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plugin/template: support metadata (#2958)

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* Enable use of metadata in templates

* Update README

* Don't stash away ctx, instead use a new func
This commit is contained in:
John Belamaric 2019-07-03 16:10:56 +01:00 • committed by GitHub
parent 2faad5b397
commit 7cf73cc01d
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4 changed files with 135 additions and 4 deletions
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10
plugin/metadata/provider.go
View file

@ -82,6 +82,16 @@ func Labels(ctx context.Context) []string {
return nil
}
// ValueFuncs returns the map[string]Func from the context, or nil if it does not exist.
func ValueFuncs(ctx context.Context) map[string]Func {
if metadata := ctx.Value(key{}); metadata != nil {
if m, ok := metadata.(md); ok {
return m
}
}
return nil
}
// ValueFunc returns the value function of label. If none can be found nil is returned. Calling the
// function returns the value of the label.
func ValueFunc(ctx context.Context, label string) Func {

2
plugin/template/README.md
View file

@ -48,6 +48,8 @@ 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.
* `.Meta` a function that takes a metadata name and returns the value, if the
metadata plugin is enabled. For example, `.Meta "kubernetes/client-namespace"`
The output of the template must be a [RFC 1035](https://tools.ietf.org/html/rfc1035) style resource record (commonly referred to as a "zone file").

22
plugin/template/template.go
View file

@ -8,6 +8,7 @@ import (
gotmpl "text/template"
"github.com/coredns/coredns/plugin"
"github.com/coredns/coredns/plugin/metadata"
"github.com/coredns/coredns/plugin/metrics"
"github.com/coredns/coredns/plugin/pkg/fall"
"github.com/coredns/coredns/plugin/pkg/upstream"
@ -47,6 +48,19 @@ type templateData struct {
Type string
Message *dns.Msg
Question *dns.Question
md map[string]metadata.Func
}
func (data *templateData) Meta(metaName string) string {
if data.md == nil {
return ""
}
if f, ok := data.md[metaName]; ok {
return f()
}
return ""
}
// ServeDNS implements the plugin.Handler interface.
@ -59,7 +73,7 @@ func (h Handler) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
}
for _, template := range h.Templates {
data, match, fthrough := template.match(state, zone)
data, match, fthrough := template.match(ctx, state, zone)
if !match {
if !fthrough {
return dns.RcodeNameError, nil
@ -114,7 +128,7 @@ func (h Handler) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
// Name implements the plugin.Handler interface.
func (h Handler) Name() string { return "template" }
func executeRRTemplate(server, section string, template *gotmpl.Template, data templateData) (dns.RR, error) {
func executeRRTemplate(server, section string, template *gotmpl.Template, data *templateData) (dns.RR, error) {
buffer := &bytes.Buffer{}
err := template.Execute(buffer, data)
if err != nil {
@ -129,9 +143,9 @@ func executeRRTemplate(server, section string, template *gotmpl.Template, data t
return rr, nil
}
func (t template) match(state request.Request, zone string) (templateData, bool, bool) {
func (t template) match(ctx context.Context, state request.Request, zone string) (*templateData, bool, bool) {
q := state.Req.Question[0]
data := templateData{}
data := &templateData{md: metadata.ValueFuncs(ctx)}
zone = plugin.Zones(t.zones).Matches(state.Name())
if zone == "" {

