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dns: send NXDOMAIN for non-existant local names

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This commit is contained in:
Michael Stapelberg 2018-06-23 22:15:35 +02:00
parent 3886367a32
commit c96c683e43
2 changed files with 51 additions and 15 deletions
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16
internal/dns/dns.go
View File

@ -179,6 +179,7 @@ func (s *Server) handleRequest(w dns.ResponseWriter, r *dns.Msg) {
name = strings.TrimSuffix(name, "."+s.domain) name = strings.TrimSuffix(name, "."+s.domain)
if !strings.Contains(name, ".") { if !strings.Contains(name, ".") {
s.prom.upstream.WithLabelValues("local").Inc()
if host, ok := s.hostByName(name); ok { if host, ok := s.hostByName(name); ok {
rr, err := dns.NewRR(q.Name + " 3600 IN A " + host) rr, err := dns.NewRR(q.Name + " 3600 IN A " + host)
if err != nil { if err != nil {
@ -188,13 +189,19 @@ func (s *Server) handleRequest(w dns.ResponseWriter, r *dns.Msg) {
m.SetReply(r) m.SetReply(r)
m.Answer = append(m.Answer, rr) m.Answer = append(m.Answer, rr)
w.WriteMsg(m) w.WriteMsg(m)
s.prom.upstream.WithLabelValues("local").Inc()
return return
} }
// Send an authoritative NXDOMAIN for local names:
m := new(dns.Msg)
m.SetReply(r)
m.SetRcode(r, dns.RcodeNameError)
w.WriteMsg(m)
return
} }
} }
if q.Qtype == dns.TypePTR && q.Qclass == dns.ClassINET { if q.Qtype == dns.TypePTR && q.Qclass == dns.ClassINET {
if isLocalInAddrArpa(q.Name) { if isLocalInAddrArpa(q.Name) {
s.prom.upstream.WithLabelValues("local").Inc()
if host, ok := s.hostByIP(q.Name); ok { if host, ok := s.hostByIP(q.Name); ok {
rr, err := dns.NewRR(q.Name + " 3600 IN PTR " + host + "." + s.domain) rr, err := dns.NewRR(q.Name + " 3600 IN PTR " + host + "." + s.domain)
if err != nil { if err != nil {
@ -204,9 +211,14 @@ func (s *Server) handleRequest(w dns.ResponseWriter, r *dns.Msg) {
m.SetReply(r) m.SetReply(r)
m.Answer = append(m.Answer, rr) m.Answer = append(m.Answer, rr)
w.WriteMsg(m) w.WriteMsg(m)
s.prom.upstream.WithLabelValues("local").Inc()
return return
} }
// Send an authoritative NXDOMAIN for local names:
m := new(dns.Msg)
m.SetReply(r)
m.SetRcode(r, dns.RcodeNameError)
w.WriteMsg(m)
return
} }
} }
} }

50
internal/dns/dns_test.go
View File

@ -60,19 +60,31 @@ func TestDHCP(t *testing.T) {
Addr: net.IP{192, 168, 42, 23}, Addr: net.IP{192, 168, 42, 23},
}, },
}) })
m := new(dns.Msg)
m.SetQuestion("xps.lan.", dns.TypeA) t.Run("xps.lan.", func(t *testing.T) {
s.handleRequest(r, m) m := new(dns.Msg)
if got, want := len(r.response.Answer), 1; got != want { m.SetQuestion("xps.lan.", dns.TypeA)
t.Fatalf("unexpected number of answers: got %d, want %d", got, want) s.handleRequest(r, m)
} if got, want := len(r.response.Answer), 1; got != want {
a := r.response.Answer[0] t.Fatalf("unexpected number of answers: got %d, want %d", got, want)
if _, ok := a.(*dns.A); !ok { }
t.Fatalf("unexpected response type: got %T, want dns.A", a) a := r.response.Answer[0]
} if _, ok := a.(*dns.A); !ok {
if got, want := a.(*dns.A).A.To4(), (net.IP{192, 168, 42, 23}); !bytes.Equal(got, want) { t.Fatalf("unexpected response type: got %T, want dns.A", a)
t.Fatalf("unexpected response IP: got %v, want %v", got, want) }
} if got, want := a.(*dns.A).A.To4(), (net.IP{192, 168, 42, 23}); !bytes.Equal(got, want) {
t.Fatalf("unexpected response IP: got %v, want %v", got, want)
}
})
t.Run("notfound.lan.", func(t *testing.T) {
m := new(dns.Msg)
m.SetQuestion("notfound.lan.", dns.TypeA)
s.handleRequest(r, m)
if got, want := r.response.Rcode, dns.RcodeNameError; got != want {
t.Fatalf("unexpected rcode: got %v, want %v", got, want)
}
})
} }
func TestHostname(t *testing.T) { func TestHostname(t *testing.T) {
@ -166,6 +178,18 @@ func TestDHCPReverse(t *testing.T) {
} }
}) })
} }
t.Run("no leases", func(t *testing.T) {
r := &recorder{}
s := NewServer("localhost:0", "lan")
m := new(dns.Msg)
m.SetQuestion("254.255.31.172.in-addr.arpa.", dns.TypePTR)
s.handleRequest(r, m)
if got, want := r.response.Rcode, dns.RcodeNameError; got != want {
t.Fatalf("unexpected rcode: got %v, want %v", got, want)
}
})
} }
// TODO: multiple questions // TODO: multiple questions