TLA Line data Source code
1 : //
2 : // Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com)
3 : // Copyright (c) 2026 Steve Gerbino
4 : // Copyright (c) 2026 Michael Vandeberg
5 : //
6 : // Distributed under the Boost Software License, Version 1.0. (See accompanying
7 : // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
8 : //
9 : // Official repository: https://github.com/cppalliance/corosio
10 : //
11 :
12 : #ifndef BOOST_COROSIO_TCP_SOCKET_HPP
13 : #define BOOST_COROSIO_TCP_SOCKET_HPP
14 :
15 : #include <boost/corosio/detail/config.hpp>
16 : #include <boost/corosio/detail/platform.hpp>
17 : #include <boost/corosio/detail/except.hpp>
18 : #include <boost/corosio/detail/native_handle.hpp>
19 : #include <boost/corosio/detail/op_base.hpp>
20 : #include <boost/corosio/io/io_stream.hpp>
21 : #include <boost/capy/io_result.hpp>
22 : #include <boost/corosio/detail/buffer_param.hpp>
23 : #include <boost/corosio/endpoint.hpp>
24 : #include <boost/corosio/shutdown_type.hpp>
25 : #include <boost/corosio/tcp.hpp>
26 : #include <boost/corosio/wait_type.hpp>
27 : #include <boost/capy/ex/executor_ref.hpp>
28 : #include <boost/capy/ex/execution_context.hpp>
29 : #include <boost/capy/ex/io_env.hpp>
30 : #include <boost/capy/concept/executor.hpp>
31 :
32 : #include <system_error>
33 :
34 : #include <concepts>
35 : #include <coroutine>
36 : #include <cstddef>
37 : #include <stop_token>
38 : #include <type_traits>
39 :
40 : namespace boost::corosio {
41 :
42 : /** An asynchronous TCP socket for coroutine I/O.
43 :
44 : This class provides asynchronous TCP socket operations that return
45 : awaitable types. Each operation participates in the affine awaitable
46 : protocol, ensuring coroutines resume on the correct executor.
47 :
48 : The socket must be opened before performing I/O operations. Operations
49 : support cancellation through `std::stop_token` via the affine protocol,
50 : or explicitly through the `cancel()` member function.
51 :
52 : @par Thread Safety
53 : Distinct objects: Safe.@n
54 : Shared objects: Unsafe. A socket must not have concurrent operations
55 : of the same type (e.g., two simultaneous reads). One read and one
56 : write may be in flight simultaneously.
57 :
58 : @par Semantics
59 : Wraps the platform TCP/IP stack. Operations dispatch to
60 : OS socket APIs via the io_context reactor (epoll, IOCP,
61 : kqueue). Satisfies @ref capy::Stream.
62 :
63 : @par Example
64 : @par !example connect_and_read
65 : */
66 : class BOOST_COROSIO_DECL tcp_socket : public io_stream
67 : {
68 : public:
69 : /// The endpoint type used by this socket.
70 : using endpoint_type = corosio::endpoint;
71 :
72 : using shutdown_type = corosio::shutdown_type;
73 : using enum corosio::shutdown_type;
74 :
75 : /** Define backend hooks for TCP socket operations.
76 :
77 : Platform backends (epoll, IOCP, kqueue, select) derive from
78 : this to implement socket I/O, connection, and option management.
79 : */
80 : struct implementation : io_stream::implementation
81 : {
82 : /** Initiate an asynchronous connect to the given endpoint.
83 :
84 : @param h Coroutine handle to resume on completion.
85 : @param ex Executor for dispatching the completion.
86 : @param ep The remote endpoint to connect to.
87 : @param token Stop token for cancellation.
88 : @param ec Output error code.
89 :
90 : @return Coroutine handle to resume immediately.
91 : */
92 : virtual std::coroutine_handle<> connect(
93 : std::coroutine_handle<> h,
94 : capy::executor_ref ex,
95 : endpoint ep,
96 : std::stop_token token,
97 : std::error_code* ec) = 0;
98 :
99 : /** Initiate an asynchronous wait for socket readiness.
100 :
101 : Completes when the socket becomes ready for the
102 : specified direction, or an error condition is
103 : reported. No bytes are transferred.
104 :
105 : @param h Coroutine handle to resume on completion.
106 : @param ex Executor for dispatching the completion.
107 : @param w The direction to wait on.
108 : @param token Stop token for cancellation.
109 : @param ec Output error code.
110 :
111 : @return Coroutine handle to resume immediately.
