sniffing protocol for port forwarding

chain/hop.go

@@ -103,6 +103,16 @@ func (p *chainHop) Select(ctx context.Context, opts ...chain.SelectOption) *chai
 		if len(filters) == 0 {
 			filters = nodes
 		}
+	} else if protocol := options.Protocol; protocol != "" {
+		filters = nil
+		for _, node := range p.nodes {
+			if node == nil {
+				continue
+			}
+			if node.Options().Protocol == protocol {
+				filters = append(filters, node)
+			}
+		}
 	}
 
 	var nodes []*chain.Node

config/config.go

@@ -261,6 +261,7 @@ type ForwardNodeConfig struct {
 	Name     string   `yaml:",omitempty" json:"name,omitempty"`
 	Addr     string   `yaml:",omitempty" json:"addr,omitempty"`
 	Host     string   `yaml:",omitempty" json:"host,omitempty"`
+	Protocol string   `yaml:",omitempty" json:"protocol,omitempty"`
 	Bypass   string   `yaml:",omitempty" json:"bypass,omitempty"`
 	Bypasses []string `yaml:",omitempty" json:"bypasses,omitempty"`
 }
@@ -335,6 +336,7 @@ type NodeConfig struct {
 	Name      string           `json:"name"`
 	Addr      string           `yaml:",omitempty" json:"addr,omitempty"`
 	Host      string           `yaml:",omitempty" json:"host,omitempty"`
+	Protocol  string           `yaml:",omitempty" json:"protocol,omitempty"`
 	Interface string           `yaml:",omitempty" json:"interface,omitempty"`
 	SockOpts  *SockOptsConfig  `yaml:"sockopts,omitempty" json:"sockopts,omitempty"`
 	Bypass    string           `yaml:",omitempty" json:"bypass,omitempty"`

config/parsing/chain.go

@@ -216,6 +216,7 @@ func ParseHop(cfg *config.HopConfig) (chain.Hop, error) {
 			chain.HostMapperNodeOption(registry.HostsRegistry().Get(v.Hosts)),
 			chain.MetadataNodeOption(nm),
 			chain.HostNodeOption(host),
+			chain.ProtocolNodeOption(v.Protocol),
 		)
 		nodes = append(nodes, node)
 	}

config/parsing/service.go

@@ -250,6 +250,7 @@ func parseForwarder(cfg *config.ForwarderConfig) (chain.Hop, error) {
 						Name:     node.Name,
 						Addr:     node.Addr,
 						Host:     node.Host,
+						Protocol: node.Protocol,
 						Bypass:   node.Bypass,
 						Bypasses: node.Bypasses,
 					},

go.mod

@@ -7,7 +7,7 @@ require (
 	github.com/asaskevich/govalidator v0.0.0-20210307081110-f21760c49a8d
 	github.com/gin-contrib/cors v1.3.1
 	github.com/gin-gonic/gin v1.7.7
-	github.com/go-gost/core v0.0.0-20221129013900-0f0679a3ecbc
+	github.com/go-gost/core v0.0.0-20221130024727-8effb0b8b971
 	github.com/go-gost/gosocks4 v0.0.1
 	github.com/go-gost/gosocks5 v0.3.1-0.20211109033403-d894d75b7f09
 	github.com/go-gost/relay v0.1.1-0.20211123134818-8ef7fd81ffd7

go.sum

@@ -96,8 +96,8 @@ github.com/gin-gonic/gin v1.7.7/go.mod h1:axIBovoeJpVj8S3BwE0uPMTeReE4+AfFtqpqaZ
 github.com/go-gl/glfw v0.0.0-20190409004039-e6da0acd62b1/go.mod h1:vR7hzQXu2zJy9AVAgeJqvqgH9Q5CA+iKCZ2gyEVpxRU=
 github.com/go-gl/glfw/v3.3/glfw v0.0.0-20191125211704-12ad95a8df72/go.mod h1:tQ2UAYgL5IevRw8kRxooKSPJfGvJ9fJQFa0TUsXzTg8=
 github.com/go-gl/glfw/v3.3/glfw v0.0.0-20200222043503-6f7a984d4dc4/go.mod h1:tQ2UAYgL5IevRw8kRxooKSPJfGvJ9fJQFa0TUsXzTg8=
-github.com/go-gost/core v0.0.0-20221129013900-0f0679a3ecbc h1:LkielnJLsiOAnmgU88bW+73jZ07T4tyNb4jx94upm9g=
+github.com/go-gost/core v0.0.0-20221130024727-8effb0b8b971 h1:0AauAKN4J0ueS5yAdpQZEfhmUrPg1MZ/FBrGDmXyJi8=
-github.com/go-gost/core v0.0.0-20221129013900-0f0679a3ecbc/go.mod h1:bHVbCS9da6XtKNYMkMUVcck5UqDDUkyC37erVfs4GXQ=
+github.com/go-gost/core v0.0.0-20221130024727-8effb0b8b971/go.mod h1:bHVbCS9da6XtKNYMkMUVcck5UqDDUkyC37erVfs4GXQ=
 github.com/go-gost/gosocks4 v0.0.1 h1:+k1sec8HlELuQV7rWftIkmy8UijzUt2I6t+iMPlGB2s=
 github.com/go-gost/gosocks4 v0.0.1/go.mod h1:3B6L47HbU/qugDg4JnoFPHgJXE43Inz8Bah1QaN9qCc=
 github.com/go-gost/gosocks5 v0.3.1-0.20211109033403-d894d75b7f09 h1:A95M6UWcfZgOuJkQ7QLfG0Hs5peWIUSysCDNz4pfe04=

