"signin": map[string]bool{"requireMfa": true}}, 200)
 	u := adm("POST", "/users", map[string]any{"username": "eve", "password": "eve's password 1", "mustChangePassword": false}, 201)["user"].(map[string]any)
@@ -1250,3 +1310,300 @@ func TestDropSecurityKeys(t *testing.T) {
 		t.Fatal("security key still in config.json")
 	}
 }
+
+func TestSpeeds(t *testing.T) {
+	dir := t.TempDir()
+	store, err := openStore(filepath.Join(dir, "config.json"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	key, _ := newPrivateKey()
+	pub := key.PublicKey().String()
+	if err := store.Update(func(c *Config) error {
+		c.Peers = append(c.Peers, Peer{ID: "p1", Name: "phone", IPv4: serverIPv4(netip.MustParsePrefix(c.Server.IPv4)).Next().String(), PublicKey: pub, Enabled: true})
+		return nil
+	}); err != nil {
+		t.Fatal(err)
+	}
+	k := &fakeKernel{}
+	sp := newSpeeds(store, k)
+	t0 := time.Unix(1_800_000_000, 0)
+	step := func(sec int, rx, tx int64) {
+		k.samples = []PeerSample{{PublicKey: pub, RxBytes: rx, TxBytes: tx}}
+		sp.sample(t0.Add(time.Duration(sec) * time.Second))
+	}
+	_, ch, cancel := sp.Subscribe()
+	defer cancel()
+	step(0, 1000, 1000)
+	if n := len(sp.Since(0)); n != 0 {
+		t.Fatalf("first sample made %d points, want 0", n)
+	}
+	step(2, 1250, 3000) // +250 up, +2000 down in 2 s
+	step(4, 10, 20)     // counter reset: no speed for this step
+	pts := sp.Since(0)
+	if len(pts) != 2 {
+		t.Fatalf("got %d points, want 2", len(pts))
+	}
+	if got, want := pts[0].Peers["p1"], [2]int64{8000, 1000}; got != want {
+		t.Fatalf("speed = %v, want %v (down, up in bit/s)", got, want)
+	}
+	if got := <-ch; got.T != pts[0].T {
+		t.Fatalf("subscriber got step %d, want %d", got.T, pts[0].T)
+	}
+	if _, ok := pts[1].Peers["p1"]; ok {
+		t.Fatal("a counter reset reported a speed")
+	}
+	if got := sp.Since(pts[0].T); len(got) != 1 || got[0].T != pts[1].T {
+		t.Fatalf("Since returned %v", got)
+	}
+	for i := 0; i < speedPoints+5; i++ {
+		step(6+2*i, 0, 0)
+	}
+	if n := len(sp.Since(0)); n != speedPoints {
+		t.Fatalf("kept %d points, want %d", n, speedPoints)
+	}
+}
+
+// signedInApp starts the API with a signed-in admin and returns the app
+// and a call function.
+func signedInApp(t *testing.T) (*App, func(method, path string, body any, want int) map[string]any) {
+	t.Helper()
+	dir := t.TempDir()
+	store, err := openStore(filepath.Join(dir, "config.json"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	hash, _ := hashPassword("a long test password")
+	_ = store.Update(func(c *Config) error { c.Users[0].PasswordHash = hash; return nil })
+	k := &fakeKernel{}
+	st, _ := openStats(filepath.Join(dir, "stats.json"), store, k)
+	app := &App{store: store, kernel: k, recon: newReconciler(k, store), stats: st, auth: newAuth(store),
+		tls: &webTLS{}, logPath: filepath.Join(dir, "log.jsonl"), started: time.Now(), shutdown: func() {}}
+	srv := httptest.NewServer(app.routes())
+	t.Cleanup(srv.Close)
+	jar, _ := cookiejar.New(nil)
+	cl := &http.Client{Jar: jar}
+	call := func(method, path string, body any, want int) map[string]any {
+		t.Helper()
+		var rd io.Reader
+		if body != nil {
+			b, _ := json.Marshal(body)
+			rd = bytes.NewReader(b)
+		}
+		req, _ := http.NewRequest(method, srv.URL+"/api/v1"+path, rd)
+		req.Header.Set("Content-Type", "application/json")
+		resp, err := cl.Do(req)
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer resp.Body.Close()
+		var out map[string]any
+		_ = json.NewDecoder(resp.Body).Decode(&out)
+		if resp.StatusCode != want {
+			t.Fatalf("%s %s: status %d, want %d: %v", method, path, resp.StatusCode, want, out)
