xref: /aosp14/system/core/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.cpp

/*
 * 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.
 */

#include <arpa/inet.h>
#include <cutils/sockets.h>
#include <errno.h>
#include <netinet/in.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

#include <android-base/cmsg.h>
#include <android-base/logging.h>
#include <android-base/properties.h>
#include <android-base/scopeguard.h>
#include <android-base/strings.h>
#include <fs_mgr/file_wait.h>
#include <snapuserd/snapuserd_client.h>
#include "snapuserd_server.h"

#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
#include <sys/_system_properties.h>

namespace android {
namespace snapshot {

using namespace std::string_literals;

using android::base::borrowed_fd;
using android::base::unique_fd;

DaemonOps UserSnapshotServer::Resolveop(std::string& input) {
    if (input == "init") return DaemonOps::INIT;
    if (input == "start") return DaemonOps::START;
    if (input == "stop") return DaemonOps::STOP;
    if (input == "query") return DaemonOps::QUERY;
    if (input == "delete") return DaemonOps::DELETE;
    if (input == "detach") return DaemonOps::DETACH;
    if (input == "supports") return DaemonOps::SUPPORTS;
    if (input == "initiate_merge") return DaemonOps::INITIATE;
    if (input == "merge_percent") return DaemonOps::PERCENTAGE;
    if (input == "getstatus") return DaemonOps::GETSTATUS;
    if (input == "update-verify") return DaemonOps::UPDATE_VERIFY;

    return DaemonOps::INVALID;
}

UserSnapshotServer::UserSnapshotServer() {
    monitor_merge_event_fd_.reset(eventfd(0, EFD_CLOEXEC));
    if (monitor_merge_event_fd_ == -1) {
        PLOG(FATAL) << "monitor_merge_event_fd_: failed to create eventfd";
    }
    terminating_ = false;
}

UserSnapshotServer::~UserSnapshotServer() {
    // Close any client sockets that were added via AcceptClient().
    for (size_t i = 1; i < watched_fds_.size(); i++) {
        close(watched_fds_[i].fd);
    }
}

std::string UserSnapshotServer::GetDaemonStatus() {
    std::string msg = "";

    if (IsTerminating())
        msg = "passive";
    else
        msg = "active";

    return msg;
}

void UserSnapshotServer::Parsemsg(std::string const& msg, const char delim,
                                  std::vector<std::string>& out) {
    std::stringstream ss(msg);
    std::string s;

    while (std::getline(ss, s, delim)) {
        out.push_back(s);
    }
}

void UserSnapshotServer::ShutdownThreads() {
    terminating_ = true;
    JoinAllThreads();
}

HandlerThread::HandlerThread(std::shared_ptr<SnapshotHandler> snapuserd)
    : snapuserd_(snapuserd), misc_name_(snapuserd_->GetMiscName()) {}

bool UserSnapshotServer::Sendmsg(android::base::borrowed_fd fd, const std::string& msg) {
    ssize_t ret = TEMP_FAILURE_RETRY(send(fd.get(), msg.data(), msg.size(), MSG_NOSIGNAL));
    if (ret < 0) {
        PLOG(ERROR) << "Snapuserd:server: send() failed";
        return false;
    }

    if (ret < msg.size()) {
        LOG(ERROR) << "Partial send; expected " << msg.size() << " bytes, sent " << ret;
        return false;
    }
    return true;
}

bool UserSnapshotServer::Recv(android::base::borrowed_fd fd, std::string* data) {
    char msg[kMaxPacketSize];
    ssize_t rv = TEMP_FAILURE_RETRY(recv(fd.get(), msg, sizeof(msg), 0));
    if (rv < 0) {
        PLOG(ERROR) << "recv failed";
        return false;
    }
    *data = std::string(msg, rv);
    return true;
}

bool UserSnapshotServer::Receivemsg(android::base::borrowed_fd fd, const std::string& str) {
    const char delim = ',';

    std::vector<std::string> out;
    Parsemsg(str, delim, out);
    DaemonOps op = Resolveop(out[0]);

    switch (op) {
        case DaemonOps::INIT: {
            // Message format:
            // init,<misc_name>,<cow_device_path>,<backing_device>,<base_path_merge>
            //
            // Reads the metadata and send the number of sectors
            if (out.size() != 5) {
                LOG(ERROR) << "Malformed init message, " << out.size() << " parts";
                return Sendmsg(fd, "fail");
            }

            auto handler = AddHandler(out[1], out[2], out[3], out[4]);
            if (!handler) {
                return Sendmsg(fd, "fail");
            }

