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// Copyright 2018 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/resource.h>
#include <sys/select.h>
#include <sys/time.h>
#include <climits>
#include <csignal>
#include <cstdio>
#include "gtest/gtest.h"
#include "absl/time/time.h"
#include "test/syscalls/linux/base_poll_test.h"
#include "test/util/file_descriptor.h"
#include "test/util/multiprocess_util.h"
#include "test/util/posix_error.h"
#include "test/util/rlimit_util.h"
#include "test/util/temp_path.h"
#include "test/util/test_util.h"
namespace gvisor {
namespace testing {
namespace {
class SelectTest : public BasePollTest {
protected:
void SetUp() override { BasePollTest::SetUp(); }
void TearDown() override { BasePollTest::TearDown(); }
};
// See that when there are no FD sets, select behaves like sleep.
TEST_F(SelectTest, NullFds) {
struct timeval timeout = absl::ToTimeval(absl::Milliseconds(10));
ASSERT_THAT(select(0, nullptr, nullptr, nullptr, &timeout),
SyscallSucceeds());
EXPECT_EQ(timeout.tv_sec, 0);
EXPECT_EQ(timeout.tv_usec, 0);
timeout = absl::ToTimeval(absl::Milliseconds(10));
ASSERT_THAT(select(1, nullptr, nullptr, nullptr, &timeout),
SyscallSucceeds());
EXPECT_EQ(timeout.tv_sec, 0);
EXPECT_EQ(timeout.tv_usec, 0);
}
TEST_F(SelectTest, NegativeNfds) {
EXPECT_THAT(select(-1, nullptr, nullptr, nullptr, nullptr),
SyscallFailsWithErrno(EINVAL));
EXPECT_THAT(select(-100000, nullptr, nullptr, nullptr, nullptr),
SyscallFailsWithErrno(EINVAL));
EXPECT_THAT(select(INT_MIN, nullptr, nullptr, nullptr, nullptr),
SyscallFailsWithErrno(EINVAL));
}
TEST_F(SelectTest, ClosedFds) {
auto temp_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
FileDescriptor fd =
ASSERT_NO_ERRNO_AND_VALUE(Open(temp_file.path(), O_RDONLY));
// We can't rely on a file descriptor being closed in a multi threaded
// application so fork to get a clean process.
EXPECT_THAT(InForkedProcess([&] {
int fd_num = fd.get();
fd.reset();
fd_set read_set;
FD_ZERO(&read_set);
FD_SET(fd_num, &read_set);
struct timeval timeout =
absl::ToTimeval(absl::Milliseconds(10));
TEST_PCHECK(select(fd_num + 1, &read_set, nullptr, nullptr,
&timeout) != 0);
TEST_PCHECK(errno == EBADF);
}),
IsPosixErrorOkAndHolds(0));
}
TEST_F(SelectTest, ZeroTimeout) {
struct timeval timeout = {};
EXPECT_THAT(select(1, nullptr, nullptr, nullptr, &timeout),
SyscallSucceeds());
// Ignore timeout as its value is now undefined.
}
// If random S/R interrupts the select, SIGALRM may be delivered before select
// restarts, causing the select to hang forever.
TEST_F(SelectTest, NoTimeout_NoRandomSave) {
// When there's no timeout, select may never return so set a timer.
SetTimer(absl::Milliseconds(100));
// See that we get interrupted by the timer.
ASSERT_THAT(select(1, nullptr, nullptr, nullptr, nullptr),
SyscallFailsWithErrno(EINTR));
EXPECT_TRUE(TimerFired());
}
TEST_F(SelectTest, InvalidTimeoutNegative) {
struct timeval timeout = absl::ToTimeval(absl::Microseconds(-1));
EXPECT_THAT(select(1, nullptr, nullptr, nullptr, &timeout),
SyscallFailsWithErrno(EINVAL));
// Ignore timeout as its value is now undefined.
}
// Verify that a signal interrupts select.
//
// If random S/R interrupts the select, SIGALRM may be delivered before select
// restarts, causing the select to hang forever.
TEST_F(SelectTest, InterruptedBySignal_NoRandomSave) {
absl::Duration duration(absl::Seconds(5));
struct timeval timeout = absl::ToTimeval(duration);
SetTimer(absl::Milliseconds(100));
ASSERT_FALSE(TimerFired());
ASSERT_THAT(select(1, nullptr, nullptr, nullptr, &timeout),
SyscallFailsWithErrno(EINTR));
EXPECT_TRUE(TimerFired());
// Ignore timeout as its value is now undefined.
}
TEST_F(SelectTest, IgnoreBitsAboveNfds) {
// fd_set is a bit array with at least FD_SETSIZE bits. Test that bits
// corresponding to file descriptors above nfds are ignored.
fd_set read_set;
FD_ZERO(&read_set);
constexpr int kNfds = 1;
for (int fd = kNfds; fd < FD_SETSIZE; fd++) {
FD_SET(fd, &read_set);
}
// Pass a zero timeout so that select returns immediately.
struct timeval timeout = {};
EXPECT_THAT(select(kNfds, &read_set, nullptr, nullptr, &timeout),
SyscallSucceedsWithValue(0));
}
// This test illustrates Linux's behavior of 'select' calls passing after
// setrlimit RLIMIT_NOFILE is called. In particular, versions of sshd rely on
// this behavior.
TEST_F(SelectTest, SetrlimitCallNOFILE) {
fd_set read_set;
FD_ZERO(&read_set);
timeval timeout = {};
const FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(
Open(NewTempAbsPath(), O_RDONLY | O_CREAT, S_IRUSR));
Cleanup reset_rlimit =
ASSERT_NO_ERRNO_AND_VALUE(ScopedSetSoftRlimit(RLIMIT_NOFILE, 0));
FD_SET(fd.get(), &read_set);
// this call with zero timeout should return immediately
EXPECT_THAT(select(fd.get() + 1, &read_set, nullptr, nullptr, &timeout),
SyscallSucceeds());
}
} // namespace
} // namespace testing
} // namespace gvisor
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