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package template
import (
"bytes"
"context"
"regexp"
"strconv"
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/request"
"github.com/miekg/dns"
)
// Handler is a plugin handler that takes a query and templates a response.
type Handler struct {
Zones []string
Next plugin.Handler
Templates []template
}
type template struct {
zones []string
rcode int
regex []*regexp.Regexp
answer []*gotmpl.Template
additional []*gotmpl.Template
authority []*gotmpl.Template
qclass uint16
qtype uint16
ederror *ederror
fall fall.F
upstream Upstreamer
}
type ederror struct {
code uint16
reason string
}
// Upstreamer looks up targets of CNAME templates
type Upstreamer interface {
Lookup(ctx context.Context, state request.Request, name string, typ uint16) (*dns.Msg, error)
}
type templateData struct {
Zone string
Name string
Regex string
Match []string
Group map[string]string
Class string
Type string
Message *dns.Msg
Question *dns.Question
Remote string
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.
func (h Handler) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
state := request.Request{W: w, Req: r}
zone := plugin.Zones(h.Zones).Matches(state.Name())
if zone == "" {
return plugin.NextOrFailure(h.Name(), h.Next, ctx, w, r)
}
for _, template := range h.Templates {
data, match, fthrough := template.match(ctx, state)
if !match {
if !fthrough {
return dns.RcodeServerFailure, nil
}
continue
}
templateMatchesCount.WithLabelValues(metrics.WithServer(ctx), data.Zone, metrics.WithView(ctx), data.Class, data.Type).Inc()
if template.rcode == dns.RcodeServerFailure {
return template.rcode, nil
}
msg := new(dns.Msg)
msg.SetReply(r)
msg.Authoritative = true
msg.Rcode = template.rcode
for _, answer := range template.answer {
rr, err := executeRRTemplate(metrics.WithServer(ctx), metrics.WithView(ctx), "answer", answer, data)
if err != nil {
return dns.RcodeServerFailure, err
}
msg.Answer = append(msg.Answer, rr)
if template.upstream != nil && (state.QType() == dns.TypeA || state.QType() == dns.TypeAAAA) && rr.Header().Rrtype == dns.TypeCNAME {
if up, err := template.upstream.Lookup(ctx, state, rr.(*dns.CNAME).Target, state.QType()); err == nil && up != nil {
msg.Truncated = up.Truncated
msg.Answer = append(msg.Answer, up.Answer...)
}
}
}
for _, additional := range template.additional {
rr, err := executeRRTemplate(metrics.WithServer(ctx), metrics.WithView(ctx), "additional", additional, data)
if err != nil {
return dns.RcodeServerFailure, err
}
msg.Extra = append(msg.Extra, rr)
}
for _, authority := range template.authority {
rr, err := executeRRTemplate(metrics.WithServer(ctx), metrics.WithView(ctx), "authority", authority, data)
if err != nil {
return dns.RcodeServerFailure, err
}
msg.Ns = append(msg.Ns, rr)
}
if template.ederror != nil {
msg = msg.SetEdns0(4096, true)
ede := dns.EDNS0_EDE{InfoCode: template.ederror.code, ExtraText: template.ederror.reason}
msg.IsEdns0().Option = append(msg.IsEdns0().Option, &ede)
}
w.WriteMsg(msg)
return template.rcode, nil
}
return plugin.NextOrFailure(h.Name(), h.Next, ctx, w, r)
}
// Name implements the plugin.Handler interface.
func (h Handler) Name() string { return "template" }
func executeRRTemplate(server, view, section string, template *gotmpl.Template, data *templateData) (dns.RR, error) {
buffer := &bytes.Buffer{}
err := template.Execute(buffer, data)
if err != nil {
templateFailureCount.WithLabelValues(server, data.Zone, view, data.Class, data.Type, section, template.Tree.Root.String()).Inc()
return nil, err
}
rr, err := dns.NewRR(buffer.String())
if err != nil {
templateRRFailureCount.WithLabelValues(server, data.Zone, view, data.Class, data.Type, section, template.Tree.Root.String()).Inc()
return rr, err
}
return rr, nil
}
func newTemplate(name, text string) (*gotmpl.Template, error) {
funcMap := gotmpl.FuncMap{
"parseInt": strconv.ParseUint,
}
return gotmpl.New(name).Funcs(funcMap).Parse(text)
}
func (t template) match(ctx context.Context, state request.Request) (*templateData, bool, bool) {
q := state.Req.Question[0]
data := &templateData{md: metadata.ValueFuncs(ctx), Remote: state.IP()}
zone := plugin.Zones(t.zones).Matches(state.Name())
if zone == "" {
return data, false, true
}
if t.qclass != dns.ClassANY && q.Qclass != dns.ClassANY && q.Qclass != t.qclass {
return data, false, true
}
if t.qtype != dns.TypeANY && q.Qtype != dns.TypeANY && q.Qtype != t.qtype {
return data, false, true
}
for _, regex := range t.regex {
if !regex.MatchString(state.Name()) {
continue
}
data.Zone = zone
data.Regex = regex.String()
data.Name = state.Name()
data.Question = &q
data.Message = state.Req
if q.Qclass != dns.ClassANY {
data.Class = dns.ClassToString[q.Qclass]
} else {
data.Class = dns.ClassToString[t.qclass]
}
if q.Qtype != dns.TypeANY {
data.Type = dns.TypeToString[q.Qtype]
} else {
data.Type = dns.TypeToString[t.qtype]
}
matches := regex.FindStringSubmatch(state.Name())
data.Match = make([]string, len(matches))
data.Group = make(map[string]string)
groupNames := regex.SubexpNames()
for i, m := range matches {
data.Match[i] = m
data.Group[strconv.Itoa(i)] = m
}
for i, m := range matches {
if len(groupNames[i]) > 0 {
data.Group[groupNames[i]] = m
}
}
return data, true, false
}
return data, false, t.fall.Through(state.Name())
}
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