net/ipv4/tcp_yeah.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  *
  *   YeAH TCP
  *
  * For further details look at:
  *   https://web.archive.org/web/20080316215752/http://wil.cs.caltech.edu/pfldnet2007/paper/YeAH_TCP.pdf
  *
  */
 #include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/skbuff.h>
 #include <linux/inet_diag.h>

 #include <net/tcp.h>

 #include "tcp_vegas.h"

 #define TCP_YEAH_ALPHA       80 /* number of packets queued at the bottleneck */
 #define TCP_YEAH_GAMMA        1 /* fraction of queue to be removed per rtt */
 #define TCP_YEAH_DELTA        3 /* log minimum fraction of cwnd to be removed on loss */
 #define TCP_YEAH_EPSILON      1 /* log maximum fraction to be removed on early decongestion */
 #define TCP_YEAH_PHY          8 /* maximum delta from base */
 #define TCP_YEAH_RHO         16 /* minimum number of consecutive rtt to consider competition on loss */
 #define TCP_YEAH_ZETA        50 /* minimum number of state switches to reset reno_count */

 #define TCP_SCALABLE_AI_CNT	 100U

 /* YeAH variables */
 struct yeah {
 	struct vegas vegas;	/* must be first */

 	/* YeAH */
 	u32 lastQ;
 	u32 doing_reno_now;

 	u32 reno_count;
 	u32 fast_count;
 };

 static void tcp_yeah_init(struct sock *sk)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct yeah *yeah = inet_csk_ca(sk);

 	tcp_vegas_init(sk);

 	yeah->doing_reno_now = 0;
 	yeah->lastQ = 0;

 	yeah->reno_count = 2;

 	/* Ensure the MD arithmetic works.  This is somewhat pedantic,
 	 * since I don't think we will see a cwnd this large. :) */
 	tp->snd_cwnd_clamp = min_t(u32, tp->snd_cwnd_clamp, 0xffffffff/128);
 }

 static void tcp_yeah_cong_avoid(struct sock *sk, u32 ack, u32 acked)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct yeah *yeah = inet_csk_ca(sk);

 	if (!tcp_is_cwnd_limited(sk))
 		return;

 	if (tcp_in_slow_start(tp)) {
 		acked = tcp_slow_start(tp, acked);
 		if (!acked)
 			goto do_vegas;
 	}

 	if (!yeah->doing_reno_now) {
 		/* Scalable */
 		tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT),
 				  acked);
 	} else {
 		/* Reno */
 		tcp_cong_avoid_ai(tp, tp->snd_cwnd, acked);
 	}

 	/* The key players are v_vegas.beg_snd_una and v_beg_snd_nxt.
 	 *
 	 * These are so named because they represent the approximate values
 	 * of snd_una and snd_nxt at the beginning of the current RTT. More
 	 * precisely, they represent the amount of data sent during the RTT.
 	 * At the end of the RTT, when we receive an ACK for v_beg_snd_nxt,
 	 * we will calculate that (v_beg_snd_nxt - v_vegas.beg_snd_una) outstanding
 	 * bytes of data have been ACKed during the course of the RTT, giving
 	 * an "actual" rate of:
 	 *
 	 *     (v_beg_snd_nxt - v_vegas.beg_snd_una) / (rtt duration)
 	 *
 	 * Unfortunately, v_vegas.beg_snd_una is not exactly equal to snd_una,
 	 * because delayed ACKs can cover more than one segment, so they
 	 * don't line up yeahly with the boundaries of RTTs.
 	 *
 	 * Another unfortunate fact of life is that delayed ACKs delay the
 	 * advance of the left edge of our send window, so that the number
 	 * of bytes we send in an RTT is often less than our cwnd will allow.
 	 * So we keep track of our cwnd separately, in v_beg_snd_cwnd.
 	 */
 do_vegas:
 	if (after(ack, yeah->vegas.beg_snd_nxt)) {
 		/* We do the Vegas calculations only if we got enough RTT
 		 * samples that we can be reasonably sure that we got
 		 * at least one RTT sample that wasn't from a delayed ACK.
 		 * If we only had 2 samples total,
 		 * then that means we're getting only 1 ACK per RTT, which
 		 * means they're almost certainly delayed ACKs.
 		 * If  we have 3 samples, we should be OK.
 		 */

 		if (yeah->vegas.cntRTT > 2) {
 			u32 rtt, queue;
 			u64 bw;