            auto retval = "success," + std::to_string(handler->snapuserd()->GetNumSectors());
            return Sendmsg(fd, retval);
        }
        case DaemonOps::START: {
            // Message format:
            // start,<misc_name>
            //
            // Start the new thread which binds to dm-user misc device
            if (out.size() != 2) {
                LOG(ERROR) << "Malformed start message, " << out.size() << " parts";
                return Sendmsg(fd, "fail");
            }

            std::lock_guard<std::mutex> lock(lock_);
            auto iter = FindHandler(&lock, out[1]);
            if (iter == dm_users_.end()) {
                LOG(ERROR) << "Could not find handler: " << out[1];
                return Sendmsg(fd, "fail");
            }
            if (!(*iter)->snapuserd() || (*iter)->snapuserd()->IsAttached()) {
                LOG(ERROR) << "Tried to re-attach control device: " << out[1];
                return Sendmsg(fd, "fail");
            }
            if (!StartHandler(*iter)) {
                return Sendmsg(fd, "fail");
            }
            return Sendmsg(fd, "success");
        }
        case DaemonOps::STOP: {
            // Message format: stop
            //
            // Stop all the threads gracefully and then shutdown the
            // main thread
            SetTerminating();
            ShutdownThreads();
            return true;
        }
        case DaemonOps::QUERY: {
            // Message format: query
            //
            // As part of transition, Second stage daemon will be
            // created before terminating the first stage daemon. Hence,
            // for a brief period client may have to distiguish between
            // first stage daemon and second stage daemon.
            //
            // Second stage daemon is marked as active and hence will
            // be ready to receive control message.
            return Sendmsg(fd, GetDaemonStatus());
        }
        case DaemonOps::DELETE: {
            // Message format:
            // delete,<misc_name>
            if (out.size() != 2) {
                LOG(ERROR) << "Malformed delete message, " << out.size() << " parts";
                return Sendmsg(fd, "fail");
            }
            {
                std::lock_guard<std::mutex> lock(lock_);
                auto iter = FindHandler(&lock, out[1]);
                if (iter == dm_users_.end()) {
                    // After merge is completed, we swap dm-user table with
                    // the underlying dm-linear base device. Hence, worker
                    // threads would have terminted and was removed from
                    // the list.
                    LOG(DEBUG) << "Could not find handler: " << out[1];
                    return Sendmsg(fd, "success");
                }

                if (!(*iter)->ThreadTerminated()) {
                    (*iter)->snapuserd()->NotifyIOTerminated();
                }
            }
            if (!RemoveAndJoinHandler(out[1])) {
                return Sendmsg(fd, "fail");
            }
            return Sendmsg(fd, "success");
        }
        case DaemonOps::DETACH: {
            std::lock_guard<std::mutex> lock(lock_);
            TerminateMergeThreads(&lock);
            terminating_ = true;
            return true;
        }
        case DaemonOps::SUPPORTS: {
            if (out.size() != 2) {
                LOG(ERROR) << "Malformed supports message, " << out.size() << " parts";
                return Sendmsg(fd, "fail");
            }
            if (out[1] == "second_stage_socket_handoff") {
                return Sendmsg(fd, "success");
            }
            return Sendmsg(fd, "fail");
        }
        case DaemonOps::INITIATE: {
            if (out.size() != 2) {
                LOG(ERROR) << "Malformed initiate-merge message, " << out.size() << " parts";
                return Sendmsg(fd, "fail");
            }
            if (out[0] == "initiate_merge") {
                std::lock_guard<std::mutex> lock(lock_);
                auto iter = FindHandler(&lock, out[1]);
                if (iter == dm_users_.end()) {
                    LOG(ERROR) << "Could not find handler: " << out[1];
                    return Sendmsg(fd, "fail");
                }

                if (!StartMerge(&lock, *iter)) {
                    return Sendmsg(fd, "fail");
                }

                return Sendmsg(fd, "success");
            }
            return Sendmsg(fd, "fail");
        }
        case DaemonOps::PERCENTAGE: {
            std::lock_guard<std::mutex> lock(lock_);
            double percentage = GetMergePercentage(&lock);

