ar-ack.c

linux 内核源代码

/* 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 ([e-mail])
 *
 * 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.
 */

#include <linux/module.h>
#include <linux/circ_buf.h>
#include <linux/net.h>
#include <linux/skbuff.h>
#include <linux/udp.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#include "ar-internal.h"

static unsigned rxrpc_ack_defer = 1;

static const char *rxrpc_acks[] = {
	"---", "REQ", "DUP", "OOS", "WIN", "MEM", "PNG", "PNR", "DLY", "IDL",
	"-?-"
};

static const s8 rxrpc_ack_priority[] = {
	[0]				= 0,
	[RXRPC_ACK_DELAY]		= 1,
	[RXRPC_ACK_REQUESTED]		= 2,
	[RXRPC_ACK_IDLE]		= 3,
	[RXRPC_ACK_PING_RESPONSE]	= 4,
	[RXRPC_ACK_DUPLICATE]		= 5,
	[RXRPC_ACK_OUT_OF_SEQUENCE]	= 6,
	[RXRPC_ACK_EXCEEDS_WINDOW]	= 7,
	[RXRPC_ACK_NOSPACE]		= 8,
};

/*
 * propose an ACK be sent
 */
void __rxrpc_propose_ACK(struct rxrpc_call *call, uint8_t ack_reason,
			 __be32 serial, bool immediate)
{
	unsigned long expiry;
	s8 prior = rxrpc_ack_priority[ack_reason];

	ASSERTCMP(prior, >, 0);

	_enter("{%d},%s,%%%x,%u",
	       call->debug_id, rxrpc_acks[ack_reason], ntohl(serial),
	       immediate);

	if (prior < rxrpc_ack_priority[call->ackr_reason]) {
		if (immediate)
			goto cancel_timer;
		return;
	}

	/* update DELAY, IDLE, REQUESTED and PING_RESPONSE ACK serial
	 * numbers */
	if (prior == rxrpc_ack_priority[call->ackr_reason]) {
		if (prior <= 4)
			call->ackr_serial = serial;
		if (immediate)
			goto cancel_timer;
		return;
	}

	call->ackr_reason = ack_reason;
	call->ackr_serial = serial;

	switch (ack_reason) {
	case RXRPC_ACK_DELAY:
		_debug("run delay timer");
		call->ack_timer.expires = jiffies + rxrpc_ack_timeout * HZ;
		add_timer(&call->ack_timer);
		return;

	case RXRPC_ACK_IDLE:
		if (!immediate) {
			_debug("run defer timer");
			expiry = 1;
			goto run_timer;
		}
		goto cancel_timer;

	case RXRPC_ACK_REQUESTED:
		if (!rxrpc_ack_defer)
			goto cancel_timer;
		if (!immediate || serial == cpu_to_be32(1)) {
			_debug("run defer timer");
			expiry = rxrpc_ack_defer;
			goto run_timer;
		}

	default:
		_debug("immediate ACK");
		goto cancel_timer;
	}

run_timer:
	expiry += jiffies;
	if (!timer_pending(&call->ack_timer) ||
	    time_after(call->ack_timer.expires, expiry))
		mod_timer(&call->ack_timer, expiry);
	return;

cancel_timer:
	_debug("cancel timer %%%u", ntohl(serial));
	try_to_del_timer_sync(&call->ack_timer);
	read_lock_bh(&call->state_lock);
	if (call->state <= RXRPC_CALL_COMPLETE &&
	    !test_and_set_bit(RXRPC_CALL_ACK, &call->events))
		rxrpc_queue_call(call);
	read_unlock_bh(&call->state_lock);
}

/*
 * propose an ACK be sent, locking the call structure
 */
void rxrpc_propose_ACK(struct rxrpc_call *call, uint8_t ack_reason,
		       __be32 serial, bool immediate)
{
	s8 prior = rxrpc_ack_priority[ack_reason];

	if (prior > rxrpc_ack_priority[call->ackr_reason]) {
		spin_lock_bh(&call->lock);
		__rxrpc_propose_ACK(call, ack_reason, serial, immediate);
		spin_unlock_bh(&call->lock);
	}
}

/*
 * set the resend timer
 */
static void rxrpc_set_resend(struct rxrpc_call *call, u8 resend,
			     unsigned long resend_at)
{
	read_lock_bh(&call->state_lock);
	if (call->state >= RXRPC_CALL_COMPLETE)
		resend = 0;

	if (resend & 1) {
		_debug("SET RESEND");
		set_bit(RXRPC_CALL_RESEND, &call->events);
	}

	if (resend & 2) {
		_debug("MODIFY RESEND TIMER");
		set_bit(RXRPC_CALL_RUN_RTIMER, &call->flags);
		mod_timer(&call->resend_timer, resend_at);
	} else {
		_debug("KILL RESEND TIMER");
		del_timer_sync(&call->resend_timer);
		clear_bit(RXRPC_CALL_RESEND_TIMER, &call->events);
		clear_bit(RXRPC_CALL_RUN_RTIMER, &call->flags);
	}
	read_unlock_bh(&call->state_lock);
}

