1 /*
2 * Copyright (c) 2009-2012 Niels Provos, Nick Mathewson
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 * 3. The name of the author may not be used to endorse or promote products
13 * derived from this software without specific prior written permission.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26 #include "event2/event-config.h"
27 #include "evconfig-private.h"
28
29 #include <sys/types.h>
30
31 #ifdef _WIN32
32 #include <winsock2.h>
33 #endif
34
35 #include "event2/util.h"
36 #include "event2/buffer.h"
37 #include "event2/bufferevent.h"
38 #include "event2/bufferevent_struct.h"
39 #include "event2/event.h"
40 #include "defer-internal.h"
41 #include "bufferevent-internal.h"
42 #include "mm-internal.h"
43 #include "util-internal.h"
44
45 struct bufferevent_pair {
46 struct bufferevent_private bev;
47 struct bufferevent_pair *partner;
48 /* For ->destruct() lock checking */
49 struct bufferevent_pair *unlinked_partner;
50 };
51
52
53 /* Given a bufferevent that's really a bev part of a bufferevent_pair,
54 * return that bufferevent_filtered. Returns NULL otherwise.*/
55 static inline struct bufferevent_pair *
upcast(struct bufferevent * bev)56 upcast(struct bufferevent *bev)
57 {
58 struct bufferevent_pair *bev_p;
59 if (!BEV_IS_PAIR(bev))
60 return NULL;
61 bev_p = EVUTIL_UPCAST(bev, struct bufferevent_pair, bev.bev);
62 EVUTIL_ASSERT(BEV_IS_PAIR(&bev_p->bev.bev));
63 return bev_p;
64 }
65
66 #define downcast(bev_pair) (&(bev_pair)->bev.bev)
67
68 static inline void
incref_and_lock(struct bufferevent * b)69 incref_and_lock(struct bufferevent *b)
70 {
71 struct bufferevent_pair *bevp;
72 bufferevent_incref_and_lock_(b);
73 bevp = upcast(b);
74 if (bevp->partner)
75 bufferevent_incref_and_lock_(downcast(bevp->partner));
76 }
77
78 static inline void
decref_and_unlock(struct bufferevent * b)79 decref_and_unlock(struct bufferevent *b)
80 {
81 struct bufferevent_pair *bevp = upcast(b);
82 if (bevp->partner)
83 bufferevent_decref_and_unlock_(downcast(bevp->partner));
84 bufferevent_decref_and_unlock_(b);
85 }
86
87 /* XXX Handle close */
88
89 static void be_pair_outbuf_cb(struct evbuffer *,
90 const struct evbuffer_cb_info *, void *);
91
92 static struct bufferevent_pair *
bufferevent_pair_elt_new(struct event_base * base,int options)93 bufferevent_pair_elt_new(struct event_base *base,
94 int options)
95 {
96 struct bufferevent_pair *bufev;
97 if (! (bufev = mm_calloc(1, sizeof(struct bufferevent_pair))))
98 return NULL;
99 if (bufferevent_init_common_(&bufev->bev, base, &bufferevent_ops_pair,
100 options)) {
101 mm_free(bufev);
102 return NULL;
103 }
104 if (!evbuffer_add_cb(bufev->bev.bev.output, be_pair_outbuf_cb, bufev)) {
105 bufferevent_free(downcast(bufev));
106 return NULL;
107 }
108
109 bufferevent_init_generic_timeout_cbs_(&bufev->bev.bev);
110
111 return bufev;
112 }
113
114 int
bufferevent_pair_new(struct event_base * base,int options,struct bufferevent * pair[2])115 bufferevent_pair_new(struct event_base *base, int options,
116 struct bufferevent *pair[2])
117 {
118 struct bufferevent_pair *bufev1 = NULL, *bufev2 = NULL;
119 int tmp_options;
120
121 options |= BEV_OPT_DEFER_CALLBACKS;
122 tmp_options = options & ~BEV_OPT_THREADSAFE;
123
124 bufev1 = bufferevent_pair_elt_new(base, options);
125 if (!bufev1)
126 return -1;
127 bufev2 = bufferevent_pair_elt_new(base, tmp_options);
128 if (!bufev2) {
129 bufferevent_free(downcast(bufev1));
130 return -1;
131 }
132
