1 /*	$OpenBSD: select.c,v 1.2 2002/06/25 15:50:15 mickey Exp $	*/
2 
3 /*
4  * Copyright 2000-2007 Niels Provos <provos@citi.umich.edu>
5  * Copyright 2007-2012 Niels Provos and Nick Mathewson
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. The name of the author may not be used to endorse or promote products
16  *    derived from this software without specific prior written permission.
17  *
18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
23  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28  */
29 #include "event2/event-config.h"
30 #include "evconfig-private.h"
31 
32 #ifdef EVENT__HAVE_SELECT
33 
34 #ifdef __APPLE__
35 /* Apple wants us to define this if we might ever pass more than
36  * FD_SETSIZE bits to select(). */
37 #define _DARWIN_UNLIMITED_SELECT
38 #endif
39 
40 #include <sys/types.h>
41 #ifdef EVENT__HAVE_SYS_TIME_H
42 #include <sys/time.h>
43 #endif
44 #ifdef EVENT__HAVE_SYS_SELECT_H
45 #include <sys/select.h>
46 #endif
47 #include <sys/queue.h>
48 #include <signal.h>
49 #include <stdio.h>
50 #include <stdlib.h>
51 #include <string.h>
52 #include <unistd.h>
53 #include <errno.h>
54 
55 #include "event-internal.h"
56 #include "evsignal-internal.h"
57 #include "event2/thread.h"
58 #include "evthread-internal.h"
59 #include "log-internal.h"
60 #include "evmap-internal.h"
61 
62 #ifndef EVENT__HAVE_FD_MASK
63 /* This type is mandatory, but Android doesn't define it. */
64 typedef unsigned long fd_mask;
65 #endif
66 
67 #ifndef NFDBITS
68 #define NFDBITS (sizeof(fd_mask)*8)
69 #endif
70 
71 /* Divide positive x by y, rounding up. */
72 #define DIV_ROUNDUP(x, y)   (((x)+((y)-1))/(y))
73 
74 /* How many bytes to allocate for N fds? */
75 #define SELECT_ALLOC_SIZE(n) \
76 	(DIV_ROUNDUP(n, NFDBITS) * sizeof(fd_mask))
77 
78 struct selectop {
79 	int event_fds;		/* Highest fd in fd set */
80 	int event_fdsz;
81 	int resize_out_sets;
82 	fd_set *event_readset_in;
83 	fd_set *event_writeset_in;
84 	fd_set *event_readset_out;
85 	fd_set *event_writeset_out;
86 };
87 
88 static void *select_init(struct event_base *);
89 static int select_add(struct event_base *, int, short old, short events, void*);
90 static int select_del(struct event_base *, int, short old, short events, void*);
91 static int select_dispatch(struct event_base *, struct timeval *);
92 static void select_dealloc(struct event_base *);
93 
94 const struct eventop selectops = {
95 	"select",
96 	select_init,
97 	select_add,
98 	select_del,
99 	select_dispatch,
100 	select_dealloc,
101 	0, /* doesn't need reinit. */
102 	EV_FEATURE_FDS,
103 	0,
104 };
105 
106 static int select_resize(struct selectop *sop, int fdsz);
107 static void select_free_selectop(struct selectop *sop);
108 
109 static void *
select_init(struct event_base * base)110 select_init(struct event_base *base)
111 {
112 	struct selectop *sop;
113 
114 	if (!(sop = mm_calloc(1, sizeof(struct selectop))))
115 		return (NULL);
116 
117 	if (select_resize(sop, SELECT_ALLOC_SIZE(32 + 1))) {
118 		select_free_selectop(sop);
119 		return (NULL);
120 	}
121 
122 	evsig_init_(base);
123 
124 	evutil_weakrand_seed_(&base->weakrand_seed, 0);
125 
126 	return (sop);
127 }
128 
129 #ifdef CHECK_INVARIANTS
130 static void
check_selectop(struct selectop * sop)131 check_selectop(struct selectop *sop)
132 {
133 	/* nothing to be done here */
134 }
135 #else
136 #define check_selectop(sop) do { (void) sop; } while (0)
137 #endif
138 
139 static int
select_dispatch(struct event_base * base,struct timeval * tv)140 select_dispatch(struct event_base *base, struct timeval *tv)
141 {
142 	int res=0, i, j, nfds;
143 	struct selectop *sop = base->evbase;
144 
145 	check_selectop(sop);
146 	if (sop->resize_out_sets) {
147 		fd_set *readset_out=NULL, *writeset_out=NULL;
148 		size_t sz = sop->event_fdsz;
149 		if (!(readset_out = mm_realloc(sop->event_readset_out, sz)))
150 			return (-1);
151 		sop->event_readset_out = readset_out;
152 		if (!(writeset_out = mm_realloc(sop->event_writeset_out, sz))) {
153 			/* We don't free readset_out here, since it was
154 			 * already successfully reallocated. The next time
155 			 * we call select_dispatch, the realloc will be a
156 			 * no-op. */
157 			return (-1);
158 		}
159 		sop->event_writeset_out = writeset_out;
160 		sop->resize_out_sets = 0;
161 	}
162 
163 	memcpy(sop->event_readset_out, sop->event_readset_in,
164 	       sop->event_fdsz);
165 	memcpy(sop->event_writeset_out, sop->event_writeset_in,
166 	       sop->event_fdsz);
167 
168 	nfds = sop->event_fds+1;
169 
170 	EVBASE_RELEASE_LOCK(base, th_base_lock);
171 
172 	res = select(nfds, sop->event_readset_out,
173 	    sop->event_writeset_out, NULL, tv);
174 
175 	EVBASE_ACQUIRE_LOCK(base, th_base_lock);
176 
177 	check_selectop(sop);
178 
179 	if (res == -1) {
180 		if (errno != EINTR) {
181 			event_warn("select");
182 			return (-1);
183 		}
184 
185 		return (0);
186 	}
187 
188 	event_debug(("%s: select reports %d", __func__, res));
189 
190 	check_selectop(sop);
191 	i = evutil_weakrand_range_(&base->weakrand_seed, nfds);
192 	for (j = 0; j < nfds; ++j) {
193 		if (++i >= nfds)
194 			i = 0;
195 		res = 0;
196 		if (FD_ISSET(i, sop->event_readset_out))
197 			res |= EV_READ;
198 		if (FD_ISSET(i, sop->event_writeset_out))
199 			res |= EV_WRITE;
200 
201 		if (res == 0)
202 			continue;
203 
204 		evmap_io_active_(base, i, res);
205 	}
206 	check_selectop(sop);
207 
208 	return (0);
209 }
210 
211 static int
select_resize(struct selectop * sop,int fdsz)212 select_resize(struct selectop *sop, int fdsz)
213 {
214 	fd_set *readset_in = NULL;
215 	fd_set *writeset_in = NULL;
216 
217 	if (sop->event_readset_in)
218 		check_selectop(sop);
219 
220 	if ((readset_in = mm_realloc(sop->event_readset_in, fdsz)) == NULL)
221 		goto error;
222 	sop->event_readset_in = readset_in;
223 	if ((writeset_in = mm_realloc(sop->event_writeset_in, fdsz)) == NULL) {
224 		/* Note that this will leave event_readset_in expanded.
