1/*
2 * Copyright (c) 2010-2014 Apple Inc. All rights reserved.
3 *
4 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
5 *
6 * This file contains Original Code and/or Modifications of Original Code
7 * as defined in and that are subject to the Apple Public Source License
8 * Version 2.0 (the 'License'). You may not use this file except in
9 * compliance with the License. The rights granted to you under the License
10 * may not be used to create, or enable the creation or redistribution of,
11 * unlawful or unlicensed copies of an Apple operating system, or to
12 * circumvent, violate, or enable the circumvention or violation of, any
13 * terms of an Apple operating system software license agreement.
14 *
15 * Please obtain a copy of the License at
16 * http://www.opensource.apple.com/apsl/ and read it before using this file.
17 *
18 * The Original Code and all software distributed under the License are
19 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
20 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
21 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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23 * Please see the License for the specific language governing rights and
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25 *
26 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
27 */
28/*
29 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
30 * The Regents of the University of California. All rights reserved.
31 *
32 * Redistribution and use in source and binary forms, with or without
33 * modification, are permitted provided that the following conditions
34 * are met:
35 * 1. Redistributions of source code must retain the above copyright
36 * notice, this list of conditions and the following disclaimer.
37 * 2. Redistributions in binary form must reproduce the above copyright
38 * notice, this list of conditions and the following disclaimer in the
39 * documentation and/or other materials provided with the distribution.
40 * 3. All advertising materials mentioning features or use of this software
41 * must display the following acknowledgement:
42 * This product includes software developed by the University of
43 * California, Berkeley and its contributors.
44 * 4. Neither the name of the University nor the names of its contributors
45 * may be used to endorse or promote products derived from this software
46 * without specific prior written permission.
47 *
48 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
49 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
50 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
51 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
52 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
53 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
54 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
55 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
56 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
57 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
58 * SUCH DAMAGE.
59 *
60 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
61 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.16 2001/08/22 00:59:12 silby Exp $
62 */
63#include <sys/param.h>
64#include <sys/systm.h>
65#include <sys/kernel.h>
66#include <sys/protosw.h>
67#include <sys/socketvar.h>
68
69#include <net/route.h>
70#include <netinet/in.h>
71#include <netinet/in_systm.h>
72#include <netinet/ip.h>
73
74#if INET6
75#include <netinet/ip6.h>
76#endif
77#include <netinet/ip_var.h>
78#include <netinet/tcp.h>
79#include <netinet/tcp_fsm.h>
80#include <netinet/tcp_timer.h>
81#include <netinet/tcp_var.h>
82#include <netinet/tcpip.h>
83#include <netinet/tcp_cc.h>
84#include <libkern/OSAtomic.h>
85
86int tcp_newreno_init(struct tcpcb *tp);
87int tcp_newreno_cleanup(struct tcpcb *tp);
88void tcp_newreno_cwnd_init_or_reset(struct tcpcb *tp);
89void tcp_newreno_congestion_avd(struct tcpcb *tp, struct tcphdr *th);
90void tcp_newreno_ack_rcvd(struct tcpcb *tp, struct tcphdr *th);
91void tcp_newreno_pre_fr(struct tcpcb *tp);
92void tcp_newreno_post_fr(struct tcpcb *tp, struct tcphdr *th);
93void tcp_newreno_after_idle(struct tcpcb *tp);
94void tcp_newreno_after_timeout(struct tcpcb *tp);
95int tcp_newreno_delay_ack(struct tcpcb *tp, struct tcphdr *th);
96void tcp_newreno_switch_cc(struct tcpcb *tp, uint16_t old_index);
97
98struct tcp_cc_algo tcp_cc_newreno = {
99 .name = "newreno",
100 .init = tcp_newreno_init,
101 .cleanup = tcp_newreno_cleanup,
102 .cwnd_init = tcp_newreno_cwnd_init_or_reset,
103 .congestion_avd = tcp_newreno_congestion_avd,
104 .ack_rcvd = tcp_newreno_ack_rcvd,
105 .pre_fr = tcp_newreno_pre_fr,
106 .post_fr = tcp_newreno_post_fr,
107 .after_idle = tcp_newreno_cwnd_init_or_reset,
108 .after_timeout = tcp_newreno_after_timeout,
109 .delay_ack = tcp_newreno_delay_ack,
110 .switch_to = tcp_newreno_switch_cc
111};
112
113int tcp_newreno_init(struct tcpcb *tp) {
114#pragma unused(tp)
115 OSIncrementAtomic((volatile SInt32 *)&tcp_cc_newreno.num_sockets);
116 return 0;
117}
118
119int tcp_newreno_cleanup(struct tcpcb *tp) {
120#pragma unused(tp)
121 OSDecrementAtomic((volatile SInt32 *)&tcp_cc_newreno.num_sockets);
122 return 0;
123}
124
125/* Initialize the congestion window for a connection or
126 * handles connections that have been idle for
127 * some time. In this state, no acks are
128 * expected to clock out any data we send --
129 * slow start to get ack "clock" running again.
