add udp redirect listener

pkg/listener/redirect/udp/conn.go

@@ -0,0 +1,42 @@
+package udp
+
+import (
+	"net"
+	"sync"
+	"time"
+
+	"github.com/go-gost/gost/pkg/common/bufpool"
+)
+
+type redirConn struct {
+	net.Conn
+	buf  []byte
+	ttl  time.Duration
+	once sync.Once
+}
+
+func (c *redirConn) Read(b []byte) (n int, err error) {
+	if c.ttl > 0 {
+		c.SetReadDeadline(time.Now().Add(c.ttl))
+		defer c.SetReadDeadline(time.Time{})
+	}
+
+	c.once.Do(func() {
+		n = copy(b, c.buf)
+		bufpool.Put(c.buf)
+		c.buf = nil
+	})
+
+	if n == 0 {
+		n, err = c.Conn.Read(b)
+	}
+	return
+}
+
+func (c *redirConn) Write(b []byte) (n int, err error) {
+	if c.ttl > 0 {
+		c.SetWriteDeadline(time.Now().Add(c.ttl))
+		defer c.SetWriteDeadline(time.Time{})
+	}
+	return c.Conn.Write(b)
+}

pkg/listener/redirect/udp/listener.go

@@ -0,0 +1,63 @@
+package udp
+
+import (
+	"net"
+
+	"github.com/go-gost/gost/pkg/listener"
+	"github.com/go-gost/gost/pkg/logger"
+	md "github.com/go-gost/gost/pkg/metadata"
+	"github.com/go-gost/gost/pkg/registry"
+)
+
+func init() {
+	registry.RegisterListener("redu", NewListener)
+}
+
+type redirectListener struct {
+	addr   string
+	ln     *net.UDPConn
+	logger logger.Logger
+	md     metadata
+}
+
+func NewListener(opts ...listener.Option) listener.Listener {
+	options := &listener.Options{}
+	for _, opt := range opts {
+		opt(options)
+	}
+	return &redirectListener{
+		addr:   options.Addr,
+		logger: options.Logger,
+	}
+}
+
+func (l *redirectListener) Init(md md.Metadata) (err error) {
+	if err = l.parseMetadata(md); err != nil {
+		return
+	}
+
+	laddr, err := net.ResolveUDPAddr("udp", l.addr)
+	if err != nil {
+		return
+	}
+
+	ln, err := l.listenUDP(laddr)
+	if err != nil {
+		return
+	}
+
+	l.ln = ln
+	return
+}
+
+func (l *redirectListener) Accept() (conn net.Conn, err error) {
+	return l.accept()
+}
+
+func (l *redirectListener) Addr() net.Addr {
+	return l.ln.LocalAddr()
+}
+
+func (l *redirectListener) Close() error {
+	return l.ln.Close()
+}

pkg/listener/redirect/udp/listener_linux.go

@@ -0,0 +1,37 @@
+package udp
+
+import (
+	"net"
+
+	"github.com/LiamHaworth/go-tproxy"
+	"github.com/go-gost/gost/pkg/common/bufpool"
+)
+
+func (l *redirectListener) listenUDP(addr *net.UDPAddr) (*net.UDPConn, error) {
+	return tproxy.ListenUDP("udp", addr)
+}
+
+func (l *redirectListener) accept() (conn net.Conn, err error) {
+	b := bufpool.Get(l.md.readBufferSize)
+
+	n, raddr, dstAddr, err := tproxy.ReadFromUDP(l.ln, b)
+	if err != nil {
+		l.logger.Error(err)
+		return
+	}
+
+	l.logger.Infof("%s >> %s", raddr.String(), dstAddr.String())
+
+	c, err := tproxy.DialUDP("udp", dstAddr, raddr)
+	if err != nil {
+		l.logger.Error(err)
+		return
+	}
+
+	conn = &redirConn{
+		Conn: c,
+		buf:  b[:n],
+		ttl:  l.md.ttl,
+	}
+	return
+}

pkg/listener/redirect/udp/listener_other.go

@@ -0,0 +1,16 @@
+//go:build !linux
+
+package udp
+
+import (
+	"errors"
+	"net"
+)
+
+func (l *redirectListener) listenUDP(addr *net.UDPAddr) (*net.UDPConn, error) {
+	return nil, errors.New("UDP redirect is not available on non-linux platform")
+}
+
+func (l *redirectListener) accept() (conn net.Conn, err error) {
+	return nil, errors.New("UDP redirect is not available on non-linux platform")
+}

pkg/listener/redirect/udp/metadata.go

@@ -0,0 +1,36 @@
+package udp
+
+import (
+	"time"
+
+	md "github.com/go-gost/gost/pkg/metadata"
+)
+
+const (
+	defaultTTL            = 60 * time.Second
+	defaultReadBufferSize = 1024
+)
+
+type metadata struct {
+	ttl            time.Duration
+	readBufferSize int
+}
+
+func (l *redirectListener) parseMetadata(md md.Metadata) (err error) {
+	const (
+		ttl            = "ttl"
+		readBufferSize = "readBufferSize"
+	)
+
+	l.md.ttl = md.GetDuration(ttl)
+	if l.md.ttl <= 0 {
+		l.md.ttl = defaultTTL
+	}
+
+	l.md.readBufferSize = md.GetInt(readBufferSize)
+	if l.md.readBufferSize <= 0 {
+		l.md.readBufferSize = defaultReadBufferSize
+	}
+
+	return
+}