forked from Minki/linux
c410bf0193
rxrpc currently uses a fixed 4s retransmission timeout until the RTT is
sufficiently sampled. This can cause problems with some fileservers with
calls to the cache manager in the afs filesystem being dropped from the
fileserver because a packet goes missing and the retransmission timeout is
greater than the call expiry timeout.
Fix this by:
(1) Copying the RTT/RTO calculation code from Linux's TCP implementation
and altering it to fit rxrpc.
(2) Altering the various users of the RTT to make use of the new SRTT
value.
(3) Replacing the use of rxrpc_resend_timeout to use the calculated RTO
value instead (which is needed in jiffies), along with a backoff.
Notes:
(1) rxrpc provides RTT samples by matching the serial numbers on outgoing
DATA packets that have the RXRPC_REQUEST_ACK set and PING ACK packets
against the reference serial number in incoming REQUESTED ACK and
PING-RESPONSE ACK packets.
(2) Each packet that is transmitted on an rxrpc connection gets a new
per-connection serial number, even for retransmissions, so an ACK can
be cross-referenced to a specific trigger packet. This allows RTT
information to be drawn from retransmitted DATA packets also.
(3) rxrpc maintains the RTT/RTO state on the rxrpc_peer record rather than
on an rxrpc_call because many RPC calls won't live long enough to
generate more than one sample.
(4) The calculated SRTT value is in units of 8ths of a microsecond rather
than nanoseconds.
The (S)RTT and RTO values are displayed in /proc/net/rxrpc/peers.
Fixes: 17926a7932
([AF_RXRPC]: Provide secure RxRPC sockets for use by userspace and kernel both"")
Signed-off-by: David Howells <dhowells@redhat.com>
457 lines
12 KiB
C
457 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* Management of Tx window, Tx resend, ACKs and out-of-sequence reception
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*
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* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/circ_buf.h>
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#include <linux/net.h>
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#include <linux/skbuff.h>
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#include <linux/slab.h>
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#include <linux/udp.h>
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#include <net/sock.h>
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#include <net/af_rxrpc.h>
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#include "ar-internal.h"
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/*
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* Propose a PING ACK be sent.
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*/
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static void rxrpc_propose_ping(struct rxrpc_call *call,
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bool immediate, bool background)
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{
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if (immediate) {
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if (background &&
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!test_and_set_bit(RXRPC_CALL_EV_PING, &call->events))
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rxrpc_queue_call(call);
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} else {
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unsigned long now = jiffies;
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unsigned long ping_at = now + rxrpc_idle_ack_delay;
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if (time_before(ping_at, call->ping_at)) {
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WRITE_ONCE(call->ping_at, ping_at);
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rxrpc_reduce_call_timer(call, ping_at, now,
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rxrpc_timer_set_for_ping);
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}
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}
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}
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/*
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* propose an ACK be sent
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*/
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static void __rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason,
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u32 serial, bool immediate, bool background,
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enum rxrpc_propose_ack_trace why)
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{
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enum rxrpc_propose_ack_outcome outcome = rxrpc_propose_ack_use;
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unsigned long expiry = rxrpc_soft_ack_delay;
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s8 prior = rxrpc_ack_priority[ack_reason];
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/* Pings are handled specially because we don't want to accidentally
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* lose a ping response by subsuming it into a ping.
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*/
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if (ack_reason == RXRPC_ACK_PING) {
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rxrpc_propose_ping(call, immediate, background);
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goto trace;
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}
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/* Update DELAY, IDLE, REQUESTED and PING_RESPONSE ACK serial
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* numbers, but we don't alter the timeout.
