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,bool immediate,bool background)23 static void rxrpc_propose_ping(struct rxrpc_call *call,
24 bool immediate, bool background)
25 {
26 if (immediate) {
27 if (background &&
28 !test_and_set_bit(RXRPC_CALL_EV_PING, &call->events))
29 rxrpc_queue_call(call);
30 } else {
31 unsigned long now = jiffies;
32 unsigned long ping_at = now + rxrpc_idle_ack_delay;
33
34 if (time_before(ping_at, call->ping_at)) {
35 WRITE_ONCE(call->ping_at, ping_at);
36 rxrpc_reduce_call_timer(call, ping_at, now,
37 rxrpc_timer_set_for_ping);
38 }
39 }
40 }
41
42 /*
43 * propose an ACK be sent
44 */
__rxrpc_propose_ACK(struct rxrpc_call * call,u8 ack_reason,u32 serial,bool immediate,bool background,enum rxrpc_propose_ack_trace why)45 static void __rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason,
46 u32 serial, bool immediate, bool background,
47 enum rxrpc_propose_ack_trace why)
48 {
49 enum rxrpc_propose_ack_outcome outcome = rxrpc_propose_ack_use;
50 unsigned long expiry = rxrpc_soft_ack_delay;
51 s8 prior = rxrpc_ack_priority[ack_reason];
52
53 /* Pings are handled specially because we don't want to accidentally
54 * lose a ping response by subsuming it into a ping.
55 */
56 if (ack_reason == RXRPC_ACK_PING) {
57 rxrpc_propose_ping(call, immediate, background);
58 goto trace;
59 }
60
61 /* Update DELAY, IDLE, REQUESTED and PING_RESPONSE ACK serial
62 * numbers, but we don't alter the timeout.
63 */
64 _debug("prior %u %u vs %u %u",
65 ack_reason, prior,
66 call->ackr_reason, rxrpc_ack_priority[call->ackr_reason]);
67 if (ack_reason == call->ackr_reason) {
68 if (RXRPC_ACK_UPDATEABLE & (1 << ack_reason)) {
69 outcome = rxrpc_propose_ack_update;
70 call->ackr_serial = serial;
71 }
72 if (!immediate)
73 goto trace;
74 } else if (prior > rxrpc_ack_priority[call->ackr_reason]) {
75 call->ackr_reason = ack_reason;
76 call->ackr_serial = serial;
77 } else {
78 outcome = rxrpc_propose_ack_subsume;
79 }
80
81 switch (ack_reason) {
82 case RXRPC_ACK_REQUESTED:
83 if (rxrpc_requested_ack_delay < expiry)
84 expiry = rxrpc_requested_ack_delay;
85 if (serial == 1)
86 immediate = false;
87 break;
88
89 case RXRPC_ACK_DELAY:
90 if (rxrpc_soft_ack_delay < expiry)
91 expiry = rxrpc_soft_ack_delay;
92 break;
93
94 case RXRPC_ACK_IDLE:
95 if (rxrpc_idle_ack_delay < expiry)
96 expiry = rxrpc_idle_ack_delay;
97 break;
98
99 default:
100 immediate = true;
101 break;
102 }
103
104 if (test_bit(RXRPC_CALL_EV_ACK, &call->events)) {
105 _debug("already scheduled");
106 } else if (immediate || expiry == 0) {
107 _debug("immediate ACK %lx", call->events);
108 if (!test_and_set_bit(RXRPC_CALL_EV_ACK, &call->events) &&
109 background)
110 rxrpc_queue_call(call);
111 } else {
112 unsigned long now = jiffies, ack_at;
113
114 if (call->peer->srtt_us != 0)
115 ack_at = usecs_to_jiffies(call->peer->srtt_us >> 3);
116 else
117 ack_at = expiry;
118
119 ack_at += READ_ONCE(call->tx_backoff);
120 ack_at += now;
121 if (time_before(ack_at, call->ack_at)) {
122 WRITE_ONCE(call->ack_at, ack_at);
123 rxrpc_reduce_call_timer(call, ack_at, now,
124 rxrpc_timer_set_for_ack);
125 }
126 }
127
128 trace:
129 trace_rxrpc_propose_ack(call, why, ack_reason, serial, immediate,
130 background, outcome);
131 }
132
133 /*
134 * propose an ACK be sent, locking the call structure
135 */
rxrpc_propose_ACK(struct rxrpc_call * call,u8 ack_reason,u32 serial,bool immediate,bool background,enum rxrpc_propose_ack_trace why)136 void rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason,
137 u32 serial, bool immediate, bool background,
138 enum rxrpc_propose_ack_trace why)
139 {
140 spin_lock_bh(&call->lock);
141 __rxrpc_propose_ACK(call, ack_reason, serial,
142 immediate, background, why);
143 spin_unlock_bh(&call->lock);
144 }
145
146 /*
147 * Handle congestion being detected by the retransmit timeout.
