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 * Propose a PING ACK be sent. 26 */ 27 static void rxrpc_propose_ping(struct rxrpc_call *call, 28 bool immediate, bool background) 29 { 30 if (immediate) { 31 if (background && 32 !test_and_set_bit(RXRPC_CALL_EV_PING, &call->events)) 33 rxrpc_queue_call(call); 34 } else { 35 unsigned long now = jiffies; 36 unsigned long ping_at = now + rxrpc_idle_ack_delay; 37 38 if (time_before(ping_at, call->ping_at)) { 39 WRITE_ONCE(call->ping_at, ping_at); 40 rxrpc_reduce_call_timer(call, ping_at, now, 41 rxrpc_timer_set_for_ping); 42 } 43 } 44 } 45 46 /* 47 * propose an ACK be sent 48 */ 49 static void __rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason, 50 u16 skew, u32 serial, bool immediate, 51 bool background, 52 enum rxrpc_propose_ack_trace why) 53 { 54 enum rxrpc_propose_ack_outcome outcome = rxrpc_propose_ack_use; 55 unsigned long expiry = rxrpc_soft_ack_delay; 56 s8 prior = rxrpc_ack_priority[ack_reason]; 57 58 /* Pings are handled specially because we don't want to accidentally 59 * lose a ping response by subsuming it into a ping. 60 */ 61 if (ack_reason == RXRPC_ACK_PING) { 62 rxrpc_propose_ping(call, immediate, background); 63 goto trace; 64 } 65 66 /* Update DELAY, IDLE, REQUESTED and PING_RESPONSE ACK serial 67 * numbers, but we don't alter the timeout. 68 */ 69 _debug("prior %u %u vs %u %u", 70 ack_reason, prior, 71 call->ackr_reason, rxrpc_ack_priority[call->ackr_reason]); 72 if (ack_reason == call->ackr_reason) { 73 if (RXRPC_ACK_UPDATEABLE & (1 << ack_reason)) { 74 outcome = rxrpc_propose_ack_update; 75 call->ackr_serial = serial; 76 call->ackr_skew = skew; 77 } 78 if (!immediate) 79 goto trace; 80 } else if (prior > rxrpc_ack_priority[call->ackr_reason]) { 81 call->ackr_reason = ack_reason; 82 call->ackr_serial = serial; 83 call->ackr_skew = skew; 84 } else { 85 outcome = rxrpc_propose_ack_subsume; 86 } 87 88 switch (ack_reason) { 89 case RXRPC_ACK_REQUESTED: 90 if (rxrpc_requested_ack_delay < expiry) 91 expiry = rxrpc_requested_ack_delay; 92 if (serial == 1) 93 immediate = false; 94 break; 95 96 case RXRPC_ACK_DELAY: 97 if (rxrpc_soft_ack_delay < expiry) 98 expiry = rxrpc_soft_ack_delay; 99 break; 100 101 case RXRPC_ACK_IDLE: 102 if (rxrpc_idle_ack_delay < expiry) 103 expiry = rxrpc_idle_ack_delay; 104 break; 105 106 default: 107 immediate = true; 108 break; 109 } 110 111 if (test_bit(RXRPC_CALL_EV_ACK, &call->events)) { 112 _debug("already scheduled"); 113 } else if (immediate || expiry == 0) { 114 _debug("immediate ACK %lx", call->events); 115 if (!test_and_set_bit(RXRPC_CALL_EV_ACK, &call->events) && 116 background) 117 rxrpc_queue_call(call); 118 } else { 119 unsigned long now = jiffies, ack_at; 120 121 if (call->peer->rtt_usage > 0) 122 ack_at = nsecs_to_jiffies(call->peer->rtt); 123 else 124 ack_at = expiry; 125 126 ack_at += now; 127 if (time_before(ack_at, call->ack_at)) { 128 WRITE_ONCE(call->ack_at, ack_at); 129 rxrpc_reduce_call_timer(call, ack_at, now, 130 rxrpc_timer_set_for_ack); 131 } 132 } 133 134 trace: 135 trace_rxrpc_propose_ack(call, why, ack_reason, serial, immediate, 136 background, outcome); 137 } 138 139 /* 140 * propose an ACK be sent, locking the call structure 141 */ 142 void rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason, 143 u16 skew, u32 serial, bool immediate, bool background, 144 enum rxrpc_propose_ack_trace why) 145 { 146 spin_lock_bh(&call->lock); 147 __rxrpc_propose_ACK(call, ack_reason, skew, serial, 148 immediate, background, why); 149 spin_unlock_bh(&call->lock); 150 } 151 152 /* 153 * Handle congestion being detected by the retransmit timeout. 