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ComixHeComixHe
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feat: Add function for sending fd
Signed-off-by: ComixHe <ComixHe1895@outlook.com>
1 parent 7146400 commit c7c2e98

5 files changed

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‎libs/common/CMakeLists.txt‎

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@@ -14,6 +14,8 @@ pfl_add_library(
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src/linglong/common/dir.h
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src/linglong/common/display.cpp
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src/linglong/common/display.h
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src/linglong/common/socket.cpp
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src/linglong/common/socket.h
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src/linglong/common/strings.cpp
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src/linglong/common/strings.h
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src/linglong/common/xdg.cpp

‎libs/common/src/linglong/common/socket.cpp‎

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// SPDX-FileCopyrightText: 2026 UnionTech Software Technology Co., Ltd.
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//
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// SPDX-License-Identifier: LGPL-3.0-or-later
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#include "linglong/common/socket.h"
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#include <cstring>
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#include <sys/socket.h>
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#include <unistd.h>
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namespace linglong::common::socket {
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tl::expected<SocketData, std::string> recvFdWithPayload(int fd, std::size_t bufSize)
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{
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if (fd < 0) {
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return tl::make_unexpected("Invalid file descriptor");
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}
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struct msghdr msg{};
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std::string payload_buffer(bufSize, '\0');
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struct iovec iov{};
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iov.iov_base = payload_buffer.data();
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iov.iov_len = payload_buffer.size();
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msg.msg_iov = &iov;
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msg.msg_iovlen = 1;
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std::array<std::byte, CMSG_SPACE(sizeof(int))> control_buf{};
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msg.msg_control = control_buf.data();
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msg.msg_controllen = control_buf.size();
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auto n = [&]() -> ssize_t {
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while (true) {
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auto ret = recvmsg(fd, &msg, 0);
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if (ret < 0) {
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if (errno == EINTR) {
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continue;
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}
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return -1;
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}
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return ret;
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}
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}();
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if (n < 0) {
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return tl::make_unexpected(std::string{ "Failed to receive message" } + ::strerror(errno));
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}
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int received_fd{ -1 };
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struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
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if (cmsg == nullptr) {
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return tl::make_unexpected("Failed to receive data");
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}
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if (cmsg->cmsg_level != SOL_SOCKET || cmsg->cmsg_type != SCM_RIGHTS) {
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return tl::make_unexpected("Not ancillary data with file descriptor");
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}
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std::memcpy(&received_fd, CMSG_DATA(cmsg), sizeof(int));
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return SocketData{ received_fd, std::string(payload_buffer.data(), n) };
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}
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tl::expected<void, std::string> sendFdWithPayload(int socketFd, int fd, const std::string &payload)
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{
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struct msghdr msg{};
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struct iovec iov{};
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iov.iov_base = const_cast<char *>(payload.data());
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iov.iov_len = payload.size();
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msg.msg_iov = &iov;
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msg.msg_iovlen = 1;
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alignas(struct cmsghdr) std::array<std::byte, CMSG_SPACE(sizeof(int))> control_buf{};
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msg.msg_control = control_buf.data();
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msg.msg_controllen = control_buf.size();
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struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
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cmsg->cmsg_level = SOL_SOCKET;
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cmsg->cmsg_type = SCM_RIGHTS;
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cmsg->cmsg_len = CMSG_LEN(sizeof(int));
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std::memcpy(CMSG_DATA(cmsg), &fd, sizeof(int));
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auto n = [&]() -> ssize_t {
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while (true) {
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auto ret = sendmsg(socketFd, &msg, 0);
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if (ret < 0) {
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if (errno == EINTR) {
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continue;
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}
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return -1;
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}
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return ret;
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}
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}();
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if (n < 0) {
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return tl::make_unexpected("sendmsg failed: " + std::string(strerror(errno)));
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}
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if (static_cast<size_t>(n) < payload.size()) {
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return tl::make_unexpected("Partial write: payload not fully sent");
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}
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return {};
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}
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} // namespace linglong::common::socket

‎libs/common/src/linglong/common/socket.h‎

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// SPDX-FileCopyrightText: 2026 UnionTech Software Technology Co., Ltd.
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//
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// SPDX-License-Identifier: LGPL-3.0-or-later
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#pragma once
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#include <tl/expected.hpp>
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#include <string>
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namespace linglong::common::socket {
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struct SocketData
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{
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int fd;
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std::string payload;
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};
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tl::expected<SocketData, std::string> recvFdWithPayload(int fd, std::size_t bufSize = 4096);
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tl::expected<void, std::string> sendFdWithPayload(int socketFd, int fd, const std::string &payload);
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} // namespace linglong::common::socket

‎libs/linglong/tests/ll-tests/CMakeLists.txt‎

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@@ -17,6 +17,7 @@ pfl_add_executable(
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src/linglong/builder/source_fetcher_test.cpp
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src/linglong/cli/cli_test.cpp
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src/linglong/common/strings_test.cpp
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src/linglong/common/socket_test.cpp
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src/linglong/common/xdg_test.cpp
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src/linglong/mocks/layer_packager_mock.h
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src/linglong/mocks/linglong_builder_mock.h
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src/linglong/utils/xdg/directory_test.cpp
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src/main.cpp
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# ll-driver-detect tests
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${PROJECT_SOURCE_DIR}/apps/ll-driver-detect/src/nvidia_driver_detector.cpp
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${PROJECT_SOURCE_DIR}/apps/ll-driver-detect/src/driver_detection_config.cpp

