1 // SPDX-License-Identifier: GPL-2.0
7  * https://tools.ietf.org/html/rfc1122#section-4.2.3.1
8  * http://ccr.sigcomm.org/archive/1995/jan95/ccr-9501-partridge87.pdf
12 #include "ar-internal.h"
18 static u32 rxrpc_rto_min_us(struct rxrpc_peer *peer)  in rxrpc_rto_min_us()
23 static u32 __rxrpc_set_rto(const struct rxrpc_peer *peer)  in __rxrpc_set_rto()
25 	return usecs_to_jiffies((peer->srtt_us >> 3) + peer->rttvar_us);  in __rxrpc_set_rto()
28 static u32 rxrpc_bound_rto(u32 rto)  in rxrpc_bound_rto()
41  * it up into three procedures. -- erics
43 static void rxrpc_rtt_estimator(struct rxrpc_peer *peer, long sample_rtt_us)  in rxrpc_rtt_estimator()
46 	u32 srtt = peer->srtt_us;  in rxrpc_rtt_estimator()
65 		m -= (srtt >> 3);	/* m is now error in rtt est */  in rxrpc_rtt_estimator()
68 			m = -m;		/* m is now abs(error) */  in rxrpc_rtt_estimator()
69 			m -= (peer->mdev_us >> 2);   /* similar update on mdev */  in rxrpc_rtt_estimator()
73 			 * for mdev in this case (alpha*beta).  in rxrpc_rtt_estimator()
81 			m -= (peer->mdev_us >> 2);   /* similar update on mdev */  in rxrpc_rtt_estimator()
84 		peer->mdev_us += m;		/* mdev = 3/4 mdev + 1/4 new */  in rxrpc_rtt_estimator()
85 		if (peer->mdev_us > peer->mdev_max_us) {  in rxrpc_rtt_estimator()
86 			peer->mdev_max_us = peer->mdev_us;  in rxrpc_rtt_estimator()
87 			if (peer->mdev_max_us > peer->rttvar_us)  in rxrpc_rtt_estimator()
88 				peer->rttvar_us = peer->mdev_max_us;  in rxrpc_rtt_estimator()
93 		peer->mdev_us = m << 1;	/* make sure rto = 3*rtt */  in rxrpc_rtt_estimator()
94 		peer->rttvar_us = max(peer->mdev_us, rxrpc_rto_min_us(peer));  in rxrpc_rtt_estimator()
95 		peer->mdev_max_us = peer->rttvar_us;  in rxrpc_rtt_estimator()
98 	peer->srtt_us = max(1U, srtt);  in rxrpc_rtt_estimator()
105 static void rxrpc_set_rto(struct rxrpc_peer *peer)  in rxrpc_set_rto()
113 	 *    is invisible. Actually, Linux-2.4 also generates erratic  in rxrpc_set_rto()
127 	peer->rto_j = rxrpc_bound_rto(rto);  in rxrpc_set_rto()
130 static void rxrpc_ack_update_rtt(struct rxrpc_peer *peer, long rtt_us)  in rxrpc_ack_update_rtt()
140 	peer->backoff = 0;  in rxrpc_ack_update_rtt()
152 	struct rxrpc_peer *peer = call->peer;  in rxrpc_peer_add_rtt()
159 	spin_lock(&peer->rtt_input_lock);  in rxrpc_peer_add_rtt()
161 	if (peer->rtt_count < 3)  in rxrpc_peer_add_rtt()
162 		peer->rtt_count++;  in rxrpc_peer_add_rtt()
163 	spin_unlock(&peer->rtt_input_lock);  in rxrpc_peer_add_rtt()
166 			   peer->srtt_us >> 3, peer->rto_j);  in rxrpc_peer_add_rtt()
176 	u8 backoff = READ_ONCE(peer->backoff);  in rxrpc_get_rto_backoff()
178 	timo_j = peer->rto_j;  in rxrpc_get_rto_backoff()
181 		WRITE_ONCE(peer->backoff, backoff + 1);  in rxrpc_get_rto_backoff()
191 	peer->rto_j	= RXRPC_TIMEOUT_INIT;  in rxrpc_peer_init_rtt()
192 	peer->mdev_us	= jiffies_to_usecs(RXRPC_TIMEOUT_INIT);  in rxrpc_peer_init_rtt()
193 	peer->backoff	= 0;  in rxrpc_peer_init_rtt()
194 	//minmax_reset(&peer->rtt_min, rxrpc_jiffies32, ~0U);  in rxrpc_peer_init_rtt()