transport_local.cpp - SHIFTPHONES/android_packages_modules_adb - Gitiles

 /*
  * Copyright (C) 2007 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 TRACE_TAG TRANSPORT

 #include "sysdeps.h"
 #include "transport.h"

 #include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>

 #include <condition_variable>
 #include <mutex>
 #include <thread>
 #include <unordered_map>
 #include <vector>

 #include <android-base/parsenetaddress.h>
 #include <android-base/stringprintf.h>
 #include <android-base/thread_annotations.h>
 #include <cutils/sockets.h>

 #if !ADB_HOST
 #include <android-base/properties.h>
 #endif

 #include "adb.h"
 #include "adb_io.h"
 #include "adb_unique_fd.h"
 #include "adb_utils.h"
 #include "sysdeps/chrono.h"
 #include "sysdeps/memory.h"

 #if ADB_HOST

 // Android Wear has been using port 5601 in all of its documentation/tooling,
 // but we search for emulators on ports [5554, 5555 + ADB_LOCAL_TRANSPORT_MAX].
 // Avoid stomping on their port by limiting the number of emulators that can be
 // connected.
 #define ADB_LOCAL_TRANSPORT_MAX 16

 static std::mutex& local_transports_lock = *new std::mutex();

 // We keep a map from emulator port to transport.
 // TODO: weak_ptr?
 static auto& local_transports GUARDED_BY(local_transports_lock) =
     *new std::unordered_map<int, atransport*>();
 #endif /* ADB_HOST */

 bool local_connect(int port) {
     std::string dummy;
     return local_connect_arbitrary_ports(port - 1, port, &dummy) == 0;
 }

 void connect_device(const std::string& address, std::string* response) {
     if (address.empty()) {
         *response = "empty address";
         return;
     }

     std::string serial;
     std::string host;
     int port = DEFAULT_ADB_LOCAL_TRANSPORT_PORT;
     if (!android::base::ParseNetAddress(address, &host, &port, &serial, response)) {
         return;
     }

     std::string error;
     int fd = network_connect(host.c_str(), port, SOCK_STREAM, 10, &error);
     if (fd == -1) {
         *response = android::base::StringPrintf("unable to connect to %s: %s",
                                                 serial.c_str(), error.c_str());
         return;
     }

     D("client: connected %s remote on fd %d", serial.c_str(), fd);
     close_on_exec(fd);
     disable_tcp_nagle(fd);

     // Send a TCP keepalive ping to the device every second so we can detect disconnects.
     if (!set_tcp_keepalive(fd, 1)) {
         D("warning: failed to configure TCP keepalives (%s)", strerror(errno));
     }

     int ret = register_socket_transport(fd, serial.c_str(), port, 0);
     if (ret < 0) {
         adb_close(fd);
         *response = android::base::StringPrintf("already connected to %s", serial.c_str());
     } else {
         *response = android::base::StringPrintf("connected to %s", serial.c_str());
     }
 }


 int local_connect_arbitrary_ports(int console_port, int adb_port, std::string* error) {
     int fd = -1;

 #if ADB_HOST
     if (find_emulator_transport_by_adb_port(adb_port) != nullptr ||
         find_emulator_transport_by_console_port(console_port) != nullptr) {
         return -1;
     }

     const char *host = getenv("ADBHOST");
     if (host) {
         fd = network_connect(host, adb_port, SOCK_STREAM, 0, error);
     }
 #endif
     if (fd < 0) {
         fd = network_loopback_client(adb_port, SOCK_STREAM, error);
     }

     if (fd >= 0) {
         D("client: connected on remote on fd %d", fd);
         close_on_exec(fd);
         disable_tcp_nagle(fd);
         std::string serial = getEmulatorSerialString(console_port);
         if (register_socket_transport(fd, serial.c_str(), adb_port, 1) == 0) {
             return 0;
         }
         adb_close(fd);
     }
     return -1;
 }

