net/rxrpc/call_event.c

   1 /* Management of Tx window, Tx resend, ACKs and out-of-sequence reception
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  13
  14 #include <linux/module.h>
  15 #include <linux/circ_buf.h>
  16 #include <linux/net.h>
  17 #include <linux/skbuff.h>
  18 #include <linux/slab.h>
  19 #include <linux/udp.h>
  20 #include <net/sock.h>
  21 #include <net/af_rxrpc.h>
  22 #include "ar-internal.h"
  23
  24 /*
  25  * Set the timer
  26  */
  27 void rxrpc_set_timer(struct rxrpc_call *call, enum rxrpc_timer_trace why)
  28 {
  29         unsigned long t, now = jiffies;
  30
  31         read_lock_bh(&call->state_lock);
  32
  33         if (call->state < RXRPC_CALL_COMPLETE) {
  34                 t = call->expire_at;
  35                 if (time_before_eq(t, now))
  36                         goto out;
  37
  38                 if (time_after(call->resend_at, now) &&
  39                     time_before(call->resend_at, t))
  40                         t = call->resend_at;
  41
  42                 if (time_after(call->ack_at, now) &&
  43                     time_before(call->ack_at, t))
  44                         t = call->ack_at;
  45
  46                 if (call->timer.expires != t || !timer_pending(&call->timer)) {
  47                         mod_timer(&call->timer, t);
  48                         trace_rxrpc_timer(call, why, now);
  49                 }
  50         }
  51
  52 out:
  53         read_unlock_bh(&call->state_lock);
  54 }
  55
  56 /*
  57  * propose an ACK be sent
  58  */
  59 static void __rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason,
  60                                 u16 skew, u32 serial, bool immediate,
  61                                 bool background,
  62                                 enum rxrpc_propose_ack_trace why)
  63 {
  64         enum rxrpc_propose_ack_outcome outcome = rxrpc_propose_ack_use;
  65         unsigned long now, ack_at, expiry = rxrpc_soft_ack_delay;
  66         s8 prior = rxrpc_ack_priority[ack_reason];
  67
  68         /* Update DELAY, IDLE, REQUESTED and PING_RESPONSE ACK serial
  69          * numbers, but we don't alter the timeout.
  70          */
  71         _debug("prior %u %u vs %u %u",
  72                ack_reason, prior,
  73                call->ackr_reason, rxrpc_ack_priority[call->ackr_reason]);
  74         if (ack_reason == call->ackr_reason) {
  75                 if (RXRPC_ACK_UPDATEABLE & (1 << ack_reason)) {
  76                         outcome = rxrpc_propose_ack_update;
  77                         call->ackr_serial = serial;
  78                         call->ackr_skew = skew;
  79                 }
  80                 if (!immediate)
  81                         goto trace;
  82         } else if (prior > rxrpc_ack_priority[call->ackr_reason]) {
  83                 call->ackr_reason = ack_reason;
  84                 call->ackr_serial = serial;
  85                 call->ackr_skew = skew;
  86         } else {
  87                 outcome = rxrpc_propose_ack_subsume;
  88         }
  89
  90         switch (ack_reason) {
  91         case RXRPC_ACK_REQUESTED:
  92                 if (rxrpc_requested_ack_delay < expiry)
  93                         expiry = rxrpc_requested_ack_delay;
  94                 if (serial == 1)
  95                         immediate = false;
  96                 break;
  97
  98         case RXRPC_ACK_DELAY:
  99                 if (rxrpc_soft_ack_delay < expiry)
 100                         expiry = rxrpc_soft_ack_delay;
 101                 break;
 102
 103         case RXRPC_ACK_PING:
 104         case RXRPC_ACK_IDLE:
 105                 if (rxrpc_idle_ack_delay < expiry)
 106                         expiry = rxrpc_idle_ack_delay;
 107                 break;
 108
 109         default:
 110                 immediate = true;
 111                 break;
 112         }
 113
 114         now = jiffies;
 115         if (test_bit(RXRPC_CALL_EV_ACK, &call->events)) {
 116                 _debug("already scheduled");
 117         } else if (immediate || expiry == 0) {
 118                 _debug("immediate ACK %lx", call->events);
 119                 if (!test_and_set_bit(RXRPC_CALL_EV_ACK, &call->events) &&
 120                     background)
 121                         rxrpc_queue_call(call);
 122         } else {
 123                 ack_at = now + expiry;
 124                 _debug("deferred ACK %ld < %ld", expiry, call->ack_at - now);
 125                 if (time_before(ack_at, call->ack_at)) {
 126                         call->ack_at = ack_at;
 127                         rxrpc_set_timer(call, rxrpc_timer_set_for_ack);
 128                 }
 129         }
 130
 131 trace:
 132         trace_rxrpc_propose_ack(call, why, ack_reason, serial, immediate,
 133                                 background, outcome);
 134 }
 135
 136 /*
 137  * propose an ACK be sent, locking the call structure
 138  */
 139 void rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason,
 140                        u16 skew, u32 serial, bool immediate, bool background,
 141                        enum rxrpc_propose_ack_trace why)
 142 {
 143         spin_lock_bh(&call->lock);
 144         __rxrpc_propose_ACK(call, ack_reason, skew, serial,
 145                             immediate, background, why);
 146         spin_unlock_bh(&call->lock);
 147 }
 148
 149 /*
 150  * Handle congestion being detected by the retransmit timeout.
