Rewrite SRV targets and additional names in response (#4287)

* Rewrite plugin - rewrite SRV targets and names in response answer and additional records
Signed-off-by: Nic Colledge <nic@njcolledge.net>

* Added README content to describe new behaviour
Signed-off-by: Nic Colledge <nic@njcolledge.net>

* Added more record types to rewrite handling based on PR/Issue feedback
Signed-off-by: Nic Colledge <nic@njcolledge.net>

* Updated README.md for plugin
Signed-off-by: Nic Colledge <nic@njcolledge.net>

* Updated unit tests.
Small refactor of getTarget... function.
Signed-off-by: Nic Colledge <nic@njcolledge.net>

* Refactor to add response value rewrite as answer value option
Signed-off-by: Nic Colledge <nic@njcolledge.net>

* Removed TODO comment, added test for NAPTR record.
Signed-off-by: Nic Colledge <nic@njcolledge.net>

plugin/rewrite/README.md

@@ -151,26 +151,37 @@ ftp-us-west-1.coredns.rocks. 0    IN A    10.20.20.20
 ftp-us-west-1.coredns.rocks. 0    IN A    10.30.30.30
 ```
 
+It is also possible to rewrite other values returned in the DNS response records 
+(e.g. the server names returned in `SRV` and `MX` records). This can be enabled by adding 
+the `answer value` to a name regex rule as specified below. `answer value` takes a 
+regular expression and a rewrite name as parameters and works in the same way as the 
+`answer name` rule.
+
+Note that names in the `AUTHORITY SECTION` and `ADDITIONAL SECTION` will also be
+rewritten following the specified rules. The names returned by the following
+record types: `CNAME`, `DNAME`, `SOA`, `SRV`, `MX`, `NAPTR`, `NS` will be rewritten 
+if the `answer value` rule is specified.
+
 The syntax for the rewrite of DNS request and response is as follows:
 
 ```
 rewrite [continue|stop] {
     name regex STRING STRING
     answer name STRING STRING
+    [answer value STRING STRING]
 }
 ```
 
 Note that the above syntax is strict.  For response rewrites, only `name`
 rules are allowed to match the question section, and only by match type
 `regex`. The answer rewrite must be after the name, as in the
-syntax example. There must only be two lines (a `name` followed by an
-`answer`) in the brackets; additional rules are not supported.
+syntax example.
 
 An alternate syntax for rewriting a DNS request and response is as
 follows:
 
 ```
-rewrite [continue|stop] name regex STRING STRING answer name STRING STRING
+rewrite [continue|stop] name regex STRING STRING answer name STRING STRING [answer value STRING STRING]
 ```
 
 When using `exact` name rewrite rules, the answer gets rewritten automatically,

plugin/rewrite/class.go

@@ -43,5 +43,5 @@ func (rule *classRule) Rewrite(ctx context.Context, state request.Request) Resul
 // Mode returns the processing mode.
 func (rule *classRule) Mode() string { return rule.NextAction }
 
-// GetResponseRule return a rule to rewrite the response with. Currently not implemented.
-func (rule *classRule) GetResponseRule() ResponseRule { return ResponseRule{} }
+// GetResponseRules return rules to rewrite the response with. Currently not implemented.
+func (rule *classRule) GetResponseRules() []ResponseRule { return []ResponseRule{} }

plugin/rewrite/edns0.go

@@ -73,8 +73,8 @@ func (rule *edns0NsidRule) Rewrite(ctx context.Context, state request.Request) R
 // Mode returns the processing mode.
 func (rule *edns0NsidRule) Mode() string { return rule.mode }
 
-// GetResponseRule returns a rule to rewrite the response with. Currently not implemented.
-func (rule *edns0NsidRule) GetResponseRule() ResponseRule { return ResponseRule{} }
+// GetResponseRules returns rules to rewrite the response with. Currently not implemented.
+func (rule *edns0NsidRule) GetResponseRules() []ResponseRule { return []ResponseRule{} }
 
 // Rewrite will alter the request EDNS0 local options.
 func (rule *edns0LocalRule) Rewrite(ctx context.Context, state request.Request) Result {
@@ -103,8 +103,8 @@ func (rule *edns0LocalRule) Rewrite(ctx context.Context, state request.Request)
 // Mode returns the processing mode.
 func (rule *edns0LocalRule) Mode() string { return rule.mode }
 
-// GetResponseRule returns a rule to rewrite the response with. Currently not implemented.
-func (rule *edns0LocalRule) GetResponseRule() ResponseRule { return ResponseRule{} }
+// GetResponseRules returns a rule to rewrite the response with. Currently not implemented.