 #if ADB_HOST

 static void PollAllLocalPortsForEmulator() {
     int port = DEFAULT_ADB_LOCAL_TRANSPORT_PORT;
     int count = ADB_LOCAL_TRANSPORT_MAX;

     // Try to connect to any number of running emulator instances.
     for ( ; count > 0; count--, port += 2 ) {
         local_connect(port);
     }
 }

 // Retry the disconnected local port for 60 times, and sleep 1 second between two retries.
 constexpr uint32_t LOCAL_PORT_RETRY_COUNT = 60;
 constexpr auto LOCAL_PORT_RETRY_INTERVAL = 1s;

 struct RetryPort {
     int port;
     uint32_t retry_count;
 };

 // Retry emulators just kicked.
 static std::vector<RetryPort>& retry_ports = *new std::vector<RetryPort>;
 std::mutex &retry_ports_lock = *new std::mutex;
 std::condition_variable &retry_ports_cond = *new std::condition_variable;

 static void client_socket_thread(int) {
     adb_thread_setname("client_socket_thread");
     D("transport: client_socket_thread() starting");
     PollAllLocalPortsForEmulator();
     while (true) {
         std::vector<RetryPort> ports;
         // Collect retry ports.
         {
             std::unique_lock<std::mutex> lock(retry_ports_lock);
             while (retry_ports.empty()) {
                 retry_ports_cond.wait(lock);
             }
             retry_ports.swap(ports);
         }
         // Sleep here instead of the end of loop, because if we immediately try to reconnect
         // the emulator just kicked, the adbd on the emulator may not have time to remove the
         // just kicked transport.
         std::this_thread::sleep_for(LOCAL_PORT_RETRY_INTERVAL);

         // Try connecting retry ports.
         std::vector<RetryPort> next_ports;
         for (auto& port : ports) {
             VLOG(TRANSPORT) << "retry port " << port.port << ", last retry_count "
                 << port.retry_count;
             if (local_connect(port.port)) {
                 VLOG(TRANSPORT) << "retry port " << port.port << " successfully";
                 continue;
             }
             if (--port.retry_count > 0) {
                 next_ports.push_back(port);
             } else {
                 VLOG(TRANSPORT) << "stop retrying port " << port.port;
             }
         }

         // Copy back left retry ports.
         {
             std::unique_lock<std::mutex> lock(retry_ports_lock);
             retry_ports.insert(retry_ports.end(), next_ports.begin(), next_ports.end());
         }
     }
 }

 #else // ADB_HOST

 static void server_socket_thread(int port) {
     int serverfd, fd;

     adb_thread_setname("server socket");
     D("transport: server_socket_thread() starting");
     serverfd = -1;
     for(;;) {
         if(serverfd == -1) {
             std::string error;
             serverfd = network_inaddr_any_server(port, SOCK_STREAM, &error);
             if(serverfd < 0) {
                 D("server: cannot bind socket yet: %s", error.c_str());
                 std::this_thread::sleep_for(1s);
                 continue;
             }
             close_on_exec(serverfd);
         }

         D("server: trying to get new connection from %d", port);
         fd = adb_socket_accept(serverfd, nullptr, nullptr);
         if(fd >= 0) {
             D("server: new connection on fd %d", fd);
             close_on_exec(fd);
             disable_tcp_nagle(fd);
             std::string serial = android::base::StringPrintf("host-%d", fd);
             if (register_socket_transport(fd, serial.c_str(), port, 1) != 0) {
                 adb_close(fd);
             }
         }
     }
     D("transport: server_socket_thread() exiting");
 }

 /* This is relevant only for ADB daemon running inside the emulator. */
 /*
  * Redefine open and write for qemu_pipe.h that contains inlined references
  * to those routines. We will redefine them back after qemu_pipe.h inclusion.
  */
 #undef open
 #undef read
 #undef write
 #define open    adb_open
 #define read    adb_read
 #define write   adb_write
 #include <qemu_pipe.h>
 #undef open
 #undef read
 #undef write
 #define open    ___xxx_open
 #define read    ___xxx_read
 #define write   ___xxx_write

