1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Management of Tx window, Tx resend, ACKs and out-of-sequence reception
3 *
4 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9
10 #include <linux/module.h>
11 #include <linux/circ_buf.h>
12 #include <linux/net.h>
13 #include <linux/skbuff.h>
14 #include <linux/slab.h>
15 #include <linux/udp.h>
16 #include <net/sock.h>
17 #include <net/af_rxrpc.h>
18 #include "ar-internal.h"
19
20 /*
21 * Propose a PING ACK be sent.
22 */
rxrpc_propose_ping(struct rxrpc_call * call,u32 serial,enum rxrpc_propose_ack_trace why)23 void rxrpc_propose_ping(struct rxrpc_call *call, u32 serial,
24 enum rxrpc_propose_ack_trace why)
25 {
26 unsigned long now = jiffies;
27 unsigned long ping_at = now + rxrpc_idle_ack_delay;
28
29 if (time_before(ping_at, call->ping_at)) {
30 WRITE_ONCE(call->ping_at, ping_at);
31 rxrpc_reduce_call_timer(call, ping_at, now,
32 rxrpc_timer_set_for_ping);
33 trace_rxrpc_propose_ack(call, why, RXRPC_ACK_PING, serial);
34 }
35 }
36
37 /*
38 * Propose a DELAY ACK be sent in the future.
39 */
rxrpc_propose_delay_ACK(struct rxrpc_call * call,rxrpc_serial_t serial,enum rxrpc_propose_ack_trace why)40 void rxrpc_propose_delay_ACK(struct rxrpc_call *call, rxrpc_serial_t serial,
41 enum rxrpc_propose_ack_trace why)
42 {
43 unsigned long expiry = rxrpc_soft_ack_delay;
44 unsigned long now = jiffies, ack_at;
45
46 if (rxrpc_soft_ack_delay < expiry)
47 expiry = rxrpc_soft_ack_delay;
48 if (call->peer->srtt_us != 0)
49 ack_at = usecs_to_jiffies(call->peer->srtt_us >> 3);
50 else
51 ack_at = expiry;
52
53 ack_at += READ_ONCE(call->tx_backoff);
54 ack_at += now;
55 if (time_before(ack_at, call->delay_ack_at)) {
56 WRITE_ONCE(call->delay_ack_at, ack_at);
57 rxrpc_reduce_call_timer(call, ack_at, now,
58 rxrpc_timer_set_for_ack);
59 }
60
61 trace_rxrpc_propose_ack(call, why, RXRPC_ACK_DELAY, serial);
62 }
63
64 /*
65 * Queue an ACK for immediate transmission.
66 */
rxrpc_send_ACK(struct rxrpc_call * call,u8 ack_reason,rxrpc_serial_t serial,enum rxrpc_propose_ack_trace why)67 void rxrpc_send_ACK(struct rxrpc_call *call, u8 ack_reason,
68 rxrpc_serial_t serial, enum rxrpc_propose_ack_trace why)
69 {
70 struct rxrpc_txbuf *txb;
71
72 if (test_bit(RXRPC_CALL_DISCONNECTED, &call->flags))
73 return;
74
75 rxrpc_inc_stat(call->rxnet, stat_tx_acks[ack_reason]);
76
77 txb = rxrpc_alloc_txbuf(call, RXRPC_PACKET_TYPE_ACK,
78 rcu_read_lock_held() ? GFP_ATOMIC | __GFP_NOWARN : GFP_NOFS);
79 if (!txb) {
80 kleave(" = -ENOMEM");
81 return;
82 }
83
84 txb->ack_why = why;
85 txb->wire.seq = 0;
86 txb->wire.type = RXRPC_PACKET_TYPE_ACK;
87 txb->wire.flags |= RXRPC_SLOW_START_OK;
88 txb->ack.bufferSpace = 0;
89 txb->ack.maxSkew = 0;
90 txb->ack.firstPacket = 0;
91 txb->ack.previousPacket = 0;
92 txb->ack.serial = htonl(serial);
93 txb->ack.reason = ack_reason;
94 txb->ack.nAcks = 0;
95
96 trace_rxrpc_send_ack(call, why, ack_reason, serial);
97 rxrpc_send_ack_packet(call, txb);
98 rxrpc_put_txbuf(txb, rxrpc_txbuf_put_ack_tx);
99 }
100
101 /*
102 * Handle congestion being detected by the retransmit timeout.
