Pull request 1943: 6046 Local PTR

Merge in DNS/adguard-home from 6046-local-ptr to master

Updates #6046.

Squashed commit of the following:

commit 3e90815f29173d2f68970278bd7b1b29cc0a4465
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Jul 27 18:17:41 2023 +0300

    all: log changes

commit 7639f6f785670c15911fb3ca20abeb4e2b8f8582
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Jul 27 17:40:49 2023 +0300

    all: fix 0 ttl ptr

internal/rdns/rdns.go

@@ -101,6 +101,8 @@ func (r *Default) Process(ip netip.Addr) (host string, changed bool) {
 		log.Debug("rdns: cache: adding item %q: %s", ip, err)
 	}
 
+	// TODO(e.burkov):  The name doesn't change if it's neither stored in cache
+	// nor resolved successfully.  Is it correct?
 	return host, fromCache == "" || host != fromCache
 }
 

internal/rdns/rdns_test.go

@@ -25,11 +25,6 @@ func TestDefault_Process(t *testing.T) {
 	localRevAddr1, err := netutil.IPToReversedAddr(localIP.AsSlice())
 	require.NoError(t, err)
 
-	config := &rdns.Config{
-		CacheSize: 100,
-		CacheTTL:  time.Hour,
-	}
-
 	testCases := []struct {
 		name string
 		addr netip.Addr
@@ -60,21 +55,21 @@ func TestDefault_Process(t *testing.T) {
 
 				switch ip {
 				case ip1:
-					return revAddr1, 0, nil
+					return revAddr1, time.Hour, nil
 				case ip2:
-					return revAddr2, 0, nil
+					return revAddr2, time.Hour, nil
 				case localIP:
-					return localRevAddr1, 0, nil
+					return localRevAddr1, time.Hour, nil
 				default:
-					return "", 0, nil
+					return "", time.Hour, nil
 				}
 			}
-			exchanger := &aghtest.Exchanger{
-				OnExchange: onExchange,
-			}
 
-			config.Exchanger = exchanger
-			r := rdns.New(config)
+			r := rdns.New(&rdns.Config{
+				CacheSize: 100,
+				CacheTTL:  time.Hour,
+				Exchanger: &aghtest.Exchanger{OnExchange: onExchange},
+			})
 
 			got, changed := r.Process(tc.addr)
 			require.True(t, changed)
@@ -90,4 +85,40 @@ func TestDefault_Process(t *testing.T) {
 			assert.Equal(t, 1, hit)
 		})
 	}
+
+	t.Run("zero_ttl", func(t *testing.T) {
+		const cacheTTL = time.Second / 2
+
+		zeroTTLExchanger := &aghtest.Exchanger{
+			OnExchange: func(ip netip.Addr) (host string, ttl time.Duration, err error) {
+				return revAddr1, 0, nil
+			},
+		}
+
+		r := rdns.New(&rdns.Config{
+			CacheSize: 1,
+			CacheTTL:  cacheTTL,
+			Exchanger: zeroTTLExchanger,
+		})
+
+		got, changed := r.Process(ip1)
+		require.True(t, changed)
+		assert.Equal(t, revAddr1, got)
+
+		zeroTTLExchanger.OnExchange = func(ip netip.Addr) (host string, ttl time.Duration, err error) {
+			return revAddr2, time.Hour, nil
+		}
+
+		require.EventuallyWithT(t, func(t *assert.CollectT) {
+			got, changed = r.Process(ip1)
+			assert.True(t, changed)
+			assert.Equal(t, revAddr2, got)
+		}, 2*cacheTTL, time.Millisecond*100)
+
+		assert.Never(t, func() (changed bool) {
+			_, changed = r.Process(ip1)
+
+			return changed
+		}, 2*cacheTTL, time.Millisecond*100)
+	})
 }