nloop.c

/*
 * uloop - event loop implementation
 *
 * Copyright (C) 2010-2016 Felix Fietkau <nbd@openwrt.org>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <stdbool.h>
#include <signal.h>

#include <sys/types.h>
#include <sys/epoll.h>

#include "nloop.h"

#ifndef ARRAY_SIZE
#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
#endif
#define ULOOP_MAX_EVENTS 10

/**
 * FIXME: uClibc < 0.9.30.3 does not define EPOLLRDHUP for Linux >= 2.6.17
 */
#ifndef EPOLLRDHUP
#define EPOLLRDHUP 0x2000
#endif

struct uloop_fd_event {
	struct uloop_fd *fd;
	unsigned int events;
};

struct uloop_fd_stack {
	struct uloop_fd_stack *next;
	struct uloop_fd *fd;
	unsigned int events;
};

static struct uloop_fd_stack *fd_stack = NULL;

static int poll_fd = -1;
bool uloop_cancelled = false;
static int uloop_status = 0;

static struct uloop_fd_event cur_fds[ULOOP_MAX_EVENTS];
static int cur_fd, cur_nfds;

int uloop_fd_add(struct uloop_fd *sock, unsigned int flags);

static int uloop_init_pollfd(void)
{
	if (poll_fd >= 0)
		return 0;

	poll_fd = epoll_create(32);
	if (poll_fd < 0)
		return -1;

	fcntl(poll_fd, F_SETFD, fcntl(poll_fd, F_GETFD) | FD_CLOEXEC);
	return 0;
}

static int register_poll(struct uloop_fd *fd, unsigned int flags)
{
	struct epoll_event ev;
	int op = fd->registered ? EPOLL_CTL_MOD : EPOLL_CTL_ADD;

	memset(&ev, 0, sizeof(struct epoll_event));

	if (flags & ULOOP_READ)
		ev.events |= EPOLLIN | EPOLLRDHUP;

	if (flags & ULOOP_WRITE)
		ev.events |= EPOLLOUT;

	if (flags & ULOOP_EDGE_TRIGGER)
		ev.events |= EPOLLET;

	ev.data.ptr = fd;
	fd->flags = flags;

	return epoll_ctl(poll_fd, op, fd->fd, &ev);
}

static struct epoll_event events[ULOOP_MAX_EVENTS];

static int __uloop_fd_delete(struct uloop_fd *sock)
{
	sock->flags = 0;
	return epoll_ctl(poll_fd, EPOLL_CTL_DEL, sock->fd, 0);
}

static int uloop_fetch_events(int timeout)
{
	int n, nfds;

	nfds = epoll_wait(poll_fd, events, ARRAY_SIZE(events), timeout);
	for (n = 0; n < nfds; ++n) {
		struct uloop_fd_event *cur = &cur_fds[n];
		struct uloop_fd *u = events[n].data.ptr;
		unsigned int ev = 0;

		cur->fd = u;
		if (!u)
			continue;

		if (events[n].events & (EPOLLERR|EPOLLHUP)) {
			u->error = true;
			if (!(u->flags & ULOOP_ERROR_CB))
				uloop_fd_delete(u);
		}

		if(!(events[n].events & (EPOLLRDHUP|EPOLLIN|EPOLLOUT|EPOLLERR|EPOLLHUP))) {
			cur->fd = NULL;
			continue;
		}

		if(events[n].events & EPOLLRDHUP)
			u->eof = true;

		if(events[n].events & EPOLLIN)
			ev |= ULOOP_READ;

		if(events[n].events & EPOLLOUT)
			ev |= ULOOP_WRITE;

		cur->events = ev;
	}

	return nfds;
}

static bool uloop_fd_stack_event(struct uloop_fd *fd, int events)
{
	struct uloop_fd_stack *cur;