+func (rule *edns0LocalRule) GetResponseRules() []ResponseRule { return []ResponseRule{} }
 
 // newEdns0Rule creates an EDNS0 rule of the appropriate type based on the args
 func newEdns0Rule(mode string, args ...string) (Rule, error) {
@@ -253,8 +253,8 @@ func (rule *edns0VariableRule) Rewrite(ctx context.Context, state request.Reques
 // Mode returns the processing mode.
 func (rule *edns0VariableRule) Mode() string { return rule.mode }
 
-// GetResponseRule returns a rule to rewrite the response with. Currently not implemented.
-func (rule *edns0VariableRule) GetResponseRule() ResponseRule { return ResponseRule{} }
+// GetResponseRules returns rules to rewrite the response with. Currently not implemented.
+func (rule *edns0VariableRule) GetResponseRules() []ResponseRule { return []ResponseRule{} }
 
 func isValidVariable(variable string) bool {
 	switch variable {
@@ -362,8 +362,8 @@ func (rule *edns0SubnetRule) Rewrite(ctx context.Context, state request.Request)
 // Mode returns the processing mode
 func (rule *edns0SubnetRule) Mode() string { return rule.mode }
 
-// GetResponseRule return a rule to rewrite the response with. Currently not implemented.
-func (rule *edns0SubnetRule) GetResponseRule() ResponseRule { return ResponseRule{} }
+// GetResponseRules return rules to rewrite the response with. Currently not implemented.
+func (rule *edns0SubnetRule) GetResponseRules() []ResponseRule { return []ResponseRule{} }
 
 // These are all defined actions.
 const (

plugin/rewrite/name.go

@@ -37,10 +37,10 @@ type substringNameRule struct {
 }
 
 type regexNameRule struct {
-	NextAction  string
-	Pattern     *regexp.Regexp
-	Replacement string
-	ResponseRule
+	NextAction    string
+	Pattern       *regexp.Regexp
+	Replacement   string
+	ResponseRules []ResponseRule
 }
 
 const (
@@ -113,7 +113,6 @@ func (rule *regexNameRule) Rewrite(ctx context.Context, state request.Request) R
 // newNameRule creates a name matching rule based on exact, partial, or regex match
 func newNameRule(nextAction string, args ...string) (Rule, error) {
 	var matchType, rewriteQuestionFrom, rewriteQuestionTo string
-	var rewriteAnswerField, rewriteAnswerFrom, rewriteAnswerTo string
 	if len(args) < 2 {
 		return nil, fmt.Errorf("too few arguments for a name rule")
 	}
@@ -140,8 +139,9 @@ func newNameRule(nextAction string, args ...string) (Rule, error) {
 		}
 	}
 
-	if len(args) > 3 && len(args) != 7 {
-		return nil, fmt.Errorf("response rewrites must consist only of a name rule with 3 arguments and an answer rule with 3 arguments")
+	//if len(args) > 3 && len(args) != 7 {
+	if len(args) > 3 && (len(args) - 3) % 4 != 0 {
+		return nil, fmt.Errorf("response rewrites must consist only of a name rule with 3 arguments and one or more answer rules with 3 arguments each")
 	}
 
 	if len(args) < 7 {
@@ -190,47 +190,39 @@ func newNameRule(nextAction string, args ...string) (Rule, error) {
 				nextAction,
 				rewriteQuestionFromPattern,
 				rewriteQuestionTo,
-				ResponseRule{
+				[]ResponseRule{{
 					Type: "name",
-				},
+				}},
 			}, nil
 		default:
 			return nil, fmt.Errorf("name rule supports only exact, prefix, suffix, substring, and regex name matching, received: %s", matchType)
 		}
 	}
-	if len(args) == 7 {
+	//if len(args) == 7 {
+	if (len(args) - 3) % 4 == 0 {
 		if matchType == RegexMatch {
-			if args[3] != "answer" {
-				return nil, fmt.Errorf("exceeded the number of arguments for a regex name rule")
-			}
 			rewriteQuestionFromPattern, err := isValidRegexPattern(rewriteQuestionFrom, rewriteQuestionTo)
 			if err != nil {
 				return nil, err
 			}
-			rewriteAnswerField = strings.ToLower(args[4])
-			switch rewriteAnswerField {
-			case "name":
-			default:
-				return nil, fmt.Errorf("exceeded the number of arguments for a regex name rule")
-			}
-			rewriteAnswerFrom = args[5]
-			rewriteAnswerTo = args[6]
-			rewriteAnswerFromPattern, err := isValidRegexPattern(rewriteAnswerFrom, rewriteAnswerTo)
