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                      ktime_t now)
  29 {
  30         unsigned long t_j, now_j = jiffies;
  31         ktime_t t;
  32         bool queue = false;
  33
  34         read_lock_bh(&call->state_lock);
  35
  36         if (call->state < RXRPC_CALL_COMPLETE) {
  37                 t = call->expire_at;
  38                 if (!ktime_after(t, now))
  39                         goto out;
  40
  41                 if (!ktime_after(call->resend_at, now)) {
  42                         call->resend_at = call->expire_at;
  43                         if (!test_and_set_bit(RXRPC_CALL_EV_RESEND, &call->events))
  44                                 queue = true;
  45                 } else if (ktime_before(call->resend_at, t)) {
  46                         t = call->resend_at;
  47                 }
  48
  49                 if (!ktime_after(call->ack_at, now)) {
  50                         call->ack_at = call->expire_at;
  51                         if (!test_and_set_bit(RXRPC_CALL_EV_ACK, &call->events))
  52                                 queue = true;
  53                 } else if (ktime_before(call->ack_at, t)) {
  54                         t = call->ack_at;
  55                 }
  56
  57                 t_j = nsecs_to_jiffies(ktime_to_ns(ktime_sub(t, now)));
  58                 t_j += jiffies;
  59
  60                 /* We have to make sure that the calculated jiffies value falls
  61                  * at or after the nsec value, or we may loop ceaselessly
  62                  * because the timer times out, but we haven't reached the nsec
  63                  * timeout yet.
  64                  */
  65                 t_j++;
  66
  67                 if (call->timer.expires != t_j || !timer_pending(&call->timer)) {
  68                         mod_timer(&call->timer, t_j);
  69                         trace_rxrpc_timer(call, why, now, now_j);
  70                 }
  71
  72                 if (queue)
  73                         rxrpc_queue_call(call);
  74         }
  75
  76 out:
  77         read_unlock_bh(&call->state_lock);
  78 }
  79
  80 /*
  81  * propose an ACK be sent
  82  */
  83 static void __rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason,
  84                                 u16 skew, u32 serial, bool immediate,
  85                                 bool background,
  86                                 enum rxrpc_propose_ack_trace why)
  87 {
  88         enum rxrpc_propose_ack_outcome outcome = rxrpc_propose_ack_use;
  89         unsigned int expiry = rxrpc_soft_ack_delay;
  90         ktime_t now, ack_at;
  91         s8 prior = rxrpc_ack_priority[ack_reason];
  92
  93         /* Update DELAY, IDLE, REQUESTED and PING_RESPONSE ACK serial
  94          * numbers, but we don't alter the timeout.
  95          */
  96         _debug("prior %u %u vs %u %u",
  97                ack_reason, prior,
  98                call->ackr_reason, rxrpc_ack_priority[call->ackr_reason]);
  99         if (ack_reason == call->ackr_reason) {
 100                 if (RXRPC_ACK_UPDATEABLE & (1 << ack_reason)) {
 101                         outcome = rxrpc_propose_ack_update;
 102                         call->ackr_serial = serial;
 103                         call->ackr_skew = skew;
 104                 }
 105                 if (!immediate)
 106                         goto trace;
 107         } else if (prior > rxrpc_ack_priority[call->ackr_reason]) {
 108                 call->ackr_reason = ack_reason;
 109                 call->ackr_serial = serial;
 110                 call->ackr_skew = skew;
 111         } else {
 112                 outcome = rxrpc_propose_ack_subsume;
 113         }
 114
 115         switch (ack_reason) {
 116         case RXRPC_ACK_REQUESTED:
 117                 if (rxrpc_requested_ack_delay < expiry)
 118                         expiry = rxrpc_requested_ack_delay;
 119                 if (serial == 1)
 120                         immediate = false;
 121                 break;
 122
 123         case RXRPC_ACK_DELAY:
 124                 if (rxrpc_soft_ack_delay < expiry)
 125                         expiry = rxrpc_soft_ack_delay;
 126                 break;
 127
 128         case RXRPC_ACK_PING:
 129         case RXRPC_ACK_IDLE:
 130                 if (rxrpc_idle_ack_delay < expiry)
 131                         expiry = rxrpc_idle_ack_delay;
 132                 break;
 133
 134         default:
 135                 immediate = true;
 136                 break;
 137         }
 138
 139         if (test_bit(RXRPC_CALL_EV_ACK, &call->events)) {
 140                 _debug("already scheduled");
 141         } else if (immediate || expiry == 0) {
 142                 _debug("immediate ACK %lx", call->events);
 143                 if (!test_and_set_bit(RXRPC_CALL_EV_ACK, &call->events) &&
 144                     background)
 145                         rxrpc_queue_call(call);
 146         } else {
 147                 now = ktime_get_real();
 148                 ack_at = ktime_add_ms(now, expiry);
 149                 if (ktime_before(ack_at, call->ack_at)) {
 150                         call->ack_at = ack_at;
 151                         rxrpc_set_timer(call, rxrpc_timer_set_for_ack, now);
 152                 }
 153         }
 154
 155 trace:
 156         trace_rxrpc_propose_ack(call, why, ack_reason, serial, immediate,
 157                                 background, outcome);
 158 }
 159
 160 /*
 161  * propose an ACK be sent, locking the call structure
 162  */
 163 void rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason,
 164                        u16 skew, u32 serial, bool immediate, bool background,
 165                        enum rxrpc_propose_ack_trace why)
 166 {
 167         spin_lock_bh(&call->lock);
 168         __rxrpc_propose_ACK(call, ack_reason, skew, serial,
 169                             immediate, background, why);
 170         spin_unlock_bh(&call->lock);
 171 }
 172
 173 /*
 174  * Handle congestion being detected by the retransmit timeout.
