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/
nbdserver.go
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/
nbdserver.go
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package nbd
import (
"encoding/binary"
"fmt"
"io"
"net"
"sync"
"time"
"github.com/coreos/pkg/capnslog"
)
var clog = capnslog.NewPackageLogger("github.com/coreos/torus", "nbd")
const (
nbdMagic uint64 = 0x4e42444d41474943
nbdOpts uint64 = 0x49484156454F5054
nbdFlagFixedNewStyle = 0x1
// options
nbdOptExportName = 0x1
nbdOptAbort = 0x2
nbdOptList = 0x3
// option replies
nbdRepAck = 0x1
nbdRepServer = 0x2
nbdRepErrUnsup = 0x80000001
tcpKeepAlive = 10 * time.Second
)
type DeviceFinder interface {
FindDevice(name string) (Device, error)
ListDevices() ([]string, error)
}
type NBDServer struct {
l *net.TCPListener
finder DeviceFinder
}
func NewNBDServer(addr string, finder DeviceFinder) (*NBDServer, error) {
tcpaddr, err := net.ResolveTCPAddr("tcp", addr)
if err != nil {
return nil, err
}
ln, err := net.ListenTCP("tcp", tcpaddr)
if err != nil {
return nil, err
}
ns := &NBDServer{
l: ln,
finder: finder,
}
return ns, nil
}
func (s *NBDServer) Serve() error {
for {
c, err := s.l.AcceptTCP()
if err != nil {
return err
}
c.SetKeepAlive(true)
c.SetKeepAlivePeriod(tcpKeepAlive)
conn := &NBDConn{
c: c,
finder: s.finder,
export: "<none>",
}
go func() {
if err := conn.handler(); err != nil {
conn.errorf("handler error: %v", err)
}
conn.Close()
}()
}
}
func (s *NBDServer) Close() error {
return s.l.Close()
}
type option struct {
opt uint32
data []byte
}
type NBDConn struct {
c net.Conn
finder DeviceFinder
device Device
export string
}
func (c *NBDConn) errorf(format string, stuff ...interface{}) {
s := fmt.Sprintf(format, stuff...)
clog.Errorf("%s: %s: %s", c.c.RemoteAddr(), c.export, s)
}
func (c *NBDConn) tracef(format string, stuff ...interface{}) {
s := fmt.Sprintf(format, stuff...)
clog.Tracef("%s: %s: %s", c.c.RemoteAddr(), c.export, s)
}
func (c *NBDConn) handler() error {
var clientFlags uint32
c.tracef("handshaking")
// initial handshake
if err := binary.Write(c.c, binary.BigEndian, nbdMagic); err != nil {
return err
}
if err := binary.Write(c.c, binary.BigEndian, nbdOpts); err != nil {
return err
}
if err := binary.Write(c.c, binary.BigEndian, uint16(nbdFlagFixedNewStyle)); err != nil {
return err
}
// these are read but ignore since none are used.
if err := binary.Read(c.c, binary.BigEndian, &clientFlags); err != nil {
return err
}
c.tracef("reading options")
// get options
if err := c.options(); err != nil {
return fmt.Errorf("handshake failure: %v", err)
}
// send transmission flags
if err := binary.Write(c.c, binary.BigEndian, c.device.Size()); err != nil {
return err
}
if err := binary.Write(c.c, binary.BigEndian, uint16(flagHasFlags|flagSendFlush|flagSendTrim)); err != nil {
return err
}
// reserved zero pad
zpad := make([]byte, 124)
if err := writeFull(c.c, zpad); err != nil {
return err
}
c.tracef("serving")
srv := &serverConn{
rw: c.c,
}
// TODO: don't throw away serveLoop errors.
// also see nbd.go's Serve
n := 1
wg := new(sync.WaitGroup)
wg.Add(n)
for i := 0; i < n; i++ {
go srv.serveLoop(c.device, wg)
}
wg.Wait()
return nil
}
// do nbd option exchange and return once export name is given.
func (c *NBDConn) options() error {
for {
opt, err := c.getOpt()
if err != nil {
return err
}
switch opt.opt {
case nbdOptExportName:
if len(opt.data) == 0 {
return fmt.Errorf("nbdserve doesn't support empty volume name. client needs to specify it")
}
dev, err := c.finder.FindDevice(string(opt.data))
if err != nil {
// terminate the connection on failure
return err
}
c.device = dev
c.export = string(opt.data)
// got dev, done with options.
return nil
case nbdOptAbort:
if err := c.optReply(nbdOptList, nbdRepAck, nil); err != nil {
return err
}
return nil
case nbdOptList:
devs, err := c.finder.ListDevices()
if err != nil {
return err
}
for _, d := range devs {
// a bit silly. prefix string with length..
buf := make([]byte, 4+len(d))
binary.BigEndian.PutUint32(buf[0:4], uint32(len(d)))
copy(buf[4:], []byte(d))
if err := c.optReply(nbdOptList, nbdRepServer, buf); err != nil {
return err
}
}
if err := c.optReply(nbdOptList, nbdRepAck, nil); err != nil {
return err
}
default:
if err := c.optReply(opt.opt, nbdRepErrUnsup, nil); err != nil {
return err
}
}
}
}
func writeFull(w io.Writer, buf []byte) error {
n, err := w.Write(buf)
if err != nil {
return err
}
if n != len(buf) {
return io.ErrShortWrite
}
return nil
}
func (c *NBDConn) optReply(opt uint32, reptype uint32, data []byte) error {
rep := make([]byte, 8+4+4+4)
// option reply magic
binary.BigEndian.PutUint64(rep[0:8], uint64(0x3e889045565a9))
binary.BigEndian.PutUint32(rep[8:12], opt)
binary.BigEndian.PutUint32(rep[12:16], reptype)
binary.BigEndian.PutUint32(rep[16:20], uint32(len(data)))
rep = append(rep, data...)
return writeFull(c.c, rep)
}
func (c *NBDConn) getOpt() (*option, error) {
var (
optMagic uint64
opt uint32
optLen uint32
)
if err := binary.Read(c.c, binary.BigEndian, &optMagic); err != nil {
return nil, err
}
if optMagic != nbdOpts {
return nil, fmt.Errorf("bad option magic %x", optMagic)
}
if err := binary.Read(c.c, binary.BigEndian, &opt); err != nil {
return nil, err
}
if err := binary.Read(c.c, binary.BigEndian, &optLen); err != nil {
return nil, err
}
if optLen > 4096 {
return nil, fmt.Errorf("strange option length: %d", optLen)
}
switch opt {
case nbdOptExportName:
o := &option{
opt: opt,
data: make([]byte, optLen),
}
if optLen > 0 {
if _, err := io.ReadFull(c.c, o.data); err != nil {
return nil, err
}
}
return o, nil
case nbdOptAbort, nbdOptList:
return &option{opt: opt}, nil
default:
return nil, fmt.Errorf("unknown option %032b", opt)
}
}
func (c *NBDConn) Close() error {
if c.device != nil {
c.device.Close()
}
return c.c.Close()
}