add tcp redirect

cmd/gost/register.go

@@ -20,6 +20,7 @@ import (
 	_ "github.com/go-gost/gost/pkg/handler/forward/local"
 	_ "github.com/go-gost/gost/pkg/handler/forward/remote"
 	_ "github.com/go-gost/gost/pkg/handler/http"
+	_ "github.com/go-gost/gost/pkg/handler/redirect"
 	_ "github.com/go-gost/gost/pkg/handler/relay"
 	_ "github.com/go-gost/gost/pkg/handler/sni"
 	_ "github.com/go-gost/gost/pkg/handler/socks/v4"

pkg/handler/redirect/handler.go

@@ -0,0 +1,114 @@
+package redirect
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"time"
+
+	"github.com/go-gost/gost/pkg/bypass"
+	"github.com/go-gost/gost/pkg/chain"
+	"github.com/go-gost/gost/pkg/handler"
+	"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.RegisterHandler("red", NewHandler)
+	registry.RegisterHandler("redir", NewHandler)
+	registry.RegisterHandler("redirect", NewHandler)
+}
+
+type redirectHandler struct {
+	chain  *chain.Chain
+	bypass bypass.Bypass
+	logger logger.Logger
+	md     metadata
+}
+
+func NewHandler(opts ...handler.Option) handler.Handler {
+	options := &handler.Options{}
+	for _, opt := range opts {
+		opt(options)
+	}
+
+	return &redirectHandler{
+		bypass: options.Bypass,
+		logger: options.Logger,
+	}
+}
+
+func (h *redirectHandler) Init(md md.Metadata) (err error) {
+	return h.parseMetadata(md)
+}
+
+// WithChain implements chain.Chainable interface
+func (h *redirectHandler) WithChain(chain *chain.Chain) {
+	h.chain = chain
+}
+
+func (h *redirectHandler) Handle(ctx context.Context, conn net.Conn) {
+	start := time.Now()
+	h.logger = h.logger.WithFields(map[string]interface{}{
+		"remote": conn.RemoteAddr().String(),
+		"local":  conn.LocalAddr().String(),
+	})
+
+	h.logger.Infof("%s <> %s", conn.RemoteAddr(), conn.LocalAddr())
+	defer func() {
+		h.logger.WithFields(map[string]interface{}{
+			"duration": time.Since(start),
+		}).Infof("%s >< %s", conn.RemoteAddr(), conn.LocalAddr())
+	}()
+
+	network := "tcp"
+	var dstAddr net.Addr
+	var err error
+
+	if _, ok := conn.(net.PacketConn); ok {
+		network = "udp"
+		dstAddr = conn.LocalAddr()
+	}
+
+	if network == "tcp" {
+		dstAddr, conn, err = h.getOriginalDstAddr(conn)
+		if err != nil {
+			h.logger.Error(err)
+			return
+		}
+	}
+	defer conn.Close()
+
+	h.logger = h.logger.WithFields(map[string]interface{}{
+		"dst": fmt.Sprintf("%s/%s", dstAddr, network),
+	})
+
+	h.logger.Infof("%s >> %s", conn.RemoteAddr(), dstAddr)
+
+	if h.bypass != nil && h.bypass.Contains(dstAddr.String()) {
+		h.logger.Info("bypass: ", dstAddr)
+		return
+	}
+
+	r := (&chain.Router{}).
+		WithChain(h.chain).
+		WithRetry(h.md.retryCount).
+		WithLogger(h.logger)
+
+	cc, err := r.Dial(ctx, network, dstAddr.String())
+	if err != nil {
+		h.logger.Error(err)
+		return
+	}
+	defer cc.Close()
+
+	t := time.Now()
+	h.logger.Infof("%s <-> %s", conn.RemoteAddr(), dstAddr)
+	handler.Transport(conn, cc)
+	h.logger.
+		WithFields(map[string]interface{}{
+			"duration": time.Since(t),
+		}).
+		Infof("%s >-< %s", conn.RemoteAddr(), dstAddr)
+}

pkg/handler/redirect/handler_linux.go

@@ -0,0 +1,41 @@
+package redirect
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"syscall"
+)
+
+func (h *redirectHandler) getOriginalDstAddr(conn net.Conn) (addr net.Addr, c net.Conn, err error) {
+	defer conn.Close()
+
+	tc, ok := conn.(*net.TCPConn)
+	if !ok {
+		err = errors.New("wrong connection type, must be TCP")
+		h.logger.Error(err)
+		return
+	}
+
+	fc, err := tc.File()
+	if err != nil {
+		return
+	}
+	defer fc.Close()
+
+	mreq, err := syscall.GetsockoptIPv6Mreq(int(fc.Fd()), syscall.IPPROTO_IP, 80)
+	if err != nil {
+		return
+	}
+
+	// only ipv4 support
+	ip := net.IPv4(mreq.Multiaddr[4], mreq.Multiaddr[5], mreq.Multiaddr[6], mreq.Multiaddr[7])
+	port := uint16(mreq.Multiaddr[2])<<8 + uint16(mreq.Multiaddr[3])
+	addr, err = net.ResolveTCPAddr("tcp4", fmt.Sprintf("%s:%d", ip.String(), port))
+	if err != nil {
+		return
+	}
+
+	c, err = net.FileConn(fc)
+	return
+}

pkg/handler/redirect/handler_other.go

@@ -0,0 +1,15 @@
+//go:build !linux
+
+package redirect
+
+import (
+	"errors"
+	"net"
+)
+
+func (h *redirectHandler) getOriginalDstAddr(conn net.Conn) (addr net.Addr, c net.Conn, err error) {
+	defer conn.Close()
+
+	err = errors.New("TCP redirect is not available on Windows platform")
+	return
+}

pkg/handler/redirect/metadata.go

@@ -0,0 +1,18 @@
+package redirect
+
+import (
+	md "github.com/go-gost/gost/pkg/metadata"
+)
+
+type metadata struct {
+	retryCount int
+}
+
+func (h *redirectHandler) parseMetadata(md md.Metadata) (err error) {
+	const (
+		retryCount = "retry"
+	)
+
+	h.md.retryCount = md.GetInt(retryCount)
+	return
+}