112 : */
113 : virtual std::coroutine_handle<> wait(
114 : std::coroutine_handle<> h,
115 : capy::executor_ref ex,
116 : wait_type w,
117 : std::stop_token token,
118 : std::error_code* ec) = 0;
119 :
120 : /** Shut down the socket for the given direction(s).
121 :
122 : @param what The shutdown direction.
123 :
124 : @return Error code on failure, empty on success.
125 : */
126 : virtual std::error_code shutdown(shutdown_type what) noexcept = 0;
127 :
128 : /// Return the platform socket descriptor.
129 : virtual native_handle_type native_handle() const noexcept = 0;
130 :
131 : /** Release ownership of the native socket handle.
132 :
133 : Deregisters the socket from the backend and cancels
134 : pending operations without closing the descriptor. The
135 : caller takes ownership.
136 :
137 : @return The native handle.
138 : */
139 : virtual native_handle_type release_socket() noexcept = 0;
140 :
141 : /** Request cancellation of pending asynchronous operations.
142 :
143 : Operations still in flight complete with `operation_canceled`; an
144 : operation whose result is already decided reports that result.
145 : Check `ec == cond::canceled` for portable comparison.
146 : */
147 : virtual void cancel() noexcept = 0;
148 :
149 : /** Set a socket option.
150 :
151 : @param level The protocol level (e.g. `SOL_SOCKET`).
152 : @param optname The option name (e.g. `SO_KEEPALIVE`).
153 : @param data Pointer to the option value.
154 : @param size Size of the option value in bytes.
155 : @return Error code on failure, empty on success.
156 : */
157 : virtual std::error_code set_option(
158 : int level,
159 : int optname,
160 : void const* data,
161 : std::size_t size) noexcept = 0;
162 :
163 : /** Get a socket option.
164 :
165 : @param level The protocol level (e.g. `SOL_SOCKET`).
166 : @param optname The option name (e.g. `SO_KEEPALIVE`).
167 : @param data Pointer to receive the option value.
168 : @param size On entry, the size of the buffer. On exit,
169 : the size of the option value.
170 : @return Error code on failure, empty on success.
171 : */
172 : virtual std::error_code
173 : get_option(int level, int optname, void* data, std::size_t* size)
174 : const noexcept = 0;
175 :
176 : /// Return the cached local endpoint.
177 : virtual endpoint local_endpoint() const noexcept = 0;
178 :
179 : /// Return the cached remote endpoint.
180 : virtual endpoint remote_endpoint() const noexcept = 0;
181 : };
182 :
183 : /// Represent the awaitable returned by @ref connect.
184 : struct connect_awaitable : detail::void_op_base<connect_awaitable>
185 : {
186 : tcp_socket& s_;
187 : endpoint endpoint_;
188 :
189 HIT 4401 : connect_awaitable(tcp_socket& s, endpoint ep) noexcept
190 8802 : : s_(s)
191 4401 : , endpoint_(ep)
192 : {
193 4401 : }
194 :
195 : std::coroutine_handle<>
196 4398 : dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const
197 : {
198 4398 : return s_.get().connect(h, ex, endpoint_, token_, &ec_);
199 : }
200 : };
201 :
202 : /// Represent the awaitable returned by @ref wait.
203 : struct wait_awaitable : detail::void_op_base<wait_awaitable>
204 : {
205 : tcp_socket& s_;
206 : wait_type w_;
207 :
208 68 : wait_awaitable(tcp_socket& s, wait_type w) noexcept : s_(s), w_(w) {}
209 :
210 : std::coroutine_handle<>
211 64 : dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const
212 : {
213 64 : return s_.get().wait(h, ex, w_, token_, &ec_);
214 : }
215 : };
216 :
217 : public:
218 : /** Destructor.
219 :
220 : Closes the socket if open, cancelling any pending operations.
221 : */
222 : ~tcp_socket() override;
223 :
224 : /** Construct a socket from an execution context.
225 :
226 : @param ctx The execution context that will own this socket.
227 : */
228 : explicit tcp_socket(capy::execution_context& ctx);
229 :
230 : /** Construct a socket from an executor.
231 :
232 : The socket is associated with the executor's context.
233 :
234 : @param ex The executor whose context will own the socket.
235 : */
236 : template<class Ex>
237 : requires(!std::same_as<std::remove_cvref_t<Ex>, tcp_socket>) &&
238 : capy::Executor<Ex>
239 1 : explicit tcp_socket(Ex const& ex) : tcp_socket(ex.context())
240 : {
241 1 : }
242 :
243 : /** Move constructor.
244 :
245 : Transfers ownership of the socket resources.
246 :
247 : @param other The socket to move from.