+		}
+		return out
+	}
+	call("POST", "/auth/login", map[string]string{"username": "admin", "password": "a long test password"}, 200)
+	return app, call
+}
+
+// Web settings the service could not start with are refused before they
+// are saved: a restart would otherwise take the web interface and the API
+// down for good.
+func TestWebSettingsCheck(t *testing.T) {
+	app, call := signedInApp(t)
+	web := func(change func(w *WebConfig)) map[string]any {
+		w := app.store.Get().Web
+		w.HTTPListen = ""
+		change(&w)
+		return map[string]any{"web": w}
+	}
+	call("PATCH", "/settings", web(func(w *WebConfig) { w.Listen = "not-an-address" }), 400)
+	call("PATCH", "/settings", web(func(w *WebConfig) { w.SessionHours = -1 }), 400)
+	call("PATCH", "/settings", web(func(w *WebConfig) {
+		w.TLS = TLSConfig{Mode: "files", CertFile: "/nonexistent/cert.pem", KeyFile: "/nonexistent/key.pem"}
+	}), 400)
+
+	// A port another program holds is refused; a free one is saved.
+	busy, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer busy.Close()
+	call("PATCH", "/settings", web(func(w *WebConfig) { w.Listen = busy.Addr().String() }), 400)
+	free, _ := net.Listen("tcp", "127.0.0.1:0")
+	addr := free.Addr().String()
+	free.Close()
+	call("PATCH", "/settings", web(func(w *WebConfig) { w.Listen = addr; w.TLS = TLSConfig{Mode: "off"} }), 200)
+	if app.store.Get().Web.Listen != addr {
+		t.Fatal("valid listen address not saved")
+	}
+
+	// The address the service listens on now is in use by itself: fine.
+	app.webAddrs = []string{busy.Addr().String()}
+	call("PATCH", "/settings", web(func(w *WebConfig) { w.Listen = busy.Addr().String() }), 200)
+
+	// Restore runs the same check.
+	backup := app.store.Get()
+	backup.Web.Listen = "not-an-address"
+	call("POST", "/restore", backup, 400)
+}
+
+func TestRemoteIP(t *testing.T) {
+	for _, c := range []struct {
+		remote string
+		xff    []string
+		want   string
+	}{
+		{"203.0.113.5:1234", nil, "203.0.113.5"},
+		{"203.0.113.5:1234", []string{"198.51.100.1"}, "203.0.113.5"}, // not from a local proxy
+		{"127.0.0.1:1234", []string{"198.51.100.1"}, "198.51.100.1"},
+		// The client sent its own header; the proxy appended the real address.
+		{"127.0.0.1:1234", []string{"1.2.3.4, 198.51.100.1"}, "198.51.100.1"},
+		{"127.0.0.1:1234", []string{"1.2.3.4", "198.51.100.1"}, "198.51.100.1"},
+		{"127.0.0.1:1234", []string{"garbage"}, "127.0.0.1"},
+	} {
+		r := httptest.NewRequest("GET", "/", nil)
+		r.RemoteAddr = c.remote
+		for _, v := range c.xff {
+			r.Header.Add("X-Forwarded-For", v)
+		}
+		if got := remoteIP(r); got != c.want {
+			t.Errorf("%s %v: got %s, want %s", c.remote, c.xff, got, c.want)
+		}
+	}
+}
+
+// Anyone can start a passkey sign-in, so pending ones are capped per
+// address and in total.
+func TestPasskeyLoginCap(t *testing.T) {
+	a := newAuth(nil)
+	start := func(id, ip string, expires time.Time) bool {
+		a.mu.Lock()
+		defer a.mu.Unlock()
+		return a.addPasskeyLoginLocked(id, &ceremony{ip: lockKey(ip), expires: expires})
+	}
+	later := time.Now().Add(ticketTTL)
+	for i := range maxPasskeyLoginsPerIP {
+		if !start(fmt.Sprint("a", i), "198.51.100.1", later) {
+			t.Fatalf("sign-in %d refused", i)
+		}
+	}
+	if start("a-more", "198.51.100.1", later) {
+		t.Fatal("too many sign-ins from one address accepted")
+	}
+	if !start("b0", "198.51.100.2", later) {
+		t.Fatal("another address refused")
+	}
+	// Expired ones make room again.
+	a.mfa.logins = map[string]*ceremony{}
+	start("old", "198.51.100.3", time.Now().Add(-time.Second))
