tailcfg, ipn, controlclient: add MapResponse.ClientVersion, plumb to IPN bus

Updates #6480

Change-Id: I6321071425cd091148d8140d1eb24dd536bb7984
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

control/controlclient/direct.go

@@ -76,6 +76,7 @@ type Direct struct {
 	pinger                 Pinger
 	popBrowser             func(url string)             // or nil
 	c2nHandler             http.Handler                 // or nil
+	onClientVersion        func(*tailcfg.ClientVersion) // or nil
 
 	dialPlan ControlDialPlanner // can be nil
 
@@ -114,6 +115,7 @@ type Options struct {
 	DebugFlags           []string                     // debug settings to send to control
 	LinkMonitor          *monitor.Mon                 // optional link monitor
 	PopBrowserURL        func(url string)             // optional func to open browser
+	OnClientVersion      func(*tailcfg.ClientVersion) // optional func to inform GUI of client version status
 	Dialer               *tsdial.Dialer               // non-nil
 	C2NHandler           http.Handler                 // or nil
 
@@ -241,6 +243,7 @@ func NewDirect(opts Options) (*Direct, error) {
 		skipIPForwardingCheck:  opts.SkipIPForwardingCheck,
 		pinger:                 opts.Pinger,
 		popBrowser:             opts.PopBrowserURL,
+		onClientVersion:        opts.OnClientVersion,
 		c2nHandler:             opts.C2NHandler,
 		dialer:                 opts.Dialer,
 		dialPlan:               opts.DialPlan,
@@ -1008,6 +1011,9 @@ func (c *Direct) sendMapRequest(ctx context.Context, maxPolls int, readOnly bool
 				c.logf("netmap: control says to open URL %v; no popBrowser func", u)
 			}
 		}
+		if resp.ClientVersion != nil && c.onClientVersion != nil {
+			c.onClientVersion(resp.ClientVersion)
+		}
 		if resp.ControlTime != nil && !resp.ControlTime.IsZero() {
 			c.logf.JSON(1, "controltime", resp.ControlTime.UTC())
 		}

ipn/backend.go

@@ -95,6 +95,10 @@ type Notify struct {
 	// macOS Network Extension.
 	LocalTCPPort *uint16 `json:",omitempty"`
 
+	// ClientVersion, if non-nil, describes whether a client version update
+	// is available.
+	ClientVersion *tailcfg.ClientVersion `json:",omitempty"`
+
 	// type is mirrored in xcode/Shared/IPN.swift
 }
 

ipn/ipnlocal/local.go

@@ -1271,6 +1271,7 @@ func (b *LocalBackend) Start(opts ipn.Options) error {
 		LinkMonitor:          b.e.GetLinkMonitor(),
 		Pinger:               b,
 		PopBrowserURL:        b.tellClientToBrowseToURL,
+		OnClientVersion:      b.onClientVersion,
 		Dialer:               b.Dialer(),
 		Status:               b.setClientStatus,
 		C2NHandler:           http.HandlerFunc(b.handleC2N),
@@ -1836,6 +1837,21 @@ func (b *LocalBackend) tellClientToBrowseToURL(url string) {
 	}
 }
 
+// onClientVersion is called on MapResponse updates when a MapResponse contains
+// a non-nil ClientVersion message.
+func (b *LocalBackend) onClientVersion(v *tailcfg.ClientVersion) {
+	switch runtime.GOOS {
+	case "darwin", "ios":
+		// These auto-update well enough, and we haven't converted the
+		// ClientVersion types to Swift yet, so don't send them in ipn.Notify
+		// messages.
+	default:
+		// But everything else is a Go client and can deal with this field, even
+		// if they ignore it.
+		b.send(ipn.Notify{ClientVersion: v})
+	}
+}
+
 // For testing lazy machine key generation.
 var panicOnMachineKeyGeneration = envknob.RegisterBool("TS_DEBUG_PANIC_MACHINE_KEY")
 

tailcfg/tailcfg.go

@@ -1425,6 +1425,40 @@ type MapResponse struct {
 	// server. An initial nil is equivalent to new(ControlDialPlan).
 	// A subsequent streamed nil means no change.
 	ControlDialPlan *ControlDialPlan `json:",omitempty"`
+
+	// ClientVersion describes the latest client version that's available for
+	// download and whether the client is using it. A nil value means no change
+	// or nothing to report.
+	ClientVersion *ClientVersion `json:",omitempty"`
+}
+
+// ClientVersion is information about the latest client version that's available
+// for the client (and whether they're already running it).
+//
+// It does not include a URL to download the client, as that varies by platform.
+type ClientVersion struct {
+	// RunningLatest is true if the client is running the latest build.
+	RunningLatest bool `json:",omitempty"`
+
+	// LatestVersion is the latest version.Short ("1.34.2") version available
+	// for download for the client's platform and packaging type.
+	// It won't be populated if RunningLatest is true.
+	// The primary purpose of the LatestVersion value is to invalidate the client's
+	// cache update check value, if any. This primarily applies to Windows.
+	LatestVersion string `json:",omitempty"`
+
+	// Notify is whether the client should do an OS-specific notification about
+	// a new version being available. This should not be populated if
+	// RunningLatest is true. The client should not notify multiple times for
+	// the same LatestVersion value.
+	Notify bool `json:",omitempty"`
+
+	// NotifyURL is a URL to open in the browser when the user clicks on the
+	// notification, when Notify is true.
+	NotifyURL string `json:",omitempty"`
+
+	// NotifyText is the text to show in the notification, when Notify is true.
+	NotifyText string `json:",omitempty"`
 }
 
 // ControlDialPlan is instructions from the control server to the client on how