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client.go
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client.go
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//go:build linux
// +build linux
package nbd
import (
"os"
"syscall"
"github.com/pkg/errors"
"github.com/sirupsen/logrus"
)
const (
IO = 0xab << 8
NBD_SET_SOCK = IO
NBD_SET_BLKSIZE = IO | 1
NBD_SET_SIZE = IO | 2
NBD_DO_IT = IO | 3
NBD_CLEAR_SOCK = IO | 4
NBD_CLEAR_QUE = IO | 5
NBD_PRINT_DEBUG = IO | 6
NBD_SET_SIZE_BLOCKS = IO | 7
NBD_DISCONNECT = IO | 8
NBD_SET_TIMEOUT = IO | 9
NBD_SET_FLAGS = IO | 10
)
const (
NBD_FLAG_HAS_FLAGS = (1 << 0)
NBD_FLAG_READ_ONLY = (1 << 1)
NBD_FLAG_SEND_FLUSH = (1 << 2)
NBD_FLAG_SEND_TRIM = (1 << 5)
)
type Client struct {
devpath string
devsize int64
blocksize int
sockFd int
sendFlush, sendTrim bool
readOnly bool
dev *os.File
log *logrus.Logger
}
func ioctl(fd, op, arg uintptr) error {
_, _, err := syscall.Syscall(syscall.SYS_IOCTL, fd, op, arg)
if err != 0 {
return errors.Wrapf(err, "ioctl(%d, %d, %d) failed", fd, op, arg)
}
return nil
}
func NewClient(devpath string, sockFd int, devsize int64) *Client {
return &Client{
devpath: devpath,
sockFd: sockFd,
devsize: devsize,
}
}
func (c *Client) SetSendFlush(v bool) {
c.sendFlush = v
}
func (c *Client) SetSendTrim(v bool) {
c.sendTrim = v
}
func (c *Client) SetBlockSize(size int) {
c.blocksize = size
}
func (c *Client) SetReadOnly(flag bool) {
c.readOnly = flag
}
func (c *Client) SetLogger(log *logrus.Logger) {
c.log = log
}
func (c *Client) Run() (err error) {
c.dev, err = os.OpenFile(c.devpath, os.O_RDWR, 0600)
if err != nil {
return
}
devFd := c.dev.Fd()
if err = ioctl(devFd, NBD_SET_SIZE, uintptr(c.devsize)); err != nil {
return
}
if err = ioctl(devFd, NBD_CLEAR_QUE, 0); err != nil {
return
}
if err = ioctl(devFd, NBD_CLEAR_SOCK, 0); err != nil {
return
}
if c.blocksize > 0 {
if err = ioctl(devFd, NBD_SET_BLKSIZE, uintptr(c.blocksize)); err != nil {
return
}
}
var flags uintptr
if c.sendFlush {
flags |= NBD_FLAG_SEND_FLUSH
}
if c.sendTrim {
flags |= NBD_FLAG_SEND_TRIM
}
if c.readOnly {
flags |= NBD_FLAG_READ_ONLY
}
if err1 := ioctl(devFd, NBD_SET_FLAGS, flags); err1 != nil {
// ignore errors as some features may not be supported
if c.log != nil {
c.log.Warnf("Could not set flags: %v", err1)
}
}
if err = ioctl(devFd, NBD_SET_SOCK, uintptr(c.sockFd)); err != nil {
return
}
go func() {
//opens the device file at least once, to make sure the partition table is updated
tmp, err := os.Open(c.devpath)
if err != nil {
if c.log != nil {
c.log.Errorf("Cannot open the device %s: %s", c.devpath, err)
}
}
tmp.Close()
}()
// The following call will block until the client disconnects
err = ioctl(devFd, NBD_DO_IT, 0)
if c.log != nil {
c.log.Debug("Finished NBD client")
}
ioctl(devFd, NBD_CLEAR_SOCK, 0)
c.dev.Close()
syscall.Close(int(c.sockFd))
return err
}
func (c *Client) Close() error {
return ioctl(c.dev.Fd(), NBD_DISCONNECT, 0)
}