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plugin/k8s_external: fix SRV queries doesn't work with AWS ELB/NLB (#4929)

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* fix for issue #4927

Signed-off-by: denis-tingaikin <denis.tingajkin@xored.com>

* apply review comments

Signed-off-by: denis-tingaikin <denis.tingajkin@xored.com>

* apply review comments

Signed-off-by: denis-tingaikin <denis.tingajkin@xored.com>
This commit is contained in:
Denis Tingaikin 2021-10-27 16:59:21 +03:00 • committed by GitHub
parent 6a6905c16c
commit de21fb2436
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GPG key ID: 4AEE18F83AFDEB23
3 changed files with 24 additions and 10 deletions
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2
plugin/k8s_external/external.go
View file

@ -97,7 +97,7 @@ func (e *External) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Ms
case dns.TypeAAAA: case dns.TypeAAAA:
m.Answer = e.aaaa(ctx, svc, state) m.Answer = e.aaaa(ctx, svc, state)
case dns.TypeSRV: case dns.TypeSRV:
m.Answer, m.Extra = e.srv(svc, state) m.Answer, m.Extra = e.srv(ctx, svc, state)
default: default:
m.Ns = []dns.RR{e.soa(state)} m.Ns = []dns.RR{e.soa(state)}
} }

6
plugin/k8s_external/external_test.go
View file

@ -153,6 +153,12 @@ var tests = []test.Case{
test.A("svc11.testns.example.com. 5 IN A 1.2.3.4"), test.A("svc11.testns.example.com. 5 IN A 1.2.3.4"),
}, },
}, },
{
Qname: "_http._tcp.svc12.testns.example.com.", Qtype: dns.TypeSRV, Rcode: dns.RcodeSuccess,
Answer: []dns.RR{
test.SRV("_http._tcp.svc12.testns.example.com. 5 IN SRV 0 100 80 dummy.hostname."),
},
},
{ {
Qname: "svc12.testns.example.com.", Qtype: dns.TypeA, Rcode: dns.RcodeSuccess, Qname: "svc12.testns.example.com.", Qtype: dns.TypeA, Rcode: dns.RcodeSuccess,
Answer: []dns.RR{ Answer: []dns.RR{

26
plugin/k8s_external/msg_to_dns.go
View file

@ -22,9 +22,7 @@ func (e *External) a(ctx context.Context, services []msg.Service, state request.
rr := s.NewCNAME(state.QName(), s.Host) rr := s.NewCNAME(state.QName(), s.Host)
records = append(records, rr) records = append(records, rr)
if resp, err := e.upstream.Lookup(ctx, state, dns.Fqdn(s.Host), dns.TypeA); err == nil { if resp, err := e.upstream.Lookup(ctx, state, dns.Fqdn(s.Host), dns.TypeA); err == nil {
for _, rr := range resp.Answer { records = append(records, resp.Answer...)
records = append(records, rr)
}
} }
case dns.TypeA: case dns.TypeA:
@ -54,9 +52,7 @@ func (e *External) aaaa(ctx context.Context, services []msg.Service, state reque
rr := s.NewCNAME(state.QName(), s.Host) rr := s.NewCNAME(state.QName(), s.Host)
records = append(records, rr) records = append(records, rr)
if resp, err := e.upstream.Lookup(ctx, state, dns.Fqdn(s.Host), dns.TypeAAAA); err == nil { if resp, err := e.upstream.Lookup(ctx, state, dns.Fqdn(s.Host), dns.TypeAAAA); err == nil {
for _, rr := range resp.Answer { records = append(records, resp.Answer...)
records = append(records, rr)
}
} }
case dns.TypeA: case dns.TypeA:
@ -74,7 +70,7 @@ func (e *External) aaaa(ctx context.Context, services []msg.Service, state reque
return records return records
} }
func (e *External) srv(services []msg.Service, state request.Request) (records, extra []dns.RR) { func (e *External) srv(ctx context.Context, services []msg.Service, state request.Request) (records, extra []dns.RR) {
dup := make(map[item]struct{}) dup := make(map[item]struct{})
// Looping twice to get the right weight vs priority. This might break because we may drop duplicate SRV records latter on. // Looping twice to get the right weight vs priority. This might break because we may drop duplicate SRV records latter on.
@ -111,9 +107,21 @@ func (e *External) srv(services []msg.Service, state request.Request) (records,
what, ip := s.HostType() what, ip := s.HostType()
switch what { switch what {
case dns.TypeCNAME:
// can't happen
case dns.TypeCNAME:
addr := dns.Fqdn(s.Host)
srv := s.NewSRV(state.QName(), weight)
if ok := isDuplicate(dup, srv.Target, "", srv.Port); !ok {
records = append(records, srv)
}
if ok := isDuplicate(dup, srv.Target, addr, 0); !ok {
if resp, err := e.upstream.Lookup(ctx, state, addr, dns.TypeA); err == nil {
extra = append(extra, resp.Answer...)
}
if resp, err := e.upstream.Lookup(ctx, state, addr, dns.TypeAAAA); err == nil {
extra = append(extra, resp.Answer...)
}
}
case dns.TypeA, dns.TypeAAAA: case dns.TypeA, dns.TypeAAAA:
addr := s.Host addr := s.Host
s.Host = msg.Domain(s.Key) s.Host = msg.Domain(s.Key)