linux/net/rxrpc/rtt.c

// SPDX-License-Identifier: GPL-2.0
/* RTT/RTO calculation.
 *
 * Adapted from TCP for AF_RXRPC by David Howells ([email protected])
 *
 * https://tools.ietf.org/html/rfc6298
 * https://tools.ietf.org/html/rfc1122#section-4.2.3.1
 * http://ccr.sigcomm.org/archive/1995/jan95/ccr-9501-partridge87.pdf
 */

#include <linux/net.h>
#include "ar-internal.h"

#define RXRPC_RTO_MAX …
#define RXRPC_TIMEOUT_INIT …
#define rxrpc_jiffies32 …

static u32 rxrpc_rto_min_us(struct rxrpc_peer *peer)
{ … }

static u32 __rxrpc_set_rto(const struct rxrpc_peer *peer)
{ … }

static u32 rxrpc_bound_rto(u32 rto)
{ … }

/*
 * Called to compute a smoothed rtt estimate. The data fed to this
 * routine either comes from timestamps, or from segments that were
 * known _not_ to have been retransmitted [see Karn/Partridge
 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
 * piece by Van Jacobson.
 * NOTE: the next three routines used to be one big routine.
 * To save cycles in the RFC 1323 implementation it was better to break
 * it up into three procedures. -- erics
 */
static void rxrpc_rtt_estimator(struct rxrpc_peer *peer, long sample_rtt_us)
{ … }

/*
 * Calculate rto without backoff.  This is the second half of Van Jacobson's
 * routine referred to above.
 */
static void rxrpc_set_rto(struct rxrpc_peer *peer)
{ … }

static void rxrpc_ack_update_rtt(struct rxrpc_peer *peer, long rtt_us)
{ … }

/*
 * Add RTT information to cache.  This is called in softirq mode and has
 * exclusive access to the peer RTT data.
 */
void rxrpc_peer_add_rtt(struct rxrpc_call *call, enum rxrpc_rtt_rx_trace why,
			int rtt_slot,
			rxrpc_serial_t send_serial, rxrpc_serial_t resp_serial,
			ktime_t send_time, ktime_t resp_time)
{ … }

/*
 * Get the retransmission timeout to set in nanoseconds, backing it off each
 * time we retransmit.
 */
ktime_t rxrpc_get_rto_backoff(struct rxrpc_peer *peer, bool retrans)
{ … }

void rxrpc_peer_init_rtt(struct rxrpc_peer *peer)
{ … }