2 * Copyright (c) 2009-2010
3 * Swinburne University of Technology, Melbourne, Australia
4 * Copyright (c) 2010-2011 The FreeBSD Foundation
7 * This software was developed at the Centre for Advanced Internet
8 * Architectures, Swinburne University of Technology, by David Hayes and
9 * Lawrence Stewart, made possible in part by a grant from the Cisco University
10 * Research Program Fund at Community Foundation Silicon Valley.
12 * Portions of this software were developed at the Centre for Advanced Internet
13 * Architectures, Swinburne University of Technology, Melbourne, Australia by
14 * David Hayes under sponsorship from the FreeBSD Foundation.
16 * Redistribution and use in source and binary forms, with or without
17 * modification, are permitted provided that the following conditions
19 * 1. Redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer.
21 * 2. Redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution.
25 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
28 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
29 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
31 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
32 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
33 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
34 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
39 * An implementation of the CAIA-Hamilton delay based congestion control
40 * algorithm, based on "Improved coexistence and loss tolerance for delay based
41 * TCP congestion control" by D. A. Hayes and G. Armitage., in 35th Annual IEEE
42 * Conference on Local Computer Networks (LCN 2010), Denver, Colorado, USA,
45 * Originally released as part of the NewTCP research project at Swinburne
46 * University of Technology's Centre for Advanced Internet Architectures,
47 * Melbourne, Australia, which was made possible in part by a grant from the
48 * Cisco University Research Program Fund at Community Foundation Silicon
49 * Valley. More details are available at:
50 * http://caia.swin.edu.au/urp/newtcp/
53 #include <sys/cdefs.h>
54 __FBSDID("$FreeBSD$");
56 #include <sys/param.h>
57 #include <sys/kernel.h>
58 #include <sys/khelp.h>
59 #include <sys/limits.h>
60 #include <sys/malloc.h>
61 #include <sys/module.h>
62 #include <sys/queue.h>
63 #include <sys/socket.h>
64 #include <sys/socketvar.h>
65 #include <sys/sysctl.h>
66 #include <sys/systm.h>
71 #include <netinet/cc.h>
72 #include <netinet/tcp_seq.h>
73 #include <netinet/tcp_timer.h>
74 #include <netinet/tcp_var.h>
76 #include <netinet/cc/cc_module.h>
78 #include <netinet/khelp/h_ertt.h>
80 #define CAST_PTR_INT(X) (*((int*)(X)))
83 * Private signal type for rate based congestion signal.
84 * See <netinet/cc.h> for appropriate bit-range to use for private signals.
86 #define CC_CHD_DELAY 0x02000000
88 /* Largest possible number returned by random(). */
89 #define RANDOM_MAX INT_MAX
91 static void chd_ack_received(struct cc_var *ccv, uint16_t ack_type);
92 static void chd_cb_destroy(struct cc_var *ccv);
93 static int chd_cb_init(struct cc_var *ccv);
94 static void chd_cong_signal(struct cc_var *ccv, uint32_t signal_type);
95 static void chd_conn_init(struct cc_var *ccv);
96 static int chd_mod_init(void);
100 * Shadow window - keeps track of what the NewReno congestion window
101 * would have been if delay-based cwnd backoffs had not been made. This
102 * functionality aids coexistence with loss-based TCP flows which may be
103 * sharing links along the path.
105 unsigned long shadow_w;
107 * Loss-based TCP compatibility flag - When set, it turns on the shadow
108 * window functionality.
