1//===-- llvm/Support/raw_socket_stream.cpp - Socket streams --*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file contains raw_ostream implementations for streams to communicate
10// via UNIX sockets
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/Support/raw_socket_stream.h"
15#include "llvm/Config/config.h"
16#include "llvm/Support/Error.h"
17#include "llvm/Support/FileSystem.h"
18
19#include <atomic>
20#include <fcntl.h>
21#include <functional>
22
23#ifndef _WIN32
24#include <poll.h>
25#include <sys/socket.h>
26#include <sys/un.h>
27#else
28#include "llvm/Support/Windows/WindowsSupport.h"
29// winsock2.h must be included before afunix.h. Briefly turn off clang-format to
30// avoid error.
31// clang-format off
32#include <winsock2.h>
33#include <afunix.h>
34// clang-format on
35#include <io.h>
36#endif // _WIN32
37
38#if defined(HAVE_UNISTD_H)
39#include <unistd.h>
40#endif
41
42using namespace llvm;
43
44#ifdef _WIN32
45WSABalancer::WSABalancer() {
46 WSADATA WsaData;
47 ::memset(&WsaData, 0, sizeof(WsaData));
48 if (WSAStartup(MAKEWORD(2, 2), &WsaData) != 0) {
49 llvm::report_fatal_error("WSAStartup failed");
50 }
51}
52
53WSABalancer::~WSABalancer() { WSACleanup(); }
54#endif // _WIN32
55
56static std::error_code getLastSocketErrorCode() {
57#ifdef _WIN32
58 return std::error_code(::WSAGetLastError(), std::system_category());
59#else
60 return errnoAsErrorCode();
61#endif
62}
63
64static sockaddr_un setSocketAddr(StringRef SocketPath) {
65 struct sockaddr_un Addr;
66 memset(s: &Addr, c: 0, n: sizeof(Addr));
67 Addr.sun_family = AF_UNIX;
68 strncpy(dest: Addr.sun_path, src: SocketPath.str().c_str(), n: sizeof(Addr.sun_path) - 1);
69 return Addr;
70}
71
72static Expected<int> getSocketFD(StringRef SocketPath) {
73#ifdef _WIN32
74 SOCKET Socket = socket(AF_UNIX, SOCK_STREAM, 0);
75 if (Socket == INVALID_SOCKET) {
76#else
77 int Socket = socket(AF_UNIX, SOCK_STREAM, protocol: 0);
78 if (Socket == -1) {
79#endif // _WIN32
80 return llvm::make_error<StringError>(Args: getLastSocketErrorCode(),
81 Args: "Create socket failed");
82 }
83
84#ifdef __CYGWIN__
85 // On Cygwin, UNIX sockets involve a handshake between connect and accept
86 // to enable SO_PEERCRED/getpeereid handling. This necessitates accept being
87 // called before connect can return, but at least the tests in
88 // llvm/unittests/Support/raw_socket_stream_test do both on the same thread
89 // (first connect and then accept), resulting in a deadlock. This call turns
90 // off the handshake (and SO_PEERCRED/getpeereid support).
91 setsockopt(Socket, SOL_SOCKET, SO_PEERCRED, NULL, 0);
92#endif
93 struct sockaddr_un Addr = setSocketAddr(SocketPath);
94 if (::connect(fd: Socket, addr: (struct sockaddr *)&Addr, len: sizeof(Addr)) == -1)
95 return llvm::make_error<StringError>(Args: getLastSocketErrorCode(),
96 Args: "Connect socket failed");
97
98#ifdef _WIN32
99 return _open_osfhandle(Socket, 0);
100#else
101 return Socket;
102#endif // _WIN32
103}
104
105ListeningSocket::ListeningSocket(int SocketFD, StringRef SocketPath,
106 int PipeFD[2])
107 : FD(SocketFD), SocketPath(SocketPath), PipeFD{PipeFD[0], PipeFD[1]} {}
108
109ListeningSocket::ListeningSocket(ListeningSocket &&LS)
110 : FD(LS.FD.load()), SocketPath(LS.SocketPath),
111 PipeFD{LS.PipeFD[0], LS.PipeFD[1]} {
112
113 LS.FD = -1;
114 LS.SocketPath.clear();
115 LS.PipeFD[0] = -1;
116 LS.PipeFD[1] = -1;
117}
118
119Expected<ListeningSocket> ListeningSocket::createUnix(StringRef SocketPath,
120 int MaxBacklog) {
121
122 // Handle instances where the target socket address already exists and
123 // differentiate between a preexisting file with and without a bound socket
124 //
125 // ::bind will return std::errc:address_in_use if a file at the socket address
126 // already exists (e.g., the file was not properly unlinked due to a crash)
127 // even if another socket has not yet binded to that address
128 if (llvm::sys::fs::exists(Path: SocketPath)) {
129 Expected<int> MaybeFD = getSocketFD(SocketPath);
130 if (!MaybeFD) {
131
132 // Regardless of the error, notify the caller that a file already exists
133 // at the desired socket address and that there is no bound socket at that
