k8s middleware cleanup, testcases, basic SRV (#181)

* Removing unnecessary gitignore pattern

* Updating Makefile to run unittests for subpackages

* Adding Corefile validation to ignore overlapping zones

* Fixing SRV query handling

* Updating README.md now that SRV works

* Fixing debug message, adding code comment

* Clarifying implementation of zone normalization

* "Overlapping zones" is ill-defined. Reimplemented zone overlap/subzone
  checking to contain these functions in k8s middleware and provide
  better code comments explaining the normalization.

* Separate build verbosity from test verbosity

* Cleaning up comments to match repo code style

* Merging warning messages into single message
* Moving function docs to before function declaration

* Adding test cases for k8sclient connector

* Tests cover connector create and setting base url
* Fixed bugs in connector create and setting base url functions

* Updaing README to group and order development work

* Priority focused on achieving functional parity with SkyDNS.

* Adding work items to README and cleaning up formatting

* More README format cleaning

* List formating

* Refactoring k8s API call to allow dependency injection

* Add test cases for data parsing from k8s into dataobject structures

* URL is dependency-injected to allow replacement with a mock http
  server during test execution

* Adding more data validation for JSON parsing tests

* Adding test case for GetResourceList()

* Adding notes about SkyDNS embedded IP and port record names

* Marked test case implemented.

* Fixing formatting for example command.

* Fixing formatting

* Adding notes about Docker image building.

* Adding SkyDNS work item

* Updating TODO list

* Adding name template to Corefile to specify how k8s record names are assembled

* Adding template support for multi-segment zones

* Updating example CoreFile for k8s with template comment

* Misc whitespace cleanup

* Adding SkyDNS naming notes

* Adding namespace filtering to CoreFile config

* Updating example k8sCoreFile to specify namespaces

* Removing unused codepath

* Adding check for valid namespace

* More README TODO restructuring to focus effort

* Adding template validation while parsing CoreFile

* Record name template is considered invalid if it contains a symbol of the form ${bar} where the symbol
  "${bar}" is not an accepted template symbol.

* Refactoring generation of answer records

* Parse typeName out of query string
* Refactor answer record creation as operation over list of ServiceItems

* Moving k8s API caching into SkyDNS equivalency segment

* Adding function to assemble record names from template

* Warning: This commit may be broken. Syncing to get laptop code over to dev machine.

* More todo notes

* Adding comment describing sample test data.

* Update k8sCorefile

* Adding comment

* Adding filtering support for kubernetes "type"

* Required refactoring to support reuse of the StringInSlice function.

* Cleaning up formatting

* Adding note about SkyDNS supporting word "any".

* baseUrl -> baseURL

* Also removed debug statement from core/setup/kubernetes.go

* Fixing test breaking from Url -> URL naming changes

* Changing record name template language ${...} -> {...}

* Fix formatting with go fmt

* Updating all k8sclient data getters to return error value

* Adding error message to k8sclient data accessors

* Cleaning up setup for kubernetes

* Removed verbose nils in initial k8s middleware instance
* Set reasonable defaults if CoreFile has no parameters in the
kubernetes block. (k8s endpoint, and name template)

* Formatting cleanup -- go fmt

1 files changed, 48 insertions, 0 deletions

diff --git a/middleware/kubernetes/subzone.go b/middleware/kubernetes/subzone.go
new file mode 100644
index 000000000..48efba472
--- /dev/null
+++ b/middleware/kubernetes/subzone.go
@@ -0,0 +1,48 @@
+package kubernetes
+
+import (
+	"fmt"
+
+	"github.com/miekg/dns"
+)
+
+// NormalizeZoneList filters the zones argument to remove
+// array items that conflict with other items in zones.
+// For example, providing the following zones array:
+//    [ "a.b.c", "b.c", "a", "e.d.f", "a.b" ]
+// Returns:
+//    [ "a.b.c", "a", "e.d.f", "a.b" ]
+// Zones filted out:
+//    - "b.c" because "a.b.c" and "b.c" share the common top
+//      level "b.c". First listed zone wins if there is a conflict.
+//
+// Note: This may prove to be too restrictive in practice.
+//       Need to find counter-example use-cases.
+func NormalizeZoneList(zones []string) []string {
+	filteredZones := []string{}
+
+	for _, z := range zones {
+		zoneConflict, _ := subzoneConflict(filteredZones, z)
+		if zoneConflict {
+			fmt.Printf("[WARN] new zone '%v' from Corefile conflicts with existing zones: %v\n        Ignoring zone '%v'\n", z, filteredZones, z)
+		} else {
+			filteredZones = append(filteredZones, z)
+		}
+	}
+
+	return filteredZones
+}
+
+// subzoneConflict returns true if name is a child or parent zone of
+// any element in zones. If conflicts exist, return the conflicting zones.
+func subzoneConflict(zones []string, name string) (bool, []string) {
+	conflicts := []string{}
+
+	for _, z := range zones {
+		if dns.IsSubDomain(z, name) || dns.IsSubDomain(name, z) {
+			conflicts = append(conflicts, z)
+		}
+	}
+
+	return (len(conflicts) != 0), conflicts
+}