/* * Copyright (c) 2010-2012 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. 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All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.16 2001/08/22 00:59:12 silby Exp $ */ #include <sys/param.h> #include <sys/systm.h> #include <sys/kernel.h> #include <sys/protosw.h> #include <sys/socketvar.h> #include <net/route.h> #include <netinet/in.h> #include <netinet/in_systm.h> #include <netinet/ip.h> #if INET6 #include <netinet/ip6.h> #endif #include <netinet/ip_var.h> #include <netinet/tcp.h> #include <netinet/tcp_fsm.h> #include <netinet/tcp_timer.h> #include <netinet/tcp_var.h> #include <netinet/tcpip.h> #include <netinet/tcp_cc.h> #include <libkern/OSAtomic.h> 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); 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; extern u_int32_t tcp_autosndbuf_max; #define SET_SNDSB_IDEAL_SIZE(sndsb, size) \ sndsb->sb_idealsize = min(max(tcp_sendspace, tp->snd_ssthresh), \ tcp_autosndbuf_max); void tcp_cc_resize_sndbuf(struct tcpcb *tp) { struct sockbuf *sb; /* If the send socket buffer size is bigger than ssthresh, * it is time to trim it because we do not want to hold * too many mbufs in the socket buffer */ sb = &(tp->t_inpcb->inp_socket->so_snd); if (sb->sb_hiwat > tp->snd_ssthresh && (sb->sb_flags & SB_AUTOSIZE) != 0) { if (sb->sb_idealsize > tp->snd_ssthresh) { SET_SNDSB_IDEAL_SIZE(sb, tp->snd_ssthresh); } sb->sb_flags |= SB_TRIM; } } void tcp_bad_rexmt_fix_sndbuf(struct tcpcb *tp) { struct sockbuf *sb; sb = &(tp->t_inpcb->inp_socket->so_snd); if ((sb->sb_flags & (SB_TRIM|SB_AUTOSIZE)) == (SB_TRIM|SB_AUTOSIZE)) { /* If there was a retransmission that was not necessary * then the size of socket buffer can be restored to * what it was before */ SET_SNDSB_IDEAL_SIZE(sb, tp->snd_ssthresh); if (sb->sb_hiwat <= sb->sb_idealsize) { sbreserve(sb, sb->sb_idealsize); sb->sb_flags &= ~SB_TRIM; } } } 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<<tp->snd_scale); } void tcp_newreno_pre_fr(struct tcpcb *tp) { 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; tcp_cc_resize_sndbuf(tp); } 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; tcp_cc_resize_sndbuf(tp); } } /* * 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_unacksegs == 1)) return(1); break; case 3: if ((tp->t_flags & TF_RXWIN0SENT) == 0 && (th->th_flags & TH_PUSH) == 0 && ((tp->t_unacksegs == 1) || ((tp->t_flags & TF_STRETCHACK) != 0 && tp->t_unacksegs < (maxseg_unacked)))) 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); }