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         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_local *local = call->conn->params.local;
  73         struct rxrpc_txbuf *txb;
  74
  75         if (test_bit(RXRPC_CALL_DISCONNECTED, &call->flags))
  76                 return;
  77         if (ack_reason == RXRPC_ACK_DELAY &&
  78             test_and_set_bit(RXRPC_CALL_DELAY_ACK_PENDING, &call->flags)) {
  79                 trace_rxrpc_drop_ack(call, why, ack_reason, serial, false);
  80                 return;
  81         }
  82
  83         rxrpc_inc_stat(call->rxnet, stat_tx_acks[ack_reason]);
  84
  85         txb = rxrpc_alloc_txbuf(call, RXRPC_PACKET_TYPE_ACK,
  86                                 in_softirq() ? GFP_ATOMIC | __GFP_NOWARN : GFP_NOFS);
  87         if (!txb) {
  88                 kleave(" = -ENOMEM");
  89                 return;
  90         }
  91
  92         txb->ack_why            = why;
  93         txb->wire.seq           = 0;
  94         txb->wire.type          = RXRPC_PACKET_TYPE_ACK;
  95         txb->wire.flags         |= RXRPC_SLOW_START_OK;
  96         txb->ack.bufferSpace    = 0;
  97         txb->ack.maxSkew        = 0;
  98         txb->ack.firstPacket    = 0;
  99         txb->ack.previousPacket = 0;
 100         txb->ack.serial         = htonl(serial);
 101         txb->ack.reason         = ack_reason;
 102         txb->ack.nAcks          = 0;
 103
 104         if (!rxrpc_try_get_call(call, rxrpc_call_got)) {
 105                 rxrpc_put_txbuf(txb, rxrpc_txbuf_put_nomem);
 106                 return;
 107         }
 108
 109         spin_lock_bh(&local->ack_tx_lock);
 110         list_add_tail(&txb->tx_link, &local->ack_tx_queue);
 111         spin_unlock_bh(&local->ack_tx_lock);
 112         trace_rxrpc_send_ack(call, why, ack_reason, serial);
 113
 114         if (in_task()) {
 115                 rxrpc_transmit_ack_packets(call->peer->local);
 116         } else {
 117                 rxrpc_get_local(local);
 118                 rxrpc_queue_local(local);
 119         }
 120 }
 121
 122 /*
 123  * Handle congestion being detected by the retransmit timeout.
 124  */
 125 static void rxrpc_congestion_timeout(struct rxrpc_call *call)
 126 {
 127         set_bit(RXRPC_CALL_RETRANS_TIMEOUT, &call->flags);
 128 }
 129
 130 /*
 131  * Perform retransmission of NAK'd and unack'd packets.
 132  */
 133 static void rxrpc_resend(struct rxrpc_call *call, unsigned long now_j)
 134 {
 135         struct rxrpc_ackpacket *ack = NULL;
 136         struct rxrpc_txbuf *txb;
 137         struct sk_buff *ack_skb = NULL;
 138         unsigned long resend_at;
 139         rxrpc_seq_t transmitted = READ_ONCE(call->tx_transmitted);
 140         ktime_t now, max_age, oldest, ack_ts;
 141         bool unacked = false;
 142         unsigned int i;
 143         LIST_HEAD(retrans_queue);
 144
 145         _enter("{%d,%d}", call->acks_hard_ack, call->tx_top);
 146
 147         now = ktime_get_real();
 148         max_age = ktime_sub_us(now, jiffies_to_usecs(call->peer->rto_j));
 149         oldest = now;
 150
 151         /* See if there's an ACK saved with a soft-ACK table in it. */
 152         if (call->acks_soft_tbl) {
 153                 spin_lock_bh(&call->acks_ack_lock);
 154                 ack_skb = call->acks_soft_tbl;
 155                 if (ack_skb) {
 156                         rxrpc_get_skb(ack_skb, rxrpc_skb_ack);
 157                         ack = (void *)ack_skb->data + sizeof(struct rxrpc_wire_header);
 158                 }
 159                 spin_unlock_bh(&call->acks_ack_lock);
 160         }
 161
 162         if (list_empty(&call->tx_buffer))
 163                 goto no_resend;
 164
 165         spin_lock(&call->tx_lock);
 166
 167         if (list_empty(&call->tx_buffer))
 168                 goto no_further_resend;
 169
 170         trace_rxrpc_resend(call);
 171         txb = list_first_entry(&call->tx_buffer, struct rxrpc_txbuf, call_link);
 172
 173         /* Scan the soft ACK table without dropping the lock and resend any
 174          * explicitly NAK'd packets.
