syncthing/lib/protocol/protocol.go
2015-09-22 20:34:24 +02:00

785 lines
18 KiB
Go

// Copyright (C) 2014 The Protocol Authors.
package protocol
import (
"encoding/binary"
"encoding/hex"
"errors"
"fmt"
"io"
"sync"
"time"
lz4 "github.com/bkaradzic/go-lz4"
)
const (
// BlockSize is the standard ata block size (128 KiB)
BlockSize = 128 << 10
// MaxMessageLen is the largest message size allowed on the wire. (64 MiB)
MaxMessageLen = 64 << 20
)
const (
messageTypeClusterConfig = 0
messageTypeIndex = 1
messageTypeRequest = 2
messageTypeResponse = 3
messageTypePing = 4
messageTypeIndexUpdate = 6
messageTypeClose = 7
)
const (
stateInitial = iota
stateReady
)
// FileInfo flags
const (
FlagDeleted uint32 = 1 << 12
FlagInvalid = 1 << 13
FlagDirectory = 1 << 14
FlagNoPermBits = 1 << 15
FlagSymlink = 1 << 16
FlagSymlinkMissingTarget = 1 << 17
FlagsAll = (1 << 18) - 1
SymlinkTypeMask = FlagDirectory | FlagSymlinkMissingTarget
)
// IndexMessage message flags (for IndexUpdate)
const (
FlagIndexTemporary uint32 = 1 << iota
)
// Request message flags
const (
FlagRequestTemporary uint32 = 1 << iota
)
// ClusterConfigMessage.Folders.Devices flags
const (
FlagShareTrusted uint32 = 1 << 0
FlagShareReadOnly = 1 << 1
FlagIntroducer = 1 << 2
FlagShareBits = 0x000000ff
)
var (
ErrClosed = errors.New("connection closed")
ErrTimeout = errors.New("read timeout")
)
// Specific variants of empty messages...
type pingMessage struct{ EmptyMessage }
type Model interface {
// An index was received from the peer device
Index(deviceID DeviceID, folder string, files []FileInfo, flags uint32, options []Option)
// An index update was received from the peer device
IndexUpdate(deviceID DeviceID, folder string, files []FileInfo, flags uint32, options []Option)
// A request was made by the peer device
Request(deviceID DeviceID, folder string, name string, offset int64, hash []byte, flags uint32, options []Option, buf []byte) error
// A cluster configuration message was received
ClusterConfig(deviceID DeviceID, config ClusterConfigMessage)
// The peer device closed the connection
Close(deviceID DeviceID, err error)
}
type Connection interface {
Start()
ID() DeviceID
Name() string
Index(folder string, files []FileInfo, flags uint32, options []Option) error
IndexUpdate(folder string, files []FileInfo, flags uint32, options []Option) error
Request(folder string, name string, offset int64, size int, hash []byte, flags uint32, options []Option) ([]byte, error)
ClusterConfig(config ClusterConfigMessage)
Statistics() Statistics
}
type rawConnection struct {
id DeviceID
name string
receiver Model
cr *countingReader
cw *countingWriter
awaiting [4096]chan asyncResult
awaitingMut sync.Mutex
idxMut sync.Mutex // ensures serialization of Index calls
nextID chan int
outbox chan hdrMsg
closed chan struct{}
once sync.Once
pool sync.Pool
compression Compression
rdbuf0 []byte // used & reused by readMessage
rdbuf1 []byte // used & reused by readMessage
}
type asyncResult struct {
val []byte
err error
}
type hdrMsg struct {
hdr header
msg encodable
done chan struct{}
}
type encodable interface {
AppendXDR([]byte) ([]byte, error)
}
type isEofer interface {
IsEOF() bool
}
const (
// PingSendInterval is how often we make sure to send a message, by
// triggering pings if necessary.
PingSendInterval = 90 * time.Second
// ReceiveTimeout is the longest we'll wait for a message from the other
// side before closing the connection.
