More reliable full tunnel on macOs

This makes switching between physical networks
with full tunnel mode enabled more reliable.
There were issues with the physical default route or device
changing.

osdep/ManagedRoute.cpp

@@ -484,58 +484,57 @@ bool ManagedRoute::sync()
 
 
 	if (!hasRoute) {
-		if (_target && _target.netmaskBits() == 0) {
+		if (_target && _target.netmaskBits() == 0) { // Allow Default
 			InetAddress newSystemVia;
 			char newSystemDevice[128];
 			newSystemDevice[0] = (char)0;
 
-			// If macos has a network hiccup, it deletes what _systemVia we had set.
-			// Then we don't know how to set the default route again.
-			// So use the one we had set previously. Don't overwrite it.
-			if (!_systemVia) {
-				// Find system default route that this route should override
-				// We need to put it back when default route is turned off
-				for(std::vector<_RTE>::iterator r(rtes.begin());r!=rtes.end();++r) {
-					if (r->via) {
-						if ( !_systemVia && r->isDefault == 1 && (strcmp(r->device,_device) != 0) ) {
-
-							newSystemVia = r->via;
-							Utils::scopy(newSystemDevice,sizeof(newSystemDevice),r->device);
-						}
-					}
-				}
-				if (newSystemVia) { _systemVia = newSystemVia; }
+			// if our routes got deleted
+			// delete the systemd via that we had added with -ifscope
+			if (_systemVia && !!_systemDevice[0]) {
+				_routeCmd("delete",_target,_systemVia,_systemDevice,(const char *)0);
 			}
 
+			_systemVia = newSystemVia;
+			Utils::scopy(_systemDevice,sizeof(_systemDevice),newSystemDevice);
+			// If macos has a network hiccup, it deletes what the route we set, and it's own physical routes.
+			// if !hasRoute (our 0.0.0.0 has been deleted), the OS has changed stuff
+			// So don't assume _systemX are valid anymore. Always get for _system{Via,Device}
 
-			// char buf1[255], buf2[255];
-			// fprintf(stderr, "_systemVia %s new %s\n", _systemVia.toString(buf1), newSystemVia.toString(buf2));
-			if (!_systemVia) { return false; }
+			// Find system default route that this route should override
+			// We need to put it back when default route is turned off
+			for(std::vector<_RTE>::iterator r(rtes.begin());r!=rtes.end();++r) {
+				if (r->via) {
+					if ( r->isDefault == 1 && (strcmp(r->device,_device) != 0) ) {
 
-			if (!_systemDevice[0]) {
-				// Get device corresponding to route if we don't have that already
-				if ((newSystemVia)&&(!newSystemDevice[0])) {
-					rtes = _getRTEs(newSystemVia,true);
-					for(std::vector<_RTE>::iterator r(rtes.begin());r!=rtes.end();++r) {
-						if ( (r->device[0]) && (strcmp(r->device,_device) != 0) && r->target.netmaskBits() != 0) {
-							Utils::scopy(newSystemDevice,sizeof(newSystemDevice),r->device);
-							break;
-						}
+						// char buf[255];
+						// fprintf(stderr, "system device1  %s  %s\n", r->via.toString(buf), r->device);
+
+						newSystemVia = r->via;
+						Utils::scopy(newSystemDevice,sizeof(newSystemDevice),r->device);
+						break;
 					}
 				}
+			}
 
-				if (newSystemDevice[0]) {
-					Utils::scopy(_systemDevice,sizeof(_systemDevice),newSystemDevice);
-				}
+			if (newSystemVia) { _systemVia = newSystemVia; }
+			if (newSystemDevice[0]) {
+				Utils::scopy(_systemDevice,sizeof(_systemDevice),newSystemDevice);
 			}
-			// fprintf(stderr, "_systemDevice %s new %s\n", _systemDevice, newSystemDevice);
-			if (!_systemDevice[0]) { return false; }
 
+			// if there's no newSystemVia, the OS might not have
+			// ipv4 or ipv6 connectivity.
+			// we should still add our ZeroTier ipv4 or 6 routes though
+
+			if (!!_systemVia && !!_systemDevice[0]) {
+				_routeCmd("delete",_target,_systemVia,(const char *)0,(const char *)0);
+			}
 
-			// Do Default Route route commands
-			_routeCmd("delete",_target,_systemVia,(const char *)0,(const char *)0);
 			_routeCmd("add",_target,_via,(const char *)0,(const char *)0);
-			_routeCmd("add",_target,_systemVia,_systemDevice,(const char *)0);
+
+			if (!!_systemVia && !!_systemDevice[0]) {
+				_routeCmd("add",_target,_systemVia,_systemDevice,(const char *)0);
+			}
 
 			_applied[_target] = true;
 
@@ -595,8 +594,8 @@ void ManagedRoute::remove()
 	for(std::map<InetAddress,bool>::iterator r(_applied.begin());r!=_applied.end();++r) {
 #ifdef __BSD__ // ------------------------------------------------------------
 		if (_target && _target.netmaskBits() == 0) {
-			if (_systemVia) {
-				_routeCmd("delete",_target,_via,(const char *)0,(const char *)0);
+			_routeCmd("delete",_target,_via,(const char *)0,(const char *)0);
+			if (_systemVia && _systemDevice[0]) {
 				_routeCmd("delete",_target,_systemVia,_systemDevice,(const char *)0);
 
 				_routeCmd("add",_target,_systemVia,(const char *)0,(const char *)0);