 175          */
 176         if (ack) {
 177                 for (i = 0; i < ack->nAcks; i++) {
 178                         rxrpc_seq_t seq;
 179
 180                         if (ack->acks[i] & 1)
 181                                 continue;
 182                         seq = ntohl(ack->firstPacket) + i;
 183                         if (after(txb->seq, transmitted))
 184                                 break;
 185                         if (after(txb->seq, seq))
 186                                 continue; /* A new hard ACK probably came in */
 187                         list_for_each_entry_from(txb, &call->tx_buffer, call_link) {
 188                                 if (txb->seq == seq)
 189                                         goto found_txb;
 190                         }
 191                         goto no_further_resend;
 192
 193                 found_txb:
 194                         if (after(ntohl(txb->wire.serial), call->acks_highest_serial))
 195                                 continue; /* Ack point not yet reached */
 196
 197                         rxrpc_see_txbuf(txb, rxrpc_txbuf_see_unacked);
 198
 199                         if (list_empty(&txb->tx_link)) {
 200                                 rxrpc_get_txbuf(txb, rxrpc_txbuf_get_retrans);
 201                                 list_add_tail(&txb->tx_link, &retrans_queue);
 202                                 set_bit(RXRPC_TXBUF_RESENT, &txb->flags);
 203                         }
 204
 205                         trace_rxrpc_retransmit(call, txb->seq,
 206                                                ktime_to_ns(ktime_sub(txb->last_sent,
 207                                                                      max_age)));
 208
 209                         if (list_is_last(&txb->call_link, &call->tx_buffer))
 210                                 goto no_further_resend;
 211                         txb = list_next_entry(txb, call_link);
 212                 }
 213         }
 214
 215         /* Fast-forward through the Tx queue to the point the peer says it has
 216          * seen.  Anything between the soft-ACK table and that point will get
 217          * ACK'd or NACK'd in due course, so don't worry about it here; here we
 218          * need to consider retransmitting anything beyond that point.
 219          *
 220          * Note that ACK for a packet can beat the update of tx_transmitted.
 221          */
 222         if (after_eq(READ_ONCE(call->acks_prev_seq), READ_ONCE(call->tx_transmitted)))
 223                 goto no_further_resend;
 224
 225         list_for_each_entry_from(txb, &call->tx_buffer, call_link) {
 226                 if (before_eq(txb->seq, READ_ONCE(call->acks_prev_seq)))
 227                         continue;
 228                 if (after(txb->seq, READ_ONCE(call->tx_transmitted)))
 229                         break; /* Not transmitted yet */
 230
 231                 if (ack && ack->reason == RXRPC_ACK_PING_RESPONSE &&
 232                     before(ntohl(txb->wire.serial), ntohl(ack->serial)))
 233                         goto do_resend; /* Wasn't accounted for by a more recent ping. */
 234
 235                 if (ktime_after(txb->last_sent, max_age)) {
 236                         if (ktime_before(txb->last_sent, oldest))
 237                                 oldest = txb->last_sent;
 238                         continue;
 239                 }
 240
 241         do_resend:
 242                 unacked = true;
 243                 if (list_empty(&txb->tx_link)) {
 244                         rxrpc_get_txbuf(txb, rxrpc_txbuf_get_retrans);
 245                         list_add_tail(&txb->tx_link, &retrans_queue);
 246                         set_bit(RXRPC_TXBUF_RESENT, &txb->flags);
 247                         rxrpc_inc_stat(call->rxnet, stat_tx_data_retrans);
 248                 }
 249         }
 250
 251 no_further_resend:
 252         spin_unlock(&call->tx_lock);
 253 no_resend:
 254         rxrpc_free_skb(ack_skb, rxrpc_skb_freed);
 255
 256         resend_at = nsecs_to_jiffies(ktime_to_ns(ktime_sub(now, oldest)));
 257         resend_at += jiffies + rxrpc_get_rto_backoff(call->peer,
 258                                                      !list_empty(&retrans_queue));
 259         WRITE_ONCE(call->resend_at, resend_at);
 260
 261         if (unacked)
 262                 rxrpc_congestion_timeout(call);
 263
 264         /* If there was nothing that needed retransmission then it's likely
 265          * that an ACK got lost somewhere.  Send a ping to find out instead of
 266          * retransmitting data.