154 */ 155 static void rxrpc_congestion_timeout(struct rxrpc_call *call) 156 { 157 set_bit(RXRPC_CALL_RETRANS_TIMEOUT, &call->flags); 158 } 159 160 /* 161 * Perform retransmission of NAK'd and unack'd packets. 162 */ 163 static void rxrpc_resend(struct rxrpc_call *call, unsigned long now_j) 164 { 165 struct rxrpc_skb_priv *sp; 166 struct sk_buff *skb; 167 unsigned long resend_at; 168 rxrpc_seq_t cursor, seq, top; 169 ktime_t now, max_age, oldest, ack_ts, timeout, min_timeo; 170 int ix; 171 u8 annotation, anno_type, retrans = 0, unacked = 0; 172 173 _enter("{%d,%d}", call->tx_hard_ack, call->tx_top); 174 175 if (call->peer->rtt_usage > 1) 176 timeout = ns_to_ktime(call->peer->rtt * 3 / 2); 177 else 178 timeout = ms_to_ktime(rxrpc_resend_timeout); 179 min_timeo = ns_to_ktime((1000000000 / HZ) * 4); 180 if (ktime_before(timeout, min_timeo)) 181 timeout = min_timeo; 182 183 now = ktime_get_real(); 184 max_age = ktime_sub(now, timeout); 185 186 spin_lock_bh(&call->lock); 187 188 cursor = call->tx_hard_ack; 189 top = call->tx_top; 190 ASSERT(before_eq(cursor, top)); 191 if (cursor == top) 192 goto out_unlock; 193 194 /* Scan the packet list without dropping the lock and decide which of 195 * the packets in the Tx buffer we're going to resend and what the new 196 * resend timeout will be. 197 */ 198 oldest = now; 199 for (seq = cursor + 1; before_eq(seq, top); seq++) { 200 ix = seq & RXRPC_RXTX_BUFF_MASK; 201 annotation = call->rxtx_annotations[ix]; 202 anno_type = annotation & RXRPC_TX_ANNO_MASK; 203 annotation &= ~RXRPC_TX_ANNO_MASK; 204 if (anno_type == RXRPC_TX_ANNO_ACK) 205 continue; 206 207 skb = call->rxtx_buffer[ix]; 208 rxrpc_see_skb(skb, rxrpc_skb_tx_seen); 209 sp = rxrpc_skb(skb); 210 211 if (anno_type == RXRPC_TX_ANNO_UNACK) { 212 if (ktime_after(skb->tstamp, max_age)) { 213 if (ktime_before(skb->tstamp, oldest)) 214 oldest = skb->tstamp; 215 continue; 216 } 217 if (!(annotation & RXRPC_TX_ANNO_RESENT)) 218 unacked++; 219 } 220 221 /* Okay, we need to retransmit a packet. */ 222 call->rxtx_annotations[ix] = RXRPC_TX_ANNO_RETRANS | annotation; 223 retrans++; 224 trace_rxrpc_retransmit(call, seq, annotation | anno_type, 225 ktime_to_ns(ktime_sub(skb->tstamp, max_age))); 226 } 227 228 resend_at = nsecs_to_jiffies(ktime_to_ns(ktime_sub(oldest, now))); 229 resend_at += jiffies + rxrpc_resend_timeout; 230 WRITE_ONCE(call->resend_at, resend_at); 231 232 if (unacked) 233 rxrpc_congestion_timeout(call); 234 235 /* If there was nothing that needed retransmission then it's likely 236 * that an ACK got lost somewhere. Send a ping to find out instead of 237 * retransmitting data. 238 */ 239 if (!retrans) { 240 rxrpc_reduce_call_timer(call, resend_at, now, 241 rxrpc_timer_set_for_resend); 242 spin_unlock_bh(&call->lock); 243 ack_ts = ktime_sub(now, call->acks_latest_ts); 244 if (ktime_to_ns(ack_ts) < call->peer->rtt) 