1 /*
2 * Ring buffer management
3 *
4 * Copyright (C) 2000-2019 Willy Tarreau - w@1wt.eu
5 *
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation, version 2.1
9 * exclusively.
10 *
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20
21 #include <stdlib.h>
22 #include <haproxy/api.h>
23 #include <haproxy/applet.h>
24 #include <haproxy/buf.h>
25 #include <haproxy/cli.h>
26 #include <haproxy/ring.h>
27 #include <haproxy/stream_interface.h>
28 #include <haproxy/thread.h>
29
30 /* Initialize a pre-allocated ring with the buffer area
31 * of size */
ring_init(struct ring * ring,void * area,size_t size)32 void ring_init(struct ring *ring, void *area, size_t size)
33 {
34 HA_RWLOCK_INIT(&ring->lock);
35 LIST_INIT(&ring->waiters);
36 ring->readers_count = 0;
37 ring->ofs = 0;
38 ring->buf = b_make(area, size, 0, 0);
39 /* write the initial RC byte */
40 b_putchr(&ring->buf, 0);
41 }
42
43 /* Creates and returns a ring buffer of size <size> bytes. Returns NULL on
44 * allocation failure.
45 */
ring_new(size_t size)46 struct ring *ring_new(size_t size)
47 {
48 struct ring *ring = NULL;
49 void *area = NULL;
50
51 if (size < 2)
52 goto fail;
53
54 ring = malloc(sizeof(*ring));
55 if (!ring)
56 goto fail;
57
58 area = malloc(size);
59 if (!area)
60 goto fail;
61
62 ring_init(ring, area, size);
63 return ring;
64 fail:
65 free(area);
66 free(ring);
67 return NULL;
68 }
69
70 /* Resizes existing ring <ring> to <size> which must be larger, without losing
71 * its contents. The new size must be at least as large as the previous one or
72 * no change will be performed. The pointer to the ring is returned on success,
73 * or NULL on allocation failure. This will lock the ring for writes.
74 */
ring_resize(struct ring * ring,size_t size)75 struct ring *ring_resize(struct ring *ring, size_t size)
76 {
77 void *area;
78
79 if (b_size(&ring->buf) >= size)
80 return ring;
81
82 area = malloc(size);
83 if (!area)
84 return NULL;
85
86 HA_RWLOCK_WRLOCK(LOGSRV_LOCK, &ring->lock);
87
88 /* recheck the buffer's size, it may have changed during the malloc */
89 if (b_size(&ring->buf) < size) {
90 /* copy old contents */
91 b_getblk(&ring->buf, area, ring->buf.data, 0);
92 area = HA_ATOMIC_XCHG(&ring->buf.area, area);
93 ring->buf.size = size;
94 ring->buf.head = 0;
95 }
96
97 HA_RWLOCK_WRUNLOCK(LOGSRV_LOCK, &ring->lock);
98
99 free(area);
100 return ring;
101 }
102
103 /* destroys and frees ring <ring> */
ring_free(struct ring * ring)104 void ring_free(struct ring *ring)
105 {
106 if (!ring)
107 return;
108 free(ring->buf.area);
109 free(ring);
110 }
111
112 /* Tries to send <npfx> parts from <prefix> followed by <nmsg> parts from <msg>
113 * to ring <ring>. The message is sent atomically. It may be truncated to
114 * <maxlen> bytes if <maxlen> is non-null. There is no distinction between the
115 * two lists, it's just a convenience to help the caller prepend some prefixes
116 * when necessary. It takes the ring's write lock to make sure no other thread
117 * will touch the buffer during the update. Returns the number of bytes sent,
118 * or <=0 on failure.
119 */
ring_write(struct ring * ring,size_t maxlen,const struct ist pfx[],size_t npfx,const struct ist msg[],size_t nmsg)120 ssize_t ring_write(struct ring *ring, size_t maxlen, const struct ist pfx[], size_t npfx, const struct ist msg[], size_t nmsg)
121 {
122 struct buffer *buf = &ring->buf;
123 struct appctx *appctx;
124 size_t totlen = 0;
125 size_t lenlen;
126 uint64_t dellen;
127 int dellenlen;
128 ssize_t sent = 0;
129 int i;
130
131 /* we have to find some room to add our message (the buffer is
132 * never empty and at least contains the previous counter) and
133 * to update both the buffer contents and heads at the same
134 * time (it's doable using atomic ops but not worth the
135 * trouble, let's just lock). For this we first need to know
136 * the total message's length. We cannot measure it while
137 * copying due to the varint encoding of the length.
138 */
139 for (i = 0; i < npfx; i++)
140 totlen += pfx[i].len;
141 for (i = 0; i < nmsg; i++)
142 totlen += msg[i].len;
143
144 if (totlen > maxlen)
145 totlen = maxlen;
146
147 lenlen = varint_bytes(totlen);
148
149 HA_RWLOCK_WRLOCK(LOGSRV_LOCK, &ring->lock);
150 if (lenlen + totlen + 1 + 1 > b_size(buf))
151 goto done_buf;
152
153 while (b_room(buf) < lenlen + totlen + 1) {
154 /* we need to delete the oldest message (from the end),
155 * and we have to stop if there's a reader stuck there.