ReceiveTimeout = 300 * time.Second
)
func NewConnection(deviceID DeviceID, reader io.Reader, writer io.Writer, receiver Model, name string, compress Compression) Connection {
cr := &countingReader{Reader: reader}
cw := &countingWriter{Writer: writer}
c := rawConnection{
id: deviceID,
name: name,
receiver: nativeModel{receiver},
cr: cr,
cw: cw,
outbox: make(chan hdrMsg),
nextID: make(chan int),
closed: make(chan struct{}),
pool: sync.Pool{
New: func() interface{} {
return make([]byte, BlockSize)
},
},
compression: compress,
}
return wireFormatConnection{&c}
}
// Start creates the goroutines for sending and receiving of messages. It must
// be called exactly once after creating a connection.
func (c *rawConnection) Start() {
go c.readerLoop()
go c.writerLoop()
go c.pingSender()
go c.pingReceiver()
go c.idGenerator()
}
func (c *rawConnection) ID() DeviceID {
return c.id
}
func (c *rawConnection) Name() string {
return c.name
}
// Index writes the list of file information to the connected peer device
func (c *rawConnection) Index(folder string, idx []FileInfo, flags uint32, options []Option) error {
select {
case <-c.closed:
return ErrClosed
default:
}
c.idxMut.Lock()
c.send(-1, messageTypeIndex, IndexMessage{
Folder: folder,
Files: idx,
Flags: flags,
Options: options,
}, nil)
c.idxMut.Unlock()
return nil
}
// IndexUpdate writes the list of file information to the connected peer device as an update
func (c *rawConnection) IndexUpdate(folder string, idx []FileInfo, flags uint32, options []Option) error {
select {
case <-c.closed:
return ErrClosed
default:
}
c.idxMut.Lock()
c.send(-1, messageTypeIndexUpdate, IndexMessage{
Folder: folder,
Files: idx,
Flags: flags,
Options: options,
}, nil)
c.idxMut.Unlock()
return nil
}
// Request returns the bytes for the specified block after fetching them from the connected peer.
func (c *rawConnection) Request(folder string, name string, offset int64, size int, hash []byte, flags uint32, options []Option) ([]byte, error) {
var id int
select {
case id = <-c.nextID:
case <-c.closed:
return nil, ErrClosed
}
c.awaitingMut.Lock()
if ch := c.awaiting[id]; ch != nil {
panic("id taken")
}
rc := make(chan asyncResult, 1)
c.awaiting[id] = rc
c.awaitingMut.Unlock()
ok := c.send(id, messageTypeRequest, RequestMessage{
Folder: folder,
Name: name,
Offset: offset,
Size: int32(size),
Hash: hash,
Flags: flags,
Options: options,
}, nil)
if !ok {
return nil, ErrClosed
}
res, ok := <-rc
if !ok {
return nil, ErrClosed
}
return res.val, res.err
}
// ClusterConfig send the cluster configuration message to the peer and returns any error
func (c *rawConnection) ClusterConfig(config ClusterConfigMessage) {
c.send(-1, messageTypeClusterConfig, config, nil)
}
func (c *rawConnection) ping() bool {
var id int
select {
case id = <-c.nextID:
case <-c.closed:
return false
}
return c.send(id, messageTypePing, nil, nil)
}
func (c *rawConnection) readerLoop() (err error) {
defer func() {
c.close(err)
}()
state := stateInitial
for {
select {
case <-c.closed:
return ErrClosed
default:
}
hdr, msg, err := c.readMessage()
if err != nil {
return err
}
switch msg := msg.(type) {
case ClusterConfigMessage:
if state != stateInitial {
return fmt.Errorf("protocol error: cluster config message in state %d", state)
}
go c.receiver.ClusterConfig(c.id, msg)
state = stateReady
