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https://github.com/coredns/coredns.git
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Add etcd middleware
This middleware acts in the same way as SkyDNS. We might add options
to allow it to be behave different, but for now it will suffice.
A Corefile like:
.:1053 {
etcd miek.nl
proxy . 8.8.8.8:53
}
will perform lookup in etcd and proxy everything not miek.nl to Google
for further resolution.
The internal etcd forwarding *also* uses the proxy infrastructure,
meaning you get health check and such for (almost) free
This commit is contained in:
Miek Gieben
344
middleware/etcd/lookup.go
Normal file
344
middleware/etcd/lookup.go
Normal file
@@ -0,0 +1,344 @@
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package etcd
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import (
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"math"
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"net"
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"github.com/miekg/coredns/middleware"
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"github.com/miekg/coredns/middleware/etcd/msg"
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"github.com/miekg/dns"
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)
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// TODO(miek): factor out common code a bit
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func (e Etcd) A(zone string, state middleware.State, previousRecords []dns.RR) (records []dns.RR, err error) {
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services, err := e.Records(state.Name(), false)
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if err != nil {
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return nil, err
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}
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services = msg.Group(services)
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for _, serv := range services {
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ip := net.ParseIP(serv.Host)
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switch {
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case ip == nil:
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// Try to resolve as CNAME if it's not an IP, but only if we don't create loops.
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// TODO(miek): lowercasing, use Match in middleware?
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if state.Name() == dns.Fqdn(serv.Host) {
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// x CNAME x is a direct loop, don't add those
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continue
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}
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newRecord := serv.NewCNAME(state.QName(), serv.Host)
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if len(previousRecords) > 7 {
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// don't add it, and just continue
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continue
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}
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if isDuplicateCNAME(newRecord, previousRecords) {
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continue
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}
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state1 := copyState(state, serv.Host, state.QType())
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nextRecords, err := e.A(zone, state1, append(previousRecords, newRecord))
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if err == nil {
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// Not only have we found something we should add the CNAME and the IP addresses.
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if len(nextRecords) > 0 {
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// TODO(miek): sorting here?
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records = append(records, newRecord)
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records = append(records, nextRecords...)
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}
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continue
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}
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// This means we can not complete the CNAME, try to look else where.
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target := newRecord.Target
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if dns.IsSubDomain(zone, target) {
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// We should already have found it
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continue
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}
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m1, e1 := e.Proxy.Lookup(state, target, state.QType())
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if e1 != nil {
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continue
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}
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// Len(m1.Answer) > 0 here is well?
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records = append(records, newRecord)
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records = append(records, m1.Answer...)
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continue
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case ip.To4() != nil:
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records = append(records, serv.NewA(state.QName(), ip.To4()))
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case ip.To4() == nil:
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// noda?
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}
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}
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return records, nil
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}
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func (e Etcd) AAAA(zone string, state middleware.State, previousRecords []dns.RR) (records []dns.RR, err error) {
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services, err := e.Records(state.Name(), false)
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if err != nil {
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return nil, err
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}
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services = msg.Group(services)
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for _, serv := range services {
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ip := net.ParseIP(serv.Host)
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switch {
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case ip == nil:
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// Try to resolve as CNAME if it's not an IP, but only if we don't create loops.
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// TODO(miek): lowercasing, use Match in middleware/
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if state.Name() == dns.Fqdn(serv.Host) {
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// x CNAME x is a direct loop, don't add those
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continue
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}
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newRecord := serv.NewCNAME(state.QName(), serv.Host)
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if len(previousRecords) > 7 {
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// don't add it, and just continue
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continue
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}
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if isDuplicateCNAME(newRecord, previousRecords) {
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continue
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}
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state1 := copyState(state, serv.Host, state.QType())
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nextRecords, err := e.AAAA(zone, state1, append(previousRecords, newRecord))
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if err == nil {
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// Not only have we found something we should add the CNAME and the IP addresses.
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if len(nextRecords) > 0 {
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// TODO(miek): sorting here?
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records = append(records, newRecord)
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records = append(records, nextRecords...)
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}
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continue
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}
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// This means we can not complete the CNAME, try to look else where.
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target := newRecord.Target
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if dns.IsSubDomain(zone, target) {
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// We should already have found it
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continue
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}
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m1, e1 := e.Proxy.Lookup(state, target, state.QType())
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if e1 != nil {
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continue
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}
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// Len(m1.Answer) > 0 here is well?
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records = append(records, newRecord)
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records = append(records, m1.Answer...)
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continue
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// both here again
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case ip.To4() != nil:
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// nada?
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case ip.To4() == nil:
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records = append(records, serv.NewAAAA(state.QName(), ip.To16()))
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}
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}
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return records, nil
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}
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// SRV returns SRV records from etcd.
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// If the Target is not a name but an IP address, a name is created on the fly.
