1 /*
2 * Copyright (C) 2016 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 specic language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "libappfuse/FuseBridgeLoop.h"
18
19 #include <sys/epoll.h>
20 #include <sys/socket.h>
21
22 #include <unordered_map>
23
24 #include <android-base/logging.h>
25 #include <android-base/unique_fd.h>
26
27 #include "libappfuse/EpollController.h"
28
29 namespace android {
30 namespace fuse {
31 namespace {
32
33 enum class FuseBridgeState { kWaitToReadEither, kWaitToReadProxy, kWaitToWriteProxy, kClosing };
34
35 struct FuseBridgeEntryEvent {
36 FuseBridgeEntry* entry;
37 int events;
38 };
39
GetObservedEvents(FuseBridgeState state,int * device_events,int * proxy_events)40 void GetObservedEvents(FuseBridgeState state, int* device_events, int* proxy_events) {
41 switch (state) {
42 case FuseBridgeState::kWaitToReadEither:
43 *device_events = EPOLLIN;
44 *proxy_events = EPOLLIN;
45 return;
46 case FuseBridgeState::kWaitToReadProxy:
47 *device_events = 0;
48 *proxy_events = EPOLLIN;
49 return;
50 case FuseBridgeState::kWaitToWriteProxy:
51 *device_events = 0;
52 *proxy_events = EPOLLOUT;
53 return;
54 case FuseBridgeState::kClosing:
55 *device_events = 0;
56 *proxy_events = 0;
57 return;
58 }
59 }
60
LogResponseError(const std::string & message,const FuseResponse & response)61 void LogResponseError(const std::string& message, const FuseResponse& response) {
62 LOG(ERROR) << message << ": header.len=" << response.header.len
63 << " header.error=" << response.header.error
64 << " header.unique=" << response.header.unique;
65 }
66 }
67
68 class FuseBridgeEntry {
69 public:
FuseBridgeEntry(int mount_id,base::unique_fd && dev_fd,base::unique_fd && proxy_fd)70 FuseBridgeEntry(int mount_id, base::unique_fd&& dev_fd, base::unique_fd&& proxy_fd)
71 : mount_id_(mount_id),
72 device_fd_(std::move(dev_fd)),
73 proxy_fd_(std::move(proxy_fd)),
74 state_(FuseBridgeState::kWaitToReadEither),
75 last_state_(FuseBridgeState::kWaitToReadEither),
76 last_device_events_({this, 0}),
77 last_proxy_events_({this, 0}),
78 open_count_(0) {}
79
80 // Transfer bytes depends on availability of FDs and the internal |state_|.
Transfer(FuseBridgeLoopCallback * callback)81 void Transfer(FuseBridgeLoopCallback* callback) {
82 constexpr int kUnexpectedEventMask = ~(EPOLLIN | EPOLLOUT);
83 const bool unexpected_event = (last_device_events_.events & kUnexpectedEventMask) ||
84 (last_proxy_events_.events & kUnexpectedEventMask);
85 const bool device_read_ready = last_device_events_.events & EPOLLIN;
86 const bool proxy_read_ready = last_proxy_events_.events & EPOLLIN;
87 const bool proxy_write_ready = last_proxy_events_.events & EPOLLOUT;
88
89 last_state_ = state_;
90 last_device_events_.events = 0;
91 last_proxy_events_.events = 0;