	/*
	 * Do not buffer events for level-triggered fds, they will keep firing.
	 * Caller needs to take care of recursion issues.
	 */
	if (!(fd->flags & ULOOP_EDGE_TRIGGER))
		return false;

	for (cur = fd_stack; cur; cur = cur->next) {
		if (cur->fd != fd)
			continue;

		if (events < 0)
			cur->fd = NULL;
		else
			cur->events |= events | ULOOP_EVENT_BUFFERED;

		return true;
	}

	return false;
}

static void uloop_run_events(int timeout)
{
	struct uloop_fd_event *cur;
	struct uloop_fd *fd;

	if (!cur_nfds) {
		cur_fd = 0;
		cur_nfds = uloop_fetch_events(timeout);
		if (cur_nfds < 0)
			cur_nfds = 0;
	}

	while (cur_nfds > 0) {
		struct uloop_fd_stack stack_cur;
		unsigned int events;

		cur = &cur_fds[cur_fd++];
		cur_nfds--;

		fd = cur->fd;
		events = cur->events;
		if (!fd)
			continue;

		if (!fd->cb)
			continue;

		if (uloop_fd_stack_event(fd, cur->events))
			continue;

		stack_cur.next = fd_stack;
		stack_cur.fd = fd;
		fd_stack = &stack_cur;
		do {
			stack_cur.events = 0;
			fd->cb(fd, events);
			events = stack_cur.events & ULOOP_EVENT_MASK;
		} while (stack_cur.fd && events);
		fd_stack = stack_cur.next;

		return;
	}
}

int uloop_fd_add(struct uloop_fd *sock, unsigned int flags)
{
	unsigned int fl;
	int ret;

	if (!(flags & (ULOOP_READ | ULOOP_WRITE)))
		return uloop_fd_delete(sock);

	if (!sock->registered && !(flags & ULOOP_BLOCKING)) {
		fl = fcntl(sock->fd, F_GETFL, 0);
		fl |= O_NONBLOCK;
		fcntl(sock->fd, F_SETFL, fl);
	}

	ret = register_poll(sock, flags);
	if (ret < 0)
		goto out;

	sock->registered = true;
	sock->eof = false;
	sock->error = false;

out:
	return ret;
}

int uloop_fd_delete(struct uloop_fd *fd)
{
	int i;

	for (i = 0; i < cur_nfds; i++) {
		if (cur_fds[cur_fd + i].fd != fd)
			continue;

		cur_fds[cur_fd + i].fd = NULL;
	}

	if (!fd->registered)
		return 0;

	fd->registered = false;
	uloop_fd_stack_event(fd, -1);
	return __uloop_fd_delete(fd);
}

static void uloop_handle_sigint(int signo)
{
	uloop_status = signo;
	uloop_cancelled = true;
}

static void uloop_install_handler(int signum, void (*handler)(int), struct sigaction* old, bool add)
{
	struct sigaction s;
	struct sigaction *act;

	act = NULL;
	sigaction(signum, NULL, &s);

	if (add) {
		if (s.sa_handler == SIG_DFL) { /* Do not override existing custom signal handlers */
			memcpy(old, &s, sizeof(struct sigaction));
			s.sa_handler = handler;
			s.sa_flags = 0;
			act = &s;
		}
	}
	else if (s.sa_handler == handler) { /* Do not restore if someone modified our handler */
			act = old;
	}

	if (act != NULL)
		sigaction(signum, act, NULL);
}

static void uloop_setup_signals(bool add)
{
	static struct sigaction old_sigint, old_sigterm;
	uloop_install_handler(SIGINT, uloop_handle_sigint, &old_sigint, add);
	uloop_install_handler(SIGTERM, uloop_handle_sigint, &old_sigterm, add);
}

int uloop_init(void)
{
	if (uloop_init_pollfd() < 0)
		return -1;
	uloop_setup_signals(true);
	return 0;
}

int uloop_run(void)
{
	uloop_status = 0;
	uloop_cancelled = false;
	while (!uloop_cancelled) uloop_run_events(-1);
	return uloop_status;
}

void uloop_done(void)
{
	uloop_setup_signals(false);
	if (poll_fd >= 0) {
		close(poll_fd);
		poll_fd = -1;
	}
}