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func (e Etcd) SRV(zone string, state middleware.State) (records []dns.RR, extra []dns.RR, err error) {
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services, err := e.Records(state.Name(), false)
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if err != nil {
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return nil, nil, err
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}
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services = msg.Group(services)
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// Looping twice to get the right weight vs priority
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w := make(map[int]int)
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for _, serv := range services {
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weight := 100
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if serv.Weight != 0 {
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weight = serv.Weight
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}
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if _, ok := w[serv.Priority]; !ok {
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w[serv.Priority] = weight
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continue
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}
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w[serv.Priority] += weight
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}
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lookup := make(map[string]bool)
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for _, serv := range services {
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w1 := 100.0 / float64(w[serv.Priority])
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if serv.Weight == 0 {
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w1 *= 100
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} else {
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w1 *= float64(serv.Weight)
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}
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weight := uint16(math.Floor(w1))
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ip := net.ParseIP(serv.Host)
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switch {
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case ip == nil:
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srv := serv.NewSRV(state.QName(), weight)
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records = append(records, srv)
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if _, ok := lookup[srv.Target]; ok {
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break
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}
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lookup[srv.Target] = true
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if !dns.IsSubDomain(zone, srv.Target) {
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m1, e1 := e.Proxy.Lookup(state, srv.Target, dns.TypeA)
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if e1 == nil {
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extra = append(extra, m1.Answer...)
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}
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m1, e1 = e.Proxy.Lookup(state, srv.Target, dns.TypeAAAA)
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if e1 == nil {
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// If we have seen CNAME's we *assume* that they are already added.
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for _, a := range m1.Answer {
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if _, ok := a.(*dns.CNAME); !ok {
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extra = append(extra, a)
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}
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}
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}
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break
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}
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// Internal name, we should have some info on them, either v4 or v6
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// Clients expect a complete answer, because we are a recursor in their
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// view.
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state1 := copyState(state, srv.Target, dns.TypeA)
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// TODO(both is true here!
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addr, e1 := e.A(zone, state1, nil)
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if e1 == nil {
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extra = append(extra, addr...)
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}
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// e.AAA(zone, state1, nil) as well...
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case ip.To4() != nil:
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serv.Host = e.Domain(serv.Key)
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srv := serv.NewSRV(state.QName(), weight)
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records = append(records, srv)
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extra = append(extra, serv.NewA(srv.Target, ip.To4()))
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case ip.To4() == nil:
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serv.Host = e.Domain(serv.Key)
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srv := serv.NewSRV(state.QName(), weight)
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records = append(records, srv)
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extra = append(extra, serv.NewAAAA(srv.Target, ip.To16()))
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}
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}
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return records, extra, nil
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}
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// MX returns MX records from etcd.
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// If the Target is not a name but an IP address, a name is created on the fly.
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func (e Etcd) MX(zone string, state middleware.State) (records []dns.RR, extra []dns.RR, err error) {
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services, err := e.Records(state.Name(), false)
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if err != nil {
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return nil, nil, err
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}
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lookup := make(map[string]bool)
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for _, serv := range services {
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if !serv.Mail {
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continue
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}
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ip := net.ParseIP(serv.Host)
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switch {
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case ip == nil:
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mx := serv.NewMX(state.QName())
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records = append(records, mx)
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if _, ok := lookup[mx.Mx]; ok {
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break
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}
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lookup[mx.Mx] = true
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if !dns.IsSubDomain(zone, mx.Mx) {
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m1, e1 := e.Proxy.Lookup(state, mx.Mx, dns.TypeA)
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if e1 == nil {
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extra = append(extra, m1.Answer...)
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}
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m1, e1 = e.Proxy.Lookup(state, mx.Mx, dns.TypeAAAA)
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if e1 == nil {
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// If we have seen CNAME's we *assume* that they are already added.
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for _, a := range m1.Answer {
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if _, ok := a.(*dns.CNAME); !ok {
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extra = append(extra, a)
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}
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}
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}
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break
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}
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// Internal name
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// both is true here as well
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state1 := copyState(state, mx.Mx, dns.TypeA)
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addr, e1 := e.A(zone, state1, nil)
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if e1 == nil {
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extra = append(extra, addr...)
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}
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// e.AAAA as well
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case ip.To4() != nil:
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serv.Host = e.Domain(serv.Key)
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records = append(records, serv.NewMX(state.QName()))
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extra = append(extra, serv.NewA(serv.Host, ip.To4()))
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case ip.To4() == nil:
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serv.Host = e.Domain(serv.Key)
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records = append(records, serv.NewMX(state.QName()))
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extra = append(extra, serv.NewAAAA(serv.Host, ip.To16()))
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}
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}
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return records, extra, nil
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}
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func (e Etcd) CNAME(zone string, state middleware.State) (records []dns.RR, err error) {
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services, err := e.Records(state.Name(), true)
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if err != nil {
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return nil, err
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}
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services = msg.Group(services)
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if len(services) > 0 {
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serv := services[0]
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if ip := net.ParseIP(serv.Host); ip == nil {
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records = append(records, serv.NewCNAME(state.QName(), serv.Host))
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}
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}
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return records, nil
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}
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func (e Etcd) TXT(zone string, state middleware.State) (records []dns.RR, err error) {
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services, err := e.Records(state.Name(), false)
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if err != nil {
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return nil, err
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}
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services = msg.Group(services)
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for _, serv := range services {
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if serv.Text == "" {
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continue
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}
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records = append(records, serv.NewTXT(state.QName()))
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}
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return records, nil
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}
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// synthesis a SOA Record.
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func SOA(zone string) *dns.SOA {
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return &dns.SOA{}
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}
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func isDuplicateCNAME(r *dns.CNAME, records []dns.RR) bool {
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for _, rec := range records {
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if v, ok := rec.(*dns.CNAME); ok {
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if v.Target == r.Target {
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return true
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}
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}
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}
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return false
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}
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func copyState(state middleware.State, target string, typ uint16) middleware.State {
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state1 := state
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state1.Req.Question[0] = dns.Question{dns.Fqdn(target), dns.ClassINET, typ}
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return state1
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}
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