+	if !start("new", "198.51.100.3", later) || len(a.mfa.logins) != 1 {
+		t.Fatalf("expired sign-in not dropped: %d pending", len(a.mfa.logins))
+	}
+	// In total, the oldest makes room.
+	a.mfa.logins = map[string]*ceremony{}
+	for i := range maxPasskeyLogins {
+		start(fmt.Sprint("c", i), fmt.Sprintf("10.0.%d.%d", i/250, i%250), later.Add(time.Duration(i)*time.Millisecond))
+	}
+	start("last", "192.0.2.1", later.Add(time.Hour))
+	if _, ok := a.mfa.logins["c0"]; ok || len(a.mfa.logins) != maxPasskeyLogins {
+		t.Fatalf("cap not kept: %d pending, oldest kept %v", len(a.mfa.logins), ok)
+	}
+}
+
+func TestLanBlock(t *testing.T) {
+	got := lanBlock([]netip.Prefix{
+		netip.MustParsePrefix("192.168.1.20/24"),
+		netip.MustParsePrefix("203.0.113.9/24"), // public IPv4: not a LAN
+		netip.MustParsePrefix("2001:db8:1:2::20/64"),
+		netip.MustParsePrefix("fd00:1:2:3::20/64"),
+		netip.MustParsePrefix("fe80::1/64"),
+		netip.MustParsePrefix("2001:db8::1/32"),  // no LAN
+		netip.MustParsePrefix("192.168.1.30/24"), // same network twice
+	})
+	want := []netip.Prefix{
+		netip.MustParsePrefix("192.168.1.0/24"),
+		netip.MustParsePrefix("2001:db8:1:2::/64"),
+		netip.MustParsePrefix("fd00:1:2:3::/64"),
+	}
+	if !slices.Equal(got, want) {
+		t.Fatalf("got %v, want %v", got, want)
+	}
+}
+
+// A change that would leave no user with a password is refused: restoring
+// a backup without users, or the last users deleting each other.
+func TestNoUserLeftWithPassword(t *testing.T) {
+	app, call := signedInApp(t)
+	if err := app.store.Update(func(c *Config) error { c.Users = nil; return nil }); err == nil {
+		t.Fatal("removing every user was accepted")
+	}
+	if !app.store.Get().passwordSet() {
+		t.Fatal("password lost")
+	}
+
+	backup := app.store.Get()
+	backup.Users, backup.APITokens = nil, nil
+	call("POST", "/restore", backup, 400)
+	backup = app.store.Get()
+	backup.Version = configVersion + 1
+	call("POST", "/restore", backup, 400)
+	call("POST", "/restore", app.store.Get(), 200)
+	if !app.store.Get().passwordSet() {
+		t.Fatal("password lost")
+	}
+}
+
+// slowKernel records the configs it applied; the first apply takes a while.
+type slowKernel struct {
+	fakeKernel
+	mu      sync.Mutex
+	calls   int
+	applied []string // peer names, per apply
+}
+
+func (k *slowKernel) Apply(c *Config) error {
+	k.mu.Lock()
+	k.calls++
+	first := k.calls == 1
+	k.mu.Unlock()
+	if first {
+		time.Sleep(200 * time.Millisecond)
+	}
+	var names []string
+	for _, p := range c.Peers {
+		names = append(names, p.Name)
+	}
+	k.mu.Lock()
+	k.applied = append(k.applied, strings.Join(names, ","))
+	k.mu.Unlock()
+	return nil
+}
+
+// Applies run one at a time, so a slow apply of an older config cannot
+// finish after the newest one and undo it in the kernel.
+func TestApplyOrder(t *testing.T) {
+	store, err := openStore(filepath.Join(t.TempDir(), "config.json"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	k := &slowKernel{}
+	r := newReconciler(k, store)
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() { defer wg.Done(); _ = r.ApplyNow() }() // the old config, slowly
+	time.Sleep(50 * time.Millisecond)
+	if err := store.Update(func(c *Config) error {
+		c.Peers = append(c.Peers, Peer{ID: newID(), Name: "phone", IPv4: serverIPv4(netip.MustParsePrefix(c.Server.IPv4)).Next().String()})
+		return nil
+	}); err != nil {
+		t.Fatal(err)
+	}
+	_ = r.ApplyNow()
+	wg.Wait()
+	if last := k.applied[len(k.applied)-1]; last != "phone" {
+		t.Fatalf("the kernel ended with %q, not the newest config; applies: %q", last, k.applied)
+	}
+}

