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

3 files changed, 291 insertions, 0 deletions

diff --git a/plugin/pkg/response/classify.go b/plugin/pkg/response/classify.go
new file mode 100644
index 000000000..2e705cb0b
--- /dev/null
+++ b/plugin/pkg/response/classify.go
@@ -0,0 +1,61 @@
+package response
+
+import "fmt"
+
+// Class holds sets of Types
+type Class int
+
+const (
+	// All is a meta class encompassing all the classes.
+	All Class = iota
+	// Success is a class for a successful response.
+	Success
+	// Denial is a class for denying existence (NXDOMAIN, or a nodata: type does not exist)
+	Denial
+	// Error is a class for errors, right now defined as not Success and not Denial
+	Error
+)
+
+func (c Class) String() string {
+	switch c {
+	case All:
+		return "all"
+	case Success:
+		return "success"
+	case Denial:
+		return "denial"
+	case Error:
+		return "error"
+	}
+	return ""
+}
+
+// ClassFromString returns the class from the string s. If not class matches
+// the All class and an error are returned
+func ClassFromString(s string) (Class, error) {
+	switch s {
+	case "all":
+		return All, nil
+	case "success":
+		return Success, nil
+	case "denial":
+		return Denial, nil
+	case "error":
+		return Error, nil
+	}
+	return All, fmt.Errorf("invalid Class: %s", s)
+}
+
+// Classify classifies the Type t, it returns its Class.
+func Classify(t Type) Class {
+	switch t {
+	case NoError, Delegation:
+		return Success
+	case NameError, NoData:
+		return Denial
+	case OtherError:
+		fallthrough
+	default:
+		return Error
+	}
+}
diff --git a/plugin/pkg/response/typify.go b/plugin/pkg/response/typify.go
new file mode 100644
index 000000000..7cfaab497
--- /dev/null
+++ b/plugin/pkg/response/typify.go
@@ -0,0 +1,146 @@
+package response
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/miekg/dns"
+)
+
+// Type is the type of the message.
+type Type int
+
+const (
+	// NoError indicates a positive reply
+	NoError Type = iota
+	// NameError is a NXDOMAIN in header, SOA in auth.
+	NameError
+	// NoData indicates name found, but not the type: NOERROR in header, SOA in auth.
+	NoData
+	// Delegation is a msg with a pointer to another nameserver: NOERROR in header, NS in auth, optionally fluff in additional (not checked).
+	Delegation
+	// Meta indicates a meta message, NOTIFY, or a transfer:  qType is IXFR or AXFR.
+	Meta
+	// Update is an dynamic update message.
+	Update
+	// OtherError indicates any other error: don't cache these.
+	OtherError
+)
+
+var toString = map[Type]string{
+	NoError:    "NOERROR",
+	NameError:  "NXDOMAIN",
+	NoData:     "NODATA",
+	Delegation: "DELEGATION",
+	Meta:       "META",
+	Update:     "UPDATE",
+	OtherError: "OTHERERROR",
+}
+
+func (t Type) String() string { return toString[t] }
+
+// TypeFromString returns the type from the string s. If not type matches
+// the OtherError type and an error are returned.
+func TypeFromString(s string) (Type, error) {
+	for t, str := range toString {
+		if s == str {
+			return t, nil
+		}
+	}
+	return NoError, fmt.Errorf("invalid Type: %s", s)
+}
+
+// Typify classifies a message, it returns the Type.
+func Typify(m *dns.Msg, t time.Time) (Type, *dns.OPT) {
+	if m == nil {
+		return OtherError, nil
+	}
+	opt := m.IsEdns0()
+	do := false
+	if opt != nil {
+		do = opt.Do()
+	}
+
+	if m.Opcode == dns.OpcodeUpdate {
+		return Update, opt
+	}
+
+	// Check transfer and update first
+	if m.Opcode == dns.OpcodeNotify {
+		return Meta, opt
+	}
+
+	if len(m.Question) > 0 {
+		if m.Question[0].Qtype == dns.TypeAXFR || m.Question[0].Qtype == dns.TypeIXFR {
+			return Meta, opt
+		}
+	}
+
+	// If our message contains any expired sigs and we care about that, we should return expired
+	if do {
+		if expired := typifyExpired(m, t); expired {
+			return OtherError, opt
+		}
+	}
+
+	if len(m.Answer) > 0 && m.Rcode == dns.RcodeSuccess {
+		return NoError, opt
+	}
+
+	soa := false
+	ns := 0
+	for _, r := range m.Ns {
+		if r.Header().Rrtype == dns.TypeSOA {
+			soa = true
+			continue
+		}
+		if r.Header().Rrtype == dns.TypeNS {
+			ns++
+		}
+	}
+
+	// Check length of different sections, and drop stuff that is just to large? TODO(miek).