133 if (options & BEV_OPT_THREADSAFE) {
134 /*XXXX check return */
135 bufferevent_enable_locking_(downcast(bufev2), bufev1->bev.lock);
136 }
137
138 bufev1->partner = bufev2;
139 bufev2->partner = bufev1;
140
141 evbuffer_freeze(downcast(bufev1)->input, 0);
142 evbuffer_freeze(downcast(bufev1)->output, 1);
143 evbuffer_freeze(downcast(bufev2)->input, 0);
144 evbuffer_freeze(downcast(bufev2)->output, 1);
145
146 pair[0] = downcast(bufev1);
147 pair[1] = downcast(bufev2);
148
149 return 0;
150 }
151
152 static void
be_pair_transfer(struct bufferevent * src,struct bufferevent * dst,int ignore_wm)153 be_pair_transfer(struct bufferevent *src, struct bufferevent *dst,
154 int ignore_wm)
155 {
156 size_t dst_size;
157 size_t n;
158
159 evbuffer_unfreeze(src->output, 1);
160 evbuffer_unfreeze(dst->input, 0);
161
162 if (dst->wm_read.high) {
163 dst_size = evbuffer_get_length(dst->input);
164 if (dst_size < dst->wm_read.high) {
165 n = dst->wm_read.high - dst_size;
166 evbuffer_remove_buffer(src->output, dst->input, n);
167 } else {
168 if (!ignore_wm)
169 goto done;
170 n = evbuffer_get_length(src->output);
171 evbuffer_add_buffer(dst->input, src->output);
172 }
173 } else {
174 n = evbuffer_get_length(src->output);
175 evbuffer_add_buffer(dst->input, src->output);
176 }
177
178 if (n) {
179 BEV_RESET_GENERIC_READ_TIMEOUT(dst);
180
181 if (evbuffer_get_length(dst->output))
182 BEV_RESET_GENERIC_WRITE_TIMEOUT(dst);
183 else
184 BEV_DEL_GENERIC_WRITE_TIMEOUT(dst);
185 }
186
187 bufferevent_trigger_nolock_(dst, EV_READ, 0);
188 bufferevent_trigger_nolock_(src, EV_WRITE, 0);
189 done:
190 evbuffer_freeze(src->output, 1);
191 evbuffer_freeze(dst->input, 0);
192 }
193
194 static inline int
be_pair_wants_to_talk(struct bufferevent_pair * src,struct bufferevent_pair * dst)195 be_pair_wants_to_talk(struct bufferevent_pair *src,
196 struct bufferevent_pair *dst)
197 {
198 return (downcast(src)->enabled & EV_WRITE) &&
199 (downcast(dst)->enabled & EV_READ) &&
200 !dst->bev.read_suspended &&
201 evbuffer_get_length(downcast(src)->output);
202 }
203
204 static void
be_pair_outbuf_cb(struct evbuffer * outbuf,const struct evbuffer_cb_info * info,void * arg)205 be_pair_outbuf_cb(struct evbuffer *outbuf,
206 const struct evbuffer_cb_info *info, void *arg)
207 {
208 struct bufferevent_pair *bev_pair = arg;
209 struct bufferevent_pair *partner = bev_pair->partner;
210
211 incref_and_lock(downcast(bev_pair));
212
213 if (info->n_added > info->n_deleted && partner) {
214 /* We got more data. If the other side's reading, then
215 hand it over. */
216 if (be_pair_wants_to_talk(bev_pair, partner)) {
217 be_pair_transfer(downcast(bev_pair), downcast(partner), 0);
218 }
219 }
220
221 decref_and_unlock(downcast(bev_pair));
222 }
223
224 static int
be_pair_enable(struct bufferevent * bufev,short events)225 be_pair_enable(struct bufferevent *bufev, short events)
226 {
227 struct bufferevent_pair *bev_p = upcast(bufev);
228 struct bufferevent_pair *partner = bev_p->partner;
229
230 incref_and_lock(bufev);
231
232 if (events & EV_READ) {
233 BEV_RESET_GENERIC_READ_TIMEOUT(bufev);
234 }
235 if ((events & EV_WRITE) && evbuffer_get_length(bufev->output))
236 BEV_RESET_GENERIC_WRITE_TIMEOUT(bufev);
237
238 /* We're starting to read! Does the other side have anything to write?*/
239 if ((events & EV_READ) && partner &&
240 be_pair_wants_to_talk(partner, bev_p)) {
241 be_pair_transfer(downcast(partner), bufev, 0);
242 }