            return Sendmsg(fd, std::to_string(percentage));
        }
        case DaemonOps::GETSTATUS: {
            // Message format:
            // getstatus,<misc_name>
            if (out.size() != 2) {
                LOG(ERROR) << "Malformed delete message, " << out.size() << " parts";
                return Sendmsg(fd, "snapshot-merge-failed");
            }
            {
                std::lock_guard<std::mutex> lock(lock_);
                auto iter = FindHandler(&lock, out[1]);
                if (iter == dm_users_.end()) {
                    LOG(ERROR) << "Could not find handler: " << out[1];
                    return Sendmsg(fd, "snapshot-merge-failed");
                }

                std::string merge_status = GetMergeStatus(*iter);
                return Sendmsg(fd, merge_status);
            }
        }
        case DaemonOps::UPDATE_VERIFY: {
            std::lock_guard<std::mutex> lock(lock_);
            if (!UpdateVerification(&lock)) {
                return Sendmsg(fd, "fail");
            }

            return Sendmsg(fd, "success");
        }
        default: {
            LOG(ERROR) << "Received unknown message type from client";
            Sendmsg(fd, "fail");
            return false;
        }
    }
}

void UserSnapshotServer::RunThread(std::shared_ptr<HandlerThread> handler) {
    LOG(INFO) << "Entering thread for handler: " << handler->misc_name();

    if (!handler->snapuserd()->Start()) {
        LOG(ERROR) << " Failed to launch all worker threads";
    }

    handler->snapuserd()->CloseFds();
    bool merge_completed = handler->snapuserd()->CheckMergeCompletionStatus();
    handler->snapuserd()->UnmapBufferRegion();

    auto misc_name = handler->misc_name();
    LOG(INFO) << "Handler thread about to exit: " << misc_name;

    {
        std::lock_guard<std::mutex> lock(lock_);
        if (merge_completed) {
            num_partitions_merge_complete_ += 1;
            active_merge_threads_ -= 1;
            WakeupMonitorMergeThread();
        }
        handler->SetThreadTerminated();
        auto iter = FindHandler(&lock, handler->misc_name());
        if (iter == dm_users_.end()) {
            // RemoveAndJoinHandler() already removed us from the list, and is
            // now waiting on a join(), so just return. Additionally, release
            // all the resources held by snapuserd object which are shared
            // by worker threads. This should be done when the last reference
            // of "handler" is released; but we will explicitly release here
            // to make sure snapuserd object is freed as it is the biggest
            // consumer of memory in the daemon.
            handler->FreeResources();
            LOG(INFO) << "Exiting handler thread to allow for join: " << misc_name;
            return;
        }

        LOG(INFO) << "Exiting handler thread and freeing resources: " << misc_name;

        if (handler->snapuserd()->IsAttached()) {
            handler->thread().detach();
        }

        // Important: free resources within the lock. This ensures that if
        // WaitForDelete() is called, the handler is either in the list, or
        // it's not and its resources are guaranteed to be freed.
        handler->FreeResources();
        dm_users_.erase(iter);
    }
}

bool UserSnapshotServer::Start(const std::string& socketname) {
    bool start_listening = true;

    sockfd_.reset(android_get_control_socket(socketname.c_str()));
    if (sockfd_ < 0) {
        sockfd_.reset(socket_local_server(socketname.c_str(), ANDROID_SOCKET_NAMESPACE_RESERVED,
                                          SOCK_STREAM));
        if (sockfd_ < 0) {
            PLOG(ERROR) << "Failed to create server socket " << socketname;
            return false;
        }
        start_listening = false;
    }
    return StartWithSocket(start_listening);
}

bool UserSnapshotServer::StartWithSocket(bool start_listening) {
    if (start_listening && listen(sockfd_.get(), 4) < 0) {
        PLOG(ERROR) << "listen socket failed";
        return false;
    }

    AddWatchedFd(sockfd_, POLLIN);
    is_socket_present_ = true;

    // If started in first-stage init, the property service won't be online.
    if (access("/dev/socket/property_service", F_OK) == 0) {
        if (!android::base::SetProperty("snapuserd.ready", "true")) {
            LOG(ERROR) << "Failed to set snapuserd.ready property";
            return false;
        }
    }

    LOG(DEBUG) << "Snapuserd server now accepting connections";
    return true;
}

bool UserSnapshotServer::Run() {
    LOG(INFO) << "Now listening on snapuserd socket";

    while (!IsTerminating()) {
        int rv = TEMP_FAILURE_RETRY(poll(watched_fds_.data(), watched_fds_.size(), -1));
        if (rv < 0) {
            PLOG(ERROR) << "poll failed";
            return false;
        }
        if (!rv) {
            continue;
        }

        if (watched_fds_[0].revents) {
            AcceptClient();
        }

        auto iter = watched_fds_.begin() + 1;
        while (iter != watched_fds_.end()) {
            if (iter->revents && !HandleClient(iter->fd, iter->revents)) {
                close(iter->fd);
                iter = watched_fds_.erase(iter);
            } else {
                iter++;
            }
        }
    }

