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* Copyright (C) 2019 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
// Include qemu_pipe.h before sysdeps, since it has inlined references to open, read, write.
#include <qemu_pipe.h>
#include "socket_spec.h"
#include "sysdeps.h"
#include "transport.h"
#include <android-base/properties.h>
#include "adb_io.h"
#include "adb_trace.h"
#include "adb_unique_fd.h"
/* 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.
void qemu_socket_thread(std::string_view addr) {
/* '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";
char tmp[256];
char con_name[32];
adb_thread_setname("qemu socket");
D("transport: qemu_socket_thread() starting");
std::string error;
int port = get_host_socket_spec_port(addr, &error);
if (port == -1) {
/* adb QEMUD service connection request. */
snprintf(con_name, sizeof(con_name), "pipe:qemud:adb:%d", port);
/* Connect to the adb QEMUD service. */
unique_fd 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, adb_listen, addr).detach();
while (true) {
* Wait till the host creates a new connection.
/* Send the 'accept' request. */
if (WriteFdExactly(fd.get(), _accept_req, strlen(_accept_req))) {
/* Wait for the response. In the response we expect 'ok' on success,
* or 'ko' on failure. */
if (!ReadFdExactly(fd.get(), tmp, 2) || memcmp(tmp, _ok_resp, 2)) {
D("Accepting ADB host connection has failed.");
} else {
/* Host is connected. Register the transport, and start the
* exchange. */
std::string serial = android::base::StringPrintf("host-%d", fd.get());
WriteFdExactly(fd.get(), _start_req, strlen(_start_req));
std::move(fd), std::move(serial), port, 1,
[](atransport*) { return ReconnectResult::Abort; }, false);
/* Prepare for accepting of the next ADB host connection. */
if (fd < 0) {
D("adb service become unavailable.");
} else {
D("Unable to send the '%s' request to ADB service.", _accept_req);
D("transport: qemu_socket_thread() exiting");
// If adbd is running inside the emulator, it will normally use QEMUD pipe (aka
// goldfish) as the transport. This is explicitly set by the
// service.adb.transport property.
bool use_qemu_goldfish() {
return android::base::GetProperty("service.adb.transport", "") == "goldfish";