Outbound: One endpoint and at most one user only (#5144)

https://github.com/XTLS/Xray-core/pull/5124#issuecomment-3281091009

Fixes https://github.com/XTLS/Xray-core/pull/5124#pullrequestreview-3218097421

proxy/shadowsocks/client.go

@@ -22,27 +22,23 @@ import (
 
 // Client is a inbound handler for Shadowsocks protocol
 type Client struct {
-	serverPicker  protocol.ServerPicker
+	server        *protocol.ServerSpec
 	policyManager policy.Manager
 }
 
 // NewClient create a new Shadowsocks client.
 func NewClient(ctx context.Context, config *ClientConfig) (*Client, error) {
-	serverList := protocol.NewServerList()
-	for _, rec := range config.Server {
-		s, err := protocol.NewServerSpecFromPB(rec)
-		if err != nil {
-			return nil, errors.New("failed to parse server spec").Base(err)
-		}
-		serverList.AddServer(s)
+	if config.Server == nil {
+		return nil, errors.New(`no target server found`)
 	}
-	if serverList.Size() == 0 {
-		return nil, errors.New("0 server")
+	server, err := protocol.NewServerSpecFromPB(config.Server)
+	if err != nil {
+		return nil, errors.New("failed to get server spec").Base(err)
 	}
 
 	v := core.MustFromContext(ctx)
 	client := &Client{
-		serverPicker:  protocol.NewRoundRobinServerPicker(serverList),
+		server:        server,
 		policyManager: v.GetFeature(policy.ManagerType()).(policy.Manager),
 	}
 	return client, nil
@@ -60,13 +56,12 @@ func (c *Client) Process(ctx context.Context, link *transport.Link, dialer inter
 	destination := ob.Target
 	network := destination.Network
 
-	var server *protocol.ServerSpec
+	server := c.server
+	dest := server.Destination
+	dest.Network = network
 	var conn stat.Connection
 
 	err := retry.ExponentialBackoff(5, 100).On(func() error {
-		server = c.serverPicker.PickServer()
-		dest := server.Destination()
-		dest.Network = network
 		rawConn, err := dialer.Dial(ctx, dest)
 		if err != nil {
 			return err
@@ -78,7 +73,7 @@ func (c *Client) Process(ctx context.Context, link *transport.Link, dialer inter
 	if err != nil {
 		return errors.New("failed to find an available destination").AtWarning().Base(err)
 	}
-	errors.LogInfo(ctx, "tunneling request to ", destination, " via ", network, ":", server.Destination().NetAddr())
+	errors.LogInfo(ctx, "tunneling request to ", destination, " via ", network, ":", server.Destination.NetAddr())
 
 	defer conn.Close()
 
@@ -93,7 +88,7 @@ func (c *Client) Process(ctx context.Context, link *transport.Link, dialer inter
 		request.Command = protocol.RequestCommandUDP
 	}
 
-	user := server.PickUser()
+	user := server.User
 	_, ok := user.Account.(*MemoryAccount)
 	if !ok {
 		return errors.New("user account is not valid")