fuse: Implement IterDirents for directory file description

Fixes #3255.

This change adds support for IterDirents. You can now use `ls` in
the FUSE sandbox.

Co-authored-by: Craig Chi <craigchi@google.com>

3 files changed, 207 insertions, 1 deletions

diff --git a/test/fuse/BUILD b/test/fuse/BUILD
index 30d2a871f..a1b29aa33 100644
--- a/test/fuse/BUILD
+++ b/test/fuse/BUILD
@@ -43,7 +43,11 @@ syscall_test(
 )
 
 syscall_test(
+    fuse = "True",
     test = "//test/fuse/linux:rmdir_test",
-    vfs2 = "True",
+)
+
+syscall_test(
     fuse = "True",
+    test = "//test/fuse/linux:readdir_test",
 )
diff --git a/test/fuse/linux/BUILD b/test/fuse/linux/BUILD
index 159428fce..23c9fba31 100644
--- a/test/fuse/linux/BUILD
+++ b/test/fuse/linux/BUILD
@@ -112,6 +112,20 @@ cc_binary(
     ],
 )
 
+cc_binary(
+    name = "readdir_test",
+    testonly = 1,
+    srcs = ["readdir_test.cc"],
+    deps = [
+        gtest,
+        ":fuse_base",
+        "//test/util:fs_util",
+        "//test/util:fuse_util",
+        "//test/util:test_main",
+        "//test/util:test_util",
+    ],
+)
+
 cc_library(
     name = "fuse_base",
     testonly = 1,
diff --git a/test/fuse/linux/readdir_test.cc b/test/fuse/linux/readdir_test.cc
new file mode 100644
index 000000000..17fb630ee
--- /dev/null
+++ b/test/fuse/linux/readdir_test.cc
@@ -0,0 +1,188 @@
+// 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 <errno.h>
+#include <fcntl.h>
+#include <linux/fuse.h>
+#include <sys/stat.h>
+#include <sys/statfs.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <string>
+
+#include "gtest/gtest.h"
+#include "test/fuse/linux/fuse_base.h"
+#include "test/util/fuse_util.h"
+#include "test/util/test_util.h"
+
+#define FUSE_NAME_OFFSET offsetof(struct fuse_dirent, name)
+#define FUSE_DIRENT_ALIGN(x) \
+  (((x) + sizeof(uint64_t) - 1) & ~(sizeof(uint64_t) - 1))
+#define FUSE_DIRENT_SIZE(d) FUSE_DIRENT_ALIGN(FUSE_NAME_OFFSET + (d)->namelen)
+
+namespace gvisor {
+namespace testing {
+
+namespace {
+
+class ReaddirTest : public FuseTest {
+ public:
+  void fill_fuse_dirent(char *buf, const char *name) {
+    size_t namelen = strlen(name);
+    size_t entlen = FUSE_NAME_OFFSET + namelen;
+    size_t entlen_padded = FUSE_DIRENT_ALIGN(entlen);
+    struct fuse_dirent *dirent;
+
+    dirent = reinterpret_cast<struct fuse_dirent *>(buf);
+    dirent->namelen = namelen;
+    memcpy(dirent->name, name, namelen);
+    memset(dirent->name + namelen, 0, entlen_padded - entlen);
+  }
+
+ protected:
+  const std::string test_dir_name_ = "test_dir";
+};
+
+TEST_F(ReaddirTest, SingleEntry) {
+  const std::string test_dir_path =
+      JoinPath(mount_point_.path().c_str(), test_dir_name_);
+
+  // We need to make sure the test dir is a directory that can be found.
+  mode_t expected_mode =
+      S_IFDIR | S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH;
+  struct fuse_attr dir_attr = {
+      .ino = 1,
+      .size = 512,
+      .blocks = 4,
+      .mode = expected_mode,
+      .blksize = 4096,
+  };
+  struct fuse_out_header stat_header = {
+      .len = sizeof(struct fuse_out_header) + sizeof(struct fuse_attr_out),
+  };
+
+  struct fuse_attr_out stat_payload = {
+      .attr_valid_nsec = 2,
+      .attr = dir_attr,
+  };
+
+  // We need to make sure the test dir is a directory that can be found.
+  struct fuse_out_header lookup_header = {
+      .len = sizeof(struct fuse_out_header) + sizeof(struct fuse_entry_out),
+  };
+  struct fuse_entry_out lookup_payload = {