243 /* We're starting to write! Does the other side want to read? */
244 if ((events & EV_WRITE) && partner &&
245 be_pair_wants_to_talk(bev_p, partner)) {
246 be_pair_transfer(bufev, downcast(partner), 0);
247 }
248 decref_and_unlock(bufev);
249 return 0;
250 }
251
252 static int
be_pair_disable(struct bufferevent * bev,short events)253 be_pair_disable(struct bufferevent *bev, short events)
254 {
255 if (events & EV_READ) {
256 BEV_DEL_GENERIC_READ_TIMEOUT(bev);
257 }
258 if (events & EV_WRITE) {
259 BEV_DEL_GENERIC_WRITE_TIMEOUT(bev);
260 }
261 return 0;
262 }
263
264 static void
be_pair_unlink(struct bufferevent * bev)265 be_pair_unlink(struct bufferevent *bev)
266 {
267 struct bufferevent_pair *bev_p = upcast(bev);
268
269 if (bev_p->partner) {
270 bev_p->unlinked_partner = bev_p->partner;
271 bev_p->partner->partner = NULL;
272 bev_p->partner = NULL;
273 }
274 }
275
276 /* Free *shared* lock in the latest be (since we share it between two of them). */
277 static void
be_pair_destruct(struct bufferevent * bev)278 be_pair_destruct(struct bufferevent *bev)
279 {
280 struct bufferevent_pair *bev_p = upcast(bev);
281
282 /* Transfer ownership of the lock into partner, otherwise we will use
283 * already free'd lock during freeing second bev, see next example:
284 *
285 * bev1->own_lock = 1
286 * bev2->own_lock = 0
287 * bev2->lock = bev1->lock
288 *
289 * bufferevent_free(bev1) # refcnt == 0 -> unlink
290 * bufferevent_free(bev2) # refcnt == 0 -> unlink
291 *
292 * event_base_free() -> finilizers -> EVTHREAD_FREE_LOCK(bev1->lock)
293 * -> BEV_LOCK(bev2->lock) <-- already freed
294 *
295 * Where bev1 == pair[0], bev2 == pair[1].
296 */
297 if (bev_p->unlinked_partner && bev_p->bev.own_lock) {
298 bev_p->unlinked_partner->bev.own_lock = 1;
299 bev_p->bev.own_lock = 0;
300 }
301 bev_p->unlinked_partner = NULL;
302 }
303
304 static int
be_pair_flush(struct bufferevent * bev,short iotype,enum bufferevent_flush_mode mode)305 be_pair_flush(struct bufferevent *bev, short iotype,
306 enum bufferevent_flush_mode mode)
307 {
308 struct bufferevent_pair *bev_p = upcast(bev);
309 struct bufferevent *partner;
310
311 if (!bev_p->partner)
312 return -1;
313
314 if (mode == BEV_NORMAL)
315 return 0;
316
317 incref_and_lock(bev);
318
319 partner = downcast(bev_p->partner);
320
321 if ((iotype & EV_READ) != 0)
322 be_pair_transfer(partner, bev, 1);
323
324 if ((iotype & EV_WRITE) != 0)
325 be_pair_transfer(bev, partner, 1);
326
327 if (mode == BEV_FINISHED) {
328 short what = BEV_EVENT_EOF;
329 if (iotype & EV_READ)
330 what |= BEV_EVENT_WRITING;
331 if (iotype & EV_WRITE)
332 what |= BEV_EVENT_READING;
333 bufferevent_run_eventcb_(partner, what, 0);
334 }
335 decref_and_unlock(bev);
336 return 0;
337 }
338
339 struct bufferevent *
bufferevent_pair_get_partner(struct bufferevent * bev)340 bufferevent_pair_get_partner(struct bufferevent *bev)
341 {
342 struct bufferevent_pair *bev_p;
343 struct bufferevent *partner = NULL;
344 bev_p = upcast(bev);
345 if (! bev_p)
346 return NULL;
347
348 incref_and_lock(bev);
349 if (bev_p->partner)
350 partner = downcast(bev_p->partner);
351 decref_and_unlock(bev);
352 return partner;
353 }
354
355 const struct bufferevent_ops bufferevent_ops_pair = {
356 "pair_elt",
357 evutil_offsetof(struct bufferevent_pair, bev.bev),
358 be_pair_enable,
359 be_pair_disable,
360 be_pair_unlink,
361 be_pair_destruct,
362 bufferevent_generic_adj_timeouts_,
363 be_pair_flush,
364 NULL, /* ctrl */
365 };
366