148 */
rxrpc_congestion_timeout(struct rxrpc_call * call)149 static void rxrpc_congestion_timeout(struct rxrpc_call *call)
150 {
151 set_bit(RXRPC_CALL_RETRANS_TIMEOUT, &call->flags);
152 }
153
154 /*
155 * Perform retransmission of NAK'd and unack'd packets.
156 */
rxrpc_resend(struct rxrpc_call * call,unsigned long now_j)157 static void rxrpc_resend(struct rxrpc_call *call, unsigned long now_j)
158 {
159 struct sk_buff *skb;
160 unsigned long resend_at;
161 rxrpc_seq_t cursor, seq, top;
162 ktime_t now, max_age, oldest, ack_ts;
163 int ix;
164 u8 annotation, anno_type, retrans = 0, unacked = 0;
165
166 _enter("{%d,%d}", call->tx_hard_ack, call->tx_top);
167
168 now = ktime_get_real();
169 max_age = ktime_sub_us(now, jiffies_to_usecs(call->peer->rto_j));
170
171 spin_lock_bh(&call->lock);
172
173 cursor = call->tx_hard_ack;
174 top = call->tx_top;
175 ASSERT(before_eq(cursor, top));
176 if (cursor == top)
177 goto out_unlock;
178
179 /* Scan the packet list without dropping the lock and decide which of
180 * the packets in the Tx buffer we're going to resend and what the new
181 * resend timeout will be.
182 */
183 trace_rxrpc_resend(call, (cursor + 1) & RXRPC_RXTX_BUFF_MASK);
184 oldest = now;
185 for (seq = cursor + 1; before_eq(seq, top); seq++) {
186 ix = seq & RXRPC_RXTX_BUFF_MASK;
187 annotation = call->rxtx_annotations[ix];
188 anno_type = annotation & RXRPC_TX_ANNO_MASK;
189 annotation &= ~RXRPC_TX_ANNO_MASK;
190 if (anno_type == RXRPC_TX_ANNO_ACK)
191 continue;
192
193 skb = call->rxtx_buffer[ix];
194 rxrpc_see_skb(skb, rxrpc_skb_seen);
195
196 if (anno_type == RXRPC_TX_ANNO_UNACK) {
197 if (ktime_after(skb->tstamp, max_age)) {
198 if (ktime_before(skb->tstamp, oldest))
199 oldest = skb->tstamp;
200 continue;
201 }
202 if (!(annotation & RXRPC_TX_ANNO_RESENT))
203 unacked++;
204 }
205
206 /* Okay, we need to retransmit a packet. */
207 call->rxtx_annotations[ix] = RXRPC_TX_ANNO_RETRANS | annotation;
208 retrans++;
209 trace_rxrpc_retransmit(call, seq, annotation | anno_type,
210 ktime_to_ns(ktime_sub(skb->tstamp, max_age)));
211 }
212
213 resend_at = nsecs_to_jiffies(ktime_to_ns(ktime_sub(now, oldest)));
214 resend_at += jiffies + rxrpc_get_rto_backoff(call->peer, retrans);
215 WRITE_ONCE(call->resend_at, resend_at);
216
217 if (unacked)
218 rxrpc_congestion_timeout(call);
219
220 /* If there was nothing that needed retransmission then it's likely
221 * that an ACK got lost somewhere. Send a ping to find out instead of
222 * retransmitting data.
223 */
224 if (!retrans) {
225 rxrpc_reduce_call_timer(call, resend_at, now_j,
226 rxrpc_timer_set_for_resend);
227 spin_unlock_bh(&call->lock);
228 ack_ts = ktime_sub(now, call->acks_latest_ts);
229 if (ktime_to_us(ack_ts) < (call->peer->srtt_us >> 3))
230 goto out;
231 rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, true, false,
232 rxrpc_propose_ack_ping_for_lost_ack);
233 rxrpc_send_ack_packet(call, true, NULL);
234 goto out;
235 }
236
237 /* Now go through the Tx window and perform the retransmissions. We
238 * have to drop the lock for each send. If an ACK comes in whilst the
239 * lock is dropped, it may clear some of the retransmission markers for
240 * packets that it soft-ACKs.
