2 * Copyright (c) 2009-2010
3 * Swinburne University of Technology, Melbourne, Australia
4 * Copyright (c) 2010 Lawrence Stewart <lstewart@freebsd.org>
5 * Copyright (c) 2010-2011 The FreeBSD Foundation
8 * This software was developed at the Centre for Advanced Internet
9 * Architectures, Swinburne University of Technology, by David Hayes and
10 * Lawrence Stewart, made possible in part by a grant from the Cisco University
11 * Research Program Fund at Community Foundation Silicon Valley.
13 * Portions of this software were developed at the Centre for Advanced Internet
14 * Architectures, Swinburne University of Technology, Melbourne, Australia by
15 * David Hayes under sponsorship from the FreeBSD Foundation.
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions
20 * 1. Redistributions of source code must retain the above copyright
21 * notice, this list of conditions and the following disclaimer.
22 * 2. Redistributions in binary form must reproduce the above copyright
23 * notice, this list of conditions and the following disclaimer in the
24 * documentation and/or other materials provided with the distribution.
26 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
40 * An implementation of the Vegas congestion control algorithm for FreeBSD,
41 * based on L. S. Brakmo and L. L. Peterson, "TCP Vegas: end to end congestion
42 * avoidance on a global internet", IEEE J. Sel. Areas Commun., vol. 13, no. 8,
43 * pp. 1465-1480, Oct. 1995. The original Vegas duplicate ack policy has not
44 * been implemented, since clock ticks are not as coarse as they were (i.e.
45 * 500ms) when Vegas was designed. Also, packets are timed once per RTT as in
48 * Originally released as part of the NewTCP research project at Swinburne
49 * University of Technology's Centre for Advanced Internet Architectures,
50 * Melbourne, Australia, which was made possible in part by a grant from the
51 * Cisco University Research Program Fund at Community Foundation Silicon
52 * Valley. More details are available at:
53 * http://caia.swin.edu.au/urp/newtcp/
56 #include <sys/cdefs.h>
57 __FBSDID("$FreeBSD$");
59 #include <sys/param.h>
60 #include <sys/kernel.h>
61 #include <sys/khelp.h>
62 #include <sys/malloc.h>
63 #include <sys/module.h>
64 #include <sys/queue.h>
65 #include <sys/socket.h>
66 #include <sys/socketvar.h>
67 #include <sys/sysctl.h>
68 #include <sys/systm.h>
72 #include <netinet/tcp.h>
73 #include <netinet/tcp_timer.h>
74 #include <netinet/tcp_var.h>
75 #include <netinet/cc/cc.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_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 static VNET_DEFINE(uint32_t, vegas_alpha) = 1;
102 static VNET_DEFINE(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)
172 if (ccv->cc_data != NULL)
173 free(ccv->cc_data, M_VEGAS);
177 vegas_cb_init(struct cc_var *ccv)
179 struct vegas *vegas_data;
181 vegas_data = malloc(sizeof(struct vegas), M_VEGAS, M_NOWAIT);
183 if (vegas_data == NULL)
186 vegas_data->slow_start_toggle = 1;
187 ccv->cc_data = vegas_data;
193 * If congestion has been triggered triggered by the Vegas measured rates, it is
194 * handled here, otherwise it falls back to newreno's congestion handling.
197 vegas_cong_signal(struct cc_var *ccv, uint32_t signal_type)
199 struct vegas *vegas_data;
202 vegas_data = ccv->cc_data;
204 if (IN_RECOVERY(CCV(ccv, t_flags)))
209 switch(signal_type) {
211 if (!IN_RECOVERY(CCV(ccv, t_flags))) {
212 CCV(ccv, snd_cwnd) = max(2 * CCV(ccv, t_maxseg),
213 CCV(ccv, snd_cwnd) - CCV(ccv, t_maxseg));
214 if (CCV(ccv, snd_cwnd) < CCV(ccv, snd_ssthresh))
215 /* Exit slow start. */
216 CCV(ccv, snd_ssthresh) = CCV(ccv, snd_cwnd);
221 newreno_cc_algo.cong_signal(ccv, signal_type);
224 if (IN_RECOVERY(CCV(ccv, t_flags)) && !presignalrecov)
225 vegas_data->slow_start_toggle =
226 (CCV(ccv, snd_cwnd) < CCV(ccv, snd_ssthresh)) ? 1 : 0;
230 vegas_conn_init(struct cc_var *ccv)
232 struct vegas *vegas_data;
234 vegas_data = ccv->cc_data;
235 vegas_data->slow_start_toggle = 1;
242 ertt_id = khelp_get_id("ertt");
244 printf("%s: h_ertt module not found\n", __func__);
248 vegas_cc_algo.after_idle = newreno_cc_algo.after_idle;
249 vegas_cc_algo.post_recovery = newreno_cc_algo.post_recovery;
255 vegas_alpha_handler(SYSCTL_HANDLER_ARGS)
261 error = sysctl_handle_int(oidp, &new, 0, req);
262 if (error == 0 && req->newptr != NULL) {
263 if (CAST_PTR_INT(req->newptr) < 1 ||
264 CAST_PTR_INT(req->newptr) > V_vegas_beta)
274 vegas_beta_handler(SYSCTL_HANDLER_ARGS)
280 error = sysctl_handle_int(oidp, &new, 0, req);
281 if (error == 0 && req->newptr != NULL) {
282 if (CAST_PTR_INT(req->newptr) < 1 ||
283 CAST_PTR_INT(req->newptr) < V_vegas_alpha)
292 SYSCTL_DECL(_net_inet_tcp_cc_vegas);
293 SYSCTL_NODE(_net_inet_tcp_cc, OID_AUTO, vegas, CTLFLAG_RW, NULL,
294 "Vegas related settings");
296 SYSCTL_PROC(_net_inet_tcp_cc_vegas, OID_AUTO, alpha,
297 CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW,
298 &VNET_NAME(vegas_alpha), 1, &vegas_alpha_handler, "IU",
299 "vegas alpha, specified as number of \"buffers\" (0 < alpha < beta)");
301 SYSCTL_PROC(_net_inet_tcp_cc_vegas, OID_AUTO, beta,
302 CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW,
303 &VNET_NAME(vegas_beta), 3, &vegas_beta_handler, "IU",
304 "vegas beta, specified as number of \"buffers\" (0 < alpha < beta)");
306 DECLARE_CC_MODULE(vegas, &vegas_cc_algo);
307 MODULE_DEPEND(vegas, ertt, 1, 1, 1);