 267          */
 268         if (list_empty(&retrans_queue)) {
 269                 rxrpc_reduce_call_timer(call, resend_at, now_j,
 270                                         rxrpc_timer_set_for_resend);
 271                 ack_ts = ktime_sub(now, call->acks_latest_ts);
 272                 if (ktime_to_us(ack_ts) < (call->peer->srtt_us >> 3))
 273                         goto out;
 274                 rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
 275                                rxrpc_propose_ack_ping_for_lost_ack);
 276                 goto out;
 277         }
 278
 279         while ((txb = list_first_entry_or_null(&retrans_queue,
 280                                                struct rxrpc_txbuf, tx_link))) {
 281                 list_del_init(&txb->tx_link);
 282                 rxrpc_send_data_packet(call, txb);
 283                 rxrpc_put_txbuf(txb, rxrpc_txbuf_put_trans);
 284
 285                 trace_rxrpc_retransmit(call, txb->seq,
 286                                        ktime_to_ns(ktime_sub(txb->last_sent,
 287                                                              max_age)));
 288         }
 289
 290 out:
 291         _leave("");
 292 }
 293
 294 /*
 295  * Handle retransmission and deferred ACK/abort generation.
 296  */
 297 void rxrpc_process_call(struct work_struct *work)
 298 {
 299         struct rxrpc_call *call =
 300                 container_of(work, struct rxrpc_call, processor);
 301         unsigned long now, next, t;
 302         unsigned int iterations = 0;
 303         rxrpc_serial_t ackr_serial;
 304
 305         rxrpc_see_call(call);
 306
 307         //printk("\n--------------------\n");
 308         _enter("{%d,%s,%lx}",
 309                call->debug_id, rxrpc_call_states[call->state], call->events);
 310
 311 recheck_state:
 312         /* Limit the number of times we do this before returning to the manager */
 313         iterations++;
 314         if (iterations > 5)
 315                 goto requeue;
 316
 317         if (test_and_clear_bit(RXRPC_CALL_EV_ABORT, &call->events)) {
 318                 rxrpc_send_abort_packet(call);
 319                 goto recheck_state;
 320         }
 321
 322         if (READ_ONCE(call->acks_hard_ack) != call->tx_bottom)
 323                 rxrpc_shrink_call_tx_buffer(call);
 324
 325         if (call->state == RXRPC_CALL_COMPLETE) {
 326                 rxrpc_delete_call_timer(call);
 327                 goto out_put;
 328         }
 329
 330         /* Work out if any timeouts tripped */
 331         now = jiffies;
 332         t = READ_ONCE(call->expect_rx_by);
 333         if (time_after_eq(now, t)) {
 334                 trace_rxrpc_timer(call, rxrpc_timer_exp_normal, now);
 335                 set_bit(RXRPC_CALL_EV_EXPIRED, &call->events);
 336         }
 337
 338         t = READ_ONCE(call->expect_req_by);
 339         if (call->state == RXRPC_CALL_SERVER_RECV_REQUEST &&
 340             time_after_eq(now, t)) {
 341                 trace_rxrpc_timer(call, rxrpc_timer_exp_idle, now);
 342                 set_bit(RXRPC_CALL_EV_EXPIRED, &call->events);
 343         }
 344
 345         t = READ_ONCE(call->expect_term_by);