+      .nodeid = 1,
+      .entry_valid = true,
+      .attr_valid = true,
+      .attr = dir_attr,
+  };
+
+  struct fuse_out_header open_header = {
+      .len = sizeof(struct fuse_out_header) + sizeof(struct fuse_open_out),
+  };
+  struct fuse_open_out open_payload = {
+      .fh = 1,
+  };
+  auto iov_out = FuseGenerateIovecs(lookup_header, lookup_payload);
+  SetServerResponse(FUSE_LOOKUP, iov_out);
+
+  iov_out = FuseGenerateIovecs(open_header, open_payload);
+  SetServerResponse(FUSE_OPENDIR, iov_out);
+
+  iov_out = FuseGenerateIovecs(stat_header, stat_payload);
+  SetServerResponse(FUSE_GETATTR, iov_out);
+
+  DIR *dir = opendir(test_dir_path.c_str());
+
+  // The opendir command makes three syscalls. Lookup the dir file, stat it and
+  // open.
+  // We don't need to inspect those headers in this test.
+  SkipServerActualRequest();  // LOOKUP.
+  SkipServerActualRequest();  // GETATTR.
+  SkipServerActualRequest();  // OPENDIR.
+
+  // Readdir test code.
+  std::string dot = ".";
+  std::string dot_dot = "..";
+  std::string test_file = "testFile";
+
+  // Figure out how many dirents to send over and allocate them appropriately.
+  // Each dirent has a dynamic name and a static metadata part. The dirent size
+  // is aligned to being a multiple of 8.
+  size_t dot_file_dirent_size =
+      FUSE_DIRENT_ALIGN(dot.length() + FUSE_NAME_OFFSET);
+  size_t dot_dot_file_dirent_size =
+      FUSE_DIRENT_ALIGN(dot_dot.length() + FUSE_NAME_OFFSET);
+  size_t test_file_dirent_size =
+      FUSE_DIRENT_ALIGN(test_file.length() + FUSE_NAME_OFFSET);
+
+  // Create an appropriately sized payload.
+  size_t readdir_payload_size =
+      test_file_dirent_size + dot_file_dirent_size + dot_dot_file_dirent_size;
+  char readdir_payload[readdir_payload_size];
+
+  fill_fuse_dirent(readdir_payload, dot.c_str());
+  fill_fuse_dirent(readdir_payload + dot_file_dirent_size, dot_dot.c_str());
+  fill_fuse_dirent(
+      readdir_payload + dot_file_dirent_size + dot_dot_file_dirent_size,
+      test_file.c_str());
+
+  std::vector<char> readdir_payload_vec(readdir_payload,
+                                        readdir_payload + readdir_payload_size);
+  struct fuse_out_header readdir_header = {
+      .len = uint32_t(sizeof(struct fuse_out_header) + sizeof(readdir_payload)),
+  };
+  struct fuse_out_header readdir_header_break = {
+      .len = uint32_t(sizeof(struct fuse_out_header)),
+  };
+
+  iov_out = FuseGenerateIovecs(readdir_header, readdir_payload_vec);
+  SetServerResponse(FUSE_READDIR, iov_out);
+
+  iov_out = FuseGenerateIovecs(readdir_header_break);
+  SetServerResponse(FUSE_READDIR, iov_out);
+
+  struct dirent *entry;
+  entry = readdir(dir);
+  EXPECT_EQ(std::string(entry->d_name), dot);
+
+  entry = readdir(dir);
+  EXPECT_EQ(std::string(entry->d_name), dot_dot);
+
+  entry = readdir(dir);
+  EXPECT_EQ(std::string(entry->d_name), test_file);
+
+  entry = readdir(dir);
+  EXPECT_TRUE((entry == NULL));
+
+  SkipServerActualRequest();  // READDIR.
+  SkipServerActualRequest();  // READDIR with no data.
+
+  // Clean up.
+  closedir(dir);
+
+  struct fuse_in_header in_header;
+  struct fuse_release_in in_payload;
+
+  auto iov_in = FuseGenerateIovecs(in_header, in_payload);
+  GetServerActualRequest(iov_in);
+  EXPECT_EQ(in_header.len, sizeof(in_header) + sizeof(in_payload));
+  EXPECT_EQ(in_header.opcode, FUSE_RELEASEDIR);
+}
+
+}  // namespace
+
+}  // namespace testing
+}  // namespace gvisor
\ No newline at end of file