What causes "unkown parent type %s" in snail007/goproxy?

Set the parent type to a supported value (tcp, tls, udp) in the UDP service config

unkown parent type %s

Error message

unkown parent type %s

What it means

The UDP service callback dispatches packets to a parent based on cfg.ParentType. This error is the switch default branch: the configured ParentType is none of the supported values, so the packet cannot be forwarded and the failure is logged (the packet is dropped).

Source

Thrown at services/udp.go:80

func (s *UDP) Clean() {
	s.StopService()
}
func (s *UDP) callback(packet []byte, localAddr, srcAddr *net.UDPAddr) {
	defer func() {
		if err := recover(); err != nil {
			log.Printf("udp conn handler crashed with err : %s \nstack: %s", err, string(debug.Stack()))
		}
	}()
	var err error
	switch *s.cfg.ParentType {
	case TYPE_TCP:
		fallthrough
	case TYPE_TLS:
		err = s.OutToTCP(packet, localAddr, srcAddr)
	case TYPE_UDP:
		err = s.OutToUDP(packet, localAddr, srcAddr)
	default:
		err = fmt.Errorf("unkown parent type %s", *s.cfg.ParentType)
	}
	if err != nil {
		log.Printf("connect to %s parent %s fail, ERR:%s", *s.cfg.ParentType, *s.cfg.Parent, err)
	}
}
func (s *UDP) GetConn(connKey string) (conn net.Conn, isNew bool, err error) {
	isNew = !s.p.Has(connKey)
	var _conn interface{}
	if isNew {
		_conn, err = s.outPool.Pool.Get()
		if err != nil {
			return nil, false, err
		}
		s.p.Set(connKey, _conn)
	} else {
		_conn, _ = s.p.Get(connKey)
	}
	conn = _conn.(net.Conn)

View on GitHub (pinned to e6d6a821db)

Solutions

Set the parent type to a supported value (tcp, tls, udp) in the UDP service config
Normalize case/whitespace in the config value
Upgrade the binary if you intend to use a parent type this build does not support
Check the log line 'connect to %s parent %s fail' to see the offending value and correct it

Example fix

// before
// parent_type=UDP
// after
// parent_type=udp

Defensive patterns

Strategy: validation

Validate before calling

pt := strings.ToLower(strings.TrimSpace(cfg.ParentType))
if pt != "tcp" && pt != "tls" && pt != "udp" {
    return fmt.Errorf("udp service parent_type %q must be tcp|tls|udp", cfg.ParentType)
}

Try / catch

if err := svc.Start(); err != nil {
    if strings.Contains(err.Error(), "unkown parent type") {
        log.Fatalf("udp parent_type invalid: %q; set tcp|tls|udp", cfg.ParentType)
    }
}

Prevention

Set parent_type explicitly for UDP services; do not rely on defaults
Validate enum config values in CI before deploying
Use consistent lowercase values across all service configs
Re-check config after migrating between versions that support different parent types

When it happens

Trigger: *s.cfg.ParentType is not TYPE_TCP, TYPE_TLS, or TYPE_UDP — blank config value, typo, or unsupported mode — so callback's default case returns "unkown parent type %s".

Common situations: Missing udp_parent_type/parent_type setting; value written as 'TCP'/'Tls' with wrong case; config migrated from a build supporting extra parent types (e.g. kcp) not enabled in this binary.

Related errors

AI-assisted analysis of snail007/goproxy@e6d6a821db (2026-09-03). Data as JSON: /api/errors/27dd299f34d152e1. Report an issue: GitHub.