case IndexMessage:
switch hdr.msgType {
case messageTypeIndex:
if state != stateReady {
return fmt.Errorf("protocol error: index message in state %d", state)
}
c.handleIndex(msg)
state = stateReady
case messageTypeIndexUpdate:
if state != stateReady {
return fmt.Errorf("protocol error: index update message in state %d", state)
}
c.handleIndexUpdate(msg)
state = stateReady
}
case RequestMessage:
if state != stateReady {
return fmt.Errorf("protocol error: request message in state %d", state)
}
// Requests are handled asynchronously
go c.handleRequest(hdr.msgID, msg)
case ResponseMessage:
if state != stateReady {
return fmt.Errorf("protocol error: response message in state %d", state)
}
c.handleResponse(hdr.msgID, msg)
case pingMessage:
if state != stateReady {
return fmt.Errorf("protocol error: ping message in state %d", state)
}
// Nothing
case CloseMessage:
return errors.New(msg.Reason)
default:
return fmt.Errorf("protocol error: %s: unknown message type %#x", c.id, hdr.msgType)
}
}
}
func (c *rawConnection) readMessage() (hdr header, msg encodable, err error) {
if cap(c.rdbuf0) < 8 {
c.rdbuf0 = make([]byte, 8)
} else {
c.rdbuf0 = c.rdbuf0[:8]
}
_, err = io.ReadFull(c.cr, c.rdbuf0)
if err != nil {
return
}
hdr = decodeHeader(binary.BigEndian.Uint32(c.rdbuf0[0:4]))
msglen := int(binary.BigEndian.Uint32(c.rdbuf0[4:8]))
if debug {
l.Debugf("read header %v (msglen=%d)", hdr, msglen)
}
if msglen > MaxMessageLen {
err = fmt.Errorf("message length %d exceeds maximum %d", msglen, MaxMessageLen)
return
}
if hdr.version != 0 {
err = fmt.Errorf("unknown protocol version 0x%x", hdr.version)
return
}
if cap(c.rdbuf0) < msglen {
c.rdbuf0 = make([]byte, msglen)
} else {
c.rdbuf0 = c.rdbuf0[:msglen]
}
_, err = io.ReadFull(c.cr, c.rdbuf0)
if err != nil {
return
}
if debug {
l.Debugf("read %d bytes", len(c.rdbuf0))
}
msgBuf := c.rdbuf0
if hdr.compression && msglen > 0 {
c.rdbuf1 = c.rdbuf1[:cap(c.rdbuf1)]
c.rdbuf1, err = lz4.Decode(c.rdbuf1, c.rdbuf0)
if err != nil {
return
}
msgBuf = c.rdbuf1
if debug {
l.Debugf("decompressed to %d bytes", len(msgBuf))
}
}
if debug {
if len(msgBuf) > 1024 {
l.Debugf("message data:\n%s", hex.Dump(msgBuf[:1024]))
} else {
l.Debugf("message data:\n%s", hex.Dump(msgBuf))
}
}
// We check each returned error for the XDRError.IsEOF() method.
// IsEOF()==true here means that the message contained fewer fields than
// expected. It does not signify an EOF on the socket, because we've
// successfully read a size value and that many bytes already. New fields
// we expected but the other peer didn't send should be interpreted as
// zero/nil, and if that's not valid we'll verify it somewhere else.
switch hdr.msgType {
case messageTypeIndex, messageTypeIndexUpdate:
var idx IndexMessage
err = idx.UnmarshalXDR(msgBuf)
if xdrErr, ok := err.(isEofer); ok && xdrErr.IsEOF() {
err = nil
}
msg = idx
case messageTypeRequest:
var req RequestMessage
err = req.UnmarshalXDR(msgBuf)
if xdrErr, ok := err.(isEofer); ok && xdrErr.IsEOF() {
err = nil
}
msg = req
case messageTypeResponse:
var resp ResponseMessage
err = resp.UnmarshalXDR(msgBuf)
if xdrErr, ok := err.(isEofer); ok && xdrErr.IsEOF() {
err = nil
}
msg = resp
case messageTypePing:
msg = pingMessage{}
case messageTypeClusterConfig:
var cc ClusterConfigMessage
err = cc.UnmarshalXDR(msgBuf)
if xdrErr, ok := err.(isEofer); ok && xdrErr.IsEOF() {
