msg.Service: add HostType() method (#627)

This method parses the Host field in the service. It returns 1 or 3
things 1) it is a host 2) an IPv4 address or an 3) IPv6 address.
This simplifies some code a bit and allows for 1 way of parsing the Host
field.

This *only* parse the Host field, Mail and/or Text values should be
checked separately.

We reuse the dns.TypeXXX values for this as to not invent anything new.

3 files changed, 114 insertions, 40 deletions

diff --git a/middleware/backend_lookup.go b/middleware/backend_lookup.go
index 8b86495bb..41968c2fa 100644
--- a/middleware/backend_lookup.go
+++ b/middleware/backend_lookup.go
@@ -21,9 +21,11 @@ func A(b ServiceBackend, zone string, state request.Request, previousRecords []d
 	}
 
 	for _, serv := range services {
-		ip := net.ParseIP(serv.Host)
-		switch {
-		case ip == nil:
+
+		what, ip := serv.HostType()
+
+		switch what {
+		case dns.TypeANY:
 			if Name(state.Name()).Matches(dns.Fqdn(serv.Host)) {
 				// x CNAME x is a direct loop, don't add those
 				continue
@@ -67,9 +69,11 @@ func A(b ServiceBackend, zone string, state request.Request, previousRecords []d
 			records = append(records, newRecord)
 			records = append(records, m1.Answer...)
 			continue
-		case ip.To4() != nil:
-			records = append(records, serv.NewA(state.QName(), ip.To4()))
-		case ip.To4() == nil:
+
+		case dns.TypeA:
+			records = append(records, serv.NewA(state.QName(), ip))
+
+		case dns.TypeAAAA:
 			// nodata?
 		}
 	}
@@ -84,9 +88,11 @@ func AAAA(b ServiceBackend, zone string, state request.Request, previousRecords
 	}
 
 	for _, serv := range services {
-		ip := net.ParseIP(serv.Host)
-		switch {
-		case ip == nil:
+
+		what, ip := serv.HostType()
+
+		switch what {
+		case dns.TypeANY:
 			// Try to resolve as CNAME if it's not an IP, but only if we don't create loops.
 			if Name(state.Name()).Matches(dns.Fqdn(serv.Host)) {
 				// x CNAME x is a direct loop, don't add those
@@ -131,10 +137,12 @@ func AAAA(b ServiceBackend, zone string, state request.Request, previousRecords
 			records = append(records, m1.Answer...)
 			continue
 			// both here again
-		case ip.To4() != nil:
+
+		case dns.TypeA:
 			// nada?
-		case ip.To4() == nil:
-			records = append(records, serv.NewAAAA(state.QName(), ip.To16()))
+
+		case dns.TypeAAAA:
+			records = append(records, serv.NewAAAA(state.QName(), ip))
 		}
 	}
 	return records, debug, nil
@@ -170,9 +178,11 @@ func SRV(b ServiceBackend, zone string, state request.Request, opt Options) (rec
 			w1 *= float64(serv.Weight)
 		}
 		weight := uint16(math.Floor(w1))
-		ip := net.ParseIP(serv.Host)
-		switch {
-		case ip == nil:
+
+		what, ip := serv.HostType()
+
+		switch what {
+		case dns.TypeANY:
 			srv := serv.NewSRV(state.QName(), weight)
 			records = append(records, srv)
 
@@ -214,18 +224,13 @@ func SRV(b ServiceBackend, zone string, state request.Request, opt Options) (rec
 				debug = append(debug, debugAddr...)
 			}
 			// IPv6 lookups here as well? AAAA(zone, state1, nil).
-		case ip.To4() != nil:
-			serv.Host = msg.Domain(serv.Key)
-			srv := serv.NewSRV(state.QName(), weight)
 
-			records = append(records, srv)
-			extra = append(extra, serv.NewA(srv.Target, ip.To4()))
-		case ip.To4() == nil:
+		case dns.TypeA, dns.TypeAAAA:
 			serv.Host = msg.Domain(serv.Key)
 			srv := serv.NewSRV(state.QName(), weight)
 
 			records = append(records, srv)
-			extra = append(extra, serv.NewAAAA(srv.Target, ip.To16()))
+			extra = append(extra, newAddress(serv, srv.Target, ip, what))
 		}
 	}
 	return records, extra, debug, nil
@@ -243,9 +248,9 @@ func MX(b ServiceBackend, zone string, state request.Request, opt Options) (reco
 		if !serv.Mail {
 			continue
 		}
-		ip := net.ParseIP(serv.Host)
-		switch {
-		case ip == nil:
+		what, ip := serv.HostType()
+		switch what {
+		case dns.TypeANY:
 			mx := serv.NewMX(state.QName())
 			records = append(records, mx)
 			if _, ok := lookup[mx.Mx]; ok {
@@ -284,14 +289,11 @@ func MX(b ServiceBackend, zone string, state request.Request, opt Options) (reco
 				debug = append(debug, debugAddr...)
 			}
 			// e.AAAA as well
-		case ip.To4() != nil:
-			serv.Host = msg.Domain(serv.Key)
-			records = append(records, serv.NewMX(state.QName()))
-			extra = append(extra, serv.NewA(serv.Host, ip.To4()))
-		case ip.To4() == nil:
+
+		case dns.TypeA, dns.TypeAAAA:
 			serv.Host = msg.Domain(serv.Key)
 			records = append(records, serv.NewMX(state.QName()))
-			extra = append(extra, serv.NewAAAA(serv.Host, ip.To16()))
+			extra = append(extra, newAddress(serv, serv.Host, ip, what))
 		}
 	}
 	return records, extra, debug, nil
@@ -360,18 +362,15 @@ func NS(b ServiceBackend, zone string, state request.Request, opt Options) (reco
 	state.Req.Question[0].Name = old
 
