c1c98924c3
* Add new plugin: external This plugin works in conjunction with the kubernetes plugin and exports ingress and LB addresses as DNS records. It bypasses backend.go and backend_lookup.go flow because it is not needed. README, tests are implemented. The tests only exercise the unit tests, this has not been tested in any ci. Signed-off-by: Miek Gieben <miek@miek.nl> * Rename to k8s_external Signed-off-by: Miek Gieben <miek@miek.nl> * go gen Signed-off-by: Miek Gieben <miek@miek.nl>
112 lines
2.9 KiB
Go
112 lines
2.9 KiB
Go
/*
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Package external implements external names for kubernetes clusters.
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This plugin only handles three qtypes (except the apex queries, because those are handled
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differently). We support A, AAAA and SRV request, for all other types we return NODATA or
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NXDOMAIN depending on the state of the cluster.
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A plugin willing to provide these services must implement the Externaler interface, although it
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likely only makes sense for the *kubernetes* plugin.
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*/
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package external
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import (
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"context"
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"github.com/coredns/coredns/plugin"
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"github.com/coredns/coredns/plugin/etcd/msg"
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"github.com/coredns/coredns/request"
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"github.com/miekg/dns"
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)
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// Externaler defines the interface that a plugin should implement in order to be used by External.
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type Externaler interface {
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// External returns a slice of msg.Services that are looked up in the backend and match
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// the request.
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External(request.Request) ([]msg.Service, int)
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// ExternalAddress should return a string slice of addresses for the nameserving endpoint.
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ExternalAddress(state request.Request) []dns.RR
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}
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// External resolves Ingress and Loadbalance IPs from kubernetes clusters.
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type External struct {
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Next plugin.Handler
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Zones []string
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hostmaster string
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apex string
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ttl uint32
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externalFunc func(request.Request) ([]msg.Service, int)
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externalAddrFunc func(request.Request) []dns.RR
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}
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// New returns a new and initialized *External.
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func New() *External {
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e := &External{hostmaster: "hostmaster", ttl: 5, apex: "dns"}
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return e
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}
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// ServeDNS implements the plugin.Handle interface.
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func (e *External) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
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state := request.Request{W: w, Req: r}
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zone := plugin.Zones(e.Zones).Matches(state.Name())
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if zone == "" {
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return plugin.NextOrFailure(e.Name(), e.Next, ctx, w, r)
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}
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if e.externalFunc == nil {
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return plugin.NextOrFailure(e.Name(), e.Next, ctx, w, r)
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}
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state.Zone = zone
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for _, z := range e.Zones {
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// TODO(miek): save this in the External struct.
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if state.Name() == z { // apex query
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ret, err := e.serveApex(state)
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return ret, err
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}
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if dns.IsSubDomain(e.apex+"."+z, state.Name()) {
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// dns subdomain test for ns. and dns. queries
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ret, err := e.serveSubApex(state)
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return ret, err
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}
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}
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svc, rcode := e.externalFunc(state)
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m := new(dns.Msg)
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m.SetReply(state.Req)
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if len(svc) == 0 {
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m.Rcode = rcode
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m.Ns = []dns.RR{e.soa(state)}
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w.WriteMsg(m)
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return 0, nil
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}
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switch state.QType() {
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case dns.TypeA:
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m.Answer = e.a(svc, state)
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case dns.TypeAAAA:
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m.Answer = e.aaaa(svc, state)
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case dns.TypeSRV:
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m.Answer, m.Extra = e.srv(svc, state)
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default:
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m.Ns = []dns.RR{e.soa(state)}
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}
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// If we did have records, but queried for the wrong qtype return a nodata response.
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if len(m.Answer) == 0 {
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m.Ns = []dns.RR{e.soa(state)}
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}
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w.WriteMsg(m)
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return 0, nil
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}
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// Name implements the Handler interface.
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func (e *External) Name() string { return "k8s_external" }
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