1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
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
8 * All rights reserved.
9 *
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.
14 *
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.
18 *
19 * Redistribution and use in source and binary forms, with or without
20 * modification, are permitted provided that the following conditions
21 * are met:
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.
27 *
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
38 * SUCH DAMAGE.
39 */
40
41 /*
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
48 * the original paper.
49 *
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/
56 */
57
58 #include <sys/param.h>
59 #include <sys/kernel.h>
60 #include <sys/khelp.h>
61 #include <sys/malloc.h>
62 #include <sys/module.h>
63 #include <sys/queue.h>
64 #include <sys/socket.h>
65 #include <sys/socketvar.h>
66 #include <sys/sysctl.h>
67 #include <sys/systm.h>
68
69 #include <net/vnet.h>
70
71 #include <net/route.h>
72 #include <net/route/nhop.h>
73
74 #include <netinet/in_pcb.h>
75 #include <netinet/tcp.h>
76 #include <netinet/tcp_timer.h>
77 #include <netinet/tcp_var.h>
78 #include <netinet/cc/cc.h>
79 #include <netinet/cc/cc_module.h>
80
81 #include <netinet/khelp/h_ertt.h>
82
83 /*
84 * Private signal type for rate based congestion signal.
85 * See <netinet/cc.h> for appropriate bit-range to use for private signals.
86 */
87 #define CC_VEGAS_RATE 0x04000000
88
89 static void vegas_ack_received(struct cc_var *ccv, ccsignal_t ack_type);
90 static void vegas_cb_destroy(struct cc_var *ccv);
91 static int vegas_cb_init(struct cc_var *ccv, void *ptr);
92 static void vegas_cong_signal(struct cc_var *ccv, ccsignal_t signal_type);
93 static void vegas_conn_init(struct cc_var *ccv);
94 static int vegas_mod_init(void);
95 static size_t vegas_data_sz(void);
96
97 struct vegas {
98 int slow_start_toggle;
99 };
100
101 static int32_t ertt_id;
102
103 VNET_DEFINE_STATIC(uint32_t, vegas_alpha) = 1;
104 VNET_DEFINE_STATIC(uint32_t, vegas_beta) = 3;
105 #define V_vegas_alpha VNET(vegas_alpha)
106 #define V_vegas_beta VNET(vegas_beta)
107
108 struct cc_algo vegas_cc_algo = {
109 .name = "vegas",
110 .ack_received = vegas_ack_received,
111 .cb_destroy = vegas_cb_destroy,
112 .cb_init = vegas_cb_init,
113 .cong_signal = vegas_cong_signal,
114 .conn_init = vegas_conn_init,
115 .mod_init = vegas_mod_init,
116 .cc_data_sz = vegas_data_sz,
117 .after_idle = newreno_cc_after_idle,
118 .post_recovery = newreno_cc_post_recovery,
119 };
120
121 /*
122 * The vegas window adjustment is done once every RTT, as indicated by the
123 * ERTT_NEW_MEASUREMENT flag. This flag is reset once the new measurement data
124 * has been used.
125 */
126 static void
vegas_ack_received(struct cc_var * ccv,ccsignal_t ack_type)127 vegas_ack_received(struct cc_var *ccv, ccsignal_t ack_type)
128 {
129 struct ertt *e_t;
130 struct vegas *vegas_data;
131 long actual_tx_rate, expected_tx_rate, ndiff;
132 uint32_t mss = tcp_fixed_maxseg(ccv->tp);
133
134 e_t = khelp_get_osd(&CCV(ccv, t_osd), ertt_id);
135 vegas_data = ccv->cc_data;
136
137 if (e_t->flags & ERTT_NEW_MEASUREMENT) { /* Once per RTT. */
138 if (e_t->minrtt && e_t->markedpkt_rtt) {
139 expected_tx_rate = e_t->marked_snd_cwnd / e_t->minrtt;
140 actual_tx_rate = e_t->bytes_tx_in_marked_rtt /
141 e_t->markedpkt_rtt;
142 ndiff = (expected_tx_rate - actual_tx_rate) *
143 e_t->minrtt / mss;
144
145 if (ndiff < V_vegas_alpha) {
146 if (CCV(ccv, snd_cwnd) <=
147 CCV(ccv, snd_ssthresh)) {
148 vegas_data->slow_start_toggle =
149 vegas_data->slow_start_toggle ?