/*
 * resend packets
 */
static void rxrpc_resend(struct rxrpc_call *call)
{
	struct rxrpc_skb_priv *sp;
	struct rxrpc_header *hdr;
	struct sk_buff *txb;
	unsigned long *p_txb, resend_at;
	int loop, stop;
	u8 resend;

	_enter("{%d,%d,%d,%d},",
	       call->acks_hard, call->acks_unacked,
	       atomic_read(&call->sequence),
	       CIRC_CNT(call->acks_head, call->acks_tail, call->acks_winsz));

	stop = 0;
	resend = 0;
	resend_at = 0;

	for (loop = call->acks_tail;
	     loop != call->acks_head || stop;
	     loop = (loop + 1) &  (call->acks_winsz - 1)
	     ) {
		p_txb = call->acks_window + loop;
		smp_read_barrier_depends();
		if (*p_txb & 1)
			continue;

		txb = (struct sk_buff *) *p_txb;
		sp = rxrpc_skb(txb);

		if (sp->need_resend) {
			sp->need_resend = 0;

			/* each Tx packet has a new serial number */
			sp->hdr.serial =
				htonl(atomic_inc_return(&call->conn->serial));

			hdr = (struct rxrpc_header *) txb->head;
			hdr->serial = sp->hdr.serial;

			_proto("Tx DATA %%%u { #%d }",
			       ntohl(sp->hdr.serial), ntohl(sp->hdr.seq));
			if (rxrpc_send_packet(call->conn->trans, txb) < 0) {
				stop = 0;
				sp->resend_at = jiffies + 3;
			} else {
				sp->resend_at =
					jiffies + rxrpc_resend_timeout * HZ;
			}
		}

		if (time_after_eq(jiffies + 1, sp->resend_at)) {
			sp->need_resend = 1;
			resend |= 1;
		} else if (resend & 2) {
			if (time_before(sp->resend_at, resend_at))
				resend_at = sp->resend_at;
		} else {
			resend_at = sp->resend_at;
			resend |= 2;
		}
	}

	rxrpc_set_resend(call, resend, resend_at);
	_leave("");
}

/*
 * handle resend timer expiry
 */
static void rxrpc_resend_timer(struct rxrpc_call *call)
{
	struct rxrpc_skb_priv *sp;
	struct sk_buff *txb;
	unsigned long *p_txb, resend_at;
	int loop;
	u8 resend;

	_enter("%d,%d,%d",
	       call->acks_tail, call->acks_unacked, call->acks_head);

	resend = 0;
	resend_at = 0;

	for (loop = call->acks_unacked;
	     loop != call->acks_head;
	     loop = (loop + 1) &  (call->acks_winsz - 1)
	     ) {
		p_txb = call->acks_window + loop;
		smp_read_barrier_depends();
		txb = (struct sk_buff *) (*p_txb & ~1);
		sp = rxrpc_skb(txb);

		ASSERT(!(*p_txb & 1));

		if (sp->need_resend) {
			;
		} else if (time_after_eq(jiffies + 1, sp->resend_at)) {
			sp->need_resend = 1;
			resend |= 1;
		} else if (resend & 2) {
			if (time_before(sp->resend_at, resend_at))
				resend_at = sp->resend_at;
		} else {
			resend_at = sp->resend_at;
			resend |= 2;
		}
	}

	rxrpc_set_resend(call, resend, resend_at);
	_leave("");
}

/*
 * process soft ACKs of our transmitted packets
 * - these indicate packets the peer has or has not received, but hasn't yet
 *   given to the consumer, and so can still be discarded and re-requested
 */
static int rxrpc_process_soft_ACKs(struct rxrpc_call *call,
				   struct rxrpc_ackpacket *ack,
				   struct sk_buff *skb)
{
	struct rxrpc_skb_priv *sp;
	struct sk_buff *txb;
	unsigned long *p_txb, resend_at;
	int loop;
	u8 sacks[RXRPC_MAXACKS], resend;

