// SPDX-License-Identifier: GPL-2.0-or-later
/* 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 ([email protected])
*/
#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.
*/
void rxrpc_propose_ping(struct rxrpc_call *call, u32 serial,
enum rxrpc_propose_ack_trace why)
{
ktime_t delay = ms_to_ktime(READ_ONCE(rxrpc_idle_ack_delay));
ktime_t now = ktime_get_real();
ktime_t ping_at = ktime_add(now, delay);
trace_rxrpc_propose_ack(call, why, RXRPC_ACK_PING, serial);
if (ktime_before(ping_at, call->ping_at)) {
call->ping_at = ping_at;
trace_rxrpc_timer_set(call, delay, rxrpc_timer_trace_ping);
}
}
/*
* Propose a DELAY ACK be sent in the future.
*/
void rxrpc_propose_delay_ACK(struct rxrpc_call *call, rxrpc_serial_t serial,
enum rxrpc_propose_ack_trace why)
{
ktime_t now = ktime_get_real(), delay;
trace_rxrpc_propose_ack(call, why, RXRPC_ACK_DELAY, serial);
if (call->peer->srtt_us)
delay = (call->peer->srtt_us >> 3) * NSEC_PER_USEC;
else
delay = ms_to_ktime(READ_ONCE(rxrpc_soft_ack_delay));
ktime_add_ms(delay, call->tx_backoff);
call->delay_ack_at = ktime_add(now, delay);
trace_rxrpc_timer_set(call, delay, rxrpc_timer_trace_delayed_ack);
}
/*
* 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.
*/
void rxrpc_resend(struct rxrpc_call *call, struct sk_buff *ack_skb)
{
struct rxrpc_ackpacket *ack = NULL;
struct rxrpc_skb_priv *sp;
struct rxrpc_txbuf *txb;
rxrpc_seq_t transmitted = call->tx_transmitted;
ktime_t next_resend = KTIME_MAX, rto = ns_to_ktime(call->peer->rto_us * NSEC_PER_USEC);
ktime_t resend_at = KTIME_MAX, now, delay;
bool unacked = false, did_send = false;
unsigned int i;
_enter("{%d,%d}", call->acks_hard_ack, call->tx_top);
now = ktime_get_real();
if (list_empty(&call->tx_buffer))
goto no_resend;
trace_rxrpc_resend(call, ack_skb);
txb = list_first_entry(&call->tx_buffer, struct rxrpc_txbuf, call_link);
/* Scan the soft ACK table without dropping the lock and resend any
* explicitly NAK'd packets.
*/
if (ack_skb) {
sp = rxrpc_skb(ack_skb);
ack = (void *)ack_skb->data + sizeof(struct rxrpc_wire_header);
for (i = 0; i < sp->ack.nr_acks; i++) {
rxrpc_seq_t seq;
if (ack->acks[i] & 1)
continue;
seq = sp->ack.first_ack + i;
if (after(txb->seq, transmitted))
break;
if (after(txb->seq, seq))
continue; /* A new hard ACK probably came in */
list_for_each_entry_from(txb, &call->tx_buffer, call_link) {
if (txb->seq == seq)
goto found_txb;
}
goto no_further_resend;
found_txb:
resend_at = ktime_add(txb->last_sent, rto);
if (after(txb->serial, call->acks_highest_serial)) {
if (ktime_after(resend_at, now) &&
ktime_before(resend_at, next_resend))
next_resend = resend_at;
continue; /* Ack point not yet reached */
}
rxrpc_see_txbuf(txb, rxrpc_txbuf_see_unacked);
trace_rxrpc_retransmit(call, txb->seq, txb->serial,
ktime_sub(resend_at, now));
txb->flags |= RXRPC_TXBUF_RESENT;
rxrpc_transmit_one(call, txb);
did_send = true;
now = ktime_get_real();
if (list_is_last(&txb->call_link, &call->tx_buffer))
goto no_further_resend;
txb = list_next_entry(txb, call_link);
}
}
/* Fast-forward through the Tx queue to the point the peer says it has
* seen. Anything between the soft-ACK table and that point will get
* ACK'd or NACK'd in due course, so don't worry about it here; here we
* need to consider retransmitting anything beyond that point.
