1/*	$NetBSD: poll.c,v 1.1.1.4 2021/04/07 02:43:13 christos Exp $	*/
2/*	$OpenBSD: poll.c,v 1.2 2002/06/25 15:50:15 mickey Exp $	*/
3
4/*
5 * Copyright 2000-2007 Niels Provos <provos@citi.umich.edu>
6 * Copyright 2007-2012 Niels Provos and Nick Mathewson
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. The name of the author may not be used to endorse or promote products
17 *    derived from this software without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
24 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30#include "event2/event-config.h"
31#include <sys/cdefs.h>
32__RCSID("$NetBSD: poll.c,v 1.1.1.4 2021/04/07 02:43:13 christos Exp $");
33#include "evconfig-private.h"
34
35#ifdef EVENT__HAVE_POLL
36
37#include <sys/types.h>
38#ifdef EVENT__HAVE_SYS_TIME_H
39#include <sys/time.h>
40#endif
41#include <sys/queue.h>
42#include <poll.h>
43#include <signal.h>
44#include <limits.h>
45#include <stdio.h>
46#include <stdlib.h>
47#include <string.h>
48#include <unistd.h>
49#include <errno.h>
50
51#include "event-internal.h"
52#include "evsignal-internal.h"
53#include "log-internal.h"
54#include "evmap-internal.h"
55#include "event2/thread.h"
56#include "evthread-internal.h"
57#include "time-internal.h"
58
59/* Since Linux 2.6.17, poll is able to report about peer half-closed connection
60   using special POLLRDHUP flag on a read event.
61*/
62#if !defined(POLLRDHUP)
63#define POLLRDHUP 0
64#define EARLY_CLOSE_IF_HAVE_RDHUP 0
65#else
66#define EARLY_CLOSE_IF_HAVE_RDHUP EV_FEATURE_EARLY_CLOSE
67#endif
68
69
70struct pollidx {
71	int idxplus1;
72};
73
74struct pollop {
75	int event_count;		/* Highest number alloc */
76	int nfds;			/* Highest number used */
77	int realloc_copy;		/* True iff we must realloc
78					 * event_set_copy */
79	struct pollfd *event_set;
80	struct pollfd *event_set_copy;
81};
82
83static void *poll_init(struct event_base *);
84static int poll_add(struct event_base *, int, short old, short events, void *idx);
85static int poll_del(struct event_base *, int, short old, short events, void *idx);
86static int poll_dispatch(struct event_base *, struct timeval *);
87static void poll_dealloc(struct event_base *);
88
89const struct eventop pollops = {
90	"poll",
91	poll_init,
92	poll_add,
93	poll_del,
94	poll_dispatch,
95	poll_dealloc,
96	1, /* need_reinit */
97	EV_FEATURE_FDS|EARLY_CLOSE_IF_HAVE_RDHUP,
98	sizeof(struct pollidx),
99};
100
101static void *
102poll_init(struct event_base *base)
103{
104	struct pollop *pollop;
105
106	if (!(pollop = mm_calloc(1, sizeof(struct pollop))))
107		return (NULL);
108
109	evsig_init_(base);
110
111	evutil_weakrand_seed_(&base->weakrand_seed, 0);
112
113	return (pollop);
114}
115
116#ifdef CHECK_INVARIANTS
117static void
118poll_check_ok(struct pollop *pop)
119{
120	int i, idx;
121	struct event *ev;
122
123	for (i = 0; i < pop->fd_count; ++i) {
124		idx = pop->idxplus1_by_fd[i]-1;
125		if (idx < 0)
126			continue;
127		EVUTIL_ASSERT(pop->event_set[idx].fd == i);
128	}
129	for (i = 0; i < pop->nfds; ++i) {
130		struct pollfd *pfd = &pop->event_set[i];
131		EVUTIL_ASSERT(pop->idxplus1_by_fd[pfd->fd] == i+1);
132	}
133}
134#else
135#define poll_check_ok(pop)
136#endif
137
138static int
139poll_dispatch(struct event_base *base, struct timeval *tv)
140{
141	int res, i, j, nfds;
142	long msec = -1;
143	struct pollop *pop = base->evbase;
144	struct pollfd *event_set;
145
146	poll_check_ok(pop);
147
148	nfds = pop->nfds;
149
150#ifndef EVENT__DISABLE_THREAD_SUPPORT
151	if (base->th_base_lock) {
152		/* If we're using this backend in a multithreaded setting,
153		 * then we need to work on a copy of event_set, so that we can
154		 * let other threads modify the main event_set while we're
155		 * polling. If we're not multithreaded, then we'll skip the
156		 * copy step here to save memory and time. */
157		if (pop->realloc_copy) {
158			struct pollfd *tmp = mm_realloc(pop->event_set_copy,
159			    pop->event_count * sizeof(struct pollfd));
160			if (tmp == NULL) {
161				event_warn("realloc");
162				return -1;
163			}
164			pop->event_set_copy = tmp;
165			pop->realloc_copy = 0;
166		}
167		memcpy(pop->event_set_copy, pop->event_set,
168		    sizeof(struct pollfd)*nfds);
169		event_set = pop->event_set_copy;
170	} else {
171		event_set = pop->event_set;
172	}
173#else
