Add field keywords to rewrite middleware (#497)

* Require Field for rewrite rules

* review feedback changes

* fix ut

* fix typo, add warning message

middleware/rewrite/README.md

@@ -7,24 +7,26 @@ accommodate most dynamic back-end applications.
 ## Syntax
 
 ~~~
-rewrite FROM TO
+rewrite FIELD FROM TO
 ~~~
 
+* **FIELD** is (`type`, `class`, `name`, ...)
 * **FROM** is the exact name of type to match
 * **TO** is the destination name or type to rewrite to
 
-If from *and* to look like a DNS type (`A`, `MX`, etc.), the type of the message will be rewriten;
-e.g., to rewrite ANY queries to HINFO, use `rewrite ANY HINFO`.
+When the FIELD is `type` and FROM is (`A`, `MX`, etc.), the type of the message will be rewritten;
+e.g., to rewrite ANY queries to HINFO, use `rewrite type ANY HINFO`.
 
-If from *and* to look like a DNS class (`IN`, `CH`, or `HS`) the class of the message will be
-rewritten; e.g., to rewrite CH queries to IN use `rewrite CH IN`.
+When the FIELD is `class` and FROM is (`IN`, `CH`, or `HS`) the class of the message will be
+rewritten; e.g., to rewrite CH queries to IN use `rewrite class CH IN`.
 
-If it does not look like a type a name is assumed and the qname in the message is rewritten; this
-needs to be a full match of the name, e.g., `rewrite miek.nl example.org`.
+When the FIELD is `name` the query name in the message is rewritten; this
+needs to be a full match of the name, e.g., `rewrite name miek.nl example.org`.
 
 If you specify multiple rules and an incoming query matches on multiple (simple) rules, only
 the first rewrite is applied.
 
