fix issue with out-of-order packets

examples/request-server/main.go

@@ -11,7 +11,7 @@ import (
 	"net"
 	"os"
 
-	"github.com/pkg/sftp"
+	"github.com/eikenb/sftp"
 	"golang.org/x/crypto/ssh"
 )
 

request-example.go

@@ -10,6 +10,7 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"sync"
 	"syscall"
 	"time"
 )
@@ -24,7 +25,7 @@ func InMemHandler() Handlers {
 }
 
 // Handlers
-func (fs *root) Fileread(r *Request) (io.Reader, error) {
+func (fs *root) Fileread(r *Request) (io.ReaderAt, error) {
 	file, err := fs.fetch(r.Filepath)
 	if err != nil {
 		return nil, err
@@ -35,10 +36,10 @@ func (fs *root) Fileread(r *Request) (io.Reader, error) {
 			return nil, err
 		}
 	}
-	return file.Reader()
+	return file.ReaderAt()
 }
 
-func (fs *root) Filewrite(r *Request) (io.Writer, error) {
+func (fs *root) Filewrite(r *Request) (io.WriterAt, error) {
 	file, err := fs.fetch(r.Filepath)
 	if err == os.ErrNotExist {
 		dir, err := fs.fetch(filepath.Dir(r.Filepath))
@@ -51,7 +52,7 @@ func (fs *root) Filewrite(r *Request) (io.Writer, error) {
 		file = newMemFile(r.Filepath, false)
 		fs.files[r.Filepath] = file
 	}
-	return file.Writer()
+	return file.WriterAt()
 }
 
 func (fs *root) Filecmd(r *Request) error {
@@ -144,11 +145,12 @@ func (fs *root) fetch(path string) (*memFile, error) {
 // Implements os.FileInfo, Reader and Writer interfaces.
 // These are the 3 interfaces necessary for the Handlers.
 type memFile struct {
-	name    string
-	content []byte
-	modtime time.Time
-	symlink string
-	isdir   bool
+	name        string
+	modtime     time.Time
+	symlink     string
+	isdir       bool
+	content     []byte
+	contentLock sync.RWMutex
 }
 
 // factory to make sure modtime is set
@@ -180,22 +182,30 @@ func (f *memFile) Sys() interface{} {
 }
 
 // Read/Write
-func (f *memFile) Reader() (io.Reader, error) {
+func (f *memFile) ReaderAt() (io.ReaderAt, error) {
 	if f.isdir {
 		return nil, os.ErrInvalid
 	}
 	return bytes.NewReader(f.content), nil
 }
 
-func (f *memFile) Writer() (io.Writer, error) {
+func (f *memFile) WriterAt() (io.WriterAt, error) {
 	if f.isdir {
 		return nil, os.ErrInvalid
 	}
 	return f, nil
 }
-func (f *memFile) Write(p []byte) (int, error) {
+func (f *memFile) WriteAt(p []byte, off int64) (int, error) {
 	// mimic write delays, should be optional
 	time.Sleep(time.Microsecond * time.Duration(len(p)))
-	f.content = append(f.content, p...)
+	f.contentLock.Lock()
+	defer f.contentLock.Unlock()
+	plen := len(p) + int(off)
+	if plen >= len(f.content) {
+		nc := make([]byte, plen)
+		copy(nc, f.content)
+		f.content = nc
+	}
+	copy(f.content[off:], p)
 	return len(p), nil
 }

request-interfaces.go

@@ -10,12 +10,12 @@ import (
 
 // FileReader should return an io.Reader for the filepath
 type FileReader interface {
-	Fileread(*Request) (io.Reader, error)
+	Fileread(*Request) (io.ReaderAt, error)
 }
 
 // FileWriter should return an io.Writer for the filepath
 type FileWriter interface {
-	Filewrite(*Request) (io.Writer, error)
+	Filewrite(*Request) (io.WriterAt, error)
 }
 
 // FileCmder should return an error (rename, remove, setstate, etc.)

request.go

@@ -5,6 +5,7 @@ import (
 	"os"
 	"path"
 	"path/filepath"
+	"sync"
 	"syscall"
 )
 
@@ -17,21 +18,47 @@ type Request struct {
 	Attrs    []byte // convert to sub-struct
 	Target   string // for renames and sym-links
 	// packet data
-	pkt_id uint32
-	data   []byte
-	length uint32
+	packets     []packet_data
+	packetsLock sync.RWMutex
 	// reader/writer from handlers
-	put_writer io.Writer
-	get_reader io.Reader
+	put_writer io.WriterAt
+	get_reader io.ReaderAt
 	eof        bool // hack for readdir to keep eof state
 }
 
+type packet_data struct {
+	id     uint32
+	data   []byte
+	length uint32
+	offset int64
+}
+
 // Here mainly to specify that Filepath is required
 func newRequest(path string) *Request {
 	request := &Request{Filepath: filepath.Clean(path)}
 	return request
 }
 