mfa.go

@@ -217,6 +217,7 @@ type ticket struct {
 
 type ceremony struct {
 	userID  string // "" for a passkey sign-in
+	ip      string // lockKey of who started a passkey sign-in
 	data    *webauthn.SessionData
 	expires time.Time
 }
@@ -551,12 +552,52 @@ func (a *App) loginPasskeyBegin(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	id := randomString(24)
+	ip := remoteIP(r)
 	a.auth.mu.Lock()
-	a.auth.mfa.logins[id] = &ceremony{data: data, expires: time.Now().Add(ticketTTL)}
+	ok := a.auth.addPasskeyLoginLocked(id, &ceremony{data: data, ip: lockKey(ip), expires: time.Now().Add(ticketTTL)})
 	a.auth.mu.Unlock()
+	if !ok {
+		writeJSON(w, http.StatusTooManyRequests, map[string]string{"error": errBusy.Error()})
+		return
+	}
 	writeJSON(w, http.StatusOK, map[string]any{"id": id, "options": opts})
 }
 
+// Anyone can start a passkey sign-in, so the pending ones are capped: per
+// address, and in total, where the oldest makes room.
+const (
+	maxPasskeyLogins      = 1000
+	maxPasskeyLoginsPerIP = 10
+)
+
+// addPasskeyLoginLocked stores a started passkey sign-in, or reports false
+// when its address has too many pending. a.mu must be held.
+func (a *Auth) addPasskeyLoginLocked(id string, c *ceremony) bool {
+	now := time.Now()
+	var fromIP int
+	var oldestID string
+	for k, x := range a.mfa.logins {
+		if now.After(x.expires) {
+			delete(a.mfa.logins, k)
+			continue
+		}
+		if x.ip == c.ip {
+			fromIP++
+		}
+		if oldestID == "" || x.expires.Before(a.mfa.logins[oldestID].expires) {
+			oldestID = k
+		}
+	}
+	if fromIP >= maxPasskeyLoginsPerIP {
+		return false
+	}
+	if len(a.mfa.logins) >= maxPasskeyLogins {
+		delete(a.mfa.logins, oldestID)
+	}
+	a.mfa.logins[id] = c
+	return true
+}
+
 func (a *App) loginPasskeyFinish(w http.ResponseWriter, r *http.Request) {
 	id := r.URL.Query().Get("id")
 	ip := remoteIP(r)

