Line data Source code
1 : //
2 : // Copyright (c) 2026 Steve Gerbino
3 : //
4 : // Distributed under the Boost Software License, Version 1.0. (See accompanying
5 : // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6 : //
7 : // Official repository: https://github.com/cppalliance/corosio
8 : //
9 :
10 : #ifndef BOOST_COROSIO_DETAIL_EPOLL_SOCKETS_HPP
11 : #define BOOST_COROSIO_DETAIL_EPOLL_SOCKETS_HPP
12 :
13 : #include <boost/corosio/detail/platform.hpp>
14 :
15 : #if BOOST_COROSIO_HAS_EPOLL
16 :
17 : #include <boost/corosio/detail/config.hpp>
18 : #include <boost/corosio/tcp_socket.hpp>
19 : #include <boost/capy/ex/executor_ref.hpp>
20 : #include <boost/capy/ex/execution_context.hpp>
21 : #include "src/detail/intrusive.hpp"
22 : #include "src/detail/socket_service.hpp"
23 :
24 : #include "src/detail/cached_initiator.hpp"
25 : #include "src/detail/epoll/op.hpp"
26 : #include "src/detail/epoll/scheduler.hpp"
27 :
28 : #include <coroutine>
29 : #include <memory>
30 : #include <mutex>
31 : #include <unordered_map>
32 :
33 : /*
34 : epoll Socket Implementation
35 : ===========================
36 :
37 : Each I/O operation follows the same pattern:
38 : 1. Try the syscall immediately (non-blocking socket)
39 : 2. If it succeeds or fails with a real error, post to completion queue
40 : 3. If EAGAIN/EWOULDBLOCK, register with epoll and wait
41 :
42 : This "try first" approach avoids unnecessary epoll round-trips for
43 : operations that can complete immediately (common for small reads/writes
44 : on fast local connections).
45 :
46 : One-Shot Registration
47 : ---------------------
48 : We use one-shot epoll registration: each operation registers, waits for
49 : one event, then unregisters. This simplifies the state machine since we
50 : don't need to track whether an fd is currently registered or handle
51 : re-arming. The tradeoff is slightly more epoll_ctl calls, but the
52 : simplicity is worth it.
53 :
54 : Cancellation
55 : ------------
56 : See op.hpp for the completion/cancellation race handling via the
57 : `registered` atomic. cancel() must complete pending operations (post
58 : them with cancelled flag) so coroutines waiting on them can resume.
59 : close_socket() calls cancel() first to ensure this.
60 :
61 : Impl Lifetime with shared_ptr
62 : -----------------------------
63 : Socket impls use enable_shared_from_this. The service owns impls via
64 : shared_ptr maps (socket_ptrs_) keyed by raw pointer for O(1) lookup and
65 : removal. When a user calls close(), we call cancel() which posts pending
66 : ops to the scheduler.
67 :
68 : CRITICAL: The posted ops must keep the impl alive until they complete.
69 : Otherwise the scheduler would process a freed op (use-after-free). The
70 : cancel() method captures shared_from_this() into op.impl_ptr before
71 : posting. When the op completes, impl_ptr is cleared, allowing the impl
72 : to be destroyed if no other references exist.
73 :
74 : Service Ownership
75 : -----------------
76 : epoll_socket_service owns all socket impls. destroy_impl() removes the
77 : shared_ptr from the map, but the impl may survive if ops still hold
78 : impl_ptr refs. shutdown() closes all sockets and clears the map; any
79 : in-flight ops will complete and release their refs.
80 : */
81 :
82 : namespace boost::corosio::detail {
83 :
84 : class epoll_socket_service;
85 : class epoll_socket_impl;
86 :
87 : /// Socket implementation for epoll backend.
