1 /* $NetBSD: select.c,v 1.5 2021/04/10 19:18:45 rillig Exp $ */
2 /* $OpenBSD: select.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: select.c,v 1.5 2021/04/10 19:18:45 rillig Exp $");
33 #include "evconfig-private.h"
34
35 #ifdef EVENT__HAVE_SELECT
36
37 #ifdef __APPLE__
38 /* Apple wants us to define this if we might ever pass more than
39 * FD_SETSIZE bits to select(). */
40 #define _DARWIN_UNLIMITED_SELECT
41 #endif
42
43 #include <sys/types.h>
44 #ifdef EVENT__HAVE_SYS_TIME_H
45 #include <sys/time.h>
46 #endif
47 #ifdef EVENT__HAVE_SYS_SELECT_H
48 #include <sys/select.h>
49 #endif
50 #include <sys/queue.h>
51 #include <signal.h>
52 #include <stdio.h>
53 #include <stdlib.h>
54 #include <string.h>
55 #include <unistd.h>
56 #include <errno.h>
57
58 #include "event-internal.h"
59 #include "evsignal-internal.h"
60 #include "event2/thread.h"
61 #include "evthread-internal.h"
62 #include "log-internal.h"
63 #include "evmap-internal.h"
64
65 #ifndef EVENT__HAVE_FD_MASK
66 /* This type is mandatory, but Android doesn't define it. */
67 typedef unsigned long fd_mask;
68 #endif
69
70 #ifndef NFDBITS
71 #define NFDBITS (sizeof(fd_mask)*8)
72 #endif
73
74 /* Divide positive x by y, rounding up. */
75 #define DIV_ROUNDUP(x, y) (((x)+((y)-1))/(y))
76
77 /* How many bytes to allocate for N fds? */
78 #define SELECT_ALLOC_SIZE(n) \
79 (DIV_ROUNDUP(n, NFDBITS) * sizeof(fd_mask))
80
81 struct selectop {
82 int event_fds; /* Highest fd in fd set */
83 int event_fdsz;
84 int resize_out_sets;
85 fd_set *event_readset_in;
86 fd_set *event_writeset_in;
87 fd_set *event_readset_out;
88 fd_set *event_writeset_out;
89 };
90
91 static void *select_init(struct event_base *);
92 static int select_add(struct event_base *, int, short old, short events, void*);
93 static int select_del(struct event_base *, int, short old, short events, void*);
94 static int select_dispatch(struct event_base *, struct timeval *);
95 static void select_dealloc(struct event_base *);
96
97 const struct eventop selectops = {
98 "select",
99 select_init,
100 select_add,
101 select_del,
102 select_dispatch,
103 select_dealloc,
104 1, /* need_reinit. */
105 EV_FEATURE_FDS,
106 0,
107 };
108
109 static int select_resize(struct selectop *sop, int fdsz);
110 static void select_free_selectop(struct selectop *sop);
111
112 static void *
select_init(struct event_base * base)113 select_init(struct event_base *base)
114 {
115 struct selectop *sop;
116
117 if (!(sop = mm_calloc(1, sizeof(struct selectop))))
118 return (NULL);
119
120 if (select_resize(sop, SELECT_ALLOC_SIZE(32 + 1))) {
121 select_free_selectop(sop);
122 return (NULL);
123 }
124
125 evsig_init_(base);
126
127 evutil_weakrand_seed_(&base->weakrand_seed, 0);
128
129 return (sop);
130 }
131
132 #ifdef CHECK_INVARIANTS
133 static void
check_selectop(struct selectop * sop)134 check_selectop(struct selectop *sop)
135 {
136 /* nothing to be done here */
137 }
138 #else
139 #define check_selectop(sop) do { (void) sop; } while (0)
140 #endif
141
142 static int
select_dispatch(struct event_base * base,struct timeval * tv)143 select_dispatch(struct event_base *base, struct timeval *tv)
144 {
145 int res=0, i, j, nfds;
146 struct selectop *sop = base->evbase;
147
148 check_selectop(sop);
149 if (sop->resize_out_sets) {
150 fd_set *readset_out=NULL, *writeset_out=NULL;
151 size_t sz = sop->event_fdsz;
152 if (!(readset_out = mm_realloc(sop->event_readset_out, sz)))
153 return (-1);
154 sop->event_readset_out = readset_out;
155 if (!(writeset_out = mm_realloc(sop->event_writeset_out, sz))) {
156 /* We don't free readset_out here, since it was
157 * already successfully reallocated. The next time
158 * we call select_dispatch, the realloc will be a
159 * no-op. */
160 return (-1);
161 }
162 sop->event_writeset_out = writeset_out;
163 sop->resize_out_sets = 0;
164 }
165
166 memcpy(sop->event_readset_out, sop->event_readset_in,
167 sop->event_fdsz);
168 memcpy(sop->event_writeset_out, sop->event_writeset_in,
169 sop->event_fdsz);
170
171 nfds = sop->event_fds+1;
172
173 EVBASE_RELEASE_LOCK(base, th_base_lock);
174
175 res = select(nfds, sop->event_readset_out,
176 sop->event_writeset_out, NULL, tv);
177
178 EVBASE_ACQUIRE_LOCK(base, th_base_lock);
179
180 check_selectop(sop);
181
182 if (res == -1) {
183 if (errno != EINTR) {
184 event_warn("select");
185 return (-1);
186 }
187
188 return (0);
189 }
190
191 event_debug(("%s: select reports %d", __func__, res));
192
193 check_selectop(sop);
194 i = evutil_weakrand_range_(&base->weakrand_seed, nfds);
195 for (j = 0; j < nfds; ++j) {
196 if (++i >= nfds)
197 i = 0;
198 res = 0;
199 if (FD_ISSET(i, sop->event_readset_out))
200 res |= EV_READ;
201 if (FD_ISSET(i, sop->event_writeset_out))
202 res |= EV_WRITE;
203
204 if (res == 0)
205 continue;
206
207 evmap_io_active_(base, i, res);
208 }
209 check_selectop(sop);
210
211 return (0);
212 }
213
214 static int
select_resize(struct selectop * sop,int fdsz)215 select_resize(struct selectop *sop, int fdsz)
216 {
217 fd_set *readset_in = NULL;
218 fd_set *writeset_in = NULL;
219
220 if (sop->event_readset_in)
221 check_selectop(sop);
222
223 if ((readset_in = mm_realloc(sop->event_readset_in, fdsz)) == NULL)
224 goto error;
225 sop->event_readset_in = readset_in;
226 if ((writeset_in = mm_realloc(sop->event_writeset_in, fdsz)) == NULL) {
227 /* Note that this will leave event_readset_in expanded.