setup.go

@@ -589,7 +589,7 @@ func cmdUpdate(args []string) error {
 	if err != nil {
 		return err
 	}
-	backup := configFile + ".bak-" + oldVersion
+	backup := newUpdateBackupPath(configFile, oldVersion, time.Now())
 	step("Backing up config to %s", backup)
 	if err := copyFile(configFile, backup, 0o600, uid, gid); err != nil {
 		return err
@@ -627,6 +627,11 @@ func cmdUpdate(args []string) error {
 		}
 		return fmt.Errorf("update failed, %s %s is running again: %w", appName, oldVersion, err)
 	}
+	if n, err := pruneUpdateBackups(configFile, keepUpdateBackups); err != nil {
+		fmt.Fprintln(os.Stderr, "  Could not remove older config backups:", err)
+	} else if n > 0 {
+		step("Removed %d older config backups, kept the newest %d", n, keepUpdateBackups)
+	}
 	fmt.Printf("\nUpdated %s %s → %s.\n", appName, oldVersion, version)
 	return nil
 }

setup.js

@@ -20,6 +20,10 @@
   }
 
   // Same drawing as favicon.svg.
+  // ext opens an outside page in a new tab, marked with ↗ as in the app.
+  const ext = (href, text) => h('a', { class: 'ext', href, target: '_blank', rel: 'noopener' }, text,
+    h('span', { class: 'ar', 'aria-hidden': 'true' }, '↗'), h('span', { class: 'sr' }, ' (opens in a new tab)'));
+
   function logo(size, plain) {
     const s = document.createElementNS('http://www.w3.org/2000/svg', 'svg');
     for (const [k, v] of Object.entries({ width: size, height: size, viewBox: '0 0 64 64', 'aria-hidden': 'true' })) s.setAttribute(k, v);
@@ -108,9 +112,9 @@
       h('div', { class: 'notice' }, 'Save it now. This page can\'t be opened again: the private key exists only here and isn\'t stored anywhere.'),
       h('ol', { class: 'steps' },
         step(1, 'Install WireGuard',
-          h('p', null, h('a', { href: 'https://apps.apple.com/app/wireguard/id1441195209', rel: 'noopener' }, 'App Store'), ' · ',
-            h('a', { href: 'https://play.google.com/store/apps/details?id=com.wireguard.android', rel: 'noopener' }, 'Google Play'), ' · ',
-            h('a', { href: 'https://www.wireguard.com/install/', rel: 'noopener' }, 'Other systems'))),
+          h('p', null, ext('https://apps.apple.com/app/wireguard/id1441195209', 'App Store'), ' · ',
+            ext('https://play.google.com/store/apps/details?id=com.wireguard.android', 'Google Play'), ' · ',
+            ext('https://www.wireguard.com/install/', 'Other systems'))),
         step(2, 'Add the profile',
           h('button', { type: 'button', class: 'btn primary', onClick: download }, 'Download ' + file),
           h('p', null, 'Open the downloaded file with WireGuard, or in WireGuard tap + and choose “Create from file”.')),

speed.go

@@ -0,0 +1,134 @@
+package main
+
+import (
+	"log/slog"
+	"sync"
+	"time"
+)
+
+// Speeds keeps the last few minutes of each peer's speed in memory for the
+// Live page. It reads the kernel counters every speedStep, apart from the
+// traffic history in Stats, and never writes to disk.
+
+const (
+	speedStep   = 2 * time.Second
+	speedPoints = 60 // 2 minutes
+)
+
+// SpeedPoint is one step: per peer ID, download and upload in bits per
+// second, from the peer's point of view.
+type SpeedPoint struct {
+	T     int64               `json:"t"`
+	Peers map[string][2]int64 `json:"peers"`
+}
+
+type Speeds struct {
+	store  *Store
+	kernel Kernel
+
+	mu     sync.Mutex
+	last   map[string][2]int64 // raw rx, tx by public key
+	lastAt time.Time
+	points []SpeedPoint
+	subs   map[chan SpeedPoint]struct{}
+	done   chan struct{} // closed when Run returns
+}
+
+func newSpeeds(store *Store, kernel Kernel) *Speeds {
+	return &Speeds{store: store, kernel: kernel, last: map[string][2]int64{}, subs: map[chan SpeedPoint]struct{}{}, done: make(chan struct{})}
+}
+
+// Subscribe returns the current points and a channel that receives each new
+// one; cancel ends the subscription. A subscriber that falls behind misses
+// points rather than holding up the sampler.
+func (s *Speeds) Subscribe() (points []SpeedPoint, ch <-chan SpeedPoint, cancel func()) {
+	c := make(chan SpeedPoint, 4)
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.subs[c] = struct{}{}
+	return append([]SpeedPoint{}, s.points...), c, func() {
+		s.mu.Lock()
+		delete(s.subs, c)
+		s.mu.Unlock()
+	}
+}
+
+// Done is closed when the sampler stops, so streams can end.
+func (s *Speeds) Done() <-chan struct{} { return s.done }
+
+func (s *Speeds) sample(now time.Time) {
+	cfg := s.store.Get()
+	samples, err := s.kernel.Sample(cfg.Server.Interface)
+	if err != nil {
+		slog.Debug("speed sample failed", "err", err)
+		return
+	}
+	idByKey := map[string]string{}
+	for _, p := range cfg.Peers {
+		if p.hasKey() {
+			idByKey[p.PublicKey] = p.ID
+		}
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	secs := now.Sub(s.lastAt).Seconds()
+	first := s.lastAt.IsZero()
+	cur := map[string][2]int64{}
+	pt := SpeedPoint{T: now.Unix(), Peers: map[string][2]int64{}}
+	for _, smp := range samples {
+		cur[smp.PublicKey] = [2]int64{smp.RxBytes, smp.TxBytes}
+		id := idByKey[smp.PublicKey]
+		prev, ok := s.last[smp.PublicKey]
+		if id == "" || !ok || first {
+			continue
+		}
+		dRx, dTx := smp.RxBytes-prev[0], smp.TxBytes-prev[1]
+		if dRx < 0 || dTx < 0 { // counters were reset
+			continue
+		}
+		// Tx is what the server sent: the peer's download.
+		pt.Peers[id] = [2]int64{int64(float64(dTx*8) / secs), int64(float64(dRx*8) / secs)}
+	}
+	s.last, s.lastAt = cur, now
+	if first {
+		return
+	}
+	s.points = append(s.points, pt)
+	if len(s.points) > speedPoints {
+		s.points = s.points[len(s.points)-speedPoints:]
+	}
+	for c := range s.subs {
+		select {
+		case c <- pt:
+		default:
+		}
+	}
+}
+
+// Since returns the points newer than the unix time t, oldest first.
+func (s *Speeds) Since(t int64) []SpeedPoint {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	out := []SpeedPoint{}
+	for _, p := range s.points {
+		if p.T > t {
+			out = append(out, p)
+		}
+	}
+	return out
+}
+
+func (s *Speeds) Run(stop <-chan struct{}) {
+	defer close(s.done)
+	s.sample(time.Now())
+	t := time.NewTicker(speedStep)
+	defer t.Stop()
+	for {
+		select {
+		case <-stop:
+			return
+		case now := <-t.C:
+			s.sample(now)
+		}
+	}
+}