 /* A worker thread that monitors host connections, and registers a transport for
  * every new host connection. This thread replaces server_socket_thread on
  * condition that adbd daemon runs inside the emulator, and emulator uses QEMUD
  * pipe to communicate with adbd daemon inside the guest. This is done in order
  * to provide more robust communication channel between ADB host and guest. The
  * main issue with server_socket_thread approach is that it runs on top of TCP,
  * and thus is sensitive to network disruptions. For instance, the
  * ConnectionManager may decide to reset all network connections, in which case
  * the connection between ADB host and guest will be lost. To make ADB traffic
  * independent from the network, we use here 'adb' QEMUD service to transfer data
  * between the host, and the guest. See external/qemu/android/adb-*.* that
  * implements the emulator's side of the protocol. Another advantage of using
  * QEMUD approach is that ADB will be up much sooner, since it doesn't depend
  * anymore on network being set up.
  * The guest side of the protocol contains the following phases:
  * - Connect with adb QEMUD service. In this phase a handle to 'adb' QEMUD service
  *   is opened, and it becomes clear whether or not emulator supports that
  *   protocol.
  * - Wait for the ADB host to create connection with the guest. This is done by
  *   sending an 'accept' request to the adb QEMUD service, and waiting on
  *   response.
  * - When new ADB host connection is accepted, the connection with adb QEMUD
  *   service is registered as the transport, and a 'start' request is sent to the
  *   adb QEMUD service, indicating that the guest is ready to receive messages.
  *   Note that the guest will ignore messages sent down from the emulator before
  *   the transport registration is completed. That's why we need to send the
  *   'start' request after the transport is registered.
  */
 static void qemu_socket_thread(int port) {
     /* 'accept' request to the adb QEMUD service. */
     static const char _accept_req[] = "accept";
     /* 'start' request to the adb QEMUD service. */
     static const char _start_req[] = "start";
     /* 'ok' reply from the adb QEMUD service. */
     static const char _ok_resp[] = "ok";

     int fd;
     char tmp[256];
     char con_name[32];

     adb_thread_setname("qemu socket");
     D("transport: qemu_socket_thread() starting");

     /* adb QEMUD service connection request. */
     snprintf(con_name, sizeof(con_name), "pipe:qemud:adb:%d", port);

     /* Connect to the adb QEMUD service. */
     fd = qemu_pipe_open(con_name);
     if (fd < 0) {
         /* This could be an older version of the emulator, that doesn't
          * implement adb QEMUD service. Fall back to the old TCP way. */
         D("adb service is not available. Falling back to TCP socket.");
         std::thread(server_socket_thread, port).detach();
         return;
     }

     for(;;) {
         /*
          * Wait till the host creates a new connection.
          */

         /* Send the 'accept' request. */
         if (WriteFdExactly(fd, _accept_req, strlen(_accept_req))) {
             /* Wait for the response. In the response we expect 'ok' on success,
              * or 'ko' on failure. */
             if (!ReadFdExactly(fd, tmp, 2) || memcmp(tmp, _ok_resp, 2)) {
                 D("Accepting ADB host connection has failed.");
                 adb_close(fd);
             } else {
                 /* Host is connected. Register the transport, and start the
                  * exchange. */
                 std::string serial = android::base::StringPrintf("host-%d", fd);
                 if (register_socket_transport(fd, serial.c_str(), port, 1) != 0 ||
                     !WriteFdExactly(fd, _start_req, strlen(_start_req))) {
                     adb_close(fd);
                 }
             }

             /* Prepare for accepting of the next ADB host connection. */
             fd = qemu_pipe_open(con_name);
             if (fd < 0) {
                 D("adb service become unavailable.");
                 return;
             }
         } else {
             D("Unable to send the '%s' request to ADB service.", _accept_req);
             return;
         }
     }
     D("transport: qemu_socket_thread() exiting");
     return;
 }

