1 /**
2  * Copyright (c) 2020, The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *     http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #pragma once
18 
19 #include <climits>
20 #include <functional>
21 #include <map>
22 #include <mutex>
23 #include <string>
24 #include <string_view>
25 
26 #include <android-base/thread_annotations.h>
27 #include <netdutils/DumpWriter.h>
28 
29 namespace android::net {
30 
31 // TODO: Add some way to update the stored experiment flags periodically.
32 // TODO: Refactor this class and make things easier. (e.g. remove string map.)
33 class Experiments {
34   public:
35     using GetExperimentFlagIntFunction = std::function<int(const std::string&, int)>;
36     static Experiments* getInstance();
37     int getFlag(std::string_view key, int defaultValue) const EXCLUDES(mMutex);
38     void update();
39     void dump(netdutils::DumpWriter& dw) const EXCLUDES(mMutex);
40 
41     Experiments(Experiments const&) = delete;
42     void operator=(Experiments const&) = delete;
43 
44   private:
45     explicit Experiments(GetExperimentFlagIntFunction getExperimentFlagIntFunction);
46     Experiments() = delete;
47     void updateInternal() EXCLUDES(mMutex);
48     mutable std::mutex mMutex;
49     std::map<std::string_view, int> mFlagsMapInt GUARDED_BY(mMutex);
50     static constexpr const char* const kExperimentFlagKeyList[] = {
51             "doh_early_data",
52             "doh_idle_timeout_ms",
53             "doh_probe_timeout_ms",
54             "doh_query_timeout_ms",
55             "doh_session_resumption",
56             "dot_async_handshake",
57             "dot_connect_timeout_ms",
58             "dot_maxtries",
59             "dot_query_timeout_ms",
60             "dot_quick_fallback",
61             "dot_revalidation_threshold",
62             "dot_validation_latency_factor",
63             "dot_validation_latency_offset_ms",
64             "dot_xport_unusable_threshold",
65             "fail_fast_on_uid_network_blocking",
66             "keep_listening_udp",
67             "max_cache_entries",
68             "max_queries_global",
69             "mdns_resolution",
70             "parallel_lookup_sleep_time",
71             "retransmission_time_interval",
72             "retry_count",
73             "sort_nameservers",
74     };
75     // This value is used in updateInternal as the default value if any flags can't be found.
76     static constexpr int kFlagIntDefault = INT_MIN;
77     // For testing.
78     friend class ExperimentsTest;
79     const GetExperimentFlagIntFunction mGetExperimentFlagIntFunction;
80 };
81 
82 }  // namespace android::net
83