Add basic plumbing for splice and stub implementation.

This does not actually implement an efficient splice or sendfile. Rather, it
adds a generic plumbing to the file internals so that this can be added. All
file implementations use the stub fileutil.NoSplice implementation, which
causes sendfile and splice to fall back to an internal copy.

A basic splice system call interface is added, along with a test.

PiperOrigin-RevId: 249335960
Change-Id: Ic5568be2af0a505c19e7aec66d5af2480ab0939b

1 files changed, 404 insertions, 0 deletions

diff --git a/test/syscalls/linux/splice.cc b/test/syscalls/linux/splice.cc
new file mode 100644
index 000000000..1875f4533
--- /dev/null
+++ b/test/syscalls/linux/splice.cc
@@ -0,0 +1,404 @@
+// Copyright 2019 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 <fcntl.h>
+#include <sys/sendfile.h>
+#include <unistd.h>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/strings/string_view.h"
+#include "test/util/file_descriptor.h"
+#include "test/util/temp_path.h"
+#include "test/util/test_util.h"
+#include "test/util/thread_util.h"
+
+namespace gvisor {
+namespace testing {
+
+namespace {
+
+TEST(SpliceTest, TwoRegularFiles) {
+  // Create temp files.
+  const TempPath in_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  const TempPath out_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+
+  // Open the input file as read only.
+  const FileDescriptor inf =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(in_file.path(), O_RDONLY));
+
+  // Open the output file as write only.
+  const FileDescriptor outf =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(out_file.path(), O_WRONLY));
+
+  // Verify that it is rejected as expected; regardless of offsets.
+  loff_t in_offset = 0;
+  loff_t out_offset = 0;
+  EXPECT_THAT(splice(inf.get(), &in_offset, outf.get(), &out_offset, 1, 0),
+              SyscallFailsWithErrno(EINVAL));
+  EXPECT_THAT(splice(inf.get(), nullptr, outf.get(), &out_offset, 1, 0),
+              SyscallFailsWithErrno(EINVAL));
+  EXPECT_THAT(splice(inf.get(), &in_offset, outf.get(), nullptr, 1, 0),
+              SyscallFailsWithErrno(EINVAL));
+  EXPECT_THAT(splice(inf.get(), nullptr, outf.get(), nullptr, 1, 0),
+              SyscallFailsWithErrno(EINVAL));
+}
+
+TEST(SpliceTest, SamePipe) {
+  // Create a new pipe.
+  int fds[2];
+  ASSERT_THAT(pipe(fds), SyscallSucceeds());
+  const FileDescriptor rfd(fds[0]);
+  const FileDescriptor wfd(fds[1]);
+
+  // Fill the pipe.
+  std::vector<char> buf(kPageSize);
+  RandomizeBuffer(buf.data(), buf.size());
+  ASSERT_THAT(write(wfd.get(), buf.data(), buf.size()),
+              SyscallSucceedsWithValue(kPageSize));
+
+  // Attempt to splice to itself.
+  EXPECT_THAT(splice(rfd.get(), nullptr, wfd.get(), nullptr, kPageSize, 0),
+              SyscallFailsWithErrno(EINVAL));
+}
+
+TEST(TeeTest, SamePipe) {
+  SKIP_IF(IsRunningOnGvisor());
+
+  // Create a new pipe.
+  int fds[2];
+  ASSERT_THAT(pipe(fds), SyscallSucceeds());
+  const FileDescriptor rfd(fds[0]);
+  const FileDescriptor wfd(fds[1]);
+
+  // Fill the pipe.
+  std::vector<char> buf(kPageSize);
+  RandomizeBuffer(buf.data(), buf.size());
+  ASSERT_THAT(write(wfd.get(), buf.data(), buf.size()),
+              SyscallSucceedsWithValue(kPageSize));
+
+  // Attempt to tee to itself.
+  EXPECT_THAT(tee(rfd.get(), wfd.get(), kPageSize, 0),
+              SyscallFailsWithErrno(EINVAL));
+}
+
+TEST(TeeTest, RegularFile) {
+  SKIP_IF(IsRunningOnGvisor());
+
+  // Open some file.
+  const TempPath in_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  const FileDescriptor inf =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(in_file.path(), O_RDWR));
+
+  // Create a new pipe.
+  int fds[2];
+  ASSERT_THAT(pipe(fds), SyscallSucceeds());
+  const FileDescriptor rfd(fds[0]);
+  const FileDescriptor wfd(fds[1]);
+
+  // Attempt to tee from the file.