-			if err != nil {
-				return nil, err
-			}
 			rewriteQuestionTo = plugin.Name(args[2]).Normalize()
-			rewriteAnswerTo = plugin.Name(args[6]).Normalize()
+
+			responseRuleCount := (len(args) - 3) / 4
+			responseRules := make([]ResponseRule, responseRuleCount)
+			for i := 0; i < responseRuleCount; i ++ {
+				startIdx := 3 + (i * 4)
+				responseRule, err := newResponseRule(args[startIdx:startIdx + 4])
+				if err != nil {
+					return nil, err
+				}
+				responseRules[i] = *responseRule
+			}
+
 			return &regexNameRule{
 				nextAction,
 				rewriteQuestionFromPattern,
 				rewriteQuestionTo,
-				ResponseRule{
-					Active:      true,
-					Type:        "name",
-					Pattern:     rewriteAnswerFromPattern,
-					Replacement: rewriteAnswerTo,
-				},
+				responseRules,
 			}, nil
 		}
 		return nil, fmt.Errorf("the rewrite of response is supported only for name regex rule")
@@ -238,6 +230,34 @@ func newNameRule(nextAction string, args ...string) (Rule, error) {
 	return nil, fmt.Errorf("the rewrite rule is invalid: %s", args)
 }
 
+// newResponseRule creates a new "answer name" or "answer value" response rule.
+func newResponseRule(args []string) (responseRule *ResponseRule, err error){
+	if args[0] != "answer" {
+		return nil, fmt.Errorf("exceeded the number of arguments for a regex name rule")
+	}
+	rewriteAnswerField := strings.ToLower(args[1])
+	switch rewriteAnswerField {
+	case "name":
+	case "value":
+	default:
+		return nil, fmt.Errorf("exceeded the number of arguments for a regex name rule")
+	}
+	rewriteAnswerFrom := args[2]
+	rewriteAnswerTo := args[3]
+	rewriteAnswerFromPattern, err := isValidRegexPattern(rewriteAnswerFrom, rewriteAnswerTo)
+	if err != nil {
+		return nil, err
+	}
+	rewriteAnswerTo = plugin.Name(args[3]).Normalize()
+
+	return &ResponseRule{
+		Active:      true,
+		Type:        rewriteAnswerField,
+		Pattern:     rewriteAnswerFromPattern,
+		Replacement: rewriteAnswerTo,
+	}, nil
+}
+
 // Mode returns the processing nextAction
 func (rule *exactNameRule) Mode() string     { return rule.NextAction }
 func (rule *prefixNameRule) Mode() string    { return rule.NextAction }
@@ -245,20 +265,20 @@ func (rule *suffixNameRule) Mode() string    { return rule.NextAction }
 func (rule *substringNameRule) Mode() string { return rule.NextAction }
 func (rule *regexNameRule) Mode() string     { return rule.NextAction }
 
-// GetResponseRule returns a rule to rewrite the response with. Currently not implemented.
-func (rule *exactNameRule) GetResponseRule() ResponseRule { return rule.ResponseRule }
+// GetResponseRules returns rules to rewrite the response with. Currently not implemented.
+func (rule *exactNameRule) GetResponseRules() []ResponseRule { return []ResponseRule{rule.ResponseRule} }
 
-// GetResponseRule returns a rule to rewrite the response with. Currently not implemented.
-func (rule *prefixNameRule) GetResponseRule() ResponseRule { return ResponseRule{} }
+// GetResponseRules returns rules to rewrite the response with. Currently not implemented.
+func (rule *prefixNameRule) GetResponseRules() []ResponseRule { return []ResponseRule{} }
 
-// GetResponseRule returns a rule to rewrite the response with. Currently not implemented.
-func (rule *suffixNameRule) GetResponseRule() ResponseRule { return ResponseRule{} }
+// GetResponseRules returns rules to rewrite the response with. Currently not implemented.
+func (rule *suffixNameRule) GetResponseRules() []ResponseRule { return []ResponseRule{} }
 
-// GetResponseRule returns a rule to rewrite the response with. Currently not implemented.
-func (rule *substringNameRule) GetResponseRule() ResponseRule { return ResponseRule{} }
+// GetResponseRules returns rules to rewrite the response with. Currently not implemented.
+func (rule *substringNameRule) GetResponseRules() []ResponseRule { return []ResponseRule{} }
 
-// GetResponseRule returns a rule to rewrite the response with.