156 * Unless there's corruption in the buffer it's guaranteed
157 * that we have enough data to find 1 counter byte, a
158 * varint-encoded length (1 byte min) and the message
159 * payload (0 bytes min).
160 */
161 if (*b_head(buf))
162 goto done_buf;
163 dellenlen = b_peek_varint(buf, 1, &dellen);
164 if (!dellenlen)
165 goto done_buf;
166 BUG_ON(b_data(buf) < 1 + dellenlen + dellen);
167
168 b_del(buf, 1 + dellenlen + dellen);
169 ring->ofs += 1 + dellenlen + dellen;
170 }
171
172 /* OK now we do have room */
173 __b_put_varint(buf, totlen);
174
175 totlen = 0;
176 for (i = 0; i < npfx; i++) {
177 size_t len = pfx[i].len;
178
179 if (len + totlen > maxlen)
180 len = maxlen - totlen;
181 if (len)
182 __b_putblk(buf, pfx[i].ptr, len);
183 totlen += len;
184 }
185
186 for (i = 0; i < nmsg; i++) {
187 size_t len = msg[i].len;
188
189 if (len + totlen > maxlen)
190 len = maxlen - totlen;
191 if (len)
192 __b_putblk(buf, msg[i].ptr, len);
193 totlen += len;
194 }
195
196 *b_tail(buf) = 0; buf->data++; // new read counter
197 sent = lenlen + totlen + 1;
198
199 /* notify potential readers */
200 list_for_each_entry(appctx, &ring->waiters, wait_entry)
201 appctx_wakeup(appctx);
202
203 done_buf:
204 HA_RWLOCK_WRUNLOCK(LOGSRV_LOCK, &ring->lock);
205 return sent;
206 }
207
208 /* Tries to attach appctx <appctx> as a new reader on ring <ring>. This is
209 * meant to be used by low level appctx code such as CLI or ring forwarding.
210 * For higher level functions, please see the relevant parts in appctx or CLI.
211 * It returns non-zero on success or zero on failure if too many users are
212 * already attached. On success, the caller MUST call ring_detach_appctx()
213 * to detach itself, even if it was never woken up.
214 */
ring_attach(struct ring * ring)215 int ring_attach(struct ring *ring)
216 {
217 int users = ring->readers_count;
218
219 do {
220 if (users >= 255)
221 return 0;
222 } while (!_HA_ATOMIC_CAS(&ring->readers_count, &users, users + 1));
223 return 1;
224 }
225
226 /* detach an appctx from a ring. The appctx is expected to be waiting at
227 * offset <ofs>. Nothing is done if <ring> is NULL.
228 */
ring_detach_appctx(struct ring * ring,struct appctx * appctx,size_t ofs)229 void ring_detach_appctx(struct ring *ring, struct appctx *appctx, size_t ofs)
230 {
231 if (!ring)
232 return;
233
234 HA_RWLOCK_WRLOCK(LOGSRV_LOCK, &ring->lock);
235 if (ofs != ~0) {
236 /* reader was still attached */
237 ofs -= ring->ofs;
238 BUG_ON(ofs >= b_size(&ring->buf));
239 LIST_DEL_INIT(&appctx->wait_entry);
240 HA_ATOMIC_DEC(b_peek(&ring->buf, ofs));
241 }
242 HA_ATOMIC_DEC(&ring->readers_count);
243 HA_RWLOCK_WRUNLOCK(LOGSRV_LOCK, &ring->lock);
244 }
245
246 /* Tries to attach CLI handler <appctx> as a new reader on ring <ring>. This is
247 * meant to be used when registering a CLI function to dump a buffer, so it
248 * returns zero on success, or non-zero on failure with a message in the appctx
249 * CLI context. It automatically sets the io_handler and io_release callbacks if
250 * they were not set.
251 */
ring_attach_cli(struct ring * ring,struct appctx * appctx)252 int ring_attach_cli(struct ring *ring, struct appctx *appctx)
253 {
254 if (!ring_attach(ring))
255 return cli_err(appctx,
256 "Sorry, too many watchers (255) on this ring buffer. "
257 "What could it have so interesting to attract so many watchers ?");
258
259 if (!appctx->io_handler)
260 appctx->io_handler = cli_io_handler_show_ring;
261 if (!appctx->io_release)
262 appctx->io_release = cli_io_release_show_ring;
263 appctx->ctx.cli.p0 = ring;
264 appctx->ctx.cli.o0 = ~0; // start from the oldest event
265 return 0;
266 }
267
268 /* This function dumps all events from the ring whose pointer is in <p0> into
269 * the appctx's output buffer, and takes from <o0> the seek offset into the
270 * buffer's history (0 for oldest known event). It looks at <i0> for boolean
271 * options: bit0 means it must wait for new data or any key to be pressed. Bit1
272 * means it must seek directly to the end to wait for new contents. It returns
273 * 0 if the output buffer or events are missing is full and it needs to be
274 * called again, otherwise non-zero. It is meant to be used with
275 * cli_release_show_ring() to clean up.
