Add socks4/4a support

infra/conf/socks.go

@@ -2,6 +2,7 @@ package conf
 
 import (
 	"encoding/json"
+	"strings"
 
 	"github.com/golang/protobuf/proto"
 
@@ -74,11 +75,22 @@ type SocksRemoteConfig struct {
 
 type SocksClientConfig struct {
 	Servers []*SocksRemoteConfig `json:"servers"`
+	Version string               `json:"version"`
 }
 
 func (v *SocksClientConfig) Build() (proto.Message, error) {
 	config := new(socks.ClientConfig)
 	config.Server = make([]*protocol.ServerEndpoint, len(v.Servers))
+	switch strings.ToLower(v.Version) {
+	case "4":
+		config.Version = socks.Version_SOCKS4
+	case "4a":
+		config.Version = socks.Version_SOCKS4A
+	case "", "5":
+		config.Version = socks.Version_SOCKS5
+	default:
+		return nil, newError("failed to parse socks server version: ", v.Version).AtError()
+	}
 	for idx, serverConfig := range v.Servers {
 		server := &protocol.ServerEndpoint{
 			Address: serverConfig.Address.Build(),
@@ -93,6 +105,9 @@ func (v *SocksClientConfig) Build() (proto.Message, error) {
 			if err := json.Unmarshal(rawUser, account); err != nil {
 				return nil, newError("failed to parse socks account").Base(err).AtError()
 			}
+			if config.Version != socks.Version_SOCKS5 && account.Password != "" {
+				return nil, newError("password is only supported in socks5").AtError()
+			}
 			user.Account = serial.ToTypedMessage(account.Build())
 			server.User = append(server.User, user)
 		}

proxy/socks/client.go

@@ -16,6 +16,7 @@ import (
 	"github.com/v2fly/v2ray-core/v4/common/session"
 	"github.com/v2fly/v2ray-core/v4/common/signal"
 	"github.com/v2fly/v2ray-core/v4/common/task"
+	"github.com/v2fly/v2ray-core/v4/features/dns"
 	"github.com/v2fly/v2ray-core/v4/features/policy"
 	"github.com/v2fly/v2ray-core/v4/transport"
 	"github.com/v2fly/v2ray-core/v4/transport/internet"
@@ -25,6 +26,8 @@ import (
 type Client struct {
 	serverPicker  protocol.ServerPicker
 	policyManager policy.Manager
+	version       Version
+	dns           dns.Client
 }
 
 // NewClient create a new Socks5 client based on the given config.
@@ -42,10 +45,16 @@ func NewClient(ctx context.Context, config *ClientConfig) (*Client, error) {
 	}
 
 	v := core.MustFromContext(ctx)
-	return &Client{
+	c := &Client{
 		serverPicker:  protocol.NewRoundRobinServerPicker(serverList),
 		policyManager: v.GetFeature(policy.ManagerType()).(policy.Manager),
-	}, nil
+		version:       config.Version,
+	}
+	if config.Version == Version_SOCKS4 {
+		c.dns = v.GetFeature(dns.ClientType()).(dns.Client)
+	}
+
+	return c, nil
 }
 
 // Process implements proxy.Outbound.Process.
@@ -92,6 +101,39 @@ func (c *Client) Process(ctx context.Context, link *transport.Link, dialer inter
 		Address: destination.Address,
 		Port:    destination.Port,
 	}
+
+	switch c.version {
+	case Version_SOCKS4:
+		if request.Address.Family().IsDomain() {
+			if d, ok := c.dns.(dns.ClientWithIPOption); ok {
+				d.SetFakeDNSOption(false) // Skip FakeDNS
+			} else {
+				newError("DNS client doesn't implement ClientWithIPOption")
+			}
+
+			lookupFunc := c.dns.LookupIP
+			if lookupIPv4, ok := c.dns.(dns.IPv4Lookup); ok {
+				lookupFunc = lookupIPv4.LookupIPv4
+			}
+			ips, err := lookupFunc(request.Address.Domain())
+			if err != nil {
+				return err
+			} else if len(ips) == 0 {
+				return dns.ErrEmptyResponse
+			}
+			request.Address = net.IPAddress(ips[0])
+		}
+		fallthrough
+	case Version_SOCKS4A:
+		request.Version = socks4Version
+
+		if destination.Network == net.Network_UDP {
+			return newError("udp is not supported in socks4")
+		} else if destination.Address.Family().IsIPv6() {
+			return newError("ipv6 is not supported in socks4")
+		}
+	}
+
 	if destination.Network == net.Network_UDP {
 		request.Command = protocol.RequestCommandUDP
 	}

proxy/socks/config.proto

@@ -23,6 +23,13 @@ enum AuthType {
   PASSWORD = 1;
 }
 
+enum Version {
+  SOCKS5 = 0;
+  SOCKS4 = 1;
+  SOCKS4A = 2;
+}
+
+
 // ServerConfig is the protobuf config for Socks server.
 message ServerConfig {
   AuthType auth_type = 1;
@@ -37,4 +44,5 @@ message ServerConfig {
 message ClientConfig {
   // Sever is a list of Socks server addresses.
   repeated v2ray.core.common.protocol.ServerEndpoint server = 1;
+  Version version = 2;
 }