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 :
22 : #include <errno.h>
23 : #include <fcntl.h>
24 : #include <netinet/in.h>
25 : #include <sys/select.h>
26 : #include <sys/socket.h>
27 : #include <unistd.h>
28 :
29 : /* select backend traits.
30 :
31 : Captures the platform-specific behavior of the portable select() backend:
32 : manual fcntl for O_NONBLOCK/FD_CLOEXEC, FD_SETSIZE validation,
33 : conditional SO_NOSIGPIPE, sendmsg(MSG_NOSIGNAL) where available,
34 : and accept()+fcntl for accepted connections.
35 : */
36 :
37 : namespace boost::corosio::detail {
38 :
39 : class select_scheduler;
40 :
41 : struct select_traits
42 : {
43 : using scheduler_type = select_scheduler;
44 : using desc_state_type = reactor_descriptor_state;
45 :
46 : static constexpr bool needs_write_notification = true;
47 :
48 : // No extra per-socket state or lifecycle hooks needed for select.
49 : struct stream_socket_hook
50 : {
51 HIT 28 : std::error_code on_set_option(
52 : int fd, int level, int optname,
53 : void const* data, std::size_t size) noexcept
54 : {
55 28 : if (::setsockopt(
56 : fd, level, optname, data,
57 28 : static_cast<socklen_t>(size)) != 0)
58 MIS 0 : return make_err(errno);
59 HIT 28 : return {};
60 : }
61 14562 : static void pre_shutdown(int) noexcept {}
62 4828 : static void pre_destroy(int) noexcept {}
63 : };
64 :
65 : struct write_policy
66 : {
67 MIS 0 : static ssize_t write(int fd, iovec* iovecs, int count) noexcept
68 : {
69 0 : msghdr msg{};
70 0 : msg.msg_iov = iovecs;
71 0 : msg.msg_iovlen = static_cast<std::size_t>(count);
72 :
73 : #ifdef MSG_NOSIGNAL
74 0 : constexpr int send_flags = MSG_NOSIGNAL;
75 : #else
76 : constexpr int send_flags = 0;
77 : #endif
78 :
79 : ssize_t n;
80 : do
81 : {
82 0 : n = ::sendmsg(fd, &msg, send_flags);
83 : }
84 0 : while (n < 0 && errno == EINTR);
85 0 : return n;
86 : }
87 :
88 : // Single-buffer fast path. Where MSG_NOSIGNAL exists we use
89 : // send() to suppress SIGPIPE inline; otherwise fall back to
90 : // write() and rely on the SO_NOSIGPIPE set in accept_policy
91 : // and set_fd_options.
92 HIT 127774 : static ssize_t write_one(
93 : int fd, void const* data, std::size_t size) noexcept
94 : {
95 : ssize_t n;
96 : do
97 : {
98 : #ifdef MSG_NOSIGNAL
99 127774 : n = ::send(fd, data, size, MSG_NOSIGNAL);
100 : #else
101 : n = ::write(fd, data, size);
102 : #endif
103 : }
104 127774 : while (n < 0 && errno == EINTR);
105 127774 : return n;
106 : }
107 : };
108 :
109 : struct accept_policy
110 : {
111 3198 : static int do_accept(
112 : int fd, sockaddr_storage& peer, socklen_t& addrlen) noexcept
113 : {
114 3198 : addrlen = sizeof(peer);
115 : int new_fd;
116 : do
117 : {
118 3198 : new_fd = ::accept(
119 : fd, reinterpret_cast<sockaddr*>(&peer), &addrlen);
120 : }
121 3198 : while (new_fd < 0 && errno == EINTR);
122 :
123 3198 : if (new_fd < 0)
124 1599 : return new_fd;
125 :
126 1599 : if (new_fd >= FD_SETSIZE)
127 : {
128 MIS 0 : ::close(new_fd);
129 0 : errno = EINVAL;
130 0 : return -1;
131 : }
132 :
133 HIT 1599 : int flags = ::fcntl(new_fd, F_GETFL, 0);
134 1599 : if (flags == -1)
135 : {
136 MIS 0 : int err = errno;
137 0 : ::close(new_fd);
138 0 : errno = err;
139 0 : return -1;
140 : }
141 :
142 HIT 1599 : if (::fcntl(new_fd, F_SETFL, flags | O_NONBLOCK) == -1)
143 : {
144 MIS 0 : int err = errno;
145 0 : ::close(new_fd);
146 0 : errno = err;
147 0 : return -1;
148 : }
149 :
150 HIT 1599 : if (::fcntl(new_fd, F_SETFD, FD_CLOEXEC) == -1)
151 : {
152 MIS 0 : int err = errno;
153 0 : ::close(new_fd);
154 0 : errno = err;
155 0 : return -1;
156 : }
157 :
158 : #ifdef SO_NOSIGPIPE
159 : // Best-effort: SO_NOSIGPIPE is a safety net; write paths
160 : // also use MSG_NOSIGNAL where available. Failure here
161 : // should not prevent the accepted connection from being used.
