mirror of
https://github.com/coredns/coredns.git
synced 2025-11-03 10:43:20 -05:00
e3266d24f7
* Add test case for TXT lookup via CNAME Signed-off-by: Jonathan Nagy <nagytech@users.noreply.github.com> * Return HostType of explicit TXT records Signed-off-by: Jonathan Nagy <nagytech@users.noreply.github.com> * Adapt TXT method lookup to allow lookup via CNAME Signed-off-by: Jonathan Nagy <nagytech@users.noreply.github.com> * Implement lookup of TXT records via CNAME Signed-off-by: Jonathan Nagy <nagytech@users.noreply.github.com>
550 lines
15 KiB
Go
550 lines
15 KiB
Go
package plugin
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import (
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"context"
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"fmt"
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"math"
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"net"
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"github.com/coredns/coredns/plugin/etcd/msg"
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"github.com/coredns/coredns/plugin/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(ctx context.Context, b ServiceBackend, zone string, state request.Request, previousRecords []dns.RR, opt Options) (records []dns.RR, err error) {
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services, err := checkForApex(ctx, b, zone, state, opt)
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if err != nil {
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return nil, err
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}
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dup := make(map[string]struct{})
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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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if dns.IsSubDomain(zone, dns.Fqdn(serv.Host)) {
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state1 := state.NewWithQuestion(serv.Host, state.QType())
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state1.Zone = zone
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nextRecords, err := A(ctx, 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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}
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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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// Lookup
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m1, e1 := b.Lookup(ctx, 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 dns.TypeA:
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if _, ok := dup[serv.Host]; !ok {
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dup[serv.Host] = struct{}{}
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records = append(records, serv.NewA(state.QName(), ip))
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}
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case dns.TypeAAAA:
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// nada
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}
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}
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return records, nil
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}
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// AAAA returns AAAA records from Backend or an error.
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func AAAA(ctx context.Context, b ServiceBackend, zone string, state request.Request, previousRecords []dns.RR, opt Options) (records []dns.RR, err error) {
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services, err := checkForApex(ctx, b, zone, state, opt)
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if err != nil {
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return nil, err
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}
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dup := make(map[string]struct{})
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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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if dns.IsSubDomain(zone, dns.Fqdn(serv.Host)) {
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state1 := state.NewWithQuestion(serv.Host, state.QType())
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state1.Zone = zone
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nextRecords, err := AAAA(ctx, 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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}
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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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m1, e1 := b.Lookup(ctx, 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 dns.TypeA:
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// nada
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case dns.TypeAAAA:
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if _, ok := dup[serv.Host]; !ok {
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dup[serv.Host] = struct{}{}
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records = append(records, serv.NewAAAA(state.QName(), ip))
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}
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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 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(ctx context.Context, b ServiceBackend, zone string, state request.Request, opt Options) (records, extra []dns.RR, err error) {
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services, err := b.Services(ctx, state, false, opt)
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if err != nil {
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return nil, nil, err
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}
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dup := make(map[item]struct{})
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lookup := make(map[string]struct{})
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// Looping twice to get the right weight vs priority. This might break because we may drop duplicate SRV records latter on.
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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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for _, serv := range services {
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// Don't add the entry if the port is -1 (invalid). The kubernetes plugin uses port -1 when a service/endpoint
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// does not have any declared ports.
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if serv.Port == -1 {
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continue
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}
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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] = struct{}{}
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if !dns.IsSubDomain(zone, srv.Target) {
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m1, e1 := b.Lookup(ctx, 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 = b.Lookup(ctx, 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 view.
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state1 := state.NewWithQuestion(srv.Target, dns.TypeA)
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addr, e1 := A(ctx, b, zone, state1, nil, opt)
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if e1 == nil {
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extra = append(extra, addr...)
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}
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// TODO(miek): AAAA as well here.
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case dns.TypeA, dns.TypeAAAA:
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addr := serv.Host
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serv.Host = msg.Domain(serv.Key)
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srv := serv.NewSRV(state.QName(), weight)
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if ok := isDuplicate(dup, srv.Target, "", srv.Port); !ok {
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records = append(records, srv)
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}
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if ok := isDuplicate(dup, srv.Target, addr, 0); !ok {
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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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}
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return records, extra, 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(ctx context.Context, b ServiceBackend, zone string, state request.Request, opt Options) (records, extra []dns.RR, err error) {
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services, err := b.Services(ctx, state, false, opt)
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if err != nil {
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return nil, nil, err
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}
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dup := make(map[item]struct{})
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lookup := make(map[string]struct{})
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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] = struct{}{}
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if !dns.IsSubDomain(zone, mx.Mx) {
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m1, e1 := b.Lookup(ctx, 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 = b.Lookup(ctx, 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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state1 := state.NewWithQuestion(mx.Mx, dns.TypeA)
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addr, e1 := A(ctx, b, zone, state1, nil, opt)
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if e1 == nil {
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extra = append(extra, addr...)
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}
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// TODO(miek): AAAA as well here.
