cloudflare/cloudflared · error

%v is not valid IP

Error message

%v is not valid IP

What it means

registerUdpSession read the destination IP bytes from the RegisterUdpSession RPC parameters and net.IP(dstIPRaw) came back nil, meaning the bytes are not a valid 4- or 16-byte IP representation. cloudflared cannot route a UDP session without a valid destination address, so it rejects the registration.

Source

Thrown at tunnelrpc/pogs/session_manager.go:57

func (i SessionManager_PogsImpl) registerUdpSession(p proto.SessionManager_registerUdpSession) error {
	server.Ack(p.Options)

	sessionIDRaw, err := p.Params.SessionId()
	if err != nil {
		return err
	}
	sessionID, err := uuid.FromBytes(sessionIDRaw)
	if err != nil {
		return err
	}

	dstIPRaw, err := p.Params.DstIp()
	if err != nil {
		return err
	}
	dstIP := net.IP(dstIPRaw)
	if dstIP == nil {
		return fmt.Errorf("%v is not valid IP", dstIPRaw)
	}
	dstPort := p.Params.DstPort()

	closeIdleAfterHint := time.Duration(p.Params.CloseAfterIdleHint())

	traceContext, err := p.Params.TraceContext()
	if err != nil {
		return err
	}

	resp, registrationErr := i.impl.RegisterUdpSession(p.Ctx, sessionID, dstIP, dstPort, closeIdleAfterHint, traceContext)
	if registrationErr != nil {
		// Make sure to assign a response even if one is not returned from register
		if resp == nil {
			resp = &RegisterUdpSessionResponse{}
		}
		resp.Err = registrationErr
	}

View on GitHub (pinned to 2253eeeb25)

Solutions

1. Fix the caller to send a valid dst IP (net.ParseIP(...).To4()/.To16()) in RegisterUdpSessionParams.
2. Update cloudflared on both ends to matching versions to avoid payload skew.
3. Validate the destination before dialing (net.ParseIP on the configured host).

Example fix

// before
params := quicpogs.RegisterUdpSessionParams{DstIp: []byte("invalid")}
// after
ip := net.ParseIP("198.51.100.7")
params := quicpogs.RegisterUdpSessionParams{DstIp: ip.To4()}

ip := net.ParseIP(host)
if ip == nil {
    return fmt.Errorf("destination %q is not a valid IP", host)
}
params.DstIp = ip.To4()
if params.DstIp == nil { params.DstIp = ip.To16() }

func isValidDstIP(raw []byte) bool {
    return net.IP(raw) != nil && (len(raw) == 4 || len(raw) == 16)
}

When it happens

Trigger: A RegisterUdpSession RPC arrives whose Params carry a DstIp byte slice that is empty, wrong length, or malformed — i.e., not parseable as an IPv4/IPv6 address.

Common situations: Client-side bug sending uninitialized/garbage IP bytes; QUIC packet marshalled by an incompatible cloudflared version; corrupted RPC payload over the wire.

Related errors

• %s
• invalid datagram type expected
• flow not found
• cause
• unable to dial udp to origin %s: %w

AI-assisted analysis of cloudflare/cloudflared@2253eeeb25 (2026-09-06). Data as JSON: /api/errors/7bc85168846818b0. Report an issue: GitHub.