/
loopbackconn.go
226 lines (192 loc) · 4.19 KB
/
loopbackconn.go
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package libproxy
import (
"io"
"net"
"sync"
"time"
)
// io.Pipe is synchronous but we need to decouple the Read and Write calls
// with buffering. Adding bufio.NewWriter still requires domeone else to call
// `Flush` in a background thread to perform the write. It's simpler to create
// our own bufferedPipe out of an array of []byte
// - each direction within the connection is represented by a bufferedPipe
// - each bufferedPipe can be shutdown such that further writes return EOF
// and reads return EOF after the buffer is exhausted
type bufferedPipe struct {
bufs [][]byte
eof bool
m *sync.Mutex
c *sync.Cond
readDeadline time.Time
}
func newBufferedPipe() *bufferedPipe {
var m sync.Mutex
c := sync.NewCond(&m)
return &bufferedPipe{
m: &m,
c: c,
}
}
func (pipe *bufferedPipe) TryReadLocked(p []byte) (n int, err error) {
// drain buffers before considering EOF
if len(pipe.bufs) > 0 {
n := copy(p, pipe.bufs[0])
pipe.bufs[0] = pipe.bufs[0][n:]
if len(pipe.bufs[0]) == 0 {
// first fragment consumed
pipe.bufs = pipe.bufs[1:]
}
return n, nil
}
if pipe.eof {
return 0, io.EOF
}
return 0, nil
}
func (pipe *bufferedPipe) SetReadDeadline(deadline time.Time) error {
pipe.m.Lock()
defer pipe.m.Unlock()
pipe.readDeadline = deadline
pipe.c.Broadcast()
return nil
}
type errTimeout struct {
}
func (e *errTimeout) String() string {
return "i/o timeout"
}
func (e *errTimeout) Error() string {
return e.String()
}
func (e *errTimeout) Timeout() bool {
return true
}
func (e *errTimeout) Temporary() bool {
return true
}
func (pipe *bufferedPipe) Read(p []byte) (n int, err error) {
pipe.m.Lock()
defer pipe.m.Unlock()
for {
n, err := pipe.TryReadLocked(p)
if n > 0 || err != nil {
return n, err
}
done := make(chan struct{})
timeout := make(chan time.Time)
if !pipe.readDeadline.IsZero() {
go func() {
time.Sleep(time.Until(pipe.readDeadline))
close(timeout)
}()
}
go func() {
pipe.c.Wait()
close(done)
}()
select {
case <-timeout:
// Clean up the goroutine
pipe.c.Broadcast()
<-done
return n, &errTimeout{}
case <-done:
// The timeout will still fire in the background
continue
}
}
}
func (pipe *bufferedPipe) Write(p []byte) (n int, err error) {
buf := make([]byte, len(p))
copy(buf, p)
pipe.m.Lock()
defer pipe.m.Unlock()
if pipe.eof {
return 0, io.EOF
}
if len(p) == 0 {
return 0, nil
}
pipe.bufs = append(pipe.bufs, buf)
pipe.c.Broadcast()
return len(p), nil
}
func (pipe *bufferedPipe) closeWriteNoErr() {
pipe.m.Lock()
defer pipe.m.Unlock()
pipe.eof = true
pipe.c.Broadcast()
}
func (pipe *bufferedPipe) CloseWrite() error {
pipe.closeWriteNoErr()
return nil
}
type loopback struct {
write *bufferedPipe
read *bufferedPipe
simulateLatency time.Duration
}
func newLoopback() *loopback {
write := newBufferedPipe()
read := newBufferedPipe()
return &loopback{
write: write,
read: read,
}
}
func (l *loopback) LocalAddr() net.Addr {
return &addrLoopback{}
}
func (l *loopback) RemoteAddr() net.Addr {
return &addrLoopback{}
}
type addrLoopback struct {
}
func (a *addrLoopback) Network() string {
return "loopback"
}
func (a *addrLoopback) String() string {
return ""
}
func (l *loopback) SetReadDeadline(timeout time.Time) error {
return l.read.SetReadDeadline(timeout)
}
func (l *loopback) SetWriteDeadline(_ time.Time) error {
// Writes never block
return nil
}
func (l *loopback) SetDeadline(timeout time.Time) error {
if err := l.SetReadDeadline(timeout); err != nil {
return err
}
return l.SetWriteDeadline(timeout)
}
func (l *loopback) OtherEnd() *loopback {
return &loopback{
write: l.read,
read: l.write,
}
}
func (l *loopback) Read(p []byte) (n int, err error) {
return l.read.Read(p)
}
func (l *loopback) Write(p []byte) (n int, err error) {
n, err = l.write.Write(p)
time.Sleep(l.simulateLatency)
return
}
func (l *loopback) CloseRead() error {
return l.read.CloseWrite()
}
func (l *loopback) CloseWrite() error {
return l.write.CloseWrite()
}
func (l *loopback) Close() error {
err1 := l.CloseRead()
err2 := l.CloseWrite()
if err1 != nil {
return err1
}
return err2
}
var _ Conn = &loopback{}