1/*
2 * Copyright (C) 2017 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#define LOG_TAG "DnsTlsDispatcher"
18//#define LOG_NDEBUG 0
19
20#include "dns/DnsTlsDispatcher.h"
21
22#include "log/log.h"
23
24namespace android {
25namespace net {
26
27using netdutils::Slice;
28
29// static
30std::mutex DnsTlsDispatcher::sLock;
31
32std::list<DnsTlsServer> DnsTlsDispatcher::getOrderedServerList(
33        const std::list<DnsTlsServer> &tlsServers, unsigned mark) const {
34    // Our preferred DnsTlsServer order is:
35    //     1) reuse existing IPv6 connections
36    //     2) reuse existing IPv4 connections
37    //     3) establish new IPv6 connections
38    //     4) establish new IPv4 connections
39    std::list<DnsTlsServer> existing6;
40    std::list<DnsTlsServer> existing4;
41    std::list<DnsTlsServer> new6;
42    std::list<DnsTlsServer> new4;
43
44    // Pull out any servers for which we might have existing connections and
45    // place them at the from the list of servers to try.
46    {
47        std::lock_guard<std::mutex> guard(sLock);
48
49        for (const auto& tlsServer : tlsServers) {
50            const Key key = std::make_pair(mark, tlsServer);
51            if (mStore.find(key) != mStore.end()) {
52                switch (tlsServer.ss.ss_family) {
53                    case AF_INET:
54                        existing4.push_back(tlsServer);
55                        break;
56                    case AF_INET6:
57                        existing6.push_back(tlsServer);
58                        break;
59                }
60            } else {
61                switch (tlsServer.ss.ss_family) {
62                    case AF_INET:
63                        new4.push_back(tlsServer);
64                        break;
65                    case AF_INET6:
66                        new6.push_back(tlsServer);
67                        break;
68                }
69            }
70        }
71    }
72
73    auto& out = existing6;
74    out.splice(out.cend(), existing4);
75    out.splice(out.cend(), new6);
76    out.splice(out.cend(), new4);
77    return out;
78}
79
80DnsTlsTransport::Response DnsTlsDispatcher::query(
81        const std::list<DnsTlsServer> &tlsServers, unsigned mark,
82        const Slice query, const Slice ans, int *resplen) {
83    const std::list<DnsTlsServer> orderedServers(getOrderedServerList(tlsServers, mark));
84
85    if (orderedServers.empty()) ALOGW("Empty DnsTlsServer list");
86
87    DnsTlsTransport::Response code = DnsTlsTransport::Response::internal_error;
88    for (const auto& server : orderedServers) {
89        code = this->query(server, mark, query, ans, resplen);
90        switch (code) {
91            // These response codes are valid responses and not expected to
92            // change if another server is queried.
93            case DnsTlsTransport::Response::success:
94            case DnsTlsTransport::Response::limit_error:
95                return code;
96                break;
97            // These response codes might differ when trying other servers, so
98            // keep iterating to see if we can get a different (better) result.
99            case DnsTlsTransport::Response::network_error:
100            case DnsTlsTransport::Response::internal_error:
101                continue;
102                break;
103            // No "default" statement.
104        }
105    }
106
107    return code;
108}
109
110DnsTlsTransport::Response DnsTlsDispatcher::query(const DnsTlsServer& server, unsigned mark,
111                                                  const Slice query,
112                                                  const Slice ans, int *resplen) {
113    const Key key = std::make_pair(mark, server);
114    Transport* xport;
115    {
116        std::lock_guard<std::mutex> guard(sLock);
117        auto it = mStore.find(key);
118        if (it == mStore.end()) {
119            xport = new Transport(server, mark, mFactory.get());
120            mStore[key].reset(xport);
121        } else {
122            xport = it->second.get();
123        }
124        ++xport->useCount;
125    }
126
127    ALOGV("Sending query of length %zu", query.size());
128    auto res = xport->transport.query(query);
129    ALOGV("Awaiting response");
130    const auto& result = res.get();
131    DnsTlsTransport::Response code = result.code;
132    if (code == DnsTlsTransport::Response::success) {
133        if (result.response.size() > ans.size()) {
134            ALOGV("Response too large: %zu > %zu", result.response.size(), ans.size());
135            code = DnsTlsTransport::Response::limit_error;
136        } else {
137            ALOGV("Got response successfully");
138            *resplen = result.response.size();
139            netdutils::copy(ans, netdutils::makeSlice(result.response));
140        }
141    } else {
142        ALOGV("Query failed: %u", (unsigned int) code);
143    }
144
145    auto now = std::chrono::steady_clock::now();
146    {
147        std::lock_guard<std::mutex> guard(sLock);
148        --xport->useCount;
149        xport->lastUsed = now;
150        cleanup(now);
151    }
152    return code;
153}
154
155// This timeout effectively controls how long to keep SSL session tickets.
156static constexpr std::chrono::minutes IDLE_TIMEOUT(5);
157void DnsTlsDispatcher::cleanup(std::chrono::time_point<std::chrono::steady_clock> now) {
158    // To avoid scanning mStore after every query, return early if a cleanup has been
159    // performed recently.
160    if (now - mLastCleanup < IDLE_TIMEOUT) {
161        return;
162    }
163    for (auto it = mStore.begin(); it != mStore.end();) {
164        auto& s = it->second;
165        if (s->useCount == 0 && now - s->lastUsed > IDLE_TIMEOUT) {
166            it = mStore.erase(it);
167        } else {
168            ++it;
169        }
170    }
171    mLastCleanup = now;
172}
173
174}  // end of namespace net
175}  // end of namespace android
176