 // If adbd is running inside the emulator, it will normally use QEMUD pipe (aka
 // goldfish) as the transport. This can either be explicitly set by the
 // service.adb.transport property, or be inferred from ro.kernel.qemu that is
 // set to "1" for ranchu/goldfish.
 static bool use_qemu_goldfish() {
     // Legacy way to detect if adbd should use the goldfish pipe is to check for
     // ro.kernel.qemu, keep that behaviour for backward compatibility.
     if (android::base::GetBoolProperty("ro.kernel.qemu", false)) {
         return true;
     }
     // If service.adb.transport is present and is set to "goldfish", use the
     // QEMUD pipe.
     if (android::base::GetProperty("service.adb.transport", "") == "goldfish") {
         return true;
     }
     return false;
 }

 #endif  // !ADB_HOST

 void local_init(int port)
 {
     void (*func)(int);
     const char* debug_name = "";

 #if ADB_HOST
     func = client_socket_thread;
     debug_name = "client";
 #else
     // For the adbd daemon in the system image we need to distinguish
     // between the device, and the emulator.
     func = use_qemu_goldfish() ? qemu_socket_thread : server_socket_thread;
     debug_name = "server";
 #endif // !ADB_HOST

     D("transport: local %s init", debug_name);
     std::thread(func, port).detach();
 }

 #if ADB_HOST
 struct EmulatorConnection : public FdConnection {
     EmulatorConnection(unique_fd fd, int local_port)
         : FdConnection(std::move(fd)), local_port_(local_port) {}

     ~EmulatorConnection() {
         VLOG(TRANSPORT) << "remote_close, local_port = " << local_port_;
         std::unique_lock<std::mutex> lock(retry_ports_lock);
         RetryPort port;
         port.port = local_port_;
         port.retry_count = LOCAL_PORT_RETRY_COUNT;
         retry_ports.push_back(port);
         retry_ports_cond.notify_one();
     }

     void Close() override {
         std::lock_guard<std::mutex> lock(local_transports_lock);
         local_transports.erase(local_port_);
         FdConnection::Close();
     }

     int local_port_;
 };

 /* Only call this function if you already hold local_transports_lock. */
 static atransport* find_emulator_transport_by_adb_port_locked(int adb_port)
     REQUIRES(local_transports_lock) {
     auto it = local_transports.find(adb_port);
     if (it == local_transports.end()) {
         return nullptr;
     }
     return it->second;
 }

 std::string getEmulatorSerialString(int console_port) {
     return android::base::StringPrintf("emulator-%d", console_port);
 }

 atransport* find_emulator_transport_by_adb_port(int adb_port) {
     std::lock_guard<std::mutex> lock(local_transports_lock);
     return find_emulator_transport_by_adb_port_locked(adb_port);
 }

 atransport* find_emulator_transport_by_console_port(int console_port) {
     return find_transport(getEmulatorSerialString(console_port).c_str());
 }
 #endif

 int init_socket_transport(atransport* t, int s, int adb_port, int local) {
     int fail = 0;

     unique_fd fd(s);
     t->type = kTransportLocal;

 #if ADB_HOST
     // Emulator connection.
     if (local) {
         auto emulator_connection = std::make_unique<EmulatorConnection>(std::move(fd), adb_port);
         t->connection = std::make_unique<BlockingConnectionAdapter>(std::move(emulator_connection));
         std::lock_guard<std::mutex> lock(local_transports_lock);
         atransport* existing_transport = find_emulator_transport_by_adb_port_locked(adb_port);
         if (existing_transport != NULL) {
             D("local transport for port %d already registered (%p)?", adb_port, existing_transport);
             fail = -1;
         } else if (local_transports.size() >= ADB_LOCAL_TRANSPORT_MAX) {
             // Too many emulators.
             D("cannot register more emulators. Maximum is %d", ADB_LOCAL_TRANSPORT_MAX);
             fail = -1;
         } else {
             local_transports[adb_port] = t;
         }

         return fail;
     }
 #endif

     // Regular tcp connection.
     auto fd_connection = std::make_unique<FdConnection>(std::move(fd));
     t->connection = std::make_unique<BlockingConnectionAdapter>(std::move(fd_connection));
     return fail;
 }
	/*
	* Copyright (C) 2007 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 TRACE_TAG TRANSPORT