 151  */
 152 static void rxrpc_congestion_timeout(struct rxrpc_call *call)
 153 {
 154         set_bit(RXRPC_CALL_RETRANS_TIMEOUT, &call->flags);
 155 }
 156
 157 /*
 158  * Perform retransmission of NAK'd and unack'd packets.
 159  */
 160 static void rxrpc_resend(struct rxrpc_call *call)
 161 {
 162         struct rxrpc_skb_priv *sp;
 163         struct sk_buff *skb;
 164         rxrpc_seq_t cursor, seq, top;
 165         ktime_t now = ktime_get_real(), max_age, oldest, resend_at, ack_ts;
 166         int ix;
 167         u8 annotation, anno_type, retrans = 0, unacked = 0;
 168
 169         _enter("{%d,%d}", call->tx_hard_ack, call->tx_top);
 170
 171         max_age = ktime_sub_ms(now, rxrpc_resend_timeout);
 172
 173         spin_lock_bh(&call->lock);
 174
 175         cursor = call->tx_hard_ack;
 176         top = call->tx_top;
 177         ASSERT(before_eq(cursor, top));
 178         if (cursor == top)
 179                 goto out_unlock;
 180
 181         /* Scan the packet list without dropping the lock and decide which of
 182          * the packets in the Tx buffer we're going to resend and what the new
 183          * resend timeout will be.
 184          */
 185         oldest = now;
 186         for (seq = cursor + 1; before_eq(seq, top); seq++) {
 187                 ix = seq & RXRPC_RXTX_BUFF_MASK;
 188                 annotation = call->rxtx_annotations[ix];
 189                 anno_type = annotation & RXRPC_TX_ANNO_MASK;
 190                 annotation &= ~RXRPC_TX_ANNO_MASK;
 191                 if (anno_type == RXRPC_TX_ANNO_ACK)
 192                         continue;
 193
 194                 skb = call->rxtx_buffer[ix];
 195                 rxrpc_see_skb(skb, rxrpc_skb_tx_seen);
 196                 sp = rxrpc_skb(skb);
 197
 198                 if (anno_type == RXRPC_TX_ANNO_UNACK) {
 199                         if (ktime_after(skb->tstamp, max_age)) {
 200                                 if (ktime_before(skb->tstamp, oldest))
 201                                         oldest = skb->tstamp;
 202                                 continue;
 203                         }
 204                         if (!(annotation & RXRPC_TX_ANNO_RESENT))
 205                                 unacked++;
 206                 }
 207
 208                 /* Okay, we need to retransmit a packet. */
 209                 call->rxtx_annotations[ix] = RXRPC_TX_ANNO_RETRANS | annotation;
 210                 retrans++;
 211                 trace_rxrpc_retransmit(call, seq, annotation | anno_type,
 212                                        ktime_to_ns(ktime_sub(skb->tstamp, max_age)));
 213         }
 214
 215         resend_at = ktime_add_ms(oldest, rxrpc_resend_timeout);
 216         call->resend_at = jiffies +
 217                 nsecs_to_jiffies(ktime_to_ns(ktime_sub(resend_at, now))) +
 218                 1; /* We have to make sure that the calculated jiffies value
 219                     * falls at or after the nsec value, or we shall loop
 220                     * ceaselessly because the timer times out, but we haven't
 221                     * reached the nsec timeout yet.
 222                     */
 223
 224         if (unacked)
 225                 rxrpc_congestion_timeout(call);
 226
 227         /* If there was nothing that needed retransmission then it's likely
 228          * that an ACK got lost somewhere.  Send a ping to find out instead of
 229          * retransmitting data.
 230          */
 231         if (!retrans) {
 232                 rxrpc_set_timer(call, rxrpc_timer_set_for_resend);
 233                 spin_unlock_bh(&call->lock);
 234                 ack_ts = ktime_sub(now, call->acks_latest_ts);
 235                 if (ktime_to_ns(ack_ts) < call->peer->rtt)
 236                         goto out;
 237                 rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, 0, true, false,
 238                                   rxrpc_propose_ack_ping_for_lost_ack);
 239                 rxrpc_send_call_packet(call, RXRPC_PACKET_TYPE_ACK);
 240                 goto out;
 241         }
 242
 243         /* Now go through the Tx window and perform the retransmissions.  We
 244          * have to drop the lock for each send.  If an ACK comes in whilst the
 245          * lock is dropped, it may clear some of the retransmission markers for
 246          * packets that it soft-ACKs.