248 :
249 : @pre No awaitables returned by @p other's methods exist.
250 : @pre @p other is not referenced as a peer in any outstanding
251 : accept awaitable.
252 : @pre The execution context associated with @p other must
253 : outlive this socket.
254 : */
255 701 : tcp_socket(tcp_socket&& other) noexcept : io_object(std::move(other)) {}
256 :
257 : /** Move assignment operator.
258 :
259 : Closes any existing socket and transfers ownership.
260 :
261 : @param other The socket to move from.
262 :
263 : @pre No awaitables returned by either `*this` or @p other's
264 : methods exist.
265 : @pre Neither `*this` nor @p other is referenced as a peer in
266 : any outstanding accept awaitable.
267 : @pre The execution context associated with @p other must
268 : outlive this socket.
269 :
270 : @return Reference to this socket.
271 : */
272 25 : tcp_socket& operator=(tcp_socket&& other) noexcept
273 : {
274 25 : if (this != &other)
275 : {
276 25 : close();
277 25 : h_ = std::move(other.h_);
278 : }
279 25 : return *this;
280 : }
281 :
282 : tcp_socket(tcp_socket const&) = delete;
283 : tcp_socket& operator=(tcp_socket const&) = delete;
284 :
285 : /** Open the socket.
286 :
287 : Creates a TCP socket and associates it with the platform
288 : reactor (IOCP on Windows). Calling @ref connect on a closed
289 : socket opens it automatically with the endpoint's address family,
290 : so explicit `open()` is only needed when socket options must be
291 : set before connecting.
292 :
293 : Failures such as descriptor exhaustion are normal runtime
294 : conditions and are reported through the returned error code.
295 : Opening an already-open socket is a no-op that reports
296 : success.
297 :
298 : @param proto The protocol (IPv4 or IPv6). Defaults to
299 : `tcp::v4()`.
300 :
301 : @return The error code, empty on success.
302 : */
303 : [[nodiscard]] std::error_code open(tcp proto = tcp::v4()) noexcept;
304 :
305 : /** Bind the socket to a local endpoint.
306 :
307 : Associates the socket with a local address and port before
308 : connecting. Useful for multi-homed hosts or source-port
309 : pinning.
310 :
311 : @param ep The local endpoint to bind to.
312 :
313 : @return An error code indicating success or the reason for
314 : failure.
315 :
316 : @par Error Conditions
317 : @li `errc::address_in_use`: The endpoint is already in use.
318 : @li `errc::address_not_available`: The address is not
319 : available on any local interface.
320 : @li `errc::permission_denied`: Insufficient privileges to
321 : bind to the endpoint (e.g., privileged port).
322 :
323 : A closed socket reports `errc::bad_file_descriptor`.
324 : */
325 : [[nodiscard]] std::error_code bind(endpoint ep) noexcept;
326 :
327 : /** Close the socket.
328 :
329 : Releases socket resources. Any pending operations complete
330 : with `errc::operation_canceled`.
331 : */
332 : void close() noexcept;
333 :
334 : /** Check if the socket is open.
335 :
336 : @return `true` if the socket is open and ready for operations.
337 : */
338 28156 : bool is_open() const noexcept
339 : {
340 : #if BOOST_COROSIO_HAS_IOCP && !defined(BOOST_COROSIO_MRDOCS)
341 : return h_ && get().native_handle() != ~native_handle_type(0);
342 : #else
343 28156 : return h_ && get().native_handle() >= 0;
344 : #endif
345 : }
346 :
347 : /** Initiate an asynchronous connect operation.
348 :
349 : If the socket is not already open, it is opened automatically
350 : using the address family of @p ep (IPv4 or IPv6). If the socket
351 : is already open, the existing file descriptor is used as-is.
352 :
353 : The operation supports cancellation via `std::stop_token` through
354 : the affine awaitable protocol. If the associated stop token is
355 : triggered, the operation completes immediately with
356 : `errc::operation_canceled`.
357 :
358 : @param ep The remote endpoint to connect to.
359 :
360 : @return An awaitable that completes with `io_result<>`.
361 : Returns success (default error_code) on successful connection,
362 : or an error code on failure including:
363 : - connection_refused: No server listening at endpoint
364 : - timed_out: Connection attempt timed out
365 : - network_unreachable: No route to host
366 : - operation_canceled: Cancelled via stop_token or cancel().
367 : Check `ec == cond::canceled` for portable comparison.
368 :
369 : If the socket needs to be opened and the open fails, the
370 : awaitable completes immediately with that error.
371 :
372 : @par Preconditions
373 : This socket must outlive the returned awaitable.
