Add FUSE integration test

This commit adds an integration test framework for FUSE support. Please
refer to the test example and test/fuse/README.md for further details.

Fixes #3098

3 files changed, 322 insertions, 0 deletions

diff --git a/test/fuse/linux/BUILD b/test/fuse/linux/BUILD
new file mode 100644
index 000000000..cc3383741
--- /dev/null
+++ b/test/fuse/linux/BUILD
@@ -0,0 +1,21 @@
+load("//tools:defs.bzl", "cc_library", "gtest")
+
+package(
+    default_visibility = ["//:sandbox"],
+    licenses = ["notice"],
+)
+
+cc_library(
+    name = "fuse_base",
+    testonly = 1,
+    srcs = [
+        "fuse_base.h",
+        "fuse_base.cc",
+    ],
+    deps = [
+        gtest,
+        "//test/util:posix_error",
+        "//test/util:test_util",
+        "@com_google_absl//absl/strings:str_format",
+    ],
+)
diff --git a/test/fuse/linux/fuse_base.cc b/test/fuse/linux/fuse_base.cc
new file mode 100644
index 000000000..87092b515
--- /dev/null
+++ b/test/fuse/linux/fuse_base.cc
@@ -0,0 +1,204 @@
+// Copyright 2020 The gVisor Authors.
+//
+// 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 specific language governing permissions and
+// limitations under the License.
+
+#include "fuse_base.h"
+
+#include <fcntl.h>
+#include <linux/fuse.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/uio.h>
+#include <unistd.h>
+
+#include <iostream>
+
+#include "absl/strings/str_format.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "test/util/posix_error.h"
+#include "test/util/test_util.h"
+
+namespace gvisor {
+namespace testing {
+
+void FuseTest::SetUp() {
+  MountFuse();
+  SetUpFuseServer();
+}
+
+void FuseTest::TearDown() { UnmountFuse(); }
+
+// Since CompareRequest is running in background thread, gTest assertions and
+// expectations won't directly reflect the test result. However, the FUSE
+// background server still connects to the same standard I/O as testing main
+// thread. So EXPECT_XX can still be used to show different results. To
+// ensure failed testing result is observable, return false and the result
+// will be sent to test main thread via pipe.
+bool FuseTest::CompareRequest(void* expected_mem, size_t expected_len,
+                              void* real_mem, size_t real_len) {
+  if (expected_len != real_len) return false;
+  return memcmp(expected_mem, real_mem, expected_len) == 0;
+}
+
+// SetExpected is called by the testing main thread to set expected request-
+// response pair of a single FUSE operation.
+void FuseTest::SetExpected(struct iovec* iov_in, int iov_in_cnt,
+                           struct iovec* iov_out, int iov_out_cnt) {
+  EXPECT_THAT(RetryEINTR(writev)(set_expected_[1], iov_in, iov_in_cnt),
+              SyscallSucceedsWithValue(::testing::Gt(0)));
+  WaitCompleted();
+
+  EXPECT_THAT(RetryEINTR(writev)(set_expected_[1], iov_out, iov_out_cnt),
+              SyscallSucceedsWithValue(::testing::Gt(0)));
+  WaitCompleted();
+}
+
+// WaitCompleted waits for the FUSE server to finish its job and check if it
+// completes without errors.
+void FuseTest::WaitCompleted() {
+  char success;
+  EXPECT_THAT(RetryEINTR(read)(done_[0], &success, sizeof(success)),
+              SyscallSucceedsWithValue(1));
+}
+
+void FuseTest::MountFuse() {
+  EXPECT_THAT(dev_fd_ = open("/dev/fuse", O_RDWR), SyscallSucceeds());
+
+  std::string mount_opts = absl::StrFormat("fd=%d,%s", dev_fd_, kMountOpts);
+  EXPECT_THAT(mount("fuse", kMountPoint, "fuse", MS_NODEV | MS_NOSUID,
+                    mount_opts.c_str()),
+              SyscallSucceedsWithValue(0));
+}
+
+void FuseTest::UnmountFuse() {
+  EXPECT_THAT(umount(kMountPoint), SyscallSucceeds());
+  // TODO(gvisor.dev/issue/3330): ensure the process is terminated successfully.
