media/mtp/MtpFfsCompatHandle.cpp

/*
 * Copyright (C) 2017 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 <android-base/logging.h>
#include <android-base/properties.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <linux/usb/ch9.h>
#include <linux/usb/functionfs.h>
#include <mutex>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/endian.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#include "PosixAsyncIO.h"
#include "MtpFfsCompatHandle.h"
#include "mtp.h"

#define FUNCTIONFS_ENDPOINT_ALLOC       _IOR('g', 231, __u32)

namespace {

// Must be divisible by all max packet size values
constexpr int MAX_FILE_CHUNK_SIZE = 3145728;

// Safe values since some devices cannot handle large DMAs
// To get good performance, override these with
// higher values per device using the properties
// sys.usb.ffs.max_read and sys.usb.ffs.max_write
constexpr int USB_FFS_MAX_WRITE = MTP_BUFFER_SIZE;
constexpr int USB_FFS_MAX_READ = MTP_BUFFER_SIZE;

static_assert(USB_FFS_MAX_WRITE > 0, "Max r/w values must be > 0!");
static_assert(USB_FFS_MAX_READ > 0, "Max r/w values must be > 0!");

constexpr unsigned int MAX_MTP_FILE_SIZE = 0xFFFFFFFF;

constexpr size_t ENDPOINT_ALLOC_RETRIES = 10;

} // anonymous namespace

namespace android {

MtpFfsCompatHandle::MtpFfsCompatHandle() :
    mMaxWrite(USB_FFS_MAX_WRITE),
    mMaxRead(USB_FFS_MAX_READ) {}

MtpFfsCompatHandle::~MtpFfsCompatHandle() {}

int MtpFfsCompatHandle::writeHandle(int fd, const void* data, size_t len) {
    int ret = 0;
    const char* buf = static_cast<const char*>(data);
    while (len > 0) {
        int write_len = std::min(mMaxWrite, len);
        int n = TEMP_FAILURE_RETRY(::write(fd, buf, write_len));

        if (n < 0) {
            PLOG(ERROR) << "write ERROR: fd = " << fd << ", n = " << n;
            return -1;
        } else if (n < write_len) {
            errno = EIO;
            PLOG(ERROR) << "less written than expected";
            return -1;
        }
        buf += n;
        len -= n;
        ret += n;
    }
    return ret;
}

int MtpFfsCompatHandle::readHandle(int fd, void* data, size_t len) {
    int ret = 0;
    char* buf = static_cast<char*>(data);
    while (len > 0) {
        int read_len = std::min(mMaxRead, len);
        int n = TEMP_FAILURE_RETRY(::read(fd, buf, read_len));
        if (n < 0) {
            PLOG(ERROR) << "read ERROR: fd = " << fd << ", n = " << n;
            return -1;
        }
        ret += n;
        if (n < read_len) // done reading early
            break;
        buf += n;
        len -= n;
    }
    return ret;
}

int MtpFfsCompatHandle::start() {
    mLock.lock();

    if (!openEndpoints())
        return -1;

    for (unsigned i = 0; i < NUM_IO_BUFS; i++) {
        mIobuf[i].bufs.resize(MAX_FILE_CHUNK_SIZE);
        posix_madvise(mIobuf[i].bufs.data(), MAX_FILE_CHUNK_SIZE,
                POSIX_MADV_SEQUENTIAL | POSIX_MADV_WILLNEED);
    }

    // Get device specific r/w size
    mMaxWrite = android::base::GetIntProperty("sys.usb.ffs.max_write", USB_FFS_MAX_WRITE);
    mMaxRead = android::base::GetIntProperty("sys.usb.ffs.max_read", USB_FFS_MAX_READ);

    size_t attempts = 0;
    while (mMaxWrite >= USB_FFS_MAX_WRITE && mMaxRead >= USB_FFS_MAX_READ &&
            attempts < ENDPOINT_ALLOC_RETRIES) {
        // If larger contiguous chunks of memory aren't available, attempt to try
        // smaller allocations.
        if (ioctl(mBulkIn, FUNCTIONFS_ENDPOINT_ALLOC, static_cast<__u32>(mMaxWrite)) ||
            ioctl(mBulkOut, FUNCTIONFS_ENDPOINT_ALLOC, static_cast<__u32>(mMaxRead))) {
            if (errno == ENODEV) {
                // Driver hasn't enabled endpoints yet.
                std::this_thread::sleep_for(std::chrono::milliseconds(100));
                attempts += 1;
                continue;
            }
            mMaxWrite /= 2;
            mMaxRead /=2;
        } else {
            return 0;
        }
    }
    // Try to start MtpServer anyway, with the smallest max r/w values
    mMaxWrite = USB_FFS_MAX_WRITE;
    mMaxRead = USB_FFS_MAX_READ;
    PLOG(ERROR) << "Functionfs could not allocate any memory!";
    return 0;
}

int MtpFfsCompatHandle::read(void* data, size_t len) {
    return readHandle(mBulkOut, data, len);
}

int MtpFfsCompatHandle::write(const void* data, size_t len) {
    return writeHandle(mBulkIn, data, len);
}

int MtpFfsCompatHandle::receiveFile(mtp_file_range mfr, bool zero_packet) {
    // When receiving files, the incoming length is given in 32 bits.
    // A >4G file is given as 0xFFFFFFFF
    uint32_t file_length = mfr.length;
    uint64_t offset = mfr.offset;
    int packet_size = getPacketSize(mBulkOut);

    unsigned char *data = mIobuf[0].bufs.data();
    unsigned char *data2 = mIobuf[1].bufs.data();

    struct aiocb aio;
    aio.aio_fildes = mfr.fd;
    aio.aio_buf = nullptr;
    struct aiocb *aiol[] = {&aio};
    int ret = -1;
    size_t length;
    bool read = false;
    bool write = false;

    posix_fadvise(mfr.fd, 0, 0, POSIX_FADV_SEQUENTIAL | POSIX_FADV_NOREUSE);

