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 */
23void 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, expire_at: ping_at, now,
32 why: 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 */
40void 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(u: 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, expire_at: ack_at, now,
60 why: 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 */
69void 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 gfp: 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, what: rxrpc_txbuf_put_ack_tx);
101}
102
103/*
104 * Handle congestion being detected by the retransmit timeout.
105 */
106static void rxrpc_congestion_timeout(struct rxrpc_call *call)
107{
108 set_bit(nr: RXRPC_CALL_RETRANS_TIMEOUT, addr: &call->flags);
109}
110
111/*
112 * Perform retransmission of NAK'd and unack'd packets.
113 */
114void 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(kt: now, usec: jiffies_to_usecs(j: call->peer->rto_j));
129 oldest = now;
130
131 if (list_empty(head: &call->tx_buffer))
132 goto no_resend;
133
134 if (list_empty(head: &call->tx_buffer))
135 goto no_further_resend;
136
137 trace_rxrpc_resend(call, ack: 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(seq1: txb->seq, seq2: transmitted))
153 break;
154 if (after(seq1: txb->seq, seq2: 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), seq2: call->acks_highest_serial))
164 continue; /* Ack point not yet reached */
165
166 rxrpc_see_txbuf(txb, what: rxrpc_txbuf_see_unacked);
167
168 if (list_empty(head: &txb->tx_link)) {
169 list_add_tail(new: &txb->tx_link, head: &retrans_queue);
170 set_bit(RXRPC_TXBUF_RESENT, addr: &txb->flags);
171 }
172
173 trace_rxrpc_retransmit(call, seq: txb->seq,
174 expiry: ktime_to_ns(ktime_sub(txb->last_sent,
175 max_age)));
176
177 if (list_is_last(list: &txb->call_link, head: &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(seq1: txb->seq, READ_ONCE(call->acks_prev_seq)))
195 continue;
196 if (after(seq1: 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(cmp1: txb->last_sent, cmp2: max_age)) {
204 if (ktime_before(cmp1: txb->last_sent, cmp2: oldest))
205 oldest = txb->last_sent;
206 continue;
207 }
208
209 do_resend:
210 unacked = true;
211 if (list_empty(head: &txb->tx_link)) {
212 list_add_tail(new: &txb->tx_link, head: &retrans_queue);
213 set_bit(RXRPC_TXBUF_RESENT, addr: &txb->flags);
214 rxrpc_inc_stat(call->rxnet, stat_tx_data_retrans);
215 }
216 }
217
218no_further_resend:
219no_resend:
220 resend_at = nsecs_to_jiffies(n: ktime_to_ns(ktime_sub(now, oldest)));
221 resend_at += jiffies + rxrpc_get_rto_backoff(call->peer,
222 !list_empty(head: &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(head: &retrans_queue)) {
233 rxrpc_reduce_call_timer(call, expire_at: resend_at, now: jiffies,
234 why: rxrpc_timer_set_for_resend);
235 ack_ts = ktime_sub(now, call->acks_latest_ts);
236 if (ktime_to_us(kt: ack_ts) < (call->peer->srtt_us >> 3))
237 goto out;
238 rxrpc_send_ACK(call, RXRPC_ACK_PING, serial: 0,
239 why: 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(entry: &txb->tx_link);
247 rxrpc_transmit_one(call, txb);
248 }
249
250out:
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 */
258static void rxrpc_begin_service_reply(struct rxrpc_call *call)
259{
260 unsigned long now = jiffies;
261
262 rxrpc_set_call_state(call, state: 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, why: 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 */
273static 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, state: RXRPC_CALL_CLIENT_AWAIT_REPLY);
280 break;
281 case RXRPC_CALL_SERVER_SEND_REPLY:
282 rxrpc_set_call_state(call, state: RXRPC_CALL_SERVER_AWAIT_ACK);
283 break;
284 default:
285 break;
286 }
287}
288
289static 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 */
304static 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(head: &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(lock: &call->tx_lock);
317 list_del(entry: &txb->call_link);
318 spin_unlock(lock: &call->tx_lock);
319
320 call->tx_top = txb->seq;
321 list_add_tail(new: &txb->call_link, head: &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
333static 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(head: &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(head: &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 */
361static void rxrpc_send_initial_ping(struct rxrpc_call *call)
362{
363 if (call->peer->rtt_count < 3 ||
364 ktime_before(cmp1: ktime_add_ms(kt: call->peer->rtt_last_req, msec: 1000),
365 cmp2: ktime_get_real()))
366 rxrpc_send_ACK(call, RXRPC_ACK_PING, serial: 0,
367 why: rxrpc_propose_ack_ping_for_params);
368}
369
370/*
371 * Handle retransmission and deferred ACK/abort generation.
