3 files changed, 42 insertions, 0 deletions
diff --git a/libs/binder/RpcServer.cpp b/libs/binder/RpcServer.cpp
index dc10d1c524..9cc6e7fe04 100644
--- a/libs/binder/RpcServer.cpp
+++ b/libs/binder/RpcServer.cpp
@@ -272,8 +272,26 @@ void RpcServer::onSessionTerminating(const sp<RpcSession>& session) {
 }
 
 bool RpcServer::hasServer() {
+    LOG_ALWAYS_FATAL_IF(!mAgreedExperimental, "no!");
     std::lock_guard<std::mutex> _l(mLock);
     return mServer.ok();
 }
 
+unique_fd RpcServer::releaseServer() {
+    LOG_ALWAYS_FATAL_IF(!mAgreedExperimental, "no!");
+    std::lock_guard<std::mutex> _l(mLock);
+    return std::move(mServer);
+}
+
+bool RpcServer::setupExternalServer(base::unique_fd serverFd) {
+    LOG_ALWAYS_FATAL_IF(!mAgreedExperimental, "no!");
+    std::lock_guard<std::mutex> _l(mLock);
+    if (mServer.ok()) {
+        ALOGE("Each RpcServer can only have one server.");
+        return false;
+    }
+    mServer = std::move(serverFd);
+    return true;
+}
+
 } // namespace android
diff --git a/libs/binder/include/binder/RpcServer.h b/libs/binder/include/binder/RpcServer.h
index 771bbe68b8..8f0c6fd5e1 100644
--- a/libs/binder/include/binder/RpcServer.h
+++ b/libs/binder/include/binder/RpcServer.h
@@ -79,6 +79,17 @@ public:
      */
     [[nodiscard]] bool hasServer();
 
+    /**
+     * If hasServer(), return the server FD. Otherwise return invalid FD.
+     */
+    [[nodiscard]] base::unique_fd releaseServer();
+
+    /**
+     * Set up server using an external FD previously set up by releaseServer().
+     * Return false if there's already a server.
+     */
+    bool setupExternalServer(base::unique_fd serverFd);
+
     void iUnderstandThisCodeIsExperimentalAndIWillNotUseItInProduction();
 
     /**
diff --git a/libs/binder/tests/binderRpcTest.cpp b/libs/binder/tests/binderRpcTest.cpp
index 260be570f9..a96deb5d27 100644
--- a/libs/binder/tests/binderRpcTest.cpp
+++ b/libs/binder/tests/binderRpcTest.cpp
@@ -49,6 +49,19 @@ TEST(BinderRpcParcel, EntireParcelFormatted) {
     EXPECT_DEATH(p.markForBinder(sp<BBinder>::make()), "");
 }
 
+TEST(BinderRpc, SetExternalServer) {
+    base::unique_fd sink(TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR)));
+    int sinkFd = sink.get();
+    auto server = RpcServer::make();
+    server->iUnderstandThisCodeIsExperimentalAndIWillNotUseItInProduction();
+    ASSERT_FALSE(server->hasServer());
+    ASSERT_TRUE(server->setupExternalServer(std::move(sink)));
+    ASSERT_TRUE(server->hasServer());
+    base::unique_fd retrieved = server->releaseServer();
+    ASSERT_FALSE(server->hasServer());
+    ASSERT_EQ(sinkFd, retrieved.get());
+}
+
 using android::binder::Status;
 
 #define EXPECT_OK(status)                 \