Remove the word middleware (#1067)

* Rename middleware to plugin

first pass; mostly used 'sed', few spots where I manually changed
text.

This still builds a coredns binary.

* fmt error

* Rename AddMiddleware to AddPlugin

* Readd AddMiddleware to remain backwards compat

1 files changed, 112 insertions, 0 deletions

diff --git a/plugin/kubernetes/parse.go b/plugin/kubernetes/parse.go
new file mode 100644
index 000000000..a66e77699
--- /dev/null
+++ b/plugin/kubernetes/parse.go
@@ -0,0 +1,112 @@
+package kubernetes
+
+import (
+	"github.com/coredns/coredns/plugin/pkg/dnsutil"
+	"github.com/coredns/coredns/request"
+
+	"github.com/miekg/dns"
+)
+
+type recordRequest struct {
+	// The named port from the kubernetes DNS spec, this is the service part (think _https) from a well formed
+	// SRV record.
+	port string
+	// The protocol is usually _udp or _tcp (if set), and comes from the protocol part of a well formed
+	// SRV record.
+	protocol string
+	endpoint string
+	// The servicename used in Kubernetes.
+	service string
+	// The namespace used in Kubernetes.
+	namespace string
+	// A each name can be for a pod or a service, here we track what we've seen, either "pod" or "service".
+	podOrSvc string
+}
+
+// parseRequest parses the qname to find all the elements we need for querying k8s. Anything
+// that is not parsed will have the wildcard "*" value (except r.endpoint).
+// Potential underscores are stripped from _port and _protocol.
+func parseRequest(state request.Request) (r recordRequest, err error) {
+	// 3 Possible cases:
+	// 1. _port._protocol.service.namespace.pod|svc.zone
+	// 2. (endpoint): endpoint.service.namespace.pod|svc.zone
+	// 3. (service): service.namespace.pod|svc.zone
+	//
+	// Federations are handled in the federation plugin. And aren't parsed here.
+
+	base, _ := dnsutil.TrimZone(state.Name(), state.Zone)
+	segs := dns.SplitDomainName(base)
+
+	r.port = "*"
+	r.protocol = "*"
+	r.service = "*"
+	r.namespace = "*"
+	// r.endpoint is the odd one out, we need to know if it has been set or not. If it is
+	// empty we should skip the endpoint check in k.get(). Hence we cannot set if to "*".
+
+	// start at the right and fill out recordRequest with the bits we find, so we look for
+	// pod|svc.namespace.service and then either
+	// * endpoint
+	// *_protocol._port
+
+	last := len(segs) - 1
+	if last < 0 {
+		return r, nil
+	}
+	r.podOrSvc = segs[last]
+	if r.podOrSvc != Pod && r.podOrSvc != Svc {
+		return r, errInvalidRequest
+	}
+	last--
+	if last < 0 {
+		return r, nil
+	}
+
+	r.namespace = segs[last]
+	last--
+	if last < 0 {
+		return r, nil
+	}
+
+	r.service = segs[last]
+	last--
+	if last < 0 {
+		return r, nil
+	}
+
+	// Because of ambiquity we check the labels left: 1: an endpoint. 2: port and protocol.
+	// Anything else is a query that is too long to answer and can safely be delegated to return an nxdomain.
+	switch last {
+
+	case 0: // endpoint only
+		r.endpoint = segs[last]
+	case 1: // service and port
+		r.protocol = stripUnderscore(segs[last])
+		r.port = stripUnderscore(segs[last-1])
+
+	default: // too long
+		return r, errInvalidRequest
+	}
+
+	return r, nil
+}
+
+// stripUnderscore removes a prefixed underscore from s.
+func stripUnderscore(s string) string {
+	if s[0] != '_' {
+		return s
+	}
+	return s[1:]
+}
+
+// String return a string representation of r, it just returns all fields concatenated with dots.
+// This is mostly used in tests.
+func (r recordRequest) String() string {
+	s := r.port
+	s += "." + r.protocol
+	s += "." + r.endpoint
+	s += "." + r.service
+	s += "." + r.namespace
+	s += "." + r.podOrSvc
+	return s
+}