    JoinAllThreads();
    return true;
}

void UserSnapshotServer::JoinAllThreads() {
    // Acquire the thread list within the lock.
    std::vector<std::shared_ptr<HandlerThread>> dm_users;
    {
        std::lock_guard<std::mutex> guard(lock_);
        dm_users = std::move(dm_users_);
    }

    for (auto& client : dm_users) {
        auto& th = client->thread();

        if (th.joinable()) th.join();
    }

    stop_monitor_merge_thread_ = true;
    WakeupMonitorMergeThread();
}

void UserSnapshotServer::AddWatchedFd(android::base::borrowed_fd fd, int events) {
    struct pollfd p = {};
    p.fd = fd.get();
    p.events = events;
    watched_fds_.emplace_back(std::move(p));
}

void UserSnapshotServer::AcceptClient() {
    int fd = TEMP_FAILURE_RETRY(accept4(sockfd_.get(), nullptr, nullptr, SOCK_CLOEXEC));
    if (fd < 0) {
        PLOG(ERROR) << "accept4 failed";
        return;
    }

    AddWatchedFd(fd, POLLIN);
}

bool UserSnapshotServer::HandleClient(android::base::borrowed_fd fd, int revents) {
    std::string str;
    if (!Recv(fd, &str)) {
        return false;
    }
    if (str.empty() && (revents & POLLHUP)) {
        LOG(DEBUG) << "Snapuserd client disconnected";
        return false;
    }
    if (!Receivemsg(fd, str)) {
        LOG(ERROR) << "Encountered error handling client message, revents: " << revents;
        return false;
    }
    return true;
}

void UserSnapshotServer::Interrupt() {
    // Force close the socket so poll() fails.
    sockfd_ = {};
    SetTerminating();
}

std::shared_ptr<HandlerThread> UserSnapshotServer::AddHandler(const std::string& misc_name,
                                                              const std::string& cow_device_path,
                                                              const std::string& backing_device,
                                                              const std::string& base_path_merge) {
    // We will need multiple worker threads only during
    // device boot after OTA. For all other purposes,
    // one thread is sufficient. We don't want to consume
    // unnecessary memory especially during OTA install phase
    // when daemon will be up during entire post install phase.
    //
    // During boot up, we need multiple threads primarily for
    // update-verification.
    int num_worker_threads = kNumWorkerThreads;
    if (is_socket_present_) {
        num_worker_threads = 1;
    }

    bool perform_verification = true;
    if (android::base::EndsWith(misc_name, "-init") || is_socket_present_) {
        perform_verification = false;
    }

    auto snapuserd = std::make_shared<SnapshotHandler>(misc_name, cow_device_path, backing_device,
                                                       base_path_merge, num_worker_threads,
                                                       io_uring_enabled_, perform_verification);
    if (!snapuserd->InitCowDevice()) {
        LOG(ERROR) << "Failed to initialize Snapuserd";
        return nullptr;
    }

    if (!snapuserd->InitializeWorkers()) {
        LOG(ERROR) << "Failed to initialize workers";
        return nullptr;
    }

    auto handler = std::make_shared<HandlerThread>(snapuserd);
    {
        std::lock_guard<std::mutex> lock(lock_);
        if (FindHandler(&lock, misc_name) != dm_users_.end()) {
            LOG(ERROR) << "Handler already exists: " << misc_name;
            return nullptr;
        }
        dm_users_.push_back(handler);
    }
    return handler;
}

bool UserSnapshotServer::StartHandler(const std::shared_ptr<HandlerThread>& handler) {
    if (handler->snapuserd()->IsAttached()) {
        LOG(ERROR) << "Handler already attached";
        return false;
    }

    handler->snapuserd()->AttachControlDevice();

    handler->thread() = std::thread(std::bind(&UserSnapshotServer::RunThread, this, handler));
    return true;
}

bool UserSnapshotServer::StartMerge(std::lock_guard<std::mutex>* proof_of_lock,
                                    const std::shared_ptr<HandlerThread>& handler) {
    CHECK(proof_of_lock);

    if (!handler->snapuserd()->IsAttached()) {
        LOG(ERROR) << "Handler not attached to dm-user - Merge thread cannot be started";
        return false;
    }

    handler->snapuserd()->MonitorMerge();

