cmd/derper: add BenchmarkHandleBootstrapDNS

Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>

cmd/derper/bootstrap_dns_test.go

@@ -0,0 +1,35 @@
+// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"net/http"
+	"testing"
+)
+
+func BenchmarkHandleBootstrapDNS(b *testing.B) {
+	prev := *bootstrapDNS
+	*bootstrapDNS = "log.tailscale.io,login.tailscale.com,controlplane.tailscale.com,login.us.tailscale.com"
+	defer func() {
+		*bootstrapDNS = prev
+	}()
+	refreshBootstrapDNS()
+	w := new(bitbucketResponseWriter)
+	b.ReportAllocs()
+	b.ResetTimer()
+	b.RunParallel(func(b *testing.PB) {
+		for b.Next() {
+			handleBootstrapDNS(w, nil)
+		}
+	})
+}
+
+type bitbucketResponseWriter struct{}
+
+func (b *bitbucketResponseWriter) Header() http.Header { return make(http.Header) }
+
+func (b *bitbucketResponseWriter) Write(p []byte) (int, error) { return len(p), nil }
+
+func (b *bitbucketResponseWriter) WriteHeader(statusCode int) {}