162 : int one = 1;
163 : (void)::setsockopt(
164 : new_fd, SOL_SOCKET, SO_NOSIGPIPE, &one, sizeof(one));
165 : #endif
166 :
167 HIT 1599 : return new_fd;
168 : }
169 : };
170 :
171 : // Create a plain socket (no atomic flags -- select is POSIX-portable).
172 1759 : static int create_socket(int family, int type, int protocol) noexcept
173 : {
174 1759 : return ::socket(family, type, protocol);
175 : }
176 :
177 : // Set O_NONBLOCK, FD_CLOEXEC; check FD_SETSIZE; optionally SO_NOSIGPIPE.
178 : // Caller is responsible for closing fd on error.
179 1759 : static std::error_code set_fd_options(int fd) noexcept
180 : {
181 1759 : int flags = ::fcntl(fd, F_GETFL, 0);
182 1759 : if (flags == -1)
183 MIS 0 : return make_err(errno);
184 HIT 1759 : if (::fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1)
185 MIS 0 : return make_err(errno);
186 HIT 1759 : if (::fcntl(fd, F_SETFD, FD_CLOEXEC) == -1)
187 MIS 0 : return make_err(errno);
188 :
189 HIT 1759 : if (fd >= FD_SETSIZE)
190 MIS 0 : return make_err(EMFILE);
191 :
192 : #ifdef SO_NOSIGPIPE
193 : // Best-effort: SO_NOSIGPIPE is a safety net; write paths
194 : // also use MSG_NOSIGNAL where available. Match develop's
195 : // predominant behavior of ignoring failures here rather
196 : // than failing socket creation.
197 : {
198 : int one = 1;
199 : (void)::setsockopt(
200 : fd, SOL_SOCKET, SO_NOSIGPIPE, &one, sizeof(one));
201 : }
202 : #endif
203 :
204 HIT 1759 : return {};
205 : }
206 :
207 : // Apply protocol-specific options after socket creation.
208 : // For IP sockets, sets IPV6_V6ONLY on AF_INET6 (best-effort).
209 : static std::error_code
210 1665 : configure_ip_socket(int fd, int family) noexcept
211 : {
212 1665 : if (family == AF_INET6)
213 : {
214 14 : int one = 1;
215 14 : (void)::setsockopt(
216 : fd, IPPROTO_IPV6, IPV6_V6ONLY, &one, sizeof(one));
217 : }
218 :
219 1665 : return set_fd_options(fd);
220 : }
221 :
222 : // Apply protocol-specific options for acceptor sockets.
223 : // For IP acceptors, sets IPV6_V6ONLY=0 (dual-stack, best-effort).
224 : static std::error_code
225 74 : configure_ip_acceptor(int fd, int family) noexcept
226 : {
227 74 : if (family == AF_INET6)
228 : {
229 9 : int val = 0;
230 9 : (void)::setsockopt(
231 : fd, IPPROTO_IPV6, IPV6_V6ONLY, &val, sizeof(val));
232 : }
233 :
234 74 : return set_fd_options(fd);
235 : }
236 :
237 : // Apply options for local (unix) sockets.
238 : static std::error_code
239 20 : configure_local_socket(int fd) noexcept
240 : {
241 20 : return set_fd_options(fd);
242 : }
243 :
244 : // Non-mutating validation for fds adopted via assign(). Select's
245 : // reactor cannot handle fds above FD_SETSIZE, so reject them up
246 : // front instead of letting FD_SET clobber unrelated memory.
247 : static std::error_code
248 14 : validate_assigned_fd(int fd) noexcept
249 : {
250 14 : if (fd >= FD_SETSIZE)
251 MIS 0 : return make_err(EMFILE);
252 HIT 14 : return {};
253 : }
254 : };
255 :
256 : } // namespace boost::corosio::detail
257 :
258 : #endif // BOOST_COROSIO_HAS_SELECT
259 :
260 : #endif // BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_TRAITS_HPP
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