plugin/cache: key cache on Checking Disabled (CD) bit (#6354)
* plugin/cache: key cache on Checking Disabled (CD) bit Key the cache on CD bit, which effectively separates the entries for queries with CD disabled or enabled. Signed-off-by: Grant Spence <gspence@redhat.com>
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Grant Spence
GitHub
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commit
997c7f9539
5 changed files with 520 additions and 287 deletions
228
plugin/cache/prefetch_test.go
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228
plugin/cache/prefetch_test.go
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package cache
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import (
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"context"
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"fmt"
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"testing"
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"time"
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"github.com/coredns/coredns/plugin"
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"github.com/coredns/coredns/plugin/pkg/dnstest"
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"github.com/coredns/coredns/plugin/test"
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"github.com/miekg/dns"
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)
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func TestPrefetch(t *testing.T) {
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tests := []struct {
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qname string
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ttl int
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prefetch int
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verifications []verification
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}{
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{
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qname: "hits.reset.example.org.",
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ttl: 80,
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prefetch: 1,
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verifications: []verification{
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{
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after: 0 * time.Second,
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answer: "hits.reset.example.org. 80 IN A 127.0.0.1",
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fetch: true, // Initial fetch
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},
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{
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after: 73 * time.Second,
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answer: "hits.reset.example.org. 7 IN A 127.0.0.1",
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fetch: true, // Triggers prefetch with 7 TTL (10% of 80 = 8 TTL threshold)
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},
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{
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after: 80 * time.Second,
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answer: "hits.reset.example.org. 73 IN A 127.0.0.2",
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},
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},
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},
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{
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qname: "short.ttl.example.org.",
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ttl: 5,
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prefetch: 1,
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verifications: []verification{
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{
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after: 0 * time.Second,
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answer: "short.ttl.example.org. 5 IN A 127.0.0.1",
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fetch: true,
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},
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{
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after: 1 * time.Second,
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answer: "short.ttl.example.org. 4 IN A 127.0.0.1",
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},
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{
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after: 4 * time.Second,
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answer: "short.ttl.example.org. 1 IN A 127.0.0.1",
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fetch: true,
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},
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{
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after: 5 * time.Second,
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answer: "short.ttl.example.org. 4 IN A 127.0.0.2",
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},
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},
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},
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{
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qname: "no.prefetch.example.org.",
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ttl: 30,
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prefetch: 0,
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verifications: []verification{
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{
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after: 0 * time.Second,
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answer: "no.prefetch.example.org. 30 IN A 127.0.0.1",
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fetch: true,
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},
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{
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after: 15 * time.Second,
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answer: "no.prefetch.example.org. 15 IN A 127.0.0.1",
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},
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{
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after: 29 * time.Second,
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answer: "no.prefetch.example.org. 1 IN A 127.0.0.1",
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},
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{
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after: 30 * time.Second,
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answer: "no.prefetch.example.org. 30 IN A 127.0.0.2",
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fetch: true,
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},
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},
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},
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{
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// tests whether cache prefetches with the do bit
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qname: "do.prefetch.example.org.",
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ttl: 80,
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prefetch: 1,
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verifications: []verification{
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{
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after: 0 * time.Second,
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answer: "do.prefetch.example.org. 80 IN A 127.0.0.1",
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do: true,
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fetch: true,
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},
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{
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after: 73 * time.Second,
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answer: "do.prefetch.example.org. 7 IN A 127.0.0.1",
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do: true,
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fetch: true,
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},
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{
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after: 80 * time.Second,
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answer: "do.prefetch.example.org. 73 IN A 127.0.0.2",
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do: true,
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},
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{
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// Should be 127.0.0.3 as 127.0.0.2 was the prefetch WITH do bit
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after: 80 * time.Second,
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answer: "do.prefetch.example.org. 80 IN A 127.0.0.3",
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fetch: true,
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},
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},
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},
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{
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// tests whether cache prefetches with the cd bit
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qname: "cd.prefetch.example.org.",
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ttl: 80,
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prefetch: 1,
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verifications: []verification{
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{
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after: 0 * time.Second,
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answer: "cd.prefetch.example.org. 80 IN A 127.0.0.1",
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cd: true,
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fetch: true,
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},
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{
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after: 73 * time.Second,
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answer: "cd.prefetch.example.org. 7 IN A 127.0.0.1",
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cd: true,
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fetch: true,
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},
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{
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after: 80 * time.Second,
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answer: "cd.prefetch.example.org. 73 IN A 127.0.0.2",
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cd: true,
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},
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{
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// Should be 127.0.0.3 as 127.0.0.2 was the prefetch WITH cd bit
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after: 80 * time.Second,
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answer: "cd.prefetch.example.org. 80 IN A 127.0.0.3",
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fetch: true,
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},
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},
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},
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}
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t0, err := time.Parse(time.RFC3339, "2018-01-01T14:00:00+00:00")
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if err != nil {
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t.Fatal(err)
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}
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for _, tt := range tests {
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t.Run(tt.qname, func(t *testing.T) {
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fetchc := make(chan struct{}, 1)
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c := New()
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c.Next = prefetchHandler(tt.qname, tt.ttl, fetchc)
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c.prefetch = tt.prefetch
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rec := dnstest.NewRecorder(&test.ResponseWriter{})
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for _, v := range tt.verifications {
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c.now = func() time.Time { return t0.Add(v.after) }
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req := new(dns.Msg)
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req.SetQuestion(tt.qname, dns.TypeA)
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req.CheckingDisabled = v.cd
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req.SetEdns0(512, v.do)
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c.ServeDNS(context.TODO(), rec, req)
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if v.fetch {
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select {
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case <-fetchc:
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// Prefetch handler was called.
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case <-time.After(time.Second):
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t.Fatalf("After %s: want request to trigger a prefetch", v.after)
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}
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}
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if want, got := dns.RcodeSuccess, rec.Rcode; want != got {
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t.Errorf("After %s: want rcode %d, got %d", v.after, want, got)
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}
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if want, got := 1, len(rec.Msg.Answer); want != got {
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t.Errorf("After %s: want %d answer RR, got %d", v.after, want, got)
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}
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if want, got := test.A(v.answer).String(), rec.Msg.Answer[0].String(); want != got {
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t.Errorf("After %s: want answer %s, got %s", v.after, want, got)
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}
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}
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})
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}
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}
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type verification struct {
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after time.Duration
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answer string
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do bool
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cd bool
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// fetch defines whether a request is sent to the next handler.
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fetch bool
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}
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// prefetchHandler is a fake plugin implementation which returns a single A
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// record with the given qname and ttl. The returned IP address starts at
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// 127.0.0.1 and is incremented on every request.
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func prefetchHandler(qname string, ttl int, fetchc chan struct{}) plugin.Handler {
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i := 0
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return plugin.HandlerFunc(func(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
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i++
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m := new(dns.Msg)
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m.SetQuestion(qname, dns.TypeA)
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m.Response = true
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m.Answer = append(m.Answer, test.A(fmt.Sprintf("%s %d IN A 127.0.0.%d", qname, ttl, i)))
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w.WriteMsg(m)
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fetchc <- struct{}{}
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return dns.RcodeSuccess, nil
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})
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}
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