    if (!is_merge_monitor_started_.has_value()) {
        std::thread(&UserSnapshotServer::MonitorMerge, this).detach();
        is_merge_monitor_started_ = true;
    }

    merge_handlers_.push(handler);
    WakeupMonitorMergeThread();
    return true;
}

auto UserSnapshotServer::FindHandler(std::lock_guard<std::mutex>* proof_of_lock,
                                     const std::string& misc_name) -> HandlerList::iterator {
    CHECK(proof_of_lock);

    for (auto iter = dm_users_.begin(); iter != dm_users_.end(); iter++) {
        if ((*iter)->misc_name() == misc_name) {
            return iter;
        }
    }
    return dm_users_.end();
}

void UserSnapshotServer::TerminateMergeThreads(std::lock_guard<std::mutex>* proof_of_lock) {
    CHECK(proof_of_lock);

    for (auto iter = dm_users_.begin(); iter != dm_users_.end(); iter++) {
        if (!(*iter)->ThreadTerminated()) {
            (*iter)->snapuserd()->NotifyIOTerminated();
        }
    }
}

std::string UserSnapshotServer::GetMergeStatus(const std::shared_ptr<HandlerThread>& handler) {
    return handler->snapuserd()->GetMergeStatus();
}

double UserSnapshotServer::GetMergePercentage(std::lock_guard<std::mutex>* proof_of_lock) {
    CHECK(proof_of_lock);
    double percentage = 0.0;
    int n = 0;

    for (auto iter = dm_users_.begin(); iter != dm_users_.end(); iter++) {
        auto& th = (*iter)->thread();
        if (th.joinable()) {
            // Merge percentage by individual partitions wherein merge is still
            // in-progress
            percentage += (*iter)->snapuserd()->GetMergePercentage();
            n += 1;
        }
    }

    // Calculate final merge including those partitions where merge was already
    // completed - num_partitions_merge_complete_ will track them when each
    // thread exists in RunThread.
    int total_partitions = n + num_partitions_merge_complete_;

    if (total_partitions) {
        percentage = ((num_partitions_merge_complete_ * 100.0) + percentage) / total_partitions;
    }

    LOG(DEBUG) << "Merge %: " << percentage
               << " num_partitions_merge_complete_: " << num_partitions_merge_complete_
               << " total_partitions: " << total_partitions << " n: " << n;
    return percentage;
}

bool UserSnapshotServer::RemoveAndJoinHandler(const std::string& misc_name) {
    std::shared_ptr<HandlerThread> handler;
    {
        std::lock_guard<std::mutex> lock(lock_);

        auto iter = FindHandler(&lock, misc_name);
        if (iter == dm_users_.end()) {
            // Client already deleted.
            return true;
        }
        handler = std::move(*iter);
        dm_users_.erase(iter);
    }

    auto& th = handler->thread();
    if (th.joinable()) {
        th.join();
    }
    return true;
}

void UserSnapshotServer::WakeupMonitorMergeThread() {
    uint64_t notify = 1;
    ssize_t rc = TEMP_FAILURE_RETRY(write(monitor_merge_event_fd_.get(), &notify, sizeof(notify)));
    if (rc < 0) {
        PLOG(FATAL) << "failed to notify monitor merge thread";
    }
}

void UserSnapshotServer::MonitorMerge() {
    while (!stop_monitor_merge_thread_) {
        uint64_t testVal;
        ssize_t ret =
                TEMP_FAILURE_RETRY(read(monitor_merge_event_fd_.get(), &testVal, sizeof(testVal)));
        if (ret == -1) {
            PLOG(FATAL) << "Failed to read from eventfd";
        } else if (ret == 0) {
            LOG(FATAL) << "Hit EOF on eventfd";
        }

        LOG(INFO) << "MonitorMerge: active-merge-threads: " << active_merge_threads_;
        {
            std::lock_guard<std::mutex> lock(lock_);
            while (active_merge_threads_ < kMaxMergeThreads && merge_handlers_.size() > 0) {
                auto handler = merge_handlers_.front();
                merge_handlers_.pop();

                if (!handler->snapuserd()) {
                    LOG(INFO) << "MonitorMerge: skipping deleted handler: " << handler->misc_name();
                    continue;
                }

                LOG(INFO) << "Starting merge for partition: "
                          << handler->snapuserd()->GetMiscName();
                handler->snapuserd()->InitiateMerge();
                active_merge_threads_ += 1;
            }
        }
    }