103 */
rxrpc_congestion_timeout(struct rxrpc_call * call)104 static void rxrpc_congestion_timeout(struct rxrpc_call *call)
105 {
106 set_bit(RXRPC_CALL_RETRANS_TIMEOUT, &call->flags);
107 }
108
109 /*
110 * Perform retransmission of NAK'd and unack'd packets.
111 */
rxrpc_resend(struct rxrpc_call * call,struct sk_buff * ack_skb)112 void rxrpc_resend(struct rxrpc_call *call, struct sk_buff *ack_skb)
113 {
114 struct rxrpc_ackpacket *ack = NULL;
115 struct rxrpc_skb_priv *sp;
116 struct rxrpc_txbuf *txb;
117 unsigned long resend_at;
118 rxrpc_seq_t transmitted = READ_ONCE(call->tx_transmitted);
119 ktime_t now, max_age, oldest, ack_ts;
120 bool unacked = false;
121 unsigned int i;
122 LIST_HEAD(retrans_queue);
123
124 _enter("{%d,%d}", call->acks_hard_ack, call->tx_top);
125
126 now = ktime_get_real();
127 max_age = ktime_sub_us(now, jiffies_to_usecs(call->peer->rto_j));
128 oldest = now;
129
130 if (list_empty(&call->tx_buffer))
131 goto no_resend;
132
133 if (list_empty(&call->tx_buffer))
134 goto no_further_resend;
135
136 trace_rxrpc_resend(call, ack_skb);
137 txb = list_first_entry(&call->tx_buffer, struct rxrpc_txbuf, call_link);
138
139 /* Scan the soft ACK table without dropping the lock and resend any
140 * explicitly NAK'd packets.
141 */
142 if (ack_skb) {
143 sp = rxrpc_skb(ack_skb);
144 ack = (void *)ack_skb->data + sizeof(struct rxrpc_wire_header);
145
146 for (i = 0; i < sp->nr_acks; i++) {
147 rxrpc_seq_t seq;
148
149 if (ack->acks[i] & 1)
150 continue;
151 seq = sp->first_ack + i;
152 if (after(txb->seq, transmitted))
153 break;
154 if (after(txb->seq, seq))
155 continue; /* A new hard ACK probably came in */
156 list_for_each_entry_from(txb, &call->tx_buffer, call_link) {
157 if (txb->seq == seq)
158 goto found_txb;
159 }
160 goto no_further_resend;
161
162 found_txb:
163 if (after(ntohl(txb->wire.serial), call->acks_highest_serial))
164 continue; /* Ack point not yet reached */
165
166 rxrpc_see_txbuf(txb, rxrpc_txbuf_see_unacked);
167
168 if (list_empty(&txb->tx_link)) {
169 list_add_tail(&txb->tx_link, &retrans_queue);
170 set_bit(RXRPC_TXBUF_RESENT, &txb->flags);
171 }
172
173 trace_rxrpc_retransmit(call, txb->seq,
174 ktime_to_ns(ktime_sub(txb->last_sent,
175 max_age)));
176
177 if (list_is_last(&txb->call_link, &call->tx_buffer))
178 goto no_further_resend;
179 txb = list_next_entry(txb, call_link);
180 }
181 }
182
183 /* Fast-forward through the Tx queue to the point the peer says it has
184 * seen. Anything between the soft-ACK table and that point will get
185 * ACK'd or NACK'd in due course, so don't worry about it here; here we
186 * need to consider retransmitting anything beyond that point.
187 *
188 * Note that ACK for a packet can beat the update of tx_transmitted.
189 */
190 if (after_eq(READ_ONCE(call->acks_prev_seq), READ_ONCE(call->tx_transmitted)))
191 goto no_further_resend;
192
193 list_for_each_entry_from(txb, &call->tx_buffer, call_link) {
194 if (before_eq(txb->seq, READ_ONCE(call->acks_prev_seq)))
195 continue;
196 if (after(txb->seq, READ_ONCE(call->tx_transmitted)))
197 break; /* Not transmitted yet */
198
199 if (ack && ack->reason == RXRPC_ACK_PING_RESPONSE &&
200 before(ntohl(txb->wire.serial), ntohl(ack->serial)))
201 goto do_resend; /* Wasn't accounted for by a more recent ping. */
202
203 if (ktime_after(txb->last_sent, max_age)) {
204 if (ktime_before(txb->last_sent, oldest))
205 oldest = txb->last_sent;
206 continue;
207 }
208
209 do_resend:
210 unacked = true;
211 if (list_empty(&txb->tx_link)) {
212 list_add_tail(&txb->tx_link, &retrans_queue);
213 set_bit(RXRPC_TXBUF_RESENT, &txb->flags);
214 rxrpc_inc_stat(call->rxnet, stat_tx_data_retrans);
215 }
216 }
217
218 no_further_resend:
219 no_resend:
220 resend_at = nsecs_to_jiffies(ktime_to_ns(ktime_sub(now, oldest)));
221 resend_at += jiffies + rxrpc_get_rto_backoff(call->peer,
222 !list_empty(&retrans_queue));
223 WRITE_ONCE(call->resend_at, resend_at);
224
225 if (unacked)
226 rxrpc_congestion_timeout(call);
227
228 /* If there was nothing that needed retransmission then it's likely
229 * that an ACK got lost somewhere. Send a ping to find out instead of
230 * retransmitting data.
