some temporary code to make sure it works

osdep/MacDNSHelper.hpp

@@ -8,14 +8,16 @@
 
 namespace ZeroTier {
 
-class MacDNSHelper {
-  public:
-	static void setDNS(uint64_t nwid, const char* domain, const std::vector<InetAddress>& servers);
-	static void removeDNS(uint64_t nwid);
-	static bool addIps4(uint64_t nwid, const MAC mac, const char* dev, const std::vector<InetAddress>& addrs);
-	static bool addIps6(uint64_t nwid, const MAC mac, const char* dev, const std::vector<InetAddress>& addrs);
-	static bool removeIps4(uint64_t nwid);
-	static bool removeIps6(uint64_t nwid);
+class MacDNSHelper
+{
+public:
+    static void setDNS(uint64_t nwid, const char *domain, const std::vector<InetAddress> &servers);
+    static void removeDNS(uint64_t nwid);
+    static bool addIps4(uint64_t nwid, const MAC mac, const char *dev, const std::vector<InetAddress> &addrs);
+    static bool addIps6(uint64_t nwid, const MAC mac, const char *dev, const std::vector<InetAddress> &addrs);
+    static bool removeIps4(uint64_t nwid);
+    static bool removeIps6(uint64_t nwid);
+    static bool getDefaultRoute(char *buf);
 };
 
 }	// namespace ZeroTier

osdep/MacDNSHelper.mm

@@ -343,5 +343,40 @@ bool MacDNSHelper::removeIps4(uint64_t nwid)
     return res;
 }
 
+bool MacDNSHelper::getDefaultRoute(char *buf) {
+    SCDynamicStoreRef ds = SCDynamicStoreCreate(NULL, CFSTR("ZeroTierOne"), NULL, NULL);
+    CFPropertyListRef propertyList = SCDynamicStoreCopyValue(ds, CFSTR("State:/Network/Global/IPv4"));
+
+    if (!propertyList && CFGetTypeID(propertyList) != CFDictionaryGetTypeID()) {
+        if (propertyList != NULL) {CFRelease(propertyList);}
+        CFRelease(ds);
+        return false;
+    }
+
+    CFDictionaryRef dict = (CFDictionaryRef)propertyList;
+
+
+    CFTypeRef routerObject = CFDictionaryGetValue(dict, CFSTR("Router"));
+
+    if (!routerObject && CFGetTypeID(routerObject) != CFStringGetTypeID()) {
+        if (propertyList != NULL) {CFRelease(propertyList);}
+        CFRelease(ds);
+        return false;
+    }
+
+    CFStringRef router = (CFStringRef)routerObject;
+
+    CFIndex length = CFStringGetLength(router);
+    CFIndex maxSize = CFStringGetMaximumSizeForEncoding(length, kCFStringEncodingUTF8) + 1;
+
+    CFStringGetCString(router, buf, maxSize, kCFStringEncodingUTF8);
+
+    if (propertyList != NULL) {CFRelease(propertyList);}
+    CFRelease(ds);
+
+    return true;
+}
+
+
 
 }

service/OneService.cpp

@@ -873,6 +873,8 @@ class OneServiceImpl : public OneService {
 
 	// Last potential sleep/wake event
 	uint64_t _lastRestart;
+	char _lastDefaultGateway[255] = {};
+	bool gatewayChanged = false;
 
 	// Deadline for the next background task service function
 	volatile int64_t _nextBackgroundTaskDeadline;
@@ -1286,6 +1288,19 @@ class OneServiceImpl : public OneService {
 								syncManagedStuff(n->second, false, true, false);
 						}
 					}
+#ifdef __APPLE__
+					char buf[255];
+					MacDNSHelper::getDefaultRoute(buf);
+					if (strlen(_lastDefaultGateway) != 0 && strcmp(_lastDefaultGateway, buf) != 0) {
+						gatewayChanged = true;
+						// fprintf(stderr, "gw changed %i\n prev %s new %s", gatewayChanged, _lastDefaultGateway, buf);
+						// TODO do something to send full hello to roots here
+					} else  {
+						gatewayChanged = false;
+					}
+					strcpy(_lastDefaultGateway, buf);
+#endif
+
 				}
 
 				// Run background task processor in core if it's time to do so