path: root/net/rxrpc/call_event.c

// 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 (dhowells@redhat.com)
 */

#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);
}

struct rxrpc_resend_state {
	ktime_t			now;
	ktime_t			rto;
	struct rxrpc_txqueue	*tq;
	rxrpc_seq_t		seq;
	int			n;
	bool			did_send;
};

/*
 * Retransmit one or more packets.
 */
static bool rxrpc_retransmit_data(struct rxrpc_call *call,
				  struct rxrpc_resend_state *state,
				  bool skip_too_young)
{
	struct rxrpc_txqueue *tq = state->tq;
	unsigned int ix = state->seq & RXRPC_TXQ_MASK;
	struct rxrpc_txbuf *txb = tq->bufs[ix];
	ktime_t xmit_ts, resend_at;

	_enter("%x,%x,%x,%px", tq->qbase, state->seq, ix, txb);

	xmit_ts = ktime_add_us(tq->xmit_ts_base, tq->segment_xmit_ts[ix]);
	resend_at = ktime_add(xmit_ts, state->rto);

	trace_rxrpc_retransmit(call, tq, state->seq, txb->serial,
			       ktime_sub(resend_at, state->now));
	if (skip_too_young && ktime_after(resend_at, state->now))
		return false;

	__set_bit(ix, &tq->segment_retransmitted);
	txb->flags |= RXRPC_TXBUF_RESENT;
	rxrpc_transmit_data(call, tq, state->seq, state->n);
	rxrpc_inc_stat(call->rxnet, stat_tx_data_retrans);

	state->tq	= NULL;
	state->n	= 0;
	state->did_send	= true;
	state->now	= ktime_get_real();
	return true;
}

/*
 * Perform retransmission of NAK'd and unack'd packets.
 */
void rxrpc_resend(struct rxrpc_call *call, rxrpc_serial_t ack_serial, bool ping_response)
{
	struct rxrpc_resend_state state = {
		.rto	= rxrpc_get_rto_backoff(call->peer, false),
		.now	= ktime_get_real(),
	};
	struct rxrpc_txqueue *tq = call->tx_queue;
	ktime_t lowest_xmit_ts = KTIME_MAX;
	bool unacked = false;

	_enter("{%d,%d}", call->acks_hard_ack, call->tx_top);


	if (call->tx_bottom == call->tx_top) {
		call->resend_at = KTIME_MAX;
		trace_rxrpc_timer_can(call, rxrpc_timer_trace_resend);
		return;
	}

	trace_rxrpc_resend(call, ack_serial);

	/* Scan the transmission queue, looking for explicitly NAK'd packets. */
	do {
		unsigned long naks = ~tq->segment_acked;
		rxrpc_seq_t tq_top = tq->qbase + RXRPC_NR_TXQUEUE - 1;

		if (tq->nr_reported_acks < RXRPC_NR_TXQUEUE)
			naks &= (1UL << tq->nr_reported_acks) - 1;

		_debug("retr %16lx %u c=%08x [%x]",
		       tq->segment_acked, tq->nr_reported_acks, call->debug_id, tq->qbase);
		_debug("nack %16lx", naks);

		trace_rxrpc_resend_naks(call, tq, naks);
		while (naks) {
			unsigned int ix = __ffs(naks);
			struct rxrpc_txbuf *txb = tq->bufs[ix];

			__clear_bit(ix, &naks);
			if (after(txb->serial, call->acks_highest_serial))
				continue; /* Ack point not yet reached */

			rxrpc_see_txbuf(txb, rxrpc_txbuf_see_unacked);

			state.tq  = tq;
			state.seq = tq->qbase + ix;
			state.n   = 1;
			rxrpc_retransmit_data(call, &state, false);
		}

		/* Anything after the soft-ACK table up to and including
		 * ack.previousPacket will get ACK'd or NACK'd in due course,
		 * so don't worry about those here.  We do, however, need to
		 * consider retransmitting anything beyond that point.
		 */
		if (after_eq(call->tx_transmitted, tq->qbase) &&
		    tq->nr_reported_acks < RXRPC_NR_TXQUEUE &&
		    after(tq_top, call->acks_prev_seq)) {
			rxrpc_seq_t start = latest(call->acks_prev_seq,
						   tq->qbase + tq->nr_reported_acks);
			rxrpc_seq_t stop = earliest(tq_top, call->tx_transmitted);

			trace_rxrpc_resend_unrep(call, tq, start, stop);
			_debug("unrep %x-%x", start, stop);
			for (rxrpc_seq_t seq = start; before(seq, stop); seq++) {
				struct rxrpc_txbuf *txb = tq->bufs[seq & RXRPC_TXQ_MASK];

				if (ping_response &&
				    before(txb->serial, call->acks_highest_serial))
					break; /* Wasn't accounted for by a more recent ping. */
				state.tq  = tq;
				state.seq = seq;
				state.n   = 1;
				if (rxrpc_retransmit_data(call, &state, true))
					unacked = true;
			}
		}