-func (rule *regexNameRule) GetResponseRule() ResponseRule { return rule.ResponseRule }
+// GetResponseRules returns rules to rewrite the response with.
+func (rule *regexNameRule) GetResponseRules() []ResponseRule { return rule.ResponseRules }
 
 // hasClosingDot returns true if s has a closing dot at the end.
 func hasClosingDot(s string) bool {

plugin/rewrite/reverter.go

@@ -42,46 +42,116 @@ func (r *ResponseReverter) WriteMsg(res1 *dns.Msg) error {
 
 	res.Question[0] = r.originalQuestion
 	if r.ResponseRewrite {
+		for _, rr := range res.Ns {
+			rewriteResourceRecord(res, rr, r)
+		}
+
 		for _, rr := range res.Answer {
-			var (
-				isNameRewritten bool
-				isTTLRewritten  bool
-				name            = rr.Header().Name
-				ttl             = rr.Header().Ttl
-			)
-			for _, rule := range r.ResponseRules {
-				if rule.Type == "" {
-					rule.Type = "name"
-				}
-				switch rule.Type {
-				case "name":
-					regexGroups := rule.Pattern.FindStringSubmatch(name)
-					if len(regexGroups) == 0 {
-						continue
-					}
-					s := rule.Replacement
-					for groupIndex, groupValue := range regexGroups {
-						groupIndexStr := "{" + strconv.Itoa(groupIndex) + "}"
-						s = strings.Replace(s, groupIndexStr, groupValue, -1)
-					}
-					name = s
-					isNameRewritten = true
-				case "ttl":
-					ttl = rule.TTL
-					isTTLRewritten = true
-				}
-			}
-			if isNameRewritten {
-				rr.Header().Name = name
-			}
-			if isTTLRewritten {
-				rr.Header().Ttl = ttl
-			}
+			rewriteResourceRecord(res, rr, r)
+		}
+
+		for _, rr := range res.Extra {
+			rewriteResourceRecord(res, rr, r)
 		}
+
 	}
 	return r.ResponseWriter.WriteMsg(res)
 }
 
+func rewriteResourceRecord(res *dns.Msg, rr dns.RR, r *ResponseReverter) {
+	var (
+		isNameRewritten   bool
+		isTTLRewritten    bool
+		isValueRewritten  bool
+		name              = rr.Header().Name
+		ttl               = rr.Header().Ttl
+		value             string
+	)
+
+	for _, rule := range r.ResponseRules {
+		if rule.Type == "" {
+			rule.Type = "name"
+		}
+		switch rule.Type {
+		case "name":
+			rewriteString(rule, &name, &isNameRewritten)
+		case "value":
+			value = getRecordValueForRewrite(rr)
+			if value != "" {
+				rewriteString(rule, &value, &isValueRewritten)
+			}
+		case "ttl":
+			ttl = rule.TTL
+			isTTLRewritten = true
+		}
+	}
+
+	if isNameRewritten {
+		rr.Header().Name = name
+	}
+	if isTTLRewritten {
+		rr.Header().Ttl = ttl
+	}
+	if isValueRewritten {
+		setRewrittenRecordValue(rr, value)
+	}
+}
+
+func getRecordValueForRewrite(rr dns.RR) (name string) {
+	switch rr.Header().Rrtype {
+	case dns.TypeSRV:
+		return rr.(*dns.SRV).Target
+	case dns.TypeMX:
+		return rr.(*dns.MX).Mx
+	case dns.TypeCNAME:
+		return rr.(*dns.CNAME).Target
+	case dns.TypeNS:
+		return rr.(*dns.NS).Ns
+	case dns.TypeDNAME:
+		return rr.(*dns.DNAME).Target
+	case dns.TypeNAPTR:
+		return rr.(*dns.NAPTR).Replacement
+	case dns.TypeSOA:
+		return rr.(*dns.SOA).Ns
+	default:
+		return ""
+	}
+}
+
+func setRewrittenRecordValue(rr dns.RR, value string) {
+	switch rr.Header().Rrtype {
+	case dns.TypeSRV:
+		rr.(*dns.SRV).Target = value
+	case dns.TypeMX:
+		rr.(*dns.MX).Mx = value
+	case dns.TypeCNAME:
+		rr.(*dns.CNAME).Target = value
+	case dns.TypeNS:
+		rr.(*dns.NS).Ns = value
+	case dns.TypeDNAME:
+		rr.(*dns.DNAME).Target = value
+	case dns.TypeNAPTR:
+		rr.(*dns.NAPTR).Replacement = value
+	case dns.TypeSOA:
+		rr.(*dns.SOA).Ns = value
+	}
+}
+
+func rewriteString(rule ResponseRule, str *string, isStringRewritten *bool) {
+	regexGroups := rule.Pattern.FindStringSubmatch(*str)
+	if len(regexGroups) == 0 {
+		return
+	}
+	s := rule.Replacement
+	for groupIndex, groupValue := range regexGroups {
+		groupIndexStr := "{" + strconv.Itoa(groupIndex) + "}"
+		s = strings.Replace(s, groupIndexStr, groupValue, -1)
+	}
+
+	*isStringRewritten = true
+	*str = s
+}
+
 // Write is a wrapper that records the size of the message that gets written.
