1.支持指定IP出口，参数为bind=x.x.x.x

2.支持多网卡服务器，入口网卡作为出口网卡。

chain.go

@@ -151,17 +151,24 @@ func (c *Chain) dialWithOptions(ctx context.Context, network, address string, op
 	}
 
 	if route.IsEmpty() {
+		d := &net.Dialer{
+			Timeout: timeout,
+		}
 		switch network {
+		case "tcp", "tcp4", "tcp6":
+			d.LocalAddr = &net.TCPAddr{
+				IP: options.BindAddr,
+			}
 		case "udp", "udp4", "udp6":
 			if address == "" {
 				return net.ListenUDP(network, nil)
 			}
+			d.LocalAddr = &net.UDPAddr{
+				IP: options.BindAddr,
+			}
 		default:
 		}
-		d := &net.Dialer{
-			Timeout: timeout,
-			// LocalAddr: laddr, // TODO: optional local address
-		}
+
 		return d.DialContext(ctx, network, ipAddr)
 	}
 
@@ -325,6 +332,7 @@ func (c *Chain) selectRouteFor(addr string) (route *Chain, err error) {
 // ChainOptions holds options for Chain.
 type ChainOptions struct {
 	Retries  int
+	BindAddr net.IP //绑定地址
 	Timeout  time.Duration
 	Hosts    *Hosts
 	Resolver Resolver
@@ -360,3 +368,10 @@ func ResolverChainOption(resolver Resolver) ChainOption {
 		opts.Resolver = resolver
 	}
 }
+
+// BindChainOption specifies tcp bind address used by Chain.Dial.
+func BindChainOption(bindAddr net.IP) ChainOption {
+	return func(opts *ChainOptions) {
+		opts.BindAddr = bindAddr
+	}
+}

forward.go

@@ -128,9 +128,17 @@ func (h *tcpDirectForwardHandler) Handle(conn net.Conn) {
 			}
 		}
 
+		//指定出口IP地址,没有绑定出口IP地址才考虑以入口网卡作为出口
+		var bindAddr net.IP;
+		if h.options.Node.BindAddr == nil {
+			bindAddr = conn.LocalAddr().(*net.TCPAddr).IP
+		}else {
+			bindAddr = h.options.Node.BindAddr
+		}
 		cc, err = h.options.Chain.Dial(node.Addr,
 			RetryChainOption(h.options.Retries),
 			TimeoutChainOption(h.options.Timeout),
+			BindChainOption(bindAddr),
 		)
 		if err != nil {
 			log.Logf("[tcp] %s -> %s : %s", conn.RemoteAddr(), conn.LocalAddr(), err)
@@ -197,7 +205,17 @@ func (h *udpDirectForwardHandler) Handle(conn net.Conn) {
 		}
 	}
 
-	cc, err := h.options.Chain.DialContext(context.Background(), "udp", node.Addr)
+	//指定出口IP地址,没有绑定出口IP地址才考虑以入口网卡作为出口
+	var bindAddr net.IP;
+	if h.options.Node.BindAddr == nil {
+		bindAddr = conn.LocalAddr().(*net.UDPAddr).IP
+	}else {
+		bindAddr = h.options.Node.BindAddr
+	}
+	cc, err := h.options.Chain.DialContext(context.Background(),
+		"udp",
+		node.Addr,
+		BindChainOption(bindAddr),)
 	if err != nil {
 		node.MarkDead()
 		log.Logf("[udp] %s - %s : %s", conn.RemoteAddr(), conn.LocalAddr(), err)

http.go

@@ -261,10 +261,18 @@ func (h *httpHandler) handleRequest(conn net.Conn, req *http.Request) {
 			continue
 		}
 
+		//指定出口IP地址,没有绑定出口IP地址才考虑以入口网卡作为出口
+		var bindAddr net.IP;
+		if h.options.Node.BindAddr == nil {
+			bindAddr = conn.LocalAddr().(*net.TCPAddr).IP
+		}else {
+			bindAddr = h.options.Node.BindAddr
+		}
 		cc, err = route.Dial(host,
 			TimeoutChainOption(h.options.Timeout),
 			HostsChainOption(h.options.Hosts),
 			ResolverChainOption(h.options.Resolver),
+			BindChainOption(bindAddr),
 		)
 		if err == nil {
 			break

http2.go

@@ -424,10 +424,18 @@ func (h *http2Handler) roundTrip(w http.ResponseWriter, r *http.Request) {
 		fmt.Fprintf(&buf, "%s", host)
 		log.Log("[route]", buf.String())
 
+		//指定出口IP地址,没有绑定出口IP地址才考虑以入口网卡作为出口
+		var bindAddr net.IP;
+		if h.options.Node.BindAddr == nil {
+			bindAddr = net.ParseIP(laddr)
+		}else {
+			bindAddr = h.options.Node.BindAddr
+		}
 		cc, err = route.Dial(host,
 			TimeoutChainOption(h.options.Timeout),
 			HostsChainOption(h.options.Hosts),
 			ResolverChainOption(h.options.Resolver),
+			BindChainOption(bindAddr),
 		)
 		if err == nil {
 			break