+// push packet_data into fifo
+func (r *Request) pushPacket(pd packet_data) {
+	r.packetsLock.Lock()
+	defer r.packetsLock.Unlock()
+	r.packets = append(r.packets, pd)
+}
+
+// pop packet_data into fifo
+func (r *Request) popPacket() packet_data {
+	r.packetsLock.Lock()
+	defer r.packetsLock.Unlock()
+	var pd packet_data
+	pd, r.packets = r.packets[0], r.packets[1:]
+	return pd
+}
+
+func (r *Request) pkt_id() uint32 {
+	return r.packets[0].id
+}
+
 // called from worker to handle packet/request
 func (r *Request) handle(handlers Handlers) (responsePacket, error) {
 	var err error
@@ -59,13 +86,15 @@ func fileget(h FileReader, r *Request) (responsePacket, error) {
 		r.get_reader = reader
 	}
 	reader := r.get_reader
-	data := make([]byte, clamp(r.length, maxTxPacket))
-	n, err := reader.Read(data)
+
+	pd := r.popPacket()
+	data := make([]byte, clamp(pd.length, maxTxPacket))
+	n, err := reader.ReadAt(data, pd.offset)
 	if err != nil && (err != io.EOF || n == 0) {
 		return nil, err
 	}
 	return &sshFxpDataPacket{
-		ID:     r.pkt_id,
+		ID:     pd.id,
 		Length: uint32(n),
 		Data:   data[:n],
 	}, nil
@@ -82,12 +111,13 @@ func fileput(h FileWriter, r *Request) (responsePacket, error) {
 	}
 	writer := r.put_writer
 
-	_, err := writer.Write(r.data)
+	pd := r.popPacket()
+	_, err := writer.WriteAt(pd.data, pd.offset)
 	if err != nil {
 		return nil, err
 	}
 	return &sshFxpStatusPacket{
-		ID: r.pkt_id,
+		ID: pd.id,
 		StatusError: StatusError{
 			Code: ssh_FX_OK,
 		}}, nil
@@ -100,7 +130,7 @@ func filecmd(h FileCmder, r *Request) (responsePacket, error) {
 		return nil, err
 	}
 	return &sshFxpStatusPacket{
-		ID: r.pkt_id,
+		ID: r.pkt_id(),
 		StatusError: StatusError{
 			Code: ssh_FX_OK,
 		}}, nil
@@ -119,7 +149,7 @@ func fileinfo(h FileInfoer, r *Request) (responsePacket, error) {
 	switch r.Method {
 	case "List":
 		dirname := path.Base(r.Filepath)
-		ret := &sshFxpNamePacket{ID: r.pkt_id}
+		ret := &sshFxpNamePacket{ID: r.pkt_id()}
 		for _, fi := range finfo {
 			ret.NameAttrs = append(ret.NameAttrs, sshFxpNameAttr{
 				Name:     fi.Name(),
@@ -136,7 +166,7 @@ func fileinfo(h FileInfoer, r *Request) (responsePacket, error) {
 			return nil, err
 		}
 		return &sshFxpStatResponse{
-			ID:   r.pkt_id,
+			ID:   r.pkt_id(),
 			info: finfo[0],
 		}, nil
 	case "Readlink":
@@ -147,7 +177,7 @@ func fileinfo(h FileInfoer, r *Request) (responsePacket, error) {
 		}
 		filename := finfo[0].Name()
 		return &sshFxpNamePacket{
-			ID: r.pkt_id,
+			ID: r.pkt_id(),
 			NameAttrs: []sshFxpNameAttr{{
 				Name:     filename,
 				LongName: filename,
@@ -161,50 +191,54 @@ func fileinfo(h FileInfoer, r *Request) (responsePacket, error) {
 // populate attributes of request object from packet data
 func (r *Request) populate(p interface{}) {
 	// r.Filepath should already be set
+	var pd packet_data
 	switch p := p.(type) {
 	case *sshFxpSetstatPacket:
 		r.Method = "Setstat"
 		r.Attrs = p.Attrs.([]byte)
-		r.pkt_id = p.id()
+		pd.id = p.id()
 	case *sshFxpFsetstatPacket:
 		r.Method = "Setstat"
 		r.Attrs = p.Attrs.([]byte)
-		r.pkt_id = p.id()
+		pd.id = p.id()
 	case *sshFxpRenamePacket:
 		r.Method = "Rename"
 		r.Target = filepath.Clean(p.Newpath)
-		r.pkt_id = p.id()
+		pd.id = p.id()
 	case *sshFxpSymlinkPacket:
 		r.Method = "Symlink"
 		r.Target = filepath.Clean(p.Linkpath)
-		r.pkt_id = p.id()
+		pd.id = p.id()
 	case *sshFxpReadPacket:
 		r.Method = "Get"
-		r.length = p.Len
-		r.pkt_id = p.id()
+		pd.length = p.Len
+		pd.offset = int64(p.Offset)
+		pd.id = p.id()
 	case *sshFxpWritePacket:
 		r.Method = "Put"
-		r.data = p.Data
-		r.length = p.Length
-		r.pkt_id = p.id()
+		pd.id = p.id()
+		pd.data = p.Data
+		pd.length = p.Length
+		pd.offset = int64(p.Offset)
 	case *sshFxpReaddirPacket:
 		r.Method = "List"
-		r.pkt_id = p.id()
+		pd.id = p.id()
 	case *sshFxpRemovePacket:
 		r.Method = "Remove"
-		r.pkt_id = p.id()
+		pd.id = p.id()
 	case *sshFxpStatPacket, *sshFxpLstatPacket, *sshFxpFstatPacket:
 		r.Method = "Stat"
-		r.pkt_id = p.(packet).id()
+		pd.id = p.(packet).id()
 	case *sshFxpRmdirPacket:
 		r.Method = "Rmdir"
-		r.pkt_id = p.id()
+		pd.id = p.id()
 	case *sshFxpReadlinkPacket:
 		r.Method = "Readlink"
-		r.pkt_id = p.id()
+		pd.id = p.id()
 	case *sshFxpMkdirPacket:
 		r.Method = "Mkdir"
-		r.pkt_id = p.id()
+		pd.id = p.id()
 		//r.Attrs are ignored in ./packet.go
 	}
+	r.pushPacket(pd)
 }