libs/binder/RpcServer.cpp - platform/frameworks/native - Gitiles

 /*
  * Copyright (C) 2020 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.
  */

 #define LOG_TAG "RpcServer"

 #include <poll.h>
 #include <sys/socket.h>
 #include <sys/un.h>

 #include <thread>
 #include <vector>

 #include <android-base/scopeguard.h>
 #include <binder/Parcel.h>
 #include <binder/RpcServer.h>
 #include <log/log.h>

 #include "RpcSocketAddress.h"
 #include "RpcState.h"
 #include "RpcWireFormat.h"

 namespace android {

 using base::ScopeGuard;
 using base::unique_fd;

 RpcServer::RpcServer() {}
 RpcServer::~RpcServer() {
     (void)shutdown();
 }

 sp<RpcServer> RpcServer::make() {
     return sp<RpcServer>::make();
 }

 void RpcServer::iUnderstandThisCodeIsExperimentalAndIWillNotUseItInProduction() {
     mAgreedExperimental = true;
 }

 bool RpcServer::setupUnixDomainServer(const char* path) {
     return setupSocketServer(UnixSocketAddress(path));
 }

 bool RpcServer::setupVsockServer(unsigned int port) {
     // realizing value w/ this type at compile time to avoid ubsan abort
     constexpr unsigned int kAnyCid = VMADDR_CID_ANY;

     return setupSocketServer(VsockSocketAddress(kAnyCid, port));
 }

 bool RpcServer::setupInetServer(unsigned int port, unsigned int* assignedPort) {
     const char* kAddr = "127.0.0.1";

     if (assignedPort != nullptr) *assignedPort = 0;
     auto aiStart = InetSocketAddress::getAddrInfo(kAddr, port);
     if (aiStart == nullptr) return false;
     for (auto ai = aiStart.get(); ai != nullptr; ai = ai->ai_next) {
         InetSocketAddress socketAddress(ai->ai_addr, ai->ai_addrlen, kAddr, port);
         if (!setupSocketServer(socketAddress)) {
             continue;
         }

         LOG_ALWAYS_FATAL_IF(socketAddress.addr()->sa_family != AF_INET, "expecting inet");
         sockaddr_in addr{};
         socklen_t len = sizeof(addr);
         if (0 != getsockname(mServer.get(), reinterpret_cast<sockaddr*>(&addr), &len)) {
             int savedErrno = errno;
             ALOGE("Could not getsockname at %s: %s", socketAddress.toString().c_str(),
                   strerror(savedErrno));
             return false;
         }
         LOG_ALWAYS_FATAL_IF(len != sizeof(addr), "Wrong socket type: len %zu vs len %zu",
                             static_cast<size_t>(len), sizeof(addr));
         unsigned int realPort = ntohs(addr.sin_port);
         LOG_ALWAYS_FATAL_IF(port != 0 && realPort != port,
                             "Requesting inet server on %s but it is set up on %u.",
                             socketAddress.toString().c_str(), realPort);

         if (assignedPort != nullptr) {
             *assignedPort = realPort;
         }

         return true;
     }
     ALOGE("None of the socket address resolved for %s:%u can be set up as inet server.", kAddr,
           port);
     return false;
 }

 void RpcServer::setMaxThreads(size_t threads) {
     LOG_ALWAYS_FATAL_IF(threads <= 0, "RpcServer is useless without threads");
     LOG_ALWAYS_FATAL_IF(mJoinThreadRunning, "Cannot set max threads while running");
     mMaxThreads = threads;
 }

 size_t RpcServer::getMaxThreads() {
     return mMaxThreads;
 }

 void RpcServer::setRootObject(const sp<IBinder>& binder) {
     std::lock_guard<std::mutex> _l(mLock);
     mRootObjectWeak = mRootObject = binder;
 }

 void RpcServer::setRootObjectWeak(const wp<IBinder>& binder) {
     std::lock_guard<std::mutex> _l(mLock);
     mRootObject.clear();
     mRootObjectWeak = binder;
 }