134 // address. The file must be removed before ::bind can use the address
135 consumeError(Err: MaybeFD.takeError());
136 return llvm::make_error<StringError>(
137 Args: std::make_error_code(e: std::errc::file_exists),
138 Args: "Socket address unavailable");
139 }
140 ::close(fd: std::move(*MaybeFD));
141
142 // Notify caller that the provided socket address already has a bound socket
143 return llvm::make_error<StringError>(
144 Args: std::make_error_code(e: std::errc::address_in_use),
145 Args: "Socket address unavailable");
146 }
147
148#ifdef _WIN32
149 WSABalancer _;
150 SOCKET Socket = socket(AF_UNIX, SOCK_STREAM, 0);
151 if (Socket == INVALID_SOCKET)
152#else
153 int Socket = socket(AF_UNIX, SOCK_STREAM, protocol: 0);
154 if (Socket == -1)
155#endif
156 return llvm::make_error<StringError>(Args: getLastSocketErrorCode(),
157 Args: "socket create failed");
158
159#ifdef __CYGWIN__
160 // On Cygwin, UNIX sockets involve a handshake between connect and accept
161 // to enable SO_PEERCRED/getpeereid handling. This necessitates accept being
162 // called before connect can return, but at least the tests in
163 // llvm/unittests/Support/raw_socket_stream_test do both on the same thread
164 // (first connect and then accept), resulting in a deadlock. This call turns
165 // off the handshake (and SO_PEERCRED/getpeereid support).
166 setsockopt(Socket, SOL_SOCKET, SO_PEERCRED, NULL, 0);
167#endif
168 struct sockaddr_un Addr = setSocketAddr(SocketPath);
169 if (::bind(fd: Socket, addr: (struct sockaddr *)&Addr, len: sizeof(Addr)) == -1) {
170 // Grab error code from call to ::bind before calling ::close
171 std::error_code EC = getLastSocketErrorCode();
172 ::close(fd: Socket);
173 return llvm::make_error<StringError>(Args&: EC, Args: "Bind error");
174 }
175
176 // Mark socket as passive so incoming connections can be accepted
177 if (::listen(fd: Socket, n: MaxBacklog) == -1)
178 return llvm::make_error<StringError>(Args: getLastSocketErrorCode(),
179 Args: "Listen error");
180
181 int PipeFD[2];
182#ifdef _WIN32
183 // Reserve 1 byte for the pipe and use default textmode
184 if (::_pipe(PipeFD, 1, 0) == -1)
185#else
186 if (::pipe(pipedes: PipeFD) == -1)
187#endif // _WIN32
188 return llvm::make_error<StringError>(Args: getLastSocketErrorCode(),
189 Args: "pipe failed");
190
191#ifdef _WIN32
192 return ListeningSocket{_open_osfhandle(Socket, 0), SocketPath, PipeFD};
193#else
194 return ListeningSocket{Socket, SocketPath, PipeFD};
195#endif // _WIN32
196}
197
198// If a file descriptor being monitored by ::poll is closed by another thread,
199// the result is unspecified. In the case ::poll does not unblock and return,
200// when ActiveFD is closed, you can provide another file descriptor via CancelFD
201// that when written to will cause poll to return. Typically CancelFD is the
202// read end of a unidirectional pipe.
203//
204// Timeout should be -1 to block indefinitly
205//
206// getActiveFD is a callback to handle ActiveFD's of std::atomic<int> and int
207static std::error_code
208manageTimeout(const std::chrono::milliseconds &Timeout,
209 const std::function<int()> &getActiveFD,
210 const std::optional<int> &CancelFD = std::nullopt) {
211 struct pollfd FD[2];
212 FD[0].events = POLLIN;
213#ifdef _WIN32
214 SOCKET WinServerSock = _get_osfhandle(getActiveFD());
215 FD[0].fd = WinServerSock;
216#else
217 FD[0].fd = getActiveFD();
218#endif
219 uint8_t FDCount = 1;
220 if (CancelFD.has_value()) {
221 FD[1].events = POLLIN;
222 FD[1].fd = CancelFD.value();
223 FDCount++;
224 }
225
226 // Keep track of how much time has passed in case ::poll or WSAPoll are
227 // interupted by a signal and need to be recalled
228 auto Start = std::chrono::steady_clock::now();
229 auto RemainingTimeout = Timeout;
230 int PollStatus = 0;
231 do {
232 // If Timeout is -1 then poll should block and RemainingTimeout does not
233 // need to be recalculated
234 if (PollStatus != 0 && Timeout != std::chrono::milliseconds(-1)) {
235 auto TotalElapsedTime =
236 std::chrono::duration_cast<std::chrono::milliseconds>(
237 d: std::chrono::steady_clock::now() - Start);