231 */
232 if (list_empty(&retrans_queue)) {
233 rxrpc_reduce_call_timer(call, resend_at, jiffies,
234 rxrpc_timer_set_for_resend);
235 ack_ts = ktime_sub(now, call->acks_latest_ts);
236 if (ktime_to_us(ack_ts) < (call->peer->srtt_us >> 3))
237 goto out;
238 rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
239 rxrpc_propose_ack_ping_for_lost_ack);
240 goto out;
241 }
242
243 /* Retransmit the queue */
244 while ((txb = list_first_entry_or_null(&retrans_queue,
245 struct rxrpc_txbuf, tx_link))) {
246 list_del_init(&txb->tx_link);
247 rxrpc_transmit_one(call, txb);
248 }
249
250 out:
251 _leave("");
252 }
253
254 /*
255 * Start transmitting the reply to a service. This cancels the need to ACK the
256 * request if we haven't yet done so.
257 */
rxrpc_begin_service_reply(struct rxrpc_call * call)258 static void rxrpc_begin_service_reply(struct rxrpc_call *call)
259 {
260 unsigned long now = jiffies;
261
262 rxrpc_set_call_state(call, RXRPC_CALL_SERVER_SEND_REPLY);
263 WRITE_ONCE(call->delay_ack_at, now + MAX_JIFFY_OFFSET);
264 if (call->ackr_reason == RXRPC_ACK_DELAY)
265 call->ackr_reason = 0;
266 trace_rxrpc_timer(call, rxrpc_timer_init_for_send_reply, now);
267 }
268
269 /*
270 * Close the transmission phase. After this point there is no more data to be
271 * transmitted in the call.
272 */
rxrpc_close_tx_phase(struct rxrpc_call * call)273 static void rxrpc_close_tx_phase(struct rxrpc_call *call)
274 {
275 _debug("________awaiting reply/ACK__________");
276
277 switch (__rxrpc_call_state(call)) {
278 case RXRPC_CALL_CLIENT_SEND_REQUEST:
279 rxrpc_set_call_state(call, RXRPC_CALL_CLIENT_AWAIT_REPLY);
280 break;
281 case RXRPC_CALL_SERVER_SEND_REPLY:
282 rxrpc_set_call_state(call, RXRPC_CALL_SERVER_AWAIT_ACK);
283 break;
284 default:
285 break;
286 }
287 }
288
rxrpc_tx_window_has_space(struct rxrpc_call * call)289 static bool rxrpc_tx_window_has_space(struct rxrpc_call *call)
290 {
291 unsigned int winsize = min_t(unsigned int, call->tx_winsize,
292 call->cong_cwnd + call->cong_extra);
293 rxrpc_seq_t window = call->acks_hard_ack, wtop = window + winsize;
294 rxrpc_seq_t tx_top = call->tx_top;
295 int space;
296
297 space = wtop - tx_top;
298 return space > 0;
299 }
300
301 /*
302 * Decant some if the sendmsg prepared queue into the transmission buffer.
