config: add tcp4only for lvs whitelist! (#21552)

config/config.go

@@ -176,6 +176,9 @@ type Config struct {
 	// where M is the element literal length and w is the number of bytes required for the maximum-length character in the character set.
 	// See https://dev.mysql.com/doc/refman/8.0/en/string-type-syntax.html for more details.
 	EnableEnumLengthLimit bool `toml:"enable-enum-length-limit" json:"enable-enum-length-limit"`
+	// EnableTCP4Only enables net.Listen("tcp4",...)
+	// Note that: it can make lvs with toa work and thus tidb can get real client ip.
+	EnableTCP4Only bool `toml:"enable-tcp4-only" json:"enable-tcp4-only"`
 }
 
 // UpdateTempStoragePath is to update the `TempStoragePath` if port/statusPort was changed

server/server.go

@@ -245,7 +245,11 @@ func NewServer(cfg *config.Config, driver IDriver) (*Server, error) {
 
 	if s.cfg.Host != "" && (s.cfg.Port != 0 || runInGoTest) {
 		addr := fmt.Sprintf("%s:%d", s.cfg.Host, s.cfg.Port)
-		if s.listener, err = net.Listen("tcp", addr); err == nil {
+		tcpProto := "tcp"
+		if s.cfg.EnableTCP4Only {
+			tcpProto = "tcp4"
+		}
+		if s.listener, err = net.Listen(tcpProto, addr); err == nil {
 			logutil.BgLogger().Info("server is running MySQL protocol", zap.String("addr", addr))
 			if cfg.Socket != "" {
 				if s.socket, err = net.Listen("unix", s.cfg.Socket); err == nil {