1 /*
2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
3 * The Regents of the University of California.
4 * Copyright (c) 2007-2008,2010
5 * Swinburne University of Technology, Melbourne, Australia.
6 * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org>
7 * Copyright (c) 2010 The FreeBSD Foundation
8 * All rights reserved.
9 * Copyright (c) 2017 by Delphix. All rights reserved.
10 * Copyright 2020 RackTop Systems, Inc.
11 *
12 * This software was developed at the Centre for Advanced Internet
13 * Architectures, Swinburne University of Technology, by Lawrence Stewart, James
14 * Healy and David Hayes, made possible in part by a grant from the Cisco
15 * University Research Program Fund at Community Foundation Silicon Valley.
16 *
17 * Portions of this software were developed at the Centre for Advanced
18 * Internet Architectures, Swinburne University of Technology, Melbourne,
19 * Australia by David Hayes under sponsorship from the FreeBSD Foundation.
20 *
21 * Redistribution and use in source and binary forms, with or without
22 * modification, are permitted provided that the following conditions
23 * are met:
24 * 1. Redistributions of source code must retain the above copyright
25 * notice, this list of conditions and the following disclaimer.
26 * 2. Redistributions in binary form must reproduce the above copyright
27 * notice, this list of conditions and the following disclaimer in the
28 * documentation and/or other materials provided with the distribution.
29 *
30 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
31 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
32 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
33 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
34 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
35 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
36 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
37 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
38 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
39 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
40 * SUCH DAMAGE.
41 */
42
43 /*
44 * This software was first released in 2007 by James Healy and Lawrence Stewart
45 * whilst working on the NewTCP research project at Swinburne University of
46 * Technology's Centre for Advanced Internet Architectures, Melbourne,
47 * Australia, which was made possible in part by a grant from the Cisco
48 * University Research Program Fund at Community Foundation Silicon Valley.
49 * More details are available at:
50 * http://caia.swin.edu.au/urp/newtcp/
51 */
52
53 #include <sys/errno.h>
54 #include <inet/tcp.h>
55 #include <inet/tcp_impl.h>
56 #include <inet/cc.h>
57 #include <inet/cc/cc_module.h>
58
59 static void newreno_ack_received(struct cc_var *ccv, uint16_t type);
60 static void newreno_after_idle(struct cc_var *ccv);
61 static void newreno_cong_signal(struct cc_var *ccv, uint32_t type);
62 static void newreno_post_recovery(struct cc_var *ccv);
63
64 static struct modlmisc cc_newreno_modlmisc = {
65 &mod_miscops,
66 "New Reno Congestion Control"
67 };
68
69 static struct modlinkage cc_newreno_modlinkage = {
70 MODREV_1,
71 &cc_newreno_modlmisc,
72 NULL
73 };
74
75 struct cc_algo newreno_cc_algo = {
76 .name = "newreno",
77 .ack_received = newreno_ack_received,
78 .after_idle = newreno_after_idle,
79 .cong_signal = newreno_cong_signal,
80 .post_recovery = newreno_post_recovery,
81 };
82
83 int
_init(void)84 _init(void)
85 {
86 int err;
87
88 if ((err = cc_register_algo(&newreno_cc_algo)) == 0) {
89 if ((err = mod_install(&cc_newreno_modlinkage)) != 0)
90 (void) cc_deregister_algo(&newreno_cc_algo);
91 }
92 return (err);
93 }
94
95 int
_fini(void)96 _fini(void)
97 {
98 /* XXX Not unloadable for now */
99 return (EBUSY);
100 }
101
102 int
_info(struct modinfo * modinfop)103 _info(struct modinfo *modinfop)
104 {
105 return (mod_info(&cc_newreno_modlinkage, modinfop));
106 }
107
108 static void
newreno_ack_received(struct cc_var * ccv,uint16_t type)109 newreno_ack_received(struct cc_var *ccv, uint16_t type)
110 {
111 if (type == CC_ACK && !IN_RECOVERY(ccv->flags) &&
112 (ccv->flags & CCF_CWND_LIMITED)) {
113 uint_t cw = CCV(ccv, tcp_cwnd);
114 uint_t incr = CCV(ccv, tcp_mss);
115
116 /*
117 * Regular in-order ACK, open the congestion window.
118 * Method depends on which congestion control state we're
119 * in (slow start or cong avoid) and if ABC (RFC 3465) is
120 * enabled.
121 *
122 * slow start: cwnd <= ssthresh
123 * cong avoid: cwnd > ssthresh
124 *
125 * slow start and ABC (RFC 3465):
126 * Grow cwnd exponentially by the amount of data
127 * ACKed capping the max increment per ACK to
128 * (abc_l_var * maxseg) bytes.
129 *
130 * slow start without ABC (RFC 5681):
131 * Grow cwnd exponentially by maxseg per ACK.
132 *
133 * cong avoid and ABC (RFC 3465):
134 * Grow cwnd linearly by maxseg per RTT for each
135 * cwnd worth of ACKed data.
136 *
137 * cong avoid without ABC (RFC 5681):
138 * Grow cwnd linearly by approximately maxseg per RTT using
139 * maxseg^2 / cwnd per ACK as the increment.
140 * If cwnd > maxseg^2, fix the cwnd increment at 1 byte to
141 * avoid capping cwnd.
142 */
143 if (cw > CCV(ccv, tcp_cwnd_ssthresh)) {
144 if (CC_ABC(ccv)) {
145 if (ccv->flags & CCF_ABC_SENTAWND)
146 ccv->flags &= ~CCF_ABC_SENTAWND;
147 else
148 incr = 0;
149 } else
150 incr = max((incr * incr / cw), 1);
151 } else if (CC_ABC(ccv)) {
152 /*
153 * In slow-start with ABC enabled and no RTO in sight?