372 */
373bool 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, seq: 0, abort_code: call->send_abort, error: call->send_abort_err,
394 why: 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, why: 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, why: 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, why: 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, why: 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, serial: ackr_serial,
428 why: 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, why: rxrpc_timer_exp_lost_ack, now);
434 cmpxchg(&call->ack_lost_at, t, now + MAX_JIFFY_OFFSET);
435 set_bit(nr: RXRPC_CALL_EV_ACK_LOST, addr: &call->events);
436 }
437
438 t = READ_ONCE(call->keepalive_at);
439 if (time_after_eq(now, t)) {
440 trace_rxrpc_timer(call, why: rxrpc_timer_exp_keepalive, now);
441 cmpxchg(&call->keepalive_at, t, now + MAX_JIFFY_OFFSET);
442 rxrpc_send_ACK(call, RXRPC_ACK_PING, serial: 0,
443 why: 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, why: rxrpc_timer_exp_ping, now);
449 cmpxchg(&call->ping_at, t, now + MAX_JIFFY_OFFSET);
450 rxrpc_send_ACK(call, RXRPC_ACK_PING, serial: 0,
451 why: 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, why: 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(nr: RXRPC_CALL_EV_INITIAL_PING, addr: &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, seq: 0, RX_CALL_DEAD, error: -ECONNRESET,
482 why: rxrpc_abort_call_reset);
483 } else {
484 rxrpc_abort_call(call, seq: 0, RX_CALL_TIMEOUT, error: -ETIME,
485 why: rxrpc_abort_call_timeout);
486 }
487 goto out;
488 }
489
490 if (test_and_clear_bit(nr: RXRPC_CALL_EV_ACK_LOST, addr: &call->events))
491 rxrpc_send_ACK(call, RXRPC_ACK_PING, serial: 0,
492 why: 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(nr: RXRPC_CALL_RX_IS_IDLE, addr: &call->flags))
498 rxrpc_send_ACK(call, RXRPC_ACK_IDLE, serial: 0,
499 why: rxrpc_propose_ack_rx_idle);
500
501 if (call->ackr_nr_unacked > 2) {
502 if (call->peer->rtt_count < 3)
503 rxrpc_send_ACK(call, RXRPC_ACK_PING, serial: 0,
504 why: rxrpc_propose_ack_ping_for_rtt);
505 else if (ktime_before(cmp1: ktime_add_ms(kt: call->peer->rtt_last_req, msec: 1000),
506 cmp2: ktime_get_real()))
507 rxrpc_send_ACK(call, RXRPC_ACK_PING, serial: 0,
508 why: rxrpc_propose_ack_ping_for_old_rtt);
509 else
510 rxrpc_send_ACK(call, RXRPC_ACK_IDLE, serial: 0,
511 why: 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, what: rxrpc_call_poke_timer_now);
531
532 rxrpc_reduce_call_timer(call, expire_at: next, now, why: rxrpc_timer_restart);
533 }
534
535out:
536 if (__rxrpc_call_is_complete(call)) {
537 del_timer_sync(timer: &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

source code of linux/net/rxrpc/call_event.c