wgengine/netstack: use tailscale IPs instead of a hardcoded one (#1131)

Signed-off-by: Naman Sood <mail@nsood.in>

wgengine/userspace.go

@@ -111,15 +111,16 @@ type userspaceEngine struct {
 	sentActivityAt      map[netaddr.IP]*int64     // value is atomic int64 of unixtime
 	destIPActivityFuncs map[netaddr.IP]func()
 
-	mu                 sync.Mutex // guards following; see lock order comment below
-	closing            bool       // Close was called (even if we're still closing)
-	statusCallback     StatusCallback
-	linkChangeCallback func(major bool, newState *interfaces.State)
-	peerSequence       []wgkey.Key
-	endpoints          []string
-	pingers            map[wgkey.Key]*pinger // legacy pingers for pre-discovery peers
-	linkState          *interfaces.State
-	pendOpen           map[flowtrack.Tuple]*pendingOpenFlow // see pendopen.go
+	mu                  sync.Mutex // guards following; see lock order comment below
+	closing             bool       // Close was called (even if we're still closing)
+	statusCallback      StatusCallback
+	linkChangeCallback  func(major bool, newState *interfaces.State)
+	peerSequence        []wgkey.Key
+	endpoints           []string
+	pingers             map[wgkey.Key]*pinger // legacy pingers for pre-discovery peers
+	linkState           *interfaces.State
+	pendOpen            map[flowtrack.Tuple]*pendingOpenFlow // see pendopen.go
+	networkMapCallbacks map[*someHandle]NetworkMapCallback
 
 	// Lock ordering: magicsock.Conn.mu, wgLock, then mu.
 }
@@ -1290,6 +1291,21 @@ func (e *userspaceEngine) SetLinkChangeCallback(cb func(major bool, newState *in
 	}
 }
 
+func (e *userspaceEngine) AddNetworkMapCallback(cb NetworkMapCallback) func() {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	if e.networkMapCallbacks == nil {
+		e.networkMapCallbacks = make(map[*someHandle]NetworkMapCallback)
+	}
+	h := new(someHandle)
+	e.networkMapCallbacks[h] = cb
+	return func() {
+		e.mu.Lock()
+		defer e.mu.Unlock()
+		delete(e.networkMapCallbacks, h)
+	}
+}
+
 func getLinkState() (*interfaces.State, error) {
 	s, err := interfaces.GetState()
 	if s != nil {
@@ -1308,6 +1324,15 @@ func (e *userspaceEngine) SetDERPMap(dm *tailcfg.DERPMap) {
 
 func (e *userspaceEngine) SetNetworkMap(nm *controlclient.NetworkMap) {
 	e.magicConn.SetNetworkMap(nm)
+	e.mu.Lock()
+	callbacks := make([]NetworkMapCallback, 0, 4)
+	for _, fn := range e.networkMapCallbacks {
+		callbacks = append(callbacks, fn)
+	}
+	e.mu.Unlock()
+	for _, fn := range callbacks {
+		fn(nm)
+	}
 }
 
 func (e *userspaceEngine) DiscoPublicKey() tailcfg.DiscoKey {