111 /* The maximum round trip time seen within a measured rtt period. */
113 /* The previous qdly that caused cwnd to backoff. */
114 int prev_backoff_qdly;
119 static VNET_DEFINE(uint32_t, chd_qmin) = 5;
120 static VNET_DEFINE(uint32_t, chd_pmax) = 50;
121 static VNET_DEFINE(uint32_t, chd_loss_fair) = 1;
122 static VNET_DEFINE(uint32_t, chd_use_max) = 1;
123 static VNET_DEFINE(uint32_t, chd_qthresh) = 20;
124 #define V_chd_qthresh VNET(chd_qthresh)
125 #define V_chd_qmin VNET(chd_qmin)
126 #define V_chd_pmax VNET(chd_pmax)
127 #define V_chd_loss_fair VNET(chd_loss_fair)
128 #define V_chd_use_max VNET(chd_use_max)
130 static MALLOC_DEFINE(M_CHD, "chd data",
131 "Per connection data required for the CHD congestion control algorithm");
133 struct cc_algo chd_cc_algo = {
135 .ack_received = chd_ack_received,
136 .cb_destroy = chd_cb_destroy,
137 .cb_init = chd_cb_init,
138 .cong_signal = chd_cong_signal,
139 .conn_init = chd_conn_init,
140 .mod_init = chd_mod_init
144 chd_window_decrease(struct cc_var *ccv)
148 win = min(CCV(ccv, snd_wnd), CCV(ccv, snd_cwnd)) / CCV(ccv, t_maxseg);
149 win -= max((win / 2), 1);
150 CCV(ccv, snd_ssthresh) = max(win, 2) * CCV(ccv, t_maxseg);
154 * Probabilistic backoff function. Returns 1 if we should backoff or 0
155 * otherwise. The calculation of p is similar to the calculation of p in cc_hd.
158 should_backoff(int qdly, int maxqdly, struct chd *chd_data)
160 unsigned long p, rand;
164 if (qdly < V_chd_qthresh) {
165 chd_data->loss_compete = 0;
166 p = (((RANDOM_MAX / 100) * V_chd_pmax) /
167 (V_chd_qthresh - V_chd_qmin)) *
170 if (qdly > V_chd_qthresh) {
171 p = (((RANDOM_MAX / 100) * V_chd_pmax) /
172 (maxqdly - V_chd_qthresh)) *
174 if (V_chd_loss_fair && rand < p)
175 chd_data->loss_compete = 1;
177 p = (RANDOM_MAX / 100) * V_chd_pmax;
178 chd_data->loss_compete = 0;
186 chd_window_increase(struct cc_var *ccv, int new_measurement)
188 struct chd *chd_data;
191 chd_data = ccv->cc_data;
194 if (CCV(ccv, snd_cwnd) <= CCV(ccv, snd_ssthresh)) {
195 /* Adapted from NewReno slow start. */
196 if (V_tcp_do_rfc3465) {
197 /* In slow-start with ABC enabled. */
198 if (CCV(ccv, snd_nxt) == CCV(ccv, snd_max)) {
199 /* Not due to RTO. */
200 incr = min(ccv->bytes_this_ack,
201 V_tcp_abc_l_var * CCV(ccv, t_maxseg));
204 incr = min(ccv->bytes_this_ack,
208 incr = CCV(ccv, t_maxseg);
210 } else { /* Congestion avoidance. */
211 if (V_tcp_do_rfc3465) {
212 if (ccv->flags & CCF_ABC_SENTAWND) {
213 ccv->flags &= ~CCF_ABC_SENTAWND;
214 incr = CCV(ccv, t_maxseg);
216 } else if (new_measurement)
217 incr = CCV(ccv, t_maxseg);
220 if (chd_data->shadow_w > 0) {
221 /* Track NewReno window. */
222 chd_data->shadow_w = min(chd_data->shadow_w + incr,
223 TCP_MAXWIN << CCV(ccv, snd_scale));
226 CCV(ccv,snd_cwnd) = min(CCV(ccv, snd_cwnd) + incr,
227 TCP_MAXWIN << CCV(ccv, snd_scale));
231 * All ACK signals are used for timing measurements to determine delay-based
232 * congestion. However, window increases are only performed when
233 * ack_type == CC_ACK.
