2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
4 * Copyright (c) 2009-2010
5 * Swinburne University of Technology, Melbourne, Australia
6 * Copyright (c) 2010 Lawrence Stewart <lstewart@freebsd.org>
7 * Copyright (c) 2010-2011 The FreeBSD Foundation
10 * This software was developed at the Centre for Advanced Internet
11 * Architectures, Swinburne University of Technology, by David Hayes and
12 * Lawrence Stewart, made possible in part by a grant from the Cisco University
13 * Research Program Fund at Community Foundation Silicon Valley.
15 * Portions of this software were developed at the Centre for Advanced Internet
16 * Architectures, Swinburne University of Technology, Melbourne, Australia by
17 * David Hayes under sponsorship from the FreeBSD Foundation.
19 * Redistribution and use in source and binary forms, with or without
20 * modification, are permitted provided that the following conditions
22 * 1. Redistributions of source code must retain the above copyright
23 * notice, this list of conditions and the following disclaimer.
24 * 2. Redistributions in binary form must reproduce the above copyright
25 * notice, this list of conditions and the following disclaimer in the
26 * documentation and/or other materials provided with the distribution.
28 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
42 * An implementation of the Vegas congestion control algorithm for FreeBSD,
43 * based on L. S. Brakmo and L. L. Peterson, "TCP Vegas: end to end congestion
44 * avoidance on a global internet", IEEE J. Sel. Areas Commun., vol. 13, no. 8,
45 * pp. 1465-1480, Oct. 1995. The original Vegas duplicate ack policy has not
46 * been implemented, since clock ticks are not as coarse as they were (i.e.
47 * 500ms) when Vegas was designed. Also, packets are timed once per RTT as in
50 * Originally released as part of the NewTCP research project at Swinburne
51 * University of Technology's Centre for Advanced Internet Architectures,
52 * Melbourne, Australia, which was made possible in part by a grant from the
53 * Cisco University Research Program Fund at Community Foundation Silicon
54 * Valley. More details are available at:
55 * http://caia.swin.edu.au/urp/newtcp/
58 #include <sys/cdefs.h>
59 __FBSDID("$FreeBSD$");
61 #include <sys/param.h>
62 #include <sys/kernel.h>
63 #include <sys/khelp.h>
64 #include <sys/malloc.h>
65 #include <sys/module.h>
66 #include <sys/queue.h>
67 #include <sys/socket.h>
68 #include <sys/socketvar.h>
69 #include <sys/sysctl.h>
70 #include <sys/systm.h>
74 #include <netinet/tcp.h>
75 #include <netinet/tcp_timer.h>
76 #include <netinet/tcp_var.h>
77 #include <netinet/cc/cc.h>
78 #include <netinet/cc/cc_module.h>
80 #include <netinet/khelp/h_ertt.h>
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_VEGAS_RATE 0x01000000
88 static void vegas_ack_received(struct cc_var *ccv, uint16_t ack_type);
89 static void vegas_cb_destroy(struct cc_var *ccv);
90 static int vegas_cb_init(struct cc_var *ccv);
91 static void vegas_cong_signal(struct cc_var *ccv, uint32_t signal_type);
92 static void vegas_conn_init(struct cc_var *ccv);
93 static int vegas_mod_init(void);
96 int slow_start_toggle;
99 static int32_t ertt_id;
101 VNET_DEFINE_STATIC(uint32_t, vegas_alpha) = 1;
102 VNET_DEFINE_STATIC(uint32_t, vegas_beta) = 3;
103 #define V_vegas_alpha VNET(vegas_alpha)
104 #define V_vegas_beta VNET(vegas_beta)
106 static MALLOC_DEFINE(M_VEGAS, "vegas data",
107 "Per connection data required for the Vegas congestion control algorithm");
109 struct cc_algo vegas_cc_algo = {
111 .ack_received = vegas_ack_received,
112 .cb_destroy = vegas_cb_destroy,
113 .cb_init = vegas_cb_init,
114 .cong_signal = vegas_cong_signal,
115 .conn_init = vegas_conn_init,
116 .mod_init = vegas_mod_init
120 * The vegas window adjustment is done once every RTT, as indicated by the
121 * ERTT_NEW_MEASUREMENT flag. This flag is reset once the new measurment data
125 vegas_ack_received(struct cc_var *ccv, uint16_t ack_type)
128 struct vegas *vegas_data;
129 long actual_tx_rate, expected_tx_rate, ndiff;
131 e_t = khelp_get_osd(CCV(ccv, osd), ertt_id);
132 vegas_data = ccv->cc_data;
134 if (e_t->flags & ERTT_NEW_MEASUREMENT) { /* Once per RTT. */
135 if (e_t->minrtt && e_t->markedpkt_rtt) {
136 expected_tx_rate = e_t->marked_snd_cwnd / e_t->minrtt;
137 actual_tx_rate = e_t->bytes_tx_in_marked_rtt /
139 ndiff = (expected_tx_rate - actual_tx_rate) *
140 e_t->minrtt / CCV(ccv, t_maxseg);
142 if (ndiff < V_vegas_alpha) {
143 if (CCV(ccv, snd_cwnd) <=
144 CCV(ccv, snd_ssthresh)) {
145 vegas_data->slow_start_toggle =
146 vegas_data->slow_start_toggle ?
