rewrite: fix multi request concurrency issue in cname rewrite (#6407)

* fix concurrent issue with cname rewrite plugin

Signed-off-by: amila <amila.15@cse.mrt.ac.lk>

* add nil check before deref, add AAAA type test case

Signed-off-by: amila <amila.15@cse.mrt.ac.lk>

---------

Signed-off-by: amila <amila.15@cse.mrt.ac.lk>

2 files changed, 35 insertions, 11 deletions

diff --git a/plugin/rewrite/cname_target.go b/plugin/rewrite/cname_target.go
index 068f17fdd..d57bae3b2 100644
--- a/plugin/rewrite/cname_target.go
+++ b/plugin/rewrite/cname_target.go
@@ -25,11 +25,16 @@ type cnameTargetRule struct {
 	paramFromTarget string
 	paramToTarget   string
 	nextAction      string
-	state           request.Request
-	ctx             context.Context
 	Upstream        UpstreamInt // Upstream for looking up external names during the resolution process.
 }
 
+// cnameTargetRuleWithReqState is cname target rewrite rule state
+type cnameTargetRuleWithReqState struct {
+	rule  cnameTargetRule
+	state request.Request
+	ctx   context.Context
+}
+
 func (r *cnameTargetRule) getFromAndToTarget(inputCName string) (from string, to string) {
 	switch r.rewriteType {
 	case ExactMatch:
@@ -62,17 +67,17 @@ func (r *cnameTargetRule) getFromAndToTarget(inputCName string) (from string, to
 	return "", ""
 }
 
-func (r *cnameTargetRule) RewriteResponse(res *dns.Msg, rr dns.RR) {
+func (r *cnameTargetRuleWithReqState) RewriteResponse(res *dns.Msg, rr dns.RR) {
 	// logic to rewrite the cname target of dns response
 	switch rr.Header().Rrtype {
 	case dns.TypeCNAME:
 		// rename the target of the cname response
 		if cname, ok := rr.(*dns.CNAME); ok {
-			fromTarget, toTarget := r.getFromAndToTarget(cname.Target)
+			fromTarget, toTarget := r.rule.getFromAndToTarget(cname.Target)
 			if cname.Target == fromTarget {
 				// create upstream request with the new target with the same qtype
 				r.state.Req.Question[0].Name = toTarget
-				upRes, err := r.Upstream.Lookup(r.ctx, r.state, toTarget, r.state.Req.Question[0].Qtype)
+				upRes, err := r.rule.Upstream.Lookup(r.ctx, r.state, toTarget, r.state.Req.Question[0].Qtype)
 
 				if err != nil {
 					log.Errorf("Error upstream request %v", err)
@@ -133,10 +138,12 @@ func newCNAMERule(nextAction string, args ...string) (Rule, error) {
 
 // Rewrite rewrites the current request.
 func (r *cnameTargetRule) Rewrite(ctx context.Context, state request.Request) (ResponseRules, Result) {
-	if len(r.rewriteType) > 0 && len(r.paramFromTarget) > 0 && len(r.paramToTarget) > 0 {
-		r.state = state
-		r.ctx = ctx
-		return ResponseRules{r}, RewriteDone
+	if r != nil && len(r.rewriteType) > 0 && len(r.paramFromTarget) > 0 && len(r.paramToTarget) > 0 {
+		return ResponseRules{&cnameTargetRuleWithReqState{
+			rule:  *r,
+			state: state,
+			ctx:   ctx,
+		}}, RewriteDone
 	}
 	return nil, RewriteIgnored
 }
diff --git a/plugin/rewrite/cname_target_test.go b/plugin/rewrite/cname_target_test.go
index 04ca01af4..9eee2b8de 100644
--- a/plugin/rewrite/cname_target_test.go
+++ b/plugin/rewrite/cname_target_test.go
@@ -21,8 +21,15 @@ func (u *MockedUpstream) Lookup(ctx context.Context, state request.Request, name
 	m.Authoritative = true
 	switch state.Req.Question[0].Name {
 	case "xyz.example.com.":
-		m.Answer = []dns.RR{
-			test.A("xyz.example.com. 3600 IN A 3.4.5.6"),
+		switch state.Req.Question[0].Qtype {
+		case dns.TypeA:
+			m.Answer = []dns.RR{
+				test.A("xyz.example.com.  3600  IN  A 3.4.5.6"),
+			}
+		case dns.TypeAAAA:
+			m.Answer = []dns.RR{
+				test.AAAA("xyz.example.com.  3600  IN  AAAA 3a01:7e00::f03c:91ff:fe79:234c"),
+			}
 		}
 		return m, nil
 	case "bard.google.com.cdn.cloudflare.net.":
@@ -94,6 +101,16 @@ func doTestCNameTargetTests(rules []Rule, t *testing.T) {
 				test.A("xyz.example.com.  3600  IN  A  3.4.5.6"),
 			},
 		},
+		{"abc.example.com", dns.TypeAAAA,
+			[]dns.RR{
+				test.CNAME("abc.example.com.  5   IN  CNAME  def.example.com."),
+				test.AAAA("def.example.com.   5  IN  AAAA   2a01:7e00::f03c:91ff:fe79:234c"),
+			},
+			[]dns.RR{
+				test.CNAME("abc.example.com.  5   IN  CNAME  xyz.example.com."),
+				test.AAAA("xyz.example.com.  3600  IN  AAAA  3a01:7e00::f03c:91ff:fe79:234c"),
+			},
+		},
 		{"chat.openai.com", dns.TypeA,
 			[]dns.RR{
 				test.CNAME("chat.openai.com.  20   IN  CNAME  chat.openai.com.cdn.cloudflare.net."),