net/rxrpc/call_event.c

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