+  EXPECT_THAT(tee(inf.get(), wfd.get(), kPageSize, 0),
+              SyscallFailsWithErrno(EINVAL));
+  EXPECT_THAT(tee(rfd.get(), inf.get(), kPageSize, 0),
+              SyscallFailsWithErrno(EINVAL));
+}
+
+TEST(SpliceTest, PipeOffsets) {
+  // Create two new pipes.
+  int first[2], second[2];
+  ASSERT_THAT(pipe(first), SyscallSucceeds());
+  const FileDescriptor rfd1(first[0]);
+  const FileDescriptor wfd1(first[1]);
+  ASSERT_THAT(pipe(second), SyscallSucceeds());
+  const FileDescriptor rfd2(second[0]);
+  const FileDescriptor wfd2(second[1]);
+
+  // All pipe offsets should be rejected.
+  loff_t in_offset = 0;
+  loff_t out_offset = 0;
+  EXPECT_THAT(splice(rfd1.get(), &in_offset, wfd2.get(), &out_offset, 1, 0),
+              SyscallFailsWithErrno(ESPIPE));
+  EXPECT_THAT(splice(rfd1.get(), nullptr, wfd2.get(), &out_offset, 1, 0),
+              SyscallFailsWithErrno(ESPIPE));
+  EXPECT_THAT(splice(rfd1.get(), &in_offset, wfd2.get(), nullptr, 1, 0),
+              SyscallFailsWithErrno(ESPIPE));
+}
+
+TEST(SpliceTest, ToPipe) {
+  // Open the input file.
+  const TempPath in_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  const FileDescriptor inf =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(in_file.path(), O_RDWR));
+
+  // Fill with some random data.
+  std::vector<char> buf(kPageSize);
+  RandomizeBuffer(buf.data(), buf.size());
+  ASSERT_THAT(write(inf.get(), buf.data(), buf.size()),
+              SyscallSucceedsWithValue(kPageSize));
+  ASSERT_THAT(lseek(inf.get(), 0, SEEK_SET), SyscallSucceedsWithValue(0));
+
+  // Create a new pipe.
+  int fds[2];
+  ASSERT_THAT(pipe(fds), SyscallSucceeds());
+  const FileDescriptor rfd(fds[0]);
+  const FileDescriptor wfd(fds[1]);
+
+  // Splice to the pipe.
+  EXPECT_THAT(splice(inf.get(), nullptr, wfd.get(), nullptr, kPageSize, 0),
+              SyscallSucceedsWithValue(kPageSize));
+
+  // Contents should be equal.
+  std::vector<char> rbuf(kPageSize);
+  ASSERT_THAT(read(rfd.get(), rbuf.data(), rbuf.size()),
+              SyscallSucceedsWithValue(kPageSize));
+  EXPECT_EQ(memcmp(rbuf.data(), buf.data(), buf.size()), 0);
+}
+
+TEST(SpliceTest, ToPipeOffset) {
+  // Open the input file.
+  const TempPath in_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  const FileDescriptor inf =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(in_file.path(), O_RDWR));
+
+  // Fill with some random data.
+  std::vector<char> buf(kPageSize);
+  RandomizeBuffer(buf.data(), buf.size());
+  ASSERT_THAT(write(inf.get(), buf.data(), buf.size()),
+              SyscallSucceedsWithValue(kPageSize));
+
+  // Create a new pipe.
+  int fds[2];
+  ASSERT_THAT(pipe(fds), SyscallSucceeds());
+  const FileDescriptor rfd(fds[0]);
+  const FileDescriptor wfd(fds[1]);
+
+  // Splice to the pipe.
+  loff_t in_offset = kPageSize / 2;
+  EXPECT_THAT(
+      splice(inf.get(), &in_offset, wfd.get(), nullptr, kPageSize / 2, 0),
+      SyscallSucceedsWithValue(kPageSize / 2));
+
+  // Contents should be equal to only the second part.
+  std::vector<char> rbuf(kPageSize / 2);
+  ASSERT_THAT(read(rfd.get(), rbuf.data(), rbuf.size()),
+              SyscallSucceedsWithValue(kPageSize / 2));
+  EXPECT_EQ(memcmp(rbuf.data(), buf.data() + (kPageSize / 2), rbuf.size()), 0);
+}
+
+TEST(SpliceTest, FromPipe) {
+  // Create a new pipe.
+  int fds[2];
+  ASSERT_THAT(pipe(fds), SyscallSucceeds());
+  const FileDescriptor rfd(fds[0]);
+  const FileDescriptor wfd(fds[1]);
+
+  // Fill with some random data.
+  std::vector<char> buf(kPageSize);
+  RandomizeBuffer(buf.data(), buf.size());
+  ASSERT_THAT(write(wfd.get(), buf.data(), buf.size()),
+              SyscallSucceedsWithValue(kPageSize));
+
+  // Open the input file.