 func (r *ResponseReverter) Write(buf []byte) (int, error) {
 	n, err := r.ResponseWriter.Write(buf)

plugin/rewrite/reverter_test.go

@@ -68,3 +68,90 @@ func doReverterTests(rules []Rule, t *testing.T) {
 		}
 	}
 }
+
+var valueTests = []struct {
+	from             string
+	fromType         uint16
+	answer           []dns.RR
+	extra            []dns.RR
+	to               string
+	toType           uint16
+	noRevert         bool
+	expectValue     string
+	expectAnswerType uint16
+	expectAddlName   string
+}{
+	{"my.domain.uk", dns.TypeSRV, []dns.RR{test.SRV("my.cluster.local.  5  IN  SRV 0 100 100 srv1.my.cluster.local.")}, []dns.RR{test.A("srv1.my.cluster.local.  5   IN  A  10.0.0.1")}, "my.domain.uk", dns.TypeSRV, false, "srv1.my.domain.uk.", dns.TypeSRV, "srv1.my.domain.uk."},
+	{"my.domain.uk", dns.TypeSRV, []dns.RR{test.SRV("my.cluster.local.  5  IN  SRV 0 100 100 srv1.my.cluster.local.")}, []dns.RR{test.A("srv1.my.cluster.local.  5   IN  A  10.0.0.1")}, "my.cluster.local.", dns.TypeSRV, true, "srv1.my.cluster.local.", dns.TypeSRV, "srv1.my.cluster.local."},
+	{"my.domain.uk", dns.TypeANY, []dns.RR{test.CNAME("my.cluster.local.  3600 IN CNAME cname.cluster.local.")}, []dns.RR{test.A("cname.cluster.local.  5   IN  A  10.0.0.1")}, "my.domain.uk", dns.TypeANY, false, "cname.domain.uk.", dns.TypeCNAME, "cname.domain.uk."},
+	{"my.domain.uk", dns.TypeANY, []dns.RR{test.CNAME("my.cluster.local.  3600 IN CNAME cname.cluster.local.")}, []dns.RR{test.A("cname.cluster.local.  5   IN  A  10.0.0.1")}, "my.cluster.local.", dns.TypeANY, true, "cname.cluster.local.", dns.TypeCNAME, "cname.cluster.local."},
+	{"my.domain.uk", dns.TypeANY, []dns.RR{test.DNAME("my.cluster.local.  3600 IN DNAME dname.cluster.local.")}, []dns.RR{test.A("dname.cluster.local.  5   IN  A  10.0.0.1")}, "my.domain.uk", dns.TypeANY, false, "dname.domain.uk.", dns.TypeDNAME, "dname.domain.uk."},
+	{"my.domain.uk", dns.TypeANY, []dns.RR{test.DNAME("my.cluster.local.  3600 IN DNAME dname.cluster.local.")}, []dns.RR{test.A("dname.cluster.local.  5   IN  A  10.0.0.1")}, "my.cluster.local.", dns.TypeANY, true, "dname.cluster.local.", dns.TypeDNAME, "dname.cluster.local."},
+	{"my.domain.uk", dns.TypeMX, []dns.RR{test.MX("my.cluster.local.	3600	IN	MX	1 mx1.cluster.local.")}, []dns.RR{test.A("mx1.cluster.local.  5   IN  A  10.0.0.1")}, "my.domain.uk", dns.TypeMX, false, "mx1.domain.uk.", dns.TypeMX, "mx1.domain.uk."},
+	{"my.domain.uk", dns.TypeMX, []dns.RR{test.MX("my.cluster.local.	3600	IN	MX	1 mx1.cluster.local.")}, []dns.RR{test.A("mx1.cluster.local.  5   IN  A  10.0.0.1")}, "my.cluster.local.", dns.TypeMX, true, "mx1.cluster.local.", dns.TypeMX, "mx1.cluster.local."},
+	{"my.domain.uk", dns.TypeANY, []dns.RR{test.NS("my.cluster.local.	3600	IN	NS	ns1.cluster.local.")}, []dns.RR{test.A("ns1.cluster.local.  5   IN  A  10.0.0.1")}, "my.domain.uk", dns.TypeANY, false, "ns1.domain.uk.", dns.TypeNS, "ns1.domain.uk."},
+	{"my.domain.uk", dns.TypeANY, []dns.RR{test.NS("my.cluster.local.	3600	IN	NS	ns1.cluster.local.")}, []dns.RR{test.A("ns1.cluster.local.  5   IN  A  10.0.0.1")}, "my.cluster.local.", dns.TypeANY, true, "ns1.cluster.local.", dns.TypeNS, "ns1.cluster.local."},
+	{"my.domain.uk", dns.TypeSOA, []dns.RR{test.SOA("my.cluster.local.		1800	IN	SOA	ns1.cluster.local. admin.cluster.local. 1502165581 14400 3600 604800 14400")}, []dns.RR{test.A("ns1.cluster.local.  5   IN  A  10.0.0.1")}, "my.domain.uk", dns.TypeSOA, false, "ns1.domain.uk.", dns.TypeSOA, "ns1.domain.uk."},