err = nil
}
msg = cc
case messageTypeClose:
var cm CloseMessage
err = cm.UnmarshalXDR(msgBuf)
if xdrErr, ok := err.(isEofer); ok && xdrErr.IsEOF() {
err = nil
}
msg = cm
default:
err = fmt.Errorf("protocol error: %s: unknown message type %#x", c.id, hdr.msgType)
}
return
}
func (c *rawConnection) handleIndex(im IndexMessage) {
if debug {
l.Debugf("Index(%v, %v, %d file, flags %x, opts: %s)", c.id, im.Folder, len(im.Files), im.Flags, im.Options)
}
c.receiver.Index(c.id, im.Folder, filterIndexMessageFiles(im.Files), im.Flags, im.Options)
}
func (c *rawConnection) handleIndexUpdate(im IndexMessage) {
if debug {
l.Debugf("queueing IndexUpdate(%v, %v, %d files, flags %x, opts: %s)", c.id, im.Folder, len(im.Files), im.Flags, im.Options)
}
c.receiver.IndexUpdate(c.id, im.Folder, filterIndexMessageFiles(im.Files), im.Flags, im.Options)
}
func filterIndexMessageFiles(fs []FileInfo) []FileInfo {
var out []FileInfo
for i, f := range fs {
switch f.Name {
case "", ".", "..", "/": // A few obviously invalid filenames
l.Infof("Dropping invalid filename %q from incoming index", f.Name)
if out == nil {
// Most incoming updates won't contain anything invalid, so we
// delay the allocation and copy to output slice until we
// really need to do it, then copy all the so var valid files
// to it.
out = make([]FileInfo, i, len(fs)-1)
copy(out, fs)
}
default:
if out != nil {
out = append(out, f)
}
}
}
if out != nil {
return out
}
return fs
}
func (c *rawConnection) handleRequest(msgID int, req RequestMessage) {
size := int(req.Size)
usePool := size <= BlockSize
var buf []byte
var done chan struct{}
if usePool {
buf = c.pool.Get().([]byte)[:size]
done = make(chan struct{})
} else {
buf = make([]byte, size)
}
err := c.receiver.Request(c.id, req.Folder, req.Name, int64(req.Offset), req.Hash, req.Flags, req.Options, buf)
if err != nil {
c.send(msgID, messageTypeResponse, ResponseMessage{
Data: nil,
Code: errorToCode(err),
}, done)
} else {
c.send(msgID, messageTypeResponse, ResponseMessage{
Data: buf,
Code: errorToCode(err),
}, done)
}
if usePool {
<-done
c.pool.Put(buf)
}
}
func (c *rawConnection) handleResponse(msgID int, resp ResponseMessage) {
c.awaitingMut.Lock()
if rc := c.awaiting[msgID]; rc != nil {
c.awaiting[msgID] = nil
rc <- asyncResult{resp.Data, codeToError(resp.Code)}
close(rc)
}
c.awaitingMut.Unlock()
}
func (c *rawConnection) handlePong(msgID int) {
c.awaitingMut.Lock()
if rc := c.awaiting[msgID]; rc != nil {
c.awaiting[msgID] = nil
rc <- asyncResult{}
close(rc)
}
c.awaitingMut.Unlock()
}
func (c *rawConnection) send(msgID int, msgType int, msg encodable, done chan struct{}) bool {
if msgID < 0 {
select {
case id := <-c.nextID:
msgID = id
case <-c.closed:
return false
}
}
hdr := header{
version: 0,
msgID: msgID,
msgType: msgType,
}
select {
case c.outbox <- hdrMsg{hdr, msg, done}:
return true
case <-c.closed:
return false
}
}
func (c *rawConnection) writerLoop() {
var msgBuf = make([]byte, 8) // buffer for wire format message, kept and reused
var uncBuf []byte // buffer for uncompressed message, kept and reused
for {
var tempBuf []byte
var err error
select {
case hm := <-c.outbox:
if hm.msg != nil {
// Uncompressed message in uncBuf
uncBuf, err = hm.msg.AppendXDR(uncBuf[:0])
if hm.done != nil {
close(hm.done)
}
if err != nil {
c.close(err)
return
}
compress := false