    // Break down the file into pieces that fit in buffers
    while (file_length > 0 || write) {
        if (file_length > 0) {
            length = std::min(static_cast<uint32_t>(MAX_FILE_CHUNK_SIZE), file_length);

            // Read data from USB, handle errors after waiting for write thread.
            ret = readHandle(mBulkOut, data, length);

            if (file_length != MAX_MTP_FILE_SIZE && ret < static_cast<int>(length)) {
                ret = -1;
                errno = EIO;
            }
            read = true;
        }

        if (write) {
            // get the return status of the last write request
            aio_suspend(aiol, 1, nullptr);

            int written = aio_return(&aio);
            if (written == -1) {
                errno = aio_error(&aio);
                return -1;
            }
            if (static_cast<size_t>(written) < aio.aio_nbytes) {
                errno = EIO;
                return -1;
            }
            write = false;
        }

        // If there was an error reading above
        if (ret == -1) {
            return -1;
        }

        if (read) {
            if (file_length == MAX_MTP_FILE_SIZE) {
                // For larger files, receive until a short packet is received.
                if (static_cast<size_t>(ret) < length) {
                    file_length = 0;
                }
            } else {
                file_length -= ret;
            }
            // Enqueue a new write request
            aio_prepare(&aio, data, length, offset);
            aio_write(&aio);

            offset += ret;
            std::swap(data, data2);

            write = true;
            read = false;
        }
    }
    // Receive an empty packet if size is a multiple of the endpoint size.
    if (ret % packet_size == 0 || zero_packet) {
        if (TEMP_FAILURE_RETRY(::read(mBulkOut, data, packet_size)) != 0) {
            return -1;
        }
    }
    return 0;
}

int MtpFfsCompatHandle::sendFile(mtp_file_range mfr) {
    uint64_t file_length = mfr.length;
    uint32_t given_length = std::min(static_cast<uint64_t>(MAX_MTP_FILE_SIZE),
            file_length + sizeof(mtp_data_header));
    uint64_t offset = mfr.offset;
    int packet_size = getPacketSize(mBulkIn);

    // If file_length is larger than a size_t, truncating would produce the wrong comparison.
    // Instead, promote the left side to 64 bits, then truncate the small result.
    int init_read_len = std::min(
            static_cast<uint64_t>(packet_size - sizeof(mtp_data_header)), file_length);

    unsigned char *data = mIobuf[0].bufs.data();
    unsigned char *data2 = mIobuf[1].bufs.data();

    posix_fadvise(mfr.fd, 0, 0, POSIX_FADV_SEQUENTIAL | POSIX_FADV_NOREUSE);

    struct aiocb aio;
    aio.aio_fildes = mfr.fd;
    struct aiocb *aiol[] = {&aio};
    int ret, length;
    int error = 0;
    bool read = false;
    bool write = false;

    // Send the header data
    mtp_data_header *header = reinterpret_cast<mtp_data_header*>(data);
    header->length = htole32(given_length);
    header->type = htole16(2); /* data packet */
    header->command = htole16(mfr.command);
    header->transaction_id = htole32(mfr.transaction_id);

    // Some hosts don't support header/data separation even though MTP allows it
    // Handle by filling first packet with initial file data
    if (TEMP_FAILURE_RETRY(pread(mfr.fd, reinterpret_cast<char*>(data) +
                    sizeof(mtp_data_header), init_read_len, offset))
            != init_read_len) return -1;
    if (writeHandle(mBulkIn, data, sizeof(mtp_data_header) + init_read_len) == -1) return -1;
    file_length -= init_read_len;
    offset += init_read_len;
    ret = init_read_len + sizeof(mtp_data_header);

    // Break down the file into pieces that fit in buffers
    while (file_length > 0) {
        if (read) {
            // Wait for the previous read to finish
            aio_suspend(aiol, 1, nullptr);
            ret = aio_return(&aio);
            if (ret == -1) {
                errno = aio_error(&aio);
                return -1;
            }
            if (static_cast<size_t>(ret) < aio.aio_nbytes) {
                errno = EIO;
                return -1;
            }

            file_length -= ret;
            offset += ret;
            std::swap(data, data2);
            read = false;
            write = true;
        }

        if (error == -1) {
            return -1;
        }

        if (file_length > 0) {
            length = std::min(static_cast<uint64_t>(MAX_FILE_CHUNK_SIZE), file_length);
            // Queue up another read
            aio_prepare(&aio, data, length, offset);
            aio_read(&aio);
            read = true;
        }

        if (write) {
            if (writeHandle(mBulkIn, data2, ret) == -1) {
                error = -1;
            }
            write = false;
        }
    }

    if (ret % packet_size == 0) {
        // If the last packet wasn't short, send a final empty packet
        if (TEMP_FAILURE_RETRY(::write(mBulkIn, data, 0)) != 0) {
            return -1;
        }
    }

    return 0;
}

} // namespace android