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 * 10 * This software was developed at the Centre for Advanced Internet 11 * Architectures, Swinburne University of Technology, by Lawrence Stewart, James 12 * Healy and David Hayes, made possible in part by a grant from the Cisco 13 * University Research Program Fund at Community Foundation Silicon Valley. 14 * 15 * Portions of this software were developed at the Centre for Advanced 16 * Internet Architectures, Swinburne University of Technology, Melbourne, 17 * Australia by 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 * This software was first released in 2007 by James Healy and Lawrence Stewart 43 * whilst working on the NewTCP research project at Swinburne University of 44 * Technology's Centre for Advanced Internet Architectures, Melbourne, 45 * Australia, which was made possible in part by a grant from the Cisco 46 * University Research Program Fund at Community Foundation Silicon Valley. 47 * More details are available at: 48 * http://caia.swin.edu.au/urp/newtcp/ 49 */ 50 51#include <sys/cdefs.h> 52__FBSDID("$FreeBSD: stable/11/sys/netinet/cc/cc_newreno.c 347882 2019-05-16 18:29:25Z tuexen $"); 53 54#include <sys/param.h> 55#include <sys/kernel.h> 56#include <sys/malloc.h> 57#include <sys/module.h> 58#include <sys/socket.h> 59#include <sys/socketvar.h> 60#include <sys/sysctl.h> 61#include <sys/systm.h> 62 63#include <net/vnet.h> 64 65#include <netinet/tcp.h> 66#include <netinet/tcp_seq.h> 67#include <netinet/tcp_var.h> 68#include <netinet/cc/cc.h> 69#include <netinet/cc/cc_module.h> 70 71static void newreno_ack_received(struct cc_var *ccv, uint16_t type); 72static void newreno_after_idle(struct cc_var *ccv); 73static void newreno_cong_signal(struct cc_var *ccv, uint32_t type); 74static void newreno_post_recovery(struct cc_var *ccv); 75 76struct cc_algo newreno_cc_algo = { 77 .name = "newreno", 78 .ack_received = newreno_ack_received, 79 .after_idle = newreno_after_idle, 80 .cong_signal = newreno_cong_signal, 81 .post_recovery = newreno_post_recovery, 82}; 83 84static void 85newreno_ack_received(struct cc_var *ccv, uint16_t type) 86{ 87 if (type == CC_ACK && !IN_RECOVERY(CCV(ccv, t_flags)) && 88 (ccv->flags & CCF_CWND_LIMITED)) { 89 u_int cw = CCV(ccv, snd_cwnd); 90 u_int incr = CCV(ccv, t_maxseg); 91 92 /* 93 * Regular in-order ACK, open the congestion window. 94 * Method depends on which congestion control state we're 95 * in (slow start or cong avoid) and if ABC (RFC 3465) is 96 * enabled. 97 * 98 * slow start: cwnd <= ssthresh 99 * cong avoid: cwnd > ssthresh 100 * 101 * slow start and ABC (RFC 3465): 102 * Grow cwnd exponentially by the amount of data 103 * ACKed capping the max increment per ACK to 104 * (abc_l_var * maxseg) bytes. 105 * 106 * slow start without ABC (RFC 5681): 107 * Grow cwnd exponentially by maxseg per ACK. 108 * 109 * cong avoid and ABC (RFC 3465): 110 * Grow cwnd linearly by maxseg per RTT for each 111 * cwnd worth of ACKed data. 112 * 113 * cong avoid without ABC (RFC 5681): 114 * Grow cwnd linearly by approximately maxseg per RTT using 115 * maxseg^2 / cwnd per ACK as the increment. 116 * If cwnd > maxseg^2, fix the cwnd increment at 1 byte to 117 * avoid capping cwnd. 118 */ 119 if (cw > CCV(ccv, snd_ssthresh)) { 120 if (V_tcp_do_rfc3465) { 121 if (ccv->flags & CCF_ABC_SENTAWND) 122 ccv->flags &= ~CCF_ABC_SENTAWND; 123 else 124 incr = 0; 125 } else 126 incr = max((incr * incr / cw), 1); 127 } else if (V_tcp_do_rfc3465) { 128 /* 129 * In slow-start with ABC enabled and no RTO in sight? 