Add proxy protocol support

outbound/direct.go

@@ -3,14 +3,18 @@ package outbound
 import (
 	"context"
 	"net"
+	"net/netip"
 
 	"github.com/sagernet/sing-box/adapter"
 	"github.com/sagernet/sing-box/common/dialer"
 	C "github.com/sagernet/sing-box/constant"
 	"github.com/sagernet/sing-box/log"
 	"github.com/sagernet/sing-box/option"
+	E "github.com/sagernet/sing/common/exceptions"
 	M "github.com/sagernet/sing/common/metadata"
 	N "github.com/sagernet/sing/common/network"
+
+	"github.com/pires/go-proxyproto"
 )
 
 var _ adapter.Outbound = (*Direct)(nil)
@@ -20,9 +24,10 @@ type Direct struct {
 	dialer              N.Dialer
 	overrideOption      int
 	overrideDestination M.Socksaddr
+	proxyProto          uint8
 }
 
-func NewDirect(router adapter.Router, logger log.ContextLogger, tag string, options option.DirectOutboundOptions) *Direct {
+func NewDirect(router adapter.Router, logger log.ContextLogger, tag string, options option.DirectOutboundOptions) (*Direct, error) {
 	outbound := &Direct{
 		myOutboundAdapter: myOutboundAdapter{
 			protocol: C.TypeDirect,
@@ -31,7 +36,11 @@ func NewDirect(router adapter.Router, logger log.ContextLogger, tag string, opti
 			logger:   logger,
 			tag:      tag,
 		},
-		dialer: dialer.NewOutbound(router, options.OutboundDialerOptions),
+		dialer:     dialer.NewOutbound(router, options.OutboundDialerOptions),
+		proxyProto: options.ProxyProtocol,
+	}
+	if options.ProxyProtocol > 2 {
+		return nil, E.New("invalid proxy protocol option: ", options.ProxyProtocol)
 	}
 	if options.OverrideAddress != "" && options.OverridePort != 0 {
 		outbound.overrideOption = 1
@@ -43,11 +52,12 @@ func NewDirect(router adapter.Router, logger log.ContextLogger, tag string, opti
 		outbound.overrideOption = 3
 		outbound.overrideDestination = M.Socksaddr{Port: options.OverridePort}
 	}
-	return outbound
+	return outbound, nil
 }
 
 func (h *Direct) DialContext(ctx context.Context, network string, destination M.Socksaddr) (net.Conn, error) {
 	ctx, metadata := adapter.AppendContext(ctx)
+	originDestination := metadata.Destination
 	metadata.Outbound = h.tag
 	metadata.Destination = destination
 	switch h.overrideOption {
@@ -60,13 +70,33 @@ func (h *Direct) DialContext(ctx context.Context, network string, destination M.
 	case 3:
 		destination.Port = h.overrideDestination.Port
 	}
+	network = N.NetworkName(network)
 	switch network {
 	case N.NetworkTCP:
 		h.logger.InfoContext(ctx, "outbound connection to ", destination)
 	case N.NetworkUDP:
 		h.logger.InfoContext(ctx, "outbound packet connection to ", destination)
 	}
-	return h.dialer.DialContext(ctx, network, destination)
+	conn, err := h.dialer.DialContext(ctx, network, destination)
+	if err != nil {
+		return nil, err
+	}
+	if h.proxyProto > 0 {
+		source := metadata.Source
+		if !source.IsValid() {
+			source = M.SocksaddrFromNet(conn.LocalAddr())
+		}
+		if originDestination.Addr.Is6() {
+			source = M.SocksaddrFrom(netip.AddrFrom16(source.Addr.As16()), source.Port)
+		}
+		header := proxyproto.HeaderProxyFromAddrs(h.proxyProto, source.TCPAddr(), originDestination.TCPAddr())
+		_, err = header.WriteTo(conn)
+		if err != nil {
+			conn.Close()
+			return nil, E.Cause(err, "write proxy protocol header")
+		}
+	}
+	return conn, nil
 }
 
 func (h *Direct) ListenPacket(ctx context.Context, destination M.Socksaddr) (net.PacketConn, error) {