	#include "sysdeps.h"
	#include "transport.h"

	#include <errno.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <sys/types.h>

	#include <condition_variable>
	#include <mutex>
	#include <thread>
	#include <unordered_map>
	#include <vector>

	#include <android-base/parsenetaddress.h>
	#include <android-base/stringprintf.h>
	#include <android-base/thread_annotations.h>
	#include <cutils/sockets.h>

	#if !ADB_HOST
	#include <android-base/properties.h>
	#endif

	#include "adb.h"
	#include "adb_io.h"
	#include "adb_unique_fd.h"
	#include "adb_utils.h"
	#include "sysdeps/chrono.h"
	#include "sysdeps/memory.h"

	#if ADB_HOST

	// Android Wear has been using port 5601 in all of its documentation/tooling,
	// but we search for emulators on ports [5554, 5555 + ADB_LOCAL_TRANSPORT_MAX].
	// Avoid stomping on their port by limiting the number of emulators that can be
	// connected.
	#define ADB_LOCAL_TRANSPORT_MAX 16

	static std::mutex& local_transports_lock = *new std::mutex();

	// We keep a map from emulator port to transport.
	// TODO: weak_ptr?
	static auto& local_transports GUARDED_BY(local_transports_lock) =
	new std::unordered_map<int, atransport>();
	#endif /* ADB_HOST */

	bool local_connect(int port) {
	std::string dummy;
	return local_connect_arbitrary_ports(port - 1, port, &dummy) == 0;
	}

	void connect_device(const std::string& address, std::string* response) {
	if (address.empty()) {
	*response = "empty address";
	return;
	}

	std::string serial;
	std::string host;
	int port = DEFAULT_ADB_LOCAL_TRANSPORT_PORT;
	if (!android::base::ParseNetAddress(address, &host, &port, &serial, response)) {
	return;
	}

	std::string error;
	int fd = network_connect(host.c_str(), port, SOCK_STREAM, 10, &error);
	if (fd == -1) {
	*response = android::base::StringPrintf("unable to connect to %s: %s",
	serial.c_str(), error.c_str());
	return;
	}

	D("client: connected %s remote on fd %d", serial.c_str(), fd);
	close_on_exec(fd);
	disable_tcp_nagle(fd);

	// Send a TCP keepalive ping to the device every second so we can detect disconnects.
	if (!set_tcp_keepalive(fd, 1)) {
	D("warning: failed to configure TCP keepalives (%s)", strerror(errno));
	}

	int ret = register_socket_transport(fd, serial.c_str(), port, 0);
	if (ret < 0) {
	adb_close(fd);
	*response = android::base::StringPrintf("already connected to %s", serial.c_str());
	} else {
	*response = android::base::StringPrintf("connected to %s", serial.c_str());
	}
	}


	int local_connect_arbitrary_ports(int console_port, int adb_port, std::string* error) {
	int fd = -1;

	#if ADB_HOST
	if (find_emulator_transport_by_adb_port(adb_port) != nullptr \|\|
	find_emulator_transport_by_console_port(console_port) != nullptr) {
	return -1;
	}

	const char *host = getenv("ADBHOST");
	if (host) {
	fd = network_connect(host, adb_port, SOCK_STREAM, 0, error);
	}
	#endif
	if (fd < 0) {
	fd = network_loopback_client(adb_port, SOCK_STREAM, error);
	}

	if (fd >= 0) {
	D("client: connected on remote on fd %d", fd);
	close_on_exec(fd);
	disable_tcp_nagle(fd);
	std::string serial = getEmulatorSerialString(console_port);
	if (register_socket_transport(fd, serial.c_str(), adb_port, 1) == 0) {
	return 0;
	}
	adb_close(fd);
	}
	return -1;
	}

