mw/federation: add federation back as separate mw for k8s (#929)

* mw/federaration

This PR add the federation back as a middleware to keep it more
contained from the main kubernetes code.

It also makes parseRequest less import and pushes this functionlity down
in the k.Entries. This minimizes (or tries to) the importance for the
qtype in the query. In the end the qtype checking should only happen
in ServeDNS - but for k8s this might proof difficult.

Numerous other cleanup in code and kubernetes tests.

* up test coverage

1 files changed, 81 insertions, 0 deletions

diff --git a/middleware/federation/setup.go b/middleware/federation/setup.go
new file mode 100644
index 000000000..9a60fcc3d
--- /dev/null
+++ b/middleware/federation/setup.go
@@ -0,0 +1,81 @@
+package federation
+
+import (
+	"fmt"
+
+	"github.com/coredns/coredns/core/dnsserver"
+	"github.com/coredns/coredns/middleware"
+	"github.com/coredns/coredns/middleware/kubernetes"
+	"github.com/miekg/dns"
+
+	"github.com/mholt/caddy"
+)
+
+func init() {
+	caddy.RegisterPlugin("federation", caddy.Plugin{
+		ServerType: "dns",
+		Action:     setup,
+	})
+}
+
+func setup(c *caddy.Controller) error {
+	fed, err := federationParse(c)
+	if err != nil {
+		return middleware.Error("federation", err)
+	}
+
+	// Do this in OnStartup, so all middleware has been initialized.
+	c.OnStartup(func() error {
+		m := dnsserver.GetConfig(c).GetHandler("kubernetes")
+		if m == nil {
+			return nil
+		}
+		if x, ok := m.(kubernetes.Kubernetes); ok {
+			fed.Federations = x.Federations
+		}
+		return nil
+	})
+
+	dnsserver.GetConfig(c).AddMiddleware(func(next middleware.Handler) middleware.Handler {
+		fed.Next = next
+		return nil
+	})
+
+	return nil
+}
+
+func federationParse(c *caddy.Controller) (*Federation, error) {
+	fed := New()
+
+	for c.Next() {
+		// federation [zones..]
+		origins := make([]string, len(c.ServerBlockKeys))
+		copy(origins, c.ServerBlockKeys)
+
+		for c.NextBlock() {
+			x := c.Val()
+			switch c.Val() {
+			default:
+				args := c.RemainingArgs()
+				if len(args) != 1 {
+					return fed, fmt.Errorf("need two arguments for federation: %q", args)
+				}
+				fed.f[x] = dns.Fqdn(args[0])
+			}
+		}
+
+		for i := range origins {
+			origins[i] = middleware.Host(origins[i]).Normalize()
+		}
+
+		fed.zones = origins
+
+		if len(fed.f) == 0 {
+			return fed, fmt.Errorf("at least one name to zone federation expected")
+		}
+
+		return fed, nil
+	}
+
+	return fed, nil
+}