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*/
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_debug("prior %u %u vs %u %u",
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ack_reason, prior,
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call->ackr_reason, rxrpc_ack_priority[call->ackr_reason]);
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if (ack_reason == call->ackr_reason) {
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if (RXRPC_ACK_UPDATEABLE & (1 << ack_reason)) {
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outcome = rxrpc_propose_ack_update;
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call->ackr_serial = serial;
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}
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if (!immediate)
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goto trace;
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} else if (prior > rxrpc_ack_priority[call->ackr_reason]) {
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call->ackr_reason = ack_reason;
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call->ackr_serial = serial;
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} else {
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outcome = rxrpc_propose_ack_subsume;
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}
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switch (ack_reason) {
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case RXRPC_ACK_REQUESTED:
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if (rxrpc_requested_ack_delay < expiry)
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expiry = rxrpc_requested_ack_delay;
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if (serial == 1)
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immediate = false;
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break;
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case RXRPC_ACK_DELAY:
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if (rxrpc_soft_ack_delay < expiry)
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expiry = rxrpc_soft_ack_delay;
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break;
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case RXRPC_ACK_IDLE:
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if (rxrpc_idle_ack_delay < expiry)
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expiry = rxrpc_idle_ack_delay;
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break;
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default:
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immediate = true;
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break;
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}
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if (test_bit(RXRPC_CALL_EV_ACK, &call->events)) {
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_debug("already scheduled");
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} else if (immediate || expiry == 0) {
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_debug("immediate ACK %lx", call->events);
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if (!test_and_set_bit(RXRPC_CALL_EV_ACK, &call->events) &&
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background)
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rxrpc_queue_call(call);
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} else {
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unsigned long now = jiffies, ack_at;
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if (call->peer->srtt_us != 0)
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ack_at = usecs_to_jiffies(call->peer->srtt_us >> 3);
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else
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ack_at = expiry;
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ack_at += READ_ONCE(call->tx_backoff);
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ack_at += now;
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if (time_before(ack_at, call->ack_at)) {
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WRITE_ONCE(call->ack_at, ack_at);
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rxrpc_reduce_call_timer(call, ack_at, now,
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rxrpc_timer_set_for_ack);
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}
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}
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trace:
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trace_rxrpc_propose_ack(call, why, ack_reason, serial, immediate,
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background, outcome);
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}
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/*
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* propose an ACK be sent, locking the call structure
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*/
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void rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason,
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u32 serial, bool immediate, bool background,
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enum rxrpc_propose_ack_trace why)
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{
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spin_lock_bh(&call->lock);
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__rxrpc_propose_ACK(call, ack_reason, serial,
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immediate, background, why);
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spin_unlock_bh(&call->lock);
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}
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/*
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* Handle congestion being detected by the retransmit timeout.
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*/
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static void rxrpc_congestion_timeout(struct rxrpc_call *call)
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{
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set_bit(RXRPC_CALL_RETRANS_TIMEOUT, &call->flags);
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}
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/*
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* Perform retransmission of NAK'd and unack'd packets.
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*/
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static void rxrpc_resend(struct rxrpc_call *call, unsigned long now_j)
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{
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struct sk_buff *skb;
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unsigned long resend_at, rto_j;
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rxrpc_seq_t cursor, seq, top;
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ktime_t now, max_age, oldest, ack_ts;
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int ix;
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u8 annotation, anno_type, retrans = 0, unacked = 0;
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_enter("{%d,%d}", call->tx_hard_ack, call->tx_top);
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rto_j = call->peer->rto_j;
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now = ktime_get_real();
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max_age = ktime_sub(now, jiffies_to_usecs(rto_j));
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spin_lock_bh(&call->lock);
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cursor = call->tx_hard_ack;
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top = call->tx_top;
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ASSERT(before_eq(cursor, top));
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if (cursor == top)
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goto out_unlock;
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/* Scan the packet list without dropping the lock and decide which of
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* the packets in the Tx buffer we're going to resend and what the new
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* resend timeout will be.
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*/
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trace_rxrpc_resend(call, (cursor + 1) & RXRPC_RXTX_BUFF_MASK);
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oldest = now;
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for (seq = cursor + 1; before_eq(seq, top); seq++) {
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ix = seq & RXRPC_RXTX_BUFF_MASK;
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annotation = call->rxtx_annotations[ix];
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anno_type = annotation & RXRPC_TX_ANNO_MASK;
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annotation &= ~RXRPC_TX_ANNO_MASK;
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if (anno_type == RXRPC_TX_ANNO_ACK)
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continue;
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skb = call->rxtx_buffer[ix];
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rxrpc_see_skb(skb, rxrpc_skb_seen);
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if (anno_type == RXRPC_TX_ANNO_UNACK) {
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if (ktime_after(skb->tstamp, max_age)) {
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if (ktime_before(skb->tstamp, oldest))
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oldest = skb->tstamp;
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continue;
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}
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if (!(annotation & RXRPC_TX_ANNO_RESENT))
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unacked++;
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}
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/* Okay, we need to retransmit a packet. */
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call->rxtx_annotations[ix] = RXRPC_TX_ANNO_RETRANS | annotation;
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retrans++;
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trace_rxrpc_retransmit(call, seq, annotation | anno_type,
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ktime_to_ns(ktime_sub(skb->tstamp, max_age)));
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}
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resend_at = nsecs_to_jiffies(ktime_to_ns(ktime_sub(now, oldest)));
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resend_at += jiffies + rto_j;
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WRITE_ONCE(call->resend_at, resend_at);
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if (unacked)
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rxrpc_congestion_timeout(call);
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/* If there was nothing that needed retransmission then it's likely
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* that an ACK got lost somewhere. Send a ping to find out instead of
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* retransmitting data.
