plugin/rewrite: add rcode as a rewrite option (#6204)

* plugin/forward add ignore_server_failure for masking upstream server faults

Signed-off-by: schou <pschou@users.noreply.github.com>

* Switch from a ignore_server_fail to a rewrite rcode type.

Signed-off-by: schou <pschou@users.noreply.github.com>

* trim down the tests

Signed-off-by: schou <pschou@users.noreply.github.com>

* fixing readme TTL and using map for rcode

Signed-off-by: schou <pschou@users.noreply.github.com>

* add newline

Signed-off-by: schou <pschou@users.noreply.github.com>

---------

Signed-off-by: schou <pschou@users.noreply.github.com>

1 files changed, 72 insertions, 0 deletions

diff --git a/plugin/rewrite/rcode_test.go b/plugin/rewrite/rcode_test.go
new file mode 100644
index 000000000..e40260719
--- /dev/null
+++ b/plugin/rewrite/rcode_test.go
@@ -0,0 +1,72 @@
+package rewrite
+
+import (
+	"testing"
+
+	"github.com/coredns/coredns/plugin/test"
+	"github.com/coredns/coredns/request"
+
+	"github.com/miekg/dns"
+)
+
+func TestNewRCodeRule(t *testing.T) {
+	tests := []struct {
+		next         string
+		args         []string
+		expectedFail bool
+	}{
+		{"stop", []string{"numeric.rcode.coredns.rocks", "2", "0"}, false},
+		{"stop", []string{"too.few.rcode.coredns.rocks", "2"}, true},
+		{"stop", []string{"exact", "too.many.rcode.coredns.rocks", "2", "1", "0"}, true},
+		{"stop", []string{"exact", "match.string.rcode.coredns.rocks", "SERVFAIL", "NOERROR"}, false},
+		{"continue", []string{"regex", `(regex)\.rcode\.(coredns)\.(rocks)`, "FORMERR", "NOERROR"}, false},
+		{"stop", []string{"invalid.rcode.coredns.rocks", "random", "nothing"}, true},
+	}
+	for i, tc := range tests {
+		failed := false
+		rule, err := newRCodeRule(tc.next, tc.args...)
+		if err != nil {
+			failed = true
+		}
+		if !failed && !tc.expectedFail {
+			continue
+		}
+		if failed && tc.expectedFail {
+			continue
+		}
+		t.Fatalf("Test %d: FAIL, expected fail=%t, but received fail=%t: (%s) %s, rule=%v, err=%v", i, tc.expectedFail, failed, tc.next, tc.args, rule, err)
+	}
+	for i, tc := range tests {
+		failed := false
+		tc.args = append([]string{tc.next, "rcode"}, tc.args...)
+		rule, err := newRule(tc.args...)
+		if err != nil {
+			failed = true
+		}
+		if !failed && !tc.expectedFail {
+			continue
+		}
+		if failed && tc.expectedFail {
+			continue
+		}
+		t.Fatalf("Test %d: FAIL, expected fail=%t, but received fail=%t: (%s) %s, rule=%v, err=%v", i, tc.expectedFail, failed, tc.next, tc.args, rule, err)
+	}
+}
+
+func TestRCodeRewrite(t *testing.T) {
+	rule, err := newRCodeRule("stop", []string{"exact", "srv1.coredns.rocks", "SERVFAIL", "FORMERR"}...)
+
+	m := new(dns.Msg)
+	m.SetQuestion("srv1.coredns.rocks.", dns.TypeA)
+	m.Question[0].Qclass = dns.ClassINET
+	m.Answer = []dns.RR{test.A("srv1.coredns.rocks.  5   IN  A  10.0.0.1")}
+	m.MsgHdr.Rcode = dns.RcodeServerFailure
+	request := request.Request{Req: m}
+
+	rcRule, _ := rule.(*exactRCodeRule)
+	var rr dns.RR
+	rcRule.response.RewriteResponse(request.Req, rr)
+	if request.Req.MsgHdr.Rcode != dns.RcodeFormatError {
+		t.Fatalf("RCode rewrite did not apply changes, request=%#v, err=%v", request.Req, err)
+	}
+}