plugin/cache: Add cache disable option (#5540)

* add cache disable options

Signed-off-by: Chris O'Haver <cohaver@infoblox.com>

6 files changed, 158 insertions, 3 deletions

diff --git a/plugin/cache/README.md b/plugin/cache/README.md
index 9322af16c..602072656 100644
--- a/plugin/cache/README.md
+++ b/plugin/cache/README.md
@@ -39,6 +39,7 @@ cache [TTL] [ZONES...] {
     prefetch AMOUNT [[DURATION] [PERCENTAGE%]]
     serve_stale [DURATION] [REFRESH_MODE]
     servfail DURATION
+    disable success|denial [ZONES...]
 }
 ~~~
 
@@ -67,6 +68,8 @@ cache [TTL] [ZONES...] {
 * `servfail` cache SERVFAIL responses for **DURATION**.  Setting **DURATION** to 0 will disable caching of SERVFAIL
   responses.  If this option is not set, SERVFAIL responses will be cached for 5 seconds.  **DURATION** may not be
   greater than 5 minutes.
+* `disable`  disable the success or denial cache for the listed **ZONES**.  If no **ZONES** are given, the specified
+  cache will be disabled for all zones.
 
 ## Capacity and Eviction
 
@@ -124,3 +127,13 @@ example.org {
     }
 }
 ~~~
+
+Enable caching for `example.org`, but do not cache denials in `sub.example.org`:
+
+~~~ corefile
+example.org {
+    cache {
+        disable denial sub.example.org
+    }
+}
+~~~
\ No newline at end of file
diff --git a/plugin/cache/cache.go b/plugin/cache/cache.go
index d1989f35b..bfd8c1576 100644
--- a/plugin/cache/cache.go
+++ b/plugin/cache/cache.go
@@ -43,6 +43,10 @@ type Cache struct {
 	staleUpTo   time.Duration
 	verifyStale bool
 
+	// Positive/negative zone exceptions
+	pexcept []string
+	nexcept []string
+
 	// Testing.
 	now func() time.Time
 }
@@ -117,6 +121,8 @@ type ResponseWriter struct {
 
 	wildcardFunc func() string // function to retrieve wildcard name that synthesized the result.
 
+	pexcept []string // positive zone exceptions
+	nexcept []string // negative zone exceptions
 }
 
 // newPrefetchResponseWriter returns a Cache ResponseWriter to be used in
@@ -204,6 +210,10 @@ func (w *ResponseWriter) set(m *dns.Msg, key uint64, mt response.Type, duration
 	// and key is valid
 	switch mt {
 	case response.NoError, response.Delegation:
+		if plugin.Zones(w.pexcept).Matches(m.Question[0].Name) != "" {
+			// zone is in exception list, do not cache
+			return
+		}
 		i := newItem(m, w.now(), duration)
 		if w.wildcardFunc != nil {
 			i.wildcard = w.wildcardFunc()
@@ -217,6 +227,10 @@ func (w *ResponseWriter) set(m *dns.Msg, key uint64, mt response.Type, duration
 		}
 
 	case response.NameError, response.NoData, response.ServerError:
+		if plugin.Zones(w.nexcept).Matches(m.Question[0].Name) != "" {
+			// zone is in exception list, do not cache
+			return
+		}
 		i := newItem(m, w.now(), duration)
 		if w.wildcardFunc != nil {
 			i.wildcard = w.wildcardFunc()
diff --git a/plugin/cache/cache_test.go b/plugin/cache/cache_test.go
index 851507a4d..0328c8411 100644
--- a/plugin/cache/cache_test.go
+++ b/plugin/cache/cache_test.go
@@ -17,8 +17,8 @@ import (
 )
 
 type cacheTestCase struct {
-	test.Case
-	in                 test.Case
+	test.Case                    // the expected message coming "out" of cache
+	in                 test.Case // the test message going "in" to cache
 	AuthenticatedData  bool
 	RecursionAvailable bool
 	Truncated          bool
@@ -163,6 +163,62 @@ var cacheTestCases = []cacheTestCase{
 		},
 		shouldCache: true,
 	},
+	{
+		in: test.Case{
+			Rcode: dns.RcodeNameError,
+			Qname: "neg-disabled.example.org.", Qtype: dns.TypeA,
+			Ns: []dns.RR{
+				test.SOA("example.org. 3600 IN	SOA	sns.dns.icann.org. noc.dns.icann.org. 2016082540 7200 3600 1209600 3600"),
+			},
+		},
+		Case:        test.Case{},
+		shouldCache: false,
+	},
+	{
+		in: test.Case{
+			Rcode: dns.RcodeSuccess,
+			Qname: "pos-disabled.example.org.", Qtype: dns.TypeA,
+			Answer: []dns.RR{
+				test.A("pos-disabled.example.org. 3600 IN	A	127.0.0.1"),
+			},
+		},
+		Case:        test.Case{},
+		shouldCache: false,
+	},
+	{
+		in: test.Case{
+			Rcode: dns.RcodeNameError,
+			Qname: "pos-disabled.example.org.", Qtype: dns.TypeA,
+			Ns: []dns.RR{
+				test.SOA("example.org. 3600 IN	SOA	sns.dns.icann.org. noc.dns.icann.org. 2016082540 7200 3600 1209600 3600"),
+			},
+		},
+		Case: test.Case{
+			Rcode: dns.RcodeNameError,
+			Qname: "pos-disabled.example.org.", Qtype: dns.TypeA,
+			Ns: []dns.RR{
+				test.SOA("example.org. 3600 IN	SOA	sns.dns.icann.org. noc.dns.icann.org. 2016082540 7200 3600 1209600 3600"),
+			},
+		},
+		shouldCache: true,
+	},
+	{
+		in: test.Case{
+			Rcode: dns.RcodeSuccess,
+			Qname: "neg-disabled.example.org.", Qtype: dns.TypeA,
+			Answer: []dns.RR{
+				test.A("neg-disabled.example.org. 3600 IN	A	127.0.0.1"),
+			},
+		},
+		Case: test.Case{
+			Rcode: dns.RcodeSuccess,
+			Qname: "neg-disabled.example.org.", Qtype: dns.TypeA,
+			Answer: []dns.RR{
+				test.A("neg-disabled.example.org. 3600 IN	A	127.0.0.1"),
+			},
+		},
+		shouldCache: true,
+	},
 }
 
