xref: /linux/net/rxrpc/call_event.c (revision 84e28aa5)
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  */
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  */
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 	call->ackr_serial = serial;
47 
48 	if (rxrpc_soft_ack_delay < expiry)
49 		expiry = rxrpc_soft_ack_delay;
50 	if (call->peer->srtt_us != 0)
51 		ack_at = usecs_to_jiffies(call->peer->srtt_us >> 3);
52 	else
53 		ack_at = expiry;
54 
55 	ack_at += READ_ONCE(call->tx_backoff);
56 	ack_at += now;
57 	if (time_before(ack_at, call->delay_ack_at)) {
58 		WRITE_ONCE(call->delay_ack_at, ack_at);
59 		rxrpc_reduce_call_timer(call, ack_at, now,
60 					rxrpc_timer_set_for_ack);
61 	}
62 
63 	trace_rxrpc_propose_ack(call, why, RXRPC_ACK_DELAY, serial);
64 }
65 
66 /*
67  * Queue an ACK for immediate transmission.
68  */
69 void rxrpc_send_ACK(struct rxrpc_call *call, u8 ack_reason,
70 		    rxrpc_serial_t serial, enum rxrpc_propose_ack_trace why)
71 {
72 	struct rxrpc_txbuf *txb;
73 
74 	if (test_bit(RXRPC_CALL_DISCONNECTED, &call->flags))
75 		return;
76 
77 	rxrpc_inc_stat(call->rxnet, stat_tx_acks[ack_reason]);
78 
79 	txb = rxrpc_alloc_txbuf(call, RXRPC_PACKET_TYPE_ACK,
80 				rcu_read_lock_held() ? GFP_ATOMIC | __GFP_NOWARN : GFP_NOFS);
81 	if (!txb) {
82 		kleave(" = -ENOMEM");
83 		return;
84 	}
85 
86 	txb->ack_why		= why;
87 	txb->wire.seq		= 0;
88 	txb->wire.type		= RXRPC_PACKET_TYPE_ACK;
89 	txb->wire.flags		|= RXRPC_SLOW_START_OK;
90 	txb->ack.bufferSpace	= 0;
91 	txb->ack.maxSkew	= 0;
92 	txb->ack.firstPacket	= 0;
93 	txb->ack.previousPacket	= 0;
94 	txb->ack.serial		= htonl(serial);
95 	txb->ack.reason		= ack_reason;
96 	txb->ack.nAcks		= 0;
97 
98 	trace_rxrpc_send_ack(call, why, ack_reason, serial);
99 	rxrpc_send_ack_packet(call, txb);
100 	rxrpc_put_txbuf(txb, rxrpc_txbuf_put_ack_tx);
101 }
102 
103 /*
104  * Handle congestion being detected by the retransmit timeout.
105  */
106 static void rxrpc_congestion_timeout(struct rxrpc_call *call)
107 {
108 	set_bit(RXRPC_CALL_RETRANS_TIMEOUT, &call->flags);
109 }
110 
111 /*
112  * Perform retransmission of NAK'd and unack'd packets.
113  */
114 void rxrpc_resend(struct rxrpc_call *call, struct sk_buff *ack_skb)
115 {
116 	struct rxrpc_ackpacket *ack = NULL;
117 	struct rxrpc_txbuf *txb;
118 	unsigned long resend_at;
119 	rxrpc_seq_t transmitted = READ_ONCE(call->tx_transmitted);
120 	ktime_t now, max_age, oldest, ack_ts;
121 	bool unacked = false;
122 	unsigned int i;
123 	LIST_HEAD(retrans_queue);
124 
125 	_enter("{%d,%d}", call->acks_hard_ack, call->tx_top);
126 
127 	now = ktime_get_real();
128 	max_age = ktime_sub_us(now, jiffies_to_usecs(call->peer->rto_j));
129 	oldest = now;
130 
131 	if (list_empty(&call->tx_buffer))
132 		goto no_resend;
133 
134 	if (list_empty(&call->tx_buffer))
135 		goto no_further_resend;
136 
137 	trace_rxrpc_resend(call, ack_skb);
138 	txb = list_first_entry(&call->tx_buffer, struct rxrpc_txbuf, call_link);
139 
140 	/* Scan the soft ACK table without dropping the lock and resend any
141 	 * explicitly NAK'd packets.