303 */
rxrpc_decant_prepared_tx(struct rxrpc_call * call)304 static void rxrpc_decant_prepared_tx(struct rxrpc_call *call)
305 {
306 struct rxrpc_txbuf *txb;
307
308 if (!test_bit(RXRPC_CALL_EXPOSED, &call->flags)) {
309 if (list_empty(&call->tx_sendmsg))
310 return;
311 rxrpc_expose_client_call(call);
312 }
313
314 while ((txb = list_first_entry_or_null(&call->tx_sendmsg,
315 struct rxrpc_txbuf, call_link))) {
316 spin_lock(&call->tx_lock);
317 list_del(&txb->call_link);
318 spin_unlock(&call->tx_lock);
319
320 call->tx_top = txb->seq;
321 list_add_tail(&txb->call_link, &call->tx_buffer);
322
323 if (txb->wire.flags & RXRPC_LAST_PACKET)
324 rxrpc_close_tx_phase(call);
325
326 rxrpc_transmit_one(call, txb);
327
328 if (!rxrpc_tx_window_has_space(call))
329 break;
330 }
331 }
332
rxrpc_transmit_some_data(struct rxrpc_call * call)333 static void rxrpc_transmit_some_data(struct rxrpc_call *call)
334 {
335 switch (__rxrpc_call_state(call)) {
336 case RXRPC_CALL_SERVER_ACK_REQUEST:
337 if (list_empty(&call->tx_sendmsg))
338 return;
339 rxrpc_begin_service_reply(call);
340 fallthrough;
341
342 case RXRPC_CALL_SERVER_SEND_REPLY:
343 case RXRPC_CALL_CLIENT_SEND_REQUEST:
344 if (!rxrpc_tx_window_has_space(call))
345 return;
346 if (list_empty(&call->tx_sendmsg)) {
347 rxrpc_inc_stat(call->rxnet, stat_tx_data_underflow);
348 return;
349 }
350 rxrpc_decant_prepared_tx(call);
351 break;
352 default:
353 return;
354 }
355 }
356
357 /*
358 * Ping the other end to fill our RTT cache and to retrieve the rwind
359 * and MTU parameters.
360 */
rxrpc_send_initial_ping(struct rxrpc_call * call)361 static void rxrpc_send_initial_ping(struct rxrpc_call *call)
362 {
363 if (call->peer->rtt_count < 3 ||
364 ktime_before(ktime_add_ms(call->peer->rtt_last_req, 1000),
365 ktime_get_real()))
366 rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
367 rxrpc_propose_ack_ping_for_params);
368 }
369
370 /*
371 * Handle retransmission and deferred ACK/abort generation.
372 */
rxrpc_input_call_event(struct rxrpc_call * call,struct sk_buff * skb)373 bool rxrpc_input_call_event(struct rxrpc_call *call, struct sk_buff *skb)
374 {
375 unsigned long now, next, t;
376 bool resend = false, expired = false;
377 s32 abort_code;
378
379 rxrpc_see_call(call, rxrpc_call_see_input);
380
381 //printk("\n--------------------\n");
382 _enter("{%d,%s,%lx}",
383 call->debug_id, rxrpc_call_states[__rxrpc_call_state(call)],
384 call->events);
385
386 if (__rxrpc_call_is_complete(call))
387 goto out;
388
389 /* Handle abort request locklessly, vs rxrpc_propose_abort(). */
390 abort_code = smp_load_acquire(&call->send_abort);
391 if (abort_code) {
392 rxrpc_abort_call(call, 0, call->send_abort, call->send_abort_err,
393 call->send_abort_why);
394 goto out;
395 }
396
397 if (skb && skb->mark == RXRPC_SKB_MARK_ERROR)
398 goto out;
399
400 /* If we see our async-event poke, check for timeout trippage. */
401 now = jiffies;
402 t = READ_ONCE(call->expect_rx_by);
403 if (time_after_eq(now, t)) {
404 trace_rxrpc_timer(call, rxrpc_timer_exp_normal, now);
405 expired = true;
406 }
407
408 t = READ_ONCE(call->expect_req_by);
409 if (__rxrpc_call_state(call) == RXRPC_CALL_SERVER_RECV_REQUEST &&
410 time_after_eq(now, t)) {
411 trace_rxrpc_timer(call, rxrpc_timer_exp_idle, now);
412 expired = true;
413 }
414
415 t = READ_ONCE(call->expect_term_by);
416 if (time_after_eq(now, t)) {
417 trace_rxrpc_timer(call, rxrpc_timer_exp_hard, now);
418 expired = true;
419 }
420
421 t = READ_ONCE(call->delay_ack_at);
422 if (time_after_eq(now, t)) {
423 trace_rxrpc_timer(call, rxrpc_timer_exp_ack, now);
424 cmpxchg(&call->delay_ack_at, t, now + MAX_JIFFY_OFFSET);
425 rxrpc_send_ACK(call, RXRPC_ACK_DELAY, 0,
426 rxrpc_propose_ack_ping_for_lost_ack);
