iptables -t mangle -A ISTIO_OUTPUT -m connmark --mark 0x111/0xfff -j CONNMARK --restore-mark --nfmask 0xffffffff --ctmask 0xffffffff
iptables -t nat -A ISTIO_OUTPUT ! -o lo -p udp -m udp --dport 53 -j REDIRECT --to-port 15053
iptables -t nat -A ISTIO_OUTPUT -p tcp -m mark --mark 0x111/0xfff -j ACCEPT
iptables -t nat -A ISTIO_OUTPUT ! -d 127.0.0.1/32 -o lo -j ACCEPT

iptables -t mangle -A ISTIO_OUTPUT -m connmark --mark 0x111/0xfff -j CONNMARK --restore-mark --nfmask 0xffffffff --ctmask 0xffffffff
iptables -t nat -A ISTIO_OUTPUT ! -o lo -p udp -m udp --dport 53 -j REDIRECT --to-port 15053
iptables -t nat -A ISTIO_OUTPUT -p tcp -m mark --mark 0x111/0xfff -j ACCEPT
iptables -t nat -A ISTIO_OUTPUT ! -d 127.0.0.1/32 -o lo -j ACCEPT

	)

	// CLI: -A ISTIO_OUTPUT ! -o lo -p udp -m udp --dport 53 -j REDIRECT --to-port 15053
	//
	// DESC: If this is a UDP DNS request to a non-localhost resolver, send it to ztunnel DNS proxy port
	if redirectDNS {
		iptablesBuilder.AppendRule(
			iptableslog.UndefinedCommand, ChainInpodOutput, iptablesconstants.NAT,
			"!", "-o", "lo",
			"-p", "udp",
			"-m", "udp",
			"--dport", "53",
			"-j", "REDIRECT",

   *
   * [rfc_7540_34]: https://tools.ietf.org/html/rfc7540.section-3.4
   */
  H2_PRIOR_KNOWLEDGE("h2_prior_knowledge"),

  /**
   * QUIC (Quick UDP Internet Connection) is a new multiplexed and secure transport atop UDP,
   * designed from the ground up and optimized for HTTP/2 semantics. HTTP/1.1 semantics are layered
   * on HTTP/2.
   *

  // * must start and end with an alphanumeric character.
  // Default is empty string.
  optional string name = 1;

  // protocol represents the IP protocol for this port.
  // Must be UDP, TCP, or SCTP.
  // Default is TCP.
  optional string protocol = 2;

  // port represents the port number of the endpoint.
  // If this is not specified, ports are not restricted and must be

  // * must start and end with an alphanumeric character.
  // Default is empty string.
  optional string name = 1;

  // protocol represents the IP protocol for this port.
  // Must be UDP, TCP, or SCTP.
  // Default is TCP.
  optional string protocol = 2;

  // port represents the port number of the endpoint.
  // If this is not specified, ports are not restricted and must be

          port: 80
          protocol: TCP
kind: List
metadata:
  resourceVersion: ""`
	udpService = `
kind: Service
metadata:
  name: hello
spec:
  ports:
    -
      protocol: udp`
	skippedService = `
kind: Service
metadata:
  name: hello
  namespace: istio-system
spec:
  ports:
    -
      name: http
      port: 9080`
	validPortNamingSvc = `
apiVersion: v1

message IngressPortStatus {
  // port is the port number of the ingress port.
  optional int32 port = 1;

  // protocol is the protocol of the ingress port.
  // The supported values are: "TCP", "UDP", "SCTP"
  optional string protocol = 2;

  // error is to record the problem with the service port
  // The format of the error shall comply with the following rules:

   '--filename=rsrc.json'`)

	validFields = map[string]struct{}{
		"apiVersion": {},
		"kind":       {},
		"metadata":   {},
		"spec":       {},
		"status":     {},
	}

	serviceProtocolUDP = "UDP"

	fileExtensions = []string{".json", ".yaml", ".yml"}
)

type validator struct{}

func checkFields(un *unstructured.Unstructured) error {
	var errs error
	for key := range un.Object {

## Goals

Ztunnel should:
* **Not break users**. This means that deploying Ztunnel should retain all existing Kubernetes behavior.
  * This includes UDP, non-compliant HTTP, server-first protocols, stateful sets, external services, etc.
  * Explicitly opting into behavioral changes can be acceptable. For example, introducing Istio multi-cluster semantics.