plugin/view: Advanced routing interface and new 'view' plugin (#5538)

* introduce new interface "dnsserver.Viewer", that allows a plugin implementing it to decide if a query should be routed into its server block.
* add new plugin "view", that uses the new interface to enable a user to define expression based conditions that must be met for a query to be routed to its server block.

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

1 files changed, 163 insertions, 0 deletions

diff --git a/test/view_test.go b/test/view_test.go
new file mode 100644
index 000000000..f68595380
--- /dev/null
+++ b/test/view_test.go
@@ -0,0 +1,163 @@
+package test
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/coredns/coredns/plugin/test"
+
+	"github.com/miekg/dns"
+)
+
+func TestView(t *testing.T) {
+	// Hack to get an available port - We spin up a temporary dummy coredns on :0 to get the port number, then we re-use
+	// that one port consistently across all server blocks.
+	corefile := `example.org:0 {
+		erratic
+	}`
+	tmp, addr, _, err := CoreDNSServerAndPorts(corefile)
+	if err != nil {
+		t.Fatalf("Could not get CoreDNS serving instance: %s", err)
+	}
+
+	port := addr[strings.LastIndex(addr, ":")+1:]
+
+	// Corefile with test views
+	corefile = `
+      # split-type config: splits quries for A/AAAA into separate views
+      split-type:` + port + ` {
+		view test-view-a {
+          expr type() == 'A'
+	    }
+        hosts {
+          1.2.3.4 test.split-type
+        }
+      }
+      split-type:` + port + ` {
+		view test-view-aaaa {
+          expr type() == 'AAAA'
+	    }
+        hosts {
+          1:2:3::4 test.split-type
+        }
+      }
+
+      # split-name config: splits queries into separate views based on first label in query name ("one", "two")
+      split-name:` + port + ` {
+		view test-view-1 {
+          expr name() matches '^one\\..*\\.split-name\\.$'
+	    }
+        hosts {
+          1.1.1.1 one.test.split-name one.test.test.test.split-name
+        }
+      }
+      split-name:` + port + ` {
+		view test-view-2 {
+          expr name() matches '^two\\..*\\.split-name\\.$'
+	    }
+        hosts {
+          2.2.2.2 two.test.split-name two.test.test.test.split-name
+        }
+      }
+      split-name:` + port + ` {
+        hosts {
+          3.3.3.3 default.test.split-name
+        }
+      }
+
+     # metadata config: verifies that metadata is properly collected by the server,
+     # and that metadata function correctly looks up the value of the metadata.
+     metadata:` + port + ` {
+       metadata
+       view test-view-meta1 {
+         # This is never true
+         expr metadata('view/name') == 'not-the-view-name'
+	   }
+       hosts {
+         1.1.1.1 test.metadata
+       }
+     }
+     metadata:` + port + ` {
+       view test-view-meta2 {
+         # This is never true. The metadata plugin is not enabled in this server block so the metadata function returns
+         # an empty string
+         expr metadata('view/name') == 'test-view-meta2'
+	   }
+       hosts {
+         2.2.2.2 test.metadata
+       }
+     }
+     metadata:` + port + ` {
+       metadata
+       view test-view-meta3 {
+         # This is always true.  Queries in the zone 'metadata.' should always be served using this view.
+         expr metadata('view/name') == 'test-view-meta3'
+	   }
+       hosts {
+         2.2.2.2 test.metadata
+       }
+     }
+     metadata:` + port + ` {
+       # This block should never be reached since the prior view in the same zone is always true
+       hosts {
+         3.3.3.3 test.metadata
+       }
+     }
+    `
+
+	i, addr, _, err := CoreDNSServerAndPorts(corefile)
+	if err != nil {
+		t.Fatalf("Could not get CoreDNS serving instance: %s", err)
+	}
+	// there are multiple sever blocks, but they are all on the same port, so it's a single server instance to stop
+	defer i.Stop()
+	// stop the temporary instance before starting tests.
+	tmp.Stop()
+
+	viewTest(t, "split-type A", addr, "test.split-type.", dns.TypeA, dns.RcodeSuccess,
+		[]dns.RR{test.A("test.split-type.	303	IN	A	1.2.3.4")})
+
+	viewTest(t, "split-type AAAA", addr, "test.split-type.", dns.TypeAAAA, dns.RcodeSuccess,
+		[]dns.RR{test.AAAA("test.split-type.	303	IN	AAAA	1:2:3::4")})
+
+	viewTest(t, "split-name one.test.test.test.split-name", addr, "one.test.test.test.split-name.", dns.TypeA, dns.RcodeSuccess,
+		[]dns.RR{test.A("one.test.test.test.split-name.	303	IN	A	1.1.1.1")})
+
+	viewTest(t, "split-name one.test.split-name", addr, "one.test.split-name.", dns.TypeA, dns.RcodeSuccess,
+		[]dns.RR{test.A("one.test.split-name.	303	IN	A	1.1.1.1")})
+
+	viewTest(t, "split-name two.test.test.test.split-name", addr, "two.test.test.test.split-name.", dns.TypeA, dns.RcodeSuccess,
+		[]dns.RR{test.A("two.test.test.test.split-name.	303	IN	A	2.2.2.2")})
+
+	viewTest(t, "split-name two.test.split-name", addr, "two.test.split-name.", dns.TypeA, dns.RcodeSuccess,
+		[]dns.RR{test.A("two.test.split-name.	303	IN	A	2.2.2.2")})
+
+	viewTest(t, "split-name default.test.split-name", addr, "default.test.split-name.", dns.TypeA, dns.RcodeSuccess,
+		[]dns.RR{test.A("default.test.split-name.	303	IN	A	3.3.3.3")})
+
+	viewTest(t, "metadata test.metadata", addr, "test.metadata.", dns.TypeA, dns.RcodeSuccess,
+		[]dns.RR{test.A("test.metadata.	303	IN	A	2.2.2.2")})
+}
+
+func viewTest(t *testing.T, testName, addr, qname string, qtype uint16, expectRcode int, expectAnswers []dns.RR) {
+	t.Run(testName, func(t *testing.T) {
+		m := new(dns.Msg)
+
+		m.SetQuestion(qname, qtype)
+		resp, err := dns.Exchange(m, addr)
+		if err != nil {
+			t.Fatalf("Expected to receive reply, but didn't: %s", err)
+		}
+
+		tc := test.Case{
+			Qname: qname, Qtype: qtype,
+			Rcode:  expectRcode,
+			Answer: expectAnswers,
+		}
+
+		err = test.SortAndCheck(resp, tc)
+		if err != nil {
+			t.Error(err)
+		}
+	})
+}