150 0 : 1;
151 } else {
152 vegas_data->slow_start_toggle = 0;
153 CCV(ccv, snd_cwnd) =
154 min(CCV(ccv, snd_cwnd) + mss,
155 TCP_MAXWIN << CCV(ccv, snd_scale));
156 }
157 } else if (ndiff > V_vegas_beta) {
158 /* Rate-based congestion. */
159 vegas_cong_signal(ccv, CC_VEGAS_RATE);
160 vegas_data->slow_start_toggle = 0;
161 }
162 }
163 e_t->flags &= ~ERTT_NEW_MEASUREMENT;
164 }
165
166 if (vegas_data->slow_start_toggle)
167 newreno_cc_ack_received(ccv, ack_type);
168 }
169
170 static void
vegas_cb_destroy(struct cc_var * ccv)171 vegas_cb_destroy(struct cc_var *ccv)
172 {
173 free(ccv->cc_data, M_CC_MEM);
174 }
175
176 static size_t
vegas_data_sz(void)177 vegas_data_sz(void)
178 {
179 return (sizeof(struct vegas));
180 }
181
182 static int
vegas_cb_init(struct cc_var * ccv,void * ptr)183 vegas_cb_init(struct cc_var *ccv, void *ptr)
184 {
185 struct vegas *vegas_data;
186
187 INP_WLOCK_ASSERT(tptoinpcb(ccv->tp));
188 if (ptr == NULL) {
189 vegas_data = malloc(sizeof(struct vegas), M_CC_MEM, M_NOWAIT);
190 if (vegas_data == NULL)
191 return (ENOMEM);
192 } else
193 vegas_data = ptr;
194
195 vegas_data->slow_start_toggle = 1;
196 ccv->cc_data = vegas_data;
197
198 return (0);
199 }
200
201 /*
202 * If congestion has been triggered triggered by the Vegas measured rates, it is
203 * handled here, otherwise it falls back to newreno's congestion handling.
204 */
205 static void
vegas_cong_signal(struct cc_var * ccv,ccsignal_t signal_type)206 vegas_cong_signal(struct cc_var *ccv, ccsignal_t signal_type)
207 {
208 struct vegas *vegas_data;
209 int presignalrecov;
210 uint32_t mss = tcp_fixed_maxseg(ccv->tp);
211
212 vegas_data = ccv->cc_data;
213
214 if (IN_RECOVERY(CCV(ccv, t_flags)))
215 presignalrecov = 1;
216 else
217 presignalrecov = 0;
218
219 switch((int)signal_type) {
220 case CC_VEGAS_RATE:
221 if (!IN_RECOVERY(CCV(ccv, t_flags))) {
222 CCV(ccv, snd_cwnd) = max(2 * mss,
223 CCV(ccv, snd_cwnd) - mss);
224 if (CCV(ccv, snd_cwnd) < CCV(ccv, snd_ssthresh))
225 /* Exit slow start. */
226 CCV(ccv, snd_ssthresh) = CCV(ccv, snd_cwnd);
227 }
228 break;
229
230 default:
231 newreno_cc_cong_signal(ccv, signal_type);
232 break;
233 }
234
235 if (IN_RECOVERY(CCV(ccv, t_flags)) && !presignalrecov)
236 vegas_data->slow_start_toggle =
237 (CCV(ccv, snd_cwnd) < CCV(ccv, snd_ssthresh)) ? 1 : 0;
238 }
239
240 static void
vegas_conn_init(struct cc_var * ccv)241 vegas_conn_init(struct cc_var *ccv)
242 {
243 struct vegas *vegas_data;
244
245 vegas_data = ccv->cc_data;
246 vegas_data->slow_start_toggle = 1;
247 }
248
249 static int
vegas_mod_init(void)250 vegas_mod_init(void)
251 {
252 ertt_id = khelp_get_id("ertt");
253 if (ertt_id <= 0) {
254 printf("%s: h_ertt module not found\n", __func__);
255 return (ENOENT);
256 }
257 return (0);
258 }
259
260 static int
vegas_alpha_handler(SYSCTL_HANDLER_ARGS)261 vegas_alpha_handler(SYSCTL_HANDLER_ARGS)
262 {
263 int error;
264 uint32_t new;
265
266 new = V_vegas_alpha;
267 error = sysctl_handle_int(oidp, &new, 0, req);
268 if (error == 0 && req->newptr != NULL) {
269 if (new == 0 || new > V_vegas_beta)
270 error = EINVAL;
271 else
272 V_vegas_alpha = new;
273 }
274
275 return (error);
276 }
277
278 static int
vegas_beta_handler(SYSCTL_HANDLER_ARGS)279 vegas_beta_handler(SYSCTL_HANDLER_ARGS)
280 {
281 int error;
282 uint32_t new;
283
284 new = V_vegas_beta;
285 error = sysctl_handle_int(oidp, &new, 0, req);
286 if (error == 0 && req->newptr != NULL) {
287 if (new == 0 || new < V_vegas_alpha)
288 error = EINVAL;
289 else
290 V_vegas_beta = new;
291 }
292
293 return (error);
294 }
295
296 SYSCTL_DECL(_net_inet_tcp_cc_vegas);
297 SYSCTL_NODE(_net_inet_tcp_cc, OID_AUTO, vegas,
298 CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
299 "Vegas related settings");
300
301 SYSCTL_PROC(_net_inet_tcp_cc_vegas, OID_AUTO, alpha,
302 CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
303 &VNET_NAME(vegas_alpha), 1, &vegas_alpha_handler, "IU",
304 "vegas alpha, specified as number of \"buffers\" (0 < alpha < beta)");
305
306 SYSCTL_PROC(_net_inet_tcp_cc_vegas, OID_AUTO, beta,
307 CTLFLAG_VNET | CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
308 &VNET_NAME(vegas_beta), 3, &vegas_beta_handler, "IU",
309 "vegas beta, specified as number of \"buffers\" (0 < alpha < beta)");
310
311 DECLARE_CC_MODULE(vegas, &vegas_cc_algo);
312 MODULE_VERSION(vegas, 2);
313 MODULE_DEPEND(vegas, ertt, 1, 1, 1);
314