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*/
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if (!retrans) {
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rxrpc_reduce_call_timer(call, resend_at, now_j,
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rxrpc_timer_set_for_resend);
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spin_unlock_bh(&call->lock);
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ack_ts = ktime_sub(now, call->acks_latest_ts);
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if (ktime_to_us(ack_ts) < (call->peer->srtt_us >> 3))
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goto out;
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rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, true, false,
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rxrpc_propose_ack_ping_for_lost_ack);
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rxrpc_send_ack_packet(call, true, NULL);
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goto out;
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}
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/* Now go through the Tx window and perform the retransmissions. We
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* have to drop the lock for each send. If an ACK comes in whilst the
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* lock is dropped, it may clear some of the retransmission markers for
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* packets that it soft-ACKs.
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*/
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for (seq = cursor + 1; before_eq(seq, top); seq++) {
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ix = seq & RXRPC_RXTX_BUFF_MASK;
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annotation = call->rxtx_annotations[ix];
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anno_type = annotation & RXRPC_TX_ANNO_MASK;
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if (anno_type != RXRPC_TX_ANNO_RETRANS)
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continue;
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skb = call->rxtx_buffer[ix];
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rxrpc_get_skb(skb, rxrpc_skb_got);
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spin_unlock_bh(&call->lock);
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if (rxrpc_send_data_packet(call, skb, true) < 0) {
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rxrpc_free_skb(skb, rxrpc_skb_freed);
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return;
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}
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if (rxrpc_is_client_call(call))
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rxrpc_expose_client_call(call);
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rxrpc_free_skb(skb, rxrpc_skb_freed);
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spin_lock_bh(&call->lock);
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/* We need to clear the retransmit state, but there are two
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* things we need to be aware of: A new ACK/NAK might have been
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* received and the packet might have been hard-ACK'd (in which
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* case it will no longer be in the buffer).
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*/
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if (after(seq, call->tx_hard_ack)) {
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annotation = call->rxtx_annotations[ix];
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anno_type = annotation & RXRPC_TX_ANNO_MASK;
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if (anno_type == RXRPC_TX_ANNO_RETRANS ||
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anno_type == RXRPC_TX_ANNO_NAK) {
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annotation &= ~RXRPC_TX_ANNO_MASK;
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annotation |= RXRPC_TX_ANNO_UNACK;
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}
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annotation |= RXRPC_TX_ANNO_RESENT;
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call->rxtx_annotations[ix] = annotation;
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}
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if (after(call->tx_hard_ack, seq))
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seq = call->tx_hard_ack;
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}
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out_unlock:
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spin_unlock_bh(&call->lock);
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out:
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_leave("");
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}
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/*
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* Handle retransmission and deferred ACK/abort generation.
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*/
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void rxrpc_process_call(struct work_struct *work)
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{
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struct rxrpc_call *call =
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container_of(work, struct rxrpc_call, processor);
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rxrpc_serial_t *send_ack;
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unsigned long now, next, t;
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unsigned int iterations = 0;
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rxrpc_see_call(call);
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//printk("\n--------------------\n");
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_enter("{%d,%s,%lx}",
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call->debug_id, rxrpc_call_states[call->state], call->events);
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recheck_state:
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/* Limit the number of times we do this before returning to the manager */
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iterations++;
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if (iterations > 5)
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goto requeue;
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if (test_and_clear_bit(RXRPC_CALL_EV_ABORT, &call->events)) {
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rxrpc_send_abort_packet(call);
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goto recheck_state;
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}
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if (call->state == RXRPC_CALL_COMPLETE) {
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del_timer_sync(&call->timer);
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rxrpc_notify_socket(call);
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goto out_put;
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}
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/* Work out if any timeouts tripped */
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now = jiffies;
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t = READ_ONCE(call->expect_rx_by);
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if (time_after_eq(now, t)) {
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trace_rxrpc_timer(call, rxrpc_timer_exp_normal, now);
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set_bit(RXRPC_CALL_EV_EXPIRED, &call->events);
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}
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t = READ_ONCE(call->expect_req_by);
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if (call->state == RXRPC_CALL_SERVER_RECV_REQUEST &&