+  const TempPath out_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  const FileDescriptor outf =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(out_file.path(), O_RDWR));
+
+  // Splice to the output file.
+  EXPECT_THAT(splice(rfd.get(), nullptr, outf.get(), nullptr, kPageSize, 0),
+              SyscallSucceedsWithValue(kPageSize));
+
+  // The offset of the output should be equal to kPageSize. We assert that and
+  // reset to zero so that we can read the contents and ensure they match.
+  EXPECT_THAT(lseek(outf.get(), 0, SEEK_CUR),
+              SyscallSucceedsWithValue(kPageSize));
+  ASSERT_THAT(lseek(outf.get(), 0, SEEK_SET), SyscallSucceedsWithValue(0));
+
+  // Contents should be equal.
+  std::vector<char> rbuf(kPageSize);
+  ASSERT_THAT(read(outf.get(), rbuf.data(), rbuf.size()),
+              SyscallSucceedsWithValue(kPageSize));
+  EXPECT_EQ(memcmp(rbuf.data(), buf.data(), buf.size()), 0);
+}
+
+TEST(SpliceTest, FromPipeOffset) {
+  // Create a new pipe.
+  int fds[2];
+  ASSERT_THAT(pipe(fds), SyscallSucceeds());
+  const FileDescriptor rfd(fds[0]);
+  const FileDescriptor wfd(fds[1]);
+
+  // Fill with some random data.
+  std::vector<char> buf(kPageSize);
+  RandomizeBuffer(buf.data(), buf.size());
+  ASSERT_THAT(write(wfd.get(), buf.data(), buf.size()),
+              SyscallSucceedsWithValue(kPageSize));
+
+  // Open the input file.
+  const TempPath out_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  const FileDescriptor outf =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(out_file.path(), O_RDWR));
+
+  // Splice to the output file.
+  loff_t out_offset = kPageSize / 2;
+  EXPECT_THAT(splice(rfd.get(), nullptr, outf.get(), &out_offset, kPageSize, 0),
+              SyscallSucceedsWithValue(kPageSize));
+
+  // Content should reflect the splice. We write to a specific offset in the
+  // file, so the internals should now be allocated sparsely.
+  std::vector<char> rbuf(kPageSize);
+  ASSERT_THAT(read(outf.get(), rbuf.data(), rbuf.size()),
+              SyscallSucceedsWithValue(kPageSize));
+  std::vector<char> zbuf(kPageSize / 2);
+  memset(zbuf.data(), 0, zbuf.size());
+  EXPECT_EQ(memcmp(rbuf.data(), zbuf.data(), zbuf.size()), 0);
+  EXPECT_EQ(memcmp(rbuf.data() + kPageSize / 2, buf.data(), kPageSize / 2), 0);
+}
+
+TEST(SpliceTest, TwoPipes) {
+  // Create two new pipes.
+  int first[2], second[2];
+  ASSERT_THAT(pipe(first), SyscallSucceeds());
+  const FileDescriptor rfd1(first[0]);
+  const FileDescriptor wfd1(first[1]);
+  ASSERT_THAT(pipe(second), SyscallSucceeds());
+  const FileDescriptor rfd2(second[0]);
+  const FileDescriptor wfd2(second[1]);
+
+  // Fill with some random data.
+  std::vector<char> buf(kPageSize);
+  RandomizeBuffer(buf.data(), buf.size());
+  ASSERT_THAT(write(wfd1.get(), buf.data(), buf.size()),
+              SyscallSucceedsWithValue(kPageSize));
+
+  // Splice to the second pipe, using two operations.
+  EXPECT_THAT(
+      splice(rfd1.get(), nullptr, wfd2.get(), nullptr, kPageSize / 2, 0),
+      SyscallSucceedsWithValue(kPageSize / 2));
+  EXPECT_THAT(
+      splice(rfd1.get(), nullptr, wfd2.get(), nullptr, kPageSize / 2, 0),
+      SyscallSucceedsWithValue(kPageSize / 2));
+
+  // Content should reflect the splice.
+  std::vector<char> rbuf(kPageSize);
+  ASSERT_THAT(read(rfd2.get(), rbuf.data(), rbuf.size()),
+              SyscallSucceedsWithValue(kPageSize));
+  EXPECT_EQ(memcmp(rbuf.data(), buf.data(), kPageSize), 0);
+}
+
+TEST(SpliceTest, Blocking) {
+  // Create two new pipes.