 sp<IBinder> RpcServer::getRootObject() {
     std::lock_guard<std::mutex> _l(mLock);
     bool hasWeak = mRootObjectWeak.unsafe_get();
     sp<IBinder> ret = mRootObjectWeak.promote();
     ALOGW_IF(hasWeak && ret == nullptr, "RpcServer root object is freed, returning nullptr");
     return ret;
 }

 static void joinRpcServer(sp<RpcServer>&& thiz) {
     thiz->join();
 }

 void RpcServer::start() {
     LOG_ALWAYS_FATAL_IF(!mAgreedExperimental, "no!");
     std::lock_guard<std::mutex> _l(mLock);
     LOG_ALWAYS_FATAL_IF(mJoinThread.get(), "Already started!");
     mJoinThread = std::make_unique<std::thread>(&joinRpcServer, sp<RpcServer>::fromExisting(this));
 }

 void RpcServer::join() {
     LOG_ALWAYS_FATAL_IF(!mAgreedExperimental, "no!");

     {
         std::lock_guard<std::mutex> _l(mLock);
         LOG_ALWAYS_FATAL_IF(!mServer.ok(), "RpcServer must be setup to join.");
         LOG_ALWAYS_FATAL_IF(mShutdownTrigger != nullptr, "Already joined");
         mJoinThreadRunning = true;
         mShutdownTrigger = RpcSession::FdTrigger::make();
         LOG_ALWAYS_FATAL_IF(mShutdownTrigger == nullptr, "Cannot create join signaler");
     }

     status_t status;
     while ((status = mShutdownTrigger->triggerablePoll(mServer, POLLIN)) == OK) {
         unique_fd clientFd(TEMP_FAILURE_RETRY(
                 accept4(mServer.get(), nullptr, nullptr /*length*/, SOCK_CLOEXEC)));

         if (clientFd < 0) {
             ALOGE("Could not accept4 socket: %s", strerror(errno));
             continue;
         }
         LOG_RPC_DETAIL("accept4 on fd %d yields fd %d", mServer.get(), clientFd.get());

         {
             std::lock_guard<std::mutex> _l(mLock);
             std::thread thread =
                     std::thread(&RpcServer::establishConnection, sp<RpcServer>::fromExisting(this),
                                 std::move(clientFd));
             mConnectingThreads[thread.get_id()] = std::move(thread);
         }
     }
     LOG_RPC_DETAIL("RpcServer::join exiting with %s", statusToString(status).c_str());

     {
         std::lock_guard<std::mutex> _l(mLock);
         mJoinThreadRunning = false;
     }
     mShutdownCv.notify_all();
 }

 bool RpcServer::shutdown() {
     std::unique_lock<std::mutex> _l(mLock);
     if (mShutdownTrigger == nullptr) {
         LOG_RPC_DETAIL("Cannot shutdown. No shutdown trigger installed (already shutdown?)");
         return false;
     }

     mShutdownTrigger->trigger();
     for (auto& [id, session] : mSessions) {
         (void)id;
         session->mShutdownTrigger->trigger();
     }

     while (mJoinThreadRunning || !mConnectingThreads.empty() || !mSessions.empty()) {
         if (std::cv_status::timeout == mShutdownCv.wait_for(_l, std::chrono::seconds(1))) {
             ALOGE("Waiting for RpcServer to shut down (1s w/o progress). Join thread running: %d, "
                   "Connecting threads: "
                   "%zu, Sessions: %zu. Is your server deadlocked?",
                   mJoinThreadRunning, mConnectingThreads.size(), mSessions.size());
         }
     }

     // At this point, we know join() is about to exit, but the thread that calls
     // join() may not have exited yet.
     // If RpcServer owns the join thread (aka start() is called), make sure the thread exits;
     // otherwise ~thread() may call std::terminate(), which may crash the process.
     // If RpcServer does not own the join thread (aka join() is called directly),
     // then the owner of RpcServer is responsible for cleaning up that thread.
     if (mJoinThread.get()) {
         mJoinThread->join();
         mJoinThread.reset();
     }