88 : class epoll_socket_impl
89 : : public tcp_socket::socket_impl
90 : , public std::enable_shared_from_this<epoll_socket_impl>
91 : , public intrusive_list<epoll_socket_impl>::node
92 : {
93 : friend class epoll_socket_service;
94 :
95 : public:
96 : explicit epoll_socket_impl(epoll_socket_service& svc) noexcept;
97 : ~epoll_socket_impl();
98 :
99 : void release() override;
100 :
101 : std::coroutine_handle<> connect(
102 : std::coroutine_handle<>,
103 : capy::executor_ref,
104 : endpoint,
105 : std::stop_token,
106 : std::error_code*) override;
107 :
108 : std::coroutine_handle<> read_some(
109 : std::coroutine_handle<>,
110 : capy::executor_ref,
111 : io_buffer_param,
112 : std::stop_token,
113 : std::error_code*,
114 : std::size_t*) override;
115 :
116 : std::coroutine_handle<> write_some(
117 : std::coroutine_handle<>,
118 : capy::executor_ref,
119 : io_buffer_param,
120 : std::stop_token,
121 : std::error_code*,
122 : std::size_t*) override;
123 :
124 : std::error_code shutdown(tcp_socket::shutdown_type what) noexcept override;
125 :
126 0 : native_handle_type native_handle() const noexcept override { return fd_; }
127 :
128 : // Socket options
129 : std::error_code set_no_delay(bool value) noexcept override;
130 : bool no_delay(std::error_code& ec) const noexcept override;
131 :
132 : std::error_code set_keep_alive(bool value) noexcept override;
133 : bool keep_alive(std::error_code& ec) const noexcept override;
134 :
135 : std::error_code set_receive_buffer_size(int size) noexcept override;
136 : int receive_buffer_size(std::error_code& ec) const noexcept override;
137 :
138 : std::error_code set_send_buffer_size(int size) noexcept override;
139 : int send_buffer_size(std::error_code& ec) const noexcept override;
140 :
141 : std::error_code set_linger(bool enabled, int timeout) noexcept override;
142 : tcp_socket::linger_options linger(std::error_code& ec) const noexcept override;
143 :
144 16 : endpoint local_endpoint() const noexcept override { return local_endpoint_; }
145 16 : endpoint remote_endpoint() const noexcept override { return remote_endpoint_; }
146 : bool is_open() const noexcept { return fd_ >= 0; }
147 : void cancel() noexcept override;
148 : void cancel_single_op(epoll_op& op) noexcept;
149 : void close_socket() noexcept;
150 5017 : void set_socket(int fd) noexcept { fd_ = fd; }
151 10034 : void set_endpoints(endpoint local, endpoint remote) noexcept
152 : {
153 10034 : local_endpoint_ = local;
154 10034 : remote_endpoint_ = remote;
155 10034 : }
156 :
157 : epoll_connect_op conn_;
158 : epoll_read_op rd_;
159 : epoll_write_op wr_;
160 :
161 : /// Per-descriptor state for persistent epoll registration
162 : descriptor_state desc_state_;
163 :
164 : cached_initiator read_initiator_;
165 : cached_initiator write_initiator_;
166 :
167 : /// Execute the read I/O operation (called by initiator coroutine).
168 : void do_read_io();
169 :
170 : /// Execute the write I/O operation (called by initiator coroutine).
171 : void do_write_io();
172 :
173 : private:
174 : epoll_socket_service& svc_;
175 : int fd_ = -1;
176 : endpoint local_endpoint_;
177 : endpoint remote_endpoint_;
178 : };
179 :
180 : /** State for epoll socket service. */
181 : class epoll_socket_state
182 : {
183 : public:
184 189 : explicit epoll_socket_state(epoll_scheduler& sched) noexcept
185 189 : : sched_(sched)
186 : {
187 189 : }
188 :
189 : epoll_scheduler& sched_;
190 : std::mutex mutex_;
191 : intrusive_list<epoll_socket_impl> socket_list_;
192 : std::unordered_map<epoll_socket_impl*, std::shared_ptr<epoll_socket_impl>> socket_ptrs_;
193 : };
194 :
195 : /** epoll socket service implementation.
196 :
197 : Inherits from socket_service to enable runtime polymorphism.
198 : Uses key_type = socket_service for service lookup.
199 : */
200 : class epoll_socket_service : public socket_service
201 : {
202 : public:
203 : explicit epoll_socket_service(capy::execution_context& ctx);
204 : ~epoll_socket_service();
205 :
206 : epoll_socket_service(epoll_socket_service const&) = delete;
207 : epoll_socket_service& operator=(epoll_socket_service const&) = delete;
208 :
209 : void shutdown() override;
210 :
211 : tcp_socket::socket_impl& create_impl() override;
212 : void destroy_impl(tcp_socket::socket_impl& impl) override;
213 : std::error_code open_socket(tcp_socket::socket_impl& impl) override;
214 :
215 20092 : epoll_scheduler& scheduler() const noexcept { return state_->sched_; }
216 : void post(epoll_op* op);
217 : void work_started() noexcept;
218 : void work_finished() noexcept;
219 :
220 : private:
221 : std::unique_ptr<epoll_socket_state> state_;
222 : };
223 :
224 : } // namespace boost::corosio::detail
225 :
226 : #endif // BOOST_COROSIO_HAS_EPOLL
227 :
228 : #endif // BOOST_COROSIO_DETAIL_EPOLL_SOCKETS_HPP
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