174	event_set = pop->event_set;
175#endif
176
177	if (tv != NULL) {
178		msec = evutil_tv_to_msec_(tv);
179		if (msec < 0 || msec > INT_MAX)
180			msec = INT_MAX;
181	}
182
183	EVBASE_RELEASE_LOCK(base, th_base_lock);
184
185	res = poll(event_set, nfds, msec);
186
187	EVBASE_ACQUIRE_LOCK(base, th_base_lock);
188
189	if (res == -1) {
190		if (errno != EINTR) {
191			event_warn("poll");
192			return (-1);
193		}
194
195		return (0);
196	}
197
198	event_debug(("%s: poll reports %d", __func__, res));
199
200	if (res == 0 || nfds == 0)
201		return (0);
202
203	i = evutil_weakrand_range_(&base->weakrand_seed, nfds);
204	for (j = 0; j < nfds; j++) {
205		int what;
206		if (++i == nfds)
207			i = 0;
208		what = event_set[i].revents;
209		if (!what)
210			continue;
211
212		res = 0;
213
214		/* If the file gets closed notify */
215		if (what & (POLLHUP|POLLERR|POLLNVAL))
216			what |= POLLIN|POLLOUT;
217		if (what & POLLIN)
218			res |= EV_READ;
219		if (what & POLLOUT)
220			res |= EV_WRITE;
221		if (what & POLLRDHUP)
222			res |= EV_CLOSED;
223		if (res == 0)
224			continue;
225
226		evmap_io_active_(base, event_set[i].fd, res);
227	}
228
229	return (0);
230}
231
232static int
233poll_add(struct event_base *base, int fd, short old, short events, void *idx_)
234{
235	struct pollop *pop = base->evbase;
236	struct pollfd *pfd = NULL;
237	struct pollidx *idx = idx_;
238	int i;
239
240	EVUTIL_ASSERT((events & EV_SIGNAL) == 0);
241	if (!(events & (EV_READ|EV_WRITE|EV_CLOSED)))
242		return (0);
243
244	poll_check_ok(pop);
245	if (pop->nfds + 1 >= pop->event_count) {
246		struct pollfd *tmp_event_set;
247		int tmp_event_count;
248
249		if (pop->event_count < 32)
250			tmp_event_count = 32;
251		else
252			tmp_event_count = pop->event_count * 2;
253
254		/* We need more file descriptors */
255		tmp_event_set = mm_realloc(pop->event_set,
256				 tmp_event_count * sizeof(struct pollfd));
257		if (tmp_event_set == NULL) {
258			event_warn("realloc");
259			return (-1);
260		}
261		pop->event_set = tmp_event_set;
262
263		pop->event_count = tmp_event_count;
264		pop->realloc_copy = 1;
265	}
266
267	i = idx->idxplus1 - 1;
268
269	if (i >= 0) {
270		pfd = &pop->event_set[i];
271	} else {
272		i = pop->nfds++;
273		pfd = &pop->event_set[i];
274		pfd->events = 0;
275		pfd->fd = fd;
276		idx->idxplus1 = i + 1;
277	}
278
279	pfd->revents = 0;
280	if (events & EV_WRITE)
281		pfd->events |= POLLOUT;
282	if (events & EV_READ)
283		pfd->events |= POLLIN;
284	if (events & EV_CLOSED)
285		pfd->events |= POLLRDHUP;
286	poll_check_ok(pop);
287
288	return (0);
289}
290
291/*
292 * Nothing to be done here.
293 */
294
295static int
296poll_del(struct event_base *base, int fd, short old, short events, void *idx_)
297{
298	struct pollop *pop = base->evbase;
299	struct pollfd *pfd = NULL;
300	struct pollidx *idx = idx_;
301	int i;
302
303	EVUTIL_ASSERT((events & EV_SIGNAL) == 0);
304	if (!(events & (EV_READ|EV_WRITE|EV_CLOSED)))
305		return (0);
306
307	poll_check_ok(pop);
308	i = idx->idxplus1 - 1;
309	if (i < 0)
310		return (-1);
311
312	/* Do we still want to read or write? */
313	pfd = &pop->event_set[i];
314	if (events & EV_READ)
315		pfd->events &= ~POLLIN;
316	if (events & EV_WRITE)
317		pfd->events &= ~POLLOUT;
318	if (events & EV_CLOSED)
319		pfd->events &= ~POLLRDHUP;
320	poll_check_ok(pop);
321	if (pfd->events)
322		/* Another event cares about that fd. */
323		return (0);
324
325	/* Okay, so we aren't interested in that fd anymore. */
326	idx->idxplus1 = 0;
327
328	--pop->nfds;
329	if (i != pop->nfds) {
330		/*
331		 * Shift the last pollfd down into the now-unoccupied
332		 * position.
333		 */
334		memcpy(&pop->event_set[i], &pop->event_set[pop->nfds],
335		       sizeof(struct pollfd));
336		idx = evmap_io_get_fdinfo_(&base->io, pop->event_set[i].fd);
337		EVUTIL_ASSERT(idx);
338		EVUTIL_ASSERT(idx->idxplus1 == pop->nfds + 1);
339		idx->idxplus1 = i + 1;
340	}
341
342	poll_check_ok(pop);
343	return (0);
344}
345
346static void
347poll_dealloc(struct event_base *base)
348{
349	struct pollop *pop = base->evbase;
350
351	evsig_dealloc_(base);
352	if (pop->event_set)
353		mm_free(pop->event_set);
354	if (pop->event_set_copy)
355		mm_free(pop->event_set_copy);
356
357	memset(pop, 0, sizeof(struct pollop));
358	mm_free(pop);
359}
360
361#endif /* EVENT__HAVE_POLL */
362