include/boost/corosio/native/detail/kqueue/kqueue_traits.hpp

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kqueue_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_KQUEUE_KQUEUE_TRAITS_HPP
11			#define BOOST_COROSIO_NATIVE_DETAIL_KQUEUE_KQUEUE_TRAITS_HPP
12
13			#include <boost/corosio/detail/platform.hpp>
14
15			#if BOOST_COROSIO_HAS_KQUEUE
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/socket.h>
26			#include <sys/uio.h>
27			#include <unistd.h>
28
29			/* kqueue backend traits.
30
31			Captures the platform-specific behavior of the BSD/macOS kqueue backend:
32			manual fcntl for O_NONBLOCK/FD_CLOEXEC, mandatory SO_NOSIGPIPE (macOS
33			lacks MSG_NOSIGNAL), writev() for writes, and accept()+fcntl for
34			accepted connections.
35			*/
36
37			namespace boost::corosio::detail {
38
39			class kqueue_scheduler;
40
41			struct kqueue_traits
42			{
43			using scheduler_type = kqueue_scheduler;
44			using desc_state_type = reactor_descriptor_state;
45
46			static constexpr bool needs_write_notification = false;
47
48			// No per-socket state or lifecycle hooks: the stream socket hook is a
49			// plain setsockopt passthrough, like epoll/select. SO_LINGER in particular
50			// is passed through unmodified. An abortive close (SO_LINGER{on,0}) thus
51			// sends a RST, which the peer's kqueue reports as EV_EOF carrying
52			// ECONNRESET in fflags -- so the peer surfaces connection_reset rather than
53			// a graceful eof, consistent with the other backends (#304). A positive
54			// linger timeout is likewise honored, so close() with unsent data blocks
55			// up to that timeout, as POSIX specifies.
56			struct stream_socket_hook
57			{
58		1865x	std::error_code on_set_option(
59			int fd, int level, int optname,
60			void const* data, std::size_t size) noexcept
61			{
62	2/4 ✓ Branch 0 taken 1865 times. ✗ Branch 1 not taken. ✗ Branch 2 not taken. ✓ Branch 3 taken 1865 times.	1865x	if (::setsockopt(
63		1865x	fd, level, optname, data,
64		1865x	static_cast<socklen_t>(size)) != 0)
65		✗	return make_err(errno);
66		1865x	return {};
67		1865x	}
68		44435x	static void pre_shutdown(int) noexcept {}
69		14745x	static void pre_destroy(int) noexcept {}
70			};
71
72			struct write_policy
73			{
74		498x	static ssize_t write(int fd, iovec* iovecs, int count) noexcept
75			{
76			ssize_t n;
77		498x	do
78			{
79	1/2 ✓ Branch 0 taken 498 times. ✗ Branch 1 not taken.	498x	n = ::writev(fd, iovecs, count);
80		996x	}
81	3/4 ✓ Branch 0 taken 3 times. ✓ Branch 1 taken 495 times. ✓ Branch 2 taken 3 times. ✗ Branch 3 not taken.	498x	while (n < 0 && errno == EINTR);
82		498x	return n;
83			}
84
85			// Single-buffer fast path. macOS lacks MSG_NOSIGNAL; SIGPIPE is
86			// suppressed by the mandatory SO_NOSIGPIPE set in accept_policy
87			// and set_fd_options, so plain write() is safe here.
