diff options
| -rw-r--r-- | plugin/cache/cache.go | 4 | ||||
| -rw-r--r-- | plugin/cache/cache_test.go | 100 | ||||
| -rw-r--r-- | plugin/cache/handler.go | 6 |
3 files changed, 107 insertions, 3 deletions
diff --git a/plugin/cache/cache.go b/plugin/cache/cache.go index 6b50c51cc..9988d9c70 100644 --- a/plugin/cache/cache.go +++ b/plugin/cache/cache.go @@ -210,6 +210,10 @@ func (w *ResponseWriter) set(m *dns.Msg, key uint64, mt response.Type, duration case response.NoError, response.Delegation: i := newItem(m, w.now(), duration) w.pcache.Add(key, i) + // when pre-fetching, remove the negative cache entry if it exists + if w.prefetch { + w.ncache.Remove(key) + } case response.NameError, response.NoData, response.ServerError: i := newItem(m, w.now(), duration) diff --git a/plugin/cache/cache_test.go b/plugin/cache/cache_test.go index 138458c8f..b3ed6d6cc 100644 --- a/plugin/cache/cache_test.go +++ b/plugin/cache/cache_test.go @@ -296,6 +296,92 @@ func TestServeFromStaleCache(t *testing.T) { } } +func TestNegativeStaleMaskingPositiveCache(t *testing.T) { + c := New() + c.staleUpTo = time.Minute * 10 + c.Next = nxDomainBackend(60) + + req := new(dns.Msg) + qname := "cached.org." + req.SetQuestion(qname, dns.TypeA) + ctx := context.TODO() + + // Add an entry to Negative Cache": cached.org. = NXDOMAIN + expectedResult := dns.RcodeNameError + if ret, _ := c.ServeDNS(ctx, &test.ResponseWriter{}, req); ret != expectedResult { + t.Errorf("Test 0 Negative Cache Population: expecting %v; got %v", expectedResult, ret) + } + + // Confirm item was added to negative cache and not to positive cache + if c.ncache.Len() == 0 { + t.Errorf("Test 0 Negative Cache Population: item not added to negative cache") + } + if c.pcache.Len() != 0 { + t.Errorf("Test 0 Negative Cache Population: item added to positive cache") + } + + // Set the Backend to return non-cachable errors only + c.Next = plugin.HandlerFunc(func(context.Context, dns.ResponseWriter, *dns.Msg) (int, error) { + return 255, nil // Below, a 255 means we tried querying upstream. + }) + + // Confirm we get the NXDOMAIN from the negative cache, not the error form the backend + rec := dnstest.NewRecorder(&test.ResponseWriter{}) + req = new(dns.Msg) + req.SetQuestion(qname, dns.TypeA) + expectedResult = dns.RcodeNameError + if c.ServeDNS(ctx, rec, req); rec.Rcode != expectedResult { + t.Errorf("Test 1 NXDOMAIN from Negative Cache: expecting %v; got %v", expectedResult, rec.Rcode) + } + + // Jump into the future beyond when the negative cache item would go stale + // but before the item goes rotten (exceeds serve stale time) + c.now = func() time.Time { return time.Now().Add(time.Duration(5) * time.Minute) } + + // Set Backend to return a positive NOERROR + A record response + c.Next = BackendHandler() + + // Make a query for the stale cache item + rec = dnstest.NewRecorder(&test.ResponseWriter{}) + req = new(dns.Msg) + req.SetQuestion(qname, dns.TypeA) + expectedResult = dns.RcodeNameError + if c.ServeDNS(ctx, rec, req); rec.Rcode != expectedResult { + t.Errorf("Test 2 NOERROR from Backend: expecting %v; got %v", expectedResult, rec.Rcode) + } + + // Confirm that prefetch removes the negative cache item. + waitFor := 3 + for i := 1; i <= waitFor; i++ { + if c.ncache.Len() != 0 { + if i == waitFor { + t.Errorf("Test 2 NOERROR from Backend: item still exists in negative cache") + } + time.Sleep(time.Second) + continue + } + } + + // Confirm that positive cache has the item + if c.pcache.Len() != 1 { + t.Errorf("Test 2 NOERROR from Backend: item missing from positive cache") + } + + // Backend - Give error only + c.Next = plugin.HandlerFunc(func(context.Context, dns.ResponseWriter, *dns.Msg) (int, error) { + return 255, nil // Below, a 255 means we tried querying upstream. + }) + + // Query again, expect that positive cache entry is not masked by a negative cache entry + rec = dnstest.NewRecorder(&test.ResponseWriter{}) + req = new(dns.Msg) + req.SetQuestion(qname, dns.TypeA) + expectedResult = dns.RcodeSuccess + if ret, _ := c.ServeDNS(ctx, rec, req); ret != expectedResult { + t.Errorf("Test 3 NOERROR from Cache: expecting %v; got %v", expectedResult, ret) + } +} + func BenchmarkCacheResponse(b *testing.B) { c := New() c.prefetch = 1 @@ -334,6 +420,20 @@ func BackendHandler() plugin.Handler { }) } +func nxDomainBackend(ttl int) plugin.Handler { + return plugin.HandlerFunc(func(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) { + m := new(dns.Msg) + m.SetReply(r) + m.Response, m.RecursionAvailable = true, true + + m.Ns = []dns.RR{test.SOA(fmt.Sprintf("example.org. %d IN SOA sns.dns.icann.org. noc.dns.icann.org. 2016082540 7200 3600 1209600 3600", ttl))} + + m.MsgHdr.Rcode = dns.RcodeNameError + w.WriteMsg(m) + return dns.RcodeNameError, nil + }) +} + func ttlBackend(ttl int) plugin.Handler { return plugin.HandlerFunc(func(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) { m := new(dns.Msg) diff --git a/plugin/cache/handler.go b/plugin/cache/handler.go index 2a64f11e4..0adc81576 100644 --- a/plugin/cache/handler.go +++ b/plugin/cache/handler.go @@ -31,7 +31,7 @@ func (c *Cache) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) if i != nil { ttl = i.ttl(now) } - if i == nil || -ttl >= int(c.staleUpTo.Seconds()) { + if i == nil { crr := &ResponseWriter{ResponseWriter: w, Cache: c, state: state, server: server} return plugin.NextOrFailure(c.Name(), c.Next, ctx, crr, r) } @@ -104,15 +104,15 @@ func (c *Cache) getIgnoreTTL(now time.Time, state request.Request, server string ttl := i.(*item).ttl(now) if ttl > 0 || (c.staleUpTo > 0 && -ttl < int(c.staleUpTo.Seconds())) { cacheHits.WithLabelValues(server, Denial).Inc() + return i.(*item) } - return i.(*item) } if i, ok := c.pcache.Get(k); ok { ttl := i.(*item).ttl(now) if ttl > 0 || (c.staleUpTo > 0 && -ttl < int(c.staleUpTo.Seconds())) { cacheHits.WithLabelValues(server, Success).Inc() + return i.(*item) } - return i.(*item) } cacheMisses.WithLabelValues(server).Inc() return nil |