374 :
375 : @par Example
376 : @par !example connect
377 : */
378 4401 : [[nodiscard]] auto connect(endpoint ep)
379 : {
380 4401 : connect_awaitable aw(*this, ep);
381 4401 : if (!is_open())
382 87 : aw.ec_ = open(ep.is_v6() ? tcp::v6() : tcp::v4());
383 4401 : return aw;
384 : }
385 :
386 : /** Wait for the socket to become ready in a given direction.
387 :
388 : Suspends until the socket is ready for the requested
389 : direction, or an error condition is reported. No bytes
390 : are transferred — useful for integrating with C libraries
391 : that own the I/O on a nonblocking fd and only need
392 : readiness notification (e.g. libpq async, libssh).
393 :
394 : The operation supports cancellation via `std::stop_token`
395 : through the affine awaitable protocol. If the associated
396 : stop token is triggered, the operation completes
397 : immediately with `errc::operation_canceled`.
398 :
399 : @param w The wait direction (read, write, or error).
400 :
401 : @return An awaitable that completes with `io_result<>`.
402 : On success, no bytes have been consumed from the
403 : stream; a subsequent `read_some` (for read waits)
404 : returns the available data.
405 :
406 : A closed socket completes with `errc::bad_file_descriptor`.
407 :
408 : @par Preconditions
409 : This socket must outlive the returned awaitable.
410 : */
411 68 : [[nodiscard]] auto wait(wait_type w)
412 : {
413 68 : return wait_awaitable(*this, w);
414 : }
415 :
416 : /** Cancel any pending asynchronous operations.
417 :
418 : Operations still in flight complete with `errc::operation_canceled`;
419 : an operation whose result is already decided reports that result.
420 : Check `ec == cond::canceled` for portable comparison.
421 : */
422 : void cancel() noexcept;
423 :
424 : /** Get the native socket handle.
425 :
426 : Returns the underlying platform-specific socket descriptor.
427 : On POSIX systems this is an `int` file descriptor.
428 : On Windows this is a `SOCKET` handle.
429 :
430 : @return The native socket handle, or -1/INVALID_SOCKET if not open.
431 :
432 : @par Preconditions
433 : None. May be called on closed sockets.
434 : */
435 : native_handle_type native_handle() const noexcept;
436 :
437 : /** Assign an existing native socket to this object.
438 :
439 : Adopts a TCP socket created outside the library — received
440 : from another process, inherited, or made natively — and
441 : registers it with the backend. The socket must be a stream
442 : socket in the `AF_INET` or `AF_INET6` family. Adoption never
443 : alters the descriptor's flags or options: on POSIX the fd
444 : must already be non-blocking, and on Windows the socket must
445 : be overlapped-capable.
446 :
447 : If this object is already open, pending operations complete
448 : with `errc::operation_canceled` and the held socket is
449 : closed before the new one is adopted.
450 :
451 : @par Exception Safety
452 : Strong guarantee on validation failure: the object is
453 : unchanged. If backend registration fails, the object either
454 : retains its previous socket or is left closed, depending on
455 : the backend. In all failure cases the caller retains
456 : ownership of `fd`.
457 :
458 : @param fd The native socket to adopt. On success the object
459 : owns it and will close it.
460 :
461 : @return The error code, empty on success. Validation and
462 : registration failures are normal runtime conditions when
463 : adopting foreign descriptors.
464 : */
465 : [[nodiscard]] std::error_code assign(native_handle_type fd) noexcept;
466 :
467 : /** Release ownership of the native socket handle.
468 :
469 : Deregisters the socket from the backend and cancels pending
470 : operations without closing the descriptor. The caller takes
471 : ownership of the returned handle.
472 :
473 : @return The native handle.
474 :
475 : @throws std::system_error `errc::bad_file_descriptor` if the
476 : socket is not open.
477 :
478 : @post is_open() == false
479 : */
480 : native_handle_type release();
481 :
482 : /** Disable sends or receives on the socket.
483 :
484 : TCP connections are full-duplex: each direction (send and receive)
485 : operates independently. This function allows you to close one or
486 : both directions without destroying the socket.
487 :
488 : @li @ref shutdown_send sends a TCP FIN packet to the peer,
489 : signaling that you have no more data to send. You can still
490 : receive data until the peer also closes their send direction.
491 : This is the most common use case, typically called before
492 : close() to ensure graceful connection termination.
493 :
494 : @li @ref shutdown_receive disables reading on the socket. This
495 : does NOT send anything to the peer - they are not informed
496 : and may continue sending data. Subsequent reads will fail
497 : or return end-of-file. Incoming data may be discarded or
498 : buffered depending on the operating system.