+
+	if soa && m.Rcode == dns.RcodeSuccess {
+		return NoData, opt
+	}
+	if soa && m.Rcode == dns.RcodeNameError {
+		return NameError, opt
+	}
+
+	if ns > 0 && m.Rcode == dns.RcodeSuccess {
+		return Delegation, opt
+	}
+
+	if m.Rcode == dns.RcodeSuccess {
+		return NoError, opt
+	}
+
+	return OtherError, opt
+}
+
+func typifyExpired(m *dns.Msg, t time.Time) bool {
+	if expired := typifyExpiredRRSIG(m.Answer, t); expired {
+		return true
+	}
+	if expired := typifyExpiredRRSIG(m.Ns, t); expired {
+		return true
+	}
+	if expired := typifyExpiredRRSIG(m.Extra, t); expired {
+		return true
+	}
+	return false
+}
+
+func typifyExpiredRRSIG(rrs []dns.RR, t time.Time) bool {
+	for _, r := range rrs {
+		if r.Header().Rrtype != dns.TypeRRSIG {
+			continue
+		}
+		ok := r.(*dns.RRSIG).ValidityPeriod(t)
+		if !ok {
+			return true
+		}
+	}
+	return false
+}
diff --git a/plugin/pkg/response/typify_test.go b/plugin/pkg/response/typify_test.go
new file mode 100644
index 000000000..faeaf3579
--- /dev/null
+++ b/plugin/pkg/response/typify_test.go
@@ -0,0 +1,84 @@
+package response
+
+import (
+	"testing"
+	"time"
+
+	"github.com/coredns/coredns/plugin/test"
+
+	"github.com/miekg/dns"
+)
+
+func TestTypifyNilMsg(t *testing.T) {
+	var m *dns.Msg
+
+	ty, _ := Typify(m, time.Now().UTC())
+	if ty != OtherError {
+		t.Errorf("message wrongly typified, expected OtherError, got %s", ty)
+	}
+}
+
+func TestTypifyDelegation(t *testing.T) {
+	m := delegationMsg()
+	mt, _ := Typify(m, time.Now().UTC())
+	if mt != Delegation {
+		t.Errorf("message is wrongly typified, expected Delegation, got %s", mt)
+	}
+}
+
+func TestTypifyRRSIG(t *testing.T) {
+	now, _ := time.Parse(time.UnixDate, "Fri Apr 21 10:51:21 BST 2017")
+	utc := now.UTC()
+
+	m := delegationMsgRRSIGOK()
+	if mt, _ := Typify(m, utc); mt != Delegation {
+		t.Errorf("message is wrongly typified, expected Delegation, got %s", mt)
+	}
+
+	// Still a Delegation because EDNS0 OPT DO bool is not set, so we won't check the sigs.
+	m = delegationMsgRRSIGFail()
+	if mt, _ := Typify(m, utc); mt != Delegation {
+		t.Errorf("message is wrongly typified, expected Delegation, got %s", mt)
+	}
+
+	m = delegationMsgRRSIGFail()
+	m = addOpt(m)
+	if mt, _ := Typify(m, utc); mt != OtherError {
+		t.Errorf("message is wrongly typified, expected OtherError, got %s", mt)
+	}
+}
+
+func delegationMsg() *dns.Msg {
+	return &dns.Msg{
+		Ns: []dns.RR{
+			test.NS("miek.nl.	3600	IN	NS	linode.atoom.net."),
+			test.NS("miek.nl.	3600	IN	NS	ns-ext.nlnetlabs.nl."),
+			test.NS("miek.nl.	3600	IN	NS	omval.tednet.nl."),
+		},
+		Extra: []dns.RR{
+			test.A("omval.tednet.nl.	3600	IN	A	185.49.141.42"),
+			test.AAAA("omval.tednet.nl.	3600	IN	AAAA	2a04:b900:0:100::42"),
+		},
+	}
+}
+
+func delegationMsgRRSIGOK() *dns.Msg {
+	del := delegationMsg()
+	del.Ns = append(del.Ns,
+		test.RRSIG("miek.nl.		1800	IN	RRSIG	NS 8 2 1800 20170521031301 20170421031301 12051 miek.nl. PIUu3TKX/sB/N1n1E1yWxHHIcPnc2q6Wq9InShk+5ptRqChqKdZNMLDm gCq+1bQAZ7jGvn2PbwTwE65JzES7T+hEiqR5PU23DsidvZyClbZ9l0xG JtKwgzGXLtUHxp4xv/Plq+rq/7pOG61bNCxRyS7WS7i7QcCCWT1BCcv+ wZ0="),
+	)
+	return del
+}
+
+func delegationMsgRRSIGFail() *dns.Msg {
+	del := delegationMsg()
+	del.Ns = append(del.Ns,
+		test.RRSIG("miek.nl.		1800	IN	RRSIG	NS 8 2 1800 20160521031301 20160421031301 12051 miek.nl. PIUu3TKX/sB/N1n1E1yWxHHIcPnc2q6Wq9InShk+5ptRqChqKdZNMLDm gCq+1bQAZ7jGvn2PbwTwE65JzES7T+hEiqR5PU23DsidvZyClbZ9l0xG JtKwgzGXLtUHxp4xv/Plq+rq/7pOG61bNCxRyS7WS7i7QcCCWT1BCcv+ wZ0="),
+	)
+	return del
+}
+
+func addOpt(m *dns.Msg) *dns.Msg {
+	m.Extra = append(m.Extra, test.OPT(4096, true))
+	return m
+}