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Resolve TXT records via CNAME (#3557)

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* 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>
This commit is contained in:
Jonathan Nagy
2020-01-04 00:16:04 +11:00
committed by Miek Gieben
parent acac649c1b
commit e3266d24f7
6 changed files with 80 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
plugin/etcd/cname_test.go
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@@ -58,6 +58,9 @@ var servicesCname = []*msg.Service{
{Host: "cname6.region2.skydns.test", Key: "cname5.region2.skydns.test."},
{Host: "endpoint.region2.skydns.test", Key: "cname6.region2.skydns.test."},
{Host: "mainendpoint.region2.skydns.test", Key: "region2.skydns.test."},
{Host: "cname2.region3.skydns.test", Key: "cname3.region3.skydns.test."},
{Host: "cname1.region3.skydns.test", Key: "cname2.region3.skydns.test."},
{Host: "region3.skydns.test", Key: "cname1.region3.skydns.test."},
{Host: "", Key: "region3.skydns.test.", Text: "SOME-RECORD-TEXT"},
{Host: "10.240.0.1", Key: "endpoint.region2.skydns.test."},
}
@@ -91,4 +94,13 @@ var dnsTestCasesCname = []test.Case{
test.SOA("skydns.test. 303 IN SOA ns.dns.skydns.test. hostmaster.skydns.test. 1546424605 7200 1800 86400 30"),
},
},
{
Qname: "cname3.region3.skydns.test.", Qtype: dns.TypeTXT,
Answer: []dns.RR{
test.CNAME("cname3.region3.skydns.test. 300 IN CNAME cname2.region3.skydns.test."),
test.CNAME("cname2.region3.skydns.test. 300 IN CNAME cname1.region3.skydns.test."),
test.CNAME("cname1.region3.skydns.test. 300 IN CNAME region3.skydns.test."),
test.TXT("region3.skydns.test. 300 IN TXT \"SOME-RECORD-TEXT\""),
},
},
}

10
plugin/etcd/etcd.go
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@@ -177,11 +177,9 @@ func (e *Etcd) TTL(kv *mvccpb.KeyValue, serv *msg.Service) uint32 {
}
// shouldInclude returns true if the service should be included in a list of records, given the qType. For all the
// currently supported lookup types, the only one to allow for an empty Host field in the service are TXT records.
// Similarly, the TXT record in turn requires the Text field to be set.
// currently supported lookup types, the only one to allow for an empty Host field in the service are TXT records
// which resolve directly. If a TXT record is being resolved by CNAME, then we expect the Host field to have a
// value while the TXT field will be empty.
func shouldInclude(serv *msg.Service, qType uint16) bool {
if qType == dns.TypeTXT {
return serv.Text != ""
}
return serv.Host != ""
return (qType == dns.TypeTXT && serv.Text != "") || serv.Host != ""
}

2
plugin/etcd/handler.go
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@@ -30,7 +30,7 @@ func (e *Etcd) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (
case dns.TypeAAAA:
records, err = plugin.AAAA(ctx, e, zone, state, nil, opt)
case dns.TypeTXT:
records, err = plugin.TXT(ctx, e, zone, state, opt)
records, err = plugin.TXT(ctx, e, zone, state, nil, opt)
case dns.TypeCNAME:
records, err = plugin.CNAME(ctx, e, zone, state, opt)
case dns.TypePTR:

6
plugin/etcd/msg/type.go
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@@ -19,8 +19,12 @@ func (s *Service) HostType() (what uint16, normalized net.IP) {
ip := net.ParseIP(s.Host)
switch {
case ip == nil:
return dns.TypeCNAME, nil
if len(s.Text) == 0 {
return dns.TypeCNAME, nil
}
return dns.TypeTXT, nil
case ip.To4() != nil:
return dns.TypeA, ip.To4()