plugin/template: Add client IP data (#4034)

Signed-off-by: Maxime Guyot <maxime@root314.com>

plugin/template/README.md

@@ -48,6 +48,7 @@ Each resource record is a full-featured [Go template](https://golang.org/pkg/tex
 * `.Group` a map of the named capture groups.
 * `.Message` the complete incoming DNS message.
 * `.Question` the matched question section.
+* `.Remote` client’s IP address
 * `.Meta` a function that takes a metadata name and returns the value, if the
   metadata plugin is enabled. For example, `.Meta "kubernetes/client-namespace"`
 

plugin/template/template.go

@@ -48,6 +48,7 @@ type templateData struct {
 	Type     string
 	Message  *dns.Msg
 	Question *dns.Question
+	Remote   string
 	md       map[string]metadata.Func
 }
 
@@ -145,7 +146,7 @@ func executeRRTemplate(server, section string, template *gotmpl.Template, data *
 
 func (t template) match(ctx context.Context, state request.Request) (*templateData, bool, bool) {
 	q := state.Req.Question[0]
-	data := &templateData{md: metadata.ValueFuncs(ctx)}
+	data := &templateData{md: metadata.ValueFuncs(ctx), Remote: state.IP()}
 
 	zone := plugin.Zones(t.zones).Matches(state.Name())
 	if zone == "" {

plugin/template/template_test.go

@@ -25,6 +25,14 @@ func TestHandler(t *testing.T) {
 		fall:   fall.Root,
 		zones:  []string{"."},
 	}
+	exampleDomainIPATemplate := template{
+		regex:  []*regexp.Regexp{regexp.MustCompile(".*")},
+		answer: []*gotmpl.Template{gotmpl.Must(gotmpl.New("answer").Parse("{{ .Name }} 60 IN A {{ .Remote }}"))},
+		qclass: dns.ClassINET,
+		qtype:  dns.TypeA,
+		fall:   fall.Root,
+		zones:  []string{"."},
+	}
 	exampleDomainANSTemplate := template{
 		regex:      []*regexp.Regexp{regexp.MustCompile("(^|[.])ip-10-(?P<b>[0-9]*)-(?P<c>[0-9]*)-(?P<d>[0-9]*)[.]example[.]$")},
 		answer:     []*gotmpl.Template{gotmpl.Must(gotmpl.New("answer").Parse("{{ .Name }} 60 IN A 10.{{ .Group.b }}.{{ .Group.c }}.{{ .Group.d }}"))},
@@ -196,6 +204,25 @@ func TestHandler(t *testing.T) {
 				return nil
 			},
 		},
+		{
+			name:   "ExampleIPMatch",
+			tmpl:   exampleDomainIPATemplate,
+			qclass: dns.ClassINET,
+			qtype:  dns.TypeA,
+			qname:  "test.example.",
+			verifyResponse: func(r *dns.Msg) error {
+				if len(r.Answer) != 1 {
+					return fmt.Errorf("expected 1 answer, got %v", len(r.Answer))
+				}
+				if r.Answer[0].Header().Rrtype != dns.TypeA {
+					return fmt.Errorf("expected an A record answer, got %v", dns.TypeToString[r.Answer[0].Header().Rrtype])
+				}
+				if r.Answer[0].(*dns.A).A.String() != "10.240.0.1" {
+					return fmt.Errorf("expected an A record for 10.95.12.8, got %v", r.Answer[0].String())
+				}
+				return nil
+			},
+		},
 		{
 			name:   "ExampleDomainMatch",
 			tmpl:   exampleDomainATemplate,