 	for _, serv := range services {
-		ip := net.ParseIP(serv.Host)
-		switch {
-		case ip == nil:
+		what, ip := serv.HostType()
+		switch what {
+		case dns.TypeANY:
 			return nil, nil, debug, fmt.Errorf("NS record must be an IP address: %s", serv.Host)
-		case ip.To4() != nil:
-			serv.Host = msg.Domain(serv.Key)
-			records = append(records, serv.NewNS(state.QName()))
-			extra = append(extra, serv.NewA(serv.Host, ip.To4()))
-		case ip.To4() == nil:
+
+		case dns.TypeA, dns.TypeAAAA:
 			serv.Host = msg.Domain(serv.Key)
 			records = append(records, serv.NewNS(state.QName()))
-			extra = append(extra, serv.NewAAAA(serv.Host, ip.To16()))
+			extra = append(extra, newAddress(serv, serv.Host, ip, what))
 		}
 	}
 	return records, extra, debug, nil
@@ -445,6 +444,17 @@ func ErrorToTxt(err error) dns.RR {
 	return t
 }
 
+func newAddress(s msg.Service, name string, ip net.IP, what uint16) dns.RR {
+
+	hdr := dns.RR_Header{Name: name, Rrtype: what, Class: dns.ClassINET, Ttl: s.TTL}
+
+	if what == dns.TypeA {
+		return &dns.A{Hdr: hdr, A: ip}
+	}
+	// Should always be dns.TypeAAAA
+	return &dns.AAAA{Hdr: hdr, AAAA: ip}
+}
+
 const (
 	minTTL     = 60
 	hostmaster = "hostmaster"
diff --git a/middleware/etcd/msg/type.go b/middleware/etcd/msg/type.go
new file mode 100644
index 000000000..807e7b471
--- /dev/null
+++ b/middleware/etcd/msg/type.go
@@ -0,0 +1,33 @@
+package msg
+
+import (
+	"net"
+
+	"github.com/miekg/dns"
+)
+
+// HostType returns the DNS type of what is encoded in the Service Host field. We're reusing
+// dns.TypeXXX to not reinvent a new set of identifiers.
+//
+// dns.TypeA: the service's Host field contains an A record.
+// dns.TypeAAAA: the service's Host field contains an AAAA record.
+// dns.TypeANY: the service's Host field contains a name.
+//
+// Note that a service can double/triple as a TXT record or MX record.
+func (s *Service) HostType() (what uint16, normalized net.IP) {
+
+	ip := net.ParseIP(s.Host)
+
+	switch {
+	case ip == nil:
+		return dns.TypeANY, nil
+
+	case ip.To4() != nil:
+		return dns.TypeA, ip.To4()
+
+	case ip.To4() == nil:
+		return dns.TypeAAAA, ip.To16()
+	}
+	// This should never be reached.
+	return dns.TypeNone, nil
+}
diff --git a/middleware/etcd/msg/type_test.go b/middleware/etcd/msg/type_test.go
new file mode 100644
index 000000000..5fef74b23
--- /dev/null
+++ b/middleware/etcd/msg/type_test.go
@@ -0,0 +1,31 @@
+package msg
+
+import (
+	"testing"
+
+	"github.com/miekg/dns"
+)
+
+func TestType(t *testing.T) {
+	tests := []struct {
+		serv         Service
+		expectedType uint16
+	}{
+		{Service{Host: "example.org"}, dns.TypeANY},
+		{Service{Host: "127.0.0.1"}, dns.TypeA},
+		{Service{Host: "2000::3"}, dns.TypeAAAA},
+		{Service{Host: "2000..3"}, dns.TypeANY},
+		{Service{Host: "127.0.0.257"}, dns.TypeANY},
+		{Service{Host: "127.0.0.252", Mail: true}, dns.TypeA},
+		{Service{Host: "127.0.0.252", Mail: true, Text: "a"}, dns.TypeA},
+		{Service{Host: "127.0.0.254", Mail: false, Text: "a"}, dns.TypeA},
+	}
+
+	for i, tc := range tests {
+		what, _ := tc.serv.HostType()
+		if what != tc.expectedType {
+			t.Errorf("Test %d: Expected what %v, but got %v", i, tc.expectedType, what)
+		}
+	}
+
+}