controlclient,tailcfg,types: expose MaxKeyDuration via localapi (#10401)

Updates tailscale/corp#16016

Signed-off-by: James Sanderson <jsanderson@tailscale.com>

control/controlclient/direct.go

@@ -1044,7 +1044,7 @@ func (c *Direct) sendMapRequest(ctx context.Context, isStreaming bool, nu Netmap
 
 		var resp tailcfg.MapResponse
 		if err := c.decodeMsg(msg, &resp, machinePrivKey); err != nil {
-			vlogf("netmap: decode error: %v")
+			vlogf("netmap: decode error: %v", err)
 			return err
 		}
 		watchdogTimer.Stop()

control/controlclient/map.go

@@ -87,6 +87,7 @@ type mapSession struct {
 	lastPopBrowserURL      string
 	lastTKAInfo            *tailcfg.TKAInfo
 	lastNetmapSummary      string // from NetworkMap.VeryConcise
+	lastMaxExpiry          time.Duration
 }
 
 // newMapSession returns a mostly unconfigured new mapSession.
@@ -319,6 +320,9 @@ func (ms *mapSession) updateStateFromResponse(resp *tailcfg.MapResponse) {
 	if resp.TKAInfo != nil {
 		ms.lastTKAInfo = resp.TKAInfo
 	}
+	if resp.MaxKeyDuration > 0 {
+		ms.lastMaxExpiry = resp.MaxKeyDuration
+	}
 }
 
 var (
@@ -763,6 +767,7 @@ func (ms *mapSession) netmap() *netmap.NetworkMap {
 		DERPMap:           ms.lastDERPMap,
 		ControlHealth:     ms.lastHealth,
 		TKAEnabled:        ms.lastTKAInfo != nil && !ms.lastTKAInfo.Disabled,
+		MaxKeyDuration:    ms.lastMaxExpiry,
 	}
 
 	if ms.lastTKAInfo != nil && ms.lastTKAInfo.Head != "" {