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78db9fbb10
SOA would blindly add "." + zone, which when using the root zone would create a unparseable packet with "name.."
468 lines
13 KiB
Go
468 lines
13 KiB
Go
package middleware
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import (
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"fmt"
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"math"
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"net"
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"time"
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"github.com/coredns/coredns/middleware/etcd/msg"
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"github.com/coredns/coredns/middleware/pkg/dnsutil"
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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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// A returns A records from Backend or an error.
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func A(b ServiceBackend, zone string, state request.Request, previousRecords []dns.RR, opt Options) (records []dns.RR, debug []msg.Service, err error) {
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services, debug, err := b.Services(state, false, opt)
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if err != nil {
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return nil, debug, err
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}
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for _, serv := range services {
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what, ip := serv.HostType()
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switch what {
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case dns.TypeCNAME:
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if Name(state.Name()).Matches(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 dnsutil.DuplicateCNAME(newRecord, previousRecords) {
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continue
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}
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state1 := state.NewWithQuestion(serv.Host, state.QType())
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nextRecords, nextDebug, err := A(b, zone, state1, append(previousRecords, newRecord), opt)
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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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records = append(records, newRecord)
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records = append(records, nextRecords...)
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debug = append(debug, nextDebug...)
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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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// Lookup
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m1, e1 := b.Lookup(state, target, state.QType())
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if e1 != nil {
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debugMsg := msg.Service{Key: msg.Path(target, b.Debug()), Host: target, Text: " IN " + state.Type() + ": " + e1.Error()}
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debug = append(debug, debugMsg)
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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 dns.TypeA:
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records = append(records, serv.NewA(state.QName(), ip))
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case dns.TypeAAAA:
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// nodata?
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}
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}
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return records, debug, nil
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}
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// AAAA returns AAAA records from Backend or an error.
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func AAAA(b ServiceBackend, zone string, state request.Request, previousRecords []dns.RR, opt Options) (records []dns.RR, debug []msg.Service, err error) {
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services, debug, err := b.Services(state, false, opt)
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if err != nil {
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return nil, debug, err
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}
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for _, serv := range services {
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what, ip := serv.HostType()
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switch what {
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case dns.TypeCNAME:
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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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if Name(state.Name()).Matches(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 dnsutil.DuplicateCNAME(newRecord, previousRecords) {
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continue
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}
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state1 := state.NewWithQuestion(serv.Host, state.QType())
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nextRecords, nextDebug, err := AAAA(b, zone, state1, append(previousRecords, newRecord), opt)
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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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records = append(records, newRecord)
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records = append(records, nextRecords...)
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debug = append(debug, nextDebug...)
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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 := b.Lookup(state, target, state.QType())
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if e1 != nil {
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debugMsg := msg.Service{Key: msg.Path(target, b.Debug()), Host: target, Text: " IN " + state.Type() + ": " + e1.Error()}
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debug = append(debug, debugMsg)
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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 dns.TypeA:
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// nada?
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case dns.TypeAAAA:
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records = append(records, serv.NewAAAA(state.QName(), ip))
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}
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}
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return records, debug, nil
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}
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// SRV returns SRV records from the Backend.
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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 SRV(b ServiceBackend, zone string, state request.Request, opt Options) (records, extra []dns.RR, debug []msg.Service, err error) {
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services, debug, err := b.Services(state, false, opt)
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if err != nil {
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return nil, nil, nil, err
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}
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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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what, ip := serv.HostType()
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switch what {
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case dns.TypeCNAME:
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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 := b.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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} else {
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debugMsg := msg.Service{Key: msg.Path(srv.Target, b.Debug()), Host: srv.Target, Text: " IN A: " + e1.Error()}
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debug = append(debug, debugMsg)
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}
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m1, e1 = b.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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} else {
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debugMsg := msg.Service{Key: msg.Path(srv.Target, b.Debug()), Host: srv.Target, Text: " IN AAAA: " + e1.Error()}
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debug = append(debug, debugMsg)
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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 view.
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state1 := state.NewWithQuestion(srv.Target, dns.TypeA)
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addr, debugAddr, e1 := A(b, zone, state1, nil, Options(opt))
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if e1 == nil {
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extra = append(extra, addr...)
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debug = append(debug, debugAddr...)
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}
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// IPv6 lookups here as well? AAAA(zone, state1, nil).
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case dns.TypeA, dns.TypeAAAA:
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serv.Host = msg.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, newAddress(serv, srv.Target, ip, what))
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}
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}
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return records, extra, debug, nil
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}
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// MX returns MX records from the Backend. If the Target is not a name but an IP address, a name is created on the fly.
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func MX(b ServiceBackend, zone string, state request.Request, opt Options) (records, extra []dns.RR, debug []msg.Service, err error) {
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services, debug, err := b.Services(state, false, opt)
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if err != nil {
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return nil, nil, debug, 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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what, ip := serv.HostType()
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switch what {
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case dns.TypeCNAME:
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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 := b.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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} else {
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debugMsg := msg.Service{Key: msg.Path(mx.Mx, b.Debug()), Host: mx.Mx, Text: " IN A: " + e1.Error()}
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debug = append(debug, debugMsg)
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}
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m1, e1 = b.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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} else {
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debugMsg := msg.Service{Key: msg.Path(mx.Mx, b.Debug()), Host: mx.Mx, Text: " IN AAAA: " + e1.Error()}
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debug = append(debug, debugMsg)
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}
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break
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}
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// Internal name
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state1 := state.NewWithQuestion(mx.Mx, dns.TypeA)
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addr, debugAddr, e1 := A(b, zone, state1, nil, opt)
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if e1 == nil {
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extra = append(extra, addr...)
