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|
/* Management of Tx window, Tx resend, ACKs and out-of-sequence reception
*
* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/circ_buf.h>
#include <linux/net.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/udp.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#include "ar-internal.h"
/*
* Propose a PING ACK be sent.
*/
static void rxrpc_propose_ping(struct rxrpc_call *call,
bool immediate, bool background)
{
if (immediate) {
if (background &&
!test_and_set_bit(RXRPC_CALL_EV_PING, &call->events))
rxrpc_queue_call(call);
} else {
unsigned long now = jiffies;
unsigned long ping_at = now + rxrpc_idle_ack_delay;
if (time_before(ping_at, call->ping_at)) {
WRITE_ONCE(call->ping_at, ping_at);
rxrpc_reduce_call_timer(call, ping_at, now,
rxrpc_timer_set_for_ping);
}
}
}
/*
* propose an ACK be sent
*/
static void __rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason,
u16 skew, u32 serial, bool immediate,
bool background,
enum rxrpc_propose_ack_trace why)
{
enum rxrpc_propose_ack_outcome outcome = rxrpc_propose_ack_use;
unsigned long expiry = rxrpc_soft_ack_delay;
s8 prior = rxrpc_ack_priority[ack_reason];
/* Pings are handled specially because we don't want to accidentally
* lose a ping response by subsuming it into a ping.
*/
if (ack_reason == RXRPC_ACK_PING) {
rxrpc_propose_ping(call, immediate, background);
goto trace;
}
/* Update DELAY, IDLE, REQUESTED and PING_RESPONSE ACK serial
* numbers, but we don't alter the timeout.
*/
_debug("prior %u %u vs %u %u",
ack_reason, prior,
call->ackr_reason, rxrpc_ack_priority[call->ackr_reason]);
if (ack_reason == call->ackr_reason) {
if (RXRPC_ACK_UPDATEABLE & (1 << ack_reason)) {
outcome = rxrpc_propose_ack_update;
call->ackr_serial = serial;
call->ackr_skew = skew;
}
if (!immediate)
goto trace;
} else if (prior > rxrpc_ack_priority[call->ackr_reason]) {
call->ackr_reason = ack_reason;
call->ackr_serial = serial;
call->ackr_skew = skew;
} else {
outcome = rxrpc_propose_ack_subsume;
}
switch (ack_reason) {
case RXRPC_ACK_REQUESTED:
if (rxrpc_requested_ack_delay < expiry)
expiry = rxrpc_requested_ack_delay;
if (serial == 1)
immediate = false;
break;
case RXRPC_ACK_DELAY:
if (rxrpc_soft_ack_delay < expiry)
expiry = rxrpc_soft_ack_delay;
break;
case RXRPC_ACK_IDLE:
if (rxrpc_idle_ack_delay < expiry)
expiry = rxrpc_idle_ack_delay;
break;
default:
immediate = true;
break;
}
if (test_bit(RXRPC_CALL_EV_ACK, &call->events)) {
_debug("already scheduled");
} else if (immediate || expiry == 0) {
_debug("immediate ACK %lx", call->events);
if (!test_and_set_bit(RXRPC_CALL_EV_ACK, &call->events) &&
background)
rxrpc_queue_call(call);
} else {
unsigned long now = jiffies, ack_at;
if (call->peer->rtt_usage > 0)
ack_at = nsecs_to_jiffies(call->peer->rtt);
else
ack_at = expiry;
ack_at += now;
if (time_before(ack_at, call->ack_at)) {
WRITE_ONCE(call->ack_at, ack_at);
rxrpc_reduce_call_timer(call, ack_at, now,
rxrpc_timer_set_for_ack);
}
}
trace:
trace_rxrpc_propose_ack(call, why, ack_reason, serial, immediate,
background, outcome);
}
/*
* propose an ACK be sent, locking the call structure
*/
void rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason,
u16 skew, u32 serial, bool immediate, bool background,
enum rxrpc_propose_ack_trace why)
{
spin_lock_bh(&call->lock);
__rxrpc_propose_ACK(call, ack_reason, skew, serial,
immediate, background, why);
spin_unlock_bh(&call->lock);
}
/*
* Handle congestion being detected by the retransmit timeout.
*/
static void rxrpc_congestion_timeout(struct rxrpc_call *call)
{
set_bit(RXRPC_CALL_RETRANS_TIMEOUT, &call->flags);
}
/*
* Perform retransmission of NAK'd and unack'd packets.
*/
static void rxrpc_resend(struct rxrpc_call *call, unsigned long now_j)
{
struct sk_buff *skb;
unsigned long resend_at;
rxrpc_seq_t cursor, seq, top;
ktime_t now, max_age, oldest, ack_ts, timeout, min_timeo;
int ix;
u8 annotation, anno_type, retrans = 0, unacked = 0;
_enter("{%d,%d}", call->tx_hard_ack, call->tx_top);
if (call->peer->rtt_usage > 1)
timeout = ns_to_ktime(call->peer->rtt * 3 / 2);
else
timeout = ms_to_ktime(rxrpc_resend_timeout);
min_timeo = ns_to_ktime((1000000000 / HZ) * 4);
if (ktime_before(timeout, min_timeo))
timeout = min_timeo;
now = ktime_get_real();
max_age = ktime_sub(now, timeout);
spin_lock_bh(&call->lock);
cursor = call->tx_hard_ack;
top = call->tx_top;
ASSERT(before_eq(cursor, top));
if (cursor == top)
goto out_unlock;
/* Scan the packet list without dropping the lock and decide which of
* the packets in the Tx buffer we're going to resend and what the new
* resend timeout will be.
*/
trace_rxrpc_resend(call, (cursor + 1) & RXRPC_RXTX_BUFF_MASK);
oldest = now;
for (seq = cursor + 1; before_eq(seq, top); seq++) {
ix = seq & RXRPC_RXTX_BUFF_MASK;
annotation = call->rxtx_annotations[ix];
anno_type = annotation & RXRPC_TX_ANNO_MASK;
annotation &= ~RXRPC_TX_ANNO_MASK;
if (anno_type == RXRPC_TX_ANNO_ACK)
continue;
skb = call->rxtx_buffer[ix];
rxrpc_see_skb(skb, rxrpc_skb_tx_seen);
if (anno_type == RXRPC_TX_ANNO_UNACK) {
if (ktime_after(skb->tstamp, max_age)) {
if (ktime_before(skb->tstamp, oldest))
oldest = skb->tstamp;
continue;
}
if (!(annotation & RXRPC_TX_ANNO_RESENT))
unacked++;
}
/* Okay, we need to retransmit a packet. */
call->rxtx_annotations[ix] = RXRPC_TX_ANNO_RETRANS | annotation;
retrans++;
trace_rxrpc_retransmit(call, seq, annotation | anno_type,
ktime_to_ns(ktime_sub(skb->tstamp, max_age)));
}
resend_at = nsecs_to_jiffies(ktime_to_ns(ktime_sub(now, oldest)));
resend_at += jiffies + rxrpc_resend_timeout;
WRITE_ONCE(call->resend_at, resend_at);
if (unacked)
rxrpc_congestion_timeout(call);
/* If there was nothing that needed retransmission then it's likely
* that an ACK got lost somewhere. Send a ping to find out instead of
* retransmitting data.
*/
if (!retrans) {
rxrpc_reduce_call_timer(call, resend_at, now_j,
rxrpc_timer_set_for_resend);
spin_unlock_bh(&call->lock);
ack_ts
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