X-Git-Url: https://git.saurik.com/apple/xnu.git/blobdiff_plain/060df5ea7c632b1ac8cc8aac1fb59758165c2084..6d2010ae8f7a6078e10b361c6962983bab233e0f:/bsd/netinet/tcp_newreno.c?ds=sidebyside diff --git a/bsd/netinet/tcp_newreno.c b/bsd/netinet/tcp_newreno.c new file mode 100644 index 000000000..5c9db2de9 --- /dev/null +++ b/bsd/netinet/tcp_newreno.c @@ -0,0 +1,344 @@ +/* + * Copyright (c) 2010 Apple Inc. All rights reserved. + * + * @APPLE_OSREFERENCE_LICENSE_HEADER_START@ + * + * This file contains Original Code and/or Modifications of Original Code + * as defined in and that are subject to the Apple Public Source License + * Version 2.0 (the 'License'). You may not use this file except in + * compliance with the License. The rights granted to you under the License + * may not be used to create, or enable the creation or redistribution of, + * unlawful or unlicensed copies of an Apple operating system, or to + * circumvent, violate, or enable the circumvention or violation of, any + * terms of an Apple operating system software license agreement. + * + * Please obtain a copy of the License at + * http://www.opensource.apple.com/apsl/ and read it before using this file. + * + * The Original Code and all software distributed under the License are + * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER + * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, + * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. + * Please see the License for the specific language governing rights and + * limitations under the License. + * + * @APPLE_OSREFERENCE_LICENSE_HEADER_END@ + */ +#include +#include +#include +#include + +#include +#include +#include +#include + +#if INET6 +#include +#endif +#include +#include +#include +#include +#include +#include +#include +#include + +int tcp_newreno_init(struct tcpcb *tp); +int tcp_newreno_cleanup(struct tcpcb *tp); +void tcp_newreno_cwnd_init_or_reset(struct tcpcb *tp); +void tcp_newreno_inseq_ack_rcvd(struct tcpcb *tp, struct tcphdr *th); +void tcp_newreno_ack_rcvd(struct tcpcb *tp, struct tcphdr *th); +void tcp_newreno_pre_fr(struct tcpcb *tp, struct tcphdr *th); +void tcp_newreno_post_fr(struct tcpcb *tp, struct tcphdr *th); +void tcp_newreno_after_idle(struct tcpcb *tp); +void tcp_newreno_after_timeout(struct tcpcb *tp); +int tcp_newreno_delay_ack(struct tcpcb *tp, struct tcphdr *th); +void tcp_newreno_switch_cc(struct tcpcb *tp, uint16_t old_index); + +struct tcp_cc_algo tcp_cc_newreno = { + .name = "newreno", + .init = tcp_newreno_init, + .cleanup = tcp_newreno_cleanup, + .cwnd_init = tcp_newreno_cwnd_init_or_reset, + .inseq_ack_rcvd = tcp_newreno_inseq_ack_rcvd, + .ack_rcvd = tcp_newreno_ack_rcvd, + .pre_fr = tcp_newreno_pre_fr, + .post_fr = tcp_newreno_post_fr, + .after_idle = tcp_newreno_cwnd_init_or_reset, + .after_timeout = tcp_newreno_after_timeout, + .delay_ack = tcp_newreno_delay_ack, + .switch_to = tcp_newreno_switch_cc +}; + +extern int tcp_do_rfc3465; +extern int tcp_do_rfc3465_lim2; +extern int maxseg_unacked; + +int tcp_newreno_init(struct tcpcb *tp) { +#pragma unused(tp) + OSIncrementAtomic((volatile SInt32 *)&tcp_cc_newreno.num_sockets); + return 0; +} + +int tcp_newreno_cleanup(struct tcpcb *tp) { +#pragma unused(tp) + OSDecrementAtomic((volatile SInt32 *)&tcp_cc_newreno.num_sockets); + return 0; +} + +/* Initialize the congestion window for a connection or + * handles connections that have been idle for + * some time. In this state, no acks are + * expected to clock out any data we send -- + * slow start to get ack "clock" running again. + * + * Set the slow-start flight size depending on whether + * this is a local network or not. + */ +void +tcp_newreno_cwnd_init_or_reset(struct tcpcb *tp) { + if ( tp->t_flags & TF_LOCAL ) + tp->snd_cwnd = tp->t_maxseg * ss_fltsz_local; + else { + /* Calculate initial cwnd according to RFC3390, + * - On a standard link, this will result in a higher cwnd + * and improve initial transfer rate. + * - Keep the old ss_fltsz sysctl for ABI compabitility issues. + * but it will be overriden if tcp_do_rfc3390 sysctl is set. + */ + + if (tcp_do_rfc3390) + tp->snd_cwnd = min(4 * tp->t_maxseg, max(2 * tp->t_maxseg, 4380)); + + else + tp->snd_cwnd = tp->t_maxseg * ss_fltsz; + } +} + + +/* Function to handle an in-sequence ack during congestion avoidance phase. + * This will get called from header prediction code. + */ +void +tcp_newreno_inseq_ack_rcvd(struct tcpcb *tp, struct tcphdr *th) { + int acked = 0; + acked = th->th_ack - tp->snd_una; + /* + * Grow the congestion window, if the + * connection is cwnd bound. + */ + if (tp->snd_cwnd < tp->snd_wnd) { + tp->t_bytes_acked += acked; + if (tp->t_bytes_acked > tp->snd_cwnd) { + tp->t_bytes_acked -= tp->snd_cwnd; + tp->snd_cwnd += tp->t_maxseg; + } + } +} +/* Function to process an ack. + */ +void +tcp_newreno_ack_rcvd(struct tcpcb *tp, struct tcphdr *th) { + /* + * RFC 3465 - Appropriate Byte Counting. + * + * If the window is currently less than ssthresh, + * open the window by the number of bytes ACKed by + * the last ACK, however clamp the window increase + * to an upper limit "L". + * + * In congestion avoidance phase, open the window by + * one segment each time "bytes_acked" grows to be + * greater than or equal to the congestion window. + */ + + register u_int cw = tp->snd_cwnd; + register u_int incr = tp->t_maxseg; + int acked = 0; + + acked = th->th_ack - tp->snd_una; + if (tcp_do_rfc3465) { + + if (cw >= tp->snd_ssthresh) { + tp->t_bytes_acked += acked; + if (tp->t_bytes_acked >= cw) { + /* Time to increase the window. */ + tp->t_bytes_acked -= cw; + } else { + /* No need to increase yet. */ + incr = 0; + } + } else { + /* + * If the user explicitly enables RFC3465 + * use 2*SMSS for the "L" param. Otherwise + * use the more conservative 1*SMSS. + * + * (See RFC 3465 2.3 Choosing the Limit) + */ + u_int abc_lim; + + abc_lim = (tcp_do_rfc3465_lim2 && + tp->snd_nxt == tp->snd_max) ? incr * 2 : incr; + + incr = lmin(acked, abc_lim); + } + } else { + /* + * If the window gives us less than ssthresh packets + * in flight, open exponentially (segsz per packet). + * Otherwise open linearly: segsz per window + * (segsz^2 / cwnd per packet). + */ + + if (cw >= tp->snd_ssthresh) + incr = max((incr * incr / cw), 1); + } + tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<snd_scale); +} + +void +tcp_newreno_pre_fr(struct tcpcb *tp, struct tcphdr *th) { +#pragma unused(th) + + uint32_t win; + + win = min(tp->snd_wnd, tp->snd_cwnd) / + 2 / tp->t_maxseg; + if ( win < 2 ) + win = 2; + tp->snd_ssthresh = win * tp->t_maxseg; +} + +void +tcp_newreno_post_fr(struct tcpcb *tp, struct tcphdr *th) { + int32_t ss; + + ss = tp->snd_max - th->th_ack; + + /* + * Complete ack. Inflate the congestion window to + * ssthresh and exit fast recovery. + * + * Window inflation should have left us with approx. + * snd_ssthresh outstanding data. But in case we + * would be inclined to send a burst, better to do + * it via the slow start mechanism. + */ + if (ss < (int32_t)tp->snd_ssthresh) + tp->snd_cwnd = ss + tp->t_maxseg; + else + tp->snd_cwnd = tp->snd_ssthresh; + tp->t_bytes_acked = 0; +} + +/* Function to change the congestion window when the retransmit + * timer fires. + */ +void +tcp_newreno_after_timeout(struct tcpcb *tp) { + /* + * Close the congestion window down to one segment + * (we'll open it by one segment for each ack we get). + * Since we probably have a window's worth of unacked + * data accumulated, this "slow start" keeps us from + * dumping all that data as back-to-back packets (which + * might overwhelm an intermediate gateway). + * + * There are two phases to the opening: Initially we + * open by one mss on each ack. This makes the window + * size increase exponentially with time. If the + * window is larger than the path can handle, this + * exponential growth results in dropped packet(s) + * almost immediately. To get more time between + * drops but still "push" the network to take advantage + * of improving conditions, we switch from exponential + * to linear window opening at some threshhold size. + * For a threshhold, we use half the current window + * size, truncated to a multiple of the mss. + * + * (the minimum cwnd that will give us exponential + * growth is 2 mss. We don't allow the threshhold + * to go below this.) + */ + if (tp->t_state >= TCPS_ESTABLISHED) { + u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; + if (win < 2) + win = 2; + tp->snd_cwnd = tp->t_maxseg; + tp->snd_ssthresh = win * tp->t_maxseg; + tp->t_bytes_acked = 0; + tp->t_dupacks = 0; + } +} + +/* + * Indicate whether this ack should be delayed. + * We can delay the ack if: + * - delayed acks are enabled and set to 1, same as when value is set to 2. + * We kept this for binary compatibility. + * - delayed acks are enabled and set to 2, will "ack every other packet" + * - if our last ack wasn't a 0-sized window. + * - if the peer hasn't sent us a TH_PUSH data packet (this solves 3649245). + * If TH_PUSH is set, take this as a clue that we need to ACK + * with no delay. This helps higher level protocols who won't send + * us more data even if the window is open because their + * last "segment" hasn't been ACKed + * - delayed acks are enabled and set to 3, will do "streaming detection" + * (see the comment in tcp_input.c) and + * - if we receive more than "maxseg_unacked" full packets in the last 100ms + * - if the connection is not in slow-start or idle or loss/recovery states + * - if those criteria aren't met, it will ack every other packet. + */ + +int +tcp_newreno_delay_ack(struct tcpcb *tp, struct tcphdr *th) { + switch (tcp_delack_enabled) { + case 1: + case 2: + if ((tp->t_flags & TF_RXWIN0SENT) == 0 && + (th->th_flags & TH_PUSH) == 0 && + (tp->t_flags & TF_DELACK) == 0) + return(1); + break; + case 3: + if ((tp->t_flags & TF_RXWIN0SENT) == 0 && + (th->th_flags & TH_PUSH) == 0 && + ((tp->t_unacksegs == 0) || + ((tp->t_flags & TF_STRETCHACK) != 0 && + tp->t_unacksegs < (maxseg_unacked - 1)))) + return(1); + break; + } + return(0); +} + +/* Switch to newreno from a different CC. If the connection is in + * congestion avoidance state, it can continue to use the current + * congestion window because it is going to be conservative. But + * if the connection is in slow-start, we will halve the congestion + * window and let newreno work from there. + */ +void +tcp_newreno_switch_cc(struct tcpcb *tp, uint16_t old_index) { +#pragma unused(old_index) + + uint32_t cwnd = min(tp->snd_wnd, tp->snd_cwnd); + if (tp->snd_cwnd >= tp->snd_ssthresh) { + cwnd = cwnd / tp->t_maxseg; + } else { + cwnd = cwnd / 2 / tp->t_maxseg; + } + if (cwnd < 1) + cwnd = 1; + tp->snd_cwnd = cwnd * tp->t_maxseg; + + /* Start counting bytes for RFC 3465 again */ + tp->t_bytes_acked = 0; + + OSIncrementAtomic((volatile SInt32 *)&tcp_cc_newreno.num_sockets); +}