154 * (Must not use abc_l_var > 1 if slow starting after
155 * an RTO.
156 */
157 if (ccv->flags & CCF_RTO) {
158 incr = min(ccv->bytes_this_ack,
159 CCV(ccv, tcp_mss));
160 } else {
161 incr = min(ccv->bytes_this_ack,
162 CC_ABC_L_VAR(ccv) * CCV(ccv, tcp_mss));
163 }
164
165 }
166 /* ABC is on by default, so incr equals 0 frequently. */
167 if (incr > 0)
168 CCV(ccv, tcp_cwnd) = min(cw + incr,
169 TCP_MAXWIN << CCV(ccv, tcp_snd_ws));
170 }
171 }
172
173 static void
newreno_after_idle(struct cc_var * ccv)174 newreno_after_idle(struct cc_var *ccv)
175 {
176 int rw;
177
178 /*
179 * If we've been idle for more than one retransmit timeout the old
180 * congestion window is no longer current and we have to reduce it to
181 * the restart window before we can transmit again.
182 *
183 * The restart window is the initial window or the last CWND, whichever
184 * is smaller.
185 *
186 * This is done to prevent us from flooding the path with a full CWND at
187 * wirespeed, overloading router and switch buffers along the way.
188 *
189 * See RFC5681 Section 4.1. "Restarting Idle Connections".
190 */
191 if (CCV(ccv, tcp_init_cwnd) != 0) {
192 /*
193 * The TCP_INIT_CWND socket option was used to override the
194 * default.
195 */
196 rw = CCV(ccv, tcp_init_cwnd) * CCV(ccv, tcp_mss);
197 } else if (CCSV(ccv, tcps_slow_start_initial) != 0) {
198 /* The _slow_start_initial tunable was explicitly set. */
199 rw = min(TCP_MAX_INIT_CWND, CCSV(ccv, tcps_slow_start_initial))
200 * CCV(ccv, tcp_mss);
201 } else {
202 /* Do RFC 3390 */
203 rw = min(4 * CCV(ccv, tcp_mss),
204 max(2 * CCV(ccv, tcp_mss), 4380));
205 }
206
207 CCV(ccv, tcp_cwnd) = min(rw, CCV(ccv, tcp_cwnd));
208 }
209
210 /*
211 * Perform any necessary tasks before we enter congestion recovery.
212 */
213 static void
newreno_cong_signal(struct cc_var * ccv,uint32_t type)214 newreno_cong_signal(struct cc_var *ccv, uint32_t type)
215 {
216 uint32_t cwin, ssthresh_on_loss;
217 uint32_t mss;
218
219 cwin = CCV(ccv, tcp_cwnd);
220 mss = CCV(ccv, tcp_mss);
221 ssthresh_on_loss =
222 max((CCV(ccv, tcp_snxt) - CCV(ccv, tcp_suna)) / 2 / mss, 2)
223 * mss;
224
225 /* Catch algos which mistakenly leak private signal types. */
226 ASSERT((type & CC_SIGPRIVMASK) == 0);
227
228 cwin = max(cwin / 2 / mss, 2) * mss;
229
230 switch (type) {
231 case CC_NDUPACK:
232 if (!IN_FASTRECOVERY(ccv->flags)) {
233 if (!IN_CONGRECOVERY(ccv->flags)) {
234 CCV(ccv, tcp_cwnd_ssthresh) = ssthresh_on_loss;
235 CCV(ccv, tcp_cwnd) = cwin;
236 }
237 ENTER_RECOVERY(ccv->flags);
238 }
239 break;
240 case CC_ECN:
241 if (!IN_CONGRECOVERY(ccv->flags)) {
242 CCV(ccv, tcp_cwnd_ssthresh) = ssthresh_on_loss;
243 CCV(ccv, tcp_cwnd) = cwin;
244 ENTER_CONGRECOVERY(ccv->flags);
245 }
246 break;
247 case CC_RTO:
248 CCV(ccv, tcp_cwnd_ssthresh) = ssthresh_on_loss;
249 CCV(ccv, tcp_cwnd) = mss;
250 break;
251 }
252 }
253
254 /*
255 * Perform any necessary tasks before we exit congestion recovery.
256 */
257 static void
newreno_post_recovery(struct cc_var * ccv)258 newreno_post_recovery(struct cc_var *ccv)
259 {
260 uint32_t pipe;
261
262 if (IN_FASTRECOVERY(ccv->flags)) {
263 /*
264 * Fast recovery will conclude after returning from this
265 * function. Window inflation should have left us with
266 * approximately cwnd_ssthresh outstanding data. But in case we
267 * would be inclined to send a burst, better to do it via the
268 * slow start mechanism.
269 */
270 pipe = CCV(ccv, tcp_snxt) - CCV(ccv, tcp_suna);
271 if (pipe < CCV(ccv, tcp_cwnd_ssthresh)) {
272 /*
273 * Ensure that cwnd does not collapse to 1 MSS under
274 * adverse conditions. Implements RFC6582
275 */
276 CCV(ccv, tcp_cwnd) = MAX(pipe, CCV(ccv, tcp_mss)) +
277 CCV(ccv, tcp_mss);
278 } else if (CCV(ccv, tcp_cwnd) > CCV(ccv, tcp_cwnd_ssthresh)) {
279 CCV(ccv, tcp_cwnd) = CCV(ccv, tcp_cwnd_ssthresh);
280 }
281 }
282 }
283