+	{"my.domain.uk", dns.TypeSOA, []dns.RR{test.SOA("my.cluster.local.		1800	IN	SOA	ns1.cluster.local. admin.cluster.local. 1502165581 14400 3600 604800 14400")}, []dns.RR{test.A("ns1.cluster.local.  5   IN  A  10.0.0.1")}, "my.cluster.local.", dns.TypeSOA, true, "ns1.cluster.local.", dns.TypeSOA, "ns1.cluster.local."},
+	{"my.domain.uk", dns.TypeNAPTR, []dns.RR{test.NAPTR("my.cluster.local.  100  IN NAPTR 100 10 \"S\" \"SIP+D2U\" \"!^.*$!sip:customer-service@example.com!\" _sip._udp.cluster.local.")}, []dns.RR{test.A("ns1.cluster.local.  5   IN  A  10.0.0.1")}, "my.domain.uk", dns.TypeNAPTR, false, "_sip._udp.domain.uk.", dns.TypeNAPTR, "ns1.domain.uk."},
+	{"my.domain.uk", dns.TypeNAPTR, []dns.RR{test.NAPTR("my.cluster.local.  100  IN NAPTR 100 10 \"S\" \"SIP+D2U\" \"!^.*$!sip:customer-service@example.com!\" _sip._udp.cluster.local.")}, []dns.RR{test.A("ns1.cluster.local.  5   IN  A  10.0.0.1")}, "my.cluster.local.", dns.TypeNAPTR, true, "_sip._udp.cluster.local.", dns.TypeNAPTR, "ns1.cluster.local."},
+}
+
+func TestValueResponseReverter(t *testing.T) {
+
+	rules := []Rule{}
+	r, _ := newNameRule("stop", "regex", `(.*)\.domain\.uk`, "{1}.cluster.local", "answer", "name", `(.*)\.cluster\.local`, "{1}.domain.uk", "answer", "value", `(.*)\.cluster\.local`, "{1}.domain.uk")
+	rules = append(rules, r)
+
+	doValueReverterTests(rules, t)
+
+	rules = []Rule{}
+	r, _ = newNameRule("continue", "regex", `(.*)\.domain\.uk`, "{1}.cluster.local", "answer", "name", `(.*)\.cluster\.local`, "{1}.domain.uk", "answer", "value", `(.*)\.cluster\.local`, "{1}.domain.uk")
+	rules = append(rules, r)
+
+	doValueReverterTests(rules, t)
+}
+
+func doValueReverterTests(rules []Rule, t *testing.T) {
+	ctx := context.TODO()
+	for i, tc := range valueTests {
+		m := new(dns.Msg)
+		m.SetQuestion(tc.from, tc.fromType)
+		m.Question[0].Qclass = dns.ClassINET
+		m.Answer = tc.answer
+		m.Extra = tc.extra
+		rw := Rewrite{
+			Next:     plugin.HandlerFunc(msgPrinter),
+			Rules:    rules,
+			noRevert: tc.noRevert,
+		}
+		rec := dnstest.NewRecorder(&test.ResponseWriter{})
+		rw.ServeDNS(ctx, rec, m)
+		resp := rec.Msg
+		if resp.Question[0].Name != tc.to {
+			t.Errorf("Test %d: Expected Name to be %q but was %q", i, tc.to, resp.Question[0].Name)
+		}
+		if resp.Question[0].Qtype != tc.toType {
+			t.Errorf("Test %d: Expected Type to be '%d' but was '%d'", i, tc.toType, resp.Question[0].Qtype)
+		}
+
+		if len(resp.Answer) <= 0 || resp.Answer[0].Header().Rrtype != tc.expectAnswerType {
+			t.Error("Unexpected Answer Record Type / No Answers")
+			return
+		}
+
+		value := getRecordValueForRewrite(resp.Answer[0])
+		if value != tc.expectValue {
+			t.Errorf("Test %d: Expected Target to be '%s' but was '%s'", i, tc.expectValue, value)
+		}
+
+		if len(resp.Extra) <= 0 || resp.Extra[0].Header().Rrtype != dns.TypeA {
+			t.Error("Unexpected Additional Record Type / No Additional Records")
+			return
+		}
+
+		if resp.Extra[0].Header().Name != tc.expectAddlName {
+			t.Errorf("Test %d: Expected Extra Name to be %q but was %q", i, tc.expectAddlName, resp.Extra[0].Header().Name)
+		}
+	}
+}

plugin/rewrite/rewrite.go

@@ -49,10 +49,11 @@ func (rw Rewrite) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg
 				state.Req.Question[0] = wr.originalQuestion
 				return dns.RcodeServerFailure, err
 			}
-			respRule := rule.GetResponseRule()
-			if respRule.Active {
-				wr.ResponseRewrite = true
-				wr.ResponseRules = append(wr.ResponseRules, respRule)