228 * That's okay; we wouldn't want to free it, since that would
229 * change the semantics of select_resize from "expand the
230 * readset_in and writeset_in, or return -1" to "expand the
231 * *set_in members, or trash them and return -1."
232 */
233 goto error;
234 }
235 sop->event_writeset_in = writeset_in;
236 sop->resize_out_sets = 1;
237
238 memset((char *)sop->event_readset_in + sop->event_fdsz, 0,
239 fdsz - sop->event_fdsz);
240 memset((char *)sop->event_writeset_in + sop->event_fdsz, 0,
241 fdsz - sop->event_fdsz);
242
243 sop->event_fdsz = fdsz;
244 check_selectop(sop);
245
246 return (0);
247
248 error:
249 event_warn("malloc");
250 return (-1);
251 }
252
253
254 static int
select_add(struct event_base * base,int fd,short old,short events,void * p)255 select_add(struct event_base *base, int fd, short old, short events, void *p)
256 {
257 struct selectop *sop = base->evbase;
258 (void) p;
259
260 EVUTIL_ASSERT((events & EV_SIGNAL) == 0);
261 check_selectop(sop);
262 /*
263 * Keep track of the highest fd, so that we can calculate the size
264 * of the fd_sets for select(2)
265 */
266 if (sop->event_fds < fd) {
267 int fdsz = sop->event_fdsz;
268
269 if (fdsz < (int)sizeof(fd_mask))
270 fdsz = (int)sizeof(fd_mask);
271
272 /* In theory we should worry about overflow here. In
273 * reality, though, the highest fd on a unixy system will
274 * not overflow here. XXXX */
275 while (fdsz < (int) SELECT_ALLOC_SIZE(fd + 1))
276 fdsz *= 2;
277
278 if (fdsz != sop->event_fdsz) {
279 if (select_resize(sop, fdsz)) {
280 check_selectop(sop);
281 return (-1);
282 }
283 }
284
285 sop->event_fds = fd;
286 }
287
288 if (events & EV_READ)
289 FD_SET(fd, sop->event_readset_in);
290 if (events & EV_WRITE)
291 FD_SET(fd, sop->event_writeset_in);
292 check_selectop(sop);
293
294 return (0);
295 }
296
297 /*
298 * Nothing to be done here.
299 */
300
301 static int
select_del(struct event_base * base,int fd,short old,short events,void * p)302 select_del(struct event_base *base, int fd, short old, short events, void *p)
303 {
304 struct selectop *sop = base->evbase;
305 (void)p;
306
307 EVUTIL_ASSERT((events & EV_SIGNAL) == 0);
308 check_selectop(sop);
309
310 if (sop->event_fds < fd) {
311 check_selectop(sop);
312 return (0);
313 }
314
315 if (events & EV_READ)
316 FD_CLR(fd, sop->event_readset_in);
317
318 if (events & EV_WRITE)
319 FD_CLR(fd, sop->event_writeset_in);
320
321 check_selectop(sop);
322 return (0);
323 }
324
325 static void
select_free_selectop(struct selectop * sop)326 select_free_selectop(struct selectop *sop)
327 {
328 if (sop->event_readset_in)
329 mm_free(sop->event_readset_in);
330 if (sop->event_writeset_in)
331 mm_free(sop->event_writeset_in);
332 if (sop->event_readset_out)
333 mm_free(sop->event_readset_out);
334 if (sop->event_writeset_out)
335 mm_free(sop->event_writeset_out);
336
337 memset(sop, 0, sizeof(struct selectop));
338 mm_free(sop);
339 }
340
341 static void
select_dealloc(struct event_base * base)342 select_dealloc(struct event_base *base)
343 {
344 evsig_dealloc_(base);
345
346 select_free_selectop(base->evbase);
347 }
348
349 #endif /* EVENT__HAVE_SELECT */
350