linux/net/ipv4/tcp_veno.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * TCP Veno congestion control
 *
 * This is based on the congestion detection/avoidance scheme described in
 *    C. P. Fu, S. C. Liew.
 *    "TCP Veno: TCP Enhancement for Transmission over Wireless Access Networks."
 *    IEEE Journal on Selected Areas in Communication,
 *    Feb. 2003.
 * 	See https://www.ie.cuhk.edu.hk/fileadmin/staff_upload/soung/Journal/J3.pdf
 */

#include <linux/mm.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/inet_diag.h>

#include <net/tcp.h>

/* Default values of the Veno variables, in fixed-point representation
 * with V_PARAM_SHIFT bits to the right of the binary point.
 */
#define V_PARAM_SHIFT …
static const int beta = …;

/* Veno variables */
struct veno { … };

/* There are several situations when we must "re-start" Veno:
 *
 *  o when a connection is established
 *  o after an RTO
 *  o after fast recovery
 *  o when we send a packet and there is no outstanding
 *    unacknowledged data (restarting an idle connection)
 *
 */
static inline void veno_enable(struct sock *sk)
{ … }

static inline void veno_disable(struct sock *sk)
{ … }

static void tcp_veno_init(struct sock *sk)
{ … }

/* Do rtt sampling needed for Veno. */
static void tcp_veno_pkts_acked(struct sock *sk,
				const struct ack_sample *sample)
{ … }

static void tcp_veno_state(struct sock *sk, u8 ca_state)
{ … }

/*
 * If the connection is idle and we are restarting,
 * then we don't want to do any Veno calculations
 * until we get fresh rtt samples.  So when we
 * restart, we reset our Veno state to a clean
 * state. After we get acks for this flight of
 * packets, _then_ we can make Veno calculations
 * again.
 */
static void tcp_veno_cwnd_event(struct sock *sk, enum tcp_ca_event event)
{ … }

static void tcp_veno_cong_avoid(struct sock *sk, u32 ack, u32 acked)
{ … }

/* Veno MD phase */
static u32 tcp_veno_ssthresh(struct sock *sk)
{ … }

static struct tcp_congestion_ops tcp_veno __read_mostly = …;

static int __init tcp_veno_register(void)
{ … }

static void __exit tcp_veno_unregister(void)
{ … }

module_init(…) …;
module_exit(tcp_veno_unregister);

MODULE_AUTHOR(…) …;
MODULE_LICENSE(…) …;
MODULE_DESCRIPTION(…) …;