+
 > Everything below this line has not been implemented, yet.
 
 ~~~

middleware/rewrite/class.go

@@ -0,0 +1,31 @@
+// Package rewrite is middleware for rewriting requests internally to something different.
+package rewrite
+
+import (
+	"strings"
+
+	"github.com/miekg/dns"
+)
+
+// ClassRule is a class rewrite rule.
+type ClassRule struct {
+	fromClass, toClass uint16
+}
+
+// Initializer
+func (rule ClassRule) New(args ...string) Rule {
+	from, to := args[0], strings.Join(args[1:], " ")
+	return &ClassRule{dns.StringToClass[from], dns.StringToClass[to]}
+
+}
+
+// Rewrite rewrites the the current request.
+func (rule ClassRule) Rewrite(r *dns.Msg) Result {
+	if rule.fromClass > 0 && rule.toClass > 0 {
+		if r.Question[0].Qclass == rule.fromClass {
+			r.Question[0].Qclass = rule.toClass
+			return RewriteDone
+		}
+	}
+	return RewriteIgnored
+}

middleware/rewrite/field.go

@@ -0,0 +1,13 @@
+// Package rewrite is middleware for rewriting requests internally to something different.
+package rewrite
+
+/*
+Additional FIELD keywords may be implemented to support more rewrite use-cases.
+New Rule types must be added to the Fields map.
+The type must implement `New` and `Rewrite` functions.
+*/
+var Fields = map[string]Rule{
+	"name":  NameRule{},
+	"type":  TypeRule{},
+	"class": ClassRule{},
+}

middleware/rewrite/name.go

@@ -0,0 +1,29 @@
+// Package rewrite is middleware for rewriting requests internally to something different.
+package rewrite
+
+import (
+	"strings"
+
+	"github.com/miekg/coredns/middleware"
+	"github.com/miekg/dns"
+)
+
+// NameRule is a name rewrite rule.
+type NameRule struct {
+	From, To string
+}
+
+// Initializer
+func (rule NameRule) New(args ...string) Rule {
+	from, to := args[0], strings.Join(args[1:], " ")
+	return &NameRule{middleware.Name(from).Normalize(), middleware.Name(to).Normalize()}
+}
+
+// Rewrite rewrites the the current request.
+func (rule NameRule) Rewrite(r *dns.Msg) Result {
+	if rule.From == r.Question[0].Name {
+		r.Question[0].Name = rule.To
+		return RewriteDone
+	}
+	return RewriteIgnored
+}

middleware/rewrite/rewrite.go

@@ -2,10 +2,7 @@
 package rewrite
 
 import (
-	"strings"
-
 	"github.com/miekg/coredns/middleware"
-
 	"github.com/miekg/dns"
 	"golang.org/x/net/context"
 )
@@ -59,64 +56,6 @@ func (rw Rewrite) Name() string { return "rewrite" }
 type Rule interface {
 	// Rewrite rewrites the internal location of the current request.
 	Rewrite(*dns.Msg) Result
-}
-
-// SimpleRule is a simple rewrite rule. If the From and To look like a type
-// the type of the request is rewritten, otherwise the name is.
-// Note: TSIG signed requests will be invalid.
-type SimpleRule struct {
-	From, To           string
-	fromType, toType   uint16
-	fromClass, toClass uint16
-}
-
-// NewSimpleRule creates a new Simple Rule
-func NewSimpleRule(from, to string) SimpleRule {
-	tpf := dns.StringToType[from]
-	tpt := dns.StringToType[to]
-
-	// ANY is both a type and class, ANY class rewritting is way more less frequent
-	// so we default to ANY as a type.
-	clf := dns.StringToClass[from]
-	clt := dns.StringToClass[to]
-	if from == "ANY" {
-		clf = 0
-		clt = 0
-	}
-
-	// It's only a type/class if uppercase is used.
-	if from != strings.ToUpper(from) {
-		tpf = 0
-		clf = 0
-		from = middleware.Name(from).Normalize()
-	}
-	if to != strings.ToUpper(to) {
-		tpt = 0
-		clt = 0
-		to = middleware.Name(to).Normalize()
-	}
-	return SimpleRule{From: from, To: to, fromType: tpf, toType: tpt, fromClass: clf, toClass: clt}
-}
-
-// Rewrite rewrites the the current request.
-func (s SimpleRule) Rewrite(r *dns.Msg) Result {
-	if s.fromType > 0 && s.toType > 0 {
-		if r.Question[0].Qtype == s.fromType {
-			r.Question[0].Qtype = s.toType
-			return RewriteDone
-		}
-	}
-
-	if s.fromClass > 0 && s.toClass > 0 {
-		if r.Question[0].Qclass == s.fromClass {
-			r.Question[0].Qclass = s.toClass
-			return RewriteDone
-		}
-	}
-
-	if s.From == r.Question[0].Name {
-		r.Question[0].Name = s.To
-		return RewriteDone
-	}
-	return RewriteIgnored
+	// New returns a new rule.
+	New(...string) Rule
 }

middleware/rewrite/rewrite_test.go

@@ -20,9 +20,9 @@ func TestRewrite(t *testing.T) {
 	rw := Rewrite{
 		Next: middleware.HandlerFunc(msgPrinter),
 		Rules: []Rule{
-			NewSimpleRule("from.nl.", "to.nl."),
-			NewSimpleRule("CH", "IN"),
-			NewSimpleRule("ANY", "HINFO"),
+			Fields["name"].New("from.nl.", "to.nl."),
+			Fields["class"].New("CH", "IN"),
+			Fields["type"].New("ANY", "HINFO"),
 		},
 		noRevert: true,
 	}

middleware/rewrite/setup.go

@@ -1,7 +1,7 @@
 package rewrite
 
 import (
-	"strings"
+	"log"
 
 	"github.com/miekg/coredns/core/dnsserver"
 	"github.com/miekg/coredns/middleware"
@@ -108,8 +108,12 @@ func rewriteParse(c *caddy.Controller) ([]Rule, error) {
 
 		// the only unhandled case is 2 and above
 		default:
-			rule = NewSimpleRule(args[0], strings.Join(args[1:], " "))
-			simpleRules = append(simpleRules, rule)
+			if _, ok := Fields[args[0]]; ok {
+				rule = Fields[args[0]].New(args[1:]...)
+				simpleRules = append(simpleRules, rule)
+			} else {
+				log.Printf("[WARN] %s is not a valid field, ignore %s", args[0], args)
+			}
 		}
 	}
 

middleware/rewrite/type.go

@@ -0,0 +1,30 @@
+// Package rewrite is middleware for rewriting requests internally to something different.
+package rewrite
+
+import (
+	"strings"
+
+	"github.com/miekg/dns"
+)
+
+// TypeRule is a type rewrite rule.
+type TypeRule struct {
+	fromType, toType uint16
+}
+
+// Initializer
+func (rule TypeRule) New(args ...string) Rule {
+	from, to := args[0], strings.Join(args[1:], " ")
+	return &TypeRule{dns.StringToType[from], dns.StringToType[to]}
+}
+
+// Rewrite rewrites the the current request.
+func (rule TypeRule) Rewrite(r *dns.Msg) Result {
+	if rule.fromType > 0 && rule.toType > 0 {
+		if r.Question[0].Qtype == rule.fromType {
+			r.Question[0].Qtype = rule.toType
+			return RewriteDone
+		}
+	}
+	return RewriteIgnored
+}