	#if ADB_HOST

	static void PollAllLocalPortsForEmulator() {
	int port = DEFAULT_ADB_LOCAL_TRANSPORT_PORT;
	int count = ADB_LOCAL_TRANSPORT_MAX;

	// Try to connect to any number of running emulator instances.
	for ( ; count > 0; count--, port += 2 ) {
	local_connect(port);
	}
	}

	// Retry the disconnected local port for 60 times, and sleep 1 second between two retries.
	constexpr uint32_t LOCAL_PORT_RETRY_COUNT = 60;
	constexpr auto LOCAL_PORT_RETRY_INTERVAL = 1s;

	struct RetryPort {
	int port;
	uint32_t retry_count;
	};

	// Retry emulators just kicked.
	static std::vector<RetryPort>& retry_ports = *new std::vector<RetryPort>;
	std::mutex &retry_ports_lock = *new std::mutex;
	std::condition_variable &retry_ports_cond = *new std::condition_variable;

	static void client_socket_thread(int) {
	adb_thread_setname("client_socket_thread");
	D("transport: client_socket_thread() starting");
	PollAllLocalPortsForEmulator();
	while (true) {
	std::vector<RetryPort> ports;
	// Collect retry ports.
	{
	std::unique_lock<std::mutex> lock(retry_ports_lock);
	while (retry_ports.empty()) {
	retry_ports_cond.wait(lock);
	}
	retry_ports.swap(ports);
	}
	// Sleep here instead of the end of loop, because if we immediately try to reconnect
	// the emulator just kicked, the adbd on the emulator may not have time to remove the
	// just kicked transport.
	std::this_thread::sleep_for(LOCAL_PORT_RETRY_INTERVAL);

	// Try connecting retry ports.
	std::vector<RetryPort> next_ports;
	for (auto& port : ports) {
	VLOG(TRANSPORT) << "retry port " << port.port << ", last retry_count "
	<< port.retry_count;
	if (local_connect(port.port)) {
	VLOG(TRANSPORT) << "retry port " << port.port << " successfully";
	continue;
	}
	if (--port.retry_count > 0) {
	next_ports.push_back(port);
	} else {
	VLOG(TRANSPORT) << "stop retrying port " << port.port;
	}
	}

	// Copy back left retry ports.
	{
	std::unique_lock<std::mutex> lock(retry_ports_lock);
	retry_ports.insert(retry_ports.end(), next_ports.begin(), next_ports.end());
	}
	}
	}

	#else // ADB_HOST

	static void server_socket_thread(int port) {
	int serverfd, fd;

	adb_thread_setname("server socket");
	D("transport: server_socket_thread() starting");
	serverfd = -1;
	for(;;) {
	if(serverfd == -1) {
	std::string error;
	serverfd = network_inaddr_any_server(port, SOCK_STREAM, &error);
	if(serverfd < 0) {
	D("server: cannot bind socket yet: %s", error.c_str());
	std::this_thread::sleep_for(1s);
	continue;
	}
	close_on_exec(serverfd);
	}

	D("server: trying to get new connection from %d", port);
	fd = adb_socket_accept(serverfd, nullptr, nullptr);
	if(fd >= 0) {
	D("server: new connection on fd %d", fd);
	close_on_exec(fd);
	disable_tcp_nagle(fd);
	std::string serial = android::base::StringPrintf("host-%d", fd);
	if (register_socket_transport(fd, serial.c_str(), port, 1) != 0) {
	adb_close(fd);
	}
	}
	}
	D("transport: server_socket_thread() exiting");
	}

	/* This is relevant only for ADB daemon running inside the emulator. */
	/*
	* Redefine open and write for qemu_pipe.h that contains inlined references
	* to those routines. We will redefine them back after qemu_pipe.h inclusion.
	*/
	#undef open
	#undef read
	#undef write
	#define open adb_open
	#define read adb_read
	#define write adb_write
	#include <qemu_pipe.h>
	#undef open
	#undef read
	#undef write
	#define open ___xxx_open
	#define read ___xxx_read
	#define write ___xxx_write

