1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
use std::net::SocketAddr;
use std::os::fd::RawFd;
use std::sync::Arc;
use std::sync::atomic::AtomicBool;
use crossbeam_channel::Sender;
/// Configuration for the centralized acceptor thread.
pub struct AcceptorConfig {
/// The listening socket fd.
pub listen_fd: RawFd,
/// Per-worker channels to send accepted (fd, peer_addr) pairs.
pub worker_channels: Vec<Sender<(RawFd, SocketAddr)>>,
/// Per-worker eventfds to wake io_uring.
pub worker_eventfds: Vec<RawFd>,
/// Shared flag set by ShutdownHandle to signal the acceptor to stop.
#[allow(dead_code)] // stored for future use; acceptor currently uses channel disconnect
pub shutdown_flag: Arc<AtomicBool>,
/// Whether to set TCP_NODELAY on accepted connections.
pub tcp_nodelay: bool,
/// Whether to set SO_TIMESTAMPING on accepted connections.
#[cfg(feature = "timestamps")]
pub timestamps: bool,
}
/// Run the acceptor loop. Terminates when all channels disconnect.
///
/// Accepts connections via blocking `accept4` and distributes raw fds
/// to workers round-robin, waking each worker via eventfd.
pub fn run_acceptor(config: AcceptorConfig) {
let num_workers = config.worker_channels.len();
if num_workers == 0 {
return;
}
let mut next_worker = 0usize;
let mut addr_storage: libc::sockaddr_storage = unsafe { std::mem::zeroed() };
let mut alive = vec![true; num_workers];
let mut alive_count = num_workers;
loop {
let mut addr_len: libc::socklen_t =
std::mem::size_of::<libc::sockaddr_storage>() as libc::socklen_t;
let fd = unsafe {
libc::accept4(
config.listen_fd,
&mut addr_storage as *mut _ as *mut libc::sockaddr,
&mut addr_len,
libc::SOCK_NONBLOCK | libc::SOCK_CLOEXEC,
)
};
if fd < 0 {
let err = std::io::Error::last_os_error();
match err.raw_os_error() {
Some(libc::EINTR) => continue,
Some(libc::EMFILE) | Some(libc::ENFILE) => {
// Too many open files — back off briefly.
std::thread::sleep(std::time::Duration::from_millis(10));
continue;
}
Some(libc::ECONNABORTED) | Some(libc::ECONNRESET) | Some(libc::EPERM) => {
// Connection reset before accept completed, or blocked by
// firewall — retry immediately.
continue;
}
_ => {
// Fatal accept error or listen fd closed.
return;
}
}
}
// Set TCP_NODELAY if configured (skip for Unix domain sockets).
if config.tcp_nodelay && addr_storage.ss_family != libc::AF_UNIX as libc::sa_family_t {
let optval: libc::c_int = 1;
unsafe {
libc::setsockopt(
fd,
libc::IPPROTO_TCP,
libc::TCP_NODELAY,
&optval as *const _ as *const libc::c_void,
std::mem::size_of::<libc::c_int>() as libc::socklen_t,
);
}
}
// Set SO_TIMESTAMPING for kernel-level RX timestamps.
#[cfg(feature = "timestamps")]
if config.timestamps {
let flags: libc::c_int = (libc::SOF_TIMESTAMPING_SOFTWARE
| libc::SOF_TIMESTAMPING_RX_SOFTWARE)
as libc::c_int;
unsafe {
libc::setsockopt(
fd,
libc::SOL_SOCKET,
libc::SO_TIMESTAMPING,
&flags as *const _ as *const libc::c_void,
std::mem::size_of::<libc::c_int>() as libc::socklen_t,
);
}
}
// Parse peer address from the sockaddr_storage filled by accept4.
let peer_addr = sockaddr_to_socket_addr(&addr_storage)
.unwrap_or_else(|| SocketAddr::from(([0, 0, 0, 0], 0)));
// Round-robin pick a live worker. Try up to num_workers times.
let mut sent = false;
for _ in 0..num_workers {
let worker_idx = next_worker % num_workers;
next_worker = next_worker.wrapping_add(1);
if !alive[worker_idx] {
continue;
}
if config.worker_channels[worker_idx]
.send((fd, peer_addr))
.is_err()
{
// Worker has exited — mark dead.
alive[worker_idx] = false;
alive_count -= 1;
if alive_count == 0 {
unsafe {
libc::close(fd);
}
return;
}
continue;
}
// Wake the worker's io_uring via eventfd.
let val: u64 = 1;
unsafe {
libc::write(
config.worker_eventfds[worker_idx],
&val as *const u64 as *const libc::c_void,
8,
);
}
sent = true;
break;
}
if !sent {
// All workers dead.
unsafe {
libc::close(fd);
}
return;
}
}
}
/// Convert a `sockaddr_storage` (from accept4) to a Rust `SocketAddr`.
fn sockaddr_to_socket_addr(storage: &libc::sockaddr_storage) -> Option<SocketAddr> {
match storage.ss_family as libc::c_int {
libc::AF_INET => {
let sa = unsafe { &*(storage as *const _ as *const libc::sockaddr_in) };
let ip = std::net::Ipv4Addr::from(u32::from_be(sa.sin_addr.s_addr));
let port = u16::from_be(sa.sin_port);
Some(SocketAddr::from((ip, port)))
}
libc::AF_INET6 => {
let sa = unsafe { &*(storage as *const _ as *const libc::sockaddr_in6) };
let ip = std::net::Ipv6Addr::from(sa.sin6_addr.s6_addr);
let port = u16::from_be(sa.sin6_port);
Some(SocketAddr::from((ip, port)))
}
_ => None,
}
}