Implement chaos middleware

This allows for CH TXT queries that return some information about
the server and/or the authors (or whatever you put in there).

core/setup/chaos.go

@@ -0,0 +1,45 @@
+package setup
+
+import (
+	"github.com/miekg/coredns/middleware"
+	"github.com/miekg/coredns/middleware/chaos"
+)
+
+// Chaos configures a new Chaos middleware instance.
+func Chaos(c *Controller) (middleware.Middleware, error) {
+	version, authors, err := chaosParse(c)
+	if err != nil {
+		return nil, err
+	}
+
+	return func(next middleware.Handler) middleware.Handler {
+		return chaos.Chaos{
+			Next:    next,
+			Version: version,
+			Authors: authors,
+		}
+	}, nil
+}
+
+func chaosParse(c *Controller) (string, map[string]bool, error) {
+	version := ""
+	authors := make(map[string]bool)
+
+	for c.Next() {
+		args := c.RemainingArgs()
+		if len(args) == 0 {
+			return defaultVersion, nil, nil
+		}
+		if len(args) == 1 {
+			return args[0], nil, nil
+		}
+		version = args[0]
+		for _, a := range args[1:] {
+			authors[a] = true
+		}
+		return version, authors, nil
+	}
+	return version, authors, nil
+}
+
+const defaultVersion = "CoreDNS"