switch c.compression {
case CompressAlways:
compress = true
case CompressMetadata:
compress = hm.hdr.msgType != messageTypeResponse
}
if compress && len(uncBuf) >= compressionThreshold {
// Use compression for large messages
hm.hdr.compression = true
// Make sure we have enough space for the compressed message plus header in msgBug
msgBuf = msgBuf[:cap(msgBuf)]
if maxLen := lz4.CompressBound(len(uncBuf)) + 8; maxLen > len(msgBuf) {
msgBuf = make([]byte, maxLen)
}
// Compressed is written to msgBuf, we keep tb for the length only
tempBuf, err = lz4.Encode(msgBuf[8:], uncBuf)
binary.BigEndian.PutUint32(msgBuf[4:8], uint32(len(tempBuf)))
msgBuf = msgBuf[0 : len(tempBuf)+8]
if debug {
l.Debugf("write compressed message; %v (len=%d)", hm.hdr, len(tempBuf))
}
} else {
// No point in compressing very short messages
hm.hdr.compression = false
msgBuf = msgBuf[:cap(msgBuf)]
if l := len(uncBuf) + 8; l > len(msgBuf) {
msgBuf = make([]byte, l)
}
binary.BigEndian.PutUint32(msgBuf[4:8], uint32(len(uncBuf)))
msgBuf = msgBuf[0 : len(uncBuf)+8]
copy(msgBuf[8:], uncBuf)
if debug {
l.Debugf("write uncompressed message; %v (len=%d)", hm.hdr, len(uncBuf))
}
}
} else {
if debug {
l.Debugf("write empty message; %v", hm.hdr)
}
binary.BigEndian.PutUint32(msgBuf[4:8], 0)
msgBuf = msgBuf[:8]
}
binary.BigEndian.PutUint32(msgBuf[0:4], encodeHeader(hm.hdr))
if err == nil {
var n int
n, err = c.cw.Write(msgBuf)
if debug {
l.Debugf("wrote %d bytes on the wire", n)
}
}
if err != nil {
c.close(err)
return
}
case <-c.closed:
return
}
}
}
func (c *rawConnection) close(err error) {
c.once.Do(func() {
close(c.closed)
c.awaitingMut.Lock()
for i, ch := range c.awaiting {
if ch != nil {
close(ch)
c.awaiting[i] = nil
}
}
c.awaitingMut.Unlock()
go c.receiver.Close(c.id, err)
})
}
func (c *rawConnection) idGenerator() {
nextID := 0
for {
nextID = (nextID + 1) & 0xfff
select {
case c.nextID <- nextID:
case <-c.closed:
return
}
}
}
// The pingSender makes sure that we've sent a message within the last
// PingSendInterval. If we already have something sent in the last
// PingSendInterval/2, we do nothing. Otherwise we send a ping message. This
// results in an effecting ping interval of somewhere between
// PingSendInterval/2 and PingSendInterval.
func (c *rawConnection) pingSender() {
ticker := time.Tick(PingSendInterval / 2)
for {
select {
case <-ticker:
d := time.Since(c.cw.Last())
if d < PingSendInterval/2 {
if debug {
l.Debugln(c.id, "ping skipped after wr", d)
}
continue
}
if debug {
l.Debugln(c.id, "ping -> after", d)
}
c.ping()
case <-c.closed:
return
}
}
}
// The pingReciever checks that we've received a message (any message will do,
// but we expect pings in the absence of other messages) within the last
// ReceiveTimeout. If not, we close the connection with an ErrTimeout.
func (c *rawConnection) pingReceiver() {
ticker := time.Tick(ReceiveTimeout / 2)
for {
select {
case <-ticker:
d := time.Since(c.cr.Last())
if d > ReceiveTimeout {
if debug {
l.Debugln(c.id, "ping timeout", d)
}
c.close(ErrTimeout)
}
if debug {
l.Debugln(c.id, "last read within", d)
}
case <-c.closed:
return
}
}
}
type Statistics struct {
At time.Time
InBytesTotal int64
OutBytesTotal int64
}
func (c *rawConnection) Statistics() Statistics {
return Statistics{
At: time.Now(),
InBytesTotal: c.cr.Tot(),
OutBytesTotal: c.cw.Tot(),
}
}