update.go

@@ -0,0 +1,224 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"log/slog"
+	"net/http"
+	"runtime"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+// The update check asks one of the two places releases are published for
+// the latest one. Both carry the same tags and files.
+var updateSources = map[string]struct {
+	Name string // shown in the web interface
+	API  string // latest release, as JSON
+	Repo string // web page of the repository; downloads are under it
+}{
+	"gitea":  {"Gitea", "https://git.redetzke.aero/api/v1/repos/Redetzke/GHOSTWIRE/releases/latest", "https://git.redetzke.aero/Redetzke/GHOSTWIRE"},
+	"github": {"GitHub", "https://api.github.com/repos/danielredetzke/GHOSTWIRE/releases/latest", "https://github.com/danielredetzke/GHOSTWIRE"},
+}
+
+const updateCheckFreq = 24 * time.Hour
+
+// Release is the latest published release as the source reports it.
+type Release struct {
+	Version   string    `json:"version"` // tag, e.g. "v0.4.0"
+	Published time.Time `json:"published"`
+	Notes     string    `json:"notes"` // Markdown
+	URL       string    `json:"url"`   // release page
+}
+
+// UpdateStatus is shown in the settings; Available also reaches the sidebar
+// and the Dashboard through /auth/me.
+type UpdateStatus struct {
+	Enabled   bool       `json:"enabled"`
+	Source    string     `json:"source"`
+	Current   string     `json:"current"`
+	Latest    *Release   `json:"latest"`
+	Available bool       `json:"available"` // Latest is newer than Current
+	Checked   *time.Time `json:"checked"`   // last attempt
+	Error     string     `json:"error,omitempty"`
+	LastOK    *time.Time `json:"lastOk"` // last attempt that worked
+	// Download links for this server's platform; empty when no release
+	// file is built for it.
+	Arch      string `json:"arch"`
+	File      string `json:"file,omitempty"`
+	FileURL   string `json:"fileUrl,omitempty"`
+	SumsURL   string `json:"sumsUrl,omitempty"`
+	SourceURL string `json:"sourceUrl"` // repository page of the source
+}
+
+type Updater struct {
+	enabled atomic.Bool
+	kick    chan struct{}
+	fetch   func(ctx context.Context, url string) (*Release, error) // replaced in tests
+
+	mu      sync.Mutex
+	source  string
+	latest  *Release
+	checked *time.Time
+	lastOK  *time.Time
+	err     string
+}
+
+func newUpdater(c UpdatesConfig) *Updater {
+	u := &Updater{kick: make(chan struct{}, 1), fetch: fetchRelease, source: c.Source}
+	u.enabled.Store(c.checkEnabled())
+	return u
+}
+
+// Set applies the settings. A new source or switching the check on checks
+// at once; switching it off forgets what the last check found.
+func (u *Updater) Set(c UpdatesConfig) {
+	if u == nil {
+		return
+	}
+	on := c.checkEnabled()
+	u.mu.Lock()
+	changed := u.source != c.Source || u.enabled.Load() != on
+	if u.source != c.Source || !on {
+		u.latest, u.checked, u.lastOK, u.err = nil, nil, nil, ""
+	}
+	u.source = c.Source
+	u.enabled.Store(on)
+	u.mu.Unlock()
+	if changed && on {
+		select {
+		case u.kick <- struct{}{}:
+		default:
+		}
+	}
+}
+
+// Run checks once a day while the check is on.
+func (u *Updater) Run(stop <-chan struct{}) {
+	t := time.NewTicker(updateCheckFreq)
+	defer t.Stop()
+	for {
+		if u.enabled.Load() {
+			u.Check(context.Background())
+		}
+		select {
+		case <-stop:
+			return
+		case <-t.C:
+		case <-u.kick:
+		}
+	}
+}
+
+// Check asks the source for the latest release now.
+func (u *Updater) Check(ctx context.Context) {
+	u.mu.Lock()
+	source := u.source
+	u.mu.Unlock()
+	ctx, cancel := context.WithTimeout(ctx, 30*time.Second)
+	defer cancel()
+	rel, err := u.fetch(ctx, updateSources[source].API)
+	now := time.Now()
+	u.mu.Lock()
+	defer u.mu.Unlock()
+	if u.source != source { // the source changed meanwhile; that check counts
+		return
+	}
+	u.checked = &now
+	if err != nil {
+		u.err = err.Error()
+		slog.Warn("update check failed", "source", source, "err", err)
+		return
+	}
+	u.latest, u.lastOK, u.err = rel, &now, ""
+	if newerVersion(rel.Version, version) {
+		slog.Info("update available", "version", rel.Version, "running", version)
+	}
+}
+
+func (u *Updater) Status() UpdateStatus {
+	if u == nil {
+		return UpdateStatus{Current: version}
+	}
+	u.mu.Lock()
+	defer u.mu.Unlock()
+	src := updateSources[u.source]
+	st := UpdateStatus{
+		Enabled: u.enabled.Load(), Source: u.source, Current: version, Latest: u.latest,
+		Checked: u.checked, Error: u.err, LastOK: u.lastOK, Arch: releaseArch(), SourceURL: src.Repo,
+	}
+	if u.latest != nil {
+		st.Available = newerVersion(u.latest.Version, version)
+		if st.Arch != "" {
+			st.File = fmt.Sprintf("%s-%s-linux-%s", appName, u.latest.Version, st.Arch)
+			base := src.Repo + "/releases/download/" + u.latest.Version + "/"
+			st.FileURL, st.SumsURL = base+st.File, base+"SHA256SUMS"
+		}
+	}
+	return st
+}
+
+// Available returns the newer release's version, or "".
+func (u *Updater) Available() string {
+	if st := u.Status(); st.Enabled && st.Available {
+		return st.Latest.Version
+	}
+	return ""
+}
+
+// releaseArch names this platform the way the release files do, or "" when
+// no file is built for it.
+func releaseArch() string {
+	if runtime.GOOS != "linux" {
+		return ""
+	}
+	switch runtime.GOARCH {
+	case "amd64", "arm64":
+		return runtime.GOARCH
+	case "arm":
+		return "armv7"
+	}
+	return ""
+}
+
+func fetchRelease(ctx context.Context, url string) (*Release, error) {
+	req, _ := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	req.Header.Set("Accept", "application/json")
+	req.Header.Set("User-Agent", appName+"/"+strings.TrimPrefix(version, "v"))
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("HTTP %d from %s", resp.StatusCode, req.URL.Host)
+	}
+	// GitHub and Gitea name these fields the same.
+	var r struct {
+		Tag        string    `json:"tag_name"`
+		Body       string    `json:"body"`
+		Published  time.Time `json:"published_at"`
+		URL        string    `json:"html_url"`
+		Draft      bool      `json:"draft"`
+		Prerelease bool      `json:"prerelease"`
+	}
+	if err := json.NewDecoder(io.LimitReader(resp.Body, 1<<20)).Decode(&r); err != nil {
+		return nil, fmt.Errorf("unreadable answer from %s: %w", req.URL.Host, err)
+	}
+	if _, ok := compareVersions(r.Tag, r.Tag); r.Draft || r.Prerelease || !ok {
+		return nil, errors.New("the latest release is not a published version")
+	}
+	return &Release{Version: r.Tag, Published: r.Published, Notes: r.Body, URL: r.URL}, nil
+}
+
+// newerVersion reports whether latest is a higher version than running.
+// A running version that is not a version number is never out of date.
+func newerVersion(latest, running string) bool {
+	c, ok := compareVersions(latest, running)
+	return ok && c > 0
+}

