diff --git a/service/jni/com_android_server_connectivity_ClatCoordinator.cpp b/service/jni/com_android_server_connectivity_ClatCoordinator.cpp
new file mode 100644
index 0000000..e042bf3
--- /dev/null
+++ b/service/jni/com_android_server_connectivity_ClatCoordinator.cpp
@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <arpa/inet.h>
+#include <nativehelper/JNIHelp.h>
+
+#include <netjniutils/netjniutils.h>
+
+#include "libclat/clatutils.h"
+#include "nativehelper/scoped_utf_chars.h"
+
+namespace android {
+jstring com_android_server_connectivity_ClatCoordinator_selectIpv4Address(JNIEnv* env,
+                                                                          jobject clazz,
+                                                                          jstring v4addr,
+                                                                          jint prefixlen) {
+    ScopedUtfChars address(env, v4addr);
+    in_addr ip;
+    if (inet_pton(AF_INET, address.c_str(), &ip) != 1) {
+        return nullptr;
+    }
+
+    // Pick an IPv4 address.
+    // TODO: this picks the address based on other addresses that are assigned to interfaces, but
+    // the address is only actually assigned to an interface once clatd starts up. So we could end
+    // up with two clatd instances with the same IPv4 address.
+    // Stop doing this and instead pick a free one from the kV4Addr pool.
+    in_addr v4 = {net::clat::selectIpv4Address(ip, prefixlen)};
+    if (v4.s_addr == INADDR_NONE) {
+        jniThrowExceptionFmt(env, "java/io/IOException", "No free IPv4 address in %s/%d",
+                             address.c_str(), prefixlen);
+        return nullptr;
+    }
+
+    char addrstr[INET_ADDRSTRLEN];
+    if (!inet_ntop(AF_INET, (void*)&v4, addrstr, sizeof(addrstr))) {
+        return nullptr;
+    }
+    return env->NewStringUTF(addrstr);
+}
+
+/*
+ * JNI registration.
+ */
+static const JNINativeMethod gMethods[] = {
+        /* name, signature, funcPtr */
+        {"selectIpv4Address", "(Ljava/lang/String;I)Ljava/lang/String;",
+         (void*)com_android_server_connectivity_ClatCoordinator_selectIpv4Address},
+};
+
+int register_android_server_connectivity_ClatCoordinator(JNIEnv* env) {
+    return jniRegisterNativeMethods(env, "com/android/server/connectivity/ClatCoordinator",
+                                    gMethods, NELEM(gMethods));
+}
+
+};  // namespace android
diff --git a/service/jni/onload.cpp b/service/jni/onload.cpp
index 0012879..04d9671 100644
--- a/service/jni/onload.cpp
+++ b/service/jni/onload.cpp
@@ -20,6 +20,7 @@
 namespace android {
 
 int register_android_server_TestNetworkService(JNIEnv* env);
+int register_android_server_connectivity_ClatCoordinator(JNIEnv* env);
 
 extern "C" jint JNI_OnLoad(JavaVM* vm, void*) {
     JNIEnv *env;
@@ -32,6 +33,10 @@
         return JNI_ERR;
     }
 
+    if (register_android_server_connectivity_ClatCoordinator(env) < 0) {
+        return JNI_ERR;
+    }
+
     return JNI_VERSION_1_6;
 }