     LOG_RPC_DETAIL("Finished waiting on shutdown.");

     mShutdownTrigger = nullptr;
     return true;
 }

 std::vector<sp<RpcSession>> RpcServer::listSessions() {
     std::lock_guard<std::mutex> _l(mLock);
     std::vector<sp<RpcSession>> sessions;
     for (auto& [id, session] : mSessions) {
         (void)id;
         sessions.push_back(session);
     }
     return sessions;
 }

 size_t RpcServer::numUninitializedSessions() {
     std::lock_guard<std::mutex> _l(mLock);
     return mConnectingThreads.size();
 }

 void RpcServer::establishConnection(sp<RpcServer>&& server, base::unique_fd clientFd) {
     // TODO(b/183988761): cannot trust this simple ID
     LOG_ALWAYS_FATAL_IF(!server->mAgreedExperimental, "no!");

     // mShutdownTrigger can only be cleared once connection threads have joined.
     // It must be set before this thread is started
     LOG_ALWAYS_FATAL_IF(server->mShutdownTrigger == nullptr);

     RpcConnectionHeader header;
     status_t status = server->mShutdownTrigger->interruptableReadFully(clientFd.get(), &header,
                                                                        sizeof(header));
     bool idValid = status == OK;
     if (!idValid) {
         ALOGE("Failed to read ID for client connecting to RPC server: %s",
               statusToString(status).c_str());
         // still need to cleanup before we can return
     }
     bool incoming = header.options & RPC_CONNECTION_OPTION_INCOMING;

     std::thread thisThread;
     sp<RpcSession> session;
     {
         std::unique_lock<std::mutex> _l(server->mLock);

         auto threadId = server->mConnectingThreads.find(std::this_thread::get_id());
         LOG_ALWAYS_FATAL_IF(threadId == server->mConnectingThreads.end(),
                             "Must establish connection on owned thread");
         thisThread = std::move(threadId->second);
         ScopeGuard detachGuard = [&]() {
             thisThread.detach();
             _l.unlock();
             server->mShutdownCv.notify_all();
         };
         server->mConnectingThreads.erase(threadId);

         if (!idValid || server->mShutdownTrigger->isTriggered()) {
             return;
         }

         RpcAddress sessionId = RpcAddress::fromRawEmbedded(&header.sessionId);

         if (sessionId.isZero()) {
             if (incoming) {
                 ALOGE("Cannot create a new session with an incoming connection, would leak");
                 return;
             }

             sessionId = RpcAddress::zero();
             size_t tries = 0;
             do {
                 // don't block if there is some entropy issue
                 if (tries++ > 5) {
                     ALOGE("Cannot find new address: %s", sessionId.toString().c_str());
                     return;
                 }

                 sessionId = RpcAddress::random(true /*forServer*/);
             } while (server->mSessions.end() != server->mSessions.find(sessionId));

             session = RpcSession::make();
             session->setMaxThreads(server->mMaxThreads);
             if (!session->setForServer(server,
                                        sp<RpcServer::EventListener>::fromExisting(
                                                static_cast<RpcServer::EventListener*>(
                                                        server.get())),
                                        sessionId)) {
                 ALOGE("Failed to attach server to session");
                 return;
             }

             server->mSessions[sessionId] = session;
         } else {
             auto it = server->mSessions.find(sessionId);
             if (it == server->mSessions.end()) {
                 ALOGE("Cannot add thread, no record of session with ID %s",
                       sessionId.toString().c_str());
                 return;
             }
             session = it->second;
         }

         if (incoming) {
             LOG_ALWAYS_FATAL_IF(!session->addOutgoingConnection(std::move(clientFd), true),
                                 "server state must already be initialized");
             return;
         }

         detachGuard.Disable();
         session->preJoinThreadOwnership(std::move(thisThread));
     }

     auto setupResult = session->preJoinSetup(std::move(clientFd));

     // avoid strong cycle
     server = nullptr;