handler/forward/internal/forward/forward.go

@@ -14,7 +14,7 @@ import (
 	xio "github.com/go-gost/x/internal/io"
 )
 
-func SniffHost(ctx context.Context, rdw io.ReadWriter) (rw io.ReadWriter, host string, err error) {
+func Sniffing(ctx context.Context, rdw io.ReadWriter) (rw io.ReadWriter, host string, protocol string, err error) {
 	rw = rdw
 
 	// try to sniff TLS traffic
@@ -24,7 +24,8 @@ func SniffHost(ctx context.Context, rdw io.ReadWriter) (rw io.ReadWriter, host s
 	if err == nil &&
 		hdr[0] == dissector.Handshake &&
 		binary.BigEndian.Uint16(hdr[1:3]) == tls.VersionTLS10 {
-		return sniffSNI(ctx, rw)
+		rw, host, err = sniffSNI(ctx, rw)
+		return
 	}
 
 	// try to sniff HTTP traffic
@@ -39,6 +40,8 @@ func SniffHost(ctx context.Context, rdw io.ReadWriter) (rw io.ReadWriter, host s
 		}
 	}
 
+	protocol = sniffProtocol(hdr[:])
+
 	return
 }
 
@@ -82,3 +85,14 @@ func isHTTP(s string) bool {
 		strings.HasPrefix(http.MethodConnect, s) ||
 		strings.HasPrefix(http.MethodTrace, s)
 }
+
+const (
+	SSHv2 = "SSH-2"
+)
+
+func sniffProtocol(hdr []byte) string {
+	if string(hdr) == SSHv2 {
+		return "ssh"
+	}
+	return ""
+}

handler/forward/local/handler.go

@@ -93,15 +93,20 @@ func (h *forwardHandler) Handle(ctx context.Context, conn net.Conn, opts ...hand
 
 	var rw io.ReadWriter = conn
 	var host string
+	var protocol string
 	if h.md.sniffing {
 		if network == "tcp" {
-			rw, host, _ = forward.SniffHost(ctx, conn)
+			rw, host, protocol, _ = forward.Sniffing(ctx, conn)
+			h.options.Logger.Debugf("sniffing: host=%s, protocol=%s", host, protocol)
 		}
 	}
 
 	var target *chain.Node
 	if h.hop != nil {
-		target = h.hop.Select(ctx, chain.HostSelectOption(host))
+		target = h.hop.Select(ctx,
+			chain.HostSelectOption(host),
+			chain.ProtocolSelectOption(protocol),
+		)
 	}
 	if target == nil {
 		err := errors.New("target not available")

handler/forward/remote/handler.go

@@ -84,14 +84,18 @@ func (h *forwardHandler) Handle(ctx context.Context, conn net.Conn, opts ...hand
 
 	var rw io.ReadWriter = conn
 	var host string
+	var protocol string
 	if h.md.sniffing {
 		if network == "tcp" {
-			rw, host, _ = forward.SniffHost(ctx, conn)
+			rw, host, protocol, _ = forward.Sniffing(ctx, conn)
 		}
 	}
 	var target *chain.Node
 	if h.hop != nil {
-		target = h.hop.Select(ctx, chain.HostSelectOption(host))
+		target = h.hop.Select(ctx,
+			chain.HostSelectOption(host),
+			chain.ProtocolSelectOption(protocol),
+		)
 	}
 	if target == nil {
 		err := errors.New("target not available")