 175  */
 176 static void rxrpc_congestion_timeout(struct rxrpc_call *call)
 177 {
 178         set_bit(RXRPC_CALL_RETRANS_TIMEOUT, &call->flags);
 179 }
 180
 181 /*
 182  * Perform retransmission of NAK'd and unack'd packets.
 183  */
 184 static void rxrpc_resend(struct rxrpc_call *call, ktime_t now)
 185 {
 186         struct rxrpc_skb_priv *sp;
 187         struct sk_buff *skb;
 188         rxrpc_seq_t cursor, seq, top;
 189         ktime_t max_age, oldest, ack_ts;
 190         int ix;
 191         u8 annotation, anno_type, retrans = 0, unacked = 0;
 192
 193         _enter("{%d,%d}", call->tx_hard_ack, call->tx_top);
 194
 195         max_age = ktime_sub_ms(now, rxrpc_resend_timeout);
 196
 197         spin_lock_bh(&call->lock);
 198
 199         cursor = call->tx_hard_ack;
 200         top = call->tx_top;
 201         ASSERT(before_eq(cursor, top));
 202         if (cursor == top)
 203                 goto out_unlock;
 204
 205         /* Scan the packet list without dropping the lock and decide which of
 206          * the packets in the Tx buffer we're going to resend and what the new
 207          * resend timeout will be.
 208          */
 209         oldest = now;
 210         for (seq = cursor + 1; before_eq(seq, top); seq++) {
 211                 ix = seq & RXRPC_RXTX_BUFF_MASK;
 212                 annotation = call->rxtx_annotations[ix];
 213                 anno_type = annotation & RXRPC_TX_ANNO_MASK;
 214                 annotation &= ~RXRPC_TX_ANNO_MASK;
 215                 if (anno_type == RXRPC_TX_ANNO_ACK)
 216                         continue;
 217
 218                 skb = call->rxtx_buffer[ix];
 219                 rxrpc_see_skb(skb, rxrpc_skb_tx_seen);
 220                 sp = rxrpc_skb(skb);
 221
 222                 if (anno_type == RXRPC_TX_ANNO_UNACK) {
 223                         if (ktime_after(skb->tstamp, max_age)) {
 224                                 if (ktime_before(skb->tstamp, oldest))
 225                                         oldest = skb->tstamp;
 226                                 continue;
 227                         }
 228                         if (!(annotation & RXRPC_TX_ANNO_RESENT))
 229                                 unacked++;
 230                 }
 231
 232                 /* Okay, we need to retransmit a packet. */
 233                 call->rxtx_annotations[ix] = RXRPC_TX_ANNO_RETRANS | annotation;
 234                 retrans++;
 235                 trace_rxrpc_retransmit(call, seq, annotation | anno_type,
 236                                        ktime_to_ns(ktime_sub(skb->tstamp, max_age)));
 237         }
 238
 239         call->resend_at = ktime_add_ms(oldest, rxrpc_resend_timeout);
 240
 241         if (unacked)
 242                 rxrpc_congestion_timeout(call);
 243
 244         /* If there was nothing that needed retransmission then it's likely
 245          * that an ACK got lost somewhere.  Send a ping to find out instead of
 246          * retransmitting data.
 247          */
 248         if (!retrans) {
 249                 rxrpc_set_timer(call, rxrpc_timer_set_for_resend, now);
 250                 spin_unlock_bh(&call->lock);
 251                 ack_ts = ktime_sub(now, call->acks_latest_ts);
 252                 if (ktime_to_ns(ack_ts) < call->peer->rtt)
 253                         goto out;
 254                 rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, 0, true, false,
 255                                   rxrpc_propose_ack_ping_for_lost_ack);
 256                 rxrpc_send_call_packet(call, RXRPC_PACKET_TYPE_ACK);
 257                 goto out;
 258         }
 259
 260         /* Now go through the Tx window and perform the retransmissions.  We
 261          * have to drop the lock for each send.  If an ACK comes in whilst the
 262          * lock is dropped, it may clear some of the retransmission markers for
 263          * packets that it soft-ACKs.