	/* A worker thread that monitors host connections, and registers a transport for
	* every new host connection. This thread replaces server_socket_thread on
	* condition that adbd daemon runs inside the emulator, and emulator uses QEMUD
	* pipe to communicate with adbd daemon inside the guest. This is done in order
	* to provide more robust communication channel between ADB host and guest. The
	* main issue with server_socket_thread approach is that it runs on top of TCP,
	* and thus is sensitive to network disruptions. For instance, the
	* ConnectionManager may decide to reset all network connections, in which case
	* the connection between ADB host and guest will be lost. To make ADB traffic
	* independent from the network, we use here 'adb' QEMUD service to transfer data
	* between the host, and the guest. See external/qemu/android/adb-. that
	* implements the emulator's side of the protocol. Another advantage of using
	* QEMUD approach is that ADB will be up much sooner, since it doesn't depend
	* anymore on network being set up.
	* The guest side of the protocol contains the following phases:
	* - Connect with adb QEMUD service. In this phase a handle to 'adb' QEMUD service
	* is opened, and it becomes clear whether or not emulator supports that
	* protocol.
	* - Wait for the ADB host to create connection with the guest. This is done by
	* sending an 'accept' request to the adb QEMUD service, and waiting on
	* response.
	* - When new ADB host connection is accepted, the connection with adb QEMUD
	* service is registered as the transport, and a 'start' request is sent to the
	* adb QEMUD service, indicating that the guest is ready to receive messages.
	* Note that the guest will ignore messages sent down from the emulator before
	* the transport registration is completed. That's why we need to send the
	* 'start' request after the transport is registered.
	*/
	static void qemu_socket_thread(int port) {
	/* 'accept' request to the adb QEMUD service. */
	static const char _accept_req[] = "accept";
	/* 'start' request to the adb QEMUD service. */
	static const char _start_req[] = "start";
	/* 'ok' reply from the adb QEMUD service. */
	static const char _ok_resp[] = "ok";

	int fd;
	char tmp[256];
	char con_name[32];

	adb_thread_setname("qemu socket");
	D("transport: qemu_socket_thread() starting");

	/* adb QEMUD service connection request. */
	snprintf(con_name, sizeof(con_name), "pipe:qemud:adb:%d", port);

	/* Connect to the adb QEMUD service. */
	fd = qemu_pipe_open(con_name);
	if (fd < 0) {
	/* This could be an older version of the emulator, that doesn't
	* implement adb QEMUD service. Fall back to the old TCP way. */
	D("adb service is not available. Falling back to TCP socket.");
	std::thread(server_socket_thread, port).detach();
	return;
	}

	for(;;) {
	/*
	* Wait till the host creates a new connection.
	*/

	/* Send the 'accept' request. */
	if (WriteFdExactly(fd, _accept_req, strlen(_accept_req))) {
	/* Wait for the response. In the response we expect 'ok' on success,
	* or 'ko' on failure. */
	if (!ReadFdExactly(fd, tmp, 2) \|\| memcmp(tmp, _ok_resp, 2)) {
	D("Accepting ADB host connection has failed.");
	adb_close(fd);
	} else {
	/* Host is connected. Register the transport, and start the
	* exchange. */
	std::string serial = android::base::StringPrintf("host-%d", fd);
	if (register_socket_transport(fd, serial.c_str(), port, 1) != 0 \|\|
	!WriteFdExactly(fd, _start_req, strlen(_start_req))) {
	adb_close(fd);
	}
	}

	/* Prepare for accepting of the next ADB host connection. */
	fd = qemu_pipe_open(con_name);
	if (fd < 0) {
	D("adb service become unavailable.");
	return;
	}
	} else {
	D("Unable to send the '%s' request to ADB service.", _accept_req);
	return;
	}
	}
	D("transport: qemu_socket_thread() exiting");
	return;
	}