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time_after_eq(now, t)) {
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trace_rxrpc_timer(call, rxrpc_timer_exp_idle, now);
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set_bit(RXRPC_CALL_EV_EXPIRED, &call->events);
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}
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t = READ_ONCE(call->expect_term_by);
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if (time_after_eq(now, t)) {
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trace_rxrpc_timer(call, rxrpc_timer_exp_hard, now);
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set_bit(RXRPC_CALL_EV_EXPIRED, &call->events);
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}
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t = READ_ONCE(call->ack_at);
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if (time_after_eq(now, t)) {
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trace_rxrpc_timer(call, rxrpc_timer_exp_ack, now);
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cmpxchg(&call->ack_at, t, now + MAX_JIFFY_OFFSET);
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set_bit(RXRPC_CALL_EV_ACK, &call->events);
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}
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t = READ_ONCE(call->ack_lost_at);
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if (time_after_eq(now, t)) {
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trace_rxrpc_timer(call, rxrpc_timer_exp_lost_ack, now);
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cmpxchg(&call->ack_lost_at, t, now + MAX_JIFFY_OFFSET);
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set_bit(RXRPC_CALL_EV_ACK_LOST, &call->events);
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}
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t = READ_ONCE(call->keepalive_at);
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if (time_after_eq(now, t)) {
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trace_rxrpc_timer(call, rxrpc_timer_exp_keepalive, now);
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cmpxchg(&call->keepalive_at, t, now + MAX_JIFFY_OFFSET);
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rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, true, true,
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rxrpc_propose_ack_ping_for_keepalive);
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set_bit(RXRPC_CALL_EV_PING, &call->events);
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}
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t = READ_ONCE(call->ping_at);
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if (time_after_eq(now, t)) {
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trace_rxrpc_timer(call, rxrpc_timer_exp_ping, now);
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cmpxchg(&call->ping_at, t, now + MAX_JIFFY_OFFSET);
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set_bit(RXRPC_CALL_EV_PING, &call->events);
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}
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t = READ_ONCE(call->resend_at);
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if (time_after_eq(now, t)) {
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trace_rxrpc_timer(call, rxrpc_timer_exp_resend, now);
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cmpxchg(&call->resend_at, t, now + MAX_JIFFY_OFFSET);
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set_bit(RXRPC_CALL_EV_RESEND, &call->events);
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}
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/* Process events */
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if (test_and_clear_bit(RXRPC_CALL_EV_EXPIRED, &call->events)) {
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if (test_bit(RXRPC_CALL_RX_HEARD, &call->flags) &&
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(int)call->conn->hi_serial - (int)call->rx_serial > 0) {
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trace_rxrpc_call_reset(call);
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rxrpc_abort_call("EXP", call, 0, RX_USER_ABORT, -ECONNRESET);
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} else {
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rxrpc_abort_call("EXP", call, 0, RX_USER_ABORT, -ETIME);
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}
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set_bit(RXRPC_CALL_EV_ABORT, &call->events);
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goto recheck_state;
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}
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send_ack = NULL;
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if (test_and_clear_bit(RXRPC_CALL_EV_ACK_LOST, &call->events)) {
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call->acks_lost_top = call->tx_top;
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rxrpc_propose_ACK(call, RXRPC_ACK_PING, 0, true, false,
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rxrpc_propose_ack_ping_for_lost_ack);
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send_ack = &call->acks_lost_ping;
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}
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if (test_and_clear_bit(RXRPC_CALL_EV_ACK, &call->events) ||
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send_ack) {
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if (call->ackr_reason) {
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rxrpc_send_ack_packet(call, false, send_ack);
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goto recheck_state;
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}
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}
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if (test_and_clear_bit(RXRPC_CALL_EV_PING, &call->events)) {
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rxrpc_send_ack_packet(call, true, NULL);
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goto recheck_state;
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}
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if (test_and_clear_bit(RXRPC_CALL_EV_RESEND, &call->events)) {
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rxrpc_resend(call, now);
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goto recheck_state;
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}
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/* Make sure the timer is restarted */
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next = call->expect_rx_by;
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#define set(T) { t = READ_ONCE(T); if (time_before(t, next)) next = t; }
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set(call->expect_req_by);
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set(call->expect_term_by);
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set(call->ack_at);
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set(call->ack_lost_at);
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set(call->resend_at);
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set(call->keepalive_at);
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set(call->ping_at);
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now = jiffies;
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if (time_after_eq(now, next))
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goto recheck_state;
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rxrpc_reduce_call_timer(call, next, now, rxrpc_timer_restart);
|
|
|
|
/* other events may have been raised since we started checking */
|
|
if (call->events && call->state < RXRPC_CALL_COMPLETE)
|
|
goto requeue;
|
|
|
|
out_put:
|
|
rxrpc_put_call(call, rxrpc_call_put);
|
|
out:
|
|
_leave("");
|
|
return;
|
|
|
|
requeue:
|
|
__rxrpc_queue_call(call);
|
|
goto out;
|
|
}
|