142 	 */
143 	if (ack_skb) {
144 		ack = (void *)ack_skb->data + sizeof(struct rxrpc_wire_header);
145 
146 		for (i = 0; i < ack->nAcks; i++) {
147 			rxrpc_seq_t seq;
148 
149 			if (ack->acks[i] & 1)
150 				continue;
151 			seq = ntohl(ack->firstPacket) + 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  */
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  */
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 
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  */
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 
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  */
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  */
373 bool rxrpc_input_call_event(struct rxrpc_call *call, struct sk_buff *skb)
374 {
375 	unsigned long now, next, t;
376 	rxrpc_serial_t ackr_serial;
377 	bool resend = false, expired = false;
378 	s32 abort_code;
379 
380 	rxrpc_see_call(call, rxrpc_call_see_input);
381 
382 	//printk("\n--------------------\n");
383 	_enter("{%d,%s,%lx}",
384 	       call->debug_id, rxrpc_call_states[__rxrpc_call_state(call)],
385 	       call->events);
386 
387 	if (__rxrpc_call_is_complete(call))
388 		goto out;
389 
390 	/* Handle abort request locklessly, vs rxrpc_propose_abort(). */
391 	abort_code = smp_load_acquire(&call->send_abort);
392 	if (abort_code) {
393 		rxrpc_abort_call(call, 0, call->send_abort, call->send_abort_err,
394 				 call->send_abort_why);
395 		goto out;
396 	}
397 
398 	if (skb && skb->mark == RXRPC_SKB_MARK_ERROR)
399 		goto out;
400 
401 	/* If we see our async-event poke, check for timeout trippage. */
402 	now = jiffies;
403 	t = READ_ONCE(call->expect_rx_by);
404 	if (time_after_eq(now, t)) {
405 		trace_rxrpc_timer(call, rxrpc_timer_exp_normal, now);
406 		expired = true;
407 	}
408 
409 	t = READ_ONCE(call->expect_req_by);
410 	if (__rxrpc_call_state(call) == RXRPC_CALL_SERVER_RECV_REQUEST &&
411 	    time_after_eq(now, t)) {
412 		trace_rxrpc_timer(call, rxrpc_timer_exp_idle, now);
413 		expired = true;
414 	}
415 
416 	t = READ_ONCE(call->expect_term_by);
417 	if (time_after_eq(now, t)) {
418 		trace_rxrpc_timer(call, rxrpc_timer_exp_hard, now);
419 		expired = true;
420 	}
421 
422 	t = READ_ONCE(call->delay_ack_at);
423 	if (time_after_eq(now, t)) {
424 		trace_rxrpc_timer(call, rxrpc_timer_exp_ack, now);
425 		cmpxchg(&call->delay_ack_at, t, now + MAX_JIFFY_OFFSET);
426 		ackr_serial = xchg(&call->ackr_serial, 0);
427 		rxrpc_send_ACK(call, RXRPC_ACK_DELAY, ackr_serial,
428 			       rxrpc_propose_ack_ping_for_lost_ack);
429 	}
430 
431 	t = READ_ONCE(call->ack_lost_at);
432 	if (time_after_eq(now, t)) {
433 		trace_rxrpc_timer(call, rxrpc_timer_exp_lost_ack, now);
434 		cmpxchg(&call->ack_lost_at, t, now + MAX_JIFFY_OFFSET);
435 		set_bit(RXRPC_CALL_EV_ACK_LOST, &call->events);
436 	}
437 
438 	t = READ_ONCE(call->keepalive_at);
439 	if (time_after_eq(now, t)) {
440 		trace_rxrpc_timer(call, rxrpc_timer_exp_keepalive, now);
441 		cmpxchg(&call->keepalive_at, t, now + MAX_JIFFY_OFFSET);
442 		rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
443 			       rxrpc_propose_ack_ping_for_keepalive);
444 	}
445 
446 	t = READ_ONCE(call->ping_at);
447 	if (time_after_eq(now, t)) {
448 		trace_rxrpc_timer(call, rxrpc_timer_exp_ping, now);