427 }
428
429 t = READ_ONCE(call->ack_lost_at);
430 if (time_after_eq(now, t)) {
431 trace_rxrpc_timer(call, rxrpc_timer_exp_lost_ack, now);
432 cmpxchg(&call->ack_lost_at, t, now + MAX_JIFFY_OFFSET);
433 set_bit(RXRPC_CALL_EV_ACK_LOST, &call->events);
434 }
435
436 t = READ_ONCE(call->keepalive_at);
437 if (time_after_eq(now, t)) {
438 trace_rxrpc_timer(call, rxrpc_timer_exp_keepalive, now);
439 cmpxchg(&call->keepalive_at, t, now + MAX_JIFFY_OFFSET);
440 rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
441 rxrpc_propose_ack_ping_for_keepalive);
442 }
443
444 t = READ_ONCE(call->ping_at);
445 if (time_after_eq(now, t)) {
446 trace_rxrpc_timer(call, rxrpc_timer_exp_ping, now);
447 cmpxchg(&call->ping_at, t, now + MAX_JIFFY_OFFSET);
448 rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
449 rxrpc_propose_ack_ping_for_keepalive);
450 }
451
452 t = READ_ONCE(call->resend_at);
453 if (time_after_eq(now, t)) {
454 trace_rxrpc_timer(call, rxrpc_timer_exp_resend, now);
455 cmpxchg(&call->resend_at, t, now + MAX_JIFFY_OFFSET);
456 resend = true;
457 }
458
459 if (skb)
460 rxrpc_input_call_packet(call, skb);
461
462 rxrpc_transmit_some_data(call);
463
464 if (skb) {
465 struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
466
467 if (sp->hdr.type == RXRPC_PACKET_TYPE_ACK)
468 rxrpc_congestion_degrade(call);
469 }
470
471 if (test_and_clear_bit(RXRPC_CALL_EV_INITIAL_PING, &call->events))
472 rxrpc_send_initial_ping(call);
473
474 /* Process events */
475 if (expired) {
476 if (test_bit(RXRPC_CALL_RX_HEARD, &call->flags) &&
477 (int)call->conn->hi_serial - (int)call->rx_serial > 0) {
478 trace_rxrpc_call_reset(call);
479 rxrpc_abort_call(call, 0, RX_CALL_DEAD, -ECONNRESET,
480 rxrpc_abort_call_reset);
481 } else {
482 rxrpc_abort_call(call, 0, RX_CALL_TIMEOUT, -ETIME,
483 rxrpc_abort_call_timeout);
484 }
485 goto out;
486 }
487
488 if (test_and_clear_bit(RXRPC_CALL_EV_ACK_LOST, &call->events))
489 rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
490 rxrpc_propose_ack_ping_for_lost_ack);
491
492 if (resend && __rxrpc_call_state(call) != RXRPC_CALL_CLIENT_RECV_REPLY)
493 rxrpc_resend(call, NULL);
494
495 if (test_and_clear_bit(RXRPC_CALL_RX_IS_IDLE, &call->flags))
496 rxrpc_send_ACK(call, RXRPC_ACK_IDLE, 0,
497 rxrpc_propose_ack_rx_idle);
498
499 if (call->ackr_nr_unacked > 2) {
500 if (call->peer->rtt_count < 3)
501 rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
502 rxrpc_propose_ack_ping_for_rtt);
503 else if (ktime_before(ktime_add_ms(call->peer->rtt_last_req, 1000),
504 ktime_get_real()))
505 rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
506 rxrpc_propose_ack_ping_for_old_rtt);
507 else
508 rxrpc_send_ACK(call, RXRPC_ACK_IDLE, 0,
509 rxrpc_propose_ack_input_data);
510 }
511
512 /* Make sure the timer is restarted */
513 if (!__rxrpc_call_is_complete(call)) {
514 next = call->expect_rx_by;
515
516 #define set(T) { t = READ_ONCE(T); if (time_before(t, next)) next = t; }
517
518 set(call->expect_req_by);
519 set(call->expect_term_by);
520 set(call->delay_ack_at);
521 set(call->ack_lost_at);
522 set(call->resend_at);
523 set(call->keepalive_at);
524 set(call->ping_at);
525
526 now = jiffies;
527 if (time_after_eq(now, next))
528 rxrpc_poke_call(call, rxrpc_call_poke_timer_now);
529
530 rxrpc_reduce_call_timer(call, next, now, rxrpc_timer_restart);
531 }
532
533 out:
534 if (__rxrpc_call_is_complete(call)) {
535 del_timer_sync(&call->timer);
536 if (!test_bit(RXRPC_CALL_DISCONNECTED, &call->flags))
537 rxrpc_disconnect_call(call);
538 if (call->security)
539 call->security->free_call_crypto(call);
540 }
541 if (call->acks_hard_ack != call->tx_bottom)
542 rxrpc_shrink_call_tx_buffer(call);
543 _leave("");
544 return true;
545 }
546