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 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  */
  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  */
 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  */
 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  */
 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(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  */
 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 }