1 // SPDX-License-Identifier: GPL-2.0-only
8  *    IEEE Journal on Selected Areas in Communication, 13(8):1465--1480,
17  *     using fine-grained timers, NewReno, and FACK.
19  *     only every-other RTT during slow start, we increase during
27  *     minimum RTT sample observed during the last RTT to calculate
29  *   o When the sender re-starts from idle, it waits until it has
55 /* There are several situations when we must "re-start" Vegas:
65  * stale info -- both the saved cwnd and congestion feedback are
76 	/* Begin taking Vegas samples next time we send something. */  in vegas_enable()
77 	vegas->doing_vegas_now = 1;  in vegas_enable()
80 	vegas->beg_snd_nxt = tp->snd_nxt;  in vegas_enable()
82 	vegas->cntRTT = 0;  in vegas_enable()
83 	vegas->minRTT = 0x7fffffff;  in vegas_enable()
91 	vegas->doing_vegas_now = 0;  in vegas_disable()
98 	vegas->baseRTT = 0x7fffffff;  in tcp_vegas_init()
105  *   o min-filter RTT samples from within an RTT to get the current
106  *     propagation delay + queuing delay (we are min-filtering to try to
108  *   o min-filter RTT samples from a much longer window (forever for now)
111 void tcp_vegas_pkts_acked(struct sock *sk, const struct ack_sample *sample)  in tcp_vegas_pkts_acked()  argument
116 	if (sample->rtt_us < 0)  in tcp_vegas_pkts_acked()
120 	vrtt = sample->rtt_us + 1;  in tcp_vegas_pkts_acked()
123 	if (vrtt < vegas->baseRTT)  in tcp_vegas_pkts_acked()
124 		vegas->baseRTT = vrtt;  in tcp_vegas_pkts_acked()
126 	/* Find the min RTT during the last RTT to find  in tcp_vegas_pkts_acked()
129 	vegas->minRTT = min(vegas->minRTT, vrtt);  in tcp_vegas_pkts_acked()
130 	vegas->cntRTT++;  in tcp_vegas_pkts_acked()
162 	return  min(tp->snd_ssthresh, tp->snd_cwnd);  in tcp_vegas_ssthresh()
170 	if (!vegas->doing_vegas_now) {  in tcp_vegas_cong_avoid()
175 	if (after(ack, vegas->beg_snd_nxt)) {  in tcp_vegas_cong_avoid()
176 		/* Do the Vegas once-per-RTT cwnd adjustment. */  in tcp_vegas_cong_avoid()
181 		vegas->beg_snd_nxt  = tp->snd_nxt;  in tcp_vegas_cong_avoid()
185 		 * at least one RTT sample that wasn't from a delayed ACK.  in tcp_vegas_cong_avoid()
192 		if (vegas->cntRTT <= 2) {  in tcp_vegas_cong_avoid()
207 			 * calculations. This is the min RTT seen during the  in tcp_vegas_cong_avoid()
208 			 * last RTT. Taking the min filters out the effects  in tcp_vegas_cong_avoid()
212 			rtt = vegas->minRTT;  in tcp_vegas_cong_avoid()
220 			target_cwnd = (u64)tp->snd_cwnd * vegas->baseRTT;  in tcp_vegas_cong_avoid()
227 			diff = tp->snd_cwnd * (rtt-vegas->baseRTT) / vegas->baseRTT;  in tcp_vegas_cong_avoid()
230 				/* Going too fast. Time to slow down  in tcp_vegas_cong_avoid()
241 				tp->snd_cwnd = min(tp->snd_cwnd, (u32)target_cwnd+1);  in tcp_vegas_cong_avoid()
242 				tp->snd_ssthresh = tcp_vegas_ssthresh(tp);  in tcp_vegas_cong_avoid()
257 					tp->snd_cwnd--;  in tcp_vegas_cong_avoid()
258 					tp->snd_ssthresh  in tcp_vegas_cong_avoid()
264 					tp->snd_cwnd++;  in tcp_vegas_cong_avoid()
272 			if (tp->snd_cwnd < 2)  in tcp_vegas_cong_avoid()
273 				tp->snd_cwnd = 2;  in tcp_vegas_cong_avoid()
274 			else if (tp->snd_cwnd > tp->snd_cwnd_clamp)  in tcp_vegas_cong_avoid()
275 				tp->snd_cwnd = tp->snd_cwnd_clamp;  in tcp_vegas_cong_avoid()
277 			tp->snd_ssthresh = tcp_current_ssthresh(sk);  in tcp_vegas_cong_avoid()
281 		vegas->cntRTT = 0;  in tcp_vegas_cong_avoid()
282 		vegas->minRTT = 0x7fffffff;  in tcp_vegas_cong_avoid()
295 	if (ext & (1 << (INET_DIAG_VEGASINFO - 1))) {  in tcp_vegas_get_info()
296 		info->vegas.tcpv_enabled = ca->doing_vegas_now;  in tcp_vegas_get_info()
297 		info->vegas.tcpv_rttcnt = ca->cntRTT;  in tcp_vegas_get_info()
298 		info->vegas.tcpv_rtt = ca->baseRTT;  in tcp_vegas_get_info()
299 		info->vegas.tcpv_minrtt = ca->minRTT;  in tcp_vegas_get_info()