 346         if (time_after_eq(now, t)) {
 347                 trace_rxrpc_timer(call, rxrpc_timer_exp_hard, now);
 348                 set_bit(RXRPC_CALL_EV_EXPIRED, &call->events);
 349         }
 350
 351         t = READ_ONCE(call->delay_ack_at);
 352         if (time_after_eq(now, t)) {
 353                 trace_rxrpc_timer(call, rxrpc_timer_exp_ack, now);
 354                 cmpxchg(&call->delay_ack_at, t, now + MAX_JIFFY_OFFSET);
 355                 ackr_serial = xchg(&call->ackr_serial, 0);
 356                 rxrpc_send_ACK(call, RXRPC_ACK_DELAY, ackr_serial,
 357                                rxrpc_propose_ack_ping_for_lost_ack);
 358         }
 359
 360         t = READ_ONCE(call->ack_lost_at);
 361         if (time_after_eq(now, t)) {
 362                 trace_rxrpc_timer(call, rxrpc_timer_exp_lost_ack, now);
 363                 cmpxchg(&call->ack_lost_at, t, now + MAX_JIFFY_OFFSET);
 364                 set_bit(RXRPC_CALL_EV_ACK_LOST, &call->events);
 365         }
 366
 367         t = READ_ONCE(call->keepalive_at);
 368         if (time_after_eq(now, t)) {
 369                 trace_rxrpc_timer(call, rxrpc_timer_exp_keepalive, now);
 370                 cmpxchg(&call->keepalive_at, t, now + MAX_JIFFY_OFFSET);
 371                 rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
 372                                rxrpc_propose_ack_ping_for_keepalive);
 373         }
 374
 375         t = READ_ONCE(call->ping_at);
 376         if (time_after_eq(now, t)) {
 377                 trace_rxrpc_timer(call, rxrpc_timer_exp_ping, now);
 378                 cmpxchg(&call->ping_at, t, now + MAX_JIFFY_OFFSET);
 379                 rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
 380                                rxrpc_propose_ack_ping_for_keepalive);
 381         }
 382
 383         t = READ_ONCE(call->resend_at);
 384         if (time_after_eq(now, t)) {
 385                 trace_rxrpc_timer(call, rxrpc_timer_exp_resend, now);
 386                 cmpxchg(&call->resend_at, t, now + MAX_JIFFY_OFFSET);
 387                 set_bit(RXRPC_CALL_EV_RESEND, &call->events);
 388         }
 389
 390         /* Process events */
 391         if (test_and_clear_bit(RXRPC_CALL_EV_EXPIRED, &call->events)) {
 392                 if (test_bit(RXRPC_CALL_RX_HEARD, &call->flags) &&
 393                     (int)call->conn->hi_serial - (int)call->rx_serial > 0) {
 394                         trace_rxrpc_call_reset(call);
 395                         rxrpc_abort_call("EXP", call, 0, RX_CALL_DEAD, -ECONNRESET);
 396                 } else {
 397                         rxrpc_abort_call("EXP", call, 0, RX_CALL_TIMEOUT, -ETIME);
 398                 }
 399                 set_bit(RXRPC_CALL_EV_ABORT, &call->events);
 400                 goto recheck_state;
 401         }
 402
 403         if (test_and_clear_bit(RXRPC_CALL_EV_ACK_LOST, &call->events)) {
 404                 call->acks_lost_top = call->tx_top;
 405                 rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
 406                                rxrpc_propose_ack_ping_for_lost_ack);
 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->delay_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 }