Support enable/disable dns forwarding of dnsmasq

Bugs: 128782815
Test: built, flashed, booted
      cd systen/netd && atest

Change-Id: Id72341885d828e30296f20590c64ff614df63cee
diff --git a/server/TetherController.h b/server/TetherController.h
index 0a04874..7f8ba06 100644
--- a/server/TetherController.h
+++ b/server/TetherController.h
@@ -43,6 +43,8 @@
     // some point since the controller was initialized.
     std::multimap<std::string, ForwardingDownstream> mFwdIfaces;
 
+    bool mIsTetheringStarted = false;
+
     // NetId to use for forwarded DNS queries. This may not be the default
     // network, e.g., in the case where we are tethering to a DUN APN.
     unsigned               mDnsNetId = 0;
@@ -73,8 +75,9 @@
     bool disableForwarding(const char* requester);
     const std::set<std::string>& getIpfwdRequesterList() const;
 
-    int startTethering(int num_addrs, char **dhcp_ranges);
-    int startTethering(const std::vector<std::string>& dhcpRanges);
+    //TODO: Clean up the overload function
+    int startTethering(bool isLegacyDnsProxy, int num_addrs, char** dhcp_ranges);
+    int startTethering(bool isLegacyDnsProxy, const std::vector<std::string>& dhcpRanges);
     int stopTethering();
     bool isTetheringStarted();