105
plugin/template/template_test.go
View file

@ -7,6 +7,7 @@ import (
"testing"
gotmpl "text/template"
"github.com/coredns/coredns/plugin/metadata"
"github.com/coredns/coredns/plugin/pkg/dnstest"
"github.com/coredns/coredns/plugin/pkg/fall"
"github.com/coredns/coredns/plugin/test"
@ -100,6 +101,24 @@ func TestHandler(t *testing.T) {
fall: fall.Root,
zones: []string{"."},
}
mdTemplate := template{
regex: []*regexp.Regexp{regexp.MustCompile("(^|[.])ip-10-(?P<b>[0-9]*)-(?P<c>[0-9]*)-(?P<d>[0-9]*)[.]example[.]$")},
answer: []*gotmpl.Template{gotmpl.Must(gotmpl.New("answer").Parse(`{{ .Meta "foo" }}-{{ .Name }} 60 IN A 10.{{ .Group.b }}.{{ .Group.c }}.{{ .Group.d }}`))},
additional: []*gotmpl.Template{gotmpl.Must(gotmpl.New("additional").Parse(`{{ .Meta "bar" }}.example. IN A 203.0.113.8`))},
authority: []*gotmpl.Template{gotmpl.Must(gotmpl.New("authority").Parse(`example. IN NS {{ .Meta "bar" }}.example.com.`))},
qclass: dns.ClassANY,
qtype: dns.TypeANY,
fall: fall.Root,
zones: []string{"."},
}
mdMissingTemplate := template{
regex: []*regexp.Regexp{regexp.MustCompile("(^|[.])ip-10-(?P<b>[0-9]*)-(?P<c>[0-9]*)-(?P<d>[0-9]*)[.]example[.]$")},
answer: []*gotmpl.Template{gotmpl.Must(gotmpl.New("answer").Parse(`{{ .Meta "foofoo" }}{{ .Name }} 60 IN A 10.{{ .Group.b }}.{{ .Group.c }}.{{ .Group.d }}`))},
qclass: dns.ClassANY,
qtype: dns.TypeANY,
fall: fall.Root,
zones: []string{"."},
}
tests := []struct {
tmpl template
@ -110,6 +129,7 @@ func TestHandler(t *testing.T) {
expectedCode int
expectedErr string
verifyResponse func(*dns.Msg) error
md map[string]string
}{
{
name: "RcodeServFail",
@ -276,6 +296,78 @@ func TestHandler(t *testing.T) {
return nil
},
},
{
name: "mdMatch",
tmpl: mdTemplate,
qclass: dns.ClassINET,
qtype: dns.TypeA,
qname: "ip-10-95-12-8.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])
}
name := "myfoo-ip-10-95-12-8.example."
if r.Answer[0].Header().Name != name {
return fmt.Errorf("expected answer name %q, got %q", name, r.Answer[0].Header().Name)
}
if len(r.Extra) != 1 {
return fmt.Errorf("expected 1 extra record, got %v", len(r.Extra))
}
if r.Extra[0].Header().Rrtype != dns.TypeA {
return fmt.Errorf("expected an additional A record, got %v", dns.TypeToString[r.Extra[0].Header().Rrtype])
}
name = "mybar.example."
if r.Extra[0].Header().Name != name {
return fmt.Errorf("expected additional name %q, got %q", name, r.Extra[0].Header().Name)
}
if len(r.Ns) != 1 {
return fmt.Errorf("expected 1 authoritative record, got %v", len(r.Extra))
}
if r.Ns[0].Header().Rrtype != dns.TypeNS {
return fmt.Errorf("expected an authoritative NS record, got %v", dns.TypeToString[r.Extra[0].Header().Rrtype])
}
ns, ok := r.Ns[0].(*dns.NS)
if !ok {
return fmt.Errorf("expected NS record to be type NS, got %v", r.Ns[0])
}
rdata := "mybar.example.com."
if ns.Ns != rdata {
return fmt.Errorf("expected ns rdata %q, got %q", rdata, ns.Ns)
}
return nil
},
md: map[string]string{
"foo": "myfoo",
"bar": "mybar",
"foobar": "myfoobar",
},
},
{
name: "mdMissing",
tmpl: mdMissingTemplate,
qclass: dns.ClassINET,
qtype: dns.TypeA,
qname: "ip-10-95-12-8.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])
}
name := "ip-10-95-12-8.example."
if r.Answer[0].Header().Name != name {
return fmt.Errorf("expected answer name %q, got %q", name, r.Answer[0].Header().Name)
}
return nil
},
md: map[string]string{
"foo": "myfoo",
},
},
}
ctx := context.TODO()
@ -294,6 +386,19 @@ func TestHandler(t *testing.T) {
}},
}
rec := dnstest.NewRecorder(&test.ResponseWriter{})
if tr.md != nil {
ctx = metadata.ContextWithMetadata(context.Background())
for k, v := range tr.md {
// Go requires copying to a local variable for the closure to work
kk := k
vv := v
metadata.SetValueFunc(ctx, kk, func() string {
return vv
})
}
}
code, err := handler.ServeDNS(ctx, rec, req)
if err == nil && tr.expectedErr != "" {
t.Errorf("Test %v expected error: %v, got nothing", tr.name, tr.expectedErr)