+			for _, respRule := range rule.GetResponseRules() {
+				if respRule.Active {
+					wr.ResponseRewrite = true
+					wr.ResponseRules = append(wr.ResponseRules, respRule)
+				}
 			}
 			if rule.Mode() == Stop {
 				if rw.noRevert {
@@ -78,8 +79,8 @@ type Rule interface {
 	Rewrite(ctx context.Context, state request.Request) Result
 	// Mode returns the processing mode stop or continue.
 	Mode() string
-	// GetResponseRule returns the rule to rewrite response with, if any.
-	GetResponseRule() ResponseRule
+	// GetResponseRules returns rules to rewrite response with, if any.
+	GetResponseRules() []ResponseRule
 }
 
 func newRule(args ...string) (Rule, error) {

plugin/rewrite/ttl.go

@@ -15,31 +15,31 @@ import (
 type exactTTLRule struct {
 	NextAction string
 	From       string
-	ResponseRule
+	ResponseRules []ResponseRule
 }
 
 type prefixTTLRule struct {
 	NextAction string
 	Prefix     string
-	ResponseRule
+	ResponseRules []ResponseRule
 }
 
 type suffixTTLRule struct {
 	NextAction string
 	Suffix     string
-	ResponseRule
+	ResponseRules []ResponseRule
 }
 
 type substringTTLRule struct {
 	NextAction string
 	Substring  string
-	ResponseRule
+	ResponseRules []ResponseRule
 }
 
 type regexTTLRule struct {
 	NextAction string
 	Pattern    *regexp.Regexp
-	ResponseRule
+	ResponseRules []ResponseRule
 }
 
 // Rewrite rewrites the current request based upon exact match of the name
@@ -108,41 +108,41 @@ func newTTLRule(nextAction string, args ...string) (Rule, error) {
 			return &exactTTLRule{
 				nextAction,
 				plugin.Name(args[1]).Normalize(),
-				ResponseRule{
+				[]ResponseRule{{
 					Active: true,
 					Type:   "ttl",
 					TTL:    ttl,
-				},
+				}},
 			}, nil
 		case PrefixMatch:
 			return &prefixTTLRule{
 				nextAction,
 				plugin.Name(args[1]).Normalize(),
-				ResponseRule{
+				[]ResponseRule{{
 					Active: true,
 					Type:   "ttl",
 					TTL:    ttl,
-				},
+				}},
 			}, nil
 		case SuffixMatch:
 			return &suffixTTLRule{
 				nextAction,
 				plugin.Name(args[1]).Normalize(),
-				ResponseRule{
+				[]ResponseRule{{
 					Active: true,
 					Type:   "ttl",
 					TTL:    ttl,
-				},
+				}},
 			}, nil
 		case SubstringMatch:
 			return &substringTTLRule{
 				nextAction,
 				plugin.Name(args[1]).Normalize(),
-				ResponseRule{
+				[]ResponseRule{{
 					Active: true,
 					Type:   "ttl",
 					TTL:    ttl,
-				},
+				}},
 			}, nil
 		case RegexMatch:
 			regexPattern, err := regexp.Compile(args[1])
@@ -152,11 +152,11 @@ func newTTLRule(nextAction string, args ...string) (Rule, error) {
 			return &regexTTLRule{
 				nextAction,
 				regexPattern,
-				ResponseRule{
+				[]ResponseRule{{
 					Active: true,
 					Type:   "ttl",
 					TTL:    ttl,
-				},
+				}},
 			}, nil
 		default:
 			return nil, fmt.Errorf("ttl rule supports only exact, prefix, suffix, substring, and regex name matching")
@@ -168,11 +168,11 @@ func newTTLRule(nextAction string, args ...string) (Rule, error) {
 	return &exactTTLRule{
 		nextAction,
 		plugin.Name(args[0]).Normalize(),
-		ResponseRule{
+		[]ResponseRule{{
 			Active: true,
 			Type:   "ttl",
 			TTL:    ttl,
-		},
+		}},
 	}, nil
 }
 
@@ -183,29 +183,29 @@ func (rule *suffixTTLRule) Mode() string    { return rule.NextAction }
 func (rule *substringTTLRule) Mode() string { return rule.NextAction }
 func (rule *regexTTLRule) Mode() string     { return rule.NextAction }
 
-// GetResponseRule returns a rule to rewrite the response with. Currently not implemented.