node.go

@@ -3,6 +3,7 @@ package gost
 import (
 	"errors"
 	"fmt"
+	"net"
 	"net/url"
 	"strconv"
 	"strings"
@@ -22,6 +23,8 @@ type Node struct {
 	Host             string
 	Protocol         string
 	Transport        string
+	BindAddr         net.IP   // 绑定出口
+	OutFromIn        bool     // 是否使用入口IP网卡作为出口网卡，只有当没有绑定出口时才有效
 	Remote           string   // remote address, used by tcp/udp port forwarding
 	url              *url.URL // raw url
 	User             *url.Userinfo
@@ -54,12 +57,15 @@ func ParseNode(s string) (node Node, err error) {
 	node = Node{
 		Addr:   u.Host,
 		Host:   u.Host,
+		BindAddr: net.ParseIP(u.Query().Get("bind")),
 		Remote: strings.Trim(u.EscapedPath(), "/"),
 		Values: u.Query(),
 		User:   u.User,
 		marker: &failMarker{},
 		url:    u,
 	}
+	outFromIn, _ := strconv.ParseBool(u.Query().Get("outFromIn"))
+	node.OutFromIn = outFromIn
 
 	u.RawQuery = ""
 	u.User = nil

relay.go

@@ -221,10 +221,24 @@ func (h *relayHandler) Handle(conn net.Conn) {
 		}
 
 		log.Logf("[relay] %s -> %s -> %s", conn.RemoteAddr(), conn.LocalAddr(), raddr)
+
+		//指定出口IP地址,没有绑定出口IP地址才考虑以入口网卡作为出口
+		var bindAddr net.IP
+		if h.options.Node.BindAddr == nil {
+			switch addr := conn.LocalAddr().(type) {
+			case *net.TCPAddr:
+				bindAddr = addr.IP
+			case *net.UDPAddr:
+				bindAddr = addr.IP
+			}
+		}else {
+			bindAddr = h.options.Node.BindAddr
+		}
 		cc, err = h.options.Chain.DialContext(ctx,
 			network, raddr,
 			RetryChainOption(h.options.Retries),
 			TimeoutChainOption(h.options.Timeout),
+			BindChainOption(bindAddr),
 		)
 		if err != nil {
 			log.Logf("[relay] %s -> %s : %s", conn.RemoteAddr(), raddr, err)

sni.go

@@ -151,10 +151,18 @@ func (h *sniHandler) Handle(conn net.Conn) {
 		fmt.Fprintf(&buf, "%s", host)
 		log.Log("[route]", buf.String())
 
+		//指定出口IP地址,没有绑定出口IP地址才考虑以入口网卡作为出口
+		var bindAddr net.IP;
+		if h.options.Node.BindAddr == nil {
+			bindAddr = conn.LocalAddr().(*net.TCPAddr).IP
+		}else {
+			bindAddr = h.options.Node.BindAddr
+		}
 		cc, err = route.Dial(host,
 			TimeoutChainOption(h.options.Timeout),
 			HostsChainOption(h.options.Hosts),
 			ResolverChainOption(h.options.Resolver),
+			BindChainOption(bindAddr),
 		)
 		if err == nil {
 			break

socks.go

@@ -939,10 +939,24 @@ func (h *socks5Handler) handleConnect(conn net.Conn, req *gosocks5.Request) {
 		fmt.Fprintf(&buf, "%s", host)
 		log.Log("[route]", buf.String())
 
+		//指定出口IP地址,没有绑定出口IP地址才考虑以入口网卡作为出口
+		var bindAddr net.IP;
+		if h.options.Node.BindAddr == nil {
+			switch addr := conn.LocalAddr().(type) {
+			case *net.TCPAddr:
+				bindAddr = addr.IP
+			case *net.UDPAddr:
+				bindAddr = addr.IP
+			}
+		}else {
+			bindAddr = h.options.Node.BindAddr
+		}
+
 		cc, err = route.Dial(host,
 			TimeoutChainOption(h.options.Timeout),
 			HostsChainOption(h.options.Hosts),
 			ResolverChainOption(h.options.Resolver),
+			BindChainOption(bindAddr),
 		)
 		if err == nil {
 			break
@@ -1754,10 +1768,20 @@ func (h *socks4Handler) handleConnect(conn net.Conn, req *gosocks4.Request) {
 		fmt.Fprintf(&buf, "%s", addr)
 		log.Log("[route]", buf.String())
 
+		//指定出口IP地址,没有绑定出口IP地址才考虑以入口网卡作为出口
+		//socks4 只支持tcp
+		var bindAddr net.IP
+		if h.options.Node.BindAddr == nil {
+			bindAddr = conn.LocalAddr().(*net.TCPAddr).IP
+		}else {
+			bindAddr = h.options.Node.BindAddr
+		}
+
 		cc, err = route.Dial(addr,
 			TimeoutChainOption(h.options.Timeout),
 			HostsChainOption(h.options.Hosts),
 			ResolverChainOption(h.options.Resolver),
+			BindChainOption(bindAddr),
 		)
 		if err == nil {
 			break

ss.go

@@ -181,10 +181,23 @@ func (h *shadowHandler) Handle(conn net.Conn) {
 		fmt.Fprintf(&buf, "%s", host)
 		log.Log("[route]", buf.String())
 
+		//指定出口IP地址,没有绑定出口IP地址才考虑以入口网卡作为出口
+		var bindAddr net.IP;
+		if h.options.Node.BindAddr == nil {
+			switch addr := conn.LocalAddr().(type) {
+			case *net.TCPAddr:
+				bindAddr = addr.IP
+			case *net.UDPAddr:
+				bindAddr = addr.IP
+			}
+		}else {
+			bindAddr = h.options.Node.BindAddr
+		}
 		cc, err = route.Dial(host,
 			TimeoutChainOption(h.options.Timeout),
 			HostsChainOption(h.options.Hosts),
 			ResolverChainOption(h.options.Resolver),
+			BindChainOption(bindAddr),
 		)
 		if err == nil {
 			break