149 vegas_data->slow_start_toggle = 0;
151 min(CCV(ccv, snd_cwnd) +
153 TCP_MAXWIN << CCV(ccv, snd_scale));
155 } else if (ndiff > V_vegas_beta) {
156 /* Rate-based congestion. */
157 vegas_cong_signal(ccv, CC_VEGAS_RATE);
158 vegas_data->slow_start_toggle = 0;
161 e_t->flags &= ~ERTT_NEW_MEASUREMENT;
164 if (vegas_data->slow_start_toggle)
165 newreno_cc_algo.ack_received(ccv, ack_type);
169 vegas_cb_destroy(struct cc_var *ccv)
171 free(ccv->cc_data, M_VEGAS);
175 vegas_cb_init(struct cc_var *ccv)
177 struct vegas *vegas_data;
179 vegas_data = malloc(sizeof(struct vegas), M_VEGAS, M_NOWAIT);
181 if (vegas_data == NULL)
184 vegas_data->slow_start_toggle = 1;
185 ccv->cc_data = vegas_data;
191 * If congestion has been triggered triggered by the Vegas measured rates, it is
192 * handled here, otherwise it falls back to newreno's congestion handling.
195 vegas_cong_signal(struct cc_var *ccv, uint32_t signal_type)
197 struct vegas *vegas_data;
200 vegas_data = ccv->cc_data;
202 if (IN_RECOVERY(CCV(ccv, t_flags)))
207 switch(signal_type) {
209 if (!IN_RECOVERY(CCV(ccv, t_flags))) {
210 CCV(ccv, snd_cwnd) = max(2 * CCV(ccv, t_maxseg),
211 CCV(ccv, snd_cwnd) - CCV(ccv, t_maxseg));
212 if (CCV(ccv, snd_cwnd) < CCV(ccv, snd_ssthresh))
213 /* Exit slow start. */
214 CCV(ccv, snd_ssthresh) = CCV(ccv, snd_cwnd);
219 newreno_cc_algo.cong_signal(ccv, signal_type);
222 if (IN_RECOVERY(CCV(ccv, t_flags)) && !presignalrecov)
223 vegas_data->slow_start_toggle =
224 (CCV(ccv, snd_cwnd) < CCV(ccv, snd_ssthresh)) ? 1 : 0;
228 vegas_conn_init(struct cc_var *ccv)
230 struct vegas *vegas_data;
232 vegas_data = ccv->cc_data;
233 vegas_data->slow_start_toggle = 1;
240 ertt_id = khelp_get_id("ertt");
242 printf("%s: h_ertt module not found\n", __func__);
246 vegas_cc_algo.after_idle = newreno_cc_algo.after_idle;
247 vegas_cc_algo.post_recovery = newreno_cc_algo.post_recovery;
253 vegas_alpha_handler(SYSCTL_HANDLER_ARGS)
259 error = sysctl_handle_int(oidp, &new, 0, req);
260 if (error == 0 && req->newptr != NULL) {
261 if (new == 0 || new > V_vegas_beta)
271 vegas_beta_handler(SYSCTL_HANDLER_ARGS)
277 error = sysctl_handle_int(oidp, &new, 0, req);
278 if (error == 0 && req->newptr != NULL) {
279 if (new == 0 || new < V_vegas_alpha)
288 SYSCTL_DECL(_net_inet_tcp_cc_vegas);
289 SYSCTL_NODE(_net_inet_tcp_cc, OID_AUTO, vegas, CTLFLAG_RW, NULL,
290 "Vegas related settings");
292 SYSCTL_PROC(_net_inet_tcp_cc_vegas, OID_AUTO, alpha,
293 CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW,
294 &VNET_NAME(vegas_alpha), 1, &vegas_alpha_handler, "IU",
295 "vegas alpha, specified as number of \"buffers\" (0 < alpha < beta)");
297 SYSCTL_PROC(_net_inet_tcp_cc_vegas, OID_AUTO, beta,
298 CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW,
299 &VNET_NAME(vegas_beta), 3, &vegas_beta_handler, "IU",
300 "vegas beta, specified as number of \"buffers\" (0 < alpha < beta)");
302 DECLARE_CC_MODULE(vegas, &vegas_cc_algo);
303 MODULE_DEPEND(vegas, ertt, 1, 1, 1);