linux-brain/net/rxrpc/sysctl.c
David Howells 23ae6e3e8a rxrpc: Fix the excessive initial retransmission timeout
commit c410bf01933e5e09d142c66c3df9ad470a7eec13 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-05-27 17:46:48 +02:00

147 lines
3.8 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/* sysctls for configuring RxRPC operating parameters
*
* Copyright (C) 2014 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#include <linux/sysctl.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#include "ar-internal.h"
static struct ctl_table_header *rxrpc_sysctl_reg_table;
static const unsigned int four = 4;
static const unsigned int thirtytwo = 32;
static const unsigned int n_65535 = 65535;
static const unsigned int n_max_acks = RXRPC_RXTX_BUFF_SIZE - 1;
static const unsigned long one_jiffy = 1;
static const unsigned long max_jiffies = MAX_JIFFY_OFFSET;
/*
* RxRPC operating parameters.
*
* See Documentation/networking/rxrpc.txt and the variable definitions for more
* information on the individual parameters.
*/
static struct ctl_table rxrpc_sysctl_table[] = {
/* Values measured in milliseconds but used in jiffies */
{
.procname = "req_ack_delay",
.data = &rxrpc_requested_ack_delay,
.maxlen = sizeof(unsigned long),
.mode = 0644,
.proc_handler = proc_doulongvec_ms_jiffies_minmax,
.extra1 = (void *)&one_jiffy,
.extra2 = (void *)&max_jiffies,
},
{
.procname = "soft_ack_delay",
.data = &rxrpc_soft_ack_delay,
.maxlen = sizeof(unsigned long),
.mode = 0644,
.proc_handler = proc_doulongvec_ms_jiffies_minmax,
.extra1 = (void *)&one_jiffy,
.extra2 = (void *)&max_jiffies,
},
{
.procname = "idle_ack_delay",
.data = &rxrpc_idle_ack_delay,
.maxlen = sizeof(unsigned long),
.mode = 0644,
.proc_handler = proc_doulongvec_ms_jiffies_minmax,
.extra1 = (void *)&one_jiffy,
.extra2 = (void *)&max_jiffies,
},
{
.procname = "idle_conn_expiry",
.data = &rxrpc_conn_idle_client_expiry,
.maxlen = sizeof(unsigned long),
.mode = 0644,
.proc_handler = proc_doulongvec_ms_jiffies_minmax,
.extra1 = (void *)&one_jiffy,
.extra2 = (void *)&max_jiffies,
},
{
.procname = "idle_conn_fast_expiry",
.data = &rxrpc_conn_idle_client_fast_expiry,
.maxlen = sizeof(unsigned long),
.mode = 0644,
.proc_handler = proc_doulongvec_ms_jiffies_minmax,
.extra1 = (void *)&one_jiffy,
.extra2 = (void *)&max_jiffies,
},
/* Non-time values */
{
.procname = "max_client_conns",
.data = &rxrpc_max_client_connections,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = (void *)&rxrpc_reap_client_connections,
},
{
.procname = "reap_client_conns",
.data = &rxrpc_reap_client_connections,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = (void *)SYSCTL_ONE,
.extra2 = (void *)&rxrpc_max_client_connections,
},
{
.procname = "max_backlog",
.data = &rxrpc_max_backlog,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = (void *)&four,
.extra2 = (void *)&thirtytwo,
},
{
.procname = "rx_window_size",
.data = &rxrpc_rx_window_size,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = (void *)SYSCTL_ONE,
.extra2 = (void *)&n_max_acks,
},
{
.procname = "rx_mtu",
.data = &rxrpc_rx_mtu,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = (void *)SYSCTL_ONE,
.extra2 = (void *)&n_65535,
},
{
.procname = "rx_jumbo_max",
.data = &rxrpc_rx_jumbo_max,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = (void *)SYSCTL_ONE,
.extra2 = (void *)&four,
},
{ }
};
int __init rxrpc_sysctl_init(void)
{
rxrpc_sysctl_reg_table = register_net_sysctl(&init_net, "net/rxrpc",
rxrpc_sysctl_table);
if (!rxrpc_sysctl_reg_table)
return -ENOMEM;
return 0;
}
void rxrpc_sysctl_exit(void)
{
if (rxrpc_sysctl_reg_table)
unregister_net_sysctl_table(rxrpc_sysctl_reg_table);
}