-func (rule *exactTTLRule) GetResponseRule() ResponseRule {
-	return rule.ResponseRule
+// GetResponseRules returns rules to rewrite the response with. Currently not implemented.
+func (rule *exactTTLRule) GetResponseRules() []ResponseRule {
+	return rule.ResponseRules
 }
 
-// GetResponseRule returns a rule to rewrite the response with. Currently not implemented.
-func (rule *prefixTTLRule) GetResponseRule() ResponseRule {
-	return rule.ResponseRule
+// GetResponseRules returns rules to rewrite the response with. Currently not implemented.
+func (rule *prefixTTLRule) GetResponseRules() []ResponseRule {
+	return rule.ResponseRules
 }
 
-// GetResponseRule returns a rule to rewrite the response with. Currently not implemented.
-func (rule *suffixTTLRule) GetResponseRule() ResponseRule {
-	return rule.ResponseRule
+// GetResponseRules returns rules to rewrite the response with. Currently not implemented.
+func (rule *suffixTTLRule) GetResponseRules() []ResponseRule {
+	return rule.ResponseRules
 }
 
-// GetResponseRule returns a rule to rewrite the response with. Currently not implemented.
-func (rule *substringTTLRule) GetResponseRule() ResponseRule {
-	return rule.ResponseRule
+// GetResponseRules returns rules to rewrite the response with. Currently not implemented.
+func (rule *substringTTLRule) GetResponseRules() []ResponseRule {
+	return rule.ResponseRules
 }
 
-// GetResponseRule returns a rule to rewrite the response with.
-func (rule *regexTTLRule) GetResponseRule() ResponseRule {
-	return rule.ResponseRule
+// GetResponseRules returns rules to rewrite the response with.
+func (rule *regexTTLRule) GetResponseRules() []ResponseRule {
+	return rule.ResponseRules
 }
 
 // validTTL returns true if v is valid TTL value.

plugin/rewrite/type.go

@@ -44,5 +44,5 @@ func (rule *typeRule) Rewrite(ctx context.Context, state request.Request) Result
 // Mode returns the processing mode.
 func (rule *typeRule) Mode() string { return rule.nextAction }
 
-// GetResponseRule return a rule to rewrite the response with. Currently not implemented.
-func (rule *typeRule) GetResponseRule() ResponseRule { return ResponseRule{} }
+// GetResponseRules return rules to rewrite the response with. Currently not implemented.
+func (rule *typeRule) GetResponseRules() []ResponseRule { return []ResponseRule{} }

plugin/test/helpers.go

@@ -99,6 +99,9 @@ func DNSKEY(rr string) *dns.DNSKEY { r, _ := dns.NewRR(rr); return r.(*dns.DNSKE
 // DS returns a DS record from rr. It panics on errors.
 func DS(rr string) *dns.DS { r, _ := dns.NewRR(rr); return r.(*dns.DS) }
 
+// NAPTR returns a NAPTR record from rr. It panics on errors.
+func NAPTR(rr string) *dns.NAPTR { r, _ := dns.NewRR(rr); return r.(*dns.NAPTR) }
+
 // OPT returns an OPT record with UDP buffer size set to bufsize and the DO bit set to do.
 func OPT(bufsize int, do bool) *dns.OPT {
 	o := new(dns.OPT)