 			/* We have enough RTT samples, so, using the Vegas
 			 * algorithm, we determine if we should increase or
 			 * decrease cwnd, and by how much.
 			 */

 			/* Pluck out the RTT we are using for the Vegas
 			 * calculations. This is the min RTT seen during the
 			 * last RTT. Taking the min filters out the effects
 			 * of delayed ACKs, at the cost of noticing congestion
 			 * a bit later.
 			 */
 			rtt = yeah->vegas.minRTT;

 			/* Compute excess number of packets above bandwidth
 			 * Avoid doing full 64 bit divide.
 			 */
 			bw = tp->snd_cwnd;
 			bw *= rtt - yeah->vegas.baseRTT;
 			do_div(bw, rtt);
 			queue = bw;

 			if (queue > TCP_YEAH_ALPHA ||
 			    rtt - yeah->vegas.baseRTT > (yeah->vegas.baseRTT / TCP_YEAH_PHY)) {
 				if (queue > TCP_YEAH_ALPHA &&
 				    tp->snd_cwnd > yeah->reno_count) {
 					u32 reduction = min(queue / TCP_YEAH_GAMMA ,
 							    tp->snd_cwnd >> TCP_YEAH_EPSILON);

 					tp->snd_cwnd -= reduction;

 					tp->snd_cwnd = max(tp->snd_cwnd,
 							   yeah->reno_count);

 					tp->snd_ssthresh = tp->snd_cwnd;
 				}

 				if (yeah->reno_count <= 2)
 					yeah->reno_count = max(tp->snd_cwnd>>1, 2U);
 				else
 					yeah->reno_count++;

 				yeah->doing_reno_now = min(yeah->doing_reno_now + 1,
 							   0xffffffU);
 			} else {
 				yeah->fast_count++;

 				if (yeah->fast_count > TCP_YEAH_ZETA) {
 					yeah->reno_count = 2;
 					yeah->fast_count = 0;
 				}

 				yeah->doing_reno_now = 0;
 			}

 			yeah->lastQ = queue;
 		}

 		/* Save the extent of the current window so we can use this
 		 * at the end of the next RTT.
 		 */
 		yeah->vegas.beg_snd_una  = yeah->vegas.beg_snd_nxt;
 		yeah->vegas.beg_snd_nxt  = tp->snd_nxt;
 		yeah->vegas.beg_snd_cwnd = tp->snd_cwnd;

 		/* Wipe the slate clean for the next RTT. */
 		yeah->vegas.cntRTT = 0;
 		yeah->vegas.minRTT = 0x7fffffff;
 	}
 }

 static u32 tcp_yeah_ssthresh(struct sock *sk)
 {
 	const struct tcp_sock *tp = tcp_sk(sk);
 	struct yeah *yeah = inet_csk_ca(sk);
 	u32 reduction;

 	if (yeah->doing_reno_now < TCP_YEAH_RHO) {
 		reduction = yeah->lastQ;

 		reduction = min(reduction, max(tp->snd_cwnd>>1, 2U));

 		reduction = max(reduction, tp->snd_cwnd >> TCP_YEAH_DELTA);
 	} else
 		reduction = max(tp->snd_cwnd>>1, 2U);

 	yeah->fast_count = 0;
 	yeah->reno_count = max(yeah->reno_count>>1, 2U);

 	return max_t(int, tp->snd_cwnd - reduction, 2);
 }

 static struct tcp_congestion_ops tcp_yeah __read_mostly = {
 	.init		= tcp_yeah_init,
 	.ssthresh	= tcp_yeah_ssthresh,
 	.undo_cwnd      = tcp_reno_undo_cwnd,
 	.cong_avoid	= tcp_yeah_cong_avoid,
 	.set_state	= tcp_vegas_state,
 	.cwnd_event	= tcp_vegas_cwnd_event,
 	.get_info	= tcp_vegas_get_info,
 	.pkts_acked	= tcp_vegas_pkts_acked,

 	.owner		= THIS_MODULE,
 	.name		= "yeah",
 };

 static int __init tcp_yeah_register(void)
 {
 	BUG_ON(sizeof(struct yeah) > ICSK_CA_PRIV_SIZE);
 	tcp_register_congestion_control(&tcp_yeah);
 	return 0;
 }

 static void __exit tcp_yeah_unregister(void)
 {
 	tcp_unregister_congestion_control(&tcp_yeah);
 }

 module_init(tcp_yeah_register);
 module_exit(tcp_yeah_unregister);