241 */
242 for (seq = cursor + 1; before_eq(seq, top); seq++) {
243 ix = seq & RXRPC_RXTX_BUFF_MASK;
244 annotation = call->rxtx_annotations[ix];
245 anno_type = annotation & RXRPC_TX_ANNO_MASK;
246 if (anno_type != RXRPC_TX_ANNO_RETRANS)
247 continue;
248
249 /* We need to reset the retransmission state, but we need to do
250 * so before we drop the lock as a new ACK/NAK may come in and
251 * confuse things
252 */
253 annotation &= ~RXRPC_TX_ANNO_MASK;
254 annotation |= RXRPC_TX_ANNO_UNACK | RXRPC_TX_ANNO_RESENT;
255 call->rxtx_annotations[ix] = annotation;
256
257 skb = call->rxtx_buffer[ix];
258 if (!skb)
259 continue;
260
261 rxrpc_get_skb(skb, rxrpc_skb_got);
262 spin_unlock_bh(&call->lock);
263
264 if (rxrpc_send_data_packet(call, skb, true) < 0) {
265 rxrpc_free_skb(skb, rxrpc_skb_freed);
266 return;
267 }
268
269 if (rxrpc_is_client_call(call))
270 rxrpc_expose_client_call(call);
271
272 rxrpc_free_skb(skb, rxrpc_skb_freed);
273 spin_lock_bh(&call->lock);
274 if (after(call->tx_hard_ack, seq))
275 seq = call->tx_hard_ack;
276 }
277
278 out_unlock:
279 spin_unlock_bh(&call->lock);
280 out:
281 _leave("");
282 }
283
284 /*
285 * Handle retransmission and deferred ACK/abort generation.
286 */
rxrpc_process_call(struct work_struct * work)287 void rxrpc_process_call(struct work_struct *work)
288 {
289 struct rxrpc_call *call =
290 container_of(work, struct rxrpc_call, processor);
291 rxrpc_serial_t *send_ack;
292 unsigned long now, next, t;
293 unsigned int iterations = 0;
294
295 rxrpc_see_call(call);
296
297 //printk("\n--------------------\n");
298 _enter("{%d,%s,%lx}",
299 call->debug_id, rxrpc_call_states[call->state], call->events);
300
301 recheck_state:
302 /* Limit the number of times we do this before returning to the manager */
303 iterations++;
304 if (iterations > 5)
305 goto requeue;
306
307 if (test_and_clear_bit(RXRPC_CALL_EV_ABORT, &call->events)) {
308 rxrpc_send_abort_packet(call);
309 goto recheck_state;
310 }
311
312 if (call->state == RXRPC_CALL_COMPLETE) {
313 rxrpc_delete_call_timer(call);
314 goto out_put;
315 }
316
317 /* Work out if any timeouts tripped */
318 now = jiffies;
319 t = READ_ONCE(call->expect_rx_by);
320 if (time_after_eq(now, t)) {
321 trace_rxrpc_timer(call, rxrpc_timer_exp_normal, now);
322 set_bit(RXRPC_CALL_EV_EXPIRED, &call->events);
323 }
324
325 t = READ_ONCE(call->expect_req_by);
326 if (call->state == RXRPC_CALL_SERVER_RECV_REQUEST &&
327 time_after_eq(now, t)) {
328 trace_rxrpc_timer(call, rxrpc_timer_exp_idle, now);
329 set_bit(RXRPC_CALL_EV_EXPIRED, &call->events);
330 }
331
332 t = READ_ONCE(call->expect_term_by);
333 if (time_after_eq(now, t)) {
334 trace_rxrpc_timer(call, rxrpc_timer_exp_hard, now);
335 set_bit(RXRPC_CALL_EV_EXPIRED, &call->events);
336 }
337
338 t = READ_ONCE(call->ack_at);
339 if (time_after_eq(now, t)) {
340 trace_rxrpc_timer(call, rxrpc_timer_exp_ack, now);
341 cmpxchg(&call->ack_at, t, now + MAX_JIFFY_OFFSET);
342 set_bit(RXRPC_CALL_EV_ACK, &call->events);
343 }
344
345 t = READ_ONCE(call->ack_lost_at);
346 if (time_after_eq(now, t)) {
347 trace_rxrpc_timer(call, rxrpc_timer_exp_lost_ack, now);