‎libs/linglong/tests/ll-tests/src/linglong/common/socket_test.cpp‎

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// SPDX-FileCopyrightText: 2026 UnionTech Software Technology Co., Ltd.
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//
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// SPDX-License-Identifier: LGPL-3.0-or-later
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#include <gtest/gtest.h>
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#include "linglong/common/socket.h"
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#include <sys/socket.h>
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class SocketFdTest : public ::testing::Test
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{
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protected:
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std::array<int, 2> sv;
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void SetUp() override { ASSERT_EQ(socketpair(AF_UNIX, SOCK_SEQPACKET, 0, sv.data()), 0); }
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void TearDown() override
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{
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close(sv[0]);
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close(sv[1]);
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}
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};
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using namespace linglong::common::socket;
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TEST_F(SocketFdTest, NormalCrossProcessTransfer)
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{
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const std::string payload = R"({"action": "test-fd-transfer"})";
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const std::string secret = "linglong-security-content";
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auto pid = fork();
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ASSERT_NE(pid, -1);
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if (pid == 0) {
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close(sv[1]);
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std::array<int, 2> pipefds{};
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ASSERT_EQ(pipe(pipefds.data()), 0);
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ASSERT_NE(write(pipefds[1], secret.data(), secret.size()), -1);
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auto res = sendFdWithPayload(sv[0], pipefds[0], payload);
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close(pipefds[0]);
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close(pipefds[1]);
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close(sv[0]);
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_exit(res.has_value() ? EXIT_SUCCESS : EXIT_FAILURE);
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}
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close(sv[0]);
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auto res = recvFdWithPayload(sv[1], payload.size());
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int status{ 0 };
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waitpid(pid, &status, 0);
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EXPECT_EQ(WEXITSTATUS(status), 0);
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ASSERT_TRUE(res.has_value()) << res.error();
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EXPECT_EQ(res->payload, payload);
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ASSERT_GT(res->fd, 0);
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std::string buf(secret.size(), '\0');
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const ssize_t n = read(res->fd, buf.data(), buf.size());
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ASSERT_NE(n, -1);
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EXPECT_EQ(std::string(buf.data(), n), secret);
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close(res->fd);
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}
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TEST_F(SocketFdTest, InvalidFileDescriptor)
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{
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auto res = recvFdWithPayload(-1, 1024);
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EXPECT_FALSE(res.has_value());
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EXPECT_EQ(res.error(), "Invalid file descriptor");
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}
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TEST_F(SocketFdTest, EmptyAncillaryData)
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{
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if (fork() == 0) {
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close(sv[1]);
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std::string data = "just-text-no-fd";
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ASSERT_NE(write(sv[0], data.data(), data.size()), -1);
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close(sv[0]);
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_exit(0);
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}
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close(sv[0]);
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auto res = recvFdWithPayload(sv[1], 1024);
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EXPECT_FALSE(res.has_value());
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wait(nullptr);
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}
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TEST_F(SocketFdTest, PayloadBufferTruncation)
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{
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const std::string long_payload(200, 'Z');
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if (fork() == 0) {
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close(sv[1]);
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auto ret = sendFdWithPayload(sv[0], STDOUT_FILENO, long_payload);
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EXPECT_TRUE(ret) << ret.error();
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close(sv[0]);
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_exit(0);
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}
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close(sv[0]);
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auto res = recvFdWithPayload(sv[1], 50);
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ASSERT_TRUE(res.has_value());
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EXPECT_EQ(res->payload.size(), 50);
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EXPECT_EQ(res->payload, long_payload.substr(0, 50));
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if (res->fd >= 0) {
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close(res->fd);
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}
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wait(nullptr);
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}
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TEST_F(SocketFdTest, SignalInterruptionRecovery)
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{
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auto handler = signal(SIGUSR1, [](int) { });
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ASSERT_NE(handler, SIG_ERR);
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if (fork() == 0) {
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close(sv[1]);
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usleep(50000);
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kill(getppid(), SIGUSR1);
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usleep(50000);
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auto ret = sendFdWithPayload(sv[0], STDERR_FILENO, "recovered");
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EXPECT_TRUE(ret) << ret.error();
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close(sv[0]);
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_exit(0);
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}
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close(sv[0]);
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auto res = recvFdWithPayload(sv[1], 1024);
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ASSERT_TRUE(res.has_value());
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EXPECT_EQ(res->payload, "recovered");
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if (res->fd >= 0) {
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close(res->fd);
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}
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wait(nullptr);
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ASSERT_NE(signal(SIGUSR1, handler), SIG_ERR);
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}
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TEST_F(SocketFdTest, PeerClosedBeforeSending)
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{
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if (fork() == 0) {
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close(sv[1]);
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close(sv[0]);
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_exit(0);
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}
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close(sv[0]);
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auto res = recvFdWithPayload(sv[1], 1024);
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EXPECT_FALSE(res.has_value());
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wait(nullptr);
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}
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TEST_F(SocketFdTest, SendInvalidFdHandle)
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{
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auto res = sendFdWithPayload(sv[0], 9999, "bad-fd");
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EXPECT_FALSE(res.has_value());
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}
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TEST_F(SocketFdTest, LargePayloadHandling)
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{
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const std::string large_payload(65536, 'B');
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if (fork() == 0) {
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close(sv[1]);
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auto ret = sendFdWithPayload(sv[0], STDIN_FILENO, large_payload);
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close(sv[0]);
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_exit(0);
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}
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close(sv[0]);
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auto res = recvFdWithPayload(sv[1], 70000);
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ASSERT_TRUE(res.has_value());
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EXPECT_EQ(res->payload, large_payload);
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if (res->fd >= 0) {
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close(res->fd);
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}
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wait(nullptr);
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}

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