 MODULE_AUTHOR("Angelo P. Castellani");
 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("YeAH TCP");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	*
	* YeAH TCP
	*
	* For further details look at:
	* https://web.archive.org/web/20080316215752/http://wil.cs.caltech.edu/pfldnet2007/paper/YeAH_TCP.pdf
	*
	*/
	#include <linux/mm.h>
	#include <linux/module.h>
	#include <linux/skbuff.h>
	#include <linux/inet_diag.h>

	#include <net/tcp.h>

	#include "tcp_vegas.h"

	#define TCP_YEAH_ALPHA 80 /* number of packets queued at the bottleneck */
	#define TCP_YEAH_GAMMA 1 /* fraction of queue to be removed per rtt */
	#define TCP_YEAH_DELTA 3 /* log minimum fraction of cwnd to be removed on loss */
	#define TCP_YEAH_EPSILON 1 /* log maximum fraction to be removed on early decongestion */
	#define TCP_YEAH_PHY 8 /* maximum delta from base */
	#define TCP_YEAH_RHO 16 /* minimum number of consecutive rtt to consider competition on loss */
	#define TCP_YEAH_ZETA 50 /* minimum number of state switches to reset reno_count */

	#define TCP_SCALABLE_AI_CNT 100U

	/* YeAH variables */
	struct yeah {
	struct vegas vegas; /* must be first */

	/* YeAH */
	u32 lastQ;
	u32 doing_reno_now;

	u32 reno_count;
	u32 fast_count;
	};

	static void tcp_yeah_init(struct sock *sk)
	{
	struct tcp_sock *tp = tcp_sk(sk);
	struct yeah *yeah = inet_csk_ca(sk);

	tcp_vegas_init(sk);

	yeah->doing_reno_now = 0;
	yeah->lastQ = 0;

	yeah->reno_count = 2;

	/* Ensure the MD arithmetic works. This is somewhat pedantic,
	* since I don't think we will see a cwnd this large. :) */
	tp->snd_cwnd_clamp = min_t(u32, tp->snd_cwnd_clamp, 0xffffffff/128);
	}

	static void tcp_yeah_cong_avoid(struct sock *sk, u32 ack, u32 acked)
	{
	struct tcp_sock *tp = tcp_sk(sk);
	struct yeah *yeah = inet_csk_ca(sk);

	if (!tcp_is_cwnd_limited(sk))
	return;

	if (tcp_in_slow_start(tp)) {
	acked = tcp_slow_start(tp, acked);
	if (!acked)
	goto do_vegas;
	}

	if (!yeah->doing_reno_now) {
	/* Scalable */
	tcp_cong_avoid_ai(tp, min(tp->snd_cwnd, TCP_SCALABLE_AI_CNT),
	acked);
	} else {
	/* Reno */
	tcp_cong_avoid_ai(tp, tp->snd_cwnd, acked);
	}

	/* The key players are v_vegas.beg_snd_una and v_beg_snd_nxt.
	*
	* These are so named because they represent the approximate values
	* of snd_una and snd_nxt at the beginning of the current RTT. More
	* precisely, they represent the amount of data sent during the RTT.
	* At the end of the RTT, when we receive an ACK for v_beg_snd_nxt,
	* we will calculate that (v_beg_snd_nxt - v_vegas.beg_snd_una) outstanding
	* bytes of data have been ACKed during the course of the RTT, giving
	* an "actual" rate of:
	*
	* (v_beg_snd_nxt - v_vegas.beg_snd_una) / (rtt duration)
	*
	* Unfortunately, v_vegas.beg_snd_una is not exactly equal to snd_una,
	* because delayed ACKs can cover more than one segment, so they
	* don't line up yeahly with the boundaries of RTTs.
	*
	* Another unfortunate fact of life is that delayed ACKs delay the
	* advance of the left edge of our send window, so that the number
	* of bytes we send in an RTT is often less than our cwnd will allow.
	* So we keep track of our cwnd separately, in v_beg_snd_cwnd.
	*/
	do_vegas:
	if (after(ack, yeah->vegas.beg_snd_nxt)) {
	/* We do the Vegas calculations only if we got enough RTT
	* samples that we can be reasonably sure that we got
	* at least one RTT sample that wasn't from a delayed ACK.
	* If we only had 2 samples total,
	* then that means we're getting only 1 ACK per RTT, which
	* means they're almost certainly delayed ACKs.
	* If we have 3 samples, we should be OK.
	*/

	if (yeah->vegas.cntRTT > 2) {
	u32 rtt, queue;
	u64 bw;