449 		cmpxchg(&call->ping_at, t, now + MAX_JIFFY_OFFSET);
450 		rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
451 			       rxrpc_propose_ack_ping_for_keepalive);
452 	}
453 
454 	t = READ_ONCE(call->resend_at);
455 	if (time_after_eq(now, t)) {
456 		trace_rxrpc_timer(call, rxrpc_timer_exp_resend, now);
457 		cmpxchg(&call->resend_at, t, now + MAX_JIFFY_OFFSET);
458 		resend = true;
459 	}
460 
461 	if (skb)
462 		rxrpc_input_call_packet(call, skb);
463 
464 	rxrpc_transmit_some_data(call);
465 
466 	if (skb) {
467 		struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
468 
469 		if (sp->hdr.type == RXRPC_PACKET_TYPE_ACK)
470 			rxrpc_congestion_degrade(call);
471 	}
472 
473 	if (test_and_clear_bit(RXRPC_CALL_EV_INITIAL_PING, &call->events))
474 		rxrpc_send_initial_ping(call);
475 
476 	/* Process events */
477 	if (expired) {
478 		if (test_bit(RXRPC_CALL_RX_HEARD, &call->flags) &&
479 		    (int)call->conn->hi_serial - (int)call->rx_serial > 0) {
480 			trace_rxrpc_call_reset(call);
481 			rxrpc_abort_call(call, 0, RX_CALL_DEAD, -ECONNRESET,
482 					 rxrpc_abort_call_reset);
483 		} else {
484 			rxrpc_abort_call(call, 0, RX_CALL_TIMEOUT, -ETIME,
485 					 rxrpc_abort_call_timeout);
486 		}
487 		goto out;
488 	}
489 
490 	if (test_and_clear_bit(RXRPC_CALL_EV_ACK_LOST, &call->events))
491 		rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
492 			       rxrpc_propose_ack_ping_for_lost_ack);
493 
494 	if (resend && __rxrpc_call_state(call) != RXRPC_CALL_CLIENT_RECV_REPLY)
495 		rxrpc_resend(call, NULL);
496 
497 	if (test_and_clear_bit(RXRPC_CALL_RX_IS_IDLE, &call->flags))
498 		rxrpc_send_ACK(call, RXRPC_ACK_IDLE, 0,
499 			       rxrpc_propose_ack_rx_idle);
500 
501 	if (atomic_read(&call->ackr_nr_unacked) > 2) {
502 		if (call->peer->rtt_count < 3)
503 			rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
504 				       rxrpc_propose_ack_ping_for_rtt);
505 		else if (ktime_before(ktime_add_ms(call->peer->rtt_last_req, 1000),
506 				      ktime_get_real()))
507 			rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
508 				       rxrpc_propose_ack_ping_for_old_rtt);
509 		else
510 			rxrpc_send_ACK(call, RXRPC_ACK_IDLE, 0,
511 				       rxrpc_propose_ack_input_data);
512 	}
513 
514 	/* Make sure the timer is restarted */
515 	if (!__rxrpc_call_is_complete(call)) {
516 		next = call->expect_rx_by;
517 
518 #define set(T) { t = READ_ONCE(T); if (time_before(t, next)) next = t; }
519 
520 		set(call->expect_req_by);
521 		set(call->expect_term_by);
522 		set(call->delay_ack_at);
523 		set(call->ack_lost_at);
524 		set(call->resend_at);
525 		set(call->keepalive_at);
526 		set(call->ping_at);
527 
528 		now = jiffies;
529 		if (time_after_eq(now, next))
530 			rxrpc_poke_call(call, rxrpc_call_poke_timer_now);
531 
532 		rxrpc_reduce_call_timer(call, next, now, rxrpc_timer_restart);
533 	}
534 
535 out:
536 	if (__rxrpc_call_is_complete(call)) {
537 		del_timer_sync(&call->timer);
538 		if (!test_bit(RXRPC_CALL_DISCONNECTED, &call->flags))
539 			rxrpc_disconnect_call(call);
540 		if (call->security)
541 			call->security->free_call_crypto(call);
542 	}
543 	if (call->acks_hard_ack != call->tx_bottom)
544 		rxrpc_shrink_call_tx_buffer(call);
545 	_leave("");
546 	return true;
547 }
548