Setup interfaces for IPv6 tethering

Including:
    - set the interface for router mode (accept_ra = 0)
    - reset the interface for client mode (accept_ra = 1)
    - InterfaceController::setAcceptIPv6Ra()
    - InterfaceController::setAcceptIPv6Dad()
    - make InterfaceController static
    - refactor for more modern C++ usage here and there
    - sporadic style guide fixes

Bug: 9580643
Change-Id: Ia557c8770e18c58b12ad16d982c63b6ebd525516
diff --git a/server/InterfaceController.h b/server/InterfaceController.h
index 89728b1..4c8057e 100644
--- a/server/InterfaceController.h
+++ b/server/InterfaceController.h
@@ -18,19 +18,24 @@
 #define _INTERFACE_CONTROLLER_H
 
 class InterfaceController {
- public:
-	InterfaceController();
-	virtual ~InterfaceController();
-	int setEnableIPv6(const char *interface, const int on);
-	int setIPv6PrivacyExtensions(const char *interface, const int on);
-	int setIPv6NdOffload(char* interface, const int on);
-	int setMtu(const char *interface, const char *mtu);
+public:
+    static void initializeAll();
 
- private:
-	void setAcceptRA(const char* value);
-	void setAcceptRARouteTable(int tableOrOffset);
-	void setBaseReachableTimeMs(unsigned int millis);
-	void setIPv6OptimisticMode(const char *value);
+    static int setEnableIPv6(const char *interface, const int on);
+    static int setAcceptIPv6Ra(const char *interface, const int on);
+    static int setAcceptIPv6Dad(const char *interface, const int on);
+    static int setIPv6PrivacyExtensions(const char *interface, const int on);
+    static int setIPv6NdOffload(char* interface, const int on);
+    static int setMtu(const char *interface, const char *mtu);
+
+private:
+    static void setAcceptRA(const char* value);
+    static void setAcceptRARouteTable(int tableOrOffset);
+    static void setBaseReachableTimeMs(unsigned int millis);
+    static void setIPv6OptimisticMode(const char *value);
+
+    InterfaceController() = delete;
+    ~InterfaceController() = delete;
 };
 
 #endif