	/* We have enough RTT samples, so, using the Vegas
	* algorithm, we determine if we should increase or
	* decrease cwnd, and by how much.
	*/

	/* Pluck out the RTT we are using for the Vegas
	* calculations. This is the min RTT seen during the
	* last RTT. Taking the min filters out the effects
	* of delayed ACKs, at the cost of noticing congestion
	* a bit later.
	*/
	rtt = yeah->vegas.minRTT;

	/* Compute excess number of packets above bandwidth
	* Avoid doing full 64 bit divide.
	*/
	bw = tp->snd_cwnd;
	bw *= rtt - yeah->vegas.baseRTT;
	do_div(bw, rtt);
	queue = bw;

	if (queue > TCP_YEAH_ALPHA \|\|
	rtt - yeah->vegas.baseRTT > (yeah->vegas.baseRTT / TCP_YEAH_PHY)) {
	if (queue > TCP_YEAH_ALPHA &&
	tp->snd_cwnd > yeah->reno_count) {
	u32 reduction = min(queue / TCP_YEAH_GAMMA ,
	tp->snd_cwnd >> TCP_YEAH_EPSILON);

	tp->snd_cwnd -= reduction;

	tp->snd_cwnd = max(tp->snd_cwnd,
	yeah->reno_count);

	tp->snd_ssthresh = tp->snd_cwnd;
	}

	if (yeah->reno_count <= 2)
	yeah->reno_count = max(tp->snd_cwnd>>1, 2U);
	else
	yeah->reno_count++;

	yeah->doing_reno_now = min(yeah->doing_reno_now + 1,
	0xffffffU);
	} else {
	yeah->fast_count++;

	if (yeah->fast_count > TCP_YEAH_ZETA) {
	yeah->reno_count = 2;
	yeah->fast_count = 0;
	}

	yeah->doing_reno_now = 0;
	}

	yeah->lastQ = queue;
	}

	/* Save the extent of the current window so we can use this
	* at the end of the next RTT.
	*/
	yeah->vegas.beg_snd_una = yeah->vegas.beg_snd_nxt;
	yeah->vegas.beg_snd_nxt = tp->snd_nxt;
	yeah->vegas.beg_snd_cwnd = tp->snd_cwnd;

	/* Wipe the slate clean for the next RTT. */
	yeah->vegas.cntRTT = 0;
	yeah->vegas.minRTT = 0x7fffffff;
	}
	}

	static u32 tcp_yeah_ssthresh(struct sock *sk)
	{
	const struct tcp_sock *tp = tcp_sk(sk);
	struct yeah *yeah = inet_csk_ca(sk);
	u32 reduction;

	if (yeah->doing_reno_now < TCP_YEAH_RHO) {
	reduction = yeah->lastQ;

	reduction = min(reduction, max(tp->snd_cwnd>>1, 2U));

	reduction = max(reduction, tp->snd_cwnd >> TCP_YEAH_DELTA);
	} else
	reduction = max(tp->snd_cwnd>>1, 2U);

	yeah->fast_count = 0;
	yeah->reno_count = max(yeah->reno_count>>1, 2U);

	return max_t(int, tp->snd_cwnd - reduction, 2);
	}

	static struct tcp_congestion_ops tcp_yeah __read_mostly = {
	.init = tcp_yeah_init,
	.ssthresh = tcp_yeah_ssthresh,
	.undo_cwnd = tcp_reno_undo_cwnd,
	.cong_avoid = tcp_yeah_cong_avoid,
	.set_state = tcp_vegas_state,
	.cwnd_event = tcp_vegas_cwnd_event,
	.get_info = tcp_vegas_get_info,
	.pkts_acked = tcp_vegas_pkts_acked,

	.owner = THIS_MODULE,
	.name = "yeah",
	};

	static int __init tcp_yeah_register(void)
	{
	BUG_ON(sizeof(struct yeah) > ICSK_CA_PRIV_SIZE);
	tcp_register_congestion_control(&tcp_yeah);
	return 0;
	}

	static void __exit tcp_yeah_unregister(void)
	{
	tcp_unregister_congestion_control(&tcp_yeah);
	}

	module_init(tcp_yeah_register);
	module_exit(tcp_yeah_unregister);

	MODULE_AUTHOR("Angelo P. Castellani");
	MODULE_LICENSE("GPL");
	MODULE_DESCRIPTION("YeAH TCP");