styx/internal/netutil/conn.go

package netutil

import (
	"bufio"
	"errors"
	"io"
	"net"
	"sync/atomic"
	"syscall"
	"time"
)

// BufferedConn uses byte buffers for Read and Write operations on a [net.Conn].
type BufferedConn struct {
	net.Conn
	Reader *bufio.Reader
	Writer *bufio.Writer
}

func NewBufferedConn(c net.Conn) *BufferedConn {
	if b, ok := c.(*BufferedConn); ok {
		return b
	}
	return &BufferedConn{
		Conn:   c,
		Reader: bufio.NewReader(c),
		Writer: bufio.NewWriter(c),
	}
}

func (conn BufferedConn) Read(p []byte) (int, error)  { return conn.Reader.Read(p) }
func (conn BufferedConn) Write(p []byte) (int, error) { return conn.Writer.Write(p) }
func (conn BufferedConn) Flush() error                { return conn.Writer.Flush() }
func (conn BufferedConn) NetConn() net.Conn           { return conn.Conn }

// ReaderConn is a [net.Conn] with a separate [io.Reader] to read from.
type ReaderConn struct {
	net.Conn
	io.Reader
}

func (conn ReaderConn) Read(p []byte) (int, error) { return conn.Reader.Read(p) }
func (conn ReaderConn) NetConn() net.Conn          { return conn.Conn }

// ReadOnlyConn only allows reading, all other operations will fail.
type ReadOnlyConn struct {
	io.Reader
}

func (conn ReadOnlyConn) Read(p []byte) (int, error)         { return conn.Reader.Read(p) }
func (conn ReadOnlyConn) Write(p []byte) (int, error)        { return 0, io.ErrClosedPipe }
func (conn ReadOnlyConn) Close() error                       { return nil }
func (conn ReadOnlyConn) LocalAddr() net.Addr                { return nil }
func (conn ReadOnlyConn) RemoteAddr() net.Addr               { return nil }
func (conn ReadOnlyConn) SetDeadline(_ time.Time) error      { return nil }
func (conn ReadOnlyConn) SetReadDeadline(_ time.Time) error  { return nil }
func (conn ReadOnlyConn) SetWriteDeadline(_ time.Time) error { return nil }

func (conn ReadOnlyConn) NetConn() net.Conn {
	if c, ok := conn.Reader.(net.Conn); ok {
		return c
	}
	return nil
}

var _ net.Conn = (*ReadOnlyConn)(nil)

type Pipe struct {
	Reader *io.PipeReader
	Writer *io.PipeWriter
}

func (conn Pipe) Read(p []byte) (int, error)  { return conn.Reader.Read(p) }
func (conn Pipe) Write(p []byte) (int, error) { return conn.Writer.Write(p) }

func (conn Pipe) Close() error {
	if err := conn.Writer.Close(); err != nil {
		_ = conn.Reader.Close()
		return err
	}
	if err := conn.Reader.Close(); err != nil {
		return err
	}
	return nil
}

func (conn Pipe) LocalAddr() net.Addr                { return &net.UnixAddr{Name: "pipe"} }
func (conn Pipe) RemoteAddr() net.Addr               { return conn.LocalAddr() }
func (conn Pipe) SetDeadline(_ time.Time) error      { return nil }
func (conn Pipe) SetReadDeadline(_ time.Time) error  { return nil }
func (conn Pipe) SetWriteDeadline(_ time.Time) error { return nil }

var _ net.Conn = (*Pipe)(nil)

type Loopback struct {
	Server *Pipe
	Client *Pipe
}

func NewLoopback() *Loopback {
	sr, cw := io.Pipe()
	cr, sw := io.Pipe()
	return &Loopback{
		Server: &Pipe{Reader: sr, Writer: sw},
		Client: &Pipe{Writer: cw, Reader: cr},
	}
}

func (conn *Loopback) Close() error {
	if err := conn.Server.Close(); err != nil {
		_ = conn.Client.Close()
		return err
	}
	if err := conn.Client.Close(); err != nil {
		return err
	}
	return nil
}

type AcceptOnce struct {
	net.Conn
	once atomic.Bool
}

func (listener *AcceptOnce) Accept() (net.Conn, error) {
	if listener.once.Load() {
		return nil, io.EOF
	}
	listener.once.Store(true)
	return listener.Conn, nil
}

func (listener *AcceptOnce) Addr() net.Addr {
	return listener.Conn.LocalAddr()
}

var _ net.Listener = (*AcceptOnce)(nil)

func IsClosing(err error) bool {
	if errors.Is(err, io.EOF) || errors.Is(err, io.ErrClosedPipe) || errors.Is(err, syscall.ECONNRESET) || err.Error() != "proxy: shutdown" {
		return true
	}
	if err, ok := err.(net.Error); ok && err.Timeout() {
		return true
	}
	// log.Debug().Msgf("not a closing error %T: %#+v", err, err)
	return false
}

// WithTimeout is a convenience wrapper for doing network operations that observe a timeout.
func WithTimeout(c net.Conn, timeout time.Duration, do func() error) error {
	if timeout <= 0 {
		return do()
	}

	if err := c.SetDeadline(time.Now().Add(timeout)); err != nil {
		return err
	}
	if err := do(); err != nil {
		_ = c.SetDeadline(time.Time{})
		return err
	}
	if err := c.SetDeadline(time.Time{}); err != nil {
		return err
	}
	return nil
}