276 */
cli_io_handler_show_ring(struct appctx * appctx)277 int cli_io_handler_show_ring(struct appctx *appctx)
278 {
279 struct stream_interface *si = appctx->owner;
280 struct ring *ring = appctx->ctx.cli.p0;
281 struct buffer *buf = &ring->buf;
282 size_t ofs = appctx->ctx.cli.o0;
283 uint64_t msg_len;
284 size_t len, cnt;
285 int ret;
286
287 if (unlikely(si_ic(si)->flags & (CF_WRITE_ERROR|CF_SHUTW)))
288 return 1;
289
290 HA_RWLOCK_WRLOCK(LOGSRV_LOCK, &ring->lock);
291 LIST_DEL_INIT(&appctx->wait_entry);
292 HA_RWLOCK_WRUNLOCK(LOGSRV_LOCK, &ring->lock);
293
294 HA_RWLOCK_RDLOCK(LOGSRV_LOCK, &ring->lock);
295
296 /* explanation for the initialization below: it would be better to do
297 * this in the parsing function but this would occasionally result in
298 * dropped events because we'd take a reference on the oldest message
299 * and keep it while being scheduled. Thus instead let's take it the
300 * first time we enter here so that we have a chance to pass many
301 * existing messages before grabbing a reference to a location. This
302 * value cannot be produced after initialization.
303 */
304 if (unlikely(ofs == ~0)) {
305 ofs = 0;
306
307 /* going to the end means looking at tail-1 */
308 if (appctx->ctx.cli.i0 & 2)
309 ofs += b_data(buf) - 1;
310
311 HA_ATOMIC_INC(b_peek(buf, ofs));
312 ofs += ring->ofs;
313 }
314
315 /* we were already there, adjust the offset to be relative to
316 * the buffer's head and remove us from the counter.
317 */
318 ofs -= ring->ofs;
319 BUG_ON(ofs >= buf->size);
320 HA_ATOMIC_DEC(b_peek(buf, ofs));
321
322 /* in this loop, ofs always points to the counter byte that precedes
323 * the message so that we can take our reference there if we have to
324 * stop before the end (ret=0).
325 */
326 ret = 1;
327 while (ofs + 1 < b_data(buf)) {
328 cnt = 1;
329 len = b_peek_varint(buf, ofs + cnt, &msg_len);
330 if (!len)
331 break;
332 cnt += len;
333 BUG_ON(msg_len + ofs + cnt + 1 > b_data(buf));
334
335 if (unlikely(msg_len + 1 > b_size(&trash))) {
336 /* too large a message to ever fit, let's skip it */
337 ofs += cnt + msg_len;
338 continue;
339 }
340
341 chunk_reset(&trash);
342 len = b_getblk(buf, trash.area, msg_len, ofs + cnt);
343 trash.data += len;
344 trash.area[trash.data++] = '\n';
345
346 if (ci_putchk(si_ic(si), &trash) == -1) {
347 si_rx_room_blk(si);
348 ret = 0;
349 break;
350 }
351 ofs += cnt + msg_len;
352 }
353
354 HA_ATOMIC_INC(b_peek(buf, ofs));
355 ofs += ring->ofs;
356 appctx->ctx.cli.o0 = ofs;
357 HA_RWLOCK_RDUNLOCK(LOGSRV_LOCK, &ring->lock);
358
359 if (ret && (appctx->ctx.cli.i0 & 1)) {
360 /* we've drained everything and are configured to wait for more
361 * data or an event (keypress, close)
362 */
363 if (!si_oc(si)->output && !(si_oc(si)->flags & CF_SHUTW)) {
364 /* let's be woken up once new data arrive */
365 HA_RWLOCK_WRLOCK(LOGSRV_LOCK, &ring->lock);
366 LIST_APPEND(&ring->waiters, &appctx->wait_entry);
367 HA_RWLOCK_WRUNLOCK(LOGSRV_LOCK, &ring->lock);
368 si_rx_endp_done(si);
369 ret = 0;
370 }
371 /* always drain all the request */
372 co_skip(si_oc(si), si_oc(si)->output);
373 }
374 return ret;
375 }
376
377 /* must be called after cli_io_handler_show_ring() above */
cli_io_release_show_ring(struct appctx * appctx)378 void cli_io_release_show_ring(struct appctx *appctx)
379 {
380 struct ring *ring = appctx->ctx.cli.p0;
381 size_t ofs = appctx->ctx.cli.o0;
382
383 ring_detach_appctx(ring, appctx, ofs);
384 }
385
386
387 /*
388 * Local variables:
389 * c-indent-level: 8
390 * c-basic-offset: 8
391 * End:
392 */
393