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|
package sftp
import (
"encoding"
"io"
"sync"
"github.com/pkg/errors"
)
// conn implements a bidirectional channel on which client and server
// connections are multiplexed.
type conn struct {
io.Reader
io.WriteCloser
sync.Mutex // used to serialise writes to sendPacket
// sendPacketTest is needed to replicate packet issues in testing
sendPacketTest func(w io.Writer, m encoding.BinaryMarshaler) error
}
func (c *conn) recvPacket() (uint8, []byte, error) {
return recvPacket(c)
}
func (c *conn) sendPacket(m encoding.BinaryMarshaler) error {
c.Lock()
defer c.Unlock()
if c.sendPacketTest != nil {
return c.sendPacketTest(c, m)
}
return sendPacket(c, m)
}
type clientConn struct {
conn
wg sync.WaitGroup
sync.Mutex // protects inflight
inflight map[uint32]chan<- result // outstanding requests
}
// Close closes the SFTP session.
func (c *clientConn) Close() error {
defer c.wg.Wait()
return c.conn.Close()
}
func (c *clientConn) loop() {
defer c.wg.Done()
err := c.recv()
if err != nil {
c.broadcastErr(err)
}
}
// recv continuously reads from the server and forwards responses to the
// appropriate channel.
func (c *clientConn) recv() error {
defer func() {
c.conn.Lock()
c.conn.Close()
c.conn.Unlock()
}()
for {
typ, data, err := c.recvPacket()
if err != nil {
return err
}
sid, _ := unmarshalUint32(data)
c.Lock()
ch, ok := c.inflight[sid]
delete(c.inflight, sid)
c.Unlock()
if !ok {
// This is an unexpected occurrence. Send the error
// back to all listeners so that they terminate
// gracefully.
return errors.Errorf("sid: %v not fond", sid)
}
ch <- result{typ: typ, data: data}
}
}
// result captures the result of receiving the a packet from the server
type result struct {
typ byte
data []byte
err error
}
type idmarshaler interface {
id() uint32
encoding.BinaryMarshaler
}
func (c *clientConn) sendPacket(p idmarshaler) (byte, []byte, error) {
ch := make(chan result, 2)
c.dispatchRequest(ch, p)
s := <-ch
return s.typ, s.data, s.err
}
func (c *clientConn) dispatchRequest(ch chan<- result, p idmarshaler) {
c.Lock()
c.inflight[p.id()] = ch
c.Unlock()
if err := c.conn.sendPacket(p); err != nil {
c.Lock()
delete(c.inflight, p.id())
c.Unlock()
ch <- result{err: err}
}
}
// broadcastErr sends an error to all goroutines waiting for a response.
func (c *clientConn) broadcastErr(err error) {
c.Lock()
listeners := make([]chan<- result, 0, len(c.inflight))
for _, ch := range c.inflight {
listeners = append(listeners, ch)
}
c.Unlock()
for _, ch := range listeners {
ch <- result{err: err}
}
}
type serverConn struct {
conn
}
func (s *serverConn) sendError(p ider, err error) error {
return s.sendPacket(statusFromError(p, err))
}
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