	_enter("{%d,%d},{%d},",
	       call->acks_hard,
	       CIRC_CNT(call->acks_head, call->acks_tail, call->acks_winsz),
	       ack->nAcks);

	if (skb_copy_bits(skb, 0, sacks, ack->nAcks) < 0)
		goto protocol_error;

	resend = 0;
	resend_at = 0;
	for (loop = 0; loop < ack->nAcks; loop++) {
		p_txb = call->acks_window;
		p_txb += (call->acks_tail + loop) & (call->acks_winsz - 1);
		smp_read_barrier_depends();
		txb = (struct sk_buff *) (*p_txb & ~1);
		sp = rxrpc_skb(txb);

		switch (sacks[loop]) {
		case RXRPC_ACK_TYPE_ACK:
			sp->need_resend = 0;
			*p_txb |= 1;
			break;
		case RXRPC_ACK_TYPE_NACK:
			sp->need_resend = 1;
			*p_txb &= ~1;
			resend = 1;
			break;
		default:
			_debug("Unsupported ACK type %d", sacks[loop]);
			goto protocol_error;
		}
	}

	smp_mb();
	call->acks_unacked = (call->acks_tail + loop) & (call->acks_winsz - 1);

	/* anything not explicitly ACK'd is implicitly NACK'd, but may just not
	 * have been received or processed yet by the far end */
	for (loop = call->acks_unacked;
	     loop != call->acks_head;
	     loop = (loop + 1) &  (call->acks_winsz - 1)
	     ) {
		p_txb = call->acks_window + loop;
		smp_read_barrier_depends();
		txb = (struct sk_buff *) (*p_txb & ~1);
		sp = rxrpc_skb(txb);

		if (*p_txb & 1) {
			/* packet must have been discarded */
			sp->need_resend = 1;
			*p_txb &= ~1;
			resend |= 1;
		} else if (sp->need_resend) {
			;
		} else if (time_after_eq(jiffies + 1, sp->resend_at)) {
			sp->need_resend = 1;
			resend |= 1;
		} else if (resend & 2) {
			if (time_before(sp->resend_at, resend_at))
				resend_at = sp->resend_at;
		} else {
			resend_at = sp->resend_at;
			resend |= 2;
		}
	}

	rxrpc_set_resend(call, resend, resend_at);
	_leave(" = 0");
	return 0;

protocol_error:
	_leave(" = -EPROTO");
	return -EPROTO;
}

/*
 * discard hard-ACK'd packets from the Tx window
 */
static void rxrpc_rotate_tx_window(struct rxrpc_call *call, u32 hard)
{
	struct rxrpc_skb_priv *sp;
	unsigned long _skb;
	int tail = call->acks_tail, old_tail;
	int win = CIRC_CNT(call->acks_head, tail, call->acks_winsz);

	_enter("{%u,%u},%u", call->acks_hard, win, hard);

	ASSERTCMP(hard - call->acks_hard, <=, win);

	while (call->acks_hard < hard) {
		smp_read_barrier_depends();
		_skb = call->acks_window[tail] & ~1;
		sp = rxrpc_skb((struct sk_buff *) _skb);
		rxrpc_free_skb((struct sk_buff *) _skb);
		old_tail = tail;
		tail = (tail + 1) & (call->acks_winsz - 1);
		call->acks_tail = tail;
		if (call->acks_unacked == old_tail)
			call->acks_unacked = tail;
		call->acks_hard++;
	}

	wake_up(&call->tx_waitq);
}

/*
 * clear the Tx window in the event of a failure
 */
static void rxrpc_clear_tx_window(struct rxrpc_call *call)
{
	rxrpc_rotate_tx_window(call, atomic_read(&call->sequence));
}

/*
 * drain the out of sequence received packet queue into the packet Rx queue
 */
static int rxrpc_drain_rx_oos_queue(struct rxrpc_call *call)
{
	struct rxrpc_skb_priv *sp;
	struct sk_buff *skb;
	bool terminal;
	int ret;

	_enter("{%d,%d}", call->rx_data_post, call->rx_first_oos);

	spin_lock_bh(&call->lock);

	ret = -ECONNRESET;
	if (test_bit(RXRPC_CALL_RELEASED, &call->flags))
		goto socket_unavailable;

	skb = skb_dequeue(&call->rx_oos_queue);
	if (skb) {
		sp = rxrpc_skb(skb);

		_debug("drain OOS packet %d [%d]",
		       ntohl(sp->hdr.seq), call->rx_first_oos);

		if (ntohl(sp->hdr.seq) != call->rx_first_oos) {
			skb_queue_head(&call->rx_oos_queue, skb);
			call->rx_first_oos = ntohl(rxrpc_skb(skb)->hdr.seq);
			_debug("requeue %p {%u}", skb, call->rx_first_oos);
		} else {