130 * (Must not use abc_l_var > 1 if slow starting after 131 * an RTO. On RTO, snd_nxt = snd_una, so the 132 * snd_nxt == snd_max check is sufficient to 133 * handle this). 134 * 135 * XXXLAS: Find a way to signal SS after RTO that 136 * doesn't rely on tcpcb vars. 137 */ 138 if (CCV(ccv, snd_nxt) == CCV(ccv, snd_max)) 139 incr = min(ccv->bytes_this_ack, 140 V_tcp_abc_l_var * CCV(ccv, t_maxseg)); 141 else 142 incr = min(ccv->bytes_this_ack, CCV(ccv, t_maxseg)); 143 } 144 /* ABC is on by default, so incr equals 0 frequently. */ 145 if (incr > 0) 146 CCV(ccv, snd_cwnd) = min(cw + incr, 147 TCP_MAXWIN << CCV(ccv, snd_scale)); 148 } 149} 150 151static void 152newreno_after_idle(struct cc_var *ccv) 153{ 154 int rw; 155 156 /* 157 * If we've been idle for more than one retransmit timeout the old 158 * congestion window is no longer current and we have to reduce it to 159 * the restart window before we can transmit again. 160 * 161 * The restart window is the initial window or the last CWND, whichever 162 * is smaller. 163 * 164 * This is done to prevent us from flooding the path with a full CWND at 165 * wirespeed, overloading router and switch buffers along the way. 166 * 167 * See RFC5681 Section 4.1. "Restarting Idle Connections". 168 */ 169 if (V_tcp_do_rfc3390) 170 rw = min(4 * CCV(ccv, t_maxseg), 171 max(2 * CCV(ccv, t_maxseg), 4380)); 172 else 173 rw = CCV(ccv, t_maxseg) * 2; 174 175 CCV(ccv, snd_cwnd) = min(rw, CCV(ccv, snd_cwnd)); 176} 177 178/* 179 * Perform any necessary tasks before we enter congestion recovery. 180 */ 181static void 182newreno_cong_signal(struct cc_var *ccv, uint32_t type) 183{ 184 u_int win; 185 186 /* Catch algos which mistakenly leak private signal types. */ 187 KASSERT((type & CC_SIGPRIVMASK) == 0, 188 ("%s: congestion signal type 0x%08x is private\n", __func__, type)); 189 190 win = max(CCV(ccv, snd_cwnd) / 2 / CCV(ccv, t_maxseg), 2) * 191 CCV(ccv, t_maxseg); 192 193 switch (type) { 194 case CC_NDUPACK: 195 if (!IN_FASTRECOVERY(CCV(ccv, t_flags))) { 196 if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) 197 CCV(ccv, snd_ssthresh) = win; 198 ENTER_RECOVERY(CCV(ccv, t_flags)); 199 } 200 break; 201 case CC_ECN: 202 if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) { 203 CCV(ccv, snd_ssthresh) = win; 204 CCV(ccv, snd_cwnd) = win; 205 ENTER_CONGRECOVERY(CCV(ccv, t_flags)); 206 } 207 break; 208 } 209} 210 211/* 212 * Perform any necessary tasks before we exit congestion recovery. 213 */ 214static void 215newreno_post_recovery(struct cc_var *ccv) 216{ 217 int pipe; 218 pipe = 0; 219 220 if (IN_FASTRECOVERY(CCV(ccv, t_flags))) { 221 /* 222 * Fast recovery will conclude after returning from this 223 * function. Window inflation should have left us with 224 * approximately snd_ssthresh outstanding data. But in case we 225 * would be inclined to send a burst, better to do it via the 226 * slow start mechanism. 227 * 228 * XXXLAS: Find a way to do this without needing curack 229 */ 230 if (V_tcp_do_rfc6675_pipe) 231 pipe = tcp_compute_pipe(ccv->ccvc.tcp); 232 else 233 pipe = CCV(ccv, snd_max) - ccv->curack; 234 235 if (pipe < CCV(ccv, snd_ssthresh)) 236 /* 237 * Ensure that cwnd does not collapse to 1 MSS under 238 * adverse conditons. Implements RFC6582 239 */ 240 CCV(ccv, snd_cwnd) = max(pipe, CCV(ccv, t_maxseg)) + 241 CCV(ccv, t_maxseg); 242 else 243 CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh); 244 } 245} 246 247 248DECLARE_CC_MODULE(newreno, &newreno_cc_algo); 249