TLA Line data Source code
1 : //
2 : // Copyright (c) 2026 Michael Vandeberg
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_NATIVE_DETAIL_SELECT_SELECT_TRAITS_HPP
11 : #define BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_TRAITS_HPP
12 :
13 : #include <boost/corosio/detail/platform.hpp>
14 :
15 : #if BOOST_COROSIO_HAS_SELECT
16 :
17 : #include <boost/corosio/native/detail/make_err.hpp>
18 : #include <boost/corosio/native/detail/reactor/reactor_descriptor_state.hpp>
19 :
20 : #include <system_error>
21 : #include <tuple>
22 :
23 : #include <errno.h>
24 : #include <fcntl.h>
25 : #include <netinet/in.h>
26 : #include <sys/select.h>
27 : #include <sys/socket.h>
28 : #include <sys/uio.h>
29 : #include <unistd.h>
30 :
31 : /* select backend traits.
32 :
33 : Captures the platform-specific behavior of the portable select() backend:
34 : manual fcntl for O_NONBLOCK/FD_CLOEXEC, FD_SETSIZE validation,
35 : mandatory SO_NOSIGPIPE where the platform defines it,
36 : sendmsg(MSG_NOSIGNAL) where available, and accept()+fcntl for
37 : accepted connections.
38 : */
39 :
40 : namespace boost::corosio::detail {
41 :
42 : class select_scheduler;
43 :
44 : struct select_traits
45 : {
46 : using scheduler_type = select_scheduler;
47 : using desc_state_type = reactor_descriptor_state;
48 :
49 : static constexpr bool needs_write_notification = true;
50 :
51 : // No extra per-socket state or lifecycle hooks needed for select.
52 : struct stream_socket_hook
53 : {
54 HIT 107 : std::error_code on_set_option(
55 : int fd,
56 : int level,
57 : int optname,
58 : void const* data,
59 : std::size_t size) noexcept
60 : {
61 107 : if (::setsockopt(
62 107 : fd, level, optname, data, static_cast<socklen_t>(size)) !=
63 : 0)
64 4 : return make_err(errno);
65 103 : return {};
66 : }
67 19276 : static void pre_shutdown(int) noexcept {}
68 6260 : static void pre_destroy(int) noexcept {}
69 : };
70 :
71 : struct write_policy
72 : {
73 72 : static ssize_t write(int fd, iovec* iovecs, int count) noexcept
74 : {
75 72 : msghdr msg{};
76 72 : msg.msg_iov = iovecs;
77 72 : msg.msg_iovlen = static_cast<std::size_t>(count);
78 :
79 : #ifdef MSG_NOSIGNAL
80 72 : constexpr int send_flags = MSG_NOSIGNAL;
81 : #else
82 : constexpr int send_flags = 0;
83 : #endif
84 :
85 : ssize_t n;
86 : do
87 : {
88 73 : n = ::sendmsg(fd, &msg, send_flags);
89 : }
90 73 : while (n < 0 && errno == EINTR);
91 72 : return n;
92 : }
93 :
94 : // Single-buffer fast path. Where MSG_NOSIGNAL exists we use
95 : // send() to suppress SIGPIPE inline; otherwise fall back to
96 : // write() and rely on the SO_NOSIGPIPE set in accept_policy
97 : // and set_fd_options.
98 : static ssize_t
99 103468 : write_one(int fd, void const* data, std::size_t size) noexcept
100 : {
101 : ssize_t n;
102 : do
103 : {
104 : #ifdef MSG_NOSIGNAL
105 103469 : n = ::send(fd, data, size, MSG_NOSIGNAL);
106 : #else
107 : n = ::write(fd, data, size);
108 : #endif
109 : }
110 103469 : while (n < 0 && errno == EINTR);
111 103468 : return n;
112 : }
113 : };
114 :
115 : // Descriptors are not sockets: sendmsg() fails with ENOTSOCK on a
116 : // pipe or character device, so the write path is writev()/write()
117 : // and SIGPIPE suppression is structurally unavailable -- MSG_NOSIGNAL
118 : // is a send() flag and SO_NOSIGPIPE a socket option. A write to a
119 : // pipe whose read end has closed raises SIGPIPE, exactly as a plain
120 : // write(2) would; callers install SIG_IGN.
121 : struct descriptor_write_policy
122 : {
123 2 : static ssize_t write(int fd, iovec* iovecs, int count) noexcept
124 : {
125 : ssize_t n;
126 : do
127 : {
128 2 : n = ::writev(fd, iovecs, count);
129 : }
130 2 : while (n < 0 && errno == EINTR);
131 2 : return n;
132 : }
133 :
134 : // Single-buffer fast path: skips the kernel's iov_iter setup.