		/* Work out the next retransmission timeout. */
		if (after_eq(call->tx_transmitted, tq->qbase) &&
		    ktime_before(tq->xmit_ts_base, lowest_xmit_ts)) {
			unsigned int lowest_us = UINT_MAX;

			for (int i = 0; i < RXRPC_NR_TXQUEUE; i++)
				if (!test_bit(i, &tq->segment_acked) &&
				    tq->segment_xmit_ts[i] < lowest_us)
					lowest_us = tq->segment_xmit_ts[i];
			_debug("lowest[%x] %llx %u", tq->qbase, tq->xmit_ts_base, lowest_us);

			if (lowest_us != UINT_MAX) {
				ktime_t lowest_ns = ktime_add_us(tq->xmit_ts_base, lowest_us);
				if (ktime_before(lowest_ns, lowest_xmit_ts))
					lowest_xmit_ts = lowest_ns;
			}
		}
	} while ((tq = tq->next));

	if (lowest_xmit_ts < KTIME_MAX) {
		ktime_t delay = rxrpc_get_rto_backoff(call->peer, state.did_send);
		ktime_t resend_at = ktime_add(lowest_xmit_ts, delay);

		_debug("delay %llu %lld", delay, ktime_sub(resend_at, state.now));
		call->resend_at = resend_at;
		trace_rxrpc_timer_set(call, resend_at - state.now,
				      rxrpc_timer_trace_resend_reset);
	} else {
		call->resend_at = KTIME_MAX;
		trace_rxrpc_timer_can(call, rxrpc_timer_trace_resend);
	}

	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 (!state.did_send) {
		ktime_t next_ping = ktime_add_us(call->acks_latest_ts,
						 call->peer->srtt_us >> 3);

		if (ktime_sub(next_ping, state.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 unsigned int rxrpc_tx_window_space(struct rxrpc_call *call)
{
	int winsize = min_t(unsigned int, call->tx_winsize,
			    call->cong_cwnd + call->cong_extra);
	int in_flight = call->tx_top - call->acks_hard_ack;

	return max(winsize - in_flight, 0);
}

/*
 * Decant some if the sendmsg prepared queue into the transmission buffer.
 */
static void rxrpc_decant_prepared_tx(struct rxrpc_call *call)
{
	int space = rxrpc_tx_window_space(call);

	if (!test_bit(RXRPC_CALL_EXPOSED, &call->flags)) {
		if (call->send_top == call->tx_top)
			return;
		rxrpc_expose_client_call(call);
	}

	while (space > 0) {
		struct rxrpc_txqueue *head_tq = NULL, *tq;
		struct rxrpc_txbuf *txb;
		rxrpc_seq_t send_top, seq;
		int count = 0, limit = min(space, max(call->peer->pmtud_jumbo, 1));

		/* Order send_top before the contents of the new txbufs and
		 * txqueue pointers
		 */
		send_top = smp_load_acquire(&call->send_top);
		if (call->tx_top == send_top)
			break;

		trace_rxrpc_transmit(call, send_top, space);

		tq = call->tx_qtail;
		seq = call->tx_top;
		trace_rxrpc_tq(call, tq, seq, rxrpc_tq_decant);

		do {
			int ix;

			seq++;
			ix = seq & RXRPC_TXQ_MASK;
			if (!ix) {
				tq = tq->next;
				trace_rxrpc_tq(call, tq, seq, rxrpc_tq_decant_more);
			}
			if (!head_tq)
				head_tq = tq;
			txb = tq->bufs[ix];
			count++;
			if (txb->len != RXRPC_JUMBO_DATALEN + sizeof(struct rxrpc_wire_header))
				break;
		} while (count < limit && before(seq, send_top));

		if (txb->flags & RXRPC_LAST_PACKET) {
			rxrpc_close_tx_phase(call);
			tq = NULL;
		}
		call->tx_qtail = tq;
		call->tx_top = seq;

		space -= count;
		rxrpc_transmit_data(call, head_tq, seq - (count - 1), count);
	}
}

static void rxrpc_transmit_some_data(struct rxrpc_call *call)
{
	switch (__rxrpc_call_state(call)) {
	case RXRPC_CALL_SERVER_ACK_REQUEST:
		if (call->tx_bottom == READ_ONCE(call->send_top))
			return;
		rxrpc_begin_service_reply(call);
		fallthrough;

	case RXRPC_CALL_SERVER_SEND_REPLY:
	case RXRPC_CALL_CLIENT_SEND_REQUEST:
		if (!rxrpc_tx_window_space(call))
			return;
		if (call->tx_bottom == READ_ONCE(call->send_top)) {
			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, did_receive = false, saw_ack = 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);

	/* 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;
	}

	while ((skb = __skb_dequeue(&call->rx_queue))) {
		struct rxrpc_skb_priv *sp = rxrpc_skb(skb);

		if (__rxrpc_call_is_complete(call))
			goto out;
		if (skb->mark == RXRPC_SKB_MARK_ERROR)
			goto out;

		saw_ack |= sp->hdr.type == RXRPC_PACKET_TYPE_ACK;

		rxrpc_input_call_packet(call, skb);
		rxrpc_free_skb(skb, rxrpc_skb_put_call_rx);
		did_receive = true;
	}

	/* 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 (saw_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, 0, false);

	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);
	} else {
		if (did_receive &&
		    call->peer->ackr_adv_pmtud &&
		    call->peer->pmtud_pending)
			rxrpc_send_probe_for_pmtud(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;
}