92
93 LOG(VERBOSE) << "Transfer device_read_ready=" << device_read_ready
94 << " proxy_read_ready=" << proxy_read_ready
95 << " proxy_write_ready=" << proxy_write_ready;
96
97 if (unexpected_event) {
98 LOG(ERROR) << "Invalid epoll event is observed";
99 state_ = FuseBridgeState::kClosing;
100 return;
101 }
102
103 switch (state_) {
104 case FuseBridgeState::kWaitToReadEither:
105 if (proxy_read_ready) {
106 state_ = ReadFromProxy();
107 } else if (device_read_ready) {
108 state_ = ReadFromDevice(callback);
109 }
110 return;
111
112 case FuseBridgeState::kWaitToReadProxy:
113 CHECK(proxy_read_ready);
114 state_ = ReadFromProxy();
115 return;
116
117 case FuseBridgeState::kWaitToWriteProxy:
118 CHECK(proxy_write_ready);
119 state_ = WriteToProxy();
120 return;
121
122 case FuseBridgeState::kClosing:
123 return;
124 }
125 }
126
IsClosing() const127 bool IsClosing() const { return state_ == FuseBridgeState::kClosing; }
128
mount_id() const129 int mount_id() const { return mount_id_; }
130
131 private:
132 friend class BridgeEpollController;
133
ReadFromProxy()134 FuseBridgeState ReadFromProxy() {
135 switch (buffer_.response.ReadOrAgain(proxy_fd_)) {
136 case ResultOrAgain::kSuccess:
137 break;
138 case ResultOrAgain::kFailure:
139 return FuseBridgeState::kClosing;
140 case ResultOrAgain::kAgain:
141 return FuseBridgeState::kWaitToReadProxy;
142 }
143
144 if (!buffer_.response.Write(device_fd_)) {
145 LogResponseError("Failed to write a reply from proxy to device", buffer_.response);
146 return FuseBridgeState::kClosing;
147 }
148
149 auto it = opcode_map_.find(buffer_.response.header.unique);
150 if (it != opcode_map_.end()) {
151 switch (it->second) {
152 case FUSE_OPEN:
153 if (buffer_.response.header.error == fuse::kFuseSuccess) {
154 open_count_++;
155 }
156 break;
157
158 case FUSE_RELEASE:
159 if (open_count_ > 0) {
160 open_count_--;
161 } else {
162 LOG(WARNING) << "Unexpected FUSE_RELEASE before opening a file.";
163 break;
164 }
165 if (open_count_ == 0) {
166 return FuseBridgeState::kClosing;
167 }
168 break;
169 }
170 opcode_map_.erase(it);
171 }
172
173 return FuseBridgeState::kWaitToReadEither;
174 }
175
ReadFromDevice(FuseBridgeLoopCallback * callback)176 FuseBridgeState ReadFromDevice(FuseBridgeLoopCallback* callback) {
177 LOG(VERBOSE) << "ReadFromDevice";
178 if (!buffer_.request.Read(device_fd_)) {
179 return FuseBridgeState::kClosing;
180 }
181
182 const uint32_t opcode = buffer_.request.header.opcode;
183 const uint64_t unique = buffer_.request.header.unique;
184 LOG(VERBOSE) << "Read a fuse packet, opcode=" << opcode << " unique=" << unique;
185 if (unique == 0) {
186 return FuseBridgeState::kWaitToReadEither;
187 }
188 switch (opcode) {
189 case FUSE_FORGET:
190 // Do not reply to FUSE_FORGET.