+}
+
+// ConsumeFuseInit consumes the first FUSE request and returns the
+// corresponding PosixError.
+PosixError FuseTest::ConsumeFuseInit() {
+  RETURN_ERROR_IF_SYSCALL_FAIL(
+      RetryEINTR(read)(dev_fd_, buf_.data(), buf_.size()));
+
+  struct iovec iov_out[2];
+  struct fuse_out_header out_header = {
+      .len = sizeof(struct fuse_out_header) + sizeof(struct fuse_init_out),
+      .error = 0,
+      .unique = 2,
+  };
+  // Returns an empty init out payload since this is just a test.
+  struct fuse_init_out out_payload;
+  iov_out[0].iov_len = sizeof(out_header);
+  iov_out[0].iov_base = &out_header;
+  iov_out[1].iov_len = sizeof(out_payload);
+  iov_out[1].iov_base = &out_payload;
+
+  RETURN_ERROR_IF_SYSCALL_FAIL(RetryEINTR(writev)(dev_fd_, iov_out, 2));
+  return NoError();
+}
+
+// ReceiveExpected reads 1 pair of expected fuse request-response `iovec`s
+// from pipe and save them into member variables of this testing instance.
+void FuseTest::ReceiveExpected() {
+  // Set expected fuse_in request.
+  EXPECT_THAT(len_in_ = RetryEINTR(read)(set_expected_[0], mem_in_.data(),
+                                         mem_in_.size()),
+              SyscallSucceedsWithValue(::testing::Gt(0)));
+  MarkDone(len_in_ > 0);
+
+  // Set expected fuse_out response.
+  EXPECT_THAT(len_out_ = RetryEINTR(read)(set_expected_[0], mem_out_.data(),
+                                          mem_out_.size()),
+              SyscallSucceedsWithValue(::testing::Gt(0)));
+  MarkDone(len_out_ > 0);
+}
+
+// MarkDone writes 1 byte of success indicator through pipe.
+void FuseTest::MarkDone(bool success) {
+  char data = success ? 1 : 0;
+  EXPECT_THAT(RetryEINTR(write)(done_[1], &data, sizeof(data)),
+              SyscallSucceedsWithValue(1));
+}
+
+// FuseLoop is the implementation of the fake FUSE server. Read from /dev/fuse,
+// compare the request by CompareRequest (use derived function if specified),
+// and write the expected response to /dev/fuse.
+void FuseTest::FuseLoop() {
+  bool success = true;
+  ssize_t len = 0;
+  while (true) {
+    ReceiveExpected();
+
+    EXPECT_THAT(len = RetryEINTR(read)(dev_fd_, buf_.data(), buf_.size()),
+                SyscallSucceedsWithValue(len_in_));
+    if (len != len_in_) success = false;
+
+    if (!CompareRequest(buf_.data(), len_in_, mem_in_.data(), len_in_)) {
+      std::cerr << "the FUSE request is not expected" << std::endl;
+      success = false;
+    }
+
+    EXPECT_THAT(len = RetryEINTR(write)(dev_fd_, mem_out_.data(), len_out_),
+                SyscallSucceedsWithValue(len_out_));
+    if (len != len_out_) success = false;
+    MarkDone(success);
+  }
+}
+
+// SetUpFuseServer creates 2 pipes. First is for testing client to send the
+// expected request-response pair, and the other acts as a checkpoint for the
+// FUSE server to notify the client that it can proceed.
+void FuseTest::SetUpFuseServer() {
+  ASSERT_THAT(pipe(set_expected_), SyscallSucceedsWithValue(0));
+  ASSERT_THAT(pipe(done_), SyscallSucceedsWithValue(0));
+
+  switch (fork()) {
+    case -1:
+      GTEST_FAIL();
+      return;
+    case 0:
+      break;
+    default:
+      ASSERT_THAT(close(set_expected_[0]), SyscallSucceedsWithValue(0));
+      ASSERT_THAT(close(done_[1]), SyscallSucceedsWithValue(0));
+      WaitCompleted();
+      return;
+  }
+
+  ASSERT_THAT(close(set_expected_[1]), SyscallSucceedsWithValue(0));
+  ASSERT_THAT(close(done_[0]), SyscallSucceedsWithValue(0));
+
+  MarkDone(ConsumeFuseInit().ok());
+
+  FuseLoop();
+  _exit(0);
+}
+
+// GetPayloadSize is a helper function to get the number of bytes of a
+// specific FUSE operation struct.
