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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>
76 lines
2.3 KiB
C
76 lines
2.3 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* Miscellaneous bits
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*
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* Copyright (C) 2016 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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#include <linux/kernel.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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* The maximum listening backlog queue size that may be set on a socket by
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* listen().
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*/
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unsigned int rxrpc_max_backlog __read_mostly = 10;
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/*
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* How long to wait before scheduling ACK generation after seeing a
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* packet with RXRPC_REQUEST_ACK set (in jiffies).
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*/
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unsigned long rxrpc_requested_ack_delay = 1;
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/*
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* How long to wait before scheduling an ACK with subtype DELAY (in jiffies).
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*
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* We use this when we've received new data packets. If those packets aren't
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* all consumed within this time we will send a DELAY ACK if an ACK was not
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* requested to let the sender know it doesn't need to resend.
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*/
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unsigned long rxrpc_soft_ack_delay = HZ;
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/*
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* How long to wait before scheduling an ACK with subtype IDLE (in jiffies).
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*
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* We use this when we've consumed some previously soft-ACK'd packets when
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* further packets aren't immediately received to decide when to send an IDLE
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* ACK let the other end know that it can free up its Tx buffer space.
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*/
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unsigned long rxrpc_idle_ack_delay = HZ / 2;
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/*
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* Receive window size in packets. This indicates the maximum number of
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* unconsumed received packets we're willing to retain in memory. Once this
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* limit is hit, we should generate an EXCEEDS_WINDOW ACK and discard further
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* packets.
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*/
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unsigned int rxrpc_rx_window_size = RXRPC_INIT_RX_WINDOW_SIZE;
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#if (RXRPC_RXTX_BUFF_SIZE - 1) < RXRPC_INIT_RX_WINDOW_SIZE
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#error Need to reduce RXRPC_INIT_RX_WINDOW_SIZE
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#endif
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/*
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* Maximum Rx MTU size. This indicates to the sender the size of jumbo packet
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* made by gluing normal packets together that we're willing to handle.
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*/
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unsigned int rxrpc_rx_mtu = 5692;
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/*
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* The maximum number of fragments in a received jumbo packet that we tell the
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* sender that we're willing to handle.
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*/
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unsigned int rxrpc_rx_jumbo_max = 4;
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const s8 rxrpc_ack_priority[] = {
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[0] = 0,
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[RXRPC_ACK_DELAY] = 1,
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[RXRPC_ACK_REQUESTED] = 2,
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[RXRPC_ACK_IDLE] = 3,
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[RXRPC_ACK_DUPLICATE] = 4,
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[RXRPC_ACK_OUT_OF_SEQUENCE] = 5,
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[RXRPC_ACK_EXCEEDS_WINDOW] = 6,
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[RXRPC_ACK_NOSPACE] = 7,
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[RXRPC_ACK_PING_RESPONSE] = 8,
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};
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