245 goto out; 246 rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, 0, true, false, 247 rxrpc_propose_ack_ping_for_lost_ack); 248 rxrpc_send_ack_packet(call, true, NULL); 249 goto out; 250 } 251 252 /* Now go through the Tx window and perform the retransmissions. We 253 * have to drop the lock for each send. If an ACK comes in whilst the 254 * lock is dropped, it may clear some of the retransmission markers for 255 * packets that it soft-ACKs. 256 */ 257 for (seq = cursor + 1; before_eq(seq, top); seq++) { 258 ix = seq & RXRPC_RXTX_BUFF_MASK; 259 annotation = call->rxtx_annotations[ix]; 260 anno_type = annotation & RXRPC_TX_ANNO_MASK; 261 if (anno_type != RXRPC_TX_ANNO_RETRANS) 262 continue; 263 264 skb = call->rxtx_buffer[ix]; 265 rxrpc_get_skb(skb, rxrpc_skb_tx_got); 266 spin_unlock_bh(&call->lock); 267 268 if (rxrpc_send_data_packet(call, skb, true) < 0) { 269 rxrpc_free_skb(skb, rxrpc_skb_tx_freed); 270 return; 271 } 272 273 if (rxrpc_is_client_call(call)) 274 rxrpc_expose_client_call(call); 275 276 rxrpc_free_skb(skb, rxrpc_skb_tx_freed); 277 spin_lock_bh(&call->lock); 278 279 /* We need to clear the retransmit state, but there are two 280 * things we need to be aware of: A new ACK/NAK might have been 281 * received and the packet might have been hard-ACK'd (in which 282 * case it will no longer be in the buffer). 283 */ 284 if (after(seq, call->tx_hard_ack)) { 285 annotation = call->rxtx_annotations[ix]; 286 anno_type = annotation & RXRPC_TX_ANNO_MASK; 287 if (anno_type == RXRPC_TX_ANNO_RETRANS || 288 anno_type == RXRPC_TX_ANNO_NAK) { 289 annotation &= ~RXRPC_TX_ANNO_MASK; 290 annotation |= RXRPC_TX_ANNO_UNACK; 291 } 292 annotation |= RXRPC_TX_ANNO_RESENT; 293 call->rxtx_annotations[ix] = annotation; 294 } 295 296 if (after(call->tx_hard_ack, seq)) 297 seq = call->tx_hard_ack; 298 } 299 300 out_unlock: 301 spin_unlock_bh(&call->lock); 302 out: 303 _leave(""); 304 } 305 306 /* 307 * Handle retransmission and deferred ACK/abort generation. 308 */ 309 void rxrpc_process_call(struct work_struct *work) 310 { 311 struct rxrpc_call *call = 312 container_of(work, struct rxrpc_call, processor); 313 rxrpc_serial_t *send_ack; 314 unsigned long now, next, t; 315 316 rxrpc_see_call(call); 317 318 //printk("\n--------------------\n"); 319 _enter("{%d,%s,%lx}", 320 call->debug_id, rxrpc_call_states[call->state], call->events); 321 322 recheck_state: 323 if (test_and_clear_bit(RXRPC_CALL_EV_ABORT, &call->events)) { 324 rxrpc_send_abort_packet(call); 325 goto recheck_state; 326 } 327 328 if (call->state == RXRPC_CALL_COMPLETE) { 329 del_timer_sync(&call->timer); 330 rxrpc_notify_socket(call); 331 goto out_put; 332 } 333 334 /* Work out if any timeouts tripped */ 335 now = jiffies; 336 t = READ_ONCE(call->expect_rx_by); 337 if (time_after_eq(now, t)) { 338 trace_rxrpc_timer(call, rxrpc_timer_exp_normal, now); 339 set_bit(RXRPC_CALL_EV_EXPIRED, &call->events); 340 } 341 342 t = READ_ONCE(call->expect_req_by); 343 if (call->state == RXRPC_CALL_SERVER_RECV_REQUEST && 344 time_after_eq(now, t)) { 345 trace_rxrpc_timer(call, rxrpc_timer_exp_idle, now); 346 set_bit(RXRPC_CALL_EV_EXPIRED, &call->events); 347 } 348 349 t = READ_ONCE(call->expect_term_by); 350 if (time_after_eq(now, t)) { 