88		374584x	static ssize_t write_one(
89			int fd, void const* data, std::size_t size) noexcept
90			{
91			ssize_t n;
92		374584x	do
93			{
94	1/2 ✓ Branch 0 taken 374584 times. ✗ Branch 1 not taken.	374584x	n = ::write(fd, data, size);
95		749168x	}
96	3/4 ✓ Branch 0 taken 495 times. ✓ Branch 1 taken 374089 times. ✓ Branch 2 taken 495 times. ✗ Branch 3 not taken.	374584x	while (n < 0 && errno == EINTR);
97		374584x	return n;
98			}
99			};
100
101			struct accept_policy
102			{
103		9761x	static int do_accept(
104			int fd, sockaddr_storage& peer, socklen_t& addrlen) noexcept
105			{
106			int new_fd;
107		9761x	do
108			{
109		9761x	addrlen = sizeof(peer);
110	1/2 ✓ Branch 0 taken 9761 times. ✗ Branch 1 not taken.	9761x	new_fd = ::accept(
111		9761x	fd, reinterpret_cast<sockaddr*>(&peer), &addrlen);
112		19522x	}
113	3/4 ✓ Branch 0 taken 4889 times. ✓ Branch 1 taken 4872 times. ✓ Branch 2 taken 4889 times. ✗ Branch 3 not taken.	9761x	while (new_fd < 0 && errno == EINTR);
114
115	2/2 ✓ Branch 0 taken 4889 times. ✓ Branch 1 taken 4872 times.	9761x	if (new_fd < 0)
116		4889x	return new_fd;
117
118	1/2 ✓ Branch 0 taken 4872 times. ✗ Branch 1 not taken.	4872x	int flags = ::fcntl(new_fd, F_GETFL, 0);
119	2/4 ✓ Branch 0 taken 4872 times. ✗ Branch 1 not taken. ✓ Branch 2 taken 4872 times. ✗ Branch 3 not taken.	9744x	if (flags == -1 \|\|
120	1/2 ✓ Branch 0 taken 4872 times. ✗ Branch 1 not taken.	4872x	::fcntl(new_fd, F_SETFL, flags \| O_NONBLOCK) == -1)
121			{
122		✗	int err = errno;
123		✗	::close(new_fd);
124		✗	errno = err;
125		✗	return -1;
126			}
127
128	2/4 ✓ Branch 0 taken 4872 times. ✗ Branch 1 not taken. ✗ Branch 2 not taken. ✓ Branch 3 taken 4872 times.	4872x	if (::fcntl(new_fd, F_SETFD, FD_CLOEXEC) == -1)
129			{
130		✗	int err = errno;
131		✗	::close(new_fd);
132		✗	errno = err;
133		✗	return -1;
134			}
135
136			#ifndef BOOST_COROSIO_MRDOCS
137			// SO_NOSIGPIPE is mandatory on kqueue platforms (macOS lacks
138			// MSG_NOSIGNAL). Skipped under MRDOCS so the docs build can
139			// parse this header on Linux, where SO_NOSIGPIPE is absent.
140		4872x	int one = 1;
141	2/4 ✓ Branch 0 taken 4872 times. ✗ Branch 1 not taken. ✗ Branch 2 not taken. ✓ Branch 3 taken 4872 times.	4872x	if (::setsockopt(
142		4872x	new_fd, SOL_SOCKET, SO_NOSIGPIPE,
143		4872x	&one, sizeof(one)) == -1)
144			{
145		✗	int err = errno;
146		✗	::close(new_fd);
147		✗	errno = err;
148		✗	return -1;
149			}
150			#endif
151
152		4872x	return new_fd;
153		9761x	}
154			};
155
156			// Create a plain socket. Fd options are applied by configure_*().
157		6161x	static int create_socket(int family, int type, int protocol) noexcept
158			{
159	1/2 ✓ Branch 0 taken 6161 times. ✗ Branch 1 not taken.	6161x	return ::socket(family, type, protocol);
160			}
161
162			// Set O_NONBLOCK, FD_CLOEXEC, and SO_NOSIGPIPE on a new fd.
163			// Caller is responsible for closing fd on error.