225 		 * That's okay; we wouldn't want to free it, since that would
226 		 * change the semantics of select_resize from "expand the
227 		 * readset_in and writeset_in, or return -1" to "expand the
228 		 * *set_in members, or trash them and return -1."
229 		 */
230 		goto error;
231 	}
232 	sop->event_writeset_in = writeset_in;
233 	sop->resize_out_sets = 1;
234 
235 	memset((char *)sop->event_readset_in + sop->event_fdsz, 0,
236 	    fdsz - sop->event_fdsz);
237 	memset((char *)sop->event_writeset_in + sop->event_fdsz, 0,
238 	    fdsz - sop->event_fdsz);
239 
240 	sop->event_fdsz = fdsz;
241 	check_selectop(sop);
242 
243 	return (0);
244 
245  error:
246 	event_warn("malloc");
247 	return (-1);
248 }
249 
250 
251 static int
select_add(struct event_base * base,int fd,short old,short events,void * p)252 select_add(struct event_base *base, int fd, short old, short events, void *p)
253 {
254 	struct selectop *sop = base->evbase;
255 	(void) p;
256 
257 	EVUTIL_ASSERT((events & EV_SIGNAL) == 0);
258 	check_selectop(sop);
259 	/*
260 	 * Keep track of the highest fd, so that we can calculate the size
261 	 * of the fd_sets for select(2)
262 	 */
263 	if (sop->event_fds < fd) {
264 		int fdsz = sop->event_fdsz;
265 
266 		if (fdsz < (int)sizeof(fd_mask))
267 			fdsz = (int)sizeof(fd_mask);
268 
269 		/* In theory we should worry about overflow here.  In
270 		 * reality, though, the highest fd on a unixy system will
271 		 * not overflow here. XXXX */
272 		while (fdsz < (int) SELECT_ALLOC_SIZE(fd + 1))
273 			fdsz *= 2;
274 
275 		if (fdsz != sop->event_fdsz) {
276 			if (select_resize(sop, fdsz)) {
277 				check_selectop(sop);
278 				return (-1);
279 			}
280 		}
281 
282 		sop->event_fds = fd;
283 	}
284 
285 	if (events & EV_READ)
286 		FD_SET(fd, sop->event_readset_in);
287 	if (events & EV_WRITE)
288 		FD_SET(fd, sop->event_writeset_in);
289 	check_selectop(sop);
290 
291 	return (0);
292 }
293 
294 /*
295  * Nothing to be done here.
296  */
297 
298 static int
select_del(struct event_base * base,int fd,short old,short events,void * p)299 select_del(struct event_base *base, int fd, short old, short events, void *p)
300 {
301 	struct selectop *sop = base->evbase;
302 	(void)p;
303 
304 	EVUTIL_ASSERT((events & EV_SIGNAL) == 0);
305 	check_selectop(sop);
306 
307 	if (sop->event_fds < fd) {
308 		check_selectop(sop);
309 		return (0);
310 	}
311 
312 	if (events & EV_READ)
313 		FD_CLR(fd, sop->event_readset_in);
314 
315 	if (events & EV_WRITE)
316 		FD_CLR(fd, sop->event_writeset_in);
317 
318 	check_selectop(sop);
319 	return (0);
320 }
321 
322 static void
select_free_selectop(struct selectop * sop)323 select_free_selectop(struct selectop *sop)
324 {
325 	if (sop->event_readset_in)
326 		mm_free(sop->event_readset_in);
327 	if (sop->event_writeset_in)
328 		mm_free(sop->event_writeset_in);
329 	if (sop->event_readset_out)
330 		mm_free(sop->event_readset_out);
331 	if (sop->event_writeset_out)
332 		mm_free(sop->event_writeset_out);
333 
334 	memset(sop, 0, sizeof(struct selectop));
335 	mm_free(sop);
336 }
337 
338 static void
select_dealloc(struct event_base * base)339 select_dealloc(struct event_base *base)
340 {
341 	evsig_dealloc_(base);
342 
343 	select_free_selectop(base->evbase);
344 }
345 
346 #endif /* EVENT__HAVE_SELECT */
347