fix(test): deduplicate TSIG test helpers (#8009)

core/dnsserver/tsig_test.go

@@ -0,0 +1,46 @@
+package dnsserver
+
+import (
+	"context"
+	"testing"
+
+	"github.com/miekg/dns"
+)
+
+type tsigStatusCheckPlugin struct {
+	t      *testing.T
+	check  func(*testing.T, error)
+	called chan struct{}
+}
+
+func (p tsigStatusCheckPlugin) Name() string { return "tsig-status-check" }
+
+func (p tsigStatusCheckPlugin) ServeDNS(_ context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
+	p.t.Helper()
+	if p.called != nil {
+		p.called <- struct{}{}
+	}
+	p.check(p.t, w.TsigStatus())
+
+	m := new(dns.Msg)
+	m.SetReply(r)
+	if err := w.WriteMsg(m); err != nil {
+		p.t.Fatalf("WriteMsg() failed: %v", err)
+	}
+	return dns.RcodeSuccess, nil
+}
+
+func mustPackSignedTSIGQuery(t *testing.T, keyName, secret string, tsigTime int64) []byte {
+	t.Helper()
+
+	m := new(dns.Msg)
+	m.SetQuestion("example.com.", dns.TypeA)
+	m.Id = 0
+	m.SetTsig(keyName, dns.HmacSHA256, 300, tsigTime)
+
+	wire, _, err := dns.TsigGenerate(m, secret, "", false)
+	if err != nil {
+		t.Fatalf("dns.TsigGenerate() failed: %v", err)
+	}
+	return wire
+}