include/boost/corosio/native/detail/epoll/epoll_traits.hpp

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epoll_traits.hpp

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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_EPOLL_EPOLL_TRAITS_HPP
11		#define BOOST_COROSIO_NATIVE_DETAIL_EPOLL_EPOLL_TRAITS_HPP
12
13		#include <boost/corosio/detail/platform.hpp>
14
15		#if BOOST_COROSIO_HAS_EPOLL
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 <netinet/in.h>
24		#include <sys/socket.h>
25
26		/* epoll backend traits.
27
28		Captures the platform-specific behavior of the Linux epoll backend:
29		atomic SOCK_NONBLOCK\|SOCK_CLOEXEC on socket(), accept4() for
30		accepted connections, and sendmsg(MSG_NOSIGNAL) for writes.
31		*/
32
33		namespace boost::corosio::detail {
34
35		class epoll_scheduler;
36		struct descriptor_state;
37
38		struct epoll_traits
39		{
40		using scheduler_type = epoll_scheduler;
41		using desc_state_type = descriptor_state;
42
43		static constexpr bool needs_write_notification = false;
44
45		/// No extra per-socket state or lifecycle hooks needed for epoll.
46		struct stream_socket_hook
47		{
48	32x	std::error_code on_set_option(
49		int fd, int level, int optname,
50		void const* data, std::size_t size) noexcept
51		{
52	32x	if (::setsockopt(
53		fd, level, optname, data,
54	32x	static_cast<socklen_t>(size)) != 0)
55	✗	return make_err(errno);
56	32x	return {};
57		}
58	✗	static void pre_shutdown(int) noexcept {}
59	8967x	static void pre_destroy(int) noexcept {}
60		};
61
62		struct write_policy
63		{
64	93264x	static ssize_t write(int fd, iovec* iovecs, int count) noexcept
65		{
66	93264x	msghdr msg{};
67	93264x	msg.msg_iov = iovecs;
68	93264x	msg.msg_iovlen = static_cast<std::size_t>(count);
69
70		ssize_t n;
71		do
72		{
73	93264x	n = ::sendmsg(fd, &msg, MSG_NOSIGNAL);
74		}
75	93264x	while (n < 0 && errno == EINTR);
76	93264x	return n;
77		}
78		};
79
80		struct accept_policy
81		{
82	5942x	static int do_accept(
83		int fd, sockaddr_storage& peer, socklen_t& addrlen) noexcept
84		{
85	5942x	addrlen = sizeof(peer);
86		int new_fd;
87		do
88		{
89	5942x	new_fd = ::accept4(
90		fd, reinterpret_cast<sockaddr*>(&peer), &addrlen,
91		SOCK_NONBLOCK \| SOCK_CLOEXEC);
92		}
93	5942x	while (new_fd < 0 && errno == EINTR);
94	5942x	return new_fd;
95		}
96		};
97
98		/// Create a nonblocking, close-on-exec socket using Linux's atomic flags.
99	3131x	static int create_socket(int family, int type, int protocol) noexcept
100		{
101	3131x	return ::socket(family, type \| SOCK_NONBLOCK \| SOCK_CLOEXEC, protocol);
102		}
103
104		/// Apply protocol-specific options after socket creation.
105		/// For IP sockets, sets IPV6_V6ONLY on AF_INET6.
106		static std::error_code
107	3028x	configure_ip_socket(int fd, int family) noexcept
108		{
109	3028x	if (family == AF_INET6)
110		{
111	13x	int one = 1;
112	13x	if (::setsockopt(
113	13x	fd, IPPROTO_IPV6, IPV6_V6ONLY, &one, sizeof(one)) != 0)
114	✗	return make_err(errno);
115		}
116	3028x	return {};
117		}
118
119		/// Apply protocol-specific options for acceptor sockets.
120		/// For IP acceptors, sets IPV6_V6ONLY=0 (dual-stack).
121		static std::error_code
122	83x	configure_ip_acceptor(int fd, int family) noexcept
123		{
124	83x	if (family == AF_INET6)
125		{
126	8x	int val = 0;
127	8x	if (::setsockopt(
128	8x	fd, IPPROTO_IPV6, IPV6_V6ONLY, &val, sizeof(val)) != 0)
129	✗	return make_err(errno);
130		}
131	83x	return {};
132		}
133
134		/// No extra configuration needed for local (unix) sockets on epoll.
135		static std::error_code
136	34x	configure_local_socket(int /fd/) noexcept
137		{
138	34x	return {};
139		}
140		};
141
142		} // namespace boost::corosio::detail
143
144		#endif // BOOST_COROSIO_HAS_EPOLL
145
146		#endif // BOOST_COROSIO_NATIVE_DETAIL_EPOLL_EPOLL_TRAITS_HPP
147