update_test.go

@@ -0,0 +1,111 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+func TestNewerVersion(t *testing.T) {
+	for _, tc := range []struct {
+		latest, running string
+		want            bool
+	}{
+		{"v0.4.0", "v0.3.2", true},
+		{"v0.4.0", "0.3.2", true},
+		{"v0.10.0", "v0.9.9", true},
+		{"v1.0.0", "v0.99.0", true},
+		{"v0.4.0", "v0.4.0", false},
+		{"v0.4.0", "v0.4.0-3-gb18d16a", false}, // a build after the release
+		{"v0.3.2", "v0.4.0", false},
+		{"v0.4.0", "dev", false}, // not a version: never out of date
+		{"latest", "v0.3.2", false},
+	} {
+		if got := newerVersion(tc.latest, tc.running); got != tc.want {
+			t.Errorf("newerVersion(%q, %q) = %v, want %v", tc.latest, tc.running, got, tc.want)
+		}
+	}
+}
+
+func TestFetchRelease(t *testing.T) {
+	var body string
+	var status int
+	var ua string
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		ua = r.Header.Get("User-Agent")
+		w.WriteHeader(status)
+		_, _ = w.Write([]byte(body))
+	}))
+	defer srv.Close()
+
+	status, body = 200, `{"tag_name":"v0.4.0","body":"Fixes.","published_at":"2026-10-05T06:15:28Z","html_url":"https://example.net/r/v0.4.0","draft":false,"prerelease":false}`
+	r, err := fetchRelease(context.Background(), srv.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if r.Version != "v0.4.0" || r.Notes != "Fixes." || r.URL != "https://example.net/r/v0.4.0" || r.Published.IsZero() {
+		t.Fatalf("release = %+v", r)
+	}
+	if !strings.HasPrefix(ua, appName+"/") {
+		t.Errorf("User-Agent = %q", ua)
+	}
+
+	status, body = 200, `{"tag_name":"v0.5.0-rc1","prerelease":true}`
+	if _, err := fetchRelease(context.Background(), srv.URL); err == nil {
+		t.Error("a pre-release was accepted")
+	}
+	status, body = 404, `{}`
+	if _, err := fetchRelease(context.Background(), srv.URL); err == nil || !strings.Contains(err.Error(), "404") {
+		t.Errorf("HTTP 404: err = %v", err)
+	}
+}
+
+func TestUpdater(t *testing.T) {
+	old := version
+	version = "v0.3.2"
+	defer func() { version = old }()
+
+	u := newUpdater(UpdatesConfig{Source: "gitea"})
+	var asked string
+	u.fetch = func(_ context.Context, url string) (*Release, error) {
+		asked = url
+		return &Release{Version: "v0.4.0"}, nil
+	}
+	u.Check(context.Background())
+	if asked != updateSources["gitea"].API {
+		t.Errorf("asked %q", asked)
+	}
+	st := u.Status()
+	if !st.Available || u.Available() != "v0.4.0" || st.Checked == nil || st.LastOK == nil {
+		t.Fatalf("status = %+v", st)
+	}
+	if st.Arch != "" {
+		want := "https://git.redetzke.aero/Redetzke/GHOSTWIRE/releases/download/v0.4.0/GHOSTWIRE-v0.4.0-linux-" + st.Arch
+		if st.FileURL != want || !strings.HasSuffix(st.SumsURL, "/v0.4.0/SHA256SUMS") {
+			t.Errorf("downloads = %q, %q", st.FileURL, st.SumsURL)
+		}
+	}
+
+	// A failed check keeps the last good answer and reports the error.
+	u.fetch = func(context.Context, string) (*Release, error) { return nil, errors.New("no route to host") }
+	u.Check(context.Background())
+	if st := u.Status(); st.Error != "no route to host" || st.Latest == nil {
+		t.Errorf("after a failed check: %+v", st)
+	}
+
+	// Another source forgets what the old one said; switching off hides it.
+	u.Set(UpdatesConfig{Source: "github"})
+	if st := u.Status(); st.Latest != nil || st.Error != "" || st.SourceURL != updateSources["github"].Repo {
+		t.Errorf("after changing the source: %+v", st)
+	}
+	off := false
+	u.fetch = func(context.Context, string) (*Release, error) { return &Release{Version: "v0.4.0"}, nil }
+	u.Check(context.Background())
+	u.Set(UpdatesConfig{Source: "github", Check: &off})
+	if u.Available() != "" || u.Status().Enabled {
+		t.Error("still reports an update with the check off")
+	}
+}

