libappfuse/FuseBuffer.cc - android-core - Git at Google

 /*
  * 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/FuseBuffer.h"

 #include <inttypes.h>
 #include <string.h>
 #include <unistd.h>

 #include <algorithm>
 #include <type_traits>

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

 #include <android-base/file.h>
 #include <android-base/logging.h>
 #include <android-base/macros.h>

 namespace android {
 namespace fuse {
 namespace {

 constexpr useconds_t kRetrySleepForWriting = 1000;  // 1 ms

 template <typename T>
 bool CheckHeaderLength(const FuseMessage<T>* self, const char* name, size_t max_size) {
     const auto& header = static_cast<const T*>(self)->header;
     if (header.len >= sizeof(header) && header.len <= max_size) {
         return true;
     } else {
         LOG(ERROR) << "Invalid header length is found in " << name << ": " << header.len;
         return false;
     }
 }

 template <typename T>
 ResultOrAgain ReadInternal(FuseMessage<T>* self, int fd, int sockflag) {
     char* const buf = reinterpret_cast<char*>(self);
     const ssize_t result = sockflag ? TEMP_FAILURE_RETRY(recv(fd, buf, sizeof(T), sockflag))
                                     : TEMP_FAILURE_RETRY(read(fd, buf, sizeof(T)));

     switch (result) {
         case 0:
             // Expected EOF.
             return ResultOrAgain::kFailure;
         case -1:
             if (errno == EAGAIN) {
                 return ResultOrAgain::kAgain;
             }
             PLOG(ERROR) << "Failed to read a FUSE message";
             return ResultOrAgain::kFailure;
     }

     const auto& header = static_cast<const T*>(self)->header;
     if (result < static_cast<ssize_t>(sizeof(header))) {
         LOG(ERROR) << "Read bytes " << result << " are shorter than header size " << sizeof(header);
         return ResultOrAgain::kFailure;
     }

     if (!CheckHeaderLength<T>(self, "Read", sizeof(T))) {
         return ResultOrAgain::kFailure;
     }

     if (static_cast<uint32_t>(result) != header.len) {
         LOG(ERROR) << "Read bytes " << result << " are different from header.len " << header.len;
         return ResultOrAgain::kFailure;
     }

     return ResultOrAgain::kSuccess;
 }

 template <typename T>
 ResultOrAgain WriteInternal(const FuseMessage<T>* self, int fd, int sockflag, const void* data,
                             size_t max_size) {
     if (!CheckHeaderLength<T>(self, "Write", max_size)) {
         return ResultOrAgain::kFailure;
     }

     const char* const buf = reinterpret_cast<const char*>(self);
     const auto& header = static_cast<const T*>(self)->header;

     while (true) {
         int result;
         if (sockflag) {
             CHECK(data == nullptr);
             result = TEMP_FAILURE_RETRY(send(fd, buf, header.len, sockflag));
         } else if (data) {
             const struct iovec vec[] = {{const_cast<char*>(buf), sizeof(header)},
                                         {const_cast<void*>(data), header.len - sizeof(header)}};
             result = TEMP_FAILURE_RETRY(writev(fd, vec, arraysize(vec)));
         } else {
             result = TEMP_FAILURE_RETRY(write(fd, buf, header.len));
         }
         if (result == -1) {
             switch (errno) {
                 case ENOBUFS:
                     // When returning ENOBUFS, epoll still reports the FD is writable. Just usleep
                     // and retry again.
                     usleep(kRetrySleepForWriting);
                     continue;
                 case EAGAIN:
                     return ResultOrAgain::kAgain;
                 default:
                     PLOG(ERROR) << "Failed to write a FUSE message: "
                                 << "fd=" << fd << " "
                                 << "sockflag=" << sockflag << " "
                                 << "data=" << data;
                     return ResultOrAgain::kFailure;
             }
         }

         if (static_cast<unsigned int>(result) != header.len) {
             LOG(ERROR) << "Written bytes " << result << " is different from length in header "
                        << header.len;
             return ResultOrAgain::kFailure;
         }
         return ResultOrAgain::kSuccess;
     }
 }
 }

 static_assert(std::is_standard_layout<FuseBuffer>::value,
               "FuseBuffer must be standard layout union.");

 bool SetupMessageSockets(base::unique_fd (*result)[2]) {
     base::unique_fd fds[2];
     {
         int raw_fds[2];
         if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, raw_fds) == -1) {
             PLOG(ERROR) << "Failed to create sockets for proxy";
             return false;
         }
         fds[0].reset(raw_fds[0]);
         fds[1].reset(raw_fds[1]);
     }

     constexpr int kMaxMessageSize = sizeof(FuseBuffer);
     if (setsockopt(fds[0], SOL_SOCKET, SO_SNDBUF, &kMaxMessageSize, sizeof(int)) != 0 ||
         setsockopt(fds[1], SOL_SOCKET, SO_SNDBUF, &kMaxMessageSize, sizeof(int)) != 0) {
         PLOG(ERROR) << "Failed to update buffer size for socket";
         return false;
     }

