summaryrefslogtreecommitdiffstats
blob: 8b0c53eb261b5c316ed39eec5cea7e01001da9e1 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
/*
 * Copyright (C) 2016 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 specic language governing permissions and
 * limitations under the License.
 */

#include "libappfuse/FuseBridgeLoop.h"

#include <sys/epoll.h>
#include <sys/socket.h>

#include <unordered_map>

#include <android-base/logging.h>
#include <android-base/unique_fd.h>

#include "libappfuse/EpollController.h"

namespace android {
namespace fuse {
namespace {

enum class FuseBridgeState { kWaitToReadEither, kWaitToReadProxy, kWaitToWriteProxy, kClosing };

struct FuseBridgeEntryEvent {
    FuseBridgeEntry* entry;
    int events;
};

void GetObservedEvents(FuseBridgeState state, int* device_events, int* proxy_events) {
    switch (state) {
        case FuseBridgeState::kWaitToReadEither:
            *device_events = EPOLLIN;
            *proxy_events = EPOLLIN;
            return;
        case FuseBridgeState::kWaitToReadProxy:
            *device_events = 0;
            *proxy_events = EPOLLIN;
            return;
        case FuseBridgeState::kWaitToWriteProxy:
            *device_events = 0;
            *proxy_events = EPOLLOUT;
            return;
        case FuseBridgeState::kClosing:
            *device_events = 0;
            *proxy_events = 0;
            return;
    }
}

void LogResponseError(const std::string& message, const FuseResponse& response) {
    LOG(ERROR) << message << ": header.len=" << response.header.len
               << " header.error=" << response.header.error
               << " header.unique=" << response.header.unique;
}
}

class FuseBridgeEntry {
  public:
    FuseBridgeEntry(int mount_id, base::unique_fd&& dev_fd, base::unique_fd&& proxy_fd)
        : mount_id_(mount_id),
          device_fd_(std::move(dev_fd)),
          proxy_fd_(std::move(proxy_fd)),
          state_(FuseBridgeState::kWaitToReadEither),
          last_state_(FuseBridgeState::kWaitToReadEither),
          last_device_events_({this, 0}),
          last_proxy_events_({this, 0}),
          open_count_(0) {}

    // Transfer bytes depends on availability of FDs and the internal |state_|.
    void Transfer(FuseBridgeLoopCallback* callback) {
        constexpr int kUnexpectedEventMask = ~(EPOLLIN | EPOLLOUT);
        const bool unexpected_event = (last_device_events_.events & kUnexpectedEventMask) ||
                                      (last_proxy_events_.events & kUnexpectedEventMask);
        const bool device_read_ready = last_device_events_.events & EPOLLIN;
        const bool proxy_read_ready = last_proxy_events_.events & EPOLLIN;
        const bool proxy_write_ready = last_proxy_events_.events & EPOLLOUT;

        last_device_events_.events = 0;
        last_proxy_events_.events = 0;

        LOG(VERBOSE) << "Transfer device_read_ready=" << device_read_ready
                     << " proxy_read_ready=" << proxy_read_ready
                     << " proxy_write_ready=" << proxy_write_ready;

        if (unexpected_event) {
            LOG(ERROR) << "Invalid epoll event is observed";
            state_ = FuseBridgeState::kClosing;
            return;
        }

        switch (state_) {
            case FuseBridgeState::kWaitToReadEither:
                if (proxy_read_ready) {
                    state_ = ReadFromProxy();
                } else if (device_read_ready) {
                    state_ = ReadFromDevice(callback);
                }
                return;

            case FuseBridgeState::kWaitToReadProxy:
                CHECK(proxy_read_ready);
                state_ = ReadFromProxy();
                return;

            case FuseBridgeState::kWaitToWriteProxy:
                CHECK(proxy_write_ready);
                state_ = WriteToProxy();
                return;

            case FuseBridgeState::kClosing:
                return;
        }
    }

    bool IsClosing() const { return state_ == FuseBridgeState::kClosing; }

    int mount_id() const { return mount_id_; }

  private:
    friend class BridgeEpollController;

