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|
package sftp
import (
"encoding"
"fmt"
"io"
"sync"
)
// conn implements a bidirectional channel on which client and server
// connections are multiplexed.
type conn struct {
io.Reader
io.WriteCloser
// this is the same allocator used in packet manager
alloc *allocator
sync.Mutex // used to serialise writes to sendPacket
}
// the orderID is used in server mode if the allocator is enabled.
// For the client mode just pass 0
func (c *conn) recvPacket(orderID uint32) (uint8, []byte, error) {
return recvPacket(c, c.alloc, orderID)
}
func (c *conn) sendPacket(m encoding.BinaryMarshaler) error {
c.Lock()
defer c.Unlock()
return sendPacket(c, m)
}
func (c *conn) Close() error {
c.Lock()
defer c.Unlock()
return c.WriteCloser.Close()
}
type clientConn struct {
conn
wg sync.WaitGroup
sync.Mutex // protects inflight
inflight map[uint32]chan<- result // outstanding requests
closed chan struct{}
err error
}
// Wait blocks until the conn has shut down, and return the error
// causing the shutdown. It can be called concurrently from multiple
// goroutines.
func (c *clientConn) Wait() error {
<-c.closed
return c.err
}
// 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 c.conn.Close()
for {
typ, data, err := c.recvPacket(0)
if err != nil {
return err
}
sid, _, err := unmarshalUint32Safe(data)
if err != nil {
return err
}
ch, ok := c.getChannel(sid)
if !ok {
// This is an unexpected occurrence. Send the error
// back to all listeners so that they terminate
// gracefully.
return fmt.Errorf("sid not found: %d", sid)
}
ch <- result{typ: typ, data: data}
}
}
func (c *clientConn) putChannel(ch chan<- result, sid uint32) bool {
c.Lock()
defer c.Unlock()
select {
case <-c.closed:
// already closed with broadcastErr, return error on chan.
ch <- result{err: ErrSSHFxConnectionLost}
return false
default:
}
c.inflight[sid] = ch
return true
}
func (c *clientConn) getChannel(sid uint32) (chan<- result, bool) {
c.Lock()
defer c.Unlock()
ch, ok := c.inflight[sid]
delete(c.inflight, sid)
return ch, ok
}
// 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(ch chan result, p idmarshaler) (byte, []byte, error) {
if cap(ch) < 1 {
ch = make(chan result, 1)
}
c.dispatchRequest(ch, p)
s := <-ch
return s.typ, s.data, s.err
}
// dispatchRequest should ideally only be called by race-detection tests outside of this file,
// where you have to ensure two packets are in flight sequentially after each other.
func (c *clientConn) dispatchRequest(ch chan<- result, p idmarshaler) {
sid := p.id()
if !c.putChannel(ch, sid) {
// already closed.
return
}
if err := c.conn.sendPacket(p); err != nil {
if ch, ok := c.getChannel(sid); ok {
ch <- result{err: err}
}
}
}
// broadcastErr sends an error to all goroutines waiting for a response.
func (c *clientConn) broadcastErr(err error) {
c.Lock()
defer c.Unlock()
bcastRes := result{err: ErrSSHFxConnectionLost}
for sid, ch := range c.inflight {
ch <- bcastRes
// Replace the chan in inflight,
// we have hijacked this chan,
// and this guarantees always-only-once sending.
c.inflight[sid] = make(chan<- result, 1)
}
c.err = err
close(c.closed)
}
type serverConn struct {
conn
}
func (s *serverConn) sendError(id uint32, err error) error {
return s.sendPacket(statusFromError(id, err))
}
|