     RpcSession::join(std::move(session), std::move(setupResult));
 }

 bool RpcServer::setupSocketServer(const RpcSocketAddress& addr) {
     LOG_RPC_DETAIL("Setting up socket server %s", addr.toString().c_str());
     LOG_ALWAYS_FATAL_IF(hasServer(), "Each RpcServer can only have one server.");

     unique_fd serverFd(
             TEMP_FAILURE_RETRY(socket(addr.addr()->sa_family, SOCK_STREAM | SOCK_CLOEXEC, 0)));
     if (serverFd == -1) {
         ALOGE("Could not create socket: %s", strerror(errno));
         return false;
     }

     if (0 != TEMP_FAILURE_RETRY(bind(serverFd.get(), addr.addr(), addr.addrSize()))) {
         int savedErrno = errno;
         ALOGE("Could not bind socket at %s: %s", addr.toString().c_str(), strerror(savedErrno));
         return false;
     }

     // Right now, we create all threads at once, making accept4 slow. To avoid hanging the client,
     // the backlog is increased to a large number.
     // TODO(b/189955605): Once we create threads dynamically & lazily, the backlog can be reduced
     //  to 1.
     if (0 != TEMP_FAILURE_RETRY(listen(serverFd.get(), 50 /*backlog*/))) {
         int savedErrno = errno;
         ALOGE("Could not listen socket at %s: %s", addr.toString().c_str(), strerror(savedErrno));
         return false;
     }

     LOG_RPC_DETAIL("Successfully setup socket server %s", addr.toString().c_str());

     if (!setupExternalServer(std::move(serverFd))) {
         ALOGE("Another thread has set up server while calling setupSocketServer. Race?");
         return false;
     }
     return true;
 }

 void RpcServer::onSessionLockedAllIncomingThreadsEnded(const sp<RpcSession>& session) {
     auto id = session->mId;
     LOG_ALWAYS_FATAL_IF(id == std::nullopt, "Server sessions must be initialized with ID");
     LOG_RPC_DETAIL("Dropping session with address %s", id->toString().c_str());

     std::lock_guard<std::mutex> _l(mLock);
     auto it = mSessions.find(*id);
     LOG_ALWAYS_FATAL_IF(it == mSessions.end(), "Bad state, unknown session id %s",
                         id->toString().c_str());
     LOG_ALWAYS_FATAL_IF(it->second != session, "Bad state, session has id mismatch %s",
                         id->toString().c_str());
     (void)mSessions.erase(it);
 }

 void RpcServer::onSessionIncomingThreadEnded() {
     mShutdownCv.notify_all();
 }

 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
	/*
	* Copyright (C) 2020 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.
	*/

	#define LOG_TAG "RpcServer"

	#include <poll.h>
	#include <sys/socket.h>
	#include <sys/un.h>

	#include <thread>
	#include <vector>

	#include <android-base/scopeguard.h>
	#include <binder/Parcel.h>
	#include <binder/RpcServer.h>
	#include <log/log.h>

	#include "RpcSocketAddress.h"
	#include "RpcState.h"
	#include "RpcWireFormat.h"

	namespace android {

	using base::ScopeGuard;
	using base::unique_fd;

	RpcServer::RpcServer() {}
	RpcServer::~RpcServer() {
	(void)shutdown();
	}

	sp<RpcServer> RpcServer::make() {
	return sp<RpcServer>::make();
	}

	void RpcServer::iUnderstandThisCodeIsExperimentalAndIWillNotUseItInProduction() {
	mAgreedExperimental = true;
	}

	bool RpcServer::setupUnixDomainServer(const char* path) {
	return setupSocketServer(UnixSocketAddress(path));
	}

	bool RpcServer::setupVsockServer(unsigned int port) {
	// realizing value w/ this type at compile time to avoid ubsan abort
	constexpr unsigned int kAnyCid = VMADDR_CID_ANY;

	return setupSocketServer(VsockSocketAddress(kAnyCid, port));
	}

	bool RpcServer::setupInetServer(unsigned int port, unsigned int* assignedPort) {
	const char* kAddr = "127.0.0.1";

	if (assignedPort != nullptr) *assignedPort = 0;
	auto aiStart = InetSocketAddress::getAddrInfo(kAddr, port);
	if (aiStart == nullptr) return false;
	for (auto ai = aiStart.get(); ai != nullptr; ai = ai->ai_next) {
	InetSocketAddress socketAddress(ai->ai_addr, ai->ai_addrlen, kAddr, port);
	if (!setupSocketServer(socketAddress)) {
	continue;
	}

