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#define LINUX 1
#define NUM_SOCKETS 1
#define NUM_WORKERS 8
#define _GNU_SOURCE
#include <aio.h> /* for struct aiocb, aio_read(), aio_write(), aio_error(), aio_return(), SIGEV_SIGNAL */
#include <arpa/inet.h> /* for htons() */
#include <errno.h> /* for errno, EAGAIN, EWOULDBLOCK, EINPROGRESS, EINVAL */
#include <error.h> /* for error() */
#include <netinet/in.h> /* for struct sockaddr_in */
#include <signal.h> /* for siginfo_t, struct sigaction, sigaction(), SIGRTMIN, SIGRTMAX, SA_SIGINFO */
#include <stdlib.h> /* for shutdown(), SHUT_RD, SHUT_WR, SHUT_RDWR */
#include <string.h> /* for memset() */
#include <sys/socket.h> /* for struct sockaddr, socket(), SOCK_* flags, setsockopt(), SOL_SOCKET, SO_REUSEADDR, bind(), listen(), accept() */
#if LINUX
# include <fcntl.h> /* for fcntl(), F_SETFL, O_ASYNC, F_SETSIG */
#endif
#include "netio.h"
#include "coroutine.h"
/* I found the following post to be very helpful when writing this:
* http://davmac.org/davpage/linux/async-io.html */
static int sigs_allocated = 0;
static int sig_io = 0;
#if LINUX
static int sig_accept = 0;
#endif
struct netio_socket {
int fd;
#if LINUX
cid_t accept_waiters[NUM_WORKERS];
#endif
};
static struct netio_socket socket_table[NUM_SOCKETS] = {0};
static void handle_sig_io(int sig __attribute__ ((unused)), siginfo_t *info, void *ucontext __attribute__ ((unused))) {
cr_unpause((cid_t)info->si_value.sival_int);
}
#if LINUX
static void handle_sig_accept(int sig __attribute__ ((unused)), siginfo_t *info, void *ucontext __attribute__ ((unused))) {
struct netio_socket *sock = NULL;
for (int i = 0; sock == NULL && i < NUM_SOCKETS; i++)
if (info->si_fd == socket_table[i].fd)
sock = &socket_table[i];
if (!sock)
return;
for (int i = 0; i < NUM_WORKERS; i++)
if (sock->accept_waiters[i] > 0) {
cr_unpause(sock->accept_waiters[i]);
sock->accept_waiters[i] = 0;
return;
}
}
#endif
static void _netio_init(void) {
struct sigaction action;
if (sig_io)
return;
sig_io = SIGRTMIN + (sigs_allocated++);
if (sig_io > SIGRTMAX)
error(1, 0, "SIGRTMAX exceeded");
memset(&action, 0, sizeof(action));
action.sa_flags = SA_SIGINFO;
action.sa_sigaction = handle_sig_io;
if (sigaction(sig_io, &action, NULL) < 0)
error(1, errno, "sigaction");
#if LINUX
sig_accept = SIGRTMIN + (sigs_allocated++);
if (sig_accept > SIGRTMAX)
error(1, 0, "SIGRTMAX exceeded");
memset(&action, 0, sizeof(action));
action.sa_flags = SA_SIGINFO;
action.sa_sigaction = handle_sig_accept;
if (sigaction(sig_accept, &action, NULL) < 0)
error(1, errno, "sigaction");
#endif
}
int netio_listen(uint16_t port) {
int handle;
struct netio_socket *sock;
union {
struct sockaddr_in in;
struct sockaddr gen;
} addr;
_netio_init();
/* Allocate a handle out of socket_table. */
handle = -1;
for (int i = 0; handle < 0 && i < NUM_SOCKETS; i++)
if (socket_table[i].fd == 0)
handle = i;
if (handle < 0)
error(1, 0, "NUM_SOCKETS exceeded");
sock = &socket_table[handle];
/* Bind the socket. */
memset(&addr, 0, sizeof addr);
addr.in.sin_family = AF_INET;
addr.in.sin_port = htons(port);
sock->fd = socket(AF_INET, SOCK_STREAM | (LINUX ? 0 : SOCK_NONBLOCK), 0);
if (sock->fd < 0)
error(1, errno, "socket");
if (setsockopt(sock->fd, SOL_SOCKET, SO_REUSEADDR, &(int){1}, sizeof(int)) < 0)
error(1, errno, "setsockopt");
#if LINUX
if (fcntl(sock->fd, F_SETFL, O_ASYNC) < 0)
error(1, errno, "fcntl(F_SETFL)");
if (fcntl(sock->fd, F_SETSIG, sig_accept) < 0)
error(1, errno, "fcntl(F_SETSIG)");
#endif
if (bind(sock->fd, &addr.gen, sizeof addr) < 0)
error(1, errno, "bind");
if (listen(sock->fd, NUM_WORKERS) < 0)
error(1, errno, "listen");
/* Return. */
return handle;
}
int netio_accept(int sock) {
#if LINUX
int conn;
for (int i = 0; i < NUM_WORKERS; i++)
if (socket_table[sock].accept_waiters[i] == 0) {
socket_table[sock].accept_waiters[i] = cr_getcid();
break;
}
cr_pause_and_yield();
conn = accept(socket_table[sock].fd, NULL, NULL);
return conn < 0 ? -errno : conn;
#else
/* AFAICT in pure POSIX there's no good way to do this that
* isn't just busy-polling. */
for (;;) {
int conn = accept(socket_table[sock].fd, NULL, NULL);
if (conn < 0) {
if (errno == EAGAIN || errno == EWOULDBLOCK) {
cr_yield();
continue;
}
return -errno;
}
return conn;
}
#endif
}
size_t netio_read(int conn, void *buf, size_t count) {
int r;
struct aiocb ctl_block = {
.aio_fildes = conn,
.aio_buf = buf,
.aio_nbytes = count,
.aio_sigevent = {
.sigev_notify = SIGEV_SIGNAL,
.sigev_signo = sig_io,
.sigev_value = {
.sival_int = (int)cr_getcid(),
},
},
};
if (aio_read(&ctl_block) < 0)
return -errno;
while ((r = aio_error(&ctl_block)) == EINPROGRESS)
cr_pause_and_yield();
return r ? -abs(r) : aio_return(&ctl_block);
}
size_t netio_write(int conn, void *buf, size_t count) {
int r;
struct aiocb ctl_block = {
.aio_fildes = conn,
.aio_buf = buf,
.aio_nbytes = count,
.aio_sigevent = {
.sigev_notify = SIGEV_SIGNAL,
.sigev_signo = sig_io,
.sigev_value = {
.sival_int = (int)cr_getcid(),
},
},
};
if (aio_write(&ctl_block) < 0)
return -errno;
while ((r = aio_error(&ctl_block)) == EINPROGRESS)
cr_pause_and_yield();
return r ? -abs(r) : aio_return(&ctl_block);
}
int netio_close(int conn, bool rd, bool wr) {
int how;
if (rd && wr)
how = SHUT_RDWR;
else if (rd && !wr)
how = SHUT_RD;
else if (!rd && wr)
how = SHUT_WR;
else
return -EINVAL;
return shutdown(conn, how) ? -errno : 0;
}
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