164		6161x	static std::error_code set_fd_options(int fd) noexcept
165			{
166	1/2 ✓ Branch 0 taken 6161 times. ✗ Branch 1 not taken.	6161x	int flags = ::fcntl(fd, F_GETFL, 0);
167	1/2 ✗ Branch 0 not taken. ✓ Branch 1 taken 6161 times.	6161x	if (flags == -1)
168		✗	return make_err(errno);
169	2/4 ✓ Branch 0 taken 6161 times. ✗ Branch 1 not taken. ✗ Branch 2 not taken. ✓ Branch 3 taken 6161 times.	6161x	if (::fcntl(fd, F_SETFL, flags \| O_NONBLOCK) == -1)
170		✗	return make_err(errno);
171	2/4 ✓ Branch 0 taken 6161 times. ✗ Branch 1 not taken. ✗ Branch 2 not taken. ✓ Branch 3 taken 6161 times.	6161x	if (::fcntl(fd, F_SETFD, FD_CLOEXEC) == -1)
172		✗	return make_err(errno);
173
174			#ifndef BOOST_COROSIO_MRDOCS
175			// SO_NOSIGPIPE is mandatory on kqueue platforms (see accept_policy).
176		6161x	int one = 1;
177	2/4 ✓ Branch 0 taken 6161 times. ✗ Branch 1 not taken. ✗ Branch 2 not taken. ✓ Branch 3 taken 6161 times.	6161x	if (::setsockopt(fd, SOL_SOCKET, SO_NOSIGPIPE, &one, sizeof(one)) != 0)
178		✗	return make_err(errno);
179			#endif
180
181		6161x	return {};
182		6161x	}
183
184			// Apply protocol-specific options after socket creation.
185			// For IP sockets, sets IPV6_V6ONLY on AF_INET6 (best-effort).
186			static std::error_code
187		4995x	configure_ip_socket(int fd, int family) noexcept
188			{
189		4995x	auto ec = set_fd_options(fd);
190	1/2 ✗ Branch 0 not taken. ✓ Branch 1 taken 4995 times.	4995x	if (ec)
191		✗	return ec;
192
193	2/2 ✓ Branch 0 taken 4976 times. ✓ Branch 1 taken 19 times.	4995x	if (family == AF_INET6)
194			{
195		19x	int v6only = 1;
196	1/2 ✓ Branch 0 taken 19 times. ✗ Branch 1 not taken.	19x	(void)::setsockopt(
197		19x	fd, IPPROTO_IPV6, IPV6_V6ONLY,
198			&v6only, sizeof(v6only));
199		19x	}
200		4995x	return {};
201		4995x	}
202
203			// Apply protocol-specific options for acceptor sockets.
204			// For IP acceptors, sets IPV6_V6ONLY=0 (dual-stack, best-effort).
205			static std::error_code
206		1092x	configure_ip_acceptor(int fd, int family) noexcept
207			{
208		1092x	auto ec = set_fd_options(fd);
209	1/2 ✗ Branch 0 not taken. ✓ Branch 1 taken 1092 times.	1092x	if (ec)
210		✗	return ec;
211
212	2/2 ✓ Branch 0 taken 1082 times. ✓ Branch 1 taken 10 times.	1092x	if (family == AF_INET6)
213			{
214		10x	int val = 0;
215	1/2 ✓ Branch 0 taken 10 times. ✗ Branch 1 not taken.	10x	(void)::setsockopt(
216		10x	fd, IPPROTO_IPV6, IPV6_V6ONLY, &val, sizeof(val));
217		10x	}
218		1092x	return {};
219		1092x	}
220
221			// Apply options for local (unix) sockets.
222			static std::error_code
223		74x	configure_local_socket(int fd) noexcept
224			{
225		74x	return set_fd_options(fd);
226			}
227
228			// Non-mutating validation for fds adopted via assign(). Used when
229			// the caller retains fd ownership responsibility.
230			static std::error_code
231		76x	validate_assigned_fd(int /fd/) noexcept
232			{
233		76x	return {};
234			}
235			};
236
237			} // namespace boost::corosio::detail
238
239			#endif // BOOST_COROSIO_HAS_KQUEUE
240
241			#endif // BOOST_COROSIO_NATIVE_DETAIL_KQUEUE_KQUEUE_TRAITS_HPP
242