 264          */
 265         for (seq = cursor + 1; before_eq(seq, top); seq++) {
 266                 ix = seq & RXRPC_RXTX_BUFF_MASK;
 267                 annotation = call->rxtx_annotations[ix];
 268                 anno_type = annotation & RXRPC_TX_ANNO_MASK;
 269                 if (anno_type != RXRPC_TX_ANNO_RETRANS)
 270                         continue;
 271
 272                 skb = call->rxtx_buffer[ix];
 273                 rxrpc_get_skb(skb, rxrpc_skb_tx_got);
 274                 spin_unlock_bh(&call->lock);
 275
 276                 if (rxrpc_send_data_packet(call, skb, true) < 0) {
 277                         rxrpc_free_skb(skb, rxrpc_skb_tx_freed);
 278                         return;
 279                 }
 280
 281                 if (rxrpc_is_client_call(call))
 282                         rxrpc_expose_client_call(call);
 283
 284                 rxrpc_free_skb(skb, rxrpc_skb_tx_freed);
 285                 spin_lock_bh(&call->lock);
 286
 287                 /* We need to clear the retransmit state, but there are two
 288                  * things we need to be aware of: A new ACK/NAK might have been
 289                  * received and the packet might have been hard-ACK'd (in which
 290                  * case it will no longer be in the buffer).
 291                  */
 292                 if (after(seq, call->tx_hard_ack)) {
 293                         annotation = call->rxtx_annotations[ix];
 294                         anno_type = annotation & RXRPC_TX_ANNO_MASK;
 295                         if (anno_type == RXRPC_TX_ANNO_RETRANS ||
 296                             anno_type == RXRPC_TX_ANNO_NAK) {
 297                                 annotation &= ~RXRPC_TX_ANNO_MASK;
 298                                 annotation |= RXRPC_TX_ANNO_UNACK;
 299                         }
 300                         annotation |= RXRPC_TX_ANNO_RESENT;
 301                         call->rxtx_annotations[ix] = annotation;
 302                 }
 303
 304                 if (after(call->tx_hard_ack, seq))
 305                         seq = call->tx_hard_ack;
 306         }
 307
 308 out_unlock:
 309         spin_unlock_bh(&call->lock);
 310 out:
 311         _leave("");
 312 }
 313
 314 /*
 315  * Handle retransmission and deferred ACK/abort generation.
 316  */
 317 void rxrpc_process_call(struct work_struct *work)
 318 {
 319         struct rxrpc_call *call =
 320                 container_of(work, struct rxrpc_call, processor);
 321         ktime_t now;
 322
 323         rxrpc_see_call(call);
 324
 325         //printk("\n--------------------\n");
 326         _enter("{%d,%s,%lx}",
 327                call->debug_id, rxrpc_call_states[call->state], call->events);
 328
 329 recheck_state:
 330         if (test_and_clear_bit(RXRPC_CALL_EV_ABORT, &call->events)) {
 331                 rxrpc_send_call_packet(call, RXRPC_PACKET_TYPE_ABORT);
 332                 goto recheck_state;
 333         }
 334
 335         if (call->state == RXRPC_CALL_COMPLETE) {
 336                 del_timer_sync(&call->timer);
 337                 goto out_put;
 338         }
 339
 340         now = ktime_get_real();
 341         if (ktime_before(call->expire_at, now)) {
 342                 rxrpc_abort_call("EXP", call, 0, RX_CALL_TIMEOUT, ETIME);
 343                 set_bit(RXRPC_CALL_EV_ABORT, &call->events);
 344                 goto recheck_state;
 345         }
 346
 347         if (test_and_clear_bit(RXRPC_CALL_EV_ACK, &call->events)) {
 348                 call->ack_at = call->expire_at;
 349                 if (call->ackr_reason) {
 350                         rxrpc_send_call_packet(call, RXRPC_PACKET_TYPE_ACK);
 351                         goto recheck_state;
 352                 }
 353         }
 354
 355         if (test_and_clear_bit(RXRPC_CALL_EV_RESEND, &call->events)) {
 356                 rxrpc_resend(call, now);
 357                 goto recheck_state;
 358         }
 359
 360         rxrpc_set_timer(call, rxrpc_timer_set_for_resend, now);
 361
 362         /* other events may have been raised since we started checking */
 363         if (call->events && call->state < RXRPC_CALL_COMPLETE) {
 364                 __rxrpc_queue_call(call);
 365                 goto out;
 366         }
 367
 368 out_put:
 369         rxrpc_put_call(call, rxrpc_call_put);
 370 out:
 371         _leave("");
 372 }