238
239 if (TotalElapsedTime >= Timeout)
240 return std::make_error_code(e: std::errc::operation_would_block);
241
242 RemainingTimeout = Timeout - TotalElapsedTime;
243 }
244#ifdef _WIN32
245 PollStatus = WSAPoll(FD, FDCount, RemainingTimeout.count());
246 } while (PollStatus == SOCKET_ERROR &&
247 getLastSocketErrorCode() == std::errc::interrupted);
248#else
249 PollStatus = ::poll(fds: FD, nfds: FDCount, timeout: RemainingTimeout.count());
250 } while (PollStatus == -1 &&
251 getLastSocketErrorCode() == std::errc::interrupted);
252#endif
253
254 // If ActiveFD equals -1 or CancelFD has data to be read then the operation
255 // has been canceled by another thread
256 if (getActiveFD() == -1 || (CancelFD.has_value() && FD[1].revents & POLLIN))
257 return std::make_error_code(e: std::errc::operation_canceled);
258#if _WIN32
259 if (PollStatus == SOCKET_ERROR)
260#else
261 if (PollStatus == -1)
262#endif
263 return getLastSocketErrorCode();
264 if (PollStatus == 0)
265 return std::make_error_code(e: std::errc::timed_out);
266 if (FD[0].revents & POLLNVAL)
267 return std::make_error_code(e: std::errc::bad_file_descriptor);
268 return std::error_code();
269}
270
271Expected<std::unique_ptr<raw_socket_stream>>
272ListeningSocket::accept(const std::chrono::milliseconds &Timeout) {
273 auto getActiveFD = [this]() -> int { return FD; };
274 std::error_code TimeoutErr = manageTimeout(Timeout, getActiveFD, CancelFD: PipeFD[0]);
275 if (TimeoutErr)
276 return llvm::make_error<StringError>(Args&: TimeoutErr, Args: "Timeout error");
277
278 int AcceptFD;
279#ifdef _WIN32
280 SOCKET WinAcceptSock = ::accept(_get_osfhandle(FD), NULL, NULL);
281 AcceptFD = _open_osfhandle(WinAcceptSock, 0);
282#else
283 AcceptFD = ::accept(fd: FD, NULL, NULL);
284#endif
285
286 if (AcceptFD == -1)
287 return llvm::make_error<StringError>(Args: getLastSocketErrorCode(),
288 Args: "Socket accept failed");
289 return std::make_unique<raw_socket_stream>(args&: AcceptFD);
290}
291
292void ListeningSocket::shutdown() {
293 int ObservedFD = FD.load();
294
295 if (ObservedFD == -1)
296 return;
297
298 // If FD equals ObservedFD set FD to -1; If FD doesn't equal ObservedFD then
299 // another thread is responsible for shutdown so return
300 if (!FD.compare_exchange_strong(i1&: ObservedFD, i2: -1))
301 return;
302
303 ::close(fd: ObservedFD);
304 ::unlink(name: SocketPath.c_str());
305
306 // Ensure ::poll returns if shutdown is called by a separate thread
307 char Byte = 'A';
308 ssize_t written = ::write(fd: PipeFD[1], buf: &Byte, n: 1);
309
310 // Ignore any write() error
311 (void)written;
312}
313
314ListeningSocket::~ListeningSocket() {
315 shutdown();
316
317 // Close the pipe's FDs in the destructor instead of within
318 // ListeningSocket::shutdown to avoid unnecessary synchronization issues that
319 // would occur as PipeFD's values would have to be changed to -1
320 //
321 // The move constructor sets PipeFD to -1
322 if (PipeFD[0] != -1)
323 ::close(fd: PipeFD[0]);
324 if (PipeFD[1] != -1)
325 ::close(fd: PipeFD[1]);
326}
327
328//===----------------------------------------------------------------------===//
329// raw_socket_stream
330//===----------------------------------------------------------------------===//
331
332raw_socket_stream::raw_socket_stream(int SocketFD)
333 : raw_fd_stream(SocketFD, true) {}
334
335raw_socket_stream::~raw_socket_stream() {}
336
337Expected<std::unique_ptr<raw_socket_stream>>
338raw_socket_stream::createConnectedUnix(StringRef SocketPath) {
339#ifdef _WIN32
340 WSABalancer _;
341#endif // _WIN32
342 Expected<int> FD = getSocketFD(SocketPath);
343 if (!FD)
344 return FD.takeError();
345 return std::make_unique<raw_socket_stream>(args&: *FD);
346}
347
348ssize_t raw_socket_stream::read(char *Ptr, size_t Size,
349 const std::chrono::milliseconds &Timeout) {
350 auto getActiveFD = [this]() -> int { return this->get_fd(); };
351 std::error_code Err = manageTimeout(Timeout, getActiveFD);
352 // Mimic raw_fd_stream::read error handling behavior
353 if (Err) {
354 raw_fd_stream::error_detected(EC: Err);
355 return -1;
356 }
357 return raw_fd_stream::read(Ptr, Size);
358}
359