130 *
131 * Set the slow-start flight size depending on whether
132 * this is a local network or not.
133 */
134void
135tcp_newreno_cwnd_init_or_reset(struct tcpcb *tp) {
136 tcp_cc_cwnd_init_or_reset(tp);
137}
138
139
140/* Function to handle an in-sequence ack during congestion avoidance phase.
141 * This will get called from header prediction code.
142 */
143void
144tcp_newreno_congestion_avd(struct tcpcb *tp, struct tcphdr *th) {
145 uint32_t acked = 0;
146 acked = BYTES_ACKED(th, tp);
147 /*
148 * Grow the congestion window, if the
149 * connection is cwnd bound.
150 */
151 if (tp->snd_cwnd < tp->snd_wnd) {
152 tp->t_bytes_acked += acked;
153 if (tp->t_bytes_acked > tp->snd_cwnd) {
154 tp->t_bytes_acked -= tp->snd_cwnd;
155 tp->snd_cwnd += tp->t_maxseg;
156 }
157 }
158}
159/* Function to process an ack.
160 */
161void
162tcp_newreno_ack_rcvd(struct tcpcb *tp, struct tcphdr *th) {
163 /*
164 * RFC 3465 - Appropriate Byte Counting.
165 *
166 * If the window is currently less than ssthresh,
167 * open the window by the number of bytes ACKed by
168 * the last ACK, however clamp the window increase
169 * to an upper limit "L".
170 *
171 * In congestion avoidance phase, open the window by
172 * one segment each time "bytes_acked" grows to be
173 * greater than or equal to the congestion window.
174 */
175
176 u_int cw = tp->snd_cwnd;
177 u_int incr = tp->t_maxseg;
178 int acked = 0;
179
180 acked = BYTES_ACKED(th, tp);
181 if (tcp_do_rfc3465) {
182
183 if (cw >= tp->snd_ssthresh) {
184 tp->t_bytes_acked += acked;
185 if (tp->t_bytes_acked >= cw) {
186 /* Time to increase the window. */
187 tp->t_bytes_acked -= cw;
188 } else {
189 /* No need to increase yet. */
190 incr = 0;
191 }
192 } else {
193 /*
194 * If the user explicitly enables RFC3465
195 * use 2*SMSS for the "L" param. Otherwise
196 * use the more conservative 1*SMSS.
197 *
198 * (See RFC 3465 2.3 Choosing the Limit)
199 */
200 uint32_t abc_lim;
201 abc_lim = (tcp_do_rfc3465_lim2 &&
202 tp->snd_nxt == tp->snd_max) ? incr * 2
203 : incr;
204
205 incr = lmin(acked, abc_lim);
206 }
207 } else {
208 /*
209 * If the window gives us less than ssthresh packets
210 * in flight, open exponentially (segsz per packet).
211 * Otherwise open linearly: segsz per window
212 * (segsz^2 / cwnd per packet).
213 */
214
215 if (cw >= tp->snd_ssthresh)
216 incr = max((incr * incr / cw), 1);
217 }
218 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale);
219}
220
221void
222tcp_newreno_pre_fr(struct tcpcb *tp) {
223
224 uint32_t win;
225
226 win = min(tp->snd_wnd, tp->snd_cwnd) /
227 2 / tp->t_maxseg;
228 if ( win < 2 )
229 win = 2;
230 tp->snd_ssthresh = win * tp->t_maxseg;
231 tcp_cc_resize_sndbuf(tp);
232
233}
234
235void
236tcp_newreno_post_fr(struct tcpcb *tp, struct tcphdr *th) {
237 int32_t ss;
238
239 ss = tp->snd_max - th->th_ack;
240
241 /*
242 * Complete ack. Inflate the congestion window to
243 * ssthresh and exit fast recovery.