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case dns.TypeA, dns.TypeAAAA:
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addr := serv.Host
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serv.Host = msg.Domain(serv.Key)
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mx := serv.NewMX(state.QName())
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if ok := isDuplicate(dup, mx.Mx, "", mx.Preference); !ok {
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records = append(records, mx)
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}
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// Fake port to be 0 for address...
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if ok := isDuplicate(dup, serv.Host, addr, 0); !ok {
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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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}
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return records, extra, 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(ctx context.Context, b ServiceBackend, zone string, state request.Request, opt Options) (records []dns.RR, err error) {
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services, err := b.Services(ctx, state, true, opt)
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if err != nil {
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return nil, 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, nil
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}
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// TXT returns TXT records from Backend or an error.
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func TXT(ctx context.Context, b ServiceBackend, zone string, state request.Request, previousRecords []dns.RR, opt Options) (records []dns.RR, err error) {
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services, err := b.Services(ctx, state, true, opt)
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if err != nil {
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return nil, err
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}
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dup := make(map[string]struct{})
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for _, serv := range services {
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what, _ := 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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if dns.IsSubDomain(zone, dns.Fqdn(serv.Host)) {
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state1 := state.NewWithQuestion(serv.Host, state.QType())
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state1.Zone = zone
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nextRecords, err := TXT(ctx, 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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}
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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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// Lookup
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m1, e1 := b.Lookup(ctx, 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 dns.TypeTXT:
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if _, ok := dup[serv.Host]; !ok {
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dup[serv.Host] = struct{}{}
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return append(records, serv.NewTXT(state.QName())), nil
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}
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}
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}
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return records, 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(ctx context.Context, b ServiceBackend, zone string, state request.Request, opt Options) (records []dns.RR, err error) {
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services, err := b.Reverse(ctx, state, true, opt)
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if err != nil {
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return nil, err
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}
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dup := make(map[string]struct{})
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for _, serv := range services {
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if ip := net.ParseIP(serv.Host); ip == nil {
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if _, ok := dup[serv.Host]; !ok {
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dup[serv.Host] = struct{}{}
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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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}
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return records, nil
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}
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// NS returns NS records from the backend
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func NS(ctx context.Context, b ServiceBackend, zone string, state request.Request, opt Options) (records, extra []dns.RR, 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, err := b.Services(ctx, state, false, opt)
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if err != nil {
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return nil, nil, 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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seen := map[string]bool{}
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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, 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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extra = append(extra, newAddress(serv, serv.Host, ip, what))
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ns := serv.NewNS(state.QName())
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if _, ok := seen[ns.Ns]; ok {
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continue
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}
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seen[ns.Ns] = true
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records = append(records, ns)
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}
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}
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return records, extra, nil
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}
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// SOA returns a SOA record from the backend.
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func SOA(ctx context.Context, b ServiceBackend, zone string, state request.Request, opt Options) ([]dns.RR, error) {
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minTTL := b.MinTTL(state)
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ttl := uint32(300)
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if minTTL < ttl {
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ttl = minTTL
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}
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header := dns.RR_Header{Name: zone, Rrtype: dns.TypeSOA, Ttl: ttl, 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: b.Serial(state),
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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
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}
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// BackendError writes an error response to the client.
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func BackendError(ctx context.Context, b ServiceBackend, zone string, rcode int, state request.Request, 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 = true
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m.Ns, _ = SOA(ctx, b, zone, state, opt)
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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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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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// checkForApex checks the special apex.dns directory for records that will be returned as A or AAAA.
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func checkForApex(ctx context.Context, b ServiceBackend, zone string, state request.Request, opt Options) ([]msg.Service, error) {
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|
if state.Name() != zone {
|
|
return b.Services(ctx, state, false, opt)
|
|
}
|
|
|
|
// If the zone name itself is queried we fake the query to search for a special entry
|
|
// this is equivalent to the NS search code.
|
|
old := state.QName()
|
|
state.Clear()
|
|
state.Req.Question[0].Name = dnsutil.Join("apex.dns", zone)
|
|
|
|
services, err := b.Services(ctx, state, false, opt)
|
|
if err == nil {
|
|
state.Req.Question[0].Name = old
|
|
return services, err
|
|
}
|
|
|
|
state.Req.Question[0].Name = old
|
|
return b.Services(ctx, state, false, opt)
|
|
}
|
|
|
|
// item holds records.
|
|
type item struct {
|
|
name string // name of the record (either owner or something else unique).
|
|
port uint16 // port of the record (used for address records, A and AAAA).
|
|
addr string // address of the record (A and AAAA).
|
|
}
|
|
|
|
// isDuplicate uses m to see if the combo (name, addr, port) already exists. If it does
|
|
// not exist already IsDuplicate will also add the record to the map.
|
|
func isDuplicate(m map[item]struct{}, name, addr string, port uint16) bool {
|
|
if addr != "" {
|
|
_, ok := m[item{name, 0, addr}]
|
|
if !ok {
|
|
m[item{name, 0, addr}] = struct{}{}
|
|
}
|
|
return ok
|
|
}
|
|
_, ok := m[item{name, port, ""}]
|
|
if !ok {
|
|
m[item{name, port, ""}] = struct{}{}
|
|
}
|
|
return ok
|
|
}
|
|
|
|
const hostmaster = "hostmaster"
|