 247          */
 248         for (seq = cursor + 1; before_eq(seq, top); seq++) {
 249                 ix = seq & RXRPC_RXTX_BUFF_MASK;
 250                 annotation = call->rxtx_annotations[ix];
 251                 anno_type = annotation & RXRPC_TX_ANNO_MASK;
 252                 if (anno_type != RXRPC_TX_ANNO_RETRANS)
 253                         continue;
 254
 255                 skb = call->rxtx_buffer[ix];
 256                 rxrpc_get_skb(skb, rxrpc_skb_tx_got);
 257                 spin_unlock_bh(&call->lock);
 258
 259                 if (rxrpc_send_data_packet(call, skb) < 0) {
 260                         rxrpc_free_skb(skb, rxrpc_skb_tx_freed);
 261                         return;
 262                 }
 263
 264                 if (rxrpc_is_client_call(call))
 265                         rxrpc_expose_client_call(call);
 266
 267                 rxrpc_free_skb(skb, rxrpc_skb_tx_freed);
 268                 spin_lock_bh(&call->lock);
 269
 270                 /* We need to clear the retransmit state, but there are two
 271                  * things we need to be aware of: A new ACK/NAK might have been
 272                  * received and the packet might have been hard-ACK'd (in which
 273                  * case it will no longer be in the buffer).
 274                  */
 275                 if (after(seq, call->tx_hard_ack)) {
 276                         annotation = call->rxtx_annotations[ix];
 277                         anno_type = annotation & RXRPC_TX_ANNO_MASK;
 278                         if (anno_type == RXRPC_TX_ANNO_RETRANS ||
 279                             anno_type == RXRPC_TX_ANNO_NAK) {
 280                                 annotation &= ~RXRPC_TX_ANNO_MASK;
 281                                 annotation |= RXRPC_TX_ANNO_UNACK;
 282                         }
 283                         annotation |= RXRPC_TX_ANNO_RESENT;
 284                         call->rxtx_annotations[ix] = annotation;
 285                 }
 286
 287                 if (after(call->tx_hard_ack, seq))
 288                         seq = call->tx_hard_ack;
 289         }
 290
 291 out_unlock:
 292         spin_unlock_bh(&call->lock);
 293 out:
 294         _leave("");
 295 }
 296
 297 /*
 298  * Handle retransmission and deferred ACK/abort generation.
 299  */
 300 void rxrpc_process_call(struct work_struct *work)
 301 {
 302         struct rxrpc_call *call =
 303                 container_of(work, struct rxrpc_call, processor);
 304         unsigned long now;
 305
 306         rxrpc_see_call(call);
 307
 308         //printk("\n--------------------\n");
 309         _enter("{%d,%s,%lx}",
 310                call->debug_id, rxrpc_call_states[call->state], call->events);
 311
 312 recheck_state:
 313         if (test_and_clear_bit(RXRPC_CALL_EV_ABORT, &call->events)) {
 314                 rxrpc_send_call_packet(call, RXRPC_PACKET_TYPE_ABORT);
 315                 goto recheck_state;
 316         }
 317
 318         if (call->state == RXRPC_CALL_COMPLETE) {
 319                 del_timer_sync(&call->timer);
 320                 goto out_put;
 321         }
 322
 323         now = jiffies;
 324         if (time_after_eq(now, call->expire_at)) {
 325                 rxrpc_abort_call("EXP", call, 0, RX_CALL_TIMEOUT, ETIME);
 326                 set_bit(RXRPC_CALL_EV_ABORT, &call->events);
 327                 goto recheck_state;
 328         }
 329
 330         if (test_and_clear_bit(RXRPC_CALL_EV_ACK, &call->events) ||
 331             time_after_eq(now, call->ack_at)) {
 332                 call->ack_at = call->expire_at;
 333                 if (call->ackr_reason) {
 334                         rxrpc_send_call_packet(call, RXRPC_PACKET_TYPE_ACK);
 335                         goto recheck_state;
 336                 }
 337         }
 338
 339         if (test_and_clear_bit(RXRPC_CALL_EV_RESEND, &call->events) ||
 340             time_after_eq(now, call->resend_at)) {
 341                 rxrpc_resend(call);
 342                 goto recheck_state;
 343         }
 344
 345         rxrpc_set_timer(call, rxrpc_timer_set_for_resend);
 346
 347         /* other events may have been raised since we started checking */
 348         if (call->events && call->state < RXRPC_CALL_COMPLETE) {
 349                 __rxrpc_queue_call(call);
 350                 goto out;
 351         }
 352
 353 out_put:
 354         rxrpc_put_call(call, rxrpc_call_put);
 355 out:
 356         _leave("");
 357 }