control/controlclient, ipn/ipnlocal, tailcfg: add MapResponse.PopBrowserURL

Updates #3802

Change-Id: I89481fc5782a0cc8084354706f8f28d94f197325
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

control/controlclient/direct.go

@@ -69,6 +69,7 @@ type Direct struct {
 	keepSharerAndUserSplit bool
 	skipIPForwardingCheck  bool
 	pinger                 Pinger
+	popBrowser             func(url string) // or nil
 
 	mu             sync.Mutex        // mutex guards the following fields
 	serverKey      key.MachinePublic // original ("legacy") nacl crypto_box-based public key
@@ -103,6 +104,7 @@ type Options struct {
 	HTTPTestClient       *http.Client     // optional HTTP client to use (for tests only)
 	DebugFlags           []string         // debug settings to send to control
 	LinkMonitor          *monitor.Mon     // optional link monitor
+	PopBrowserURL        func(url string) // optional func to open browser
 
 	// KeepSharerAndUserSplit controls whether the client
 	// understands Node.Sharer. If false, the Sharer is mapped to the User.
@@ -198,6 +200,7 @@ func NewDirect(opts Options) (*Direct, error) {
 		linkMon:                opts.LinkMonitor,
 		skipIPForwardingCheck:  opts.SkipIPForwardingCheck,
 		pinger:                 opts.Pinger,
+		popBrowser:             opts.PopBrowserURL,
 	}
 	if opts.Hostinfo == nil {
 		c.SetHostinfo(hostinfo.New())
@@ -849,7 +852,15 @@ func (c *Direct) sendMapRequest(ctx context.Context, maxPolls int, cb func(*netm
 			metricMapResponsePings.Add(1)
 			go answerPing(c.logf, c.httpc, pr)
 		}
-
+		if u := resp.PopBrowserURL; u != "" && u != sess.lastPopBrowserURL {
+			sess.lastPopBrowserURL = u
+			if c.popBrowser != nil {
+				c.logf("netmap: control says to open URL %v; opening...", u)
+				c.popBrowser(u)
+			} else {
+				c.logf("netmap: control says to open URL %v; no popBrowser func", u)
+			}
+		}
 		if resp.ControlTime != nil && !resp.ControlTime.IsZero() {
 			c.logf.JSON(1, "controltime", resp.ControlTime.UTC())
 		}
@@ -858,6 +869,7 @@ func (c *Direct) sendMapRequest(ctx context.Context, maxPolls int, cb func(*netm
 		} else {
 			vlogf("netmap: got new map")
 		}
+
 		select {
 		case timeoutReset <- struct{}{}:
 			vlogf("netmap: sent timer reset")

control/controlclient/map.go

@@ -44,6 +44,7 @@ type mapSession struct {
 	previousPeers          []*tailcfg.Node // for delta-purposes
 	lastDomain             string
 	lastHealth             []string
+	lastPopBrowserURL      string
 
 	// netMapBuilding is non-nil during a netmapForResponse call,
 	// containing the value to be returned, once fully populated.

ipn/ipnlocal/local.go

@@ -973,6 +973,7 @@ func (b *LocalBackend) Start(opts ipn.Options) error {
 		DebugFlags:           debugFlags,
 		LinkMonitor:          b.e.GetLinkMonitor(),
 		Pinger:               b.e,
+		PopBrowserURL:        b.tellClientToBrowseToURL,
 
 		// Don't warn about broken Linux IP forwarding when
 		// netstack is being used.
@@ -1370,12 +1371,18 @@ func (b *LocalBackend) popBrowserAuthNow() {
 
 	b.blockEngineUpdates(true)
 	b.stopEngineAndWait()
-	b.send(ipn.Notify{BrowseToURL: &url})
+	b.tellClientToBrowseToURL(url)
 	if b.State() == ipn.Running {
 		b.enterState(ipn.Starting)
 	}
 }
 
+func (b *LocalBackend) tellClientToBrowseToURL(url string) {
+	if url != "" {
+		b.send(ipn.Notify{BrowseToURL: &url})
+	}
+}
+
 // For testing lazy machine key generation.
 var panicOnMachineKeyGeneration = envknob.Bool("TS_DEBUG_PANIC_MACHINE_KEY")
 

tailcfg/tailcfg.go

@@ -65,7 +65,8 @@ type CapabilityVersion int
 //    26: 2022-01-12: (nothing, just bumping for 1.20.0)
 //    27: 2022-02-18: start of SSHPolicy being respected
 //    28: 2022-03-09: client can communicate over Noise.
-const CurrentCapabilityVersion CapabilityVersion = 28
+//    29: 2022-03-09: MapResponse.PopBrowserURL
+const CurrentCapabilityVersion CapabilityVersion = 29
 
 type StableID string
 
@@ -1221,7 +1222,7 @@ type PingRequest struct {
 type MapResponse struct {
 	// KeepAlive, if set, represents an empty message just to keep
 	// the connection alive. When true, all other fields except
-	// PingRequest are ignored.
+	// PingRequest, ControlTime, and PopBrowserURL are ignored.
 	KeepAlive bool `json:",omitempty"`
 
 	// PingRequest, if non-empty, is a request to the client to
@@ -1231,6 +1232,11 @@ type MapResponse struct {
 	// KeepAlive true or false).
 	PingRequest *PingRequest `json:",omitempty"`
 
+	// PopBrowserURL, if non-empty, is a URL for the client to
+	// open to complete an action. The client should dup suppress
+	// identical URLs and only open it once for the same URL.
+	PopBrowserURL string
+
 	// Networking
 
 	// Node describes the node making the map request.