135 : static ssize_t
136 2 : write_one(int fd, void const* data, std::size_t size) noexcept
137 : {
138 : ssize_t n;
139 : do
140 : {
141 2 : n = ::write(fd, data, size);
142 : }
143 2 : while (n < 0 && errno == EINTR);
144 2 : return n;
145 : }
146 : };
147 :
148 : struct accept_policy
149 : {
150 : static int
151 4112 : do_accept(int fd, sockaddr_storage& peer, socklen_t& addrlen) noexcept
152 : {
153 4112 : addrlen = sizeof(peer);
154 : int new_fd;
155 : do
156 : {
157 : new_fd =
158 4113 : ::accept(fd, reinterpret_cast<sockaddr*>(&peer), &addrlen);
159 : }
160 4113 : while (new_fd < 0 && errno == EINTR);
161 :
162 4112 : if (new_fd < 0)
163 2061 : return new_fd;
164 :
165 2051 : if (new_fd >= FD_SETSIZE)
166 : {
167 1 : ::close(new_fd);
168 1 : errno = EMFILE;
169 1 : return -1;
170 : }
171 :
172 2050 : int flags = ::fcntl(new_fd, F_GETFL, 0);
173 2050 : if (flags == -1)
174 : {
175 1 : int err = errno;
176 1 : ::close(new_fd);
177 1 : errno = err;
178 1 : return -1;
179 : }
180 :
181 2049 : if (::fcntl(new_fd, F_SETFL, flags | O_NONBLOCK) == -1)
182 : {
183 1 : int err = errno;
184 1 : ::close(new_fd);
185 1 : errno = err;
186 1 : return -1;
187 : }
188 :
189 2048 : if (::fcntl(new_fd, F_SETFD, FD_CLOEXEC) == -1)
190 : {
191 1 : int err = errno;
192 1 : ::close(new_fd);
193 1 : errno = err;
194 1 : return -1;
195 : }
196 :
197 : #ifdef SO_NOSIGPIPE
198 : // MSG_NOSIGNAL is not universal across the platforms this
199 : // portable backend covers, and the write() the fast path
200 : // falls back to there takes no flag at all; SO_NOSIGPIPE is
201 : // the per-descriptor guard that covers both. Treat failure
202 : // as fatal, matching the kqueue backend.
203 : int one = 1;
204 : if (::setsockopt(
205 : new_fd, SOL_SOCKET, SO_NOSIGPIPE, &one, sizeof(one)) != 0)
206 : {
207 : int err = errno;
208 : ::close(new_fd);
209 : errno = err;
210 : return -1;
211 : }
212 : #endif
213 :
214 2047 : return new_fd;
215 : }
216 : };
217 :
218 : // Create a plain socket (no atomic flags -- select is POSIX-portable).
219 2656 : static int create_socket(int family, int type, int protocol) noexcept
220 : {
221 2656 : return ::socket(family, type, protocol);
222 : }
223 :
224 : // Set O_NONBLOCK, FD_CLOEXEC; check FD_SETSIZE; optionally SO_NOSIGPIPE.
225 : // Caller is responsible for closing fd on error.
226 2650 : static std::error_code set_fd_options(int fd) noexcept
227 : {
228 2650 : int flags = ::fcntl(fd, F_GETFL, 0);
229 2650 : if (flags == -1)
230 2 : return make_err(errno);
231 2648 : if (::fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1)
232 2 : return make_err(errno);
233 2646 : if (::fcntl(fd, F_SETFD, FD_CLOEXEC) == -1)
234 2 : return make_err(errno);
235 :
236 2644 : if (fd >= FD_SETSIZE)
237 2 : return make_err(EMFILE);
238 :
239 : #ifdef SO_NOSIGPIPE
240 : // MSG_NOSIGNAL is not universal across the platforms this
241 : // portable backend covers, and the write() the fast path falls
242 : // back to there takes no flag at all; SO_NOSIGPIPE is the
243 : // per-descriptor guard that covers both. Treat failure as fatal,
244 : // matching the kqueue backend. Caller closes fd on error.
245 : {
246 : int one = 1;
247 : if (::setsockopt(fd, SOL_SOCKET, SO_NOSIGPIPE, &one, sizeof(one)) !=
248 : 0)
249 : return make_err(errno);
250 : }
251 : #endif
252 :
253 2642 : return {};
254 : }
255 :
256 : // Apply protocol-specific options after socket creation.
257 : // For IP sockets, sets IPV6_V6ONLY on AF_INET6 (best-effort).
258 2265 : static std::error_code configure_ip_socket(int fd, int family) noexcept
259 : {
260 2265 : if (family == AF_INET6)
261 : {
262 23 : int one = 1;
263 : std::ignore =
264 23 : ::setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &one, sizeof(one));
265 : }
266 :
267 2265 : return set_fd_options(fd);
268 : }
269 :
270 : // Apply protocol-specific options for acceptor sockets.
271 : // For IP acceptors, sets IPV6_V6ONLY=0 (dual-stack, best-effort).
272 276 : static std::error_code configure_ip_acceptor(int fd, int family) noexcept
273 : {
274 276 : if (family == AF_INET6)
275 : {
276 11 : int val = 0;
277 : std::ignore =
278 11 : ::setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &val, sizeof(val));
279 : }
280 :
281 276 : return set_fd_options(fd);
282 : }
283 :
284 : // Apply options for local (unix) sockets.
285 109 : static std::error_code configure_local_socket(int fd) noexcept
286 : {
287 109 : return set_fd_options(fd);
288 : }
289 :
290 : // Non-mutating validation for fds adopted via assign(). Select's
291 : // reactor cannot handle fds above FD_SETSIZE, so reject them up
292 : // front instead of letting FD_SET clobber unrelated memory.
293 155 : static std::error_code validate_assigned_fd(int fd) noexcept
294 : {
295 155 : if (fd >= FD_SETSIZE)
296 2 : return make_err(EMFILE);
297 153 : return {};
298 : }
299 : };
300 :
301 : } // namespace boost::corosio::detail
302 :
303 : #endif // BOOST_COROSIO_HAS_SELECT
304 :
305 : #endif // BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_TRAITS_HPP
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