	LOG_ALWAYS_FATAL_IF(socketAddress.addr()->sa_family != AF_INET, "expecting inet");
	sockaddr_in addr{};
	socklen_t len = sizeof(addr);
	if (0 != getsockname(mServer.get(), reinterpret_cast<sockaddr*>(&addr), &len)) {
	int savedErrno = errno;
	ALOGE("Could not getsockname at %s: %s", socketAddress.toString().c_str(),
	strerror(savedErrno));
	return false;
	}
	LOG_ALWAYS_FATAL_IF(len != sizeof(addr), "Wrong socket type: len %zu vs len %zu",
	static_cast<size_t>(len), sizeof(addr));
	unsigned int realPort = ntohs(addr.sin_port);
	LOG_ALWAYS_FATAL_IF(port != 0 && realPort != port,
	"Requesting inet server on %s but it is set up on %u.",
	socketAddress.toString().c_str(), realPort);

	if (assignedPort != nullptr) {
	*assignedPort = realPort;
	}

	return true;
	}
	ALOGE("None of the socket address resolved for %s:%u can be set up as inet server.", kAddr,
	port);
	return false;
	}

	void RpcServer::setMaxThreads(size_t threads) {
	LOG_ALWAYS_FATAL_IF(threads <= 0, "RpcServer is useless without threads");
	LOG_ALWAYS_FATAL_IF(mJoinThreadRunning, "Cannot set max threads while running");
	mMaxThreads = threads;
	}

	size_t RpcServer::getMaxThreads() {
	return mMaxThreads;
	}

	void RpcServer::setRootObject(const sp<IBinder>& binder) {
	std::lock_guard<std::mutex> _l(mLock);
	mRootObjectWeak = mRootObject = binder;
	}

	void RpcServer::setRootObjectWeak(const wp<IBinder>& binder) {
	std::lock_guard<std::mutex> _l(mLock);
	mRootObject.clear();
	mRootObjectWeak = binder;
	}

	sp<IBinder> RpcServer::getRootObject() {
	std::lock_guard<std::mutex> _l(mLock);
	bool hasWeak = mRootObjectWeak.unsafe_get();
	sp<IBinder> ret = mRootObjectWeak.promote();
	ALOGW_IF(hasWeak && ret == nullptr, "RpcServer root object is freed, returning nullptr");
	return ret;
	}

	static void joinRpcServer(sp<RpcServer>&& thiz) {
	thiz->join();
	}

	void RpcServer::start() {
	LOG_ALWAYS_FATAL_IF(!mAgreedExperimental, "no!");
	std::lock_guard<std::mutex> _l(mLock);
	LOG_ALWAYS_FATAL_IF(mJoinThread.get(), "Already started!");
	mJoinThread = std::make_unique<std::thread>(&joinRpcServer, sp<RpcServer>::fromExisting(this));
	}

	void RpcServer::join() {
	LOG_ALWAYS_FATAL_IF(!mAgreedExperimental, "no!");

	{
	std::lock_guard<std::mutex> _l(mLock);
	LOG_ALWAYS_FATAL_IF(!mServer.ok(), "RpcServer must be setup to join.");
	LOG_ALWAYS_FATAL_IF(mShutdownTrigger != nullptr, "Already joined");
	mJoinThreadRunning = true;
	mShutdownTrigger = RpcSession::FdTrigger::make();
	LOG_ALWAYS_FATAL_IF(mShutdownTrigger == nullptr, "Cannot create join signaler");
	}

	status_t status;
	while ((status = mShutdownTrigger->triggerablePoll(mServer, POLLIN)) == OK) {
	unique_fd clientFd(TEMP_FAILURE_RETRY(
	accept4(mServer.get(), nullptr, nullptr /length/, SOCK_CLOEXEC)));

	if (clientFd < 0) {
	ALOGE("Could not accept4 socket: %s", strerror(errno));
	continue;
	}
	LOG_RPC_DETAIL("accept4 on fd %d yields fd %d", mServer.get(), clientFd.get());