*/
if (after_eq(call->acks_prev_seq, call->tx_transmitted))
goto no_further_resend;
list_for_each_entry_from(txb, &call->tx_buffer, call_link) {
resend_at = ktime_add(txb->last_sent, rto);
if (before_eq(txb->seq, call->acks_prev_seq))
continue;
if (after(txb->seq, call->tx_transmitted))
break; /* Not transmitted yet */
if (ack && ack->reason == RXRPC_ACK_PING_RESPONSE &&
before(txb->serial, ntohl(ack->serial)))
goto do_resend; /* Wasn't accounted for by a more recent ping. */
if (ktime_after(resend_at, now)) {
if (ktime_before(resend_at, next_resend))
next_resend = resend_at;
continue;
}
do_resend:
unacked = true;
txb->flags |= RXRPC_TXBUF_RESENT;
rxrpc_transmit_one(call, txb);
did_send = true;
rxrpc_inc_stat(call->rxnet, stat_tx_data_retrans);
now = ktime_get_real();
}
no_further_resend:
no_resend:
if (resend_at < KTIME_MAX) {
delay = rxrpc_get_rto_backoff(call->peer, did_send);
resend_at = ktime_add(resend_at, delay);
trace_rxrpc_timer_set(call, resend_at - now, rxrpc_timer_trace_resend_reset);
}
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 (!did_send) {
ktime_t next_ping = ktime_add_us(call->acks_latest_ts,
call->peer->srtt_us >> 3);
if (ktime_sub(next_ping, now) <= 0)
rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
rxrpc_propose_ack_ping_for_0_retrans);
}
_leave("");
}
/*
* Start transmitting the reply to a service. This cancels the need to ACK the
* request if we haven't yet done so.
*/
static void rxrpc_begin_service_reply(struct rxrpc_call *call)
{
rxrpc_set_call_state(call, RXRPC_CALL_SERVER_SEND_REPLY);
if (call->ackr_reason == RXRPC_ACK_DELAY)
call->ackr_reason = 0;
call->delay_ack_at = KTIME_MAX;
trace_rxrpc_timer_can(call, rxrpc_timer_trace_delayed_ack);
}
/*
* Close the transmission phase. After this point there is no more data to be
* transmitted in the call.
*/
static void rxrpc_close_tx_phase(struct rxrpc_call *call)
{
_debug("________awaiting reply/ACK__________");
switch (__rxrpc_call_state(call)) {
case RXRPC_CALL_CLIENT_SEND_REQUEST:
rxrpc_set_call_state(call, RXRPC_CALL_CLIENT_AWAIT_REPLY);
break;
case RXRPC_CALL_SERVER_SEND_REPLY:
rxrpc_set_call_state(call, RXRPC_CALL_SERVER_AWAIT_ACK);
break;
default:
break;
}
}
static bool rxrpc_tx_window_has_space(struct rxrpc_call *call)
{
unsigned int winsize = min_t(unsigned int, call->tx_winsize,
call->cong_cwnd + call->cong_extra);
rxrpc_seq_t window = call->acks_hard_ack, wtop = window + winsize;
rxrpc_seq_t tx_top = call->tx_top;
int space;
space = wtop - tx_top;
return space > 0;
}
/*
* Decant some if the sendmsg prepared queue into the transmission buffer.
