plugin/k8s_external: Resolve headless services (#5505)
*add option for resolving headless Services without external IPs in k8s_external Signed-off-by: Tomas Kohout <tomas.kohout1995@gmail.com>
This commit is contained in:
TomasKohout
GitHub
parent
b218b56063
commit
6782b7fb42
15 changed files with 491 additions and 81 deletions
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@ -11,9 +11,21 @@ import (
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"github.com/miekg/dns"
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)
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// Those constants are used to distinguish between records in ExternalServices headless
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// return values.
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// They are always appendedn to key in a map which is
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// either base service key eg. /com/example/namespace/service/endpoint or
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// /com/example/namespace/service/_http/_tcp/port.protocol
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// this will allow us to distinguish services in implementation of Transfer protocol
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// see plugin/k8s_external/transfer.go
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const (
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Endpoint = "endpoint"
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PortProtocol = "port.protocol"
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)
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// External implements the ExternalFunc call from the external plugin.
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// It returns any services matching in the services' ExternalIPs.
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func (k *Kubernetes) External(state request.Request) ([]msg.Service, int) {
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// It returns any services matching in the services' ExternalIPs and if enabled, headless endpoints..
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func (k *Kubernetes) External(state request.Request, headless bool) ([]msg.Service, int) {
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if state.QType() == dns.TypePTR {
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ip := dnsutil.ExtractAddressFromReverse(state.Name())
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if ip != "" {
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@ -33,10 +45,11 @@ func (k *Kubernetes) External(state request.Request) ([]msg.Service, int) {
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if last < 0 {
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return nil, dns.RcodeServerFailure
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}
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// We are dealing with a fairly normal domain name here, but we still need to have the service
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// and the namespace:
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// service.namespace.<base>
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var port, protocol string
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// We are dealing with a fairly normal domain name here, but we still need to have the service,
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// namespace and if present, endpoint:
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// service.namespace.<base> or
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// endpoint.service.namespace.<base>
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var port, protocol, endpoint string
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namespace := segs[last]
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if !k.namespaceExposed(namespace) {
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return nil, dns.RcodeNameError
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@ -49,7 +62,10 @@ func (k *Kubernetes) External(state request.Request) ([]msg.Service, int) {
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service := segs[last]
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last--
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if last == 1 {
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if last == 0 {
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endpoint = stripUnderscore(segs[last])
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last--
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} else if last == 1 {
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protocol = stripUnderscore(segs[last])
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port = stripUnderscore(segs[last-1])
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last -= 2
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@ -60,8 +76,13 @@ func (k *Kubernetes) External(state request.Request) ([]msg.Service, int) {
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return nil, dns.RcodeNameError
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}
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var (
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endpointsList []*object.Endpoints
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serviceList []*object.Service
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)
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idx := object.ServiceKey(service, namespace)
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serviceList := k.APIConn.SvcIndex(idx)
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serviceList = k.APIConn.SvcIndex(idx)
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services := []msg.Service{}
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zonePath := msg.Path(state.Zone, coredns)
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@ -75,16 +96,47 @@ func (k *Kubernetes) External(state request.Request) ([]msg.Service, int) {
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continue
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}
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for _, ip := range svc.ExternalIPs {
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for _, p := range svc.Ports {
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if !(matchPortAndProtocol(port, p.Name, protocol, string(p.Protocol))) {
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if headless && len(svc.ExternalIPs) == 0 && (svc.Headless() || endpoint != "") {
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if endpointsList == nil {
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endpointsList = k.APIConn.EpIndex(idx)
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}
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// Endpoint query or headless service
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for _, ep := range endpointsList {
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if object.EndpointsKey(svc.Name, svc.Namespace) != ep.Index {
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continue
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}
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rcode = dns.RcodeSuccess
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s := msg.Service{Host: ip, Port: int(p.Port), TTL: k.ttl}
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s.Key = strings.Join([]string{zonePath, svc.Namespace, svc.Name}, "/")
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services = append(services, s)
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for _, eps := range ep.Subsets {
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for _, addr := range eps.Addresses {
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if endpoint != "" && !match(endpoint, endpointHostname(addr, k.endpointNameMode)) {
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continue
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}
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for _, p := range eps.Ports {
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if !(matchPortAndProtocol(port, p.Name, protocol, p.Protocol)) {
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continue
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}
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s := msg.Service{Host: addr.IP, Port: int(p.Port), TTL: k.ttl}
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s.Key = strings.Join([]string{zonePath, svc.Namespace, svc.Name, endpointHostname(addr, k.endpointNameMode)}, "/")
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services = append(services, s)
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}
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}
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}
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}
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continue
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} else {
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for _, ip := range svc.ExternalIPs {
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for _, p := range svc.Ports {
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if !(matchPortAndProtocol(port, p.Name, protocol, string(p.Protocol))) {
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continue
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}
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rcode = dns.RcodeSuccess
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s := msg.Service{Host: ip, Port: int(p.Port), TTL: k.ttl}
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s.Key = strings.Join([]string{zonePath, svc.Namespace, svc.Name}, "/")
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services = append(services, s)
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}
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}
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}
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}
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@ -96,31 +148,65 @@ func (k *Kubernetes) External(state request.Request) ([]msg.Service, int) {
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}
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// ExternalAddress returns the external service address(es) for the CoreDNS service.