 func cacheMsg(m *dns.Msg, tc cacheTestCase) *dns.Msg {
@@ -183,6 +239,9 @@ func newTestCache(ttl time.Duration) (*Cache, *ResponseWriter) {
 	c.nttl = ttl
 
 	crr := &ResponseWriter{ResponseWriter: nil, Cache: c}
+	crr.nexcept = []string{"neg-disabled.example.org."}
+	crr.pexcept = []string{"pos-disabled.example.org."}
+
 	return c, crr
 }
 
diff --git a/plugin/cache/handler.go b/plugin/cache/handler.go
index 69ec4928d..3d2f43904 100644
--- a/plugin/cache/handler.go
+++ b/plugin/cache/handler.go
@@ -38,7 +38,8 @@ func (c *Cache) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
 	ttl := 0
 	i := c.getIgnoreTTL(now, state, server)
 	if i == nil {
-		crr := &ResponseWriter{ResponseWriter: w, Cache: c, state: state, server: server, do: do, ad: ad, wildcardFunc: wildcardFunc(ctx)}
+		crr := &ResponseWriter{ResponseWriter: w, Cache: c, state: state, server: server, do: do, ad: ad,
+			nexcept: c.nexcept, pexcept: c.pexcept, wildcardFunc: wildcardFunc(ctx)}
 		return c.doRefresh(ctx, state, crr)
 	}
 	ttl = i.ttl(now)
diff --git a/plugin/cache/setup.go b/plugin/cache/setup.go
index aa487105c..a1ce255a9 100644
--- a/plugin/cache/setup.go
+++ b/plugin/cache/setup.go
@@ -205,6 +205,35 @@ func cacheParse(c *caddy.Controller) (*Cache, error) {
 					return nil, errors.New("caching SERVFAIL responses over 5 minutes is not permitted")
 				}
 				ca.failttl = d
+			case "disable":
+				// disable [success|denial] [zones]...
+				args := c.RemainingArgs()
+				if len(args) < 1 {
+					return nil, c.ArgErr()
+				}
+
+				var zones []string
+				if len(args) > 1 {
+					for _, z := range args[1:] { // args[1:] define the list of zones to disable
+						nz := plugin.Name(z).Normalize()
+						if nz == "" {
+							return nil, fmt.Errorf("invalid disabled zone: %s", z)
+						}
+						zones = append(zones, nz)
+					}
+				} else {
+					// if no zones specified, default to root
+					zones = []string{"."}
+				}
+
+				switch args[0] { // args[0] defines which cache to disable
+				case Denial:
+					ca.nexcept = zones
+				case Success:
+					ca.pexcept = zones
+				default:
+					return nil, fmt.Errorf("cache type for disable must be %q or %q", Success, Denial)
+				}
 			default:
 				return nil, c.ArgErr()
 			}
diff --git a/plugin/cache/setup_test.go b/plugin/cache/setup_test.go
index 5e684c510..5d8b9653c 100644
--- a/plugin/cache/setup_test.go
+++ b/plugin/cache/setup_test.go
@@ -192,3 +192,42 @@ func TestServfail(t *testing.T) {
 		}
 	}
 }
+
+func TestDisable(t *testing.T) {
+	tests := []struct {
+		input     string
+		shouldErr bool
+		nexcept   []string
+		pexcept   []string
+	}{
+		// positive
+		{"disable denial example.com example.org", false, []string{"example.com.", "example.org."}, nil},
+		{"disable success example.com example.org", false, nil, []string{"example.com.", "example.org."}},
+		{"disable denial", false, []string{"."}, nil},
+		{"disable success", false, nil, []string{"."}},
+		{"disable denial example.com example.org\ndisable success example.com example.org", false,
+			[]string{"example.com.", "example.org."}, []string{"example.com.", "example.org."}},
+		// negative
+		{"disable invalid example.com example.org", true, nil, nil},
+	}
+	for i, test := range tests {
+		c := caddy.NewTestController("dns", fmt.Sprintf("cache {\n%s\n}", test.input))
+		ca, err := cacheParse(c)
+		if test.shouldErr && err == nil {
+			t.Errorf("Test %v: Expected error but found nil", i)
+			continue
+		} else if !test.shouldErr && err != nil {
+			t.Errorf("Test %v: Expected no error but found error: %v", i, err)
+			continue
+		}
+		if test.shouldErr {
+			continue
+		}
+		if fmt.Sprintf("%v", test.nexcept) != fmt.Sprintf("%v", ca.nexcept) {
+			t.Errorf("Test %v: Expected %v but got: %v", i, test.nexcept, ca.nexcept)
+		}
+		if fmt.Sprintf("%v", test.pexcept) != fmt.Sprintf("%v", ca.pexcept) {
+			t.Errorf("Test %v: Expected %v but got: %v", i, test.pexcept, ca.pexcept)
+		}
+	}
+}