     (*result)[0] = std::move(fds[0]);
     (*result)[1] = std::move(fds[1]);
     return true;
 }

 template <typename T>
 bool FuseMessage<T>::Read(int fd) {
     return ReadInternal(this, fd, 0) == ResultOrAgain::kSuccess;
 }

 template <typename T>
 ResultOrAgain FuseMessage<T>::ReadOrAgain(int fd) {
     return ReadInternal(this, fd, MSG_DONTWAIT);
 }

 template <typename T>
 bool FuseMessage<T>::Write(int fd) const {
     return WriteInternal(this, fd, 0, nullptr, sizeof(T)) == ResultOrAgain::kSuccess;
 }

 template <typename T>
 bool FuseMessage<T>::WriteWithBody(int fd, size_t max_size, const void* data) const {
     CHECK(data != nullptr);
     return WriteInternal(this, fd, 0, data, max_size) == ResultOrAgain::kSuccess;
 }

 template <typename T>
 ResultOrAgain FuseMessage<T>::WriteOrAgain(int fd) const {
     return WriteInternal(this, fd, MSG_DONTWAIT, nullptr, sizeof(T));
 }

 void FuseRequest::Reset(
     uint32_t data_length, uint32_t opcode, uint64_t unique) {
   memset(this, 0, sizeof(fuse_in_header) + data_length);
   header.len = sizeof(fuse_in_header) + data_length;
   header.opcode = opcode;
   header.unique = unique;
 }

 template <size_t N>
 void FuseResponseBase<N>::ResetHeader(uint32_t data_length, int32_t error, uint64_t unique) {
     CHECK_LE(error, 0) << "error should be zero or negative.";
     header.len = sizeof(fuse_out_header) + data_length;
     header.error = error;
     header.unique = unique;
 }

 template <size_t N>
 void FuseResponseBase<N>::Reset(uint32_t data_length, int32_t error, uint64_t unique) {
     memset(this, 0, sizeof(fuse_out_header) + data_length);
     ResetHeader(data_length, error, unique);
 }

 void FuseBuffer::HandleInit() {
   const fuse_init_in* const in = &request.init_in;

   // Before writing |out|, we need to copy data from |in|.
   const uint64_t unique = request.header.unique;
   const uint32_t minor = in->minor;
   const uint32_t max_readahead = in->max_readahead;

   // Kernel 2.6.16 is the first stable kernel with struct fuse_init_out
   // defined (fuse version 7.6). The structure is the same from 7.6 through
   // 7.22. Beginning with 7.23, the structure increased in size and added
   // new parameters.
   if (in->major != FUSE_KERNEL_VERSION || in->minor < 6) {
     LOG(ERROR) << "Fuse kernel version mismatch: Kernel version " << in->major
         << "." << in->minor << " Expected at least " << FUSE_KERNEL_VERSION
         << ".6";
     response.Reset(0, -EPERM, unique);
     return;
   }

   // We limit ourselves to minor=15 because we don't handle BATCH_FORGET yet.
   // Thus we need to use FUSE_COMPAT_22_INIT_OUT_SIZE.
 #if defined(FUSE_COMPAT_22_INIT_OUT_SIZE)
   // FUSE_KERNEL_VERSION >= 23.
   const size_t response_size = FUSE_COMPAT_22_INIT_OUT_SIZE;
 #else
   const size_t response_size = sizeof(fuse_init_out);
 #endif

   response.Reset(response_size, kFuseSuccess, unique);
   fuse_init_out* const out = &response.init_out;
   out->major = FUSE_KERNEL_VERSION;
   out->minor = std::min(minor, 15u);
   out->max_readahead = max_readahead;
   out->flags = FUSE_ATOMIC_O_TRUNC | FUSE_BIG_WRITES;
   out->max_background = 32;
   out->congestion_threshold = 32;
   out->max_write = kFuseMaxWrite;
 }

 void FuseBuffer::HandleNotImpl() {
   LOG(VERBOSE) << "NOTIMPL op=" << request.header.opcode << " uniq="
       << request.header.unique << " nid=" << request.header.nodeid;
   // Add volatile as a workaround for compiler issue which removes the temporary
   // variable.
   const volatile uint64_t unique = request.header.unique;
   response.Reset(0, -ENOSYS, unique);
 }

 template class FuseMessage<FuseRequest>;
 template class FuseMessage<FuseResponse>;
 template class FuseMessage<FuseSimpleResponse>;
 template struct FuseResponseBase<0u>;
 template struct FuseResponseBase<kFuseMaxRead>;