    FuseBridgeState ReadFromProxy() {
        switch (buffer_.response.ReadOrAgain(proxy_fd_)) {
            case ResultOrAgain::kSuccess:
                break;
            case ResultOrAgain::kFailure:
                return FuseBridgeState::kClosing;
            case ResultOrAgain::kAgain:
                return FuseBridgeState::kWaitToReadProxy;
        }

        if (!buffer_.response.Write(device_fd_)) {
            LogResponseError("Failed to write a reply from proxy to device", buffer_.response);
            return FuseBridgeState::kClosing;
        }

        auto it = opcode_map_.find(buffer_.response.header.unique);
        if (it != opcode_map_.end()) {
            switch (it->second) {
                case FUSE_OPEN:
                    if (buffer_.response.header.error == fuse::kFuseSuccess) {
                        open_count_++;
                    }
                    break;

                case FUSE_RELEASE:
                    if (open_count_ > 0) {
                        open_count_--;
                    } else {
                        LOG(WARNING) << "Unexpected FUSE_RELEASE before opening a file.";
                        break;
                    }
                    if (open_count_ == 0) {
                        return FuseBridgeState::kClosing;
                    }
                    break;
            }
            opcode_map_.erase(it);
        }

        return FuseBridgeState::kWaitToReadEither;
    }

    FuseBridgeState ReadFromDevice(FuseBridgeLoopCallback* callback) {
        LOG(VERBOSE) << "ReadFromDevice";
        if (!buffer_.request.Read(device_fd_)) {
            return FuseBridgeState::kClosing;
        }

        const uint32_t opcode = buffer_.request.header.opcode;
        const uint64_t unique = buffer_.request.header.unique;
        LOG(VERBOSE) << "Read a fuse packet, opcode=" << opcode << " unique=" << unique;
        if (unique == 0) {
            return FuseBridgeState::kWaitToReadEither;
        }
        switch (opcode) {
            case FUSE_FORGET:
                // Do not reply to FUSE_FORGET.
                return FuseBridgeState::kWaitToReadEither;

            case FUSE_LOOKUP:
            case FUSE_GETATTR:
            case FUSE_OPEN:
            case FUSE_READ:
            case FUSE_WRITE:
            case FUSE_RELEASE:
            case FUSE_FSYNC:
                if (opcode == FUSE_OPEN || opcode == FUSE_RELEASE) {
                    opcode_map_.emplace(buffer_.request.header.unique, opcode);
                }
                return WriteToProxy();

            case FUSE_INIT:
                buffer_.HandleInit();
                break;

            default:
                buffer_.HandleNotImpl();
                break;
        }

        if (!buffer_.response.Write(device_fd_)) {
            LogResponseError("Failed to write a response to device", buffer_.response);
            return FuseBridgeState::kClosing;
        }

        if (opcode == FUSE_INIT) {
            callback->OnMount(mount_id_);
        }

        return FuseBridgeState::kWaitToReadEither;
    }

    FuseBridgeState WriteToProxy() {
        switch (buffer_.request.WriteOrAgain(proxy_fd_)) {
            case ResultOrAgain::kSuccess:
                return FuseBridgeState::kWaitToReadEither;
            case ResultOrAgain::kFailure:
                LOG(ERROR) << "Failed to write a request to proxy:"
                           << " header.len=" << buffer_.request.header.len
                           << " header.opcode=" << buffer_.request.header.opcode
                           << " header.unique=" << buffer_.request.header.unique
                           << " header.nodeid=" << buffer_.request.header.nodeid;
                return FuseBridgeState::kClosing;
            case ResultOrAgain::kAgain:
                return FuseBridgeState::kWaitToWriteProxy;
        }
    }

    const int mount_id_;
    base::unique_fd device_fd_;
    base::unique_fd proxy_fd_;
    FuseBuffer buffer_;
    FuseBridgeState state_;
    FuseBridgeState last_state_;
    FuseBridgeEntryEvent last_device_events_;
    FuseBridgeEntryEvent last_proxy_events_;

    // Remember map between unique and opcode in fuse_in_header so that we can
    // refer the opcode later.
    std::unordered_map<uint64_t, uint32_t> opcode_map_;

    int open_count_;