+size_t FuseTest::GetPayloadSize(uint32_t opcode, bool in) {
+  switch (opcode) {
+    case FUSE_INIT:
+      return in ? sizeof(struct fuse_init_in) : sizeof(struct fuse_init_out);
+    default:
+      break;
+  }
+  return 0;
+}
+
+}  // namespace testing
+}  // namespace gvisor
diff --git a/test/fuse/linux/fuse_base.h b/test/fuse/linux/fuse_base.h
new file mode 100644
index 000000000..b008778de
--- /dev/null
+++ b/test/fuse/linux/fuse_base.h
@@ -0,0 +1,97 @@
+// Copyright 2020 The gVisor Authors.
+//
+// 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 specific language governing permissions and
+// limitations under the License.
+
+#ifndef GVISOR_TEST_FUSE_FUSE_BASE_H_
+#define GVISOR_TEST_FUSE_FUSE_BASE_H_
+
+#include <linux/fuse.h>
+#include <sys/uio.h>
+
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "test/util/posix_error.h"
+
+namespace gvisor {
+namespace testing {
+
+constexpr char kMountPoint[] = "/mnt";
+constexpr char kMountOpts[] = "rootmode=755,user_id=0,group_id=0";
+
+class FuseTest : public ::testing::Test {
+ public:
+  FuseTest() {
+    buf_.resize(FUSE_MIN_READ_BUFFER);
+    mem_in_.resize(FUSE_MIN_READ_BUFFER);
+    mem_out_.resize(FUSE_MIN_READ_BUFFER);
+  }
+  void SetUp() override;
+  void TearDown() override;
+
+  // CompareRequest is used by the FUSE server and should be implemented to
+  // compare different FUSE operations. It compares the actual FUSE input
+  // request with the expected one set by `SetExpected()`.
+  virtual bool CompareRequest(void* expected_mem, size_t expected_len,
+                              void* real_mem, size_t real_len);
+
+  // SetExpected is called by the testing main thread. Writes a request-
+  // response pair into FUSE server's member variables via pipe.
+  void SetExpected(struct iovec* iov_in, int iov_in_cnt, struct iovec* iov_out,
+                   int iov_out_cnt);
+
+  // WaitCompleted waits for FUSE server to complete its processing. It
+  // complains if the FUSE server responds failure during tests.
+  void WaitCompleted();
+
+ private:
+  void MountFuse();
+  void UnmountFuse();
+
+  // ConsumeFuseInit is only used during FUSE server setup.
+  PosixError ConsumeFuseInit();
+
+  // ReceiveExpected is the FUSE server side's corresponding code of
+  // `SetExpected()`. Save the request-response pair into its memory.
+  void ReceiveExpected();
+
+  // MarkDone is used by the FUSE server to tell testing main if it's OK to
+  // proceed next command.
+  void MarkDone(bool success);
+
+  // FuseLoop is where the FUSE server stay until it is terminated.
+  void FuseLoop();
+
+  // SetUpFuseServer creates 2 pipes for communication and forks FUSE server.
+  void SetUpFuseServer();
+
+  // GetPayloadSize is a helper function to get the number of bytes of a
+  // specific FUSE operation struct.
+  size_t GetPayloadSize(uint32_t opcode, bool in);
+
+  int dev_fd_;
+  int set_expected_[2];
+  int done_[2];
+
+  std::vector<char> buf_;
+  std::vector<char> mem_in_;
+  std::vector<char> mem_out_;
+  ssize_t len_in_;
+  ssize_t len_out_;
+};
+
+}  // namespace testing
+}  // namespace gvisor
+
+#endif  // GVISOR_TEST_FUSE_FUSE_BASE_H_