	{
	std::lock_guard<std::mutex> _l(mLock);
	std::thread thread =
	std::thread(&RpcServer::establishConnection, sp<RpcServer>::fromExisting(this),
	std::move(clientFd));
	mConnectingThreads[thread.get_id()] = std::move(thread);
	}
	}
	LOG_RPC_DETAIL("RpcServer::join exiting with %s", statusToString(status).c_str());

	{
	std::lock_guard<std::mutex> _l(mLock);
	mJoinThreadRunning = false;
	}
	mShutdownCv.notify_all();
	}

	bool RpcServer::shutdown() {
	std::unique_lock<std::mutex> _l(mLock);
	if (mShutdownTrigger == nullptr) {
	LOG_RPC_DETAIL("Cannot shutdown. No shutdown trigger installed (already shutdown?)");
	return false;
	}

	mShutdownTrigger->trigger();
	for (auto& [id, session] : mSessions) {
	(void)id;
	session->mShutdownTrigger->trigger();
	}

	while (mJoinThreadRunning \|\| !mConnectingThreads.empty() \|\| !mSessions.empty()) {
	if (std::cv_status::timeout == mShutdownCv.wait_for(_l, std::chrono::seconds(1))) {
	ALOGE("Waiting for RpcServer to shut down (1s w/o progress). Join thread running: %d, "
	"Connecting threads: "
	"%zu, Sessions: %zu. Is your server deadlocked?",
	mJoinThreadRunning, mConnectingThreads.size(), mSessions.size());
	}
	}

	// At this point, we know join() is about to exit, but the thread that calls
	// join() may not have exited yet.
	// If RpcServer owns the join thread (aka start() is called), make sure the thread exits;
	// otherwise ~thread() may call std::terminate(), which may crash the process.
	// If RpcServer does not own the join thread (aka join() is called directly),
	// then the owner of RpcServer is responsible for cleaning up that thread.
	if (mJoinThread.get()) {
	mJoinThread->join();
	mJoinThread.reset();
	}

	LOG_RPC_DETAIL("Finished waiting on shutdown.");

	mShutdownTrigger = nullptr;
	return true;
	}

	std::vector<sp<RpcSession>> RpcServer::listSessions() {
	std::lock_guard<std::mutex> _l(mLock);
	std::vector<sp<RpcSession>> sessions;
	for (auto& [id, session] : mSessions) {
	(void)id;
	sessions.push_back(session);
	}
	return sessions;
	}

	size_t RpcServer::numUninitializedSessions() {
	std::lock_guard<std::mutex> _l(mLock);
	return mConnectingThreads.size();
	}

	void RpcServer::establishConnection(sp<RpcServer>&& server, base::unique_fd clientFd) {
	// TODO(b/183988761): cannot trust this simple ID
	LOG_ALWAYS_FATAL_IF(!server->mAgreedExperimental, "no!");

	// mShutdownTrigger can only be cleared once connection threads have joined.
	// It must be set before this thread is started
	LOG_ALWAYS_FATAL_IF(server->mShutdownTrigger == nullptr);

	RpcConnectionHeader header;
	status_t status = server->mShutdownTrigger->interruptableReadFully(clientFd.get(), &header,
	sizeof(header));
	bool idValid = status == OK;
	if (!idValid) {
	ALOGE("Failed to read ID for client connecting to RPC server: %s",
	statusToString(status).c_str());
	// still need to cleanup before we can return
	}
	bool incoming = header.options & RPC_CONNECTION_OPTION_INCOMING;

	std::thread thisThread;
	sp<RpcSession> session;
	{
	std::unique_lock<std::mutex> _l(server->mLock);

	auto threadId = server->mConnectingThreads.find(std::this_thread::get_id());
	LOG_ALWAYS_FATAL_IF(threadId == server->mConnectingThreads.end(),
	"Must establish connection on owned thread");
	thisThread = std::move(threadId->second);
	ScopeGuard detachGuard = [&]() {
	thisThread.detach();
	_l.unlock();
	server->mShutdownCv.notify_all();
	};
	server->mConnectingThreads.erase(threadId);

	if (!idValid \|\| server->mShutdownTrigger->isTriggered()) {
	return;
	}

	RpcAddress sessionId = RpcAddress::fromRawEmbedded(&header.sessionId);