	// If adbd is running inside the emulator, it will normally use QEMUD pipe (aka
	// goldfish) as the transport. This can either be explicitly set by the
	// service.adb.transport property, or be inferred from ro.kernel.qemu that is
	// set to "1" for ranchu/goldfish.
	static bool use_qemu_goldfish() {
	// Legacy way to detect if adbd should use the goldfish pipe is to check for
	// ro.kernel.qemu, keep that behaviour for backward compatibility.
	if (android::base::GetBoolProperty("ro.kernel.qemu", false)) {
	return true;
	}
	// If service.adb.transport is present and is set to "goldfish", use the
	// QEMUD pipe.
	if (android::base::GetProperty("service.adb.transport", "") == "goldfish") {
	return true;
	}
	return false;
	}

	#endif // !ADB_HOST

	void local_init(int port)
	{
	void (*func)(int);
	const char* debug_name = "";

	#if ADB_HOST
	func = client_socket_thread;
	debug_name = "client";
	#else
	// For the adbd daemon in the system image we need to distinguish
	// between the device, and the emulator.
	func = use_qemu_goldfish() ? qemu_socket_thread : server_socket_thread;
	debug_name = "server";
	#endif // !ADB_HOST

	D("transport: local %s init", debug_name);
	std::thread(func, port).detach();
	}

	#if ADB_HOST
	struct EmulatorConnection : public FdConnection {
	EmulatorConnection(unique_fd fd, int local_port)
	: FdConnection(std::move(fd)), local_port_(local_port) {}

	~EmulatorConnection() {
	VLOG(TRANSPORT) << "remote_close, local_port = " << local_port_;
	std::unique_lock<std::mutex> lock(retry_ports_lock);
	RetryPort port;
	port.port = local_port_;
	port.retry_count = LOCAL_PORT_RETRY_COUNT;
	retry_ports.push_back(port);
	retry_ports_cond.notify_one();
	}

	void Close() override {
	std::lock_guard<std::mutex> lock(local_transports_lock);
	local_transports.erase(local_port_);
	FdConnection::Close();
	}

	int local_port_;
	};

	/* Only call this function if you already hold local_transports_lock. */
	static atransport* find_emulator_transport_by_adb_port_locked(int adb_port)
	REQUIRES(local_transports_lock) {
	auto it = local_transports.find(adb_port);
	if (it == local_transports.end()) {
	return nullptr;
	}
	return it->second;
	}

	std::string getEmulatorSerialString(int console_port) {
	return android::base::StringPrintf("emulator-%d", console_port);
	}

	atransport* find_emulator_transport_by_adb_port(int adb_port) {
	std::lock_guard<std::mutex> lock(local_transports_lock);
	return find_emulator_transport_by_adb_port_locked(adb_port);
	}

	atransport* find_emulator_transport_by_console_port(int console_port) {
	return find_transport(getEmulatorSerialString(console_port).c_str());
	}
	#endif

	int init_socket_transport(atransport* t, int s, int adb_port, int local) {
	int fail = 0;

	unique_fd fd(s);
	t->type = kTransportLocal;

	#if ADB_HOST
	// Emulator connection.
	if (local) {
	auto emulator_connection = std::make_unique<EmulatorConnection>(std::move(fd), adb_port);
	t->connection = std::make_unique<BlockingConnectionAdapter>(std::move(emulator_connection));
	std::lock_guard<std::mutex> lock(local_transports_lock);
	atransport* existing_transport = find_emulator_transport_by_adb_port_locked(adb_port);
	if (existing_transport != NULL) {
	D("local transport for port %d already registered (%p)?", adb_port, existing_transport);
	fail = -1;
	} else if (local_transports.size() >= ADB_LOCAL_TRANSPORT_MAX) {
	// Too many emulators.
	D("cannot register more emulators. Maximum is %d", ADB_LOCAL_TRANSPORT_MAX);
	fail = -1;
	} else {
	local_transports[adb_port] = t;
	}

	return fail;
	}
	#endif

	// Regular tcp connection.
	auto fd_connection = std::make_unique<FdConnection>(std::move(fd));
	t->connection = std::make_unique<BlockingConnectionAdapter>(std::move(fd_connection));
	return fail;
	}