191 return FuseBridgeState::kWaitToReadEither;
192
193 case FUSE_LOOKUP:
194 case FUSE_GETATTR:
195 case FUSE_OPEN:
196 case FUSE_READ:
197 case FUSE_WRITE:
198 case FUSE_RELEASE:
199 case FUSE_FSYNC:
200 if (opcode == FUSE_OPEN || opcode == FUSE_RELEASE) {
201 opcode_map_.emplace(buffer_.request.header.unique, opcode);
202 }
203 return WriteToProxy();
204
205 case FUSE_INIT:
206 buffer_.HandleInit();
207 break;
208
209 default:
210 buffer_.HandleNotImpl();
211 break;
212 }
213
214 if (!buffer_.response.Write(device_fd_)) {
215 LogResponseError("Failed to write a response to device", buffer_.response);
216 return FuseBridgeState::kClosing;
217 }
218
219 if (opcode == FUSE_INIT) {
220 callback->OnMount(mount_id_);
221 }
222
223 return FuseBridgeState::kWaitToReadEither;
224 }
225
WriteToProxy()226 FuseBridgeState WriteToProxy() {
227 switch (buffer_.request.WriteOrAgain(proxy_fd_)) {
228 case ResultOrAgain::kSuccess:
229 return FuseBridgeState::kWaitToReadEither;
230 case ResultOrAgain::kFailure:
231 LOG(ERROR) << "Failed to write a request to proxy:"
232 << " header.len=" << buffer_.request.header.len
233 << " header.opcode=" << buffer_.request.header.opcode
234 << " header.unique=" << buffer_.request.header.unique
235 << " header.nodeid=" << buffer_.request.header.nodeid;
236 return FuseBridgeState::kClosing;
237 case ResultOrAgain::kAgain:
238 return FuseBridgeState::kWaitToWriteProxy;
239 }
240 }
241
242 const int mount_id_;
243 base::unique_fd device_fd_;
244 base::unique_fd proxy_fd_;
245 FuseBuffer buffer_;
246 FuseBridgeState state_;
247 FuseBridgeState last_state_;
248 FuseBridgeEntryEvent last_device_events_;
249 FuseBridgeEntryEvent last_proxy_events_;
250
251 // Remember map between unique and opcode in fuse_in_header so that we can
252 // refer the opcode later.
253 std::unordered_map<uint64_t, uint32_t> opcode_map_;
254
255 int open_count_;
256
257 DISALLOW_COPY_AND_ASSIGN(FuseBridgeEntry);
258 };
259
260 class BridgeEpollController : private EpollController {
261 public:
BridgeEpollController(base::unique_fd && poll_fd)262 BridgeEpollController(base::unique_fd&& poll_fd) : EpollController(std::move(poll_fd)) {}
263
AddBridgePoll(FuseBridgeEntry * bridge) const264 bool AddBridgePoll(FuseBridgeEntry* bridge) const {
265 return InvokeControl(EPOLL_CTL_ADD, bridge);
266 }
267
UpdateOrDeleteBridgePoll(FuseBridgeEntry * bridge) const268 bool UpdateOrDeleteBridgePoll(FuseBridgeEntry* bridge) const {
269 return InvokeControl(
270 bridge->state_ != FuseBridgeState::kClosing ? EPOLL_CTL_MOD : EPOLL_CTL_DEL, bridge);
271 }
272
Wait(size_t bridge_count,std::unordered_set<FuseBridgeEntry * > * entries_out)273 bool Wait(size_t bridge_count, std::unordered_set<FuseBridgeEntry*>* entries_out) {
274 CHECK(entries_out);
275 const size_t event_count = std::max<size_t>(bridge_count * 2, 1);
276 if (!EpollController::Wait(event_count)) {
277 return false;
278 }
279 entries_out->clear();
280 for (const auto& event : events()) {
281 FuseBridgeEntryEvent* const entry_event =
282 reinterpret_cast<FuseBridgeEntryEvent*>(event.data.ptr);
283 entry_event->events = event.events;
284 entries_out->insert(entry_event->entry);
285 }
286 return true;
287 }
288
289 private:
InvokeControl(int op,FuseBridgeEntry * bridge) const290 bool InvokeControl(int op, FuseBridgeEntry* bridge) const {
291 LOG(VERBOSE) << "InvokeControl op=" << op << " bridge=" << bridge->mount_id_