updatebackups.go

@@ -0,0 +1,125 @@
+package main
+
+import (
+	"errors"
+	"io/fs"
+	"net/http"
+	"os"
+	"path/filepath"
+	"regexp"
+	"slices"
+	"strings"
+	"time"
+)
+
+// Each update copies config.json to config.json.bak-<old version> next to
+// it, in case the new version must be rolled back. The copies hold the same
+// secrets as a backup, so the web interface lists them and can remove them,
+// and update keeps only the newest few.
+
+const keepUpdateBackups = 3
+
+type UpdateBackup struct {
+	Name     string    `json:"name"`
+	Version  string    `json:"version"`
+	Modified time.Time `json:"modified"`
+	Size     int64     `json:"size"`
+}
+
+// A copy that would overwrite an older one gets the time appended.
+var backupStampRe = regexp.MustCompile(`-\d{8}-\d{4}$`)
+
+func updateBackupPrefix(configPath string) string { return filepath.Base(configPath) + ".bak-" }
+
+// newUpdateBackupPath names the copy update makes of configPath.
+func newUpdateBackupPath(configPath, version string, now time.Time) string {
+	p := configPath + ".bak-" + version
+	if _, err := os.Lstat(p); err == nil {
+		p += now.Format("-20060102-1504")
+	}
+	return p
+}
+
+// listUpdateBackups returns the copies next to configPath, newest first.
+func listUpdateBackups(configPath string) ([]UpdateBackup, error) {
+	entries, err := os.ReadDir(filepath.Dir(configPath))
+	if err != nil {
+		return nil, err
+	}
+	prefix := updateBackupPrefix(configPath)
+	out := []UpdateBackup{}
+	for _, e := range entries {
+		name := e.Name()
+		if !e.Type().IsRegular() || !strings.HasPrefix(name, prefix) || name == prefix {
+			continue
+		}
+		fi, err := e.Info()
+		if err != nil {
+			continue
+		}
+		out = append(out, UpdateBackup{Name: name, Version: backupStampRe.ReplaceAllString(strings.TrimPrefix(name, prefix), ""),
+			Modified: fi.ModTime(), Size: fi.Size()})
+	}
+	slices.SortFunc(out, func(a, b UpdateBackup) int { return b.Modified.Compare(a.Modified) })
+	return out, nil
+}
+
+// removeUpdateBackup deletes one copy; any other name is refused.
+func removeUpdateBackup(configPath, name string) error {
+	prefix := updateBackupPrefix(configPath)
+	path := filepath.Join(filepath.Dir(configPath), name)
+	fi, err := os.Lstat(path)
+	if !strings.HasPrefix(name, prefix) || name == prefix || strings.ContainsAny(name, `/\`) ||
+		errors.Is(err, fs.ErrNotExist) || (err == nil && !fi.Mode().IsRegular()) {
+		return badRequest("no copy named %q", name)
+	}
+	if err != nil {
+		return err
+	}
+	return os.Remove(path)
+}
+
+// pruneUpdateBackups keeps the newest keep copies and deletes the rest.
+func pruneUpdateBackups(configPath string, keep int) (int, error) {
+	list, err := listUpdateBackups(configPath)
+	if err != nil || len(list) <= keep {
+		return 0, err
+	}
+	n := 0
+	for _, b := range list[keep:] {
+		if err := removeUpdateBackup(configPath, b.Name); err != nil {
+			return n, err
+		}
+		n++
+	}
+	return n, nil
+}
+
+func (a *App) listUpdateBackups(w http.ResponseWriter, r *http.Request) {
+	list, err := listUpdateBackups(a.store.path)
+	if err != nil {
+		writeErr(w, err)
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]any{"backups": list})
+}
+
+func (a *App) removeUpdateBackup(w http.ResponseWriter, r *http.Request) {
+	name := r.PathValue("name")
+	if err := removeUpdateBackup(a.store.path, name); err != nil {
+		writeErr(w, err)
+		return
+	}
+	a.audit(r, "update backup removed", "file", name)
+	writeJSON(w, http.StatusOK, map[string]any{"ok": true})
+}
+
+func (a *App) removeUpdateBackups(w http.ResponseWriter, r *http.Request) {
+	n, err := pruneUpdateBackups(a.store.path, 0)
+	if err != nil {
+		writeErr(w, err)
+		return
+	}
+	a.audit(r, "update backups removed", "count", n)
+	writeJSON(w, http.StatusOK, map[string]any{"ok": true, "removed": n})
+}

updatebackups_test.go

@@ -0,0 +1,65 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestUpdateBackups(t *testing.T) {
+	dir := t.TempDir()
+	cfg := filepath.Join(dir, "config.json")
+	_ = os.WriteFile(cfg, []byte("{}"), 0o600)
+	now := time.Date(2026, 10, 5, 12, 9, 0, 0, time.UTC)
+
+	// A second copy of the same version gets the time appended instead of
+	// overwriting the first.
+	first := newUpdateBackupPath(cfg, "unknown", now)
+	if filepath.Base(first) != "config.json.bak-unknown" {
+		t.Fatalf("first copy: %s", first)
+	}
+	_ = os.WriteFile(first, []byte("{}"), 0o600)
+	second := newUpdateBackupPath(cfg, "unknown", now)
+	if filepath.Base(second) != "config.json.bak-unknown-20261005-1209" {
+		t.Fatalf("second copy: %s", second)
+	}
+	_ = os.WriteFile(second, []byte("{}"), 0o600)
+	for i, v := range []string{"v0.2.0", "v0.3.0", "v0.4.0"} {
+		f := filepath.Join(dir, "config.json.bak-"+v)
+		_ = os.WriteFile(f, []byte("{}"), 0o600)
+		_ = os.Chtimes(f, now, now.Add(time.Duration(i+1)*time.Hour))
+	}
+	_ = os.Chtimes(first, now, now.Add(-2*time.Hour))
+	_ = os.Chtimes(second, now, now.Add(-time.Hour))
+	_ = os.Mkdir(filepath.Join(dir, "config.json.bak-dir"), 0o700) // not a file: ignored
+
+	list, err := listUpdateBackups(cfg)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var got []string
+	for _, b := range list {
+		got = append(got, b.Version)
+	}
+	if strings.Join(got, " ") != "v0.4.0 v0.3.0 v0.2.0 unknown unknown" {
+		t.Fatalf("versions, newest first: %v", got)
+	}
+
+	for _, bad := range []string{"config.json", "config.json.bak-", "config.json.bak-dir", "../config.json.bak-v0.4.0", "config.json.bak-v0.4.0/x"} {
+		if err := removeUpdateBackup(cfg, bad); err == nil {
+			t.Errorf("removed %q", bad)
+		}
+	}
+
+	if n, err := pruneUpdateBackups(cfg, keepUpdateBackups); err != nil || n != 2 {
+		t.Fatalf("prune: %d, %v", n, err)
+	}
+	if list, _ = listUpdateBackups(cfg); len(list) != 3 || list[2].Version != "v0.2.0" {
+		t.Fatalf("after prune: %v", list)
+	}
+	if _, err := os.Stat(cfg); err != nil {
+		t.Fatal("config.json is gone")
+	}
+}