[CLATJ#12] ClatCoordinator: open packet socket with a given mark

Move the packet socket initialization from netd to jni because
mainline module is going to launch clatd. Need to provide packet
socket for reading local 464xlat IPv6 packets.

Bug: 212345928
Test: flash and boot
Run "atest ClatCoordinatorTest" in a followup commit.

Change-Id: I1cef6e099403f883d668081fb5e917863f5a3c2a

service/src/com/android/server/connectivity/ClatCoordinator.java

@@ -121,6 +121,13 @@ public class ClatCoordinator {
                 throws IOException {
             return detectMtu(platSubnet, platSuffix, mark);
         }
+
+        /**
+         * Open packet socket.
+         */
+        public int jniOpenPacketSocket() throws IOException {
+            return openPacketSocket();
+        }
     }
 
     @VisibleForTesting
@@ -221,6 +228,19 @@ public class ClatCoordinator {
                     + ifConfig.prefixLength + " failed on " + ifConfig.ifName + ": " + e);
         }
 
+        // [4] Open and configure local 464xlat read/write sockets.
+        // Opens a packet socket to receive IPv6 packets in clatd.
+        final ParcelFileDescriptor readSock6;
+        try {
+            // Use a JNI call to get native file descriptor instead of Os.socket() because we would
+            // like to use ParcelFileDescriptor to close file descriptor automatically. But ctor
+            // ParcelFileDescriptor(FileDescriptor fd) is a @hide function. Need to use native file
+            // descriptor to initialize ParcelFileDescriptor object instead.
+            readSock6 = mDeps.adoptFd(mDeps.jniOpenPacketSocket());
+        } catch (IOException e) {
+            throw new IOException("Open packet socket failed: " + e);
+        }
+
         // TODO: start clatd and returns local xlat464 v6 address.
         return null;
     }
@@ -232,4 +252,5 @@ public class ClatCoordinator {
     private static native int createTunInterface(String tuniface) throws IOException;
     private static native int detectMtu(String platSubnet, int platSuffix, int mark)
             throws IOException;
+    private static native int openPacketSocket() throws IOException;
 }