1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause
4  * Copyright (c) 2009-2010
6  * Copyright (c) 2010-2011 The FreeBSD Foundation
9  * This software was developed at the Centre for Advanced Internet
14  * Portions of this software were developed at the Centre for Advanced Internet
27  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
36  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
41  * An implementation of the CAIA-Hamilton delay based congestion control
42  * algorithm, based on "Improved coexistence and loss tolerance for delay based
45  * 11-14 October 2010.
84  * Private signal type for rate based congestion signal.
85  * See <netinet/cc.h> for appropriate bit-range to use for private signals.
102 	 * Shadow window - keeps track of what the NewReno congestion window
103 	 * would have been if delay-based cwnd backoffs had not been made. This
104 	 * functionality aids coexistence with loss-based TCP flows which may be
109 	 * Loss-based TCP compatibility flag - When set, it turns on the shadow
150 	uint32_t mss = tcp_fixed_maxseg(ccv->tp);  in chd_window_decrease()
153 	win -= max((win / 2), 1);  in chd_window_decrease()
169 		chd_data->loss_compete = 0;  in should_backoff()
171 		    (V_chd_qthresh - V_chd_qmin)) *  in should_backoff()
172 		    (qdly - V_chd_qmin);  in should_backoff()
176 			    (maxqdly - V_chd_qthresh)) *  in should_backoff()
177 			    (maxqdly - qdly);  in should_backoff()
179 				chd_data->loss_compete = 1;  in should_backoff()
182 			chd_data->loss_compete = 0;  in should_backoff()
194 	uint32_t mss = tcp_fixed_maxseg(ccv->tp);  in chd_window_increase()
196 	chd_data = ccv->cc_data;  in chd_window_increase()
202 			/* In slow-start with ABC enabled. */  in chd_window_increase()
205 				incr = min(ccv->bytes_this_ack,  in chd_window_increase()
209 				incr = min(ccv->bytes_this_ack, mss);  in chd_window_increase()
216 			if (ccv->flags & CCF_ABC_SENTAWND) {  in chd_window_increase()
217 				ccv->flags &= ~CCF_ABC_SENTAWND;  in chd_window_increase()
224 	if (chd_data->shadow_w > 0) {  in chd_window_increase()
226 		chd_data->shadow_w = min(chd_data->shadow_w + incr,  in chd_window_increase()
235  * All ACK signals are used for timing measurements to determine delay-based
247 	chd_data = ccv->cc_data;  in chd_ack_received()
248 	new_measurement = e_t->flags & ERTT_NEW_MEASUREMENT;  in chd_ack_received()
251 	chd_data->maxrtt_in_rtt = imax(e_t->rtt, chd_data->maxrtt_in_rtt);  in chd_ack_received()
256 		 * is delay based congestion.  in chd_ack_received()
258 		rtt = V_chd_use_max ? chd_data->maxrtt_in_rtt : e_t->rtt;  in chd_ack_received()
259 		chd_data->maxrtt_in_rtt = 0;  in chd_ack_received()
261 		if (rtt && e_t->minrtt && !IN_RECOVERY(CCV(ccv, t_flags))) {  in chd_ack_received()
262 			qdly = rtt - e_t->minrtt;  in chd_ack_received()
265 				 * Probabilistic delay based congestion  in chd_ack_received()
269 				    e_t->maxrtt - e_t->minrtt, chd_data);  in chd_ack_received()
271 				chd_data->loss_compete = 0;  in chd_ack_received()
274 		e_t->flags &= ~ERTT_NEW_MEASUREMENT;  in chd_ack_received()
279 		 * Update shadow_w before delay based backoff.  in chd_ack_received()
281 		if (chd_data->loss_compete ||  in chd_ack_received()
282 		    qdly > chd_data->prev_backoff_qdly) {  in chd_ack_received()
286 			 * loss based flows.  in chd_ack_received()
288 			chd_data->shadow_w = max(CCV(ccv, snd_cwnd),  in chd_ack_received()
289 			    chd_data->shadow_w);  in chd_ack_received()
293 			 * not competing with loss based flows at the moment.  in chd_ack_received()
295 			chd_data->shadow_w = 0;  in chd_ack_received()
298 		chd_data->prev_backoff_qdly = qdly;  in chd_ack_received()
300 		 * Send delay-based congestion signal to the congestion signal  in chd_ack_received()
312 	free(ccv->cc_data, M_CC_MEM);  in chd_cb_destroy()
326 	INP_WLOCK_ASSERT(tptoinpcb(ccv->tp));  in chd_cb_init()
334 	chd_data->shadow_w = 0;  in chd_cb_init()
335 	ccv->cc_data = chd_data;  in chd_cb_init()
348 	chd_data = ccv->cc_data;  in chd_cong_signal()
349 	qdly = imax(e_t->rtt, chd_data->maxrtt_in_rtt) - e_t->minrtt;  in chd_cong_signal()
364 		 * than qthresh, assume that we are competing with loss based  in chd_cong_signal()
369 			if (chd_data->loss_compete) {  in chd_cong_signal()
371 				    chd_data->shadow_w);  in chd_cong_signal()
383 		if (chd_data->shadow_w > 0) {  in chd_cong_signal()
384 			uint32_t mss = tcp_fixed_maxseg(ccv->tp);  in chd_cong_signal()
385 			chd_data->shadow_w = max(chd_data->shadow_w /  in chd_cong_signal()
402 	chd_data = ccv->cc_data;  in chd_conn_init()
403 	chd_data->prev_backoff_qdly = 0;  in chd_conn_init()
404 	chd_data->maxrtt_in_rtt = 0;  in chd_conn_init()
405 	chd_data->loss_compete = 0;  in chd_conn_init()
408 	 * competing with loss based flows from the start.  in chd_conn_init()
410 	chd_data->shadow_w = CCV(ccv, snd_cwnd);  in chd_conn_init()
433 	if (error == 0 && req->newptr != NULL) {  in chd_loss_fair_handler()
451 	if (error == 0 && req->newptr != NULL) {  in chd_pmax_handler()
469 	if (error == 0 && req->newptr != NULL) {  in chd_qthresh_handler()
481     "CAIA Hamilton delay-based congestion control related settings");