 }  // namespace fuse
 }  // namespace android
	/*
	* 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/FuseBuffer.h"

	#include <inttypes.h>
	#include <string.h>
	#include <unistd.h>

	#include <algorithm>
	#include <type_traits>

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

	#include <android-base/file.h>
	#include <android-base/logging.h>
	#include <android-base/macros.h>

	namespace android {
	namespace fuse {
	namespace {

	constexpr useconds_t kRetrySleepForWriting = 1000; // 1 ms

	template <typename T>
	bool CheckHeaderLength(const FuseMessage<T>* self, const char* name, size_t max_size) {
	const auto& header = static_cast<const T*>(self)->header;
	if (header.len >= sizeof(header) && header.len <= max_size) {
	return true;
	} else {
	LOG(ERROR) << "Invalid header length is found in " << name << ": " << header.len;
	return false;
	}
	}

	template <typename T>
	ResultOrAgain ReadInternal(FuseMessage<T>* self, int fd, int sockflag) {
	char* const buf = reinterpret_cast<char*>(self);
	const ssize_t result = sockflag ? TEMP_FAILURE_RETRY(recv(fd, buf, sizeof(T), sockflag))
	: TEMP_FAILURE_RETRY(read(fd, buf, sizeof(T)));

	switch (result) {
	case 0:
	// Expected EOF.
	return ResultOrAgain::kFailure;
	case -1:
	if (errno == EAGAIN) {
	return ResultOrAgain::kAgain;
	}
	PLOG(ERROR) << "Failed to read a FUSE message";
	return ResultOrAgain::kFailure;
	}

	const auto& header = static_cast<const T*>(self)->header;
	if (result < static_cast<ssize_t>(sizeof(header))) {
	LOG(ERROR) << "Read bytes " << result << " are shorter than header size " << sizeof(header);
	return ResultOrAgain::kFailure;
	}

	if (!CheckHeaderLength<T>(self, "Read", sizeof(T))) {
	return ResultOrAgain::kFailure;
	}

	if (static_cast<uint32_t>(result) != header.len) {
	LOG(ERROR) << "Read bytes " << result << " are different from header.len " << header.len;
	return ResultOrAgain::kFailure;
	}

	return ResultOrAgain::kSuccess;
	}

	template <typename T>
	ResultOrAgain WriteInternal(const FuseMessage<T>* self, int fd, int sockflag, const void* data,
	size_t max_size) {
	if (!CheckHeaderLength<T>(self, "Write", max_size)) {
	return ResultOrAgain::kFailure;
	}

	const char* const buf = reinterpret_cast<const char*>(self);
	const auto& header = static_cast<const T*>(self)->header;

	while (true) {
	int result;
	if (sockflag) {
	CHECK(data == nullptr);
	result = TEMP_FAILURE_RETRY(send(fd, buf, header.len, sockflag));
	} else if (data) {
	const struct iovec vec[] = {{const_cast<char*>(buf), sizeof(header)},
	{const_cast<void*>(data), header.len - sizeof(header)}};
	result = TEMP_FAILURE_RETRY(writev(fd, vec, arraysize(vec)));
	} else {
	result = TEMP_FAILURE_RETRY(write(fd, buf, header.len));
	}
	if (result == -1) {
	switch (errno) {
	case ENOBUFS:
	// When returning ENOBUFS, epoll still reports the FD is writable. Just usleep
	// and retry again.
	usleep(kRetrySleepForWriting);
	continue;
	case EAGAIN:
	return ResultOrAgain::kAgain;
	default:
	PLOG(ERROR) << "Failed to write a FUSE message: "
	<< "fd=" << fd << " "
	<< "sockflag=" << sockflag << " "
	<< "data=" << data;
	return ResultOrAgain::kFailure;
	}
	}

	if (static_cast<unsigned int>(result) != header.len) {
	LOG(ERROR) << "Written bytes " << result << " is different from length in header "
	<< header.len;
	return ResultOrAgain::kFailure;
	}
	return ResultOrAgain::kSuccess;
	}
	}
	}

	static_assert(std::is_standard_layout<FuseBuffer>::value,
	"FuseBuffer must be standard layout union.");

	bool SetupMessageSockets(base::unique_fd (*result)[2]) {
	base::unique_fd fds[2];
	{
	int raw_fds[2];
	if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, raw_fds) == -1) {
	PLOG(ERROR) << "Failed to create sockets for proxy";
	return false;
	}
	fds[0].reset(raw_fds[0]);
	fds[1].reset(raw_fds[1]);
	}

	constexpr int kMaxMessageSize = sizeof(FuseBuffer);
	if (setsockopt(fds[0], SOL_SOCKET, SO_SNDBUF, &kMaxMessageSize, sizeof(int)) != 0 \|\|
	setsockopt(fds[1], SOL_SOCKET, SO_SNDBUF, &kMaxMessageSize, sizeof(int)) != 0) {
	PLOG(ERROR) << "Failed to update buffer size for socket";
	return false;
	}