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func (k *Kubernetes) ExternalAddress(state request.Request) []dns.RR {
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func (k *Kubernetes) ExternalAddress(state request.Request, headless bool) []dns.RR {
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// If CoreDNS is running inside the Kubernetes cluster: k.nsAddrs() will return the external IPs of the services
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// targeting the CoreDNS Pod.
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// If CoreDNS is running outside of the Kubernetes cluster: k.nsAddrs() will return the first non-loopback IP
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// address seen on the local system it is running on. This could be the wrong answer if coredns is using the *bind*
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// plugin to bind to a different IP address.
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return k.nsAddrs(true, state.Zone)
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return k.nsAddrs(true, headless, state.Zone)
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}
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// ExternalServices returns all services with external IPs
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func (k *Kubernetes) ExternalServices(zone string) (services []msg.Service) {
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// ExternalServices returns all services with external IPs and if enabled headless services
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func (k *Kubernetes) ExternalServices(zone string, headless bool) (services []msg.Service, headlessServices map[string][]msg.Service) {
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zonePath := msg.Path(zone, coredns)
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headlessServices = make(map[string][]msg.Service)
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for _, svc := range k.APIConn.ServiceList() {
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for _, ip := range svc.ExternalIPs {
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for _, p := range svc.Ports {
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s := msg.Service{Host: ip, Port: int(p.Port), TTL: k.ttl}
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s.Key = strings.Join([]string{zonePath, svc.Namespace, svc.Name}, "/")
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services = append(services, s)
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s.Key = strings.Join(append([]string{zonePath, svc.Namespace, svc.Name}, strings.ToLower("_"+string(p.Protocol)), strings.ToLower("_"+string(p.Name))), "/")
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s.TargetStrip = 2
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services = append(services, s)
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// Endpoints and headless services
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if headless && len(svc.ExternalIPs) == 0 && svc.Headless() {
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idx := object.ServiceKey(svc.Name, svc.Namespace)
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endpointsList := k.APIConn.EpIndex(idx)
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for _, ep := range endpointsList {
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for _, eps := range ep.Subsets {
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for _, addr := range eps.Addresses {
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// we need to have some answers grouped together
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// 1. for endpoint requests eg. endpoint-0.service.example.com - will always have one endpoint
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// 2. for service requests eg. service.example.com - can have multiple endpoints
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// 3. for port.protocol requests eg. _http._tcp.service.example.com - can have multiple endpoints
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for _, p := range eps.Ports {
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s := msg.Service{Host: addr.IP, Port: int(p.Port), TTL: k.ttl}
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baseSvc := strings.Join([]string{zonePath, svc.Namespace, svc.Name}, "/")
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s.Key = strings.Join([]string{baseSvc, endpointHostname(addr, k.endpointNameMode)}, "/")
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headlessServices[strings.Join([]string{baseSvc, Endpoint}, "/")] = append(headlessServices[strings.Join([]string{baseSvc, Endpoint}, "/")], s)
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// As per spec unnamed ports do not have a srv record
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// https://github.com/kubernetes/dns/blob/master/docs/specification.md#232---srv-records
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if p.Name == "" {
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continue
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}
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s.Host = msg.Domain(s.Key)
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s.Key = strings.Join(append([]string{zonePath, svc.Namespace, svc.Name}, strings.ToLower("_"+string(p.Protocol)), strings.ToLower("_"+string(p.Name))), "/")
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headlessServices[strings.Join([]string{s.Key, PortProtocol}, "/")] = append(headlessServices[strings.Join([]string{s.Key, PortProtocol}, "/")], s)
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}
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}
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}
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}
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continue
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} else {
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for _, ip := range svc.ExternalIPs {
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for _, p := range svc.Ports {
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s := msg.Service{Host: ip, Port: int(p.Port), TTL: k.ttl}
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s.Key = strings.Join([]string{zonePath, svc.Namespace, svc.Name}, "/")
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services = append(services, s)
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s.Key = strings.Join(append([]string{zonePath, svc.Namespace, svc.Name}, strings.ToLower("_"+string(p.Protocol)), strings.ToLower("_"+string(p.Name))), "/")
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s.TargetStrip = 2
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services = append(services, s)
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}
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}
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}
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}
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return services
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return services, headlessServices
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}
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//ExternalSerial returns the serial of the external zone
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