292 << " state=" << static_cast<int>(bridge->state_)
293 << " last_state=" << static_cast<int>(bridge->last_state_);
294
295 int last_device_events;
296 int last_proxy_events;
297 int device_events;
298 int proxy_events;
299 GetObservedEvents(bridge->last_state_, &last_device_events, &last_proxy_events);
300 GetObservedEvents(bridge->state_, &device_events, &proxy_events);
301 bool result = true;
302 if (op != EPOLL_CTL_MOD || last_device_events != device_events) {
303 result &= EpollController::InvokeControl(op, bridge->device_fd_, device_events,
304 &bridge->last_device_events_);
305 }
306 if (op != EPOLL_CTL_MOD || last_proxy_events != proxy_events) {
307 result &= EpollController::InvokeControl(op, bridge->proxy_fd_, proxy_events,
308 &bridge->last_proxy_events_);
309 }
310 return result;
311 }
312 };
313
FuseBridgeLoop()314 FuseBridgeLoop::FuseBridgeLoop() : opened_(true) {
315 base::unique_fd epoll_fd(epoll_create1(EPOLL_CLOEXEC));
316 if (epoll_fd.get() == -1) {
317 PLOG(ERROR) << "Failed to open FD for epoll";
318 opened_ = false;
319 return;
320 }
321 epoll_controller_.reset(new BridgeEpollController(std::move(epoll_fd)));
322 }
323
~FuseBridgeLoop()324 FuseBridgeLoop::~FuseBridgeLoop() { CHECK(bridges_.empty()); }
325
AddBridge(int mount_id,base::unique_fd dev_fd,base::unique_fd proxy_fd)326 bool FuseBridgeLoop::AddBridge(int mount_id, base::unique_fd dev_fd, base::unique_fd proxy_fd) {
327 LOG(VERBOSE) << "Adding bridge " << mount_id;
328
329 std::unique_ptr<FuseBridgeEntry> bridge(
330 new FuseBridgeEntry(mount_id, std::move(dev_fd), std::move(proxy_fd)));
331 std::lock_guard<std::mutex> lock(mutex_);
332 if (!opened_) {
333 LOG(ERROR) << "Tried to add a mount to a closed bridge";
334 return false;
335 }
336 if (bridges_.count(mount_id)) {
337 LOG(ERROR) << "Tried to add a mount point that has already been added";
338 return false;
339 }
340 if (!epoll_controller_->AddBridgePoll(bridge.get())) {
341 return false;
342 }
343
344 bridges_.emplace(mount_id, std::move(bridge));
345 return true;
346 }
347
ProcessEventLocked(const std::unordered_set<FuseBridgeEntry * > & entries,FuseBridgeLoopCallback * callback)348 bool FuseBridgeLoop::ProcessEventLocked(const std::unordered_set<FuseBridgeEntry*>& entries,
349 FuseBridgeLoopCallback* callback) {
350 for (auto entry : entries) {
351 entry->Transfer(callback);
352 if (!epoll_controller_->UpdateOrDeleteBridgePoll(entry)) {
353 return false;
354 }
355 if (entry->IsClosing()) {
356 const int mount_id = entry->mount_id();
357 bridges_.erase(mount_id);
358 callback->OnClosed(mount_id);
359 if (bridges_.size() == 0) {
360 // All bridges are now closed.
361 return false;
362 }
363 }
364 }
365 return true;
366 }
367
Start(FuseBridgeLoopCallback * callback)368 void FuseBridgeLoop::Start(FuseBridgeLoopCallback* callback) {
369 LOG(DEBUG) << "Start fuse bridge loop";
370 std::unordered_set<FuseBridgeEntry*> entries;
371 while (true) {
372 const bool wait_result = epoll_controller_->Wait(bridges_.size(), &entries);
373 LOG(VERBOSE) << "Receive epoll events";
374 {
375 std::lock_guard<std::mutex> lock(mutex_);
376 if (!(wait_result && ProcessEventLocked(entries, callback))) {
377 for (auto it = bridges_.begin(); it != bridges_.end();) {
378 callback->OnClosed(it->second->mount_id());
379 it = bridges_.erase(it);
380 }
381 opened_ = false;
382 return;
383 }
384 }
385 }
386 }
387
388 } // namespace fuse
389 } // namespace android
390