*/
static void rxrpc_decant_prepared_tx(struct rxrpc_call *call)
{
struct rxrpc_txbuf *txb;
if (!test_bit(RXRPC_CALL_EXPOSED, &call->flags)) {
if (list_empty(&call->tx_sendmsg))
return;
rxrpc_expose_client_call(call);
}
while ((txb = list_first_entry_or_null(&call->tx_sendmsg,
struct rxrpc_txbuf, call_link))) {
spin_lock(&call->tx_lock);
list_del(&txb->call_link);
spin_unlock(&call->tx_lock);
call->tx_top = txb->seq;
list_add_tail(&txb->call_link, &call->tx_buffer);
if (txb->flags & RXRPC_LAST_PACKET)
rxrpc_close_tx_phase(call);
rxrpc_transmit_one(call, txb);
if (!rxrpc_tx_window_has_space(call))
break;
}
}
static void rxrpc_transmit_some_data(struct rxrpc_call *call)
{
switch (__rxrpc_call_state(call)) {
case RXRPC_CALL_SERVER_ACK_REQUEST:
if (list_empty(&call->tx_sendmsg))
return;
rxrpc_begin_service_reply(call);
fallthrough;
case RXRPC_CALL_SERVER_SEND_REPLY:
case RXRPC_CALL_CLIENT_SEND_REQUEST:
if (!rxrpc_tx_window_has_space(call))
return;
if (list_empty(&call->tx_sendmsg)) {
rxrpc_inc_stat(call->rxnet, stat_tx_data_underflow);
return;
}
rxrpc_decant_prepared_tx(call);
break;
default:
return;
}
}
/*
* Ping the other end to fill our RTT cache and to retrieve the rwind
* and MTU parameters.
*/
static void rxrpc_send_initial_ping(struct rxrpc_call *call)
{
if (call->peer->rtt_count < 3 ||
ktime_before(ktime_add_ms(call->peer->rtt_last_req, 1000),
ktime_get_real()))
rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
rxrpc_propose_ack_ping_for_params);
}
/*
* Handle retransmission and deferred ACK/abort generation.
*/
bool rxrpc_input_call_event(struct rxrpc_call *call, struct sk_buff *skb)
{
ktime_t now, t;
bool resend = false;
s32 abort_code;
rxrpc_see_call(call, rxrpc_call_see_input);
//printk("\n--------------------\n");
_enter("{%d,%s,%lx}",
call->debug_id, rxrpc_call_states[__rxrpc_call_state(call)],
call->events);
if (__rxrpc_call_is_complete(call))
goto out;
/* Handle abort request locklessly, vs rxrpc_propose_abort(). */
abort_code = smp_load_acquire(&call->send_abort);
if (abort_code) {
rxrpc_abort_call(call, 0, call->send_abort, call->send_abort_err,
call->send_abort_why);
goto out;
}
if (skb && skb->mark == RXRPC_SKB_MARK_ERROR)
goto out;
if (skb)
rxrpc_input_call_packet(call, skb);
/* If we see our async-event poke, check for timeout trippage. */
now = ktime_get_real();
t = ktime_sub(call->expect_rx_by, now);
if (t <= 0) {
trace_rxrpc_timer_exp(call, t, rxrpc_timer_trace_expect_rx);
goto expired;
}
t = ktime_sub(call->expect_req_by, now);
if (t <= 0) {
call->expect_req_by = KTIME_MAX;
if (__rxrpc_call_state(call) == RXRPC_CALL_SERVER_RECV_REQUEST) {
trace_rxrpc_timer_exp(call, t, rxrpc_timer_trace_idle);
goto expired;
}
}
t = ktime_sub(READ_ONCE(call->expect_term_by), now);
if (t <= 0) {
trace_rxrpc_timer_exp(call, t, rxrpc_timer_trace_hard);
goto expired;
}
t = ktime_sub(call->delay_ack_at, now);
if (t <= 0) {
trace_rxrpc_timer_exp(call, t, rxrpc_timer_trace_delayed_ack);
call->delay_ack_at = KTIME_MAX;
rxrpc_send_ACK(call, RXRPC_ACK_DELAY, 0,
rxrpc_propose_ack_delayed_ack);
}
t = ktime_sub(call->ack_lost_at, now);
if (t <= 0) {
trace_rxrpc_timer_exp(call, t, rxrpc_timer_trace_lost_ack);
call->ack_lost_at = KTIME_MAX;
set_bit(RXRPC_CALL_EV_ACK_LOST, &call->events);
}