351 trace_rxrpc_timer(call, rxrpc_timer_exp_hard, now); 352 set_bit(RXRPC_CALL_EV_EXPIRED, &call->events); 353 } 354 355 t = READ_ONCE(call->ack_at); 356 if (time_after_eq(now, t)) { 357 trace_rxrpc_timer(call, rxrpc_timer_exp_ack, now); 358 cmpxchg(&call->ack_at, t, now + MAX_JIFFY_OFFSET); 359 set_bit(RXRPC_CALL_EV_ACK, &call->events); 360 } 361 362 t = READ_ONCE(call->ack_lost_at); 363 if (time_after_eq(now, t)) { 364 trace_rxrpc_timer(call, rxrpc_timer_exp_lost_ack, now); 365 cmpxchg(&call->ack_lost_at, t, now + MAX_JIFFY_OFFSET); 366 set_bit(RXRPC_CALL_EV_ACK_LOST, &call->events); 367 } 368 369 t = READ_ONCE(call->keepalive_at); 370 if (time_after_eq(now, t)) { 371 trace_rxrpc_timer(call, rxrpc_timer_exp_keepalive, now); 372 cmpxchg(&call->keepalive_at, t, now + MAX_JIFFY_OFFSET); 373 rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, 0, true, true, 374 rxrpc_propose_ack_ping_for_keepalive); 375 set_bit(RXRPC_CALL_EV_PING, &call->events); 376 } 377 378 t = READ_ONCE(call->ping_at); 379 if (time_after_eq(now, t)) { 380 trace_rxrpc_timer(call, rxrpc_timer_exp_ping, now); 381 cmpxchg(&call->ping_at, t, now + MAX_JIFFY_OFFSET); 382 set_bit(RXRPC_CALL_EV_PING, &call->events); 383 } 384 385 t = READ_ONCE(call->resend_at); 386 if (time_after_eq(now, t)) { 387 trace_rxrpc_timer(call, rxrpc_timer_exp_resend, now); 388 cmpxchg(&call->resend_at, t, now + MAX_JIFFY_OFFSET); 389 set_bit(RXRPC_CALL_EV_RESEND, &call->events); 390 } 391 392 /* Process events */ 393 if (test_and_clear_bit(RXRPC_CALL_EV_EXPIRED, &call->events)) { 394 rxrpc_abort_call("EXP", call, 0, RX_USER_ABORT, -ETIME); 395 set_bit(RXRPC_CALL_EV_ABORT, &call->events); 396 goto recheck_state; 397 } 398 399 send_ack = NULL; 400 if (test_and_clear_bit(RXRPC_CALL_EV_ACK_LOST, &call->events)) { 401 call->acks_lost_top = call->tx_top; 402 rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, 0, true, false, 403 rxrpc_propose_ack_ping_for_lost_ack); 404 send_ack = &call->acks_lost_ping; 405 } 406 407 if (test_and_clear_bit(RXRPC_CALL_EV_ACK, &call->events) || 408 send_ack) { 409 if (call->ackr_reason) { 410 rxrpc_send_ack_packet(call, false, send_ack); 411 goto recheck_state; 412 } 413 } 414 415 if (test_and_clear_bit(RXRPC_CALL_EV_PING, &call->events)) { 416 rxrpc_send_ack_packet(call, true, NULL); 417 goto recheck_state; 418 } 419 420 if (test_and_clear_bit(RXRPC_CALL_EV_RESEND, &call->events)) { 421 rxrpc_resend(call, now); 422 goto recheck_state; 423 } 424 425 /* Make sure the timer is restarted */ 426 next = call->expect_rx_by; 427 428 #define set(T) { t = READ_ONCE(T); if (time_before(t, next)) next = t; } 429 430 set(call->expect_req_by); 431 set(call->expect_term_by); 432 set(call->ack_at); 433 set(call->ack_lost_at); 434 set(call->resend_at); 435 set(call->keepalive_at); 436 set(call->ping_at); 437 438 now = jiffies; 439 if (time_after_eq(now, next)) 440 goto recheck_state; 441 442 rxrpc_reduce_call_timer(call, next, now, rxrpc_timer_restart); 443 444 /* other events may have been raised since we started checking */ 445 if (call->events && call->state < RXRPC_CALL_COMPLETE) { 446 __rxrpc_queue_call(call); 447 goto out; 448 } 449 450 out_put: 451 rxrpc_put_call(call, rxrpc_call_put); 452 out: 453 _leave(""); 454 } 455