	if (sessionId.isZero()) {
	if (incoming) {
	ALOGE("Cannot create a new session with an incoming connection, would leak");
	return;
	}

	sessionId = RpcAddress::zero();
	size_t tries = 0;
	do {
	// don't block if there is some entropy issue
	if (tries++ > 5) {
	ALOGE("Cannot find new address: %s", sessionId.toString().c_str());
	return;
	}

	sessionId = RpcAddress::random(true /forServer/);
	} while (server->mSessions.end() != server->mSessions.find(sessionId));

	session = RpcSession::make();
	session->setMaxThreads(server->mMaxThreads);
	if (!session->setForServer(server,
	sp<RpcServer::EventListener>::fromExisting(
	static_cast<RpcServer::EventListener*>(
	server.get())),
	sessionId)) {
	ALOGE("Failed to attach server to session");
	return;
	}

	server->mSessions[sessionId] = session;
	} else {
	auto it = server->mSessions.find(sessionId);
	if (it == server->mSessions.end()) {
	ALOGE("Cannot add thread, no record of session with ID %s",
	sessionId.toString().c_str());
	return;
	}
	session = it->second;
	}

	if (incoming) {
	LOG_ALWAYS_FATAL_IF(!session->addOutgoingConnection(std::move(clientFd), true),
	"server state must already be initialized");
	return;
	}

	detachGuard.Disable();
	session->preJoinThreadOwnership(std::move(thisThread));
	}

	auto setupResult = session->preJoinSetup(std::move(clientFd));

	// avoid strong cycle
	server = nullptr;

	RpcSession::join(std::move(session), std::move(setupResult));
	}

	bool RpcServer::setupSocketServer(const RpcSocketAddress& addr) {
	LOG_RPC_DETAIL("Setting up socket server %s", addr.toString().c_str());
	LOG_ALWAYS_FATAL_IF(hasServer(), "Each RpcServer can only have one server.");

	unique_fd serverFd(
	TEMP_FAILURE_RETRY(socket(addr.addr()->sa_family, SOCK_STREAM \| SOCK_CLOEXEC, 0)));
	if (serverFd == -1) {
	ALOGE("Could not create socket: %s", strerror(errno));
	return false;
	}

	if (0 != TEMP_FAILURE_RETRY(bind(serverFd.get(), addr.addr(), addr.addrSize()))) {
	int savedErrno = errno;
	ALOGE("Could not bind socket at %s: %s", addr.toString().c_str(), strerror(savedErrno));
	return false;
	}

	// Right now, we create all threads at once, making accept4 slow. To avoid hanging the client,
	// the backlog is increased to a large number.
	// TODO(b/189955605): Once we create threads dynamically & lazily, the backlog can be reduced
	// to 1.
	if (0 != TEMP_FAILURE_RETRY(listen(serverFd.get(), 50 /backlog/))) {
	int savedErrno = errno;
	ALOGE("Could not listen socket at %s: %s", addr.toString().c_str(), strerror(savedErrno));
	return false;
	}

	LOG_RPC_DETAIL("Successfully setup socket server %s", addr.toString().c_str());

	if (!setupExternalServer(std::move(serverFd))) {
	ALOGE("Another thread has set up server while calling setupSocketServer. Race?");
	return false;
	}
	return true;
	}

	void RpcServer::onSessionLockedAllIncomingThreadsEnded(const sp<RpcSession>& session) {
	auto id = session->mId;
	LOG_ALWAYS_FATAL_IF(id == std::nullopt, "Server sessions must be initialized with ID");
	LOG_RPC_DETAIL("Dropping session with address %s", id->toString().c_str());

	std::lock_guard<std::mutex> _l(mLock);
	auto it = mSessions.find(*id);
	LOG_ALWAYS_FATAL_IF(it == mSessions.end(), "Bad state, unknown session id %s",
	id->toString().c_str());
	LOG_ALWAYS_FATAL_IF(it->second != session, "Bad state, session has id mismatch %s",
	id->toString().c_str());
	(void)mSessions.erase(it);
	}

	void RpcServer::onSessionIncomingThreadEnded() {
	mShutdownCv.notify_all();
	}

	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