t = ktime_sub(call->ping_at, now);
if (t <= 0) {
trace_rxrpc_timer_exp(call, t, rxrpc_timer_trace_ping);
call->ping_at = KTIME_MAX;
rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
rxrpc_propose_ack_ping_for_keepalive);
}
t = ktime_sub(call->resend_at, now);
if (t <= 0) {
trace_rxrpc_timer_exp(call, t, rxrpc_timer_trace_resend);
call->resend_at = KTIME_MAX;
resend = true;
}
rxrpc_transmit_some_data(call);
now = ktime_get_real();
t = ktime_sub(call->keepalive_at, now);
if (t <= 0) {
trace_rxrpc_timer_exp(call, t, rxrpc_timer_trace_keepalive);
call->keepalive_at = KTIME_MAX;
rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
rxrpc_propose_ack_ping_for_keepalive);
}
if (skb) {
struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
if (sp->hdr.type == RXRPC_PACKET_TYPE_ACK)
rxrpc_congestion_degrade(call);
}
if (test_and_clear_bit(RXRPC_CALL_EV_INITIAL_PING, &call->events))
rxrpc_send_initial_ping(call);
/* Process events */
if (test_and_clear_bit(RXRPC_CALL_EV_ACK_LOST, &call->events))
rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
rxrpc_propose_ack_ping_for_lost_ack);
if (resend &&
__rxrpc_call_state(call) != RXRPC_CALL_CLIENT_RECV_REPLY &&
!test_bit(RXRPC_CALL_TX_ALL_ACKED, &call->flags))
rxrpc_resend(call, NULL);
if (test_and_clear_bit(RXRPC_CALL_RX_IS_IDLE, &call->flags))
rxrpc_send_ACK(call, RXRPC_ACK_IDLE, 0,
rxrpc_propose_ack_rx_idle);
if (call->ackr_nr_unacked > 2) {
if (call->peer->rtt_count < 3)
rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
rxrpc_propose_ack_ping_for_rtt);
else if (ktime_before(ktime_add_ms(call->peer->rtt_last_req, 1000),
ktime_get_real()))
rxrpc_send_ACK(call, RXRPC_ACK_PING, 0,
rxrpc_propose_ack_ping_for_old_rtt);
else
rxrpc_send_ACK(call, RXRPC_ACK_IDLE, 0,
rxrpc_propose_ack_input_data);
}
/* Make sure the timer is restarted */
if (!__rxrpc_call_is_complete(call)) {
ktime_t next = READ_ONCE(call->expect_term_by), delay;
#define set(T) { ktime_t _t = (T); if (ktime_before(_t, next)) next = _t; }
set(call->expect_req_by);
set(call->expect_rx_by);
set(call->delay_ack_at);
set(call->ack_lost_at);
set(call->resend_at);
set(call->keepalive_at);
set(call->ping_at);
now = ktime_get_real();
delay = ktime_sub(next, now);
if (delay <= 0) {
rxrpc_poke_call(call, rxrpc_call_poke_timer_now);
} else {
unsigned long nowj = jiffies, delayj, nextj;
delayj = max(nsecs_to_jiffies(delay), 1);
nextj = nowj + delayj;
if (time_before(nextj, call->timer.expires) ||
!timer_pending(&call->timer)) {
trace_rxrpc_timer_restart(call, delay, delayj);
timer_reduce(&call->timer, nextj);
}
}
}
out:
if (__rxrpc_call_is_complete(call)) {
del_timer_sync(&call->timer);
if (!test_bit(RXRPC_CALL_DISCONNECTED, &call->flags))
rxrpc_disconnect_call(call);
if (call->security)
call->security->free_call_crypto(call);
}
if (call->acks_hard_ack != call->tx_bottom)
rxrpc_shrink_call_tx_buffer(call);
_leave("");
return true;
expired:
if (test_bit(RXRPC_CALL_RX_HEARD, &call->flags) &&
(int)call->conn->hi_serial - (int)call->rx_serial > 0) {
trace_rxrpc_call_reset(call);
rxrpc_abort_call(call, 0, RX_CALL_DEAD, -ECONNRESET,
rxrpc_abort_call_reset);
} else {
rxrpc_abort_call(call, 0, RX_CALL_TIMEOUT, -ETIME,
rxrpc_abort_call_timeout);
}
goto out;
}
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