499 :
500 : @li @ref shutdown_both combines both effects: sends a FIN and
501 : disables reading.
502 :
503 : When the peer shuts down their send direction (sends a FIN),
504 : subsequent read operations will complete with `capy::cond::eof`.
505 : Use the portable condition test rather than comparing error
506 : codes directly:
507 :
508 : @par !example shutdown
509 :
510 : Failures such as a peer that already disconnected are
511 : normal runtime conditions and are reported through the
512 : returned error code. A closed socket reports
513 : `errc::bad_file_descriptor`.
514 :
515 : @param what Determines what operations will no longer be allowed.
516 :
517 : @return The error code, empty on success.
518 : */
519 : [[nodiscard]] std::error_code shutdown(shutdown_type what) noexcept;
520 :
521 : /** Set a socket option.
522 :
523 : Applies a type-safe socket option to the underlying socket.
524 : The option type encodes the protocol level and option name.
525 :
526 : @par Example
527 : @par !example set_option
528 :
529 : @param opt The option to set.
530 :
531 : @throws std::system_error `errc::bad_file_descriptor` if the
532 : socket is not open; otherwise thrown on failure.
533 : */
534 : template<class Option>
535 288 : void set_option(Option const& opt)
536 : {
537 288 : if (!is_open())
538 2 : detail::throw_system_error(
539 4 : make_error_code(std::errc::bad_file_descriptor),
540 : "tcp_socket::set_option");
541 286 : std::error_code ec = get().set_option(
542 : Option::level(), Option::name(), opt.data(), opt.size());
543 286 : if (ec)
544 7 : detail::throw_system_error(ec, "tcp_socket::set_option");
545 279 : }
546 :
547 : /** Get a socket option.
548 :
549 : Retrieves the current value of a type-safe socket option.
550 :
551 : @par Example
552 : @par !example get_option
553 :
554 : @return The current option value.
555 :
556 : @throws std::system_error `errc::bad_file_descriptor` if the
557 : socket is not open; otherwise thrown on failure.
558 : */
559 : template<class Option>
560 97 : Option get_option() const
561 : {
562 97 : if (!is_open())
563 2 : detail::throw_system_error(
564 4 : make_error_code(std::errc::bad_file_descriptor),
565 : "tcp_socket::get_option");
566 95 : Option opt{};
567 95 : std::size_t sz = opt.size();
568 : std::error_code ec =
569 95 : get().get_option(Option::level(), Option::name(), opt.data(), &sz);
570 95 : if (ec)
571 7 : detail::throw_system_error(ec, "tcp_socket::get_option");
572 88 : opt.resize(sz);
573 88 : return opt;
574 : }
575 :
576 : /** Get the local endpoint of the socket.
577 :
578 : Returns the local address and port to which the socket is bound.
579 : For a connected socket, this is the local side of the connection.
580 : The endpoint is cached when the connection is established.
581 :
582 : @return The local endpoint, or a default endpoint (0.0.0.0:0) if
583 : the socket is not connected.
584 :
585 : @par Thread Safety
586 : The cached endpoint value is set during connect/accept completion
587 : and cleared during close(). This function may be called concurrently
588 : with I/O operations, but must not be called concurrently with
589 : connect(), accept(), or close().
590 : */
591 : endpoint local_endpoint() const noexcept;
592 :
593 : /** Get the remote endpoint of the socket.
594 :
595 : Returns the remote address and port to which the socket is connected.
596 : The endpoint is cached when the connection is established.
597 :
598 : @return The remote endpoint, or a default endpoint (0.0.0.0:0) if
599 : the socket is not connected.
600 :
601 : @par Thread Safety
602 : The cached endpoint value is set during connect/accept completion
603 : and cleared during close(). This function may be called concurrently
604 : with I/O operations, but must not be called concurrently with
605 : connect(), accept(), or close().
606 : */
607 : endpoint remote_endpoint() const noexcept;
608 :
609 : protected:
610 55 : tcp_socket() noexcept = default;
611 :
612 : explicit tcp_socket(handle h) noexcept : io_object(std::move(h)) {}
613 :
614 : private:
615 : friend class tcp_acceptor;
616 :
617 : /// Open the socket for the given protocol triple.
618 : [[nodiscard]] std::error_code
619 : open_for_family(int family, int type, int protocol) noexcept;
620 :
621 32664 : inline implementation& get() const noexcept
622 : {
623 32664 : return *static_cast<implementation*>(h_.get());
624 : }
625 : };
626 :
627 : } // namespace boost::corosio
628 :
629 : #endif
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