netd: Active FTP Helper

Enable the conntrack helper for active FTP connections when
tethering is started.

Change-Id: I5c812afe9602e80ea1c42d0cafba40fe6019a995
===========================================================

netd: Active FTP Out Iface

Out iface is not used on PREROUTING chain.

Change-Id: I4f89066c52a07ebaad174b513b132de60934fb22
===========================================================

Change-Id: I3f31351b0f032b4aaaad22107c558a8a1a35e617
CRs-fixed: 2151131 2136660
diff --git a/server/TetherController.cpp b/server/TetherController.cpp
index 6e805f5..06eaf94 100644
--- a/server/TetherController.cpp
+++ b/server/TetherController.cpp
@@ -630,6 +630,10 @@
     }
 
     std::vector<std::string> v4 = {
+        "*raw",
+        StringPrintf("%s %s -p tcp --dport 21 -i %s -j CT --helper ftp",
+                     op, LOCAL_RAW_PREROUTING, intIface),
+        "COMMIT",
         "*filter",
         StringPrintf("%s %s -i %s -o %s -m state --state ESTABLISHED,RELATED -g %s",
                      op, LOCAL_FORWARD, extIface, intIface, LOCAL_TETHER_COUNTERS_CHAIN),