1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause
4  * Copyright (c) 2007-2008
6  * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org>
42  * An implementation of the H-TCP congestion control algorithm for FreeBSD,
43  * based on the Internet Draft "draft-leith-tcp-htcp-06.txt" by Leith and
86 /* RTT_ref (ms) used in the calculation of alpha if RTT scaling is enabled. */
96  * i.e. 1 + 10(delta - delta_l) + ((delta - delta_l) / 2) ^ 2
98  * "diff" is passed in to the macro as "delta - delta_l" and is expected to be
115  * up-shifting all the terms in the function and performing the required
116  * calculations, we down-shift the final result by HTCP_ALPHA_INC_SHIFT to
174 /* Per-netstack vars. */
196 	uint32_t mss = tcp_fixed_maxseg(ccv->tp);  in htcp_ack_received()
198 	htcp_data = ccv->cc_data;  in htcp_ack_received()
207 	    (ccv->flags & CCF_CWND_LIMITED) && (!V_tcp_do_rfc3465 ||  in htcp_ack_received()
209 	    (V_tcp_do_rfc3465 && ccv->flags & CCF_ABC_SENTAWND))) {  in htcp_ack_received()
217 		if (htcp_data->alpha == 1 ||  in htcp_ack_received()
223 				CCV(ccv, snd_cwnd) += htcp_data->alpha *  in htcp_ack_received()
225 				ccv->flags &= ~CCF_ABC_SENTAWND;  in htcp_ack_received()
232 				CCV(ccv, snd_cwnd) += (((htcp_data->alpha <<  in htcp_ack_received()
243 	free(ccv->cc_data, M_CC_MEM);  in htcp_cb_destroy()
257 	INP_WLOCK_ASSERT(tptoinpcb(ccv->tp));  in htcp_cb_init()
266 	htcp_data->alpha = HTCP_INIT_ALPHA;  in htcp_cb_init()
267 	htcp_data->beta = HTCP_MINBETA;  in htcp_cb_init()
268 	htcp_data->maxrtt = TCPTV_SRTTBASE;  in htcp_cb_init()
269 	htcp_data->minrtt = TCPTV_SRTTBASE;  in htcp_cb_init()
270 	htcp_data->prev_cwnd = 0;  in htcp_cb_init()
271 	htcp_data->t_last_cong = ticks;  in htcp_cb_init()
273 	ccv->cc_data = htcp_data;  in htcp_cb_init()
287 	htcp_data = ccv->cc_data;  in htcp_cong_signal()
288 	mss = tcp_fixed_maxseg(ccv->tp);  in htcp_cong_signal()
299 				htcp_data->maxrtt = (htcp_data->minrtt +  in htcp_cong_signal()
300 				    (htcp_data->maxrtt - htcp_data->minrtt) *  in htcp_cong_signal()
303 				htcp_data->t_last_cong = ticks;  in htcp_cong_signal()
304 				htcp_data->prev_cwnd = CCV(ccv, snd_cwnd);  in htcp_cong_signal()
316 			htcp_data->maxrtt = (htcp_data->minrtt + (htcp_data->maxrtt -  in htcp_cong_signal()
317 			    htcp_data->minrtt) * 95) / 100;  in htcp_cong_signal()
320 			htcp_data->t_last_cong = ticks;  in htcp_cong_signal()
321 			htcp_data->prev_cwnd = CCV(ccv, snd_cwnd);  in htcp_cong_signal()
329 				pipe = tcp_compute_pipe(ccv->tp);  in htcp_cong_signal()
331 				pipe = CCV(ccv, snd_max) -  in htcp_cong_signal()
347 			htcp_data->t_last_cong = ticks;  in htcp_cong_signal()
374 	uint32_t mss = tcp_fixed_maxseg(ccv->tp);  in htcp_post_recovery()
377 	htcp_data = ccv->cc_data;  in htcp_post_recovery()
388 			pipe = tcp_compute_pipe(ccv->tp);  in htcp_post_recovery()
390 			pipe = CCV(ccv, snd_max) - ccv->curack;  in htcp_post_recovery()
394 			 * Ensure that cwnd down not collape to 1 MSS under  in htcp_post_recovery()
399 			CCV(ccv, snd_cwnd) = max(1, ((htcp_data->beta *  in htcp_post_recovery()
400 			    htcp_data->prev_cwnd / mss)  in htcp_post_recovery()
411 	htcp_data = ccv->cc_data;  in htcp_recalc_alpha()
418 	 * losses and restart alpha from scratch by setting t_last_cong = now -  in htcp_recalc_alpha()
425 	if (now < htcp_data->t_last_cong)  in htcp_recalc_alpha()
426 		htcp_data->t_last_cong = now - HTCP_DELTA_L;  in htcp_recalc_alpha()
428 	diff = now - htcp_data->t_last_cong - HTCP_DELTA_L;  in htcp_recalc_alpha()
441 			 * 2 * (1 - beta) * alpha_raw  in htcp_recalc_alpha()
444 				alpha = max(1, (2 * ((1 << HTCP_SHIFT) -  in htcp_recalc_alpha()
445 				    htcp_data->beta) * alpha) >> HTCP_SHIFT);  in htcp_recalc_alpha()
448 			 * RTT scaling: (RTT / RTT_ref) * alpha  in htcp_recalc_alpha()
455 				    (tcp_get_srtt(ccv->tp, TCP_TMR_GRANULARITY_TICKS) << HTCP_SHIFT) /  in htcp_recalc_alpha()
462 		htcp_data->alpha = alpha;  in htcp_recalc_alpha()
471 	htcp_data = ccv->cc_data;  in htcp_recalc_beta()
479 	if (V_htcp_adaptive_backoff && htcp_data->minrtt != TCPTV_SRTTBASE &&  in htcp_recalc_beta()
480 	    htcp_data->maxrtt != TCPTV_SRTTBASE)  in htcp_recalc_beta()
481 		htcp_data->beta = min(max(HTCP_MINBETA,  in htcp_recalc_beta()
482 		    (htcp_data->minrtt << HTCP_SHIFT) / htcp_data->maxrtt),  in htcp_recalc_beta()
485 		htcp_data->beta = HTCP_MINBETA;  in htcp_recalc_beta()
497 	htcp_data = ccv->cc_data;  in htcp_record_rtt()
506 	if ((tcp_get_srtt(ccv->tp, TCP_TMR_GRANULARITY_TICKS) < htcp_data->minrtt ||  in htcp_record_rtt()
507 	    htcp_data->minrtt == TCPTV_SRTTBASE) &&  in htcp_record_rtt()
509 		htcp_data->minrtt = tcp_get_srtt(ccv->tp, TCP_TMR_GRANULARITY_TICKS);  in htcp_record_rtt()
515 	if (tcp_get_srtt(ccv->tp, TCP_TMR_GRANULARITY_TICKS) > htcp_data->maxrtt  in htcp_record_rtt()
517 		htcp_data->maxrtt = tcp_get_srtt(ccv->tp, TCP_TMR_GRANULARITY_TICKS);  in htcp_record_rtt()
528 	htcp_data = ccv->cc_data;  in htcp_ssthresh_update()
540 		    htcp_data->beta) >> HTCP_SHIFT;  in htcp_ssthresh_update()
546     "H-TCP related settings");
549     "enable H-TCP adaptive backoff");
552     "enable H-TCP RTT scaling");