+  int first[2], second[2];
+  ASSERT_THAT(pipe(first), SyscallSucceeds());
+  const FileDescriptor rfd1(first[0]);
+  const FileDescriptor wfd1(first[1]);
+  ASSERT_THAT(pipe(second), SyscallSucceeds());
+  const FileDescriptor rfd2(second[0]);
+  const FileDescriptor wfd2(second[1]);
+
+  // This thread writes to the main pipe.
+  std::vector<char> buf(kPageSize);
+  RandomizeBuffer(buf.data(), buf.size());
+  ScopedThread t([&]() {
+    ASSERT_THAT(write(wfd1.get(), buf.data(), buf.size()),
+                SyscallSucceedsWithValue(kPageSize));
+  });
+
+  // Attempt a splice immediately; it should block.
+  EXPECT_THAT(splice(rfd1.get(), nullptr, wfd2.get(), nullptr, kPageSize, 0),
+              SyscallSucceedsWithValue(kPageSize));
+
+  // Thread should be joinable.
+  t.Join();
+
+  // Content should reflect the splice.
+  std::vector<char> rbuf(kPageSize);
+  ASSERT_THAT(read(rfd2.get(), rbuf.data(), rbuf.size()),
+              SyscallSucceedsWithValue(kPageSize));
+  EXPECT_EQ(memcmp(rbuf.data(), buf.data(), kPageSize), 0);
+}
+
+TEST(TeeTest, Blocking) {
+  SKIP_IF(IsRunningOnGvisor());
+
+  // Create two new pipes.
+  int first[2], second[2];
+  ASSERT_THAT(pipe(first), SyscallSucceeds());
+  const FileDescriptor rfd1(first[0]);
+  const FileDescriptor wfd1(first[1]);
+  ASSERT_THAT(pipe(second), SyscallSucceeds());
+  const FileDescriptor rfd2(second[0]);
+  const FileDescriptor wfd2(second[1]);
+
+  // This thread writes to the main pipe.
+  std::vector<char> buf(kPageSize);
+  RandomizeBuffer(buf.data(), buf.size());
+  ScopedThread t([&]() {
+    ASSERT_THAT(write(wfd1.get(), buf.data(), buf.size()),
+                SyscallSucceedsWithValue(kPageSize));
+  });
+
+  // Attempt a tee immediately; it should block.
+  EXPECT_THAT(tee(rfd1.get(), wfd2.get(), kPageSize, 0),
+              SyscallSucceedsWithValue(kPageSize));
+
+  // Thread should be joinable.
+  t.Join();
+
+  // Content should reflect the splice, in both pipes.
+  std::vector<char> rbuf(kPageSize);
+  ASSERT_THAT(read(rfd2.get(), rbuf.data(), rbuf.size()),
+              SyscallSucceedsWithValue(kPageSize));
+  EXPECT_EQ(memcmp(rbuf.data(), buf.data(), kPageSize), 0);
+  ASSERT_THAT(read(rfd1.get(), rbuf.data(), rbuf.size()),
+              SyscallSucceedsWithValue(kPageSize));
+  EXPECT_EQ(memcmp(rbuf.data(), buf.data(), kPageSize), 0);
+}
+
+TEST(SpliceTest, NonBlocking) {
+  // Create two new pipes.
+  int first[2], second[2];
+  ASSERT_THAT(pipe(first), SyscallSucceeds());
+  const FileDescriptor rfd1(first[0]);
+  const FileDescriptor wfd1(first[1]);
+  ASSERT_THAT(pipe(second), SyscallSucceeds());
+  const FileDescriptor rfd2(second[0]);
+  const FileDescriptor wfd2(second[1]);
+
+  // Splice with no data to back it.
+  EXPECT_THAT(splice(rfd1.get(), nullptr, wfd2.get(), nullptr, kPageSize,
+                     SPLICE_F_NONBLOCK),
+              SyscallFailsWithErrno(EAGAIN));
+}
+
+TEST(TeeTest, NonBlocking) {
+  SKIP_IF(IsRunningOnGvisor());
+
+  // Create two new pipes.
+  int first[2], second[2];
+  ASSERT_THAT(pipe(first), SyscallSucceeds());
+  const FileDescriptor rfd1(first[0]);
+  const FileDescriptor wfd1(first[1]);
+  ASSERT_THAT(pipe(second), SyscallSucceeds());
+  const FileDescriptor rfd2(second[0]);
+  const FileDescriptor wfd2(second[1]);
+
+  // Splice with no data to back it.
+  EXPECT_THAT(tee(rfd1.get(), wfd2.get(), kPageSize, SPLICE_F_NONBLOCK),
+              SyscallFailsWithErrno(EAGAIN));
+}
+
+}  // namespace
+
+}  // namespace testing
+}  // namespace gvisor