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debug = append(debug, debugAddr...)
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}
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// e.AAAA as well
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case dns.TypeA, dns.TypeAAAA:
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serv.Host = msg.Domain(serv.Key)
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records = append(records, serv.NewMX(state.QName()))
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extra = append(extra, newAddress(serv, serv.Host, ip, what))
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}
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}
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return records, extra, debug, nil
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}
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// CNAME returns CNAME records from the backend or an error.
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func CNAME(b ServiceBackend, zone string, state request.Request, opt Options) (records []dns.RR, debug []msg.Service, err error) {
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services, debug, err := b.Services(state, true, opt)
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if err != nil {
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return nil, debug, err
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}
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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, debug, nil
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}
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// TXT returns TXT records from Backend or an error.
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func TXT(b ServiceBackend, zone string, state request.Request, opt Options) (records []dns.RR, debug []msg.Service, err error) {
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services, debug, err := b.Services(state, false, opt)
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if err != nil {
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return nil, debug, err
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}
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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, debug, nil
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}
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// PTR returns the PTR records from the backend, only services that have a domain name as host are included.
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func PTR(b ServiceBackend, zone string, state request.Request, opt Options) (records []dns.RR, debug []msg.Service, err error) {
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services, debug, err := b.Reverse(state, true, opt)
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if err != nil {
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return nil, debug, err
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}
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for _, serv := range services {
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if ip := net.ParseIP(serv.Host); ip == nil {
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records = append(records, serv.NewPTR(state.QName(), serv.Host))
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}
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}
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return records, debug, nil
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}
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// NS returns NS records from the backend
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func NS(b ServiceBackend, zone string, state request.Request, opt Options) (records, extra []dns.RR, debug []msg.Service, err error) {
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// NS record for this zone live in a special place, ns.dns.<zone>. Fake our lookup.
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// only a tad bit fishy...
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old := state.QName()
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state.Clear()
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state.Req.Question[0].Name = "ns.dns." + zone
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services, debug, err := b.Services(state, false, opt)
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if err != nil {
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return nil, nil, debug, err
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}
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// ... and reset
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state.Req.Question[0].Name = old
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for _, serv := range services {
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what, ip := serv.HostType()
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switch what {
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case dns.TypeCNAME:
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return nil, nil, debug, fmt.Errorf("NS record must be an IP address: %s", serv.Host)
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case dns.TypeA, dns.TypeAAAA:
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serv.Host = msg.Domain(serv.Key)
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records = append(records, serv.NewNS(state.QName()))
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extra = append(extra, newAddress(serv, serv.Host, ip, what))
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}
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}
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return records, extra, debug, nil
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}
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// SOA returns a SOA record from the backend.
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func SOA(b ServiceBackend, zone string, state request.Request, opt Options) ([]dns.RR, []msg.Service, error) {
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header := dns.RR_Header{Name: zone, Rrtype: dns.TypeSOA, Ttl: 300, Class: dns.ClassINET}
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Mbox := hostmaster + "."
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Ns := "ns.dns."
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if zone[0] != '.' {
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Mbox += zone
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Ns += zone
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}
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soa := &dns.SOA{Hdr: header,
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Mbox: Mbox,
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Ns: Ns,
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Serial: uint32(time.Now().Unix()),
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Refresh: 7200,
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Retry: 1800,
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Expire: 86400,
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Minttl: minTTL,
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}
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return []dns.RR{soa}, nil, nil
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}
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// BackendError writes an error response to the client.
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func BackendError(b ServiceBackend, zone string, rcode int, state request.Request, debug []msg.Service, err error, opt Options) (int, error) {
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m := new(dns.Msg)
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m.SetRcode(state.Req, rcode)
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m.Authoritative, m.RecursionAvailable, m.Compress = true, true, true
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m.Ns, _, _ = SOA(b, zone, state, opt)
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if opt.Debug != "" {
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m.Extra = ServicesToTxt(debug)
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txt := ErrorToTxt(err)
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if txt != nil {
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m.Extra = append(m.Extra, ErrorToTxt(err))
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}
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}
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state.SizeAndDo(m)
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state.W.WriteMsg(m)
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// Return success as the rcode to signal we have written to the client.
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return dns.RcodeSuccess, err
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}
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// ServicesToTxt puts debug in TXT RRs.
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func ServicesToTxt(debug []msg.Service) []dns.RR {
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if debug == nil {
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return nil
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}
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rr := make([]dns.RR, len(debug))
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for i, d := range debug {
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rr[i] = d.RR()
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}
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return rr
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}
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// ErrorToTxt puts in error's text into an TXT RR.
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func ErrorToTxt(err error) dns.RR {
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if err == nil {
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return nil
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}
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msg := err.Error()
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if len(msg) > 255 {
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msg = msg[:255]
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}
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t := new(dns.TXT)
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t.Hdr.Class = dns.ClassCHAOS
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t.Hdr.Ttl = 0
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t.Hdr.Rrtype = dns.TypeTXT
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t.Hdr.Name = "."
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t.Txt = []string{msg}
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return t
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}
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func newAddress(s msg.Service, name string, ip net.IP, what uint16) dns.RR {
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hdr := dns.RR_Header{Name: name, Rrtype: what, Class: dns.ClassINET, Ttl: s.TTL}
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if what == dns.TypeA {
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return &dns.A{Hdr: hdr, A: ip}
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}
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// Should always be dns.TypeAAAA
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return &dns.AAAA{Hdr: hdr, AAAA: ip}
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}
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const (
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minTTL = 60
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hostmaster = "hostmaster"
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)
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