Refactor, prerequisite for DNS-over-TLS pipelining
This change should have no effect on behavior, but it divides functionality
out into classes in a way that will enable pipelining.
It also adds unit tests for the newly divided functionality.
Test: Unit and integration tests pass.
Bug: 63448521
Change-Id: I08948be304b7a3e4ba10f754ef58bd41db6824c4
diff --git a/server/dns/DnsTlsSessionCache.h b/server/dns/DnsTlsSessionCache.h
new file mode 100644
index 0000000..32b8b55
--- /dev/null
+++ b/server/dns/DnsTlsSessionCache.h
@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _DNS_DNSTLSSESSIONCACHE_H
+#define _DNS_DNSTLSSESSIONCACHE_H
+
+#include <mutex>
+#include <deque>
+
+#include <openssl/ssl.h>
+
+#include <android-base/thread_annotations.h>
+#include <android-base/unique_fd.h>
+
+#include "dns/DnsTlsServer.h"
+
+namespace android {
+namespace net {
+
+// Cache of recently seen SSL_SESSIONs. This is used to support session tickets.
+// This class is thread-safe.
+class DnsTlsSessionCache {
+public:
+ // Prepare SSL objects to use this session cache. These methods must be called
+ // before making use of either object.
+ void prepareSslContext(SSL_CTX* _Nonnull ssl_ctx);
+ bool prepareSsl(SSL* _Nonnull ssl);
+
+ // Get the most recently discovered session. For TLS 1.3 compatibility and
+ // maximum privacy, each session will only be returned once, so the caller
+ // gains ownership of the session. (Here and throughout,
+ // bssl::UniquePtr<SSL_SESSION> is actually serving as a reference counted
+ // pointer.)
+ bssl::UniquePtr<SSL_SESSION> getSession() EXCLUDES(mLock);
+
+private:
+ static constexpr size_t kMaxSize = 5;
+ static int newSessionCallback(SSL* _Nullable ssl, SSL_SESSION* _Nullable session);
+
+ std::mutex mLock;
+ void recordSession(SSL_SESSION* _Nullable session) EXCLUDES(mLock);
+
+ // Queue of sessions, from least recently added to most recently.
+ std::deque<bssl::UniquePtr<SSL_SESSION>> mSessions GUARDED_BY(mLock);
+};
+
+} // end of namespace net
+} // end of namespace android
+
+#endif // _DNS_DNSTLSSESSIONCACHE_H