348 cmpxchg(&call->ack_lost_at, t, now + MAX_JIFFY_OFFSET);
349 set_bit(RXRPC_CALL_EV_ACK_LOST, &call->events);
350 }
351
352 t = READ_ONCE(call->keepalive_at);
353 if (time_after_eq(now, t)) {
354 trace_rxrpc_timer(call, rxrpc_timer_exp_keepalive, now);
355 cmpxchg(&call->keepalive_at, t, now + MAX_JIFFY_OFFSET);
356 rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, true, true,
357 rxrpc_propose_ack_ping_for_keepalive);
358 set_bit(RXRPC_CALL_EV_PING, &call->events);
359 }
360
361 t = READ_ONCE(call->ping_at);
362 if (time_after_eq(now, t)) {
363 trace_rxrpc_timer(call, rxrpc_timer_exp_ping, now);
364 cmpxchg(&call->ping_at, t, now + MAX_JIFFY_OFFSET);
365 set_bit(RXRPC_CALL_EV_PING, &call->events);
366 }
367
368 t = READ_ONCE(call->resend_at);
369 if (time_after_eq(now, t)) {
370 trace_rxrpc_timer(call, rxrpc_timer_exp_resend, now);
371 cmpxchg(&call->resend_at, t, now + MAX_JIFFY_OFFSET);
372 set_bit(RXRPC_CALL_EV_RESEND, &call->events);
373 }
374
375 /* Process events */
376 if (test_and_clear_bit(RXRPC_CALL_EV_EXPIRED, &call->events)) {
377 if (test_bit(RXRPC_CALL_RX_HEARD, &call->flags) &&
378 (int)call->conn->hi_serial - (int)call->rx_serial > 0) {
379 trace_rxrpc_call_reset(call);
380 rxrpc_abort_call("EXP", call, 0, RX_CALL_DEAD, -ECONNRESET);
381 } else {
382 rxrpc_abort_call("EXP", call, 0, RX_CALL_TIMEOUT, -ETIME);
383 }
384 set_bit(RXRPC_CALL_EV_ABORT, &call->events);
385 goto recheck_state;
386 }
387
388 send_ack = NULL;
389 if (test_and_clear_bit(RXRPC_CALL_EV_ACK_LOST, &call->events)) {
390 call->acks_lost_top = call->tx_top;
391 rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, true, false,
392 rxrpc_propose_ack_ping_for_lost_ack);
393 send_ack = &call->acks_lost_ping;
394 }
395
396 if (test_and_clear_bit(RXRPC_CALL_EV_ACK, &call->events) ||
397 send_ack) {
398 if (call->ackr_reason) {
399 rxrpc_send_ack_packet(call, false, send_ack);
400 goto recheck_state;
401 }
402 }
403
404 if (test_and_clear_bit(RXRPC_CALL_EV_PING, &call->events)) {
405 rxrpc_send_ack_packet(call, true, NULL);
406 goto recheck_state;
407 }
408
409 if (test_and_clear_bit(RXRPC_CALL_EV_RESEND, &call->events) &&
410 call->state != RXRPC_CALL_CLIENT_RECV_REPLY) {
411 rxrpc_resend(call, now);
412 goto recheck_state;
413 }
414
415 /* Make sure the timer is restarted */
416 next = call->expect_rx_by;
417
418 #define set(T) { t = READ_ONCE(T); if (time_before(t, next)) next = t; }
419
420 set(call->expect_req_by);
421 set(call->expect_term_by);
422 set(call->ack_at);
423 set(call->ack_lost_at);
424 set(call->resend_at);
425 set(call->keepalive_at);
426 set(call->ping_at);
427
428 now = jiffies;
429 if (time_after_eq(now, next))
430 goto recheck_state;
431
432 rxrpc_reduce_call_timer(call, next, now, rxrpc_timer_restart);
433
434 /* other events may have been raised since we started checking */
435 if (call->events && call->state < RXRPC_CALL_COMPLETE)
436 goto requeue;
437
438 out_put:
439 rxrpc_put_call(call, rxrpc_call_put);
440 out:
441 _leave("");
442 return;
443
444 requeue:
445 __rxrpc_queue_call(call);
446 goto out;
447 }
448