    LOG(INFO) << "Exiting MonitorMerge: size: " << merge_handlers_.size();
}

bool UserSnapshotServer::WaitForSocket() {
    auto scope_guard = android::base::make_scope_guard([this]() -> void { JoinAllThreads(); });

    auto socket_path = ANDROID_SOCKET_DIR "/"s + kSnapuserdSocketProxy;

    if (!android::fs_mgr::WaitForFile(socket_path, std::chrono::milliseconds::max())) {
        LOG(ERROR)
                << "Failed to wait for proxy socket, second-stage snapuserd will fail to connect";
        return false;
    }

    // This initialization of system property is important. When daemon is
    // launched post selinux transition (before init second stage),
    // bionic libc initializes system property as part of __libc_init_common();
    // however that initialization fails silently given that fact that we don't
    // have /dev/__properties__ setup which is created at init second stage.
    //
    // At this point, we have the handlers setup and is safe to setup property.
    __system_properties_init();

    if (!android::base::WaitForProperty("snapuserd.proxy_ready", "true")) {
        LOG(ERROR)
                << "Failed to wait for proxy property, second-stage snapuserd will fail to connect";
        return false;
    }

    unique_fd fd(socket_local_client(kSnapuserdSocketProxy, ANDROID_SOCKET_NAMESPACE_RESERVED,
                                     SOCK_SEQPACKET));
    if (fd < 0) {
        PLOG(ERROR) << "Failed to connect to socket proxy";
        return false;
    }

    char code[1];
    std::vector<unique_fd> fds;
    ssize_t rv = android::base::ReceiveFileDescriptorVector(fd, code, sizeof(code), 1, &fds);
    if (rv < 0) {
        PLOG(ERROR) << "Failed to receive server socket over proxy";
        return false;
    }
    if (fds.empty()) {
        LOG(ERROR) << "Expected at least one file descriptor from proxy";
        return false;
    }

    // We don't care if the ACK is received.
    code[0] = 'a';
    if (TEMP_FAILURE_RETRY(send(fd, code, sizeof(code), MSG_NOSIGNAL)) < 0) {
        PLOG(ERROR) << "Failed to send ACK to proxy";
        return false;
    }

    sockfd_ = std::move(fds[0]);
    if (!StartWithSocket(true)) {
        return false;
    }

    return Run();
}

bool UserSnapshotServer::RunForSocketHandoff() {
    unique_fd proxy_fd(android_get_control_socket(kSnapuserdSocketProxy));
    if (proxy_fd < 0) {
        PLOG(FATAL) << "Proxy could not get android control socket " << kSnapuserdSocketProxy;
    }
    borrowed_fd server_fd(android_get_control_socket(kSnapuserdSocket));
    if (server_fd < 0) {
        PLOG(FATAL) << "Proxy could not get android control socket " << kSnapuserdSocket;
    }

    if (listen(proxy_fd.get(), 4) < 0) {
        PLOG(FATAL) << "Proxy listen socket failed";
    }

    if (!android::base::SetProperty("snapuserd.proxy_ready", "true")) {
        LOG(FATAL) << "Proxy failed to set ready property";
    }

    unique_fd client_fd(
            TEMP_FAILURE_RETRY(accept4(proxy_fd.get(), nullptr, nullptr, SOCK_CLOEXEC)));
    if (client_fd < 0) {
        PLOG(FATAL) << "Proxy accept failed";
    }

    char code[1] = {'a'};
    std::vector<int> fds = {server_fd.get()};
    ssize_t rv = android::base::SendFileDescriptorVector(client_fd, code, sizeof(code), fds);
    if (rv < 0) {
        PLOG(FATAL) << "Proxy could not send file descriptor to snapuserd";
    }
    // Wait for an ACK - results don't matter, we just don't want to risk closing
    // the proxy socket too early.
    if (recv(client_fd, code, sizeof(code), 0) < 0) {
        PLOG(FATAL) << "Proxy could not receive terminating code from snapuserd";
    }
    return true;
}

bool UserSnapshotServer::UpdateVerification(std::lock_guard<std::mutex>* proof_of_lock) {
    CHECK(proof_of_lock);

    bool status = true;
    for (auto iter = dm_users_.begin(); iter != dm_users_.end(); iter++) {
        auto& th = (*iter)->thread();
        if (th.joinable() && status) {
            status = (*iter)->snapuserd()->CheckPartitionVerification() && status;
        } else {
            // return immediately if there is a failure
            return false;
        }
    }

    return status;
}

}  // namespace snapshot
}  // namespace android