244 *
245 * Window inflation should have left us with approx.
246 * snd_ssthresh outstanding data. But in case we
247 * would be inclined to send a burst, better to do
248 * it via the slow start mechanism.
249 *
250 * If the flight size is zero, then make congestion
251 * window to be worth at least 2 segments to avoid
252 * delayed acknowledgement (draft-ietf-tcpm-rfc3782-bis-05).
253 */
254 if (ss < (int32_t)tp->snd_ssthresh)
255 tp->snd_cwnd = max(ss, tp->t_maxseg) + tp->t_maxseg;
256 else
257 tp->snd_cwnd = tp->snd_ssthresh;
258 tp->t_bytes_acked = 0;
259}
260
261/* Function to change the congestion window when the retransmit
262 * timer fires.
263 */
264void
265tcp_newreno_after_timeout(struct tcpcb *tp) {
266 /*
267 * Close the congestion window down to one segment
268 * (we'll open it by one segment for each ack we get).
269 * Since we probably have a window's worth of unacked
270 * data accumulated, this "slow start" keeps us from
271 * dumping all that data as back-to-back packets (which
272 * might overwhelm an intermediate gateway).
273 *
274 * There are two phases to the opening: Initially we
275 * open by one mss on each ack. This makes the window
276 * size increase exponentially with time. If the
277 * window is larger than the path can handle, this
278 * exponential growth results in dropped packet(s)
279 * almost immediately. To get more time between
280 * drops but still "push" the network to take advantage
281 * of improving conditions, we switch from exponential
282 * to linear window opening at some threshhold size.
283 * For a threshhold, we use half the current window
284 * size, truncated to a multiple of the mss.
285 *
286 * (the minimum cwnd that will give us exponential
287 * growth is 2 mss. We don't allow the threshhold
288 * to go below this.)
289 */
290 if (tp->t_state >= TCPS_ESTABLISHED) {
291 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
292 if (win < 2)
293 win = 2;
294 tp->snd_ssthresh = win * tp->t_maxseg;
295
296 tp->snd_cwnd = tp->t_maxseg;
297 tcp_cc_resize_sndbuf(tp);
298 }
299}
300
301/*
302 * Indicate whether this ack should be delayed.
303 * We can delay the ack if:
304 * - delayed acks are enabled and set to 1, same as when value is set to 2.
305 * We kept this for binary compatibility.
306 * - delayed acks are enabled and set to 2, will "ack every other packet"
307 * - if our last ack wasn't a 0-sized window.
308 * - if the peer hasn't sent us a TH_PUSH data packet (this solves 3649245).
309 * If TH_PUSH is set, take this as a clue that we need to ACK
310 * with no delay. This helps higher level protocols who won't send
311 * us more data even if the window is open because their
312 * last "segment" hasn't been ACKed
313 * - delayed acks are enabled and set to 3, will do "streaming detection"
314 * (see the comment in tcp_input.c) and
315 * - if we receive more than "maxseg_unacked" full packets in the last 100ms
316 * - if the connection is not in slow-start or idle or loss/recovery states
317 * - if those criteria aren't met, it will ack every other packet.
318 */
319
320int
321tcp_newreno_delay_ack(struct tcpcb *tp, struct tcphdr *th) {
322 return (tcp_cc_delay_ack(tp, th));
323}
324
325/* Switch to newreno from a different CC. If the connection is in
326 * congestion avoidance state, it can continue to use the current
327 * congestion window because it is going to be conservative. But
328 * if the connection is in slow-start, we will halve the congestion
329 * window and let newreno work from there.
330 */
331void
332tcp_newreno_switch_cc(struct tcpcb *tp, uint16_t old_index) {
333#pragma unused(old_index)
334
335 uint32_t cwnd = min(tp->snd_wnd, tp->snd_cwnd);
336 if (tp->snd_cwnd >= tp->snd_ssthresh) {
337 cwnd = cwnd / tp->t_maxseg;
338 } else {
339 cwnd = cwnd / 2 / tp->t_maxseg;
340 }
341 tp->snd_cwnd = max(TCP_CC_CWND_INIT_BYTES, cwnd * tp->t_maxseg);
342
343 /* Start counting bytes for RFC 3465 again */
344 tp->t_bytes_acked = 0;
345
346 OSIncrementAtomic((volatile SInt32 *)&tcp_cc_newreno.num_sockets);
347}
348