	(*result)[0] = std::move(fds[0]);
	(*result)[1] = std::move(fds[1]);
	return true;
	}

	template <typename T>
	bool FuseMessage<T>::Read(int fd) {
	return ReadInternal(this, fd, 0) == ResultOrAgain::kSuccess;
	}

	template <typename T>
	ResultOrAgain FuseMessage<T>::ReadOrAgain(int fd) {
	return ReadInternal(this, fd, MSG_DONTWAIT);
	}

	template <typename T>
	bool FuseMessage<T>::Write(int fd) const {
	return WriteInternal(this, fd, 0, nullptr, sizeof(T)) == ResultOrAgain::kSuccess;
	}

	template <typename T>
	bool FuseMessage<T>::WriteWithBody(int fd, size_t max_size, const void* data) const {
	CHECK(data != nullptr);
	return WriteInternal(this, fd, 0, data, max_size) == ResultOrAgain::kSuccess;
	}

	template <typename T>
	ResultOrAgain FuseMessage<T>::WriteOrAgain(int fd) const {
	return WriteInternal(this, fd, MSG_DONTWAIT, nullptr, sizeof(T));
	}

	void FuseRequest::Reset(
	uint32_t data_length, uint32_t opcode, uint64_t unique) {
	memset(this, 0, sizeof(fuse_in_header) + data_length);
	header.len = sizeof(fuse_in_header) + data_length;
	header.opcode = opcode;
	header.unique = unique;
	}

	template <size_t N>
	void FuseResponseBase<N>::ResetHeader(uint32_t data_length, int32_t error, uint64_t unique) {
	CHECK_LE(error, 0) << "error should be zero or negative.";
	header.len = sizeof(fuse_out_header) + data_length;
	header.error = error;
	header.unique = unique;
	}

	template <size_t N>
	void FuseResponseBase<N>::Reset(uint32_t data_length, int32_t error, uint64_t unique) {
	memset(this, 0, sizeof(fuse_out_header) + data_length);
	ResetHeader(data_length, error, unique);
	}

	void FuseBuffer::HandleInit() {
	const fuse_init_in* const in = &request.init_in;

	// Before writing \|out\|, we need to copy data from \|in\|.
	const uint64_t unique = request.header.unique;
	const uint32_t minor = in->minor;
	const uint32_t max_readahead = in->max_readahead;

	// Kernel 2.6.16 is the first stable kernel with struct fuse_init_out
	// defined (fuse version 7.6). The structure is the same from 7.6 through
	// 7.22. Beginning with 7.23, the structure increased in size and added
	// new parameters.
	if (in->major != FUSE_KERNEL_VERSION \|\| in->minor < 6) {
	LOG(ERROR) << "Fuse kernel version mismatch: Kernel version " << in->major
	<< "." << in->minor << " Expected at least " << FUSE_KERNEL_VERSION
	<< ".6";
	response.Reset(0, -EPERM, unique);
	return;
	}

	// We limit ourselves to minor=15 because we don't handle BATCH_FORGET yet.
	// Thus we need to use FUSE_COMPAT_22_INIT_OUT_SIZE.
	#if defined(FUSE_COMPAT_22_INIT_OUT_SIZE)
	// FUSE_KERNEL_VERSION >= 23.
	const size_t response_size = FUSE_COMPAT_22_INIT_OUT_SIZE;
	#else
	const size_t response_size = sizeof(fuse_init_out);
	#endif

	response.Reset(response_size, kFuseSuccess, unique);
	fuse_init_out* const out = &response.init_out;
	out->major = FUSE_KERNEL_VERSION;
	out->minor = std::min(minor, 15u);
	out->max_readahead = max_readahead;
	out->flags = FUSE_ATOMIC_O_TRUNC \| FUSE_BIG_WRITES;
	out->max_background = 32;
	out->congestion_threshold = 32;
	out->max_write = kFuseMaxWrite;
	}

	void FuseBuffer::HandleNotImpl() {
	LOG(VERBOSE) << "NOTIMPL op=" << request.header.opcode << " uniq="
	<< request.header.unique << " nid=" << request.header.nodeid;
	// Add volatile as a workaround for compiler issue which removes the temporary
	// variable.
	const volatile uint64_t unique = request.header.unique;
	response.Reset(0, -ENOSYS, unique);
	}

	template class FuseMessage<FuseRequest>;
	template class FuseMessage<FuseResponse>;
	template class FuseMessage<FuseSimpleResponse>;
	template struct FuseResponseBase<0u>;
	template struct FuseResponseBase<kFuseMaxRead>;

	} // namespace fuse
	} // namespace android