diff --git a/service/jni/com_android_server_connectivity_ClatCoordinator.cpp b/service/jni/com_android_server_connectivity_ClatCoordinator.cpp
index c658464..562b1a2 100644
--- a/service/jni/com_android_server_connectivity_ClatCoordinator.cpp
+++ b/service/jni/com_android_server_connectivity_ClatCoordinator.cpp
@@ -26,6 +26,9 @@
 #include "libclat/clatutils.h"
 #include "nativehelper/scoped_utf_chars.h"
 
+// Sync from system/netd/include/netid_client.h
+#define MARK_UNSET 0u
+
 namespace android {
 static void throwIOException(JNIEnv* env, const char* msg, int error) {
     jniThrowExceptionFmt(env, "java/io/IOException", "%s: %s", msg, strerror(error));
@@ -161,6 +164,25 @@
     return sock;
 }
 
+static jint com_android_server_connectivity_ClatCoordinator_openRawSocket6(JNIEnv* env,
+                                                                           jobject clazz,
+                                                                           jint mark) {
+    int sock = socket(AF_INET6, SOCK_RAW | SOCK_NONBLOCK | SOCK_CLOEXEC, IPPROTO_RAW);
+    if (sock < 0) {
+        throwIOException(env, "raw socket failed", errno);
+        return -1;
+    }
+
+    // TODO: check the mark validation
+    if (mark != MARK_UNSET && setsockopt(sock, SOL_SOCKET, SO_MARK, &mark, sizeof(mark)) < 0) {
+        throwIOException(env, "could not set mark on raw socket", errno);
+        close(sock);
+        return -1;
+    }
+
+    return sock;
+}
+
 /*
  * JNI registration.
  */
@@ -177,6 +199,8 @@
          (void*)com_android_server_connectivity_ClatCoordinator_detectMtu},
         {"openPacketSocket", "()I",
          (void*)com_android_server_connectivity_ClatCoordinator_openPacketSocket},
+        {"openRawSocket6", "(I)I",
+         (void*)com_android_server_connectivity_ClatCoordinator_openRawSocket6},
 };
 
 int register_android_server_connectivity_ClatCoordinator(JNIEnv* env) {
diff --git a/service/src/com/android/server/connectivity/ClatCoordinator.java b/service/src/com/android/server/connectivity/ClatCoordinator.java
index bc635ed..cf956c5 100644
--- a/service/src/com/android/server/connectivity/ClatCoordinator.java
+++ b/service/src/com/android/server/connectivity/ClatCoordinator.java
@@ -128,6 +128,13 @@
         public int jniOpenPacketSocket() throws IOException {
             return openPacketSocket();
         }
+
+        /**
+         * Open IPv6 raw socket and set SO_MARK.
+         */
+        public int jniOpenRawSocket6(int mark) throws IOException {
+            return openRawSocket6(mark);
+        }
     }
 
     @VisibleForTesting
@@ -241,6 +248,16 @@
             throw new IOException("Open packet socket failed: " + e);
         }
 
+        // Opens a raw socket with a given fwmark to send IPv6 packets in clatd.
+        final ParcelFileDescriptor writeSock6;
+        try {
+            // Use a JNI call to get native file descriptor instead of Os.socket(). See above
+            // reason why we use jniOpenPacketSocket6().
+            writeSock6 = mDeps.adoptFd(mDeps.jniOpenRawSocket6(fwmark));
+        } catch (IOException e) {
+            throw new IOException("Open raw socket failed: " + e);
+        }
+
         // TODO: start clatd and returns local xlat464 v6 address.
         return null;
     }
@@ -253,4 +270,5 @@
     private static native int detectMtu(String platSubnet, int platSuffix, int mark)
             throws IOException;
     private static native int openPacketSocket() throws IOException;
+    private static native int openRawSocket6(int mark) throws IOException;
 }