    DISALLOW_COPY_AND_ASSIGN(FuseBridgeEntry);
};

class BridgeEpollController : private EpollController {
  public:
    BridgeEpollController(base::unique_fd&& poll_fd) : EpollController(std::move(poll_fd)) {}

    bool AddBridgePoll(FuseBridgeEntry* bridge) const {
        return InvokeControl(EPOLL_CTL_ADD, bridge);
    }

    bool UpdateOrDeleteBridgePoll(FuseBridgeEntry* bridge) const {
        return InvokeControl(
            bridge->state_ != FuseBridgeState::kClosing ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, bridge);
    }

    bool Wait(size_t bridge_count, std::unordered_set<FuseBridgeEntry*>* entries_out) {
        CHECK(entries_out);
        const size_t event_count = std::max<size_t>(bridge_count * 2, 1);
        if (!EpollController::Wait(event_count)) {
            return false;
        }
        entries_out->clear();
        for (const auto& event : events()) {
            FuseBridgeEntryEvent* const entry_event =
                reinterpret_cast<FuseBridgeEntryEvent*>(event.data.ptr);
            entry_event->events = event.events;
            entries_out->insert(entry_event->entry);
        }
        return true;
    }

  private:
    bool InvokeControl(int op, FuseBridgeEntry* bridge) const {
        LOG(VERBOSE) << "InvokeControl op=" << op << " bridge=" << bridge->mount_id_
                     << " state=" << static_cast<int>(bridge->state_)
                     << " last_state=" << static_cast<int>(bridge->last_state_);

        int last_device_events;
        int last_proxy_events;
        int device_events;
        int proxy_events;
        GetObservedEvents(bridge->last_state_, &last_device_events, &last_proxy_events);
        GetObservedEvents(bridge->state_, &device_events, &proxy_events);
        bool result = true;
        if (op != EPOLL_CTL_MOD || last_device_events != device_events) {
            result &= EpollController::InvokeControl(op, bridge->device_fd_, device_events,
                                                     &bridge->last_device_events_);
        }
        if (op != EPOLL_CTL_MOD || last_proxy_events != proxy_events) {
            result &= EpollController::InvokeControl(op, bridge->proxy_fd_, proxy_events,
                                                     &bridge->last_proxy_events_);
        }
        return result;
    }
};

FuseBridgeLoop::FuseBridgeLoop() : opened_(true) {
    base::unique_fd epoll_fd(epoll_create1(/* no flag */ 0));
    if (epoll_fd.get() == -1) {
        PLOG(ERROR) << "Failed to open FD for epoll";
        opened_ = false;
        return;
    }
    epoll_controller_.reset(new BridgeEpollController(std::move(epoll_fd)));
}

FuseBridgeLoop::~FuseBridgeLoop() { CHECK(bridges_.empty()); }

bool FuseBridgeLoop::AddBridge(int mount_id, base::unique_fd dev_fd, base::unique_fd proxy_fd) {
    LOG(VERBOSE) << "Adding bridge " << mount_id;

    std::unique_ptr<FuseBridgeEntry> bridge(
        new FuseBridgeEntry(mount_id, std::move(dev_fd), std::move(proxy_fd)));
    std::lock_guard<std::mutex> lock(mutex_);
    if (!opened_) {
        LOG(ERROR) << "Tried to add a mount to a closed bridge";
        return false;
    }
    if (bridges_.count(mount_id)) {
        LOG(ERROR) << "Tried to add a mount point that has already been added";
        return false;
    }
    if (!epoll_controller_->AddBridgePoll(bridge.get())) {
        return false;
    }

    bridges_.emplace(mount_id, std::move(bridge));
    return true;
}

bool FuseBridgeLoop::ProcessEventLocked(const std::unordered_set<FuseBridgeEntry*>& entries,
                                        FuseBridgeLoopCallback* callback) {
    for (auto entry : entries) {
        entry->Transfer(callback);
        if (!epoll_controller_->UpdateOrDeleteBridgePoll(entry)) {
            return false;
        }
        if (entry->IsClosing()) {
            const int mount_id = entry->mount_id();
            callback->OnClosed(mount_id);
            bridges_.erase(mount_id);
            if (bridges_.size() == 0) {
                // All bridges are now closed.
                return false;
            }
        }
    }
    return true;
}

void FuseBridgeLoop::Start(FuseBridgeLoopCallback* callback) {
    LOG(DEBUG) << "Start fuse bridge loop";
    std::unordered_set<FuseBridgeEntry*> entries;
    while (true) {
        const bool wait_result = epoll_controller_->Wait(bridges_.size(), &entries);
        LOG(VERBOSE) << "Receive epoll events";
        {
            std::lock_guard<std::mutex> lock(mutex_);
            if (!(wait_result && ProcessEventLocked(entries, callback))) {
                for (auto it = bridges_.begin(); it != bridges_.end();) {
                    callback->OnClosed(it->second->mount_id());
                    it = bridges_.erase(it);
                }
                opened_ = false;
                return;
            }
        }
    }
}

}  // namespace fuse
}  // namespace android