236 chd_ack_received(struct cc_var *ccv, uint16_t ack_type)
238 struct chd *chd_data;
240 int backoff, new_measurement, qdly, rtt;
242 e_t = khelp_get_osd(CCV(ccv, osd), ertt_id);
243 chd_data = ccv->cc_data;
244 new_measurement = e_t->flags & ERTT_NEW_MEASUREMENT;
247 chd_data->maxrtt_in_rtt = imax(e_t->rtt, chd_data->maxrtt_in_rtt);
249 if (new_measurement) {
251 * There is a new per RTT measurement, so check to see if there
252 * is delay based congestion.
254 rtt = V_chd_use_max ? chd_data->maxrtt_in_rtt : e_t->rtt;
255 chd_data->maxrtt_in_rtt = 0;
257 if (rtt && e_t->minrtt && !IN_RECOVERY(CCV(ccv, t_flags))) {
258 qdly = rtt - e_t->minrtt;
259 if (qdly > V_chd_qmin) {
261 * Probabilistic delay based congestion
264 backoff = should_backoff(qdly,
265 e_t->maxrtt - e_t->minrtt, chd_data);
267 chd_data->loss_compete = 0;
269 /* Reset per RTT measurement flag to start a new measurement. */
270 e_t->flags &= ~ERTT_NEW_MEASUREMENT;
275 * Update shadow_w before delay based backoff.
277 if (chd_data->loss_compete ||
278 qdly > chd_data->prev_backoff_qdly) {
280 * Delay is higher than when we backed off previously,
281 * so it is possible that this flow is competing with
284 chd_data->shadow_w = max(CCV(ccv, snd_cwnd),
288 * Reset shadow_w, as it is probable that this flow is
289 * not competing with loss based flows at the moment.
291 chd_data->shadow_w = 0;
294 chd_data->prev_backoff_qdly = qdly;
296 * Send delay-based congestion signal to the congestion signal
299 chd_cong_signal(ccv, CC_CHD_DELAY);
301 } else if (ack_type == CC_ACK)
302 chd_window_increase(ccv, new_measurement);
306 chd_cb_destroy(struct cc_var *ccv)
309 if (ccv->cc_data != NULL)
310 free(ccv->cc_data, M_CHD);
314 chd_cb_init(struct cc_var *ccv)
316 struct chd *chd_data;
318 chd_data = malloc(sizeof(struct chd), M_CHD, M_NOWAIT);
319 if (chd_data == NULL)
322 chd_data->shadow_w = 0;
323 ccv->cc_data = chd_data;
329 chd_cong_signal(struct cc_var *ccv, uint32_t signal_type)
332 struct chd *chd_data;
335 e_t = khelp_get_osd(CCV(ccv, osd), ertt_id);
336 chd_data = ccv->cc_data;
337 qdly = imax(e_t->rtt, chd_data->maxrtt_in_rtt) - e_t->minrtt;
339 switch(signal_type) {
341 chd_window_decrease(ccv); /* Set new ssthresh. */
342 CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh);
343 CCV(ccv, snd_recover) = CCV(ccv, snd_max);
344 ENTER_CONGRECOVERY(CCV(ccv, t_flags));
347 case CC_NDUPACK: /* Packet loss. */
349 * Only react to loss as a congestion signal if qdly >
350 * V_chd_qthresh. If qdly is less than qthresh, presume that
351 * this is a non congestion related loss. If qdly is greater
352 * than qthresh, assume that we are competing with loss based
353 * tcp flows and restore window from any unnecessary backoffs,
354 * before the decrease.
356 if (!IN_RECOVERY(CCV(ccv, t_flags)) && qdly > V_chd_qthresh) {
357 if (chd_data->loss_compete) {
358 CCV(ccv, snd_cwnd) = max(CCV(ccv, snd_cwnd),
361 chd_window_decrease(ccv);
364 * This loss isn't congestion related, or already
365 * recovering from congestion.
367 CCV(ccv, snd_ssthresh) = CCV(ccv, snd_cwnd);
368 CCV(ccv, snd_recover) = CCV(ccv, snd_max);
371 if (chd_data->shadow_w > 0) {
372 chd_data->shadow_w = max(chd_data->shadow_w /
373 CCV(ccv, t_maxseg) / 2, 2) * CCV(ccv, t_maxseg);
375 ENTER_FASTRECOVERY(CCV(ccv, t_flags));
379 newreno_cc_algo.cong_signal(ccv, signal_type);
384 chd_conn_init(struct cc_var *ccv)
386 struct chd *chd_data;
388 chd_data = ccv->cc_data;
389 chd_data->prev_backoff_qdly = 0;
390 chd_data->maxrtt_in_rtt = 0;
391 chd_data->loss_compete = 0;
393 * Initialise the shadow_cwnd to be equal to snd_cwnd in case we are
394 * competing with loss based flows from the start.
396 chd_data->shadow_w = CCV(ccv, snd_cwnd);
403 ertt_id = khelp_get_id("ertt");
405 printf("%s: h_ertt module not found\n", __func__);
409 chd_cc_algo.after_idle = newreno_cc_algo.after_idle;
410 chd_cc_algo.post_recovery = newreno_cc_algo.post_recovery;
416 chd_loss_fair_handler(SYSCTL_HANDLER_ARGS)
421 new = V_chd_loss_fair;
422 error = sysctl_handle_int(oidp, &new, 0, req);
423 if (error == 0 && req->newptr != NULL) {
424 if (CAST_PTR_INT(req->newptr) > 1)
427 V_chd_loss_fair = new;
434 chd_pmax_handler(SYSCTL_HANDLER_ARGS)
440 error = sysctl_handle_int(oidp, &new, 0, req);
441 if (error == 0 && req->newptr != NULL) {
442 if (CAST_PTR_INT(req->newptr) == 0 ||
443 CAST_PTR_INT(req->newptr) > 100)
453 chd_qthresh_handler(SYSCTL_HANDLER_ARGS)
459 error = sysctl_handle_int(oidp, &new, 0, req);
460 if (error == 0 && req->newptr != NULL) {
461 if (CAST_PTR_INT(req->newptr) <= V_chd_qmin)
470 SYSCTL_DECL(_net_inet_tcp_cc_chd);
471 SYSCTL_NODE(_net_inet_tcp_cc, OID_AUTO, chd, CTLFLAG_RW, NULL,
472 "CAIA Hamilton delay-based congestion control related settings");
474 SYSCTL_VNET_PROC(_net_inet_tcp_cc_chd, OID_AUTO, loss_fair,
475 CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(chd_loss_fair), 1, &chd_loss_fair_handler,
476 "IU", "Flag to enable shadow window functionality.");
478 SYSCTL_VNET_PROC(_net_inet_tcp_cc_chd, OID_AUTO, pmax,
479 CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(chd_pmax), 5, &chd_pmax_handler,
480 "IU", "Per RTT maximum backoff probability as a percentage");
482 SYSCTL_VNET_PROC(_net_inet_tcp_cc_chd, OID_AUTO, queue_threshold,
483 CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(chd_qthresh), 20, &chd_qthresh_handler,
484 "IU", "Queueing congestion threshold in ticks");
486 SYSCTL_VNET_UINT(_net_inet_tcp_cc_chd, OID_AUTO, queue_min,
487 CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(chd_qmin), 5,
488 "Minimum queueing delay threshold in ticks");
490 SYSCTL_VNET_UINT(_net_inet_tcp_cc_chd, OID_AUTO, use_max,
491 CTLTYPE_UINT|CTLFLAG_RW, &VNET_NAME(chd_use_max), 1,
492 "Use the maximum RTT seen within the measurement period (RTT) "
493 "as the basic delay measurement